Yb3+CaF2 laser has been intensively explored in recent years. In Yb3+CaF2 continuous-wave (CW) laser, the highest output power of 10.2 W pumped by a laser diode(LD) of 64 W has been reported in 2008. The first demonstration of the highest output power of 14.5 W in a LD-pumped Yb, NaCaF2 CW laser is presented, under the conditions of an absorbed pump power of 18.2 W and a output coupler of 4%, which corresponds to a laser slope efficiency of 80%. The result shows that the novel Yb, NaCaF2 crystal is an excellent laser material for low-threshold and high-power lasers.

The experimental results of LD pumped monolithic non-planar ring resonator (NPRO) single frequency Nd:YAG laser and LD pumped monolithic bonded crystal NPRO TmYAG laser are proposed. 1064 nm and 1319 nm single frequency lasers with the power up to 1.876 W and 616 mW were obtained from the LD pumped NPRO Nd:YAG lasers, and the optical-optical efficiencies were 53.4% and 19.2%, respectively. The 878 mW single frequency 2 μm laser was generated in the LD pumped monolithic NPRO TmYAG laser, with the optical-optical efficiency of 18.8%. For reducing the influence of heat effect in 2 μm laser, a novel double-bonded YAG+TmYAG+YAG crystal was designed and good results were obtained.

High efficient continuous wave Tm∶YAP laser end-pumped by laser-diode (LD) is presented in this paper. In experiment, fiber-coupled LD at 795 nm is used to pump the Tm∶YAP crystal. The c-cut Tm∶YAP crystal with the dimensions of 3 mm×3 mm×7 mm is doped with the 3% Tm3+ (atomic fraction). Under the input pump power of 26.2 W, the highest output power reaches 8.12 W with 10% transmittance, and the laser threshold is 4.67 W, corresponding to slope efficiency of 52.1% and the optical conversion efficiency of 31.0%. The free running laser spectrum of Tm∶YAP is measured by using a grating monochromator, and the corresponding central wavelength is 1938.2 nm, with full width at half maximum of 2.9 nm.

Considering the reabsorption and thermal lens of Nd:YAG crystal when the laser operates on the transitions at 946 nm, a ring laser cavity formed by four mirrors was designed. Using a Brewster plate as a polarizer, a half-wave-plate and a TGG crystal as the optical diode and PPKTP as the frequency doubling crystal, a laser diode end-pumped 473 nm continuous wave single frequency Nd:YAG laser was demonstrated experimentally. The single frequency output power at 473 nm is 770 mW with pump power of 20 W. The long term power fluctuation is less than ±2.2%. After the laser was locked to the confocal Fabry-Perot cavity resonance, the measured frequency stability of blue laser is better than ±5 MHz/min.

A unique non-planar ring cavity consisting of a thermally bonded Porro prism and a corner cube prism is proposed. 946 nm single-frequency operation is achieved in this cavity by applying the ring permanent magnet to the corner cube prism made of fuse silica. The Porro prism by thermally bonded un-doped YAG with Nd∶YAG crystal acts as the laser gain medium. End-pumped by an optical fiber coupled semiconductor laser with core diameter of 200 μm and numerical aperture of 0.22, the maximum continuous output power of 160 mW at 946 nm is obtained.

An all solid-state continuous-wave cyan laser at 500.8 nm is presented. By using a new resonator for doubly resonant, two Nd∶YAG are pumped by two laser diode arrays (LDA) coupled by optical fibers, respectively. In the two cavities, wavelengths of 1064 nm from one Nd∶YAG and 946 nm from the other are chosen to be mixed into 500.8-nm cyan laser. Through proper design of the cavity, the optimum matching of modes and gains for the two wavelengths can be obtained. In the overlapping of the cavities, sum-frequency mixing is generated with a type I critical phase matching LBO crystal. The cyan laser output of 223 mW at 500.8 nm with TEM00 mode is obtained at the incident pump power of 12 W for one Nd∶YAG crystal and 8 W for the other. The beam quality M2 value is about 1.2 in both horizontal and vertical directions at the maximum output power. The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high power 500.8-nm cyan laser.

The output characteristic of a novel hybrid fiber-bulk laser, demonstrated with a cladding-pumped tunable Tm-doped silica fiber laser as the pump source and HoYLF as the laser crystal,is researched. Most of the heat generated via quantum defect heating in this fiber-bulk laser scheme is deposited in the fiber, and thermal effects in the bulk laser are dramatically reduced leading to the prospect of much improved efficiency, beam quality and higher output power in the 2 μm wavelength regime. Output characteristics under different pumping wavelength were experimentally studied, and it was found that the best pumping wavelength was a few nanometers off the absorption peak. Using a simple two-mirror resonator configuration,a 5.3 W polarized output is obtained at 2066 nm in a diffraction-limited TEM00 beam (with M2 of about 1.1) for 9.4 W incident pump power, corresponding to a slope efficiency of 70%.

A laser diode end-pumped 1053-nm all solid state continuous wave single frequency Nd∶YLF laser is designed and demonstrated experimentally. In order to overcome the low fracture limit, a long and low concentration Nd∶YLF is used in the experiment. The threshold power of the laser is 4.7 W and the single frequency output power is 4.21 W at pump power of 17.9 W. The long term power fluctuation is less than ±0.8％ (4.75 h) and the free running frequency stability is ±10 MHz/min. To improve the frequency stability, the laser is locked to a Fabry-Perot cavity resonance, then the measured frequency stability is less than ±1.7 MHz/min.

In order to obtain LD-pumped intracavity sum-frequency 491 nm blue laser, the oscillation conditions for the simultaneous dual-wavelength operation of 1063 nm and 912 nm were analyzed based on the threshold expressions of quasi-three-level and four-level system. In the experiment, a Nd∶GdVO4 laser crystal with doped concentration of 0.15% (atomic fraction) and size of 3 mm×3 mm×2 mm was pumped by a laser diode with the maximum output power of 3 W. A linear cavity setup was used to realize 912 nm and 1063 nm dual-wavelength operation. 0.8 mW 491 nm blue laser is obtained after a LBO crystal was inserted into the cavity as the sum frequency crystal.

Continuous wave 543 nm laser emission at powers as high as 105 mW is achieved by using an LD with a power of 2 W to pump 0.8% (atom percent) Nd:YVO4 crystal, with intracavity frequency doubling in a 10 mm long type I critical phase matching LBO crystal and a simple linear resonator. The optical to optical conversion efficiency is up to 5.53% with the incident pump power of 1.9 W, and the long term stability of the output power is better than 3% in 3 h.

The laser at 1.342 μm wavelength from an all-solid-state single frequency Nd∶YVO4 laser was used to pump a frequency-doubler consisting of LBO crystal with type-I critical phase matching. Under the 1.14 W pump power, the second harmonic output of 580 mW is obtained with the double efficiency of 50.9%. The intensity fluctuation of the second harmonic wave at 0.671 μm is less than ±0.5% in 1 h and the laser frequency shift is better than ±2 MHz in 1 min under the condition of free running.

A laser diode (LD) end-pumped Nd∶YVO4 three-wavelength laser is reported by BIBO intracavity second harmonic generation(SHG) and sum-frequency mixing (SFM) at the same time. Through the two different transitions(1064 nm and 1084 nm) of Nd∶YVO4 crystal as fundamental waves and a nonlinear crystal BIBO with 1.5 mm-thick and type-I phase matching cut for SHG on 1064 nm, a three-wavelength laser with two doubling waves (532 nm and 542 nm) and one SFM wave (537 nm ) is obtained by adjusting the phase matching factor, nonlinear conversion efficiency, of the three nonlinear frequency conversion processes (1064 nm and 1084 nm SHG respectively, 1064 nm and 1084 nm SFM). The experimental results show that SGH and SFM of nonlinear crystal with little phase accepted angle is an efficient way to realize multi-wavelength laser when two fundamental waves with a little interval wavelength.

The thermal effect of Nd:YAG crystal rods induced by laser diode-pumped is analyzed theoretically, the more rational boundary conditions are established considering the distribution of laser beam in the crystal and the heat convection between the side surface of the crystal and the coolant. As a result, the more actual temperature field in the crystal is obtained, and the influences of crystal radius and side surface area on thermal effect are calculated simultaneously. The results show that the temperature in the center and on the side surface of the crystal increases when the convective heat-transfer about the side surface is considered, the focal length of crystal increase a little bit correspondingly. As decreasing the crystal radius, the differences in temperature between the center and the side surface of the crystal decrease, the focal length of crystal increases and the thermal effect of the crystal reduces. As increasing the side surface area, the temperature of the crystal decreases, while the focal length of crystal decreases and the thermal effect aggravates, for the rate change of temperature nearby the crystal center increases for the feature of end-pumped.

Two main thermal effects, thermal birefringence and thermal lens effect, are introduced. The depolarization, thermal bifocal lens and thermal lens aberration effects in solid state laser and their influences on output power of TEM00-mode are analyzed. Using the 4f imaging system and silicon rotator for point-to-point compensation of laser rod cross section, depolarization effects are compensated and mitigated.

In a three-stack side-pumped laser, the gaps between two arrays for cooling make the pump light nonuniform and affect the thermal uniformity in the crystal. Based on the light intensity equation and the distribution characteristic of hot source, numerical method for thermal lens focus is proposed. With the total pumping power unchanged, the effects of dimensional duty factor of arrays and the distance between LD and the center of the crystal on the thermal lens focus are numerically calculated. The thermal lens focus increases along with the increasing array dimensional duty factor and the pumping distance. The result indicates that the evener the pump light distributes along the axis, the smaller the thermal lens affects. It can furnishe evidences for making choice and improving pump resources when axial thermal uniformity is concerned.

Based on the theory of semi-analytical thermal analysis, thermal effects within a diode-end-pumped cubic Nd∶GdVO4 microchip crystal cooling from back surface are investigated. Based on the analytical theory of aeolotropies, a thermal model that matches the actual working state of the microchip crystal is established. Temperature and thermal distortion fields within the microchip crystal are analyzed and general solutions of the temperature and thermal distribution fields of the crystal are obtained by using a novel method to solve the heat conduction equation of anisotropic medium. Research results show that a maximum temperature rise of 69.6 ℃ and a maximum thermal distortion of 74.1 nm can be obtained in the center of the pump face when the Nd∶GdVO4 microchip crystal doped with 1.2% Nd3+ is end pumped in the center of the front end face by LD (the super-Gaussian order is 4) with an output power of 700 W, which is in agreement with experimental results. The method can be applied to other thermal analyses of laser crystals.

Based on the method of energy equipartition the temperature and stress distribution of the composite ceramic Nd∶YAG laser slab with stepwise gradient dopant concentrations for high power laser diode(LD) end-pumping is proposed by theoretical analysis and simulation. Using the composite slab with stepwise gradient dopant concentrations, high pump absorption efficiency and intensity uniformity in slab lasers can be separately achieved, which would lead to smaller thermal induced stress. It resolves the contradiction between the pumping efficiency and the homogeneity of pumping absorbed power.

A method for increasing the maximum cross-section of beam in a five-sided slab by optimal selection of its geometry parameters is presented. The geometric analysis results indicate that the absorption coefficient of pump laser must be greater than the threshold value. The thermal distortion is analyzed by numerical simulation and the results show that it is hard to obtain high beam quality at high output power due to strong but inconsistent intensity of thermal effects in both width and thickness direction.

The high power all solid state intracavity optical parametric oscillator (IOPO) at 1.5 μm eye-safe wavelength band based on KTA and KTP crystals is demonstrated. Under the repetition rate of 18 kHz, the optimum signal output power of 13 W at 1.5 μm with a 5.46 ns pulse width, and idler beam of 3 W at 3.4 μm were obtained using laser diode-side-pumped Nd:YAG 1064 nm high power laser as the KTA-IOPO pumping source. In addition, the characteristic of KTA-IOPO was compared with that of the similar crystal KTP. These results show that the absorption of 3.4 μm wavelength band in KTA was negligible compared with KTP crystal, allowing high-power and high-frequencey-conversion operation with minimal thermally induced refractive distortion in the OPO crystal.

A diode array side pumped Nd:YAG thin disk laser was reported, and the light distribution of doped crystal and temperature distribution of the radial were studied theoretically and experimentally. The output laser peak power of 230 W, opt.-opt. efficiency of 33.5% and beam parameter product of 21.6 mm·mrad were obtained. The results of experiment showed that side pumped Nd:YAG thin disk laser could realize light uniform distribution, and decrease temperature difference of radial significantly. And composited Nd:YAG/YAG cryatal could satisfy the requirements of side pumped thin disk laser. These techniques and methods could apply to higher power side pumped thin disk laser.

We present the characteristics of a folded-cavity actively Q-switched intracavity frequency-doubled Raman laser in which a KTP crystal is used as the frequency-doubling material, an Nd∶YAG crystal is used as the gain medium and an SrWO4 crystal as the Raman medium. The dependences of the average output power, the pulse energy and width on the pulse repetition rate and incident LD pump power are given. When the incident pump power is 12.6 W and the repetition rate is 20 kHz, the average output power is 1.4 W, and the corresponding conversion efficiency from the diode laser to yellow laser is 11.1%. When the incident pump power is 12.6 W and the repetition rate is 10 kHz, the pulse energy is 122 μJ, the pulse width is 4.0 ns, and the corresponding peak power is 30.5 kW.

A laser diode-pumped Kerr-lens self-mode-locked laser was achieved by using YbLu2SiO5(Yb:LSO) crystal without any active or passive modulators and hard diaphragm inside the cavity. With the incident pump power of 15.8 W, the output power of the Kerr-lens self-mode-locked pulse reaches 2.05 W in the four-mirror cavity, corresponding to a slope efficiency of 16.5%.

A stable continuous-wave mode-locked picosecond Yb:LSO laser was demonstrated. The 5% doped Yb3+Lu2SiO5 (Yb:LSO) crystal was used as the laser medium, and a semiconductor saturable absorber was employed to realize mode-locking. With the pump power of 2 W, the output picosecond pulse power is 70 mW, at the repetition rate of 69.8 MHz. The measured pulse width is 3.6 ps, and the center wavelength can be at 1047 nm or 1066 nm.

A LD side-pumped Nd∶YAG all-solid-state ultraviolet laser is demonstrated under acousto-optic Q-switched operation, by using a simple and compact three-mirror folded and flat-concave cavity resonator, with type Ⅰphase-matched LiB3O5 (LBO) as second harmonic generation crystal and type Ⅱ phase-matched LBO as third harmonic generation crystal. The output power of 355-nm UV laser reaches to 2.14 W at the incident pump power of 155 W and repetition rate of 5.40 kHz with pulse width of 45 ns. The light-light conversion efficiency is about 1.38 %, and the power stability is 3.30% in 1 h operation accordingly. The influence factor on the triple frequency conversion efficiency is studied.

Experimental results of high-efficiency 2.7-μm laser is demonstrated on quasi-phase-matched single-resonated optical parametric oscillator (OPO) in PPMgLN (5% MgO-doping) pumped by 1064-nm laser. Theoretical analyses of PPMgLN grating period tuning are presented. When grating period is 31.3 μm, a PPMgLN OPO could get output at wavelength of 2.7 μm. The pump beam polarization matches the e→e＋e interaction in PPMgLN, thus maximal nonlinear coefficient d33 (27.4 pm/V) is effective and walk-off of beams can be avoided. When pump power is 26 W with repetition rate of 7 kHz, an average output power of 4.7 W at wavelength of 2.72 μm is obtained with slope efficiency of more than 21%, and 9 W at the corresponding idler wavelength of 1.75 μm. The M2 factors of 2.7-μm laser are 2.05 and 1.84 in parallel and perpendicular directions, respectively.

The dual wavelength and dual pulse light source with wavelengths of 448.1 nm and 449.15 nm have potential application in differential absorption lidar (DIAL) for measuring NO2 concentration in atmosphere. A dual wavelength (896.2 nm and 898.3 nm) and dual pulse Cr∶LiSAF laser output is achieved adopting the high pressure and square wave to drive the electric light Q-switch. Using one LBO crystal as the frequency doubling crystal, a dual wavelength (448.1 nm and 449.15 nm) and dual pulse laser is got. The output for one wavelength is about 13.7 mJ, the line width is less than 0.02 nm, and the time interval for two pulse in one pumping is about 62 μs.

The high power mode-locking laser system consists of an active-active mode-locking oscillator, a double-pass pre-amplifier, and two single-pass amplifiers. And the fine cavity length adjustment mechanics, single pulse selector, compensation for depolarization, and other key technologies are used. 1064-nm single pulse energy over 500 mJ is obtained, whose pulse duration is 300 ps, and the jitter is ±15 ns with respect to the external trigger. In addition, 532-nm single pulse energy exceeds 240 mJ, whose harmonic generation efficiency is more than 45% by using BBO crystal. And this laser has been used in satellite laser ranging (SLR) system, with pulse shots larger than 2×108.

A deep ultraviolet solid-state laser system using nonlinear optical frequency conversion technique, which is based on sum-frequency generation in a CLBO crystal is reported. The two beams involved in the sum-frequency generation are 1064 nm from an all-solid-state acoustic-optic Q-switched Nd:YVO4 laser and 238.7 nm from a third-harmonic generation of a Tisapphire laser pumped by a lamp-pumped electronic-optic Q-switched frequency-doubled Nd:YAG laser. The Q-switched frequency-doubled Nd:YAG laser, Tisapphire laser, BBO third-harmonic generator, Q-switched Nd:YVO4 laser and CLBO sum-frequency generator in the system are described in detail. Stable 195 nm deep ultraviolet laser with maximum output power of 217 μW at 10 Hz is achieved in experiment.

A 940 nm InGaAs laser diode (LD) array end-pumped Yb∶YAG disk laser has been demonstrated, chosing V-shape stable resonator with active-mirror configuration. The infrared laser output at 1030 nm is obtained. The output performance of the laser under different repeat frequencies (1 Hz,2 Hz,5 Hz,10 Hz) is experimentally tested. With output mirror reflectivity of 73% and pump energy of 7.6 J (power of 13 kW/cm2), the output energy of 2.43 J is obtained with repeat frequency of 1 Hz, the optical-optical efficiency is 32% and the slope efficiency is 54.5%; the output energy of 1.76 J is obtained with repeat frequency of 10 Hz, the optical-optical efficiency is 23.2% and the slope efficiency is 43.3%.

Optimum design of the optics structure for the femto-second laser aimed at Cr4+∶YAG crystal is investigated by theoretic analysis and numerical calculation. So as to reduce the complexity, a thin focus lens is plugged into the resonator to replace the fold-mirror. The pair of prisms can affect the stability and astigmatism besides the dispersion compensation, so the optics transmission matrix is deduced to eliminate them. The stability diagrams are obtained for continue-wave-operation and mode-lock-operation with diverse parameters by computer programming, and the way for, selecting the work point is described. The un-match factor (F) of the astigmatism compensation is defined, and the area distribution diagram is painted according to it. The excellent astigmatism compensation can be possessed for running laser on the stable area with F<0.05. The match of pump and oscillating laser beams within the cavity can be achieved by changing the position of the focus lens.

Experimental results of thermal effect in laser diode (LD) three-direction side-pumped Tm,Ho∶ LuLiF laser are reported. It is calculated of the distribution of pump intensity in the laser medium. The effects on the pump intensity and uniformity under different pump waists are analyzed. Temperature distribution in the laser media is simulated by finite element analysis. Considering the laser medium as lenslike, the experiment measuring is developed. Using the intensity changing of Gaussian beam through small aperature, the Gaussian beam shapes of He-Ne laser through the laser medium is fitted. Caculating from the approximate transformation of Gaussian beam by thin lens, the thermal focal length of Tm,Ho∶LuLiF crystal is about -2.3 m with pump pulse power of 3.3 J and pulse repetiton frequency of 10 Hz. The experimental result is in agreement with the theoretical prediction.

A laser diode-pumped all-solid-state narrow linewidth sodium guide star laser was developed. The repetition rate was 400 Hz and the average power was 1.0 W. Two acousto-optic (AO) Q-swithed lasers of 1064 nm and 1319 nm were used as basic-frequency lasers ,and then 589 nm sodium guide star laser was generated through a extra-cavity sum-frequency generation (SFG) lithium triborate (LBO) crystal. The efficiency of sum-frequency generation was about 20%. Each of the basic frequency lasers was adopted well-designed etalons to narrow the linewidth. The linewidth of the 589 nm laser was controlled to about 1.8 GHz. The central wavelength was locked to 589.159 nm(±1 pm) by tuning the temperature and angle of the etalons. In the end, the sodium guide star laser’s spectra was exactly matched to the D2 line of the sodium atoms.

The noise characteristic of the fiber laser with single frequency operation is experimentally investigated. The prepositive optoelectronic feed-forward is used to suppress the intensity noise of the fiber laser. Selecting the best delay time and feed-forward gain, the intensity noise can be suppressed near to shot noise limit at any sideband frequency. The maximum noise reduction of 22 dB is obtained at 6.0 MHz.

In order to meet the requirements of coherent Doppler wind lidar laser transmitter, a compact all-fiber master-oscillator power-amplifier(MOPA)laser is studied. On the other hand, high pulse repetition rate, narrow frequency linewidth, eye-safe and all-fiber configuration are required. This kind of all-fiber laser is presented with 10 kHz pulse repetition rate, 500 ns pulse duration, 1 MHz frequency linewidth, 50 mW average power and 5 μJ pulse energy, which will become the laser transmitter of a coherent Doppler lidar to measure wind in lower atmosphere layer.

An all-fiberized master oscillator power amplifier(MOPA) structured pulsed Yb fiber laser is reported. The seed source was an acousto-optic (AO) Q-switched Yb fiber laser working at 1064 nm and emitting a random polarized pulsed emission with an average power of 2 W at repetition rates between 20 kHz and 50 kHz. Using a polarization maintaining(PM) large mode field double-cladding fiber as the gain medium and six LDs each with 10 W power output at 915 nm as the pump, the Yb fiber amplifier delivered a linearly polarized pulsed emission output at 1064 nm with an average power of 23.5 W, pulse duration about 30 ns, polarization extinction ratio greater than 10 dB, and a beam quality factor M2 of 1.36. The effect of mode field mismatch between the output fiber of seed laser and the large mode field PM fiber, which influenced the beam quality and the spectral distribution of the laser output, was discussed.

A two-stage high power narrow linewidth fiber amplifier was demonstrated. The first stage was single mode Er3+ doped fiber amplifier. The double clad Er3+/Yb3+ co-doped fiber amplifier was designed as power amplifer in which two 980 nm high power laser diodes were used as the pump sources.With the maximum pump power of 10.7 W, the amplifer output powers was 1.94 W and the optical-optical conversion efficiency was 20%, the slope efficiency was 17%. The 3 dB linewidth of seed laser and each amplifier were measured by the delayed self-heterodyne method with 10 km single mode fiber. The results show that obvious spectral broadening happenes during the amplification process. The reason of spectral broadening is owing to self-phase modulation caused by intensity fluctuations of relaxation oscillations or self-pulsing.

The output characteristics and their influence factors of a fiber laser with high repetition rate and narrow pulse width based on master-oscillator power amplifier (MOPA) architecture are experimentally investigated. Under the condition of high output power, the impacts of the stimulated Raman scattering (SRS) on the gain characteristics and laser spectrum characteristics are analyzed through experiments. It is pointed out that SRS effect is the main restriction of power increases of fiber laser. By increasing the effective mode-field area and shortening the length of fiber, stimulated Raman scattering is suppressed successfully. The average output power of 64 W is achieved at repetition rate of 50 kHz with a pulse width of 14 ns. Meanwhile, the impacts of the fiber bending diameter on the output characteristics of laser are also experimentally investigated. The results show that reducing the diameter of bending properly can improve beam quality of output laser in a certain extent.

A pulse master oscillator power amplifier (MOPA) system, which can provide high repetition rate and nanosecond pulse laser, was constructed by China-made large-mode-area(LMA) fiber and single mode 1064 nm laser-diode(LD) with fiber cascaded amplification system used as seed laser. The system generates up to 59 W average power of amplified radiation at a wavelength of 1064 nm with pulse duration of 22.7 ns(at 50 kHz repetition rate) and adjustable repetition frequency of 50～150 kHz. Some basic characteristics of this system, including the pulse temporal characteristics as well as the emission spectrum characteristics are investigated experimentally, and the impacts of the power amplification of the fiber to the pulse duration are analyzed.

Using the high power multimode pumping method, the Er/Yb co-doped double clad fiber (EYDCF) two-stage master oscillation power amplification (MOPA) based on all-fiber configuration is experimentally studied. With continuous wave (CW) amplification, the maximal output power is 1.52 W, the degree of stability is 0.4% and the slope efficiency is 29%. While with 2 kHz pulsed amplification, the maximal output power is 1.1 W, the degree of stability is 0.45% and the slope efficiency is 25%. The fact that the slope efficiency and the power conversion efficiency (PCE) of pulsed amplification are lower than the CW is caused by the appearance of the Yb3+ band, and the accumulation of the Er3+ band ASE deduces from the output spectrum and time domain waveform. The gain of the amplifier decreases seriously as the input power increases under the high power amplification condition. The impact that the fluctuation of the pump spectrum with the driven current on the amplifier performance is also analyzed.

Multi-wavelength erbium-doped fiber laser using two polarization-maintaining fiber Bragg gratings (PMFBGs) in the symmetrical linear cavities at room temperature is proposed. Due to the polarization hole burning (PHB) enhanced by the PMFBG and the symmetrical cavities structure, stable four-wavelength lasing emission can be generated by adjusting the polarization controllers (PCs) simply. The side mode suppression ratio (SMSR) is over 50 dB. The amplitude variation with 16 times scan in nearly one and a half hours is less than 0.8 dB.

A new kind of single-longitudinal-mode and wavelength-switchable fiber laser is proposed and experimentally demonstrated. Such a fiber laser has a ring resonant cavity. An unpumped erbium-doped fiber (EDF) in the cavity is used as the saturable absorber to achieve single-longitudinal-mode operation. An 1×2 optical switch and 2 parallel fiber Bragg gratings (FBGs) are used as the wavelength selection module to achieve wavelength-switchable operation. At 17.5-dBm output power of EDF amplifer, the single-longitudinal-mode laser with 2.5-dBm power and 3-kHz linewidth is generated. The wavelength is randomly switched between 1545.2 nm and 1556.4 nm by applying the suitable electrical signal to optical switch.

A numerical model of the upconversion fiber laser with gain media of erbium-doped tellurite-based glass fiber was presented. The lasing output performance of erbium-doped tellurite-based glass upconversion fiber laser was investigated theoretically, and the dependence of 546 nm green output power on launched 980 nm pump power and fiber length of resonant cavity were analyzed. The results indicate that erbium-doped tellurite-based glass upconversion fiber laser can achieve milliwatt lasing power in a resonant cavity length of centimeter order, and its slope efficiency reaches about 7%. Compared to the reported fluoride glass upconversion fiber laser, the erbium-doped tellurite-based glass upconversion fiber laser shows a potential small-scale characteristic of solid laser.

The output characteristic of hundred-micron core diameter fiber laser and its mode control technique are researched. In theory, feasibility of which using winding to control the modes of hundred-micron core diameter fiber laser is analyzed. In experiment, output modes of hundred-micron core diameter fiber laser are controled by the hole in the laser cavity, and the effects to beam quality are researched with holes of different diameters.When there is no hole in the laser cavity, the beam quality factors M2 are 4.67 and 4.60 in x and y direction. After adding 2 mm diameter holes in the cavity, the beam quality factors M2 are 1.96 and 2.01 in x and y direction.The beam quality is improved remarkably by the holes.

Current developments of high power laser diode-pumped solid-state lasers such as disk rod laser, disk/slab laser, fiber laser and heat-capacity laser at home and abroad are investigated. Focusing on the problem of thermal effects in solid-state lasers which limits the increment of the output average power and degrades the output beam quality, the advantages and disadvantages of kinds of lasers are compared. Current techniques to decrease or compensate for the effects of the useless heat are summarized, and the probable techniques to reduce the laser′s thermal effects are pointed out.

Deep-ultraviolet (DUV) diode-pumped solid-state laser (DPL) is a novel coherent light source, which is meant to the solid-state laser with the wavelength below 200 nm. DUV-DPL is well known for its precision and application performance. Its history, current, development and applications of DUV-DPL are introduced in detail.

Adaptive optical wavefront control technique is an important means to improve the beam quality in the inertial confinement fusion (ICF) laser system. The new progress on adptive optics (AO) in ICF facility, including the 8 sets of AO systems for the “Shenguang Ⅲ” prototype facility, the development of the large aperture deformable mirror (DM) prototype with the replaceable actuators used in the future ICF systems, and the AO wavefront control technologies, are introduced. In the “Shenguang Ⅲ” prototype facility, the static aberrations of the entire optical system from the front-end to the target using the 8 sets of AO systems are successfully corrected and the focal spot intensity distributions in the target are improved. The improvement of the X-ray distributions after AO correction is observed. A large aperture DM prototype with 17 replaceable actuators, 284 mm×284 mm aperture size, more than ±6 μm stroke and 500 Hz resonant frequency is manufactured and tested. The stochastic parallel gradient descent (SPGD) algorithm based on the far-field focal spot intensity is tested and proven to be effective for the ICF facility.

The research progresses of all-solid-state single-frequency lasers, such as the increasing of output power, new mode-selecting and wavelength tuning techniques, spectrum range expanding and the improvement of laser property, are introduced briefly.

Three types of evaluation on laser beam quality such as near-field quality, far-field quality, and propagation quality are summarized. The parameters include modulation ratio and contrast ratio of near-field, focused spot size, far-field divergence angle, times diffraction limited factor β, Strehl rate, energy circle rate, M2 factor, etc. The application range, strong point and shortcoming of them especially used in evaluating beam quality of high power laser beam are discussed. Furthermore, a matrix of M2 factor for comprehensive evaluating astigmatic beam has been proposed, and the invariant value is given.

High repetition rate short pulsed compact solid state lasers pumped by laser-diode (LD) are promising and compellent in many applications such as laser machining, free space laser communications, spaceborne lidar, and laser ranging. Electro-optic (EO) Q-switching has been approved an effective method to obtain stable output with high peak power, narrow pulse width and small pulse-to-pulse amplitude fluctuation. Recently, with the development of new types of electro-optic crystals, the repetition rate of EO Q-switched solid state lasers has been improved significantly. The recent progresses of high repetition rate EO Q-switched solid state lasers are introduced in detail.

It has been shown by intensive research activities in the optics and optoelectronics fields that many novel properties unimaginable with conventional optical fibers can result from the holey structure in photonic crystal fibers (PCF), including flexible design of dispersion, enhanced nonlinearity, endlessly single mode operation, and high birefringence. Photonic crystal fiber has been successfully applied in femtosecond laser technology and pushed the output performance of femtosecond fiber laser to match with the solid-state laser system. A review of recent work on high power femtosecond photonic crystal fiber laser oscillator, amplifier and their applications are proposed. Feasible scenario in future applications of high pulse energy large mode area photonic crystal fiber lasers will be come soon.

Solar pumped lasers convert sunlight into laser radiation directly. The investigators of solar pumped lasers at home and abroad are introduced. The advantages of solar pumped lasers in application are discussed with the efficiency of sunlight conversion to laser radiation, and the history of solar pumped laser development and demonstration is reviewed. Solar pumped solid state lasers are classified and analyzed by sunlight concentrating approach, and the future development of solar pumped lasers is predicted.

It is one of the most important questions to reduce the thermal effect and accumulation in the laser medium effectively, by pumping and lasing in the research of laser diode pump solid-state laser (DPSSL) at high power laser level. Compared with the conventional pumping scheme, direct pumping scheme at longer wavelength will not only reduce the heat by 30%～50%, but also improve the laser performances significantly. The development and status of direct pumping DPSSL based on the research of the Nd3+ doping laser are reviewed, the characteristics of the new pumping scheme and the progresses on Nd doping lasers are introduced. Finally, the new development in the future is prospected.

For the high-power solid-state laser, the cooling technology has become one of the key techniques for its development. This paper reviews the current development of cooling technology dealing with the high-power solid-state laser, both in use and in the experimental stage, which includes the liquid convection heat exchange in microchannel, diamond cooling, spray cooling and micro-heat-pipe cooling. On the basis of our recent research and the summarization of the development, we propose two promising cooling methods, boiling heat exchange in microchannel and liquid nitrogen cooling, and discuss the recent progress of theoretical studies on the two techniques.

The research productions of the corner-pumped all-solid-state lasers gained by Tsinghua University in the recent years are reported. The primary contents include the developments of all-solid-state corner-pumped Yb∶YAG lasers with high output powers, all-solid-state corner-pumped Yb∶YAG LBO external cavity frequency doubling green lasers, and all-solid-state corner-pumped Nd∶YAG fundamental mode lasers with small and medium output powers.