Sinterability studies on K0.5Na0.5NbO3 using laser as energy source

The sinterability of K_0.5Na_0.5NbO₃ (KNN) ceramics by a laser beam has been investigated in the present research. A 100 W CO₂ laser with a beam diameter of 0.6 mm has been used to sinter the KNN specimens prepared on a uniaxial pressing machine. The relations between laser power and thickness of densified layer, crystallographic structures and phase compositions have been studied. A comparison has been made between laser and furnace sintered KNN samples according to the SEM, XRD and XRF results. The possibility of KNN used for the layer-wise laser direct sintering 3D components has been confirmed in this paper.     

An injection-locked single-mode tea CO2 laser for SMM laser pumping

A D₂O laser has been developed for collective Thomson scattering measurements of ion temperature in high temperature plasmas. A pulse duration and a spectral width of a high power D₂O laser has been successfully controlled for this purpose, by using a TEA CO₂ laser injection-locked by an etalon-tuned TEA CO₂ laser as a pump source.     

New large offset far-infrared laser lines from CD3OH

The CD₃OH molecule has been investigated for new far-infrared laser lines by optically pumping with a cw waveguide CO₂ laser. The increased tunability (300 MHz) with respect to a conventional CO₂ laser permits to pump many new CD₃OH lines. As a consequence 108 new laser lines have been discovered, ranging from 42.9 to 1155 m in wavelength. On some lines the effect of an electric Stark field has been investigated demonstrating a laser frequency tuning. The total number of known FIR laser lines from CD₃OH is increased to about 340 making this molecule the most prolific together with CH₃OH.     

Pulsed laser deposition of doped skutterudite thin films

Ca_xCo₄Sb₁₂ skutterudite thin films have been prepared by pulsed laser deposition using a Nd:YAG laser working at 532 or 266 nm of wavelength. Characterization has been carried out by X-ray diffraction, atomic force microscopy and scanning electron microscopy. Emphasis has been put on the difficulty to obtain the skutterudite phase. Influence of the deposition temperature, the way of sticking the substrate, the laser fluence, the base pressure prior to deposition and the laser wavelength has been studied. All parameters revealed to have a drastic effect, and the skutterudite could only be achieved in a very narrow range of temperature and laser fluence, for a given wavelength, showing the importance on how these parameters are measured to ensure reproducible results.     

Injection seeding for single-mode operation in an optically pumped high-power D2O laser

Spectrally narrow, pulsed outputs consisting of almost a single mode have been obtained from an optically-pumped high-power (200kW) D₂O laser by adopting the injection seeding method, where single-mode radiation (seed pulse) from a low-power, compact D₂O laser has been injected into the main D₂O laser. Spectrally narrow outputs with high power having spectral widths as narrow as 5 MHz have been obtained, when the seed pulses with frequency tuned to one longitudinal mode of the main D₂O laser have been injected at a time sufficiently before the lasing of the main laser took place. The experimental results have been compared with those of numerical simulation modified to include the injection field with varying injection times.     

Suppression of laser noise in CW 337μm HCN lasers

In a d.c.-discharge-excited 337 μm HCN laser, amplitude laser noise has been observed at the frequency range of 30 kHz to 1 MHz. The laser noise is classified into three types; oscillation noise having sharp peaks, broadly distributed noise having a center frequency and 1/f-noise. Characteristics of the laser noise have been studied experimentally. The laser noise is caused by small oscillation which appears on d.c.-discharge current and by random fluctuations of current and plasma density. The laser noise has been suppressed more than 30 dB by adjusting the laser parameters such as discharge current, pressure and flow rates of mixed gas (CH4₄ + N₂ + He) and added He.     

Doppler-free optoacoustic spectroscopy of O-18 methanol

The Doppler-free optoacoustic spectrum of the oxygen-18 species of methanol has been investigated with a CO₂ laser. Seventeen coincidences have been found between infrared absorptions of CH¹⁸₃OH and CO₂ laser lines. The strongest feature seen, pumped by the 10R(20) CO₂ laser line, has two plausible alternative identifications, determined from a parallel high-resolution spectroscopic study of the C-O stretching band. Further experimental tests are suggested to resolve the assignment, and predicted far-infrared laser frequencies are given for the two possibilities.     

Study on the Spectrum of Miniature Optically Pumped NH3 Submillimeter-Wave Laser

By means of an iteration method and taking into account the broadening of the infrared pumping laser, the spectrum of a miniature, optically pumped, superradiant NH₃ submillimeter-wave(SMMW) gas laser pumped by CO₂-10R(8) has been calculated and studied by solving density matrix equations. Experimentally, the interferogram of miniature SMMW laser pumped by a TEA-CO₂ laser with 10R(8) line is measured. This is the first time that the theoretical spectrum has been in good agreement with experimental results.     

Reflectivity measurements from a nanosecond CO2 laser produced plasma

The back-scattered light from a laser produced plasma has been studied using a nanosecond gigawatt CO₂ laser. The spectral shift and width of the reflected light have been determined as a function of the incident laser energy.     

Microstructural investigation of CaxCo4Sb12 films prepared by pulsed laser deposition

Ca_xCo₄Sb₁₂ skutterudite thin films have been synthesized by pulsed laser deposition from a Nd:YAG laser working at 532 or 355 nm. The influence of deposition temperature, laser fluence and working atmosphere on the structure and morphology of the films has been studied. The characterization has been carried out by X-ray diffraction, atomic force microscopy and scanning electron microscopy. Laser wavelength proved to be the most significant parameter to produce the skutterudite phase. PACS 81.15.Fg; 68.55.Jk; 81.05.Bx     

CO-laser photoacoustic detection of phosgene (COCl2)

Detection of COCl₂, a highly toxic gas in chemical industry, using laser photoacoustic spectroscopy is presented. The spectrophone system used has a broad band LN₂ cooled CW CO laser as a source of radiation, which operates from 4.8–8.4 um in the mid-infrared. Using an extracavity open longitudinal resonant cell, absorption signals to about 30 CO laser lines in the 5.45 um region could be observed. detection sensitivity has been estimated to be ppb order.This work has been supported by the NSFC     

Comparison of theory and experiment in electron-beam-controlled CO2 laser oscillators

A four-temperature model describing the electron-beam-controlled CO₂ pulsed laser has been developed and used to study the time evolution of a laser pulse and the influence thereon of experimental parameters. This paper explains the experimental results of two different electron-beam CO₂ pulsed laser systems which have been built in the laboratories at Frascati.     

射频激励板条波导CO2激光器远场空间压窄单峰输出模式特性的实验研究

报道了射频激励扩散型冷却板条波导CO₂激光器远场呈空间窄单斑分布的模式特性及其模式演化过程的实验现象,实验研究了远场出现压窄单斑时的模式结构.通过实验研究发现实验中所获得的近场呈多点分布和远场呈空间窄单峰分布的板条波导激光器输出模式是一种新的单模频振荡模式. 关键词：     

Broadband and rapid tuning of an all-solid-state single-frequency Nd:YVO4 laser

A diode-pumped tunable single-frequency Nd:YVO₄ laser has been built. The laser incorporates a LiNbO₃ etalon (LE) as a coarse tuning element and a LiNbO₃ crystal (LC) as a fine tuning element to obtain broadband, rapid tuning. More than 480 mW of output power has been obtained from the tunable laser with frequency tuning range of 17.2 GHz and the tuning response time of 10 ns. PACS 42.55.Xi; 42.60.Da; 42.60.Fc; 42.60.Pk     

Resonant interaction of femtosecond radiation with a cloud of cold <Superscript>87</Superscript>Rb atoms

The resonant interaction of ⁸⁷Rb atoms in a magneto-optical trap with femtosecond laser radiation in the spectral range 760–820 nm has been investigated experimentally. It has been demonstrated that femtosecond laser radiation with a spectral width of 10 nm interacts with an atomic ensemble as a set of spectrally narrow modes and as an ionizing laser field simultaneously. The dynamics of trap loading in the presence of ionization by femtosecond radiation has been studied, and the 5D _5/2 level population produced by an additional weak laser field has been measured.     

Dynamical analysis of acousto-optically Q-switched CO2 laser

A compacted size high power CO₂ laser has been developed using an acousto-optically (AO) Q-switch. Performance characteristics have been investigated as a function of output mirror transmittance. The theory of six-temperature model for CO₂ lasers has firstly been utilized to analyze the dynamical process in the AO Q-switched CO₂ laser. This theory perfectly explains the behavior of energy transfer between different molecules in laser gain medium, and describes the shape of pulse laser. The calculated pulse waveforms are in good agreement with the experimental result. Both the experimental and theoretical results present that the optimal value of output mirror transmittance is 39%. Under this condition, the measured peak power is 4750 W and pulsed width is 160 ns, which is consistent with the calculations. Six-temperature model is a perfect theory for CO₂ laser kinetics, which will lay a theoretical foundation for the laser optimum design.     

Effect of acoustic waves on the repetition frequency of high repetition rate TEA-CO2 lasers and calculating optimization condition

The gas channel of a pulse periodic TEA-CO₂ laser is considered as an acoustic resonator. In this paper, a three-dimensional mathematical modeling has been considered for describe of laser action. By calculating of the equations obtained from this model, the effects of cavity dimensions, Mach number and repetition frequency of laser on the acoustic wave spectrum have been investigated. At last optimum conditions for performance of laser operation has been arrived.     

Diffractive scanning mechanism for laser marker

We present a new idea of marking based on spectral properties of CO₂ laser radiation. The idea has been illustrated on RF excited waveguide CO₂ lasers in different configurations: single channel, multi-waveguide and slab-waveguide ones. The pulse operation of the laser has been considered as well. The advantage of the presented diffraction marker is avoiding complicated and fallible mechanical elements. The only executive elements of the marker are a diffraction grating and a piezoceramic transducer. It has been shown that the slab-waveguide configuration of the RF excited CO₂ laser equipped with an unstable resonator is the most promising configuration for application to the diffraction marker.     

CO2 laser assisted removal of UO2 and ThO2 particulates from metal surface

Pulsed laser assisted removal of uranium dioxide and thorium dioxide particulates from stainless steel surface have been studied using a TEA CO₂ laser. Decontamination efficiency is measured as a function of laser fluence and number of pulses. Threshold fluence for the removal of UO₂ particulates has been found to be lower than that required for the removal ThO₂ particulates. Usage of a ZnSe substrate, that is transparent to the laser wavelength used here, enabled us to decouple the cleaning effect arising out of absorption in the particulates from that in the substrate and has contributed towards understanding the mechanism responsible for cleaning. The experimental observations are also corroborated by simple theoretical calculations.     

The use of plane-polarized beams in controlled surface temperature laser heat treating

Plane-polarized CO₂ laser beams can be successfully employed in controlled surface temperature laser heat treating in order to improve the coupling between radiation and steel. The coupling efficiency has been quantitatively determined by means of a simple energy balance model, by using a medium-power CO₂ laser. In this way, the angle at which the best coupling can be obtained has also been singled out. Moreover, some heat treatments performed with a high power laser beam obliquely impinging on medium carbon steel samples have confirmed that controlled surface temperature laser heat treating can be completely free of the problems concerning the use of coatings generally employed.