Gli autori desiderano ringraziare Picometrix per fornire il substrato LT-GaAs e con gratitudine riconoscere il sostegno finanziario da Michigan Spazio di Grant Consortium, DARPA Giovane Faculty Award gestito dal Dott. John Albrecht (contratto # N66001-10-1-4027), NSF CARRIERA Premio gestito dal Dott. Samir El-Ghazaly (contratto # N00014-11-1-0096), ONR Young Investigator Award gestito dal Dott. Paul Maki (contratto # N00014-12-1-0947), e ARO Young Investigator Award gestito da Il dottor Dev Palmer (contratto # W911NF-12-1-0253).

1. Plasmonica Fabrication emettitore Photoconductive <ol><li> Realizzare grate plasmonic. <ol><li> Pulire il wafer semiconduttore immergendolo in acetone (2 min) seguito da isopropanolo (2 min), e risciacquo con acqua deionizzata (10 sec). </li><li> Essiccare il campione in azoto e riscaldare su una piastra riscaldante a 115 ° C per 90 secondi per rimuovere l&#39;acqua residua. </li><li> Spin MicroChem 950K PMMA A4 sul campione a 4000 rpm per 45 sec. Pre-bake il resist su una piastra riscaldante a 180 ° C per 3 min. </li><li> Caricare il campione in uno strumento di litografia a fascio di elettroni (JEOL JBX-6300-FS). Esporre il pattern di rete plasmonica alla dose base di circa 650 uC / cm 2, con una tensione di 100 kV di accelerazione. </li><li> Sviluppare PMMA immergendo il campione in un MIBK: IPA miscela 1:03 per 90 sec. Trasferire immediatamente il campione ad una soluzione di isopropanolo puro per 60 sec. </li><li> Lavare il campione con acqua deionizzata per 10 secondi e poi asciugare il campione con azoto. </li><li> Caricare il campione in una spogliarellista plasma (SI-CV200RFS). Descum l&#39;esempio utilizzando 30 W di potenza RF a 30 ° C con un SCCM O portata 100 2 per 10 sec. </li><li> Rimuovere ossido superficiale immergendo in una HCl: H 2 0 3:10 miscela per 30 sec. Trasferire immediatamente il campione ad una cascata risciacquo di acqua deionizzata per 4 min. </li><li> Trasferire il campione in un bicchiere di acqua deionizzata per minimizzare l&#39;esposizione all&#39;ossigeno atmosferico prima deposizione metallica. </li><li> Prendere becher contenente il campione con acqua deionizzata ad un evaporatore metallo (Denton SJ-20). Ventilare la camera e quindi rimuovere, asciugare, e caricare il campione nella camera (questi passi devono essere seguite senza interruzione per impedire la formazione di ossido sulla superficie del campione). </li><li> Pompare la camera ad una pressione inferiore a 2x10 -6 Torr. Cassetta di Ti / Au (50/450 A). </li><li> Ventilare la camera e rimuovere il campione. </li><li> Al fine di lift-off del metallo depositato, posizionare il campione su un supporto in Teflon in unbicchiere di acetone, coprire e lasciare per una notte. Scoprire il bicchiere, collocarlo in un agitatore ad ultrasuoni, e attendere finché non viene rimosso tutti i metalli indesiderati (in genere 30 secondi). </li></ol></li><li> Cassetta di SiO 2 passivazione. <ol><li> Pulire il campione, come nei passi 1.1.1 - 1.1.2. </li><li> Caricare il campione in uno strumento di deposizione di vapore chimico plasma-enhanced (GSI PECVD). Cauzione 1500 A di SiO 2 a 200 ° C. </li></ol></li><li> Aprire vie di contatto con SiO 2. <ol><li> Pulire il campione, come nei passi 1.1.1 - 1.1.2. </li><li> Gira su HMDS a 4.000 giri per 30 sec. Gira su Megaposit SPR 220-3,0 photoresist a 4000 rpm per 30 sec. Pre-bake il resist su una piastra riscaldante a 115 ° C per 90 sec. </li><li> Caricare il campione e la piastra maschera in proiezione litografia passo-passo (GCA autostep 200). Allineare il campione ed esporre. </li><li> Post-cuocere il photoresist esposto su una piastra riscaldante a 115 ° C per 90 sec. </li><li> Sviluppare resistere in AZ 300 MIF sviluppatore per 60 sec. </li><li> Spostare il campione immediatamente ad una cascata risciacquo di acqua deionizzata per 4 min. Asciugare il campione con azoto. </li><li> Caricare il campione in uno ione incisore reattiva (LAM 9400). Etch SiO 2 con una potenza RF di TCP 500 W, un Bias potenza RF di 100 W, 15 SCCM di SF6, 50 sccm di C 4 F 8, 50 sccm di Lui, 50 SCCM di Ar per 80 sec. </li><li> Rimuovere il grosso del fotoresist ponendo il campione in acetone (5 min) seguito da isopropanolo (2 min). Sciacquare in acqua deionizzata (10 sec). Asciugare con azoto. </li><li> Rimuovere il photoresist residuo caricando il campione in una spogliarellista plasma (SI-CV200RFS). Rimuovere il fotoresist usando 800 W di potenza RF a 30 ° C con una portata SCCM O 100 2 per 5 min. </li></ol></li><li> Fabbricare antenne e linee di polarizzazione. <ol><li> Ripetere i punti 1.3.1 - 1.3.6 ad antenne modello e le linee diagonali. </li><li> Ripetere i punti 1.1.8 - 1.1.9 per rimuovere l&#39;ossido di superficie. </li><li> Prendete il bicchiere contenente il campione eacqua deionizzata ad un evaporatore metallo (Denton SJ-20). </li><li> Ventilare la camera e poi rimuovere rapidamente, asciugare, e caricare il campione nella camera. </li><li> Pompare la camera ad una pressione inferiore a 2x10 -6 Torr. Cassetta di Ti / Au (10/4, 000 A). </li><li> Ventilare la camera e rimuovere il campione. </li><li> Ripetere il passaggio 1.1.13 per il decollo del metallo depositato. </li></ol></li><li> Confezionare il campione. <ol><li> Incollare i bordi di diametro mm lente silicio iper-emisferica 12 ad una rondella di alluminio 2 pollici con foro 8 mm. </li><li> Incollare una scheda PCB con tracce di metallo, per cui si può facilmente saldare, per la rondella di alluminio. </li><li> Montare i plasmonic fotoconduttrici prototipi emettitore terahertz fabbricati sulla lente di silicio utilizzando resina epossidica sottile. </li><li> Obbligazionari Collegare il dispositivo di contatto pad ad una scheda PCB incollato sulla stessa rondella di alluminio. </li><li> Saldare i fili alle tracce metalliche sulla scheda PCB. </li><li> Collegare il dispositivo di cuscinetti di contatto ad un analizzatore parametrico (Hewlett Paccoard 4155A) con fili saldati ai corrispondenti rilievi del bordo del PWB a scopo di test. </li></ol></li></ol> 2. Plasmonica Caratterizzazione emettitore Photoconductive <ol><li> L&#39;allineamento del dispositivo. <ol><li> Posizionare la rondella di alluminio trasporta le plasmonic fotoconduttrici terahertz prototipi emettitore su un supporto di rotazione e strettamente focalizzare la pompa ottica da un Ti: zaffiro modo bloccato laser (MIRA 900D XW V10 OPT 110V) dentro l&#39;area attiva di ciascun dispositivo. </li><li> Regolare il montaggio in rotazione in modo tale che il campo elettrico della pompa ottica è orientata per l&#39;eccitazione efficiente delle onde plasmonica di superficie (normale alle griglie plasmonic). </li><li> Utilizzare l&#39;analizzatore parametrico di applicare simultaneamente tensioni di polarizzazione per ciascun dispositivo e misurare la corrente elettrica indotta in ogni dispositivo. Confermare l&#39;allineamento della pompa ottica ottimale e regolazione polarizzazione massimizzando la fotocorrente di ogni dispositivo in prova. </li></ol></li><li> Misura di potenza di uscitasura. <ol><li> Utilizzare un chopper ottico (Thorlabs MC2000) per modulare la pompa ottica dal mode-locked incidente laser della pompa su ogni dispositivo. </li><li> Misurare la potenza dei plasmonic fotoconduttrici prototipi emettitore terahertz utilizzando un rivelatore piroelettrico (Spectrum Detector, Inc. SPI-A-65 THz) in uscita. </li><li> Collegare l&#39;uscita del sensore piroelettrico a un amplificatore lock-in (Stanford Research Systems SR830) con frequenza di riferimento del chopper ottico per recuperare i dati di potenza terahertz a bassi livelli di rumorosità. </li></ol></li><li> Radiazioni caratterizzazione spettrale. <ol><li> Iniziare con un laser Ti: zaffiro modo bloccato e utilizzare un divisore di fascio per dividere l&#39;uscita del laser mode-locked in un fascio pompa e un fascio sonda. </li><li> Utilizzare un modulatore elettroottico (Thorlabs EO-AM-NR-C2) per modulare il fascio ottico nel percorso pompa. Focalizzare il fascio pompa sull&#39;area attiva dell&#39;emettitore fotoconduttivo in prova per generare radiazione terahertz. </li><li> Collimareil fascio terahertz generato utilizzando una prima lente sferica polietilene. Focalizzare il fascio collimato terahertz usando una seconda lente sferica polietilene. </li><li> Prima della messa a fuoco del fascio terahertz, combinare il fascio collimato terahertz con il fascio ottico sonda utilizzando un filtro di vetro rivestito ITO. </li><li> Posizionare un spessore di 1 mm, &lt;110&gt; cristallo ZnTe montato su un palco rotazione al fuoco combinato del fascio ottico e terahertz. </li><li> Inserire una linea di ritardo ottica controllabile nel percorso sonda ottica utilizzando una fase lineare motorizzato (Thorlabs NRT100) per variare il ritardo di tempo tra gli impulsi ottici e terahertz interagiscono all&#39;interno del cristallo ZnTe. </li><li> Utilizzando un mezzo waveplate nel percorso sonda, ruotare la polarizzazione della sonda ottica ad essere ad un angolo di 45 ° rispetto alla direzione di polarizzazione terahertz. </li><li> Utilizzare un quarto di waveplate dopo il cristallo ZnTe, convertire la polarizzazione fascio ottico in polarizzazione circolare. </li><li> Dividere il circulfascio ottico Arly polarizzato in due rami da un prisma di Wollaston. Misurare la potenza del fascio ottico in ciascun ramo usando due rivelatori bilanciati collegati ad un amplificatore di blocco. </li><li> Collegare la linea di ritardo motorizzata e amplificatore di blocco a un computer. Scrivere uno script Matlab per spostare iterativamente la posizione della linea di ritardo a motore, mettere in pausa, e leggere l&#39;ampiezza del segnale da amplificatore lock-in. </li><li> Convertire la posizione di fase nel dominio del tempo, attraverso dividendo la lunghezza totale ritardo ottico per la velocità della luce, seguita da una trasformata di Fourier discreta (utilizzando Matlab) per ottenere i dati del dominio di frequenza. </li></ol></li></ol>

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	<li>Preu, S., Dohler, G. H., Malzer, S., Wang, L. J., Gossard, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tunable,+continuous-wave+terahertz+photomixer+sources+and+applications.">Tunable, continuous-wave terahertz photomixer sources and applications.</a> J. Appl. Phys. 109, 061301 (2011).</li><li>Bjarnason, J. E., Chan, T. L. J., Lee, A. W. M., Brown, E. R., Driscoll, D. C., Hanson, M., Gossard, A. C., Muller, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ErAs:GaAs+photomixer+with+two-decade+tunability+and+12+&#956;W+peak+output+power.">ErAs:GaAs photomixer with two-decade tunability and 12 &#956;W peak output power.</a> Appl. Phys. Lett. 85, 3983-3985 (2004).</li><li>Peytavit, E., Lepilliet, S., Hindle, F., Coinon, C., Akalin, T., Ducournau, G., Mouret, G., Lampin, J. -. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Milliwatt-level+output+power+in+the+sub-terahertz+range+generated+by+photomixing+in+a+GaAs+photoconductor.">Milliwatt-level output power in the sub-terahertz range generated by photomixing in a GaAs photoconductor.</a> Appl. Phys. Lett. 99, 223508 (2011).</li><li>Upadhya, P. C., Fan, W., Burnett, A., Cunningham, J., Davies, A. G., Linfield, E. H., Lloyd-Hughes, J., Castro-Camus, E., Johnston, M. B., Beere, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitation-density-dependent+generation+of+broadband+terahertz+radiation+in+an+asymmetrically+excited+photoconductive+antenna.">Excitation-density-dependent generation of broadband terahertz radiation in an asymmetrically excited photoconductive antenna.</a> Opt. Lett. 32, 2297-2299 (2007).</li><li>Roehle, H., Dietz, R. J. B., Hensel, H. J., B&#246;ttcher, J., K&#252;nzel, H., Stanze, D., Schell, M., Sartorius, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Next+generation+1.5+&#956;m+terahertz+antennas:+mesa-structuring+of+InGaAs/InAlAs+photoconductive+layers.">Next generation 1.5 &#956;m terahertz antennas: mesa-structuring of InGaAs/InAlAs photoconductive layers.</a> Opt. Express. 18, 2296-2301 (2010).</li><li>Taylor, Z. D., Brown, E. R., Bjarnason, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resonant-optical-cavity+photoconductive+switch+with+0.5+%+conversion+efficiency+and+1.0W+peak+power.">Resonant-optical-cavity photoconductive switch with 0.5 % conversion efficiency and 1.0W peak power.</a> Opt. Lett. 31, 1729-1731 (2006).</li><li>Park, S. -. G., Jin, K. H., Yi, M., Ye, J. C., Ahn, J., Jeong, K. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+Terahertz+Pulse+Emission+by+Optical+Nanoantenna.">Enhancement of Terahertz Pulse Emission by Optical Nanoantenna.</a> ACS NANO. 6, 2026-2031 (2012).</li><li>Auston, D. H., Cheung, K. P., Smith, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Picosecond+photocoducting+Hertzian+dipoles.">Picosecond photocoducting Hertzian dipoles.</a> Appl. Phys. Lett. 45, 284-286 (1984).</li><li>Berry, C. W., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Terahertz+generation+using+plasmonic+photoconductive+gratings.">Terahertz generation using plasmonic photoconductive gratings.</a> New Journal of Physics Focus Issue on Terahertz Plasmonics. 14, 105029 (2012).</li><li>Berry, C. W., Hashemi, M. R., Unlu, M., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Significant+Radiation+Enhancement+in+Photoconductive+Terahertz+Emitters+by+Incorporating+Plasmonic+Contact+Electrodes.">Significant Radiation Enhancement in Photoconductive Terahertz Emitters by Incorporating Plasmonic Contact Electrodes.</a> arXiv. , 1209.1680v1 (2012).</li><li>Berry, C. W., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+Photoconductors+based+on+Plasmonic+Gratings.">Ultrafast Photoconductors based on Plasmonic Gratings.</a> Proc. Int. Conf. Infrared, Millimeter, and Terahertz Waves. , 1-2 (2011).</li><li>Berry, C. W., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmonically-enhanced+localization+of+light+into+photoconductive+antennas.">Plasmonically-enhanced localization of light into photoconductive antennas.</a> Proc. Conf. Lasers and Electro-Optics. , CFI2 (2010).</li><li>Berry, C. W., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Principles+of+impedance+matching+in+photoconductive+antennas.">Principles of impedance matching in photoconductive antennas.</a> Journal of Infrared, Millimeter and Terahertz. , (2012).</li><li>Ralph, S. E., Grischkowsky, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trap-enhanced+electric+fields+in+semi-insulators:+The+role+of+electrical+and+optical+carrier+injection.">Trap-enhanced electric fields in semi-insulators: The role of electrical and optical carrier injection.</a> Appl. Phys. Lett. 59, 1972 (1991).</li><li>Upadhya, P. C., Fan, W., Burnett, A., Cunningham, J., Davies, A. G., Linfield, E. H., Lloyd-Hughes, J., Castro-Camus, E., Johnston, M. B., Beere, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitation-density-dependent+generation+of+broadband+terahertz+radiation+in+an+asymmetrically+excited+photoconductive+antenna.">Excitation-density-dependent generation of broadband terahertz radiation in an asymmetrically excited photoconductive antenna.</a> Opt. Lett. 32, 2297-2299 (2007).</li><li>Taylor, Z. D., Brown, E. R., Bjarnason, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resonant-optical-cavity+photoconductive+switch+with+0.5+%+conversion+efficiency+and+1.0W+peak+power.">Resonant-optical-cavity photoconductive switch with 0.5 % conversion efficiency and 1.0W peak power.</a> Opt. Lett. 31, 1729-1731 (2006).</li><li>Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Terahertz+radiation-band+engineering+through+spatial+beam-shaping.">Terahertz radiation-band engineering through spatial beam-shaping.</a> Photonic Technology Letters. 21, 2019620 (2009).</li><li>Jarrahi, M., Lee, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+power+tunable+terahertz+generation+based+on+photoconductive+antenna+arrays.">High power tunable terahertz generation based on photoconductive antenna arrays.</a> Proc. IEEE International Microwave Symposium. , 391-394 (2008).</li><li>Beck, M., Schafer, H., Klatt, G., Demsar, J., Winnerl, S., Helm, M., Dekorsy, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impulsive+terahertz+radiation+with+high+electric+fields+from+an+amplifier-driven+large-area+photoconductive+antenna.">Impulsive terahertz radiation with high electric fields from an amplifier-driven large-area photoconductive antenna.</a> Opt. Express. 18, 9251-9257 (2010).</li><li>Hattori, T., Egawa, K., Ookuma, S. I., Itatani, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intense+terahertz+pulses+from+large-aperture+antenna+with+interdigitated+electrodes.">Intense terahertz pulses from large-aperture antenna with interdigitated electrodes.</a> Jpn. J. Appl. Phys. 45, L422-L424 (2006).</li><li>Kim, J. H., Polley, A., Ralph, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+photoconductive+terahertz+source+using+line+excitation.">Efficient photoconductive terahertz source using line excitation.</a> Opt. Lett. 30, 2490-2492 (2005).</li><li>Dreyhaupt, A., Winnerl, S., Dekorsy, T., Helm, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-intensity+terahertz+radiation+from+a+microstructured+large-area+photoconductor.">High-intensity terahertz radiation from a microstructured large-area photoconductor.</a> Appl. Phys. Lett. 86, 121114 (2005).</li><li>Brown, E. R., Lee, A. W. M., Navi, B. S., Bjarnason, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+planar+self-complementary+square-spiral+antenna+in+the+THz+region.">Characterization of a planar self-complementary square-spiral antenna in the THz region.</a> Microwave Opt. Technol. Lett. 48, 524-529 (2006).</li><li>Huo, Y., Taylor, G. W., Bansal, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Planar+log-periodic+antennas+on+extended+hemishperical+silicon+lenses+for+millimeter/submillimeter+wave+detection+applications.">Planar log-periodic antennas on extended hemishperical silicon lenses for millimeter/submillimeter wave detection applications.</a> Int. J. Infrared and Millimeter Waves. 23, 819 (2002).</li><li>Heshmat, B., Pahlevaninezhad, H., Pang, Y., Masnadi-Shirazi, M., Lewis, R. B., Tiedje, T., Gordon, R., Darcie, T. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nanoplasmonic Terahertz Photoconductive Switch on GaAs. Nano Lett. 12, 6255-6259 (2012).</li><li>Berry, C. W., Hashemi, M. R., Unlu, M., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Significant+Performance+Enhancement+in+Photoconductive+Terahertz+Optoelectronics+by+Incorporating+Plasmonic+Contact+Electrodes.">Significant Performance Enhancement in Photoconductive Terahertz Optoelectronics by Incorporating Plasmonic Contact Electrodes.</a> Nature Communications. 4, 1622 (2013).</li><li>Wang, N., Berry, C. W., Hashemi, M. R., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmonic+photoconductive+detectors+for+enhanced+terahertz+detection+sensitivity.">Plasmonic photoconductive detectors for enhanced terahertz detection sensitivity.</a> Optics Express. , (2013).</li><li>Hsieh, B. -. Y., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+periodic+metallic+nano-slits+for+efficient+interaction+of+terahertz+and+optical+waves+at+nano-scale+dimensions.">Analysis of periodic metallic nano-slits for efficient interaction of terahertz and optical waves at nano-scale dimensions.</a> J. Appl. Phys. 109, 084326 (2011).</li><li>Hsieh, B. -. Y., Wang, N., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+Ultrafast+Pump-Probe+Measurements+at+the+Nanoscale.+Special+Issue+of+"Optics+in+2011.">Toward Ultrafast Pump-Probe Measurements at the Nanoscale. Special Issue of "Optics in 2011.</a> Optics &amp; Photonics News. 22, (2011).</li><li>Hsieh, B. -. Y., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+focusing+of+terahertz+and+optical+waves+into+nano-scale.">Simultaneous focusing of terahertz and optical waves into nano-scale.</a> Proc. Int. Conf. Infrared, Millimeter, and Terahertz Waves. , 1-2 (2011).</li><li>Jackson, A. W., Ibbetson, J. P., Gossard, A. C., Mishra, U. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced+thermal+conductivity+in+low-temperature+grown+GaAs.">Reduced thermal conductivity in low-temperature grown GaAs.</a> Appl. Phys. Lett. 74, 2325-2327 (1999).</li></ol>

Nessun conflitto di interessi dichiarati.

In questo articolo video, presentiamo una tecnica di generazione terahertz fotoconduttivo romanzo che utilizza una configurazione di elettrodo di contatto plasmonica di migliorare l&#39;efficienza di conversione ottico-terahertz da due ordini di grandezza. Il significativo aumento della potenza di radiazione terahertz dagli emettitori fotoconduttrici plasmonic presentati è molto utile per il futuro ad alta sensibilità terahertz imaging, la spettroscopia e spettrometria di sistemi utilizzati per l&#39;identificazione c...

Presentiamo un romanzo emettitore terahertz fotoconduttivo che utilizza una configurazione di elettrodo di contatto plasmonica di migliorare l&#39;efficienza di conversione ottico-terahertz da due ordini di grandezza. La nostra tecnica si rivolge ai più importanti limitazioni convenzionali emettitori terahertz fotoconduttori, vale a dire a bassa potenza di uscita e la scarsa efficienza di potenza, che provengono dal compromesso intrinseco tra elevata efficienza quantica e il funzionamento ultraveloce di fotoconduttori convenzionali. Una delle novità chiave nella nostra progettazione che hanno portato a questo miglioramento delle prestazioni cavallina è quello di progettare una configurazione di elettrodo di contatto che accumula un gran numero di vettori foto-generati in prossimità degli elettrodi di contatto, tali da poter essere raccolti all&#39;interno di un sub- picosecondo scala cronologica. In altre parole, il compromesso tra funzionamento ultraveloce fotoconduttore ed alta efficienza quantica è mitigato dalla manipolazione spaziale del foto-generivettori TED. Elettrodi di contatto plasmoniche offrono questa capacità unica di (1) consentendo confinamento luce in dispositivi nanometrici aree attive tra gli elettrodi plasmonic (oltre il limite di diffrazione), (2) straordinario valorizzazione luce al contatto metallo e foto-assorbenti interfaccia semiconduttore 10, 11. Un altro attributo importante della nostra soluzione è che alloggia ampie aree attive fotoconduttore senza un notevole aumento del carico parassitario all&#39;antenna radiante terahertz. Utilizzando grandi aree attive fotoconduttore consentono mitigare l&#39;effetto di schermatura vettore e ripartizione termica, che sono i limiti ottimali per la massima potenza di radiazione da emettitori fotoconduttori convenzionali. In questo articolo il video si concentra sulle caratteristiche uniche della nostra soluzione presentata da descrivere la fisica che disciplinano, modellazione numerica e verifica sperimentale. Noi sperimentalmente Dimostriamo 50 volte superiori poteri terahertz da un phot plasmonicaemettitore oconductive in confronto con un emettitore fotoconduttiva simile con elettrodi di contatto non plasmonic.

<table border="1">
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 <td>Reagent</td>
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 <td>MicroChem</td>
 <td>950K PMMA A4</td>
 <td>&nbsp;</td>
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 <td>Hexamethyldisilazane (HMDS)</td>
 <td>Shin-Etsu MicroSI</td>
 <td>MicroPrime HP Primer</td>
 <td>&nbsp;</td>
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 <td>Optical Photoresist</td>
 <td>Dow Chemical</td>
 <td>Megaposit SPR 220-3.0</td>
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 <td>Photoresist Developer</td>
 <td>AZ Electronic Materials</td>
 <td>AZ 300 MIF Developer</td>
 <td>&nbsp;</td>
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 <td>Methyl Iso-Butyl Keytone (MIBK)</td>
 <td>Avantor Performance Materials</td>
 <td>9322-03</td>
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 <td>Equipment</td>
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 <td>Ti:Sapphire Mode-Locked Laser</td>
 <td>Coherent</td>
 <td>MIRA 900D V10 XW OPT 110V</td>
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 <td>Pyroelectric Detector</td>
 <td>Spectrum Detector</td>
 <td>SPI-A-65 THz</td>
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 <td>Electron-Beam Lithography Tool</td>
 <td>JEOL</td>
 <td>JBX-6300-FS</td>
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 <td>Plasma Stripper</td>
 <td>Yield Engineering Systems</td>
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 <td>Optical Chopper</td>
 <td>Thorlabs</td>
 <td>MC2000</td>
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 <td>Stanford Research Systems</td>
 <td>SR830</td>
 <td>&nbsp;</td>
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 <tr>
 <td>Electrooptic Modulator</td>
 <td>Thorlabs</td>
 <td>EO-AM-NR-C2</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Motorized Linear Stage</td>
 <td>Thorlabs</td>
 <td>NRT100</td>
 <td>&nbsp;</td>
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 </tbody>
</table>

design, fabrication, and experimental characterization of plasmonic photoconductive terahertz emitters

In questo articolo video presentiamo una dimostrazione dettagliata di un metodo molto efficiente per la generazione di onde terahertz. La nostra tecnica si basa su fotoconduzione, che è stato una delle tecniche più utilizzate per la generazione di terahertz 1-8. Generazione Terahertz in un emettitore fotoconduttiva si ottiene pompando un fotoconduttore ultraveloce con una illuminazione laser pulsato o heterodyned. La fotocorrente indotta, che segue l&#39;inviluppo del laser di pompa, viene instradato a un antenna irradiante terahertz collegata agli elettrodi di contatto fotoconduttore per generare radiazione terahertz. Anche se l&#39;efficienza quantica di un emettitore fotoconduttore può raggiungere teoricamente il 100%, i trasporti relativamente lunghi lunghezze dei percorsi dei vettori foto generati per gli elettrodi di contatto di fotoconduttori convenzionali hanno gravemente limitato la loro efficienza quantica. Inoltre, l&#39;effetto di schermatura vettore e ripartizione termica limitano rigorosamente la massima uscita potenza di fonti terahertz fotoconduttori convenzionali. Per affrontare i limiti di efficienza quantica di convenzionali emettitori terahertz fotoconduttori, abbiamo sviluppato un nuovo concetto di emettitore fotoconduttiva che incorpora una configurazione plasmonico elettrodo di contatto per offrire alta quantum-efficienza e il funzionamento ultraveloce contemporaneamente. Utilizzando nano-scala elettrodi di contatto plasmonic, riduciamo notevolmente il vettore foto-generated percorso medio di trasporto per fotoconduttori elettrodi di contatto rispetto a fotoconduttori convenzionali 9. Il nostro metodo permette anche di aumentare l&#39;area attiva fotoconduttore senza un notevole incremento del carico capacitivo all&#39;antenna, aumentando la potenza massima radiazione terahertz impedendo l&#39;effetto di schermatura vettore e ripartizione termica alle alte potenze ottico di pompa. Incorporando elettrodi di contatto plasmonic, dimostriamo migliorando l&#39;ottico-terahertz efficienza di conversione di potenza di un convenzionale fotoconduttivo terahertz emettitore di un fattore 50 10.

Per dimostrare le potenzialità di elettrodi plasmonic per terahertz valorizzazione potere, abbiamo inventato due emettitori terahertz: una convenzionale (Figura 1a) e plasmonica (Figura 1b) fotoconduttiva emettitore incorporando elettrodi di contatto plasmonica di ridurre i tempi di trasporto carrier di contattare elettrodi. Entrambi i modelli sono costituiti da un fotoconduttore ultraveloce con 20 micron gap tra anodo e catodo contatti, collegato ad un&#39;antenna papillon lunga 60 mi...

Watch this Scientific Journal Video about Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters at JoVE.com

Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

Descriviamo i metodi per la progettazione, la fabbricazione e la caratterizzazione sperimentale di emettitori fotoconduttrici plasmonica, che offrono due ordini di grandezza più elevati livelli di potenza terahertz rispetto agli emettitori fotoconduttori convenzionali.

Progettazione, fabbricazione, e Sperimentale Caratterizzazione di plasmoniche Emettitori Terahertz fotoconduttive

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on ...

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14.8K Views.  University of Michigan. Descriviamo i metodi per la progettazione, la fabbricazione e la caratterizzazione sperimentale di emettitori fotoconduttrici plasmonica, che offrono due ordini di grandezza più elevati livelli di potenza terahertz rispetto agli emettitori fotoconduttori convenzionali.

Video: Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators 1,2. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials.
Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides 3, asymmetric split-ring resonators 4, and photonic band gap structures integrated into parallel-plate waveguides 5. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc.
The sensor design we use here is based on a simple parallel-plate waveguide 6,7. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE1) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove 6,8. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index 9.
Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can be accomplished with standard laboratory equipment without the need for a clean room or any special fabrication or experimental techniques. It can also be easily expanded to multichannel operation by the incorporation of multiple grooves 10. In this video we will describe our complete experimental procedure, from the design of the sensor to the data analysis and determination of the sample refractive index.

The procedure for implementing a refractive index sensor for terahertz frequencies based on a grooved parallel-plate waveguide geometry is described here. The method yields a measurement of the refractive index of a small volume of liquid through monitoring of the shift in the resonant frequency of the waveguide structure

Terahertz Sensing microfluidici Utilizzando un parallelo-piastra sensore guida d&#39;onda

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic ...

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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

Simulazione, fabbricazione e caratterizzazione di THz Assorbitori metamateriale

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view and for its considerable potential for practical applications. Slow light photonic crystal waveguides, in particular, have played a major part and have been successfully employed for delaying optical signals1-4 and the enhancement of both linear5-7 and nonlinear devices.8-11
Photonic crystal cavities achieve similar effects to that of slow light waveguides, but over a reduced band-width. These cavities offer high Q-factor/volume ratio, for the realization of optically12 and electrically13 pumped ultra-low threshold lasers and the enhancement of nonlinear effects.14-16 Furthermore, passive filters17 and modulators18-19 have been demonstrated, exhibiting ultra-narrow line-width, high free-spectral range and record values of low energy consumption.
To attain these exciting results, a robust repeatable fabrication protocol must be developed. In this paper we take an in-depth look at our fabrication protocol which employs electron-beam lithography for the definition of photonic crystal patterns and uses wet and dry etching techniques. Our optimised fabrication recipe results in photonic crystals that do not suffer from vertical asymmetry and exhibit very good edge-wall roughness. We discuss the results of varying the etching parameters and the detrimental effects that they can have on a device, leading to a diagnostic route that can be taken to identify and eliminate similar issues.
The key to evaluating slow light waveguides is the passive characterization of transmission and group index spectra. Various methods have been reported, most notably resolving the Fabry-Perot fringes of the transmission spectrum20-21 and interferometric techniques.22-25 Here, we describe a direct, broadband measurement technique combining spectral interferometry with Fourier transform analysis.26 Our method stands out for its simplicity and power, as we can characterise a bare photonic crystal with access waveguides, without need for on-chip interference components, and the setup only consists of a Mach-Zehnder interferometer, with no need for moving parts and delay scans.
When characterising photonic crystal cavities, techniques involving internal sources21 or external waveguides directly coupled to the cavity27 impact on the performance of the cavity itself, thereby distorting the measurement. Here, we describe a novel and non-intrusive technique that makes use of a cross-polarised probe beam and is known as resonant scattering (RS), where the probe is coupled out-of plane into the cavity through an objective. The technique was first demonstrated by McCutcheon et al.28 and further developed by Galli et al.29

Use of photonic crystal slow light waveguides and cavities has been widely adopted by the photonics community in many differing applications. Therefore fabrication and characterization of these devices are of great interest. This paper outlines our fabrication technique and two optical characterization methods, namely: interferometric (waveguides) and resonant scattering (cavities).

Fabbricazione e caratterizzazione di guide d&#39;onda fotoniche di cristallo di luce lenta e cavità

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view ...

Fabrication and Characterization of Disordered Polymer Optical Fibers for Transverse Anderson Localization of Light

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed polymer optical fiber is composed of 80,000 strands of poly (methyl methacrylate) (PMMA) and polystyrene (PS) that are randomly mixed and drawn into a square cross section optical fiber with a side width of 250 &mu;m. Initially, each strand is 200 &mu;m in diameter and 8-inches long. During the mixing process of the original fiber strands, the fibers cross over each other; however, a large draw ratio guarantees that the refractive index profile is invariant along the length of the fiber for several tens of centimeters. The large refractive index difference of 0.1 between the disordered sites results in a small localized beam radius that is comparable to the beam radius of conventional optical fibers. The input light is launched from a standard single mode optical fiber using the butt-coupling method and the near-field output beam from the disordered fiber is imaged using a 40X objective and a CCD camera. The output beam diameter agrees well with the expected results from the numerical simulations. The disordered optical fiber presented in this work is the first device-level implementation of 2D Anderson localization, and can potentially be used for image transport and short-haul optical communication systems.

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. This microstructured fiber can transport a small localized beam with a radius that is comparable to the beam radius of conventional optical fibers.

Fabbricazione e caratterizzazione di polimeri disordinati fibre ottiche per la Trasversale localizzazione di Anderson di Luce

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

Patterning via ottici saturabili Transitions - fabbricazione e la caratterizzazione

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

La stampa Fabbricazione di massa eterogiunzione celle solari e<em&gt; In Situ</em&gt; Morfologia Caratterizzazione

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Free-form Light Actuators &amp;#8212; Fabrication and Control of Actuation in Microscopic Scale

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.

Free-forma Attuatori Light - Fabbricazione e Controllo di attuazione in scala microscopica

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Fabbricazione e caratterizzazione di superconduttori risonatori

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR is not affected by environmental characteristics such as the temperature and pressure surrounding the resonator. Electromagnetic radiation in THz frequencies is biocompatible, which is a critical condition especially for the application of the biomolecular sensing. However, the quality factor (Q-factor) and frequency responses of traditional thin-film based split ring resonator (SRR) MMs are very low, which limits their sensitivities and selectivity as sensors. In this work, novel nanopillar-based SRR MMs, utilizing displacement current, are designed to enhance the Q-factor up to 450, which is around 45 times higher than that of traditional thin-film-based MMs. In addition to the enhanced Q-factor, the nanopillar-based MMs induce a larger frequency shifts (17 times compared to the shift obtained by the traditional thin-film based MMs). Because of the significantly enhanced Q-factors and frequency shifts as well as the property of biocompatible radiation, the THz nanopillar-based SRR are ideal MMs for the development of biomolecular sensors with high sensitivity and selectivity without inducing damage or distortion to biomaterials. A novel fabrication process has been demonstrated to build the nanopillar-based SRRs for displacement current mediated THz MMs. A two-step gold (Au) electroplating process and an atomic layer deposition (ALD) process are used to create sub-10 nm scale gaps between Au nanopillars. Since the ALD process is a conformal coating process, a uniform aluminum oxide (Al2O3) layer with nanometer-scale thickness can be achieved. By sequentially electroplating another Au thin film to fill the spaces between Al2O3 and Au, a close-packed Au-Al2O3-Au structure with nano-scale Al2O3 gaps can be fabricated. The size of the nano-gaps can be well defined by precisely controlling the deposition cycles of the ALD process, which has an accuracy of 0.1 nm.

A protocol for the design and fabrication of a novel nanopillar-based split ring resonator (SRR) is presented.

Fabbricazione di Nanopillar-Based Split Ring risonatori di corrente di spostamento mediata Risonanze a Terahertz metamateriali

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR ...

Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters

Here, we demonstrate the advantages of the laser Doppler vibrometer (LDV) over conventional techniques (the network analyzer), as well as the techniques to create an application-based microelectromechanical systems (MEMS) filter and how to use it efficiently (i.e., tuning the tuning-capability and avoiding both failure and stiction). LDV enables crucial measurements that are impossible with the network analyzer, such as higher mode detection (highly sensitive biosensor application) and resonance measurement for very small devices (fast prototyping). Accordingly, LDV was used to characterize the frequency tuning range and resonance frequency at different modes of the MEMS filters built for this study. This wide range frequency tuning mechanism is based simply on Joule heating from the embedded heaters and relatively high thermal stress with respect to the temperature of a fixed-fixed beam. However, we demonstrate that another limitation of this method is the resulting high thermal stress, which can burn the devices. Further improvement was achieved and shown for the first time in this study, such that the tuning capability was increased by 32% through an increase in the applied DC bias voltage (25 V to 35 V) between the two adjacent beams. This important finding eliminates the need for the extra Joule heating at the wider frequency tuning range. Another possible failure is through stiction and requirement of structure optimization: We propose a simple and easy technique of low frequency square wave signal application that can successfully separate the beams and eliminates the need for the more sophisticated and complicated methods given in the literature. The above findings necessitate a design methodology, and so we also provide an application-based design.

A protocol for a fixed-fixed beam design using a laser Doppler vibrometer (LDV), including the measurement of frequency tuning, modification of tuning capability, and avoidance of device failure and stiction, is presented. The superiority of the LDV method over the network analyzer is demonstrated due to its higher mode capability.

Progettazione e nella metodologia di caratterizzazione per efficiente ampio intervallo sintonizzabile MEMS filtri

Here, we demonstrate the advantages of the laser Doppler vibrometer (LDV) over conventional techniques (the network analyzer), as well as the techniques ...