In order to study the effects of the temperature changes on 980 nm vertical cavity surface emitting laser (VCSEL) output characteristics,power-current (P-I) curves of 980 nm VCSEL under two temperature conditions (365 K and 400 K) were simulated,characteristic temperature of this device was calculated. The effects of thetemperature changes on output characteristic were analyzed according to the experimental results,which authenticated the theoretical calculation result.

Based on two-dimensional model,theoretical analysis and numerical simulation were focused on the thermal effect of bi-directionally end-pumped double-clad planar waveguide lasers. Factors which could impact the thermal stress of double-clad planar waveguide laser medium were researched.

The thermodynamic model of side pumped slab laser was established. By numerical simulation,the temperature and the thermal stress of kW-class side pumped Nd:YAG slab laser was obtained. These results were analyzed. In the condition of 3890 watts′s average pump power,the average output power of side pumped Nd:YAG slab laser was achieved to 1012 watts,with slop efficiency of 31% and optical to optical efficiency of 26%. The temperature of slab′s side was measured and accorded well with the simulating results.

This paper reports the development of our recent work on an all-fiberized high power linearly polarized pulsed Yb fiber laser and using the fiber laser to pump a PPMgLN-based optical parametric oscillator (OPO). The pulsed fiber laser used a fiberized acousto-optic (AO) Q-switched Yb doped fiber laser as a seed and a large mode area double cladding polarization-maintaining fiber as the gain medium. It delivered a linearly polarized pulsed laser output working at 1064.2 nm with an average power of 23.5 W at a repetition rate of 40 kHz. The polarization extinction ratio (PER) of the emission was better than 10 dB. The pulse duration was about 46 ns and the beam quality factor (M2) was about 1.3. Using this all-fiberized laser as a pump source to pump a PPMgLN-based OPO,we obtained a maximum parametric output power of 11.05 W at signal wavelength of 1602 nm with 3.01 W of idler power at 3168 nm. The total conversion efficiency and the slope efficiency was 56% and 63% respectively. At signal wavelength of 1508 nm,a maximum parametric output power of 9.87 W was obtained with 2.75 W idler power at 3614 nm.

In high power Nd:YAG laser,because of some pump energy transforming to heat and accumulating in laser media,and inhomogeneous cooling,which leads to the destribution of temperature in media nouniform. Furthermore the grads of temperature lead to heat effect,such as stress birefringence,thermal lens. In this paper the stress birefringence in the media is calculated when the media is under the condition of given destribution of temperature and stress;the loss of thermal depolarization is calculated when polarization light propagates though this media. The results of calculations are consistent with the experiment. Summarizing a simple method of numerical calculating stress birefringence,and developing relevant MATLAB program,which prodives reference for weakening stress birefringence and compensating the loss of thermal depolarization.

In order to study the key problems of rep-rated high power laser-diode-pumed Yb:YAG laser,a 10 Hz joule-class V-shaped water-cooled Yb:YAG oscillator with active mirror(AM) configuration is demonstrated. An efficient hollow duct coupling system for 12 kW LD was designed and the coupling efficiency is 90%. 3.3 J /10 Hz output energy with 27.5% optical-optical efficiency has been achieved in free running regime,which shows that the thermal effects within the Yb:YAG crystal are well managed by the cooling system of the laser head compared with 4.4 J /1 Hz output energy. The experimental results about two kinds of pumping architectures show that the front-pumped architecture is less effective to decrease the average temperature and its gradient within the gain medium than the rear-pumped architecture which accords basically with our prediction,but the front-pumped is more efficient and has no dichromatic coating′ issues which are helpful to be implemented easily.

By solving heat conduction equation,the distribution of temperature field in laser crystal and the thermal distortion of laser crystal pumped-end were investigated,when the crystal with circular cross-section was end-pumped by laser diode. Analyzing the working environment,the more practical thermal model of laser crystal was built. The analytical expressions of temperature field and thermal distortion were obtained. Through numerical calculation,the influence of heat conduction conditions of crystal ends on temperature field and thermal distortion were studied. It was found that the widely used adiabatic conditions on laser crystal ends are not practical,and the proposed heat conduction conditions in the paper are more accurate. The results show that when parameter σ equals 0,0.6 or ∞,the maximum temperature rise in crystal is 165.2,135.7 or 40.1 ℃,and the maximum thermal distortion of crystal pumped-end is 0.66,0.55 or 0.22 μm,respectively.

According to the Sellmeier dispersion equation and law of energy conservation and momentum conservation,the tuning characteristics,conversion efficiency,permitted parametric and walk-off effect of ZGP-DFG have been obtained using numerical simulation in type-Ⅰ and type-Ⅱ phase-matched. The ranges of angle tuning were 51°-89° in type-Ⅰ,and 58°-88° in type-Ⅱ. The corresponding ranges of wavelength were 3.1-12 μm and 6.2-11.5 μm,respectively. In addition,the corresponding characteristics of AgGaS2 (AGS) and AgGaSe2 (AGSe) were compared with ZGP,and the conclusion was the walk-off effect of ZGP-DFG was small,and the conversion efficiency of ZGP-DFG was the highest among the three crystals. In summary,ZGP was a better crystal to produce the mid-infrared laser.

Pumped with Xe-flashlamp will induce non-uniformity rising of temperature in the Nd:glass and brought wave-front distortion with low space frequency,which is the main aberration source of the amplifier. So the wave-front distortion of the assembled slab amplifier with 400 mm aperture is studied in this text. The calculating results indicate that,with presently pumping configuration,the temperature rise of the Nd:glass is about 0.85 ℃,the non-uniformity temperature distributing induced “S” shape distortion is about 1.7×10-6 m,and the thermal-stress is about 65 kPa,the total wave-front distortion is about 0.3λ,which matched the experiment value of the Lawrence Livermore National Laboratory (LLNL). With presently pumping configuration,pump-induced wave-front distortion is acceptable.

A simple dispersion-compensation-free high power mode-locked femtosecond fiber laser with free output coupler is demonstrated. A segment of ytterbium(Yb)-doped double cladding large-mode-area photonic crystal fiber is explored as gain media of the laser. One end-face of the fiber is polished to 0° providing 4% feedback serves as a cavity mirror and a free output coupler. Stable mode-locking is obtained by using a high modulation semiconductor saturable absorber mirror(SESAM). The laser system generates 2.5 W,2 ps,44 nJ pulses that can be dechirped to 430 fs duration outside the cavity.

In order to investigate threshold phenomena of laser induced periodic surface structures (LIPSSs),experimental study was carried out of energy density threshold and pulse number threshold of laser induced periodic surface structures on bulk copper,aluminum,and silver samples under different experimental parameters. The laser energy accumulation effect was then explored to explain the evolutions and threshold phenomena of laser-induced surface periodic structures. In addition,based on the laser energy accumulation and the assumption of Gaussian energy distribution of pulsed laser,scanning velocity,distance of two adjacent scan lines and pulsed laser energy density were optimized in order to fabricate high-uniform and large-area period surface structures,which were in good agreement with present experimental results.

Firstly studied the deep trap state of typical polymeric material using optical parametric oscillator (OPO) as an exciting source by the method of photo-stimulated discharge (PSD). The wavelength of output laser is tunable continuously in the range of 210-420 nm and the mean energy of photo-impulse which has a width of 3-5 ns is about 2.3 mJ. The experimental results show that this laser source can be well implemented in the PSD measurement. For example,the activation energy of the polyethylene terephthalate (PET) is 4.27 eV and the activation energy exists on polypropylene (PP) is 4.92 eV and 5.17 eV which all belong to the deep trap. The activation energy is the essential parameter to characterize the polymeric dielectric material which can provide fundamental data and scientific reference for the improvement to enhance the electric properties of the material.

The beam automatic alignment system is used to adjust the beam of high power solid-state laser driver and to make the beam accurately point to target. Algorithm of alignment and flow control are two key techniques on beam automatic alignment. Considering the algorithm on alignment of cavity mirror in technical integration experiment line (TIL),three kinds of algorithms:the largest area of image signal,control of long-short axes and the length of x-y axes control are put forward based on image processing. The experiment on TIL indicates that the length of x-y axes control is propitious to closed-loop control of alignment,and the alignment accuracy is less than 90 μm. After wave-front adjusting,alignment system is used to point the far-field again. Result indicates that the influence of the adaptive optics system which makes the far-field alignment error will be able to eliminate.

Lasers with high stability of frequency are required on ultra-cold atom experiment. A compact frequency stabilization system of diode laser is proposed,which is based on the principle of saturated absorption of atom vapor. The generation,amplification,filtering,mixing of radio frequency (RF) modulation signal,as well as the error signal detection,are integrated into a 3U plug-in module. The scan circuit for finding the spectroscopy and PI controller for frequency locking are also integrated into another 3U plug-in module. For holding those modules,a 3U rack of 14-slot and 19 inches (482.6 mm) width is designed. Experiments show that the high level of integration means not only take up less space,easy to manage and maintain,but its anti-interference ability also greatly enhanced. In order to detect the faster phase jitter of the laser diode,and to avoid the noisy low frequency,a modulation frequency as high as 21.4 MHz is adopted.

High power semiconductor laser arrays have found increasing applications in pumping of solid state laser systems. Spectral width is one of the key factors of laser array products. Increasing the spectral accuracy by reducing the spectral width of the pump diode can improve the laser system compactness,efficiency,power,and beam quality while reducing thermal management cost in the system. The mechanisms of spectral broadening in high power semiconductor laser arrays are studied for the first time by numerical simulation and by means of spatial spectral mapping and scan acoustic microscope(SAM). The broadening of a laser spectrum is often the result of the appearance of a shoulder/tail on either or both sides of the spectrum or sometimes a double-peak or even multiple peaks occurs. It is concluded that the shoulder/tail appeared on the longer-wavelength side of the spectrum is normally caused by thermal effect while the shoulder/tail on the shorter-wavelength side of the spectrum is usually the result of thermal-stress built in the laser array. Based on the mechanism of spectral broadening in high power semiconductor laser arrays,the strategy of controlling spectral broadening is presented in this paper.

With a 1.06 μm solid Nd:glass nanosecond pulse laser and a bell-shaped thruster made of K9 glass,both vertical single-pulse propulsion experiment and the corresponding numerical simulation are studied. The results show that,the focal length dominates among the structural factors of thruster in the propulsion by nanosecond pulse laser. The larger focal length corresponds to a better propulsion performance,and at the same focal length,the thruster with smaller open angle and longer scale can achieve higher impulse coupling coefficient,which are different from the results achieved in the propulsion by a microsecond pulse CO2 laser. It is believed that the reason for the poor performance of thruster with shorter focal length is the thermal damage of thruster caused by ultrashort pulse laser. The 12.5 g thruster is vertically propelled for a height of 24.5 mm by a 18 J single pulse laser,and its impulse coupling coefficient is 478.75 μNDK·sDK·J-1. By comparing with the experimental results based on the CO2 laser,the nanosecond pulse laser is better than the microsecond pulse laser in the single pulse propulsion.

Resonator micro optic gyroscope (RMOG) is a novel optical rotation sensor whose resonant frequency is changed due to the Sagnac effect. Optical ring resonator is the key sensing element in RMOG. Using one-point reflection to simplify the distributed backscattering phenomenon in the resonator,combining the overlapping method of multiple beams,backscattering spectrum is theoretically formulated. On this basis,when the laser frequency is swept linearly to time,the resonance curve and the backscattering curve are measured on the polarization maintaining silica optical ring resonator. The backscattering coefficient is successfully obtained. Simulation shows that the experiments fit well with those obtained theoretically. It will supply the theoretical support to make research on the backscattering induced noise in RMOG.

The terahertz (THz) emission properties of two kinds of small-aperture photoconductive antennas are studied under the condition of different spot area of pump laser. The characteristic of THz radiation generated by them is compared. Meanwhile,it also provides a reference to investigate and fabricate the high efficient of THz radiation source. The emission spectra of the photoconductive antenna are obtained by THz time domain spectroscopy (TDS) technology. The corresponding frequency domain spectra are obtained by fast Fourier transform (FFT). The results show that when the bias voltage is enhanced or the spot area of pump laser becomes smaller,the peak value of THz radiation is increased and saturated with increasing of pump power. Under the same bias voltage,the spot area of pump laser and the pump power,the properties of THz radiation generated by two kinds of photoconductive antennas are compared. The results show that,the full width of half maximum (FWHM) of THz frequency domain spectra which is generated by the small-aperture bow-tie photoconductor antenna is broader and the intensity of THz radiation is larger.

Using water as coolant,experiments were used to study the spray cooling of 200 W/cm2 high power solid state laser for the heat dissipation. The heat transfer performance of spray cooling in the non-boiling regime was studied for volumetric flux ranged from 0.044 to 0.053 m3 /(m2·s) and the temperature ranged from 25-65 ℃. It was found that when the wall temperature was 65 ℃ and volumetric flux was 0.044 m3 /(m2·s),the heat flux dissipated could reach 257 W/cm2;when the volumetric flux increased to 0.053 m3 /(m2·s),the heat flux could reach 300 W/cm2 on the condition of the same surface temperature. Through analysis of experiments data,it was found that as the volumetric flux,wall temperature increasing,the heat transfer coefficient increased gradually. Further more,an empirical correlation between average Nusselt number Nu and the spray Reynolds number (Re>440) was developed. Compared with the data of Oliphant et al.,it was observed that the results from the correlation when Re is more than 240 could be of reference in the engineering application.

The Raman spectra of Dangshen medicinal materials are tested in different positions. The normal Raman spectrum and surface-enhanced Raman spectrum (SERS) of Dangshen decoction are tested and analyzed .The intensity of the SERS of Dangshen decoction in the silver colloid is increased obviously. The characteristic Raman bands of Dangshen decoction were tentatively assigned. The absorption spectroscopy of Dangshen decoction and the mixture of silver colloids and Dangshen decoction are measured. A new resonance absorption peak was observed in the long-wavelength region in UV-Vis absorption spectra of the mixture. The adsorption characteristics and possible enhancing mechanism of the Dangshen decoction on silver colloid were speculated. The results show that the surface-enhanced Raman spectroscopy might provide a new kind of precise,direct and fast detecting method for the detection of Dangshen decoction or other Traditional Chinese medicine.

Temperature gradient is one of the most important factors which cause large deformation on large aperture optical element in inertial confinement fusion (ICF) drivers. In this paper,the ambient temperature around the switchyard was measured and the temperature distributing and changing characteristic with time was analyzed,which indicate that temperature changing trend inside of the switchyard is identical,and the temperature gradients of the uppermost part are higher than the bottom,and the temperatures of middle part are higher than the both sides. Loading the temperature on the finite element model of switchyard,gets the deformation of the optical element changing with time. The results indicate that temperature distribution has a great impact on the optical element,the change of mirrors can meet the request of target experiment when the switchyard has about 0.01 ℃ difference in temperature or about 0.1 ℃ partial difference in temperature.

Liquid flow has positive implication for the thermal management in liquid lasers. The flowing state of liquid can considerably influence the laser beam quality. By the aid of the commercial software Fluent,the transverse flowing states of liquid media in gain area are simulated. Based on the wave-front curving sensing technology and the Green′s functions wave-front reconstruction arithmetic,the phase distribution of the probe laser (He-Ne laser) is measured when the flow rates are 0.48,1.51 and 5.39 L/min. The Strehl ratios are 0.9964,0.9960 and 0.9936,respectively. The results show that when the flow rate is stable,the laser beam quality is almost not affected by the liquid flowing state. Under the longitude uniform pumping circumstances,the laser beam quality in viscous flowing state is slightly reduced compared to that in uniform flowing state. When the pumping power density is 46.9 W/cm2,the Strehl ratios are 0.9484 and 0.9995,in which the flow rates are 0.48 and 5.39 L/min. The Strehl ratio decrease to 0.1051 and 0.9978,when the pumping power density increases to 100 W/cm2 and the flow rate keeps the same. The wave-front aberration arising out of the heterogeneity of the flow rate can be decreased by promoting the flow rate of the liquid media.

By replacing the first 3 dB coupler with a phase generating coupler (PGC) in the conventional Mach-Zehneder interferometer (MZI) electro-optic switch,a novel improved switch is designed. The structural model is presented,and the principle is described. The expressions of the amplitude transfer matrices are derived,and the compensating principle of the phase shift and the switching condition are analyzed. The parameters are optimized,and the characteristics are simulated,involving the propagation power,output power,output spectrum,insertion loss and crosstalk. Simulation results for the designed device show that,the push-pull switching voltage is 2.445 V,the switching time is 18.1 ps,the pass-band of the output spectrum can be increased to 110 nm,and the insertion loss and crosstalk are less than 2.24 dB and -30 dB,respectively,within the wavelength range from 1492 to 1602 nm. Our simulation results agree well with those of the Optiwave software based on the beam propagation method (BPM).

A method to eliminate the damage aroused by intrinsic prepulse of Blumlein transmission line is proposed. It is used as the forming line in the experiment of capillary discharge soft-X-ray laser,and an additional prepulse is loaded successfully. Ne-like Ar 46.9 nm soft-X-ray laser whose spectra detected by a Rowland spectrograph is obtained. We also detected the directionality,divergence and the gain characteristics of Ne-like Ar 46.9 nm soft-X-ray laser. With the help of Blumlein transmission line,the service efficiency of Marx generator is increased,which is helpful to achieving miniaturization of capillary discharge soft-X-ray. Finally,the supposed applications of 46.9 nm soft-X-ray are also discussed in this paper.

The paper briefly introduces the development of rapid prototyping technology and two main methods of laser direct manufacturing of metallic parts,further gives the latest advance and the development trend of laser direct manufacturing of metallic parts.