Gli autori desiderano ringraziare con gratitudine il sostegno finanziario previsto per questo studio dalla National Science Foundation (Grant No: CMMI-0653578, cbet-0853890).

1. Configurazione del sistema ottico (Fig. 1) <ol><li> Impostare una semionda piastra e un polarizzatore dopo l&#39;uscita laser per regolare l&#39;energia dell&#39;impulso laser. </li><li> Impostare un divisore di fascio dopo il polarizzatore per dividere l&#39;impulso laser a due impulsi: impulso di pompa e impulso di sonda. </li><li> Utilizzare quattro specchi riflettenti e un palco di traslazione manuale per costruire un dispositivo ottico di ritardo per l&#39;impulso di pompa. </li><li> Utilizzare altri quattro specchi riflettenti per guidare l&#39;impulso di pompa di raggiungere la superficie bersaglio verticalmente. </li><li> Impostare un generatore di seconda armonica (SHG) per trasformare la lunghezza d&#39;onda laser ad impulsi da 800 nm a 400 nm. </li><li> Usare un separatore armonica di trasmettere il 800-nm polso e riflettono la 400-nm impulsi. </li><li> Impostare un riduttore trave ed una coppia di lenti focalmente per regolare la dimensione e la convergenza del l&#39;impulso di sonda. </li><li> Impostare un altro dispositivo ottico di ritardo, come indicato al punto 1.3, per l&#39;impulso di sonda. </li><li> Utilizzare un anello di Iris per regolare l&#39;area disonda impulsi e assicurarsi che l&#39;impulso di sonda passare la superficie di destinazione e si intersecano in orizzontale con l&#39;impulso di pompa. </li><li> Impostare due lenti di obiettivo e filtri diversi per generare l&#39;immagine della regione di plasma per essere ricevuto dal intensificata Charge-Coupled Device (ICCD) telecamera. </li><li> Collegare il computer, il laser, la fotocamera ICCD e il suo controllore tramite cavi BNC o cavi USB. </li><li> Regolare il tempo di ritardo del controller della videocamera fino alla macchina fotografica cattura un&#39;immagine del polso sonda. Così, l&#39;impulso di sonda e la fotocamera sono sincronizzati. </li></ol> 2. Pump-probe sincronizzazione <ol><li> Posizionare un divisore di fascio nel punto di intersezione del polso pompa e l&#39;impulso di sonda, e ha istituito due fotodiodi di ricevere questi due impulsi. Questi due fotodiodi dovrebbero avere una stessa distanza dal divisore di fascio. </li><li> Utilizzare un oscilloscopio per ricevere i segnali di questi due fotodiodi, e spostare la stadio di ritardo sul percorso del fascio impulso di pompa fino al profile di impulso di pompa e l&#39;impulso di sonda si sovrappongono tra loro sullo schermo dell&#39;oscilloscopio. Una precisione di 20 ps viene raggiunto grazie alla risoluzione temporale dell&#39;oscilloscopio. </li><li> Rimuovere il divisore di fascio e le due fotodiodi, come indicato nel passaggio 2,1. </li><li> Regolare la fase di ritardo sul percorso del fascio impulso di pompa fino alla regione di ripartizione dell&#39;aria potrebbe semplicemente essere osservato sullo schermo ICCD. Il tempo in cui la formazione di ripartizione dell&#39;aria potrebbe essere rilevato invece di uno sfondo uniforme è determinata come zero ritardo. </li></ol> 3. Preparazione del campione e stage <ol><li> Impostare un laboratorio-jack e due le fasi manuali lineari al fine di spostare il campione con tre gradi di libertà. </li><li> Un comparatore e spessori di alta precisione per ottenere una elevata planarità delle fasi. La differenza di altezza dovrebbe essere entro 1 micron per una distanza di 25,4 mm. </li><li> Tagliare un pezzo quadrato (30 mm x 30 mm) su un foglio di Cu con uno spessore di 0,8 mm utilizzando una fresatricemacchina. </li><li> Lucidare un lato stretto (30 mm x 0,8 mm) del pezzo Cu fino a quando la ruvidità superficiale è inferiore a 0,5 um. </li><li> Fissare il pezzo Cu sul palco manuale da tavolo con la faccia lucida stretta up. </li><li> Spostare l&#39;obiettivo da una fase manuale, come indicato al punto 3.1), mentre monitorare la sua posizione tramite la fotocamera ICCD in modo tale che qualsiasi inclinazione può essere regolato inserendo spessori di alta precisione al di sotto del target. </li><li> Ripetere il passaggio 3,6 con la fase manuale altra. </li><li> Eseguire una dozzina di fori sul bersaglio mentre variare la posizione della lente focale una terza fase manuale alta precisione. La posizione del punto focale corrisponde alla posizione della lente focale in cui è praticato il foro più piccolo. </li></ol> 4. Ablazione e di misura <ol><li> Spostare la lente focale fino a una distanza di circa 50 micron di distanza dal punto focale. </li><li> Spostare la fase di ritardo sul percorso del fascio impulso di sonda con un intervallo di 0,3 mm per catturare l&#39;immagine ogni 2 ps fino a 10 ps, ​​ocon un intervallo di 3 mm per catturare l&#39;immagine ogni 20 ps fino a 480 ps. </li><li> Ripetere il passaggio 4.2 per parecchie volte di ripetibilità e precisione. </li><li> Spostare la lente focale fino a una distanza di circa 50 micron di distanza dal punto focale, e ripetere il punto 4.3. </li></ol> 5. Risultati rappresentativi Le immagini shadowgraph misurati sono mostrati in fig. 2 e Fig. 3, per il punto focale leggermente sopra e sotto la superficie del bersaglio, rispettivamente. Le posizioni di espansione radiale e longitudinali sono riportati in Fig. 4 e Fig. 5. Le espansioni longitudinali di questi due casi i primi 100 ps sono significativamente differenti, tuttavia, le espansioni longitudinali nella seguente 400 ps e le espansioni radiali sono simili. Per il primo caso, il plasma primo raggio di 100 ps ha una struttura tridimensionale espansione costituiti da più strati. Per il secondo caso, il primo plAsma ha una struttura bidimensionale di espansione che non cambia molto nel raggio di 100 ps. Il modello di simulazione 12 è utilizzato per studiare il meccanismo dell&#39;evoluzione plasma precoce. Tempo zero è definito come il tempo in cui il laser ad impulsi di picco raggiunge la superficie bersaglio. I primi simulati processi di evoluzione plasma accordo con i risultati misurati per entrambi questi due casi, come mostrato in fig. 6 e Fig. 7, rispettivamente. La formazione del plasma primo raggio di 1 ps è anche previsto per il primo caso utilizzando il modello di simulazione e di fig. 8. Il plasma iniziale si trova ad avere una regione scomposizione aria e una regione di plasma Cu. La composizione dell&#39;aria viene prima causata da multi-photon ionizzazione e poi seguita da ionizzazione valanga. Per il secondo caso, invece, il punto focale si trova sotto la superficie bersaglio e non separato regione disaggregazione aria viene formata. Invece, ionizzazione dell&#39;aria avviene in prossimità del PLA Cufronte SMA ed è causata da ionizzazione per impatto a causa degli elettroni liberi espulsi dal bersaglio Cu. <img alt="Figura 1" src="/files/ftp_upload/4033/4033fig1.jpg" /> Figura 1. Schematica della pompa-sonda di misurazione shadowgraph. <img alt="Figura 2" src="/files/ftp_upload/4033/4033fig2.jpg" /> Figura 2. Cu espansione plasma in tempi successivi di ritardo con il punto focale leggermente sopra la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 W / cm 2; target: Cu. <img alt="Figura 3" src="/files/ftp_upload/4033/4033fig3.jpg" /> Figura 3. Cu espansione plasma in tempi successivi di ritardo con il punto focale leggermente sotto la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 W / cm 2; target: Cu. &lt;img alt = &quot;Figura 4&quot; src = &quot;/ files/ftp_upload/4033/4033fig4.jpg&quot; /&gt; Figura 4. Plasma longitudinali e posizioni espansione radiale in tempi di ritardo successivi con il punto focale leggermente sopra la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 W / cm 2; target: Cu. <img alt="Figura 5" src="/files/ftp_upload/4033/4033fig5.jpg" /> Figura 5. Plasma longitudinali e posizioni espansione radiale in tempi successivi di ritardo con il punto focale leggermente sotto la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 W / cm 2; target: Cu. Figura 6. Animazione di espansione plasma misurato e calcolato in un tempo di ritardo di 70 ps con il punto focale leggermente sopra la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 </sup&gt; W / cm 2; target: Cu. <a href="http://www.jove.com/files/ftp_upload/4033/4033movie6.avi" target="_blank">Clicca qui per visualizzare l&#39;animazione</a> . Figura 7. Animazione di espansione plasma misurato e calcolato in un tempo di ritardo di 70 ps con il punto focale leggermente sotto la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 W / cm 2; target: Cu. <a href="http://www.jove.com/files/ftp_upload/4033/4033movie7.avi" target="_blank">Clicca qui per visualizzare l&#39;animazione</a> . Figura 8. Animazione di espansione plasma misurato e calcolato in un tempo di ritardo di 1 ps con il punto focale leggermente sopra la superficie. Lunghezza d&#39;onda: 800 nm, durata dell&#39;impulso: 100 fs; densità di potenza: 4,2 × 10 14 W / cm 2; target:. Cu <a href="http://www.jove.com/files/ftp_upload/4033/4033movie8.avi" target="_blank">Clicca qui per visualizzare l&#39;animazione &lt;</a>/ A&gt;.

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Non ci sono conflitti di interesse dichiarati.

I metodi di misurazione e simulazione presentati in questo documento consentono esami più accurati delle dinamiche plasmatici iniziali e una migliore comprensione dei meccanismi di ionizzazione sia per aria e Cu. Strutture di plasma di alta qualità, vengono catturate con una risoluzione temporale di 1 ps e una risoluzione spaziale di 1 um. Questa misura ha una elevata ripetibilità troppo. La procedura è critico per allineare il raggio molto bene e preparare una superficie bersaglio con una elevata planarità e una bassa rugosità. Questo approccio può essere applicato a materiali bersaglio e altri parametri laser diversi. L&#39;unica limitazione della pompa-sonda metodo shadowgraph è un numero troppo basso di variazione della densità di elettroni.

<table border="1"><tbody><tr><td> Nome dell&#39;apparecchiatura </td><td> Azienda </td><td> Numero di catalogo </td></tr><tr><td> Laser </td><td> Spectra-Physics </td><td> SPTF-100F-1K-1P </td></tr><tr><td> ICCD fotocamera </td><td> Princeton Instruments </td><td> 7467-0028 </td></tr><tr><td> Oscilloscopio </td><td> Rigol </td><td> DS1302CA </td></tr><tr><td> Fotodiodo </td><td> Newport </td><td> 818-BB30 </td></tr><tr><td> Fase lineare </td><td> Newport </td><td> 433 </td></tr><tr><td> Comparatore </td><td> Mitutoyo </td><td> ID-C112E </td></tr></tbody></table>

investigation of early plasma evolution induced by ultrashort laser pulses

Plasma precoce è generato a causa di radiazione laser ad alta intensità di target e la conseguente ionizzazione materiale bersaglio. Le dinamiche gioca un ruolo significativo nella laser-materiale interazione, soprattutto in ambiente di aria 1-11. L&#39;evoluzione plasma precoce è stata catturata attraverso la pompa-sonda shadowgraphy 1-3 e interferometria 1,4-7. Tuttavia, i tempi studiato ed applicato intervalli di parametri laser sono limitati. Ad esempio, esami diretti di posizioni frontali plasma e densità numero di elettroni entro un tempo di ritardo di 100 picosecondi (ps) rispetto al picco dell&#39;impulso laser sono ancora poche, soprattutto per l&#39;impulso ultracorto di durata circa 100 femtosecondi (fs) e una densità di potenza a bassa circa 10 14 W / cm 2. All&#39;inizio plasma generato in queste condizioni è stato catturato solo di recente con alte risoluzioni spaziali e temporali 12. La strategia di configurazione dettagliata eprocedure di questa misurazione di alta precisione saranno illustrate in questo documento. La logica della misurazione è ottico pompa-probe shadowgraphy: un laser ad impulsi ultracorti è diviso in un impulso di pompa e un impulso di sonda, mentre il tempo di ritardo tra loro può essere regolata cambiando la loro lunghezza percorso di fascio. L&#39;impulso di pompa ablazione il bersaglio e genera il plasma precoce, e l&#39;impulso di sonda si propaga attraverso la regione di plasma e rileva la non uniformità della densità numero di elettroni. Inoltre, animazioni vengono generati utilizzando i risultati calcolati dal modello di simulazione di rif. 12 per illustrare la formazione di plasma ed evoluzione con una risoluzione molto elevata (0,04 ~ 1 ps). Sia il metodo sperimentale e il metodo di simulazione può essere applicato ad un&#39;ampia gamma di tempi e parametri del laser. Questi metodi possono essere utilizzati per esaminare il plasma generato precoce non solo da metalli, ma anche da semiconduttori e isolanti.

Watch this Scientific Journal Video about Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses at JoVE.com

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Un metodo sperimentale per esaminare l&#39;evoluzione primi plasma indotto da impulsi laser ultracorti è descritto. Utilizzando questo metodo, immagini di alta qualità di plasma primi si ottengono con alte risoluzioni spaziali e temporali. Un romanzo modello integrato atomistico viene utilizzato per simulare e spiegare i meccanismi di plasma precoce.

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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14.9K Views.  Purdue University. Un metodo sperimentale per esaminare l'evoluzione primi plasma indotto da impulsi laser ultracorti è descritto. Utilizzando questo metodo, immagini di alta qualità di plasma primi si ottengono con alte risoluzioni spaziali e temporali. Un romanzo modello integrato atomistico viene utilizzato per simulare e spiegare i meccanismi di plasma precoce.

Video: Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

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, ...

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Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1&#160;to 24 hr&#160;after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 &#956;m. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response:&#160;elemental, molecular, or cellular.

Laser-induced breakdown spectroscopy performed on thin organ and tumor tissue successfully detected natural elements and artificially injected gadolinium (Gd), issued from Gd-based nanoparticles. Images of chemical elements reached a resolution of 100 &#956;m and quantitative sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of a same biological tissue.

Spettroscopia Laser-Induced Breakdown: un nuovo approccio per la mappatura di nanoparticelle e la quantificazione in Tissue Organ

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) ...

Laser-induced Forward Transfer for Flip-chip Packaging of Single Dies

Flip-chip (FC) packaging is a key technology for realizing high performance, ultra-miniaturized and high-density circuits in the micro-electronics industry. In this technique the chip and/or the substrate is bumped and the two are bonded via these conductive bumps. Many bumping techniques have been developed and intensively investigated since the introduction of the FC technology in 19601 such as stencil printing, stud bumping, evaporation and electroless/electroplating2. Despite the progress that these methods have made they all suffer from one or more than one drawbacks that need to be addressed such as cost, complex processing steps, high processing temperatures, manufacturing time and most importantly the lack of flexibility. In this paper, we demonstrate a simple and cost-effective laser-based bump forming technique known as Laser-induced Forward Transfer (LIFT)3. Using the LIFT technique a wide range of bump materials can be printed in a single-step with great flexibility, high speed and accuracy at RT. In addition, LIFT enables the bumping and bonding down to chip-scale, which is critical for fabricating ultra-miniature circuitry.

We demonstrate the use of the Laser-induced Forward Transfer (LIFT) technique for flip-chip assembly of optoelectronic components. This approach provides a simple, cost-effective, low-temperature, fast and flexible solution for fine-pitch bumping and bonding on chip-scale for achieving high-density circuits for optoelectronic applications.

Laser-indotta Transfer Forward per Flip-chip Packaging di Dies Singolo

Flip-chip (FC) packaging is a key technology for realizing high performance, ultra-miniaturized and high-density circuits in the micro-electronics ...

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

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

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 ...

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

Come Ignite una Pressione atmosferica Microonde torcia al plasma senza alcuna accenditori supplementari

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

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 ...

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

We demonstrate the use of the Laser-induced forward transfer technique (LIFT) for the printing of high-viscosity Ag paste. This technique offers a simple, low temperature, robust process for non-lithographically printing microscale 2D and 3D structures.

Indotta da laser trasferimento di andata di Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of ...

An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of &#39;high&#39; voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

An experimental setup was created for the helium-operated kHz frequency plasma jet. The setup includes a cage for the plasma power supply and jet and an in-house built reactor to monitor plasma-induced reactive species without the interference of the ambient atmosphere.

Una configurazione plasma a pressione atmosferica per Indagare sulla formazione reattiva Specie

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. ...

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

Fabbricazione di 1-D Photonic cristallo cavità su una nanofibre Utilizzando ablazione laser a femtosecondi-indotta

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

Localizzazione dei difetti suburfacea mediante riscaldamento strutturato utilizzando la termografia fototermica proiettata laser

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...