With thin disk laser under intensive pumping high heat flux go through the bonding area with voids inside it will introduce local temperature and stress increase in high-reflective(HR) coating above bonding layer. This will influence the laser damage threshold(LDTH) of local HR coating. An analytical model is developed to analyze the HR coating of thin disk laser illuminated by high fluence pulse laser considering crystal pumping and void inside bonding layer. Analytical results show that the area of HR coating is stressed and heated under crystal pumping. When illuminated by high fluence pulse laser the coating at this area has higher thermal stress. With pump density of 5kW/cm<sup>2</sup> if the radius of the void is larger than 100um the LDTH of HR coating will be affected by the void significantly. And the larger the void size is the lower the LDTH of HR coating is. Relative lower laser damage threshold of HR coating above bonding void is testified by experiment.
A SESAM mode-locked Yb:YAG thin disk laser was designed and analyzed based on the conjugated dual parabolic mirrors multi-pass pumping scheme. In the experiment, 3.6W mode-locked pulses were obtained at the repetition rate of 38.3MHz with a 5% transmission output coupler at 1030 nm. And the phenomenon of double pulses and chaotic-QML were observed in the high pumping power. Moreover, it was found that the pumping power range of the CW modelocking was very narrow in our experiment.
An numerical model considering solder viscoplasticity is developed to analyze the thermal deformation of laser disk with indium bonded. The characteristic of soft bonding material is described using Anand viscoplasticity model. The Finite Element Method analytical results show that the back surface of laser disk with pumping will deform more significantly with time and finally be steady. Correspondingly the refraction power increase gradually and diffraction loss induced by aspherical aberration decrease gradually. Futhermore when pump spot is larger the refraction power and aspherical aberration will change more due to solder viscoplasticity.
In this paper, a thin disk multi-pass amplification system is designed based on the conjugated double parabolic mirror pumping thin disk laser module, which realizes 20 passes transmitting through the thin disk crystal. The light transmission matrix is used to optimize optical mode matching of seed laser spot size and pumping spot size during the multi-pass transmission. At the same time, anti-misalignment stability of the thin disk multi-pass amplification system and the aberration of output laser beam are analyzed in deeply.
Fiber cladding mode stripper is one of key devices in high-power fiber lasers and high-power transmission fiber. We report a new kind of mode stripper using quartz tubes with etched dots on the surface. We studied the waveguide property of the mode stripper both the dots on the outer surface and on the inner surface of the tube. Then we produced some quartz tubes using green laser for the experiments, which demonstrated that the new model strippers can reduce the cladding light and improve the axial temperature distribution obviously.
We present a laser beam shaper designed to obtain a homogeneous line beam. A beam shaping system was designed based on cutting and rearranging optics, using two groups of plane parallel plates. The analysis of beam uniformity was performed by use of ray tracing simulation through ZEMAX software and experimental validation. The simulation results show that in the focal plane, a beam width of 1 mm (@95%Imax) and a uniformity of 90.2% are achieved in one direction, and a Gaussian profile with a beam width of 0.06 mm (FWHM) is achieved in the other direction.
A model of deicing with Nd:YAG and CO2 lasers for simulation using ANSYS software is presented. Experiments with a 300-W, 1-ms, 60-Hz Nd:YAG laser and a 500- to 2000-W cw CO2 laser are reported. The Nd:YAG laser is considered as a volume thermal source, and the CO2 laser as a plane thermal source. The model and the simulation results can describe both Nd:YAG and CO2 laser deicing well. The results of the simulation and experiments suggest that the melting rates for the two lasers are almost equal at the same laser power density. So are the melting efficiencies. The hard and transparent ice irradiated by the Nd:YAG laser becomes opaque and loose, because the thermal stress is distributed in the body of the ice, while the ice irradiated by the CO2 laser is still transparent and hard, because thermal stress hardly occurs. So the laser with characteristics of high output power and large ice absorbing length can be selected for the power line laser deicing system, and Nd:YAG laser is more appropriate for power-line deicing than CO2 laser.
Based on the theoretical model of uniform pulsed laser beam irradiating on the optical material, the stress
distribution of the transparent material when laser with different beam spatial distribution - circle beam spot and
dark-cross beam spot - irradiated to the inner of optical material was discussed.
The experiment that 532nm Q-switched laser pulse was focused to the inner of silicate glass was taken, which the
beam spatial distribution of the output laser was dark-cross beam spot. According to the theory, the experimental results
and phenomena were analyzed and the damage micro-configurations were explained. The theory and experiment could
be accordant well.
Development of precision micro-fabrication techniques for transparent materials such as crystal quartz, sapphire, silica glass is strongly desired in various industrial. During laser ablation the quality of micro-fabrication depends strongly on the optical breakdown region induced by laser irradiation. In this work, nanosecond ultraviolet laser can be used to micro-process on the surface of silica glass and microcrystal glass in air. The experiments demonstrate that number of laser pulse, scanning velocity, laser wavelength and absorption index of these materials are important factors affecting quality of micro-fabrication using ultraviolet laser.
Femtosecond laser is suitable to machine a variety of materials, such as metals, semiconductors, polymers, oxide ceramics, silica aerogels, optical glasses, crystals, deep sea sands and even explosives because of its high peak power density and low heat affected zone. In this paper, the femtosecond laser micromachining of different materials and for different processing is presented, including structuring in optical glasses, and the cutting of metals and the deep-sea (South China Sea) sands. The laser used in the experiment is a commercial Ti:Sapphire laser with the pulse width of 50 and 100 fs, wavelength of 800 nm, maximum pulse energy up to 2 mJ and the repetition rate of 1 kHz. The evolution of material eruption as a function of the number of laser pulses and intensity is studied. The dependence of ablation rate with laser intensity and the number of the pulses is characterized by measuring the maximum laser penetration depth in different materials.
Liquid water acts as an important role in laser processing. Water can be added on purpose gain better result: to avoid redeposition of debris, to cool the material, to increase plasma pressure or to conduct light. On the other hand water is the most common, cheap and safe medium and has an exceptionally high heat capacity. So many researches have been carried out in water-assisted laser processing. In this article, UV laser (wavelength: 355nm, pulse width: 10ns THG Nd:YAG laser) assisted processing of ceramics in air and in water is studied and compared with the processing quality in different environment.
In airborne laser bathymetry, it is very important that narrow band interference filter matches with central wavelength of Q-switched, frequency-doubled laser. A method of fast match of filter and laser central wavelength is described. The results of airborne laser bathymetry system experiments in the pool is gained under the state of match of interference filter with laser central wavelength.
An experimental airborne laser bathymetry system has been developed and field trial has been conducted. The Q-switched and frequency-doubled Nd:YAG laser output is of 100 HZ pulse repetition rate, 2 MW peak power, 8 ns pulse width. The green light receiving telescope is transmissive with 1400 mm focal length and 200 mm aperture. The varying-gain control of PMT and logarithmic amplifier are used to compress the 10<SUP>5</SUP> dynamic range of received signals. The main features of data real-time processing subsystem are of 200 Ms/s sampling rate, 8 bit resolution, adjacent average treatment of return waveforms with high noise, and pseudo-color display of sea depth.
According the wave model on the water surface, the returned laser power expression for the airborne laser bathymetry is derived from. The influence of the wavy water surface, the field of view for the IR received system on returned laser power is discussed.
In this paper, investigations have been made on a CO<SUB>2</SUB> laser with the quasi-tube-plate discharge electrodes under a new gas flow condition. A theoretical model for calculating the stable operation parameter of the new laser was present. A preliminary calculation on small signal gain under many operation conditions has been made. A stable discharge with the input power density of 20 W/cm<SUP>3</SUP> had been obtained in the experiment.
An experimental airborne laser fish finder has been developed and field trial has been conducted. The Q-switched and frequency-doubled Nd:YAG laser output is of 100 HZ pulse repetition rate, 2 MW peak power, 8 ns pulse width. The green light receiving telescope is transmissive with 1400 mm focal length and 200 mm aperture. The varying-gain control of PMT and logarithmic amplifier are used to compress the 10<SUP>5</SUP> dynamic range of received signals. The main features of data real-time processing subsystem are of 200 Ms/s sampling rate, 8 bit resolution, adjacent average treatment of return waveforms with high noise, and pseudo-color display of water depth.