This work was supported by the Natural Science and Engineering Research Council of Canada (Discovery Grant No. 122795-2010) and the program of the Canada Research Chair in Quantum Semiconductors (JJD). The help provided by Xiaohuan Xuang, Mohamed Walid Hassen and technical assistance of Sonia Blais of the Universit&#233; de Sherbrooke Centre de caract&#233;risation de mat&#233;riaux (CCM) in collecting XPS data are greatly appreciated. NL acknowledges the Merit Scholarship Program for Foreign Student, Fonds de recherche du Qu&#233;bec - Nature et technologies, for providing a graduate student scholarship.

Preparazione 1. campione <ol><li> Utilizzare uno scriba diamode per fendere un tipo n (drogato P-) un lato lucido Si wafer (resistività 3.1 ~ 4.8 Ω.m) che è 3 pollici di diametro, 380 micron di spessore, in campioni da 12 mm x 6 mm; pulire i campioni in OptiClear, acetone e alcool isopropilico (5 min per ogni passo). </li><li> Etch campioni in una soluzione di HF ~ 0,9% per 1 min a etch via ossido iniziale; risciacquo in acqua deionizzata e asciugare elevata purezza (99,999%) di azoto (N 2). </li><li> Conservare i campioni preparati in N 2 borsa per frenare la loro ossidazione in aria. </li></ol> 2. irradiano Sample per ArF (λ = 193 nm) e KrF (λ = 248 nm) Laser. <ol><li> I campioni in una camera alto 0,74 millimetri e quindi sigillare la camera con una finestra di silice fusa che ha alta trasmissione UV (≥90%). Riempire la camera con H 2 O 2 / H 2 O soluzione nell&#39;intervallo 0.01-0.2% o con metha degasatonol utilizzando un canale microfluidica. </li><li> Irradiare campioni con omogeneizzati laser ARF o KrF a demagnification di 2,6 e 1,8, rispettivamente. Irradiare solo 2 siti su ogni campione aumentando impulsi laser da 100 a 600 in fase di 100 impulsi attraverso una maschera circolare (4 mm di diametro). Irradiare i campioni nello stesso modo con una &quot;foglia di acero&quot; (9 mm x 7.2 mm) maschera. </li><li> Campioni Sciacquare in acqua deionizzata, asciugare con N 2 a filo; Porre i campioni in un contenitore sigillato, quindi riempire rapidamente questo contenitore con N 2, al fine di evitare l&#39;esposizione all&#39;aria prima ulteriori esperimenti. </li></ol> 3. Nanosfere immobilizzazione di Bio-coniugati <ol><li> Diluire nanosfere 40 nm di diametro biotina-coniugato con fluoresceina e tinto in una soluzione salina tamponata con fosfato pH 7,4 (PBS, 1X), soluzione al 10 12 particelle / ml a temperatura ambiente (~ 25 ° C). Immergere i campioni laser irradiati ARF o KrF per 2 &amp;# 160; hr in questa soluzione a temperatura ambiente. </li><li> Lavare i campioni con PBS per eliminare fisicamente rilegati fluoresceina nanosfere colorate sulla superficie. </li></ol> Caratterizzazione 4. Superficie <ol><li> Angolo di contatto (CA) di misura <ol><li> Effettuare misure CA statiche con un goniometro in un ambiente di RT e umidità ambiente. </li><li> Impiegare acqua ad elevata purezza DI (resistività 17,95 MW · cm) in un micro-siringa; generare volume analogo (~ 5 microlitri) gocce sulla superficie del campione abbassando il micro-siringa per un&#39;altezza simile per ogni misurazione. </li><li> Catturare e salvare le gocce d&#39;acqua immagini del profilo di camera CCD con il software. Misura indipendente 4 siti diversi con condizioni di irraggiamento stessi. </li><li> Stima e la media dei valori di CA nel modulo di analisi goccia da software ImageJ; caricare l&#39;immagine e cambiare in scala di grigi; lanciare il plugin Dropsnake; collocare circa un paio di nodi sul contorno goccia (~ 10 nodi) da sinistra agiusto per inizializzare serpente; accettare la curva che collega questi nodi ed evolvere la curva premendo il tasto serpente. Nota: angoli di contatto sono visualizzate nell&#39;immagine e la tabella. </li></ol></li><li> Misurazione XPS <ol><li> Indagare superficie modificazione chimica con uno spettrometro XPS (1x10 -9 Torr pressione di base) dotato di una fonte di Al Kα lavoro a 150 W: <ol><li> Caricare i campioni nella camera a vuoto. </li><li> Acquisire i dati dell&#39;indagine superficie in modalità di energia costante di 50 eV passaggio di energia da una zona di 220 micron x 220 micron. </li><li> Acquisire dati ad alta risoluzione scansioni dalla stessa zona analizzata a 20 eV passano energia. </li></ol></li><li> Processo XPS dati spettri con il software di quantificazione spettri XPS, come riferito 25,26. </li></ol></li><li> Imaging di fluorescenza microscopio <ol><li> Excite campioni, che sono stati irradiati attraverso la &quot;foglia d&#39;acero&quot; maschera e esposti a fluoresceina nanosfere macchiati, utilizzandouna sorgente di luce blu (λ = 450 ~ 490 nm). </li><li> Osservare immagini fluorescenti, che emette a 515 nm, con un microscopio a fluorescenza invertito in 4x. </li><li> Caratterizzare la morfologia superficiale di questi campioni con AFM, come riferimento 27. </li></ol></li></ol>

The authors have nothing to disclose.

Abbiamo proposto un protocollo di irradiazione laser UV wafer di Si in una camera riempita con microfluidica bassa concentrazione di H 2 O 2 soluzione per indurre una superficie Si superidrofilia, che è principalmente dovuta alla generazione di Si-OH. Fotolisi laser UV di H 2 O 2 doveva formare carica negativa OH - radicali. Inoltre, laser UV effetto fotoelettrico porta alla formazione di una superficie carica positiva 37. Quindi, l&#39;interazione di qu...

Le notevoli proprietà elettroniche e chimiche, nonché la sua elevata resistenza meccanica hanno fatto silicio (Si) la scelta ideale per i dispositivi microelettronici e chip biomedicali 1. Controllo area selettiva della superficie di Si ha ricevuto notevole attenzione per le applicazioni che coinvolgono microfluidica e dispositivi lab-on-chip 2,3 .Questo è spesso ottenuta o da modifiche nano-scala della rugosità superficiale o trattamento chimico della superficie 4. L&#39;irruvidimento superficie o patterning per produrre strutture di superficie disordinati o ordinati sulla superficie di Si includono fotolitografia 5, agli ioni di litografia a fascio 6 e tecniche laser 7. Rispetto a questi metodi, laser processo ruvido di superficie è segnalato per essere meno complicato con il potenziale di produrre microstrutture ad alta risoluzione spaziale 8. Tuttavia, come Si ha una soglia texturing elevata, richiedendo irraggiamento con impulsi di fluenzaindurre texturing superficiale supera la soglia di ablazione (~ 500 mJ / cm 2) 9, texturing di superficie Si è spesso stata assistita impiegando atmosfere gassose reattive, come quella di alta pressione SF6 ambiente 4,7,8. Di conseguenza, di modificare la bagnabilità della superficie di Si, numerosi lavori si sono concentrati sul trattamento chimico depositando organici ed inorganici 10 film 2, o usando plasma o fascio elettronico trattamento superficiale 11,12. Si riconosce che idrofilia di Si proveniente dalla presenza di gruppi OH e singolari associati sulla sua superficie potrebbe essere realizzato mediante ebollizione in una soluzione H 2 O 2 a 100 ° C per alcuni minuti 13. Tuttavia, le idrofobiche stati superficiali Si, la maggior parte dei quali sono dovuti alla presenza di Si-H o Si-O-CH 3 gruppi, possono essere raggiunti mediante manipolazione chimica umida coinvolge attacco con soluzione di acido HF o rivestimento con fotoresist 13-15. Per ottenere il controllo area selettiva di bagnabilità di Si, passi patterning complessi sono solitamente richiesti, compreso il trattamento in soluzioni chimiche 16. L&#39;elevata reattività chimica della radiazione laser UV è stato utilizzato anche per rivestite substrati solidi processo area selettiva pellicola organica e modificare la loro bagnabilità 17. Tuttavia, una quantità limitata di dati è accessibile laser assistita modifica di Si bagnabilità mediante irradiazione di campioni immersi in diverse soluzioni chimiche. Nella nostra precedente ricerca, irraggiamento laser UV di semiconduttori III-V in aria 18-20 e NH 3 21 è stato utilizzato con successo per alterare la composizione chimica della superficie di GaAs, InGaAs e InP. Abbiamo stabilito che l&#39;irradiazione laser UV di semiconduttori III-V in deionizzata (DI) diminuisce ossidi superficiali e carburi, mentre l&#39;acqua adsorbita sulla superficie del semiconduttore aumenta 22. Una superficie fortemente idrofobica Si (CA ~ 103 °) è stato ottenuto da ArF laser irradiazione di campioni di Si in metanolo nel nostro lavoro recente 23. Come indicato dalla spettroscopia fotoelettronica a raggi X (XPS), ciò è dovuto principalmente alla capacità del laser ArF a photodissociate CH 3 OH. Abbiamo usato anche KrF e laser ARF irradiare Si (001) in un 0,01% di H 2 O 2 in acqua deionizzata. Questo ci ha permesso di ottenere la formazione area selettiva di superficiale superidrofilia di Si (001) caratterizzato dalla CA di quasi 15 °. I risultati suggeriscono che XPS questo è dovuto alla generazione di legami Si-OH sulla superficie irradiata 24. Una descrizione dettagliata di questa nuova tecnica usando KrF e laser ARF per area selettiva in situ modificazione della superficie idrofila / idrofobica superficie Si in bassa concentrazione di H 2 O 2 / H 2 O e soluzioni di metanolo è dimostrato in questo articolo. I dati forniti qui dovrebbero essere sufficientiper consentire esperimenti simili di essere effettuati da ricercatori interessati.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>fluorescein stained nanospheres</td>
			<td>Invitrogen</td>
			<td>F8795</td>
			<td></td>
		</tr>
		<tr>
			<td>OptiClear</td>
			<td>National Diagnostics</td>
			<td>OE-101</td>
			<td></td>
		</tr>
		<tr>
			<td>ArF laser (&#955;=193 nm)</td>
			<td>Lumonics</td>
			<td>pulse master 800</td>
			<td></td>
		</tr>
		<tr>
			<td>KrF laser (&#955;=248 nm)</td>
			<td>Lumonics</td>
			<td>pulse master 800</td>
			<td></td>
		</tr>
		<tr>
			<td>XPS</td>
			<td>Kratos Analytical</td>
			<td>AXIS Ultra DLD</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence microscope</td>
			<td>Olympus</td>
			<td>IX71</td>
			<td></td>
		</tr>
		<tr>
			<td>XPS quantitification software</td>
			<td>CasaXPS</td>
			<td>2.3.15</td>
			<td></td>
		</tr>
	</tbody>
</table>

selective area modification of silicon surface wettability by pulsed uv laser irradiation in liquid environment

La bagnabilità di silicio (Si) è uno dei parametri importanti nella tecnologia di funzionalizzazione superficiale di questo materiale e fabbricazione di biosensori. Segnaliamo su un protocollo di utilizzo KrF e ARF laser irradiano Si (001) campioni immersi in un ambiente liquido a basso numero di impulsi e di operare a fluenze impulsi moderatamente bassi per indurre Si modifica bagnabilità. Wafer immersi per un massimo di 4 ore in un 0,01% di H 2 / H soluzione O 2 O 2 non ha mostrato cambiamento misurabile nel loro angolo di contatto iniziale (CA) ~ 75 °. Tuttavia, il 500-pulse KrF e laser ARF irradiazione di tali wafer in una microcamera riempito con 0,01% H 2 O 2 / H 2 O soluzione a 250 e 65 mJ / cm 2, rispettivamente, è diminuito il CA a quasi 15 °, indicanti la formazione di una superficie superidrofilia. La formazione di OH-terminato Si (001), con nessuna variazione misurabile totali morfologia del wafer, hastata confermata mediante spettroscopia fotoelettronica a raggi X e le misure di microscopia forza atomica. I campioni sono stati irradiati area selettiva poi immersi in una soluzione fluoresceina nanosfere macchiate biotina-coniugato per 2 ore, con un conseguente immobilizzazione successo delle nanosfere della zona non irradiato. Questo illustra il potenziale del metodo di selettiva biofunzionalizzazione area e realizzazione di architetture avanzate biosensori basati-Si. Descriviamo un protocollo simile di irradiazione di wafer immerse in metanolo (CH 3 OH) con laser ArF operante a impulsi fluenza di 65 mJ / cm 2 e formazione in situ di una superficie fortemente idrofobica di Si (001) con il CA di 103 °. I risultati indicano XPS laser indotta formazione ArF di Si- (OCH 3) x composti responsabili del idrofobicità osservato. Tuttavia, tali composti sono stati trovati da XPS sulla superficie di Si irradiato da KrF laser in metanolo, dimostrandol&#39;incapacità del laser a KrF photodissociate metanolo e creare -OCH 3 radicali.

Questi risultati rappresentativi sono stati presentati nella precedente lavoro pubblicato 23,24. La figura 1 mostra il CA vs. N (numero di impulsi) di siti irradiata dal laser KrF a 250 mJ / cm 2 in DI H 2 O per diverse concentrazioni di H 2 O 2 / H 2 O soluzioni (ad es., 0,01, 0,02, 0,05 e 0,2%). Il CA diminuisce all&#39;aumentare numero di impulsi per tutti gli H 2 O 2 soluzioni. Il CA minima (~ 15 °) per...

Watch this Scientific Journal Video about Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment at JoVE.com

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

Riportiamo un processo di alterazione in situ di HF trattata Si (001) superficie in uno stato idrofilo o idrofobo irradiando campioni in camere microfluidica riempiti con H 2 O 2 / H 2 O soluzione (0,01% -0,5%) o soluzioni di metanolo per mezzo del laser pulsato UV di un parente a bassa fluenza impulso.

Area selettiva Modifica della Silicon bagnabilità della superficie da impulsi laser UV irradiazione in ambiente liquido

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

selective-area-modification-silicon-surface-wettability-pulsed-uv

Research

JoVE Journal

Engineering

8.2K Views.  Université de Sherbrooke.  Riportiamo un processo di alterazione in situ di HF trattata Si (001) superficie in uno stato idrofilo o idrofobo irradiando campioni in camere microfluidica riempiti con H 2 O 2 / H 2 O soluzione (0,01% -0,5%) o soluzioni di metanolo per mezzo del laser pulsato UV di un parente a bassa fluenza impulso. 

Video: Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11.
Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps).
Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators.

An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.

Indagine su Evolution Plasma precoce indotta da impulsi laser ultracorti

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

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Ingegneria

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

Caratterizzazione delle modificazioni superficiali di White Interferometria Luce: Applicazioni in Ion Sputtering, ablazione laser, ed esperimenti Tribologia

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Fabbricazione di nano-ingegneria trasparenti Ossidi Conducting da Pulsed Laser Deposition

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Visualizzazione di Liquid High Speed ​​Jet Occlusione su una superficie mobile

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

Integrazione di luce Trapping Argento Nanostrutture in silicio microcristallino idrogenato celle solari tramite bonifico stampa

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

Automazione della modalità di bloccaggio in una rotazione in fibra laser non lineare di polarizzazione attraverso l&#39;uscita di polarizzazione Misure

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Emissione spettroscopica Boundary Investigation strato durante ablativo Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

Fabbricazione ad alta temperatura di Nanostrutturati di ossido di ittrio stabilizzato-Zirconia (YSZ) Ponteggi da<em&gt; In Situ</em&gt; Carbon Templating xerogel

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

Preparazione delle reti di cristalli liquidi per moto oscillatorio macroscopica indotta da luce

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

During vacuum induction melting, laser-induced breakdown spectroscopy is used to perform real-time quantitative analysis of the main-ingredient elements of a molten alloy.

Analisi quantitativa della fusione a induzione sottovuoto mediante spettroscopia di ripartizione indotta da laser

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves ...