Narrowband, mid-infrared, seeded optical parametric generator based on non-critical CdSiP2 pumped by 120-ps, single longitudinal mode 1,064 nm pulses

In this work, we present low-threshold, efficient optical parametric generation in CdSiP₂ pumping at 1,064 nm with 120-ps-long, single longitudinal and transverse mode pulses at 230-kHz repetition rate provided by a microchip passively Q-switched master-oscillator power amplifier laser system. Seeding at the signal wavelength with a laser diode, we generated bandwidth-limited idler pulses at 6,100 nm.     

Widely and continuously tunable optical parametric generator based on MgO-doped periodically poled LiNbO_3 crystal

A widely and continuously tunable optical parametric generator (OPG) pumped by a 1064-nm acousto-optically Q-switched diode-end-pumped Nd:YAG laser based on MgO-doped periodically poled LiNbO3 crystal with a multigrating structure (29.2-30.4μm) is reported. A broad continuous signal spectrum of 1513-1700 nm is obtained by changing the crystal grating periods from 29.2 to 30.4μm and by tuning the crystal temperature from 30 to 180℃simultaneously. When the average pump power is 1.82 W with pulse duration of about 70 ns operating at a repetition rate of 10 kHz, the maximum signal output power of the periodically poled MgO-doped lithium niobate (PPMgLN) OPG is about 210 mW corresponding to the idler and total powers of 118.4 and 328.4 mW respectively.     

Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3

We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485－1553nm signal wave and 3383－3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal.     

1-W, high-repetition-rate room temperature operation of mid-infrared optical parametric oscillator based on periodically poled MgO-doped LiNbO

In this paper a high-repetition-rate mid-infrared （mid-IR） optical parametric oscillator based on periodically poled MgO-doped LiNbO3 （PPMgLN） at room temperature was demonstrated. The maximum average mid-IR output power at 3.63μm was 1.02 W with the repetition rate of 60kHz and corresponding efficiency from the pump to the idler was 26.7%. The temperature tuning and the period tuning characteristics were also discussed.     

High-Power,high-repetition-rate operation of a period-continuously-tunable optical parametric oscillator at 3.78–4.62 μm based on a fan-out periodically poled MgO-doped lithium niobate

We present a period-continuously-tunable optical parametric oscillator based on a fan-out MgO:PPLN with a grating period range from 26.9 to 29.5 μm. The OPO was pumped by a Q-switched Nd:YAG laser with a repetition of 10 kHz. With a grating period of 29.3 μm and 22.0 W pump power, the idler output power at 3.78 μm arrived at 3.40 W. With a period of 27.1 μm and 13.5 W pump, the idler output at 4.58 μm arrived at 0.36 W. This is, to our best knowledge, the highest average power for pulsed OPO operating near 4.5 μm based on PPLN or MgO:PPLN. By translating the fan-out MgO:PPLN, the idler wavelength was tuned continuously from 3.78 to 4.62 μm.     

Megawatt peak power, 1 kHz, 266 nm sub nanosecond laser source based on single-crystal fiber amplifier

We report the realization of a UV source based on the fourth harmonic generation with LBO/BBO of a Nd:YAG passively Q-switched oscillator amplified in a single-crystal fiber. With careful optimization of the nonlinear components and parameters, we obtain 530 mW average power at 266 nm with pulses of 540 ps at the repetition rate of 1 kHz, which represents a 22.7 % total conversion efficiency from IR to UV and nearly 1 MW peak power. The beam quality M ² is measured to be below 2.     

Efficient light source based on an inductive ferrite-free discharge at frequencies of 300–3000 kHz

Glass cylindrical tubes from 30 to 50 cm long and from 5 to 7 cm in diameter are used to initiate an inductive discharge in electrodeless luminescent lamps at frequencies of 300–3000 kHz with a power of 50–300 W. The tubes are filled with mercury vapor and an inert gas (argon at a pressure of 0.1 mm Hg), and their inner surface is covered by a phosphor and protective coating. An induction coil (from 5 to 14 turns) made of a low-resistivity multiple-conductor cable embraces the discharge tube in the longitudinal direction, forming a discharge-initiating loop. Because of a high Q factor of the coil, Q _c = 400, the power losses in it are 4–5 W at frequencies higher than 400 kHz; the energy efficiency of the lamp is η = 0.95–0.96. Luminous efficiency ? of the lamp grows with discharge excitation frequency, reaching ? = 83–84 lm/W at a frequency of 530 kHz and a power of 150 W.     

Wavelength modulation spectroscopy at 1530.32 nm for measurements of acetylene based on Fabry–Perot tunable filter

Sensitive detection of acetylene(C_2H_2) is performed by absorption spectroscopy and wavelength modulation spectroscopy(WMS) based on Fiber Fabry–Perot tunable filter(FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating(FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv–400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C_2H_2 detection can be applied in practical applications.     

High efficiency,high power QCW diode-side-pumped Nd：YAG ceramic laser at 1064 nm based on domestic ceramic

A high efficiency, high power diode-side-pumped quasi continuous wave （QCW） Nd：YAG ceramic rod laser at 1064 nm based on the domestic transparent ceramic is reported. The average output power of 961 W is achieved with double ceramic rods by means of a symmetrical convex-convex cavity. The optical-to-optical conversion efficiency is 38.3% and the slope efficiency is 45.3%. To the best of our knowledge, this is the highest level of efficiency achieved for the domestic Nd：YAG ceramic rod laser.     

High-efficiency clean EUV plasma source at 10–30 nm, driven by a long-pulse-width excimer laser

A long-pulse-width high-output energy (120 ns FWHM, 7 J) XeCl laser has been focused on thin tape targets (Cu and Ta) to generate more than 100-ns-long (FWHM) EUV pulses in the 10–30 nm spectral region, suitable for projection microlithography. The conversion efficiency was more than 20% over a 2π solid angle. We observed debris emission using a gated CCD camera, and measured the debris speed for different irradiation conditions. We found irradiation conditions such that the measured velocities were low enough that simple mechanical devices combined with krypton at low-pressure could efficiently stop both ionic debris and cluster debris. Our results show that a suitable combination of driving-laser characteristics, target material and thickness, environment gas and mechanical choppers can make clean and increase the power of EUV solid-target laser-plasma sources. Received: 21 October 2002 / Published online: 26 February 2003 RID="*" ID="*"Corresponding author. Fax: +39-06/9400-5334, E-mail: bollanti@frascati.enea.it     

Narrow-bandwidth, mid-infrared, seeded optical parametric generation in 90° phase-matched CdSiP₂ crystal pumped by diffraction limited 500 ps pulses at 1064 nm

Low-threshold, efficient optical parametric generation at ～6100 nm is demonstrated using CdSiP₂ nonlinear crystal at 1 to 10?kHz repetition rates with relatively long 500?ps pump pulses at 1064?nm. Maximum single pulse energy of 8.7?μJ and average power of 79?mW are achieved for the idler. Seeding at the signal wavelength is employed using a distributed feedback laser diode, which enables approximately tenfold narrowing of the idler bandwidth down to less than 1?nm.     

Analysis of pulsed discharge characteristics of solid-state switch (IGBT) based 16?kHz repetition rate, 100?W average power copper–HBr lasers

We present for the first time a comprehensive analysis (both time resolved and time averaged) of the gas-discharge characteristics of a solid-state switch (IGBT) based on high average power (100?W class), high pulse repetition rate (16?kHz) copper?CHBr laser under various excitation conditions. We evaluate various discharge-plasma parameters such as the electrical inductance, electrical resistance, active laser-head voltage, active electrical power, pre-pulse electron density, and axial gas temperature by numerical processing of the measured laser head voltage?Ccurrent waveforms. For the first time, we evaluate fractional losses at various intermediate stages of the circuit elements as well as effective coupling for the laser excitation process during transfer of energy from the wall plug to the laser-discharge plasma. We conclude that irrespective of the capacitive storage input power (P _in), a constant fraction of ~40% of P _in is coupled into the laser-discharge plasma. With a low to moderate specific input power of 0.4?C0.7?kW/?, the tube produced 70?C110?W average output power at an efficiency of????3.2?C2.8%, respectively. The average laser performances at various P _in are correlated to its time-resolved and average gas-discharge parameters such as the inter-pulse electron density and axial gas temperature.     

Energy harvesting using multilayer structure based on 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 single crystal

In this paper we fabricated the multilayer structure used as the resonance-based vibration energy-harvesting device based on 0.71Pb(Mg_1/3Nb_2/3)O₃–0.29PbTiO₃ single crystal. The performances of the device including the output voltage and power were studied systematically. Under a cyclic force of 4 N (peak value), a high output power of 4.94 mW and a corresponding peak voltage of 3.14 V were measured at 1.4 kHz with a matching load resistance of 1.0 kΩ. The results demonstrate the potential of the device in energy-harvesting applied to low-power portable electronics and wireless sensors.     

The calculation of active Raman modes of α-quartz crystal via density functional theory based on B3LYP Hamiltonian in 6–311+G(2d) basis set?

We obtained an approximation of the force field of ??-quartz crystal using a new idea of applying density functional theory [J Purton, R Jones, C R A Catlow and M Leslie, Phys. Chem. Minerals 19, 392 (1993)]. Our calculations were based on B3LYP Hamiltonian [A N Lazarev and A P Mirgorodsky, Phys. Chem. Minerals 18, 231 (1991)] in 6?311+G(2d) basis set for H₁₆Si₇O₆ cluster and included a unit cell of the lattice. The advantage of our method is the increase in the speed of calculations and the better adaption of simulation results with the experimental data.     

Dielectric spectroscopy of PbZr1 ? xTixO3 solid solutions (0.495 ≤ x ≤ 0.51) in a temperature range of 100–300 K at frequencies from 1 × 10?2 to 2 × 107 Hz

The behavior of the relative permittivity ɛ/ɛ₀ of PbZr_{1 − x} Ti _x O₃ (PZT) solid solutions (0.495 ≤ x ≤ 0.51) in the temperature range of 100–300 K at frequencies from 1 × 10⁻² to 2 × 10⁷ Hz was investigated. Diffuse, strongly relaxing maxima at T = 230−260 K (x = 0.495−0.505) and 150–160 K (x = 0.510) were observed in the PZT studied. The relaxation processes are well described by the Vogel-Fulcher law, and the dielectric spectra are approximated by the Cole-Cole formula.     

Effect of excess oxygen on the electrical and magnetic properties of La1 ? xAgxMnO3 (x = 0.05, 0.1, 0.2) at 77 K < T < 300 K

A study has been made of the magnetic and electrical properties of oxygen-enriched La_{1 − x} Ag _x MnO_3.1 manganites at 77 K < T < 300 K. The samples have been produced by the sol-gel technique. The study has revealed an increase of the Curie temperature and a shift of the maximum in magnetoresistance toward high temperatures.     

Resonant scattering of nonequilibrium phonons (<Emphasis Type="Italic">λ</Emphasis><Subscript>ph</Subscript> = 10–50 nm) in nanostructured ceramics based on YSZ + Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Specific features of the transport of weakly nonequilibrium thermal phonons (λ _ph = 10–50 nm) in nanoscale ceramics at a transition from micro-to nanosizes have been investigated. On the basis of the model of spherical shells randomly distributed in space and modeling grain boundaries, whose elastic properties differ from the elastic properties of grains, features of the phonon spectrum in the wavelength range λ _ph ～ R _g have been studied. The conditions leading to the occurrence of a gap in the phonon spectrum of nanoscale materials are analyzed. It is shown that the position of the top gap edge in the phonon spectrum is determined to a large extent by the structure of phase boundaries, while the presence of inclusions (pores, other phases) with characteristic sizes smaller than that of grains of the main ceramic material shifts the gap to high frequencies in the phonon spectrum. Temperature dependences of the diffusion coefficient of nonequilibrium phonons near the top gap edge in the phonon spectrum have been measured for multiphase ceramics based on YSZ + 14.3% Al₂O₃ composites.