Search results for "Generation"

Thermal expansion, normalized thermo-optic coefficients, and condition for second harmonic generation of a Nd:YAG laser with wide temperature bandwid…

2011

Interferometric determination of thermal expansion and of normalized thermo-optic coefficients of RbTiOPO4 at four laser wavelengths are performed as a function of temperature. A suitable vectorial formalism applied to obtained data allows the establishment of the temperature dependence of refractive indices, and subsequent theoretical analysis enables one to predict that an extremum in the evolution of the phase-matching direction in the (X,Y) plane should occur near 100 °C for type II second harmonic generation of Nd:YAG lasers, with a temperature bandwidth that can be as large as 117 °C for a crystal of 10 mm in length. Such unusual behavior is observed experimentally by recording the co…

Continuous-wave, double-pass second-harmonic generation with 60% efficiency in a single MgO:PPSLT crystal

2014

We present a double-pass scheme for high-efficiency, high-power, second-harmonic generation (SHG) in a single MgO-doped periodically poled stoichiometric lithium tantalate (MgO:PPSLT) crystal. The device is pumped by a single-frequency, continuous-wave fiber amplifier laser system at a wavelength of 1091 nm. For the double-pass scheme, a conversion efficiency of 60% and a harmonic power of 12.8 W at a wavelength of 545.5 nm with a high beam quality of (M2<1.2) is achieved. Compared to single-pass SHG, a double-pass enhancement factor of more than two is observed at the highest fundamental pump power.

Laser Beam Lithography For 3-D Surface Patterning

1993

A low power laser processing unit, for microlithographic applications on non-planar surfaces, is described. By combining proper laser beam handling, micropositioning, software control and surface coating techniques, a 5-axis robotic system for laser writing has been set up. Light from a He-Cd laser source is fiber-delivered to a writing head, which moves around a resist coated solid object. After exposure, traditional wet processing can be applied. The unit is capable of patterning metal films deposited on samples up to a size of 50x50x100 mm, with 5 micrometer spatial resolution. An application in 3-D circuit fabrication is presented.

Combined heat and power generation with a HCPV system at 2000 suns

2015

In the framework of the FAE “Fotovoltaico ad Alta Efficienza” (“High Efficiency Photovoltaic”) Research Project funded by the Sicilian Region under the program PO FESR Sicilia 2007/2013 4.1.1.1, we have developed an innovative solar CHP system for the combined production of heat and power at the high concentration level of 2000 suns [1]. This work shows the experimental results obtained on FAE-HCPV modules and analyses the behaviour of the system. The solar radiation is concentrated on commercial InGaP/InGaAs/Ge triple-junction solar cells designed for intensive work. The primary optics is a rectangular off-axis parabolic mirror (with a size of 46x46 = 2116 cm2 in a projection normal to the…

Amphiphilic dyes for nonlinear optics: Dependence of second harmonic generation on functional group substitution

2008

DC and 1/f noise characterization of cryogenically cooled pseudomorphic HEMT's

2002

Pseudomorphic (AlGaAs/InGaAs/GaAs) HEMT's have exhibited the best noise performance over the entire LF-to-microwave frequency range if compared to MESFET's and conventional GaAs HEMT's, due to either a reduced flicker noise, a lower G/R contribution and a smaller high-field diffusion noise. We have recently investigated the microwave (up to 18 GHz) noise properties of packaged pseudomorphic HEMT's from 290 K down to cryogenic temperature values. The current experimental work is aimed at extending such analysis to the LF noise range and at low temperatures. Cryogenic noise spectra (1 Hz to 100 KHz) and DC characteristics have therefore been recorded and the relevant observations on the devic…

Surface Periodic Poling in Lithium Niobate and Lithium Tantalate

2005

Periodic Poling of Lithium Niobate crystals (PPLN) by means of electric field has revealed the best technique for finely tailoring PPLN structures and parameters, which play a central role in many current researches in the field of nonlinear integrated optics. Besides the most studied technique of bulk poling, recently a novel technique where domain inversion occurs just in a surface layer using photoresist or silica masks has been devised and studied. This surface periodic poling (SPP) approach is best suited when light is confined in a thin surface guiding layer or stripe, as in the case of optical waveguide devices. Also, we found that SPP respect to bulk poling offers two orders of magn…

Synthesis and nonlinear optical properties of novel N,N-dihydroxyethyl-based molecular organic glasses using triaryl substitutes as amorphous phase f…

2011

In given study a new structural design of molecular NLO materials is presented where amorphous phase formation is achieved by introduction of bulky trityl and triphenylsilyl substituents. Obtained materials formed stable organic glasses with good optical quality and glass transition temperatures notably exceeding ambient. NLO activity was successfully measured in samples that underwent corona discharge poling. The comparison of both enhancer groups revealed, that trityl group increases thermal sustainability of material, while triphenylsilyl group better promotes formation and stability of amorphous phase.

Numerical analysis of light soaking phenomenon in Ruthenium based Dye Sensitized Solar Cells

2017

Dye Sensitized Solar Cells (DSSCs) are widely considered one of the most promising third generation photovoltaic devices, especially thanks to their relatively low cost if compared to conventional solar cells. An interesting phenomenon affecting such devices is the so-called light soaking effect, consisting in the increase of cell main electrical parameters after the exposition to solar light. In this work, starting from the experimental characterization carried out on Ruthenium-based DSSCs, we report on a series of numerical analysis performed to better describe the above-mentioned light soaking effect in order to show the relationship between such phenomenon and the main physical paramete…

Multimodal nonlinear imaging of suspended carbon nanotubes using circular polarizations

2013

In this work, multimodal nonlinear microscopy of suspended CNTs using circular polarizations (CP) was reported. Significant variations in the SHG and THG signals of the CNTs between left hand circular polarization (LHCP) and right hand circular polarization (RHCP) were observed. The variations in the nonlinear signals can be associated to the unique properties of the CNTs such as chirality.