Die Autoren möchten Picometrix für die Bereitstellung der LT-GaAs-Substrat danken und bedanken uns für die finanzielle Unterstützung von Michigan Raum Grants Consortium, DARPA Young Faculty Award von Dr. John Albrecht (contract # N66001-10-1-4027), NSF CAREER verwaltet Auszeichnung verwaltet von Dr. Samir El-Ghazaly (contract # N00014-11-1-0096), ONR Young Investigator Award von Dr. Paul Maki (contract # N00014-12-1-0947) verwaltet, und ARO Young Investigator Award verwaltet von Dr. Dev Palmer (contract # W911NF-12-1-0253).

1. Plasmonic Photoconductive Emitter Fabrication <ol><li> Fabricate plasmonischen Gittern. <ol><li> Reinigen des Halbleiterwafers durch Eintauchen in Aceton (2 min) und Isopropanol (2 min), gefolgt, und Spülen mit deionisiertem Wasser (10 sec). </li><li> Trocknen der Probe mit Stickstoff und erhitzt es auf einer Heizplatte bei 115 ° C für 90 sec, um das restliche Wasser zu entfernen. </li><li> Spin MicroChem 950K PMMA A4 auf der Probe bei 4000 rpm für 45 sec. Pre-Bake das auf einer Heizplatte bei 180 ° C für 3 min zu widerstehen. </li><li> Legen Sie die Probe in einer Elektronenstrahl-Lithographie-Werkzeug (JEOL JBX-6300-FS). Freilegen plasmonischen Gittermuster an einer Basis Dosis rund 650 uC / cm 2, mit einem 100 kV Beschleunigungsspannung. </li><li> Entwickeln PMMA durch Eintauchen der Probe in einer MIBK: IPA 1:3-Gemisch für 90 sek. Sofortige Umsetzen der Probe in einer Lösung von reinem Isopropanol für 60 sek. </li><li> Spülen Sie die Probe mit VE-Wasser für 10 Sekunden und dann trocknen die Probe mit Stickstoff. </li><li> Legen Sie die Probe in ein Plasma Stripper (YES-CV200RFS). Descum die Probe mit 30 W HF-Leistung bei 30 ° C mit einer 100 sccm O 2-Flussrate für 10 sec. </li><li> Entfernen Oberflächenoxids durch Eintauchen in eine HCl: H 2 0 3.10 Mischung für 30 Sekunden. Sofortige Umsetzen der Probe mit einem Kaskadenspüle entionisiertes Wasser 4 min. </li><li> Übertragen der Probe in ein Becherglas mit entionisiertem Wasser auf dem Luftsauerstoff vor Metallabscheidung zu minimieren. </li><li> Nehmen Behälter gegeben, der mit entionisiertem Wasser auf einen Metall-Verdampfer (Denton SJ-20). Entlüften Sie die Kammer und dann zu entfernen, trocknen, und laden Sie die Probe in die Kammer (diese Schritte sollten ohne Unterbrechung folgen, um Oberfläche Oxidbildung auf der Probe zu verhindern). </li><li> Pumpen der Kammer auf einen Druck unter 2x10 -6 Torr. Kaution Ti / Au (50/450 A). </li><li> Entlüften Sie die Kammer und entfernen Sie die Probe. </li><li> Um ein Abheben der abgeschiedenen Metall, legen Sie die Probe auf einem Teflon-Halter in einBecherglas mit Aceton, abdecken und über Nacht einwirken lassen. Entdecken Sie das Becherglas, legen Sie sie in einem Ultraschall-Agitator, und warten, bis alle unerwünschten Metall entfernt (in der Regel 30 Sekunden). </li></ol></li><li> Kaution SiO2 Passivierung. <ol><li> Reinigen Sie die Probe wie in den Schritten 1.1.1 - 1.1.2. </li><li> Legen Sie die Probe in ein Plasma Enhanced Chemical Vapour Deposition-Werkzeug (GSI PECVD). Kaution 1500 A von SiO 2 bei 200 ° C </li></ol></li><li> Öffnen Kontaktvias durch SiO2. <ol><li> Reinigen Sie die Probe wie in den Schritten 1.1.1 - 1.1.2. </li><li> Spin auf HMDS bei 4.000 rpm für 30 sec. Spin auf Megaposit SPR 220 bis 3,0 Fotolack bei 4.000 rpm für 30 sec. Pre-Bake das auf einer Heizplatte widerstehen bei 115 ° C für 90 sec. </li><li> Legen Sie die Probe und Maske Platte in Projektion Lithographie Stepper (GCA autostep 200). Richten Sie die Probe und freizulegen. </li><li> Post-backen der belichteten Fotolack auf einer Heizplatte bei 115 ° C für 90 sec. </li><li> Entwickeln widerstehen in AZ 300 MIF Entwickler für 60 sec. </li><li> Unmittelbar bewegen die Probe einer Kaskadenspüle entionisiertem Wasser für 4 min. Trocknen Sie die Probe mit Stickstoff. </li><li> Legen Sie die Probe in einem reaktiven Ionenätzer (LAM 9400). Etch SiO 2 unter Verwendung eines TCP-HF-Leistung von 500 W, einer Vorspannung HF-Leistung von 100 W, 15 sccm SF6-, 50 sccm C 4 F 8, 50 sccm He, 50 sccm Ar für 80 sek. </li><li> Entfernen der Großteil des Photoresists, indem die Probe in Aceton (5 min) mit Isopropanol (2 min) gefolgt. Spülen in entionisiertem Wasser (10 sec). Mit Stickstoff trocken. </li><li> Entfernen Sie die restliche Fotolack durch das Laden der Probe in ein Plasma Stripper (YES-CV200RFS). Entfernen Sie den Fotolack mit 800 W HF-Leistung bei 30 ° C mit einer 100 sccm O 2-Flussrate für 5 min. </li></ol></li><li> Fabricate Antennen und Biasleitungen. <ol><li> Wiederholen Sie die Schritte 1.3.1 - 1.3.6 auf Musters Antennen und Biasleitungen. </li><li> Wiederholen Sie die Schritte 1.1.8 - 1.1.9 zu Oberflächenoxid entfernen. </li><li> Nehmen Sie das Becherglas mit der Probe unddeionisiertem Wasser auf einen Metall-Verdampfer (Denton SJ-20). </li><li> Entlüften Sie die Kammer und dann schnell zu entfernen, trocknen, und laden Sie die Probe in die Kammer. </li><li> Pumpen der Kammer auf einen Druck unter 2x10 -6 Torr. Kaution Ti / Au (10/4, 000 Å). </li><li> Entlüften Sie die Kammer und entfernen Sie die Probe. </li><li> Wiederholen Sie Schritt 1.1.13 zu Abheben das abgeschiedene Metall. </li></ol></li><li> Packen Sie die Probe. <ol><li> Kleben Sie die Kanten eines 12 mm Durchmesser hyper-Silizium halbkugelförmige Linse zu einem 2-Zoll-Aluminium-Unterlegscheibe mit 8 mm Loch. </li><li> Kleben Sie ein Leiterplatte mit Metall Spuren, um die man sich leicht löten, mit dem Aluminium Unterlegscheibe. </li><li> Montieren Sie die hergestellt plasmonischen photoleitenden Terahertz-Emitter-Prototypen auf dem Silizium-Linse mit dünnen Epoxy. </li><li> Draht-Bindung das Gerät Kontaktflächen zu einer Platine auf dem gleichen Aluminium-Scheibe geklebt. </li><li> Solder Drähte an den Metall-Spuren auf der Leiterplatte. </li><li> Schließen Sie das Gerät Kontaktstellen zu einer parametrischen Analysator (Hewlett-Packard 4155A) unter Verwendung von Drähten gelötet zu den entsprechenden Pads der Leiterplatte für Testzwecke. </li></ol></li></ol> 2. Plasmonic Photoconductive Emitter Charakterisierung <ol><li> Geräte-Ausrichtung. <ol><li> Legen Sie die Unterlegscheibe Aluminium trägt die Plasmonen photoleitenden Terahertz-Emitter Prototypen auf einer Montierung und Rotation fest konzentrieren die optische Pumpe aus einem Ti: Saphir-Laser (MIRA 900D XW V10 OPT 110V) auf der aktiven Fläche von jedem Gerät modengekoppelter. </li><li> Einstellen der Drehung Halterung, so dass das elektrische Feld von der optischen Pumpe ausgerichtet für eine effiziente Anregung Oberflächenplasmonwellen (senkrecht zu den Plasmonen-Gitter) ist. </li><li> Verwenden Sie die parametrische Analysator, um gleichzeitig Vorspannungen an jedes Gerät und messen die induzierte elektrische Strom in jedes Gerät. Bestätigen Sie die optimale optische Ausrichtung der Pumpe und Polarisierung Anpassung durch die Maximierung der Photostrom jedes Prüflings. </li></ol></li><li> Ausgangsleistung Maßnahmensung. <ol><li> Verwenden Sie ein optisches Chopper (Thorlabs MC2000) zur Modulation der optischen Pumpe aus dem modengekoppelter Pumplaser Vorfall auf jedem Gerät. </li><li> Messen der Ausgangsleistung der Plasmonen photoleitfähigen Terahertz-Emitter-Prototypen mit einem pyroelektrischen Detektor (Detector Spectrum, Inc. SPI-A-65 THz). </li><li> Verbinden Sie den Ausgang des pyroelektrischen Detektors ein Lock-in-Verstärker (Stanford Research Systems SR830) mit dem optischen Chopper Referenzfrequenz auf Terahertz-Leistungsdaten bei niedrigem Geräuschpegel erholen. </li></ol></li><li> Radiation spektrale Charakterisierung. <ol><li> Starten mit einem Ti: Saphir modengekoppelten Laser und mit einem Strahlteiler, um den Ausgang des modengekoppelten Lasers in einem Pumpstrahl und ein Meßstrahl aufgeteilt. </li><li> Verwendung einer elektrooptischen Modulator (Thorlabs EO-AM-NR-C2) zum Modulieren des optischen Strahls in der Pumpe Pfad. Konzentrieren der Pumpstrahl auf den aktiven Bereich der photoleitfähigen Emitter zu prüfenden Terahertz-Strahlung zu erzeugen. </li><li> Visierendas erzeugte Terahertzstrahl Verwendung eines ersten Polyethylens sphärische Linse. Fokus des kollimierten Terahertzstrahl Verwendung eines zweiten Polyethylen sphärische Linse. </li><li> Bevor der Schwerpunkt des Terahertzstrahl verbinden den kollimierten Terahertzstrahl mit der Sonde optischen Strahls unter Verwendung eines ITO-beschichtetes Glas-Filter. </li><li> Legen Sie eine 1 mm dicke, &lt;110&gt; ZnTe Kristall montiert auf einer Drehung der Bühne des kombinierten Fokus des optischen und Terahertzstrahl. </li><li> Einfügen eines steuerbaren optischen Verzögerungsleitung in der optischen Sonde Pfad unter Verwendung eines motorisierten Lineartisch (Thorlabs NRT100), um die Zeitverzögerung zwischen der optischen und Terahertzimpulsen Interaktion innerhalb der ZnTe-Kristall variieren. </li><li> Mit einem Halbwellenplatte in der Sonde weg, drehen die Polarisation der optischen Sonde, um in einem 45 ° Winkel relativ zu der Polarisationsrichtung Terahertz sein. </li><li> Verwenden Sie eine Viertel-Wellenplatte nach dem ZnTe Kristall, wandeln die optischen Strahls Polarisation in zirkulare Polarisation. </li><li> Teilen Sie die circularly polarisierten Lichtstrahl in zwei Zweige von einem Wollaston-Prisma. Messen Sie die optische Strahlungsleistung in jedem Zweig mit zwei symmetrischen Detektoren mit einem Lock-in-Verstärker. </li><li> Schließen Sie das motorisierte Delay-Line und Lock-in-Verstärker an einen Computer. Schreiben Sie eine Matlab-Skript, um iterativ bewegen die Position des motorisierten Delay-Line, Pause, und lesen Sie die Signalstärke von der Lock-in-Verstärker. </li><li> Konvertieren der Tischposition in den Zeitbereich durch Dividieren der gesamten optischen Verzögerung Länge durch die Lichtgeschwindigkeit, gefolgt von einer diskreten Fourier-Transformation (Matlab) in den Frequenzbereich zu erhalten. </li></ol></li></ol>

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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>

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In diesem Video-Artikel präsentieren wir eine neue Generation photoleitenden Terahertz-Technik, die eine plasmonischen Kontakt-Elektroden-Konfiguration verwendet, um die optisch-Terahertz-Wirkungsgrad von zwei Größenordnungen verbessern. Der deutliche Anstieg in der Terahertz-Strahlung Strom aus den vorgestellten plasmonischen photoleitenden Strahler ist sehr wertvoll für zukünftige hochempfindliche Terahertz-Bildgebung, Spektroskopie und Spektrometrie für fortschrittliche chemische Identifizierung verwendet, medi...

Wir präsentieren einen neuartigen Terahertz-Emitter photoleitenden die eine plasmonischen Kontakt-Elektroden-Konfiguration verwendet, um die optisch-Terahertz-Wirkungsgrad von zwei Größenordnungen verbessern. Unsere Technik geht die wichtigsten Beschränkungen herkömmlicher photoleitfähigen Terahertz-Sender, nämlich niedriger Ausgangsleistung und schlechter Wirkungsgrad, die aus der inhärenten Kompromiß zwischen hoher Quanteneffizienz und ultraschnellen Betrieb von herkömmlichen Photoleiter stammen. Eine der wichtigsten Neuerungen in unserem Design, das zu dieser Bockspringen Leistungsverbesserung geführt ist, um einen Kontakt-Elektroden-Konfiguration, die eine große Anzahl von Foto-generierten Ladungsträger in unmittelbarer Nähe zu den Kontakt-Elektroden, sammelt so zu konzipieren, dass sie innerhalb gesammelt werden kann ein Sub- Pikosekunden-Zeitskala. In anderen Worten wird der Kompromiss zwischen Fotoleiter ultraschnelle Bedienung und hohe Quanteneffizienz durch räumliche Manipulation des photo-Gattungen gemildertted Airlines. Plasmonic Kontakt-Elektroden bieten diese einzigartige Fähigkeit von (1) ermöglicht Lichtbegrenzungsschicht in nanoskalige Gerät aktiven Bereiche zwischen den Elektroden plasmonischen (jenseits Beugungsgrenze), (2) Erweiterung außerordentliches Licht an der Metall-Kontakt und Foto-absorbierenden Halbleiter-Grenzfläche 10, 11. Ein weiteres wichtiges Merkmal unserer Lösung ist, dass es große Photoleiter aktiven Bereiche beherbergt ohne erhebliche Steigerung der parasitäre Belastung der Terahertz strahlende Antenne. Mit Hilfe großer Photoleiter aktiven Bereiche ermöglichen Milderung der Träger-Screening-Effekt und thermischen Abbau, die die ultimativen Grenzen für die maximale Strahlungsleistung von herkömmlichen photoleitenden Strahler sind. Dieses Video Artikel basiert auf den einzigartigen Eigenschaften unserer vorgestellte Lösung durch die Beschreibung der über Physik, numerische Modellierung und experimentelle Verifikation konzentriert. Wir experimentell zeigen 50-mal höhere Mächte von einem Terahertz plasmonischen photoconductive Emitter im Vergleich mit einer ähnlichen photoleitfähigen Emitter mit nicht-Plasmonen Kontaktelektroden.

<table border="1">
 <tbody>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Reagent</td>
 </tr>
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 <td>Polymethyl Methacrylate (PMMA)</td>
 <td>MicroChem</td>
 <td>950K PMMA A4</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Hexamethyldisilazane (HMDS)</td>
 <td>Shin-Etsu MicroSI</td>
 <td>MicroPrime HP Primer</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Optical Photoresist</td>
 <td>Dow Chemical</td>
 <td>Megaposit SPR 220-3.0</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Photoresist Developer</td>
 <td>AZ Electronic Materials</td>
 <td>AZ 300 MIF Developer</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Methyl Iso-Butyl Keytone (MIBK)</td>
 <td>Avantor Performance Materials</td>
 <td>9322-03</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Equipment</td>
 </tr>
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 <td>Ti:Sapphire Mode-Locked Laser</td>
 <td>Coherent</td>
 <td>MIRA 900D V10 XW OPT 110V</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Pyroelectric Detector</td>
 <td>Spectrum Detector</td>
 <td>SPI-A-65 THz</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Electron-Beam Lithography Tool</td>
 <td>JEOL</td>
 <td>JBX-6300-FS</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Plasma Stripper</td>
 <td>Yield Engineering Systems</td>
 <td>YES-CV200RFS</td>
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 </tr>
 <tr>
 <td>Metal Evaporator</td>
 <td>Denton Vacuum</td>
 <td>SJ-20</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Plasma Enhanced Chemical Vapor Deposition Tool</td>
 <td>GSI</td>
 <td>GSI PECVD System</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Projection Lithography Stepper</td>
 <td>GCA</td>
 <td>AutoStep 200</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Reactive Ion Etcher</td>
 <td>LAM Research</td>
 <td>9400</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Parameter Analyzer</td>
 <td>Hewlett Packard</td>
 <td>4155A</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Optical Chopper</td>
 <td>Thorlabs</td>
 <td>MC2000</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Lock-in Amplifier</td>
 <td>Stanford Research Systems</td>
 <td>SR830</td>
 <td>&nbsp;</td>
 </tr>
 <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>
 </tr>
 </tbody>
</table>

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

In diesem Video-Artikel präsentieren wir eine detaillierte Demonstration eines hocheffizienten Verfahren zur Erzeugung von Terahertz-Wellen. Unsere Technik basiert auf Photoleitfähigkeit, das einer der am häufigsten verwendeten Techniken zum Terahertzerzeugung 1-8 hat basiert. Terahertzerzeugung in einer photoleitfähigen Emitter durch Pumpen eines ultraschnellen Photoleiter mit einem gepulsten oder überlagerten Laserbestrahlung erzielt. Der induzierte Photostrom, der die Hüllkurve des Pumplasers folgt, auf eine Terahertz-Sendeantenne, die mit den Photoleiter Kontaktelektroden zum Terahertz-Strahlung zu erzeugen geleitet. Obwohl die Quanteneffizienz einer photoleitfähigen Emitter theoretisch 100% erreichen kann, sind die relativ langen Transportweg Längen der foto-erzeugten Träger mit den Kontaktelektroden der herkömmlichen Photoleiter stark ihre Quantenausbeute begrenzt. Zusätzlich kann der Träger-Screening-Effekt und thermischen Abbau strikt zu begrenzen die maximale Leistung power konventioneller photoleitenden Terahertz-Quellen. Um die Quanteneffizienz Beschränkungen herkömmlicher photoleitenden Terahertz-Emitter anzugehen, haben wir ein neues Konzept, das photoleitende Emitter eine plasmonischen Kontakt-Elektroden-Konfiguration auf hohe Quanten-Effizienz und ultraschnellen Betrieb bieten gleichzeitig integriert entwickelt. Durch die Verwendung von Nano-Plasmonen Kontakt-Elektroden, wir deutliche Verkürzung der durchschnittlichen Foto-generated Träger Transportweg Photoleiter Kontakt-Elektroden im Vergleich zu herkömmlichen Photoleiter 9. Unsere Methode ermöglicht es auch zunehmende Photoleiter aktiven Fläche ohne erhebliche Steigerung der kapazitiven Belastung der Antenne, die Förderung der Terahertz-Strahlung maximale Leistung durch die Verhinderung der Träger abschirmende Wirkung und thermischer Zerfall bei hohen optischen Pumpleistung. Durch die Integration von Plasmonen Kontaktelektroden zeigen wir, Verbesserung der optischen Terahertz-to-Wirkungsgrad von einer herkömmlichen lichtleitenden terahertz Emitter um einen Faktor von 50 10.

Eine herkömmliche (Abbildung 1a) und Plasmonen (Abbildung 1b) photoleitenden Emitter Einbeziehung plasmonischen Kontakt Elektroden Träger Transportzeiten zu reduzieren, um Elektroden an: Um das Potenzial der Plasmonen-Elektroden für Terahertz Leistungssteigerung zu demonstrieren, haben wir zwei Terahertz-Emitter hergestellt. Beide Ausführungen bestehen aus einem ultraschnellen Photoleiter mit 20 um Spalt zwischen Anode und Kathode Kontakte, verbunden mit einer 60 um lang Bowtie-Ante...

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

Wir beschreiben Methoden für die Konstruktion, Fertigung und experimentelle Charakterisierung plasmonischen photoleitenden Emitter, die zwei Größenordnungen höher Terahertz-Leistung im Vergleich zu herkömmlichen Strahlern photoleitenden anbieten.

Konstruktion, Fertigung und experimentelle Charakterisierung Plasmonic Photoconductive Terahertz-Emitter

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 Aufrufe.  University of Michigan. Wir beschreiben Methoden für die Konstruktion, Fertigung und experimentelle Charakterisierung plasmonischen photoleitenden Emitter, die zwei Größenordnungen höher Terahertz-Leistung im Vergleich zu herkömmlichen Strahlern photoleitenden anbieten.

Serie: 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 Microfluidic Sensing mit einem Parallel-Platte Waveguide Sensor

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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Ingenieurwesen

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.

Simulation, Herstellung und Charakterisierung von THz Metamaterial Absorber

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).

Herstellung und Charakterisierung von Photonic Crystal Langsam Lichtwellenleitern und Hohlräume

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.

Herstellung und Charakterisierung von Disordered Optische Polymerfasern für Quer 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 ...

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.

Strukturierung via Optical Saturable Transitions - Herstellung und Charakterisierung

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.

Printing Herstellung von Bulk-Heterosolarzellen und<em&gt; In Situ</em&gt; Morphologie Charakterisierung

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.

Freiform-Lichtaktoren - Herstellung und Steuerung der Betätigung in mikroskopischer Skala

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.

Herstellung und Charakterisierung von Superconducting Resonators

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.

Die Herstellung von Nanopillar-Based Split-Ring-Resonatoren für Verschiebungsstrom Mediated Resonances in Terahertz Metamaterialien

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.

Design und Charakterisierung Methodik für effiziente Weitbereichs-abstimmbaren MEMS-Filter

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