Efficient and high-power laser-diode single-end-pumped Nd：YVO4 continuous wave laser at 1342nm

A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.     

High Power Continuous-Wave Diode-End-Pumped 1.34-μm Nd：GdVO4 Laser

A high power cw all-solid-state 1.34-μm Nd：GdVO4 laser is experimentally demonstrated. With a diode-double-end-pumped configuration and a simple plane-parallel cavity, a maximum output power of 27.9 W is obtained at incident pump power of 96 W, introducing a slope efficiency of 35.4%. To the best of our knowledge, this is the highest output power of diode-end-pumped 1.3-μm laser. With the experimental data, the thermal-stress- resistance figure of merit of Nd：GdVO4 crystal with 0.3 at% Nd^3＋ doped level is calculated to be larger than 9.94 W/cm.     

Study on optical characteristics of Nd:YVO_4/YVO_4 composite crystal laser

Thermal effect in crystals is the main obstacle blocking diode-pumped solid state laser to get high and stable output, power. Diffusion bonding crystal has been demonstrated to be an effective method to relieve the thermal lensing theoretically based on the numerical heat analysis to the end-pumped anisotropic laser crystal. The temperature distributions in Nd:YV04/YVO4 composite crystal and conventional crystal were analyzed and compared. The end-pumped Nd:YVO4/YVO4 composite crystal laser was designed and set up with 2-cavity. The maximum output powers of 9.87 W at 1064 nm and 6.14 W at 532 nm were obtained at the incident purnp power of 16.5 W. The highest optical-optical conversion efficiencies were up to 59.8% at 1064 nm and 37.2% at 532 nm respectively.     

Passively mode-locked grown-together composite YVO4 /Nd:YVO4 crystal laser with a semiconductor saturable absorber mirror under 880-nm direct pumping

A passively mode-locked grown-together composite YVO 4 /Nd:YVO 4 crystal laser is demonstrated with a semiconductor saturable absorber mirror by 880-nm laser-diode direct pumping.Under the absorbed pump power of 24.9 W,a maximum output power of 10.5 W at the repetition rate of 77 MHz is obtained,corresponding to the optical-optical conversion efficiency of 42.1% and the slope efficiency of 53.4%.The pulse width measured is 33 ps at the output power of 10 W.     

Compact high-power mode-locked Nd：YVO4 picosecond laser using multiple-pass cavity

A stable self-starting mode-locked Nd:YVO4 laser with a Herriott-type multiple-pass cavity(MPC) operating at 1 064 nm is demonstrated.An in-band 880-nm laser diode is used as an end-pump and a semiconductor saturable absorber mirror(SESAM) is used for passive mode locking(ML) and providing pulse durations of 14 ps.At a pump power of 26.4 W,the maximum average output power is as high as 10.5 W at a repetition rate of 22 MHz,which corresponds to a single pulse energy of 0.48 μJ.Optical-tooptical conversion efficiency is as high as 39.8% at the maximum output power with a slope efficiency of 55.2%.     

Theoretical analysis and experimental research on thermal focal length of a YVO4/Nd:YVO4 composite crystal

This paper investigates the temperature field distribution and thermal focal length within a laser diode array (LDA) end-pumped YVO4/Nd:YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd:YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd:YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd:YVO4 rectangular crystal for the YVO4/Nd:YVO4 composite crystal and the Nd:YVO4 single crystal are researched respec- tively. Calculating the thermal focal length within the Nd:YVO4 rectangular crystal was done by an analysis of the additional optical path differences (OPD) caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd:YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7 mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd:YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd:YVO4 crystal and the Nd:YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd:YVO4 laser is more advantageous than the laser with Nd:YVO4 single crystal.     

High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd：YVO4 Laser at 671 nm with a Compact Three-Element Cavity

We report a high-power high-efficient continuous-wave （cw） diode-end-pumped Nd：YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope effciency of 37.3%. By inserting a type-Ⅰ critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd：YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.     

High power doubly resonant all-intracavity deep blue laser at 447 nm based on sum-frequency-mixing technology

A high power continuous-wave deep blue laser at 447 nm is obtained by using a doubly cavity and a type H critical phase matching KTP crystal for intracavity sum-frequency-mixing. With the incident pump power of 240 W for the Nd：YAP crystal and 120 W for the other Nd：YAP crystal, the deep blue laser output of 5.7 W at 447 nm with near fundamental mode is obtained, and the beam quality M^2 value equals 2.53 in both horizontal and vertical directions at the maximum output power. The power stability is better than 2% at the maximum output power during half an hour. The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high power blue laser.     

A Laser-Diode-Pumped 7.36 W Continuous-Wave Nd：YVO4 Laser At 1342 nm

An efficient and high-power diode-laser single-end-pumped Nd：YVO4 laser with cw emission at 1342nm is presented. With a crystal single-end-pumped by a fibre-coupled diode laser, an output power of 7.36 W is obtained from the laser cavity of concave-convex, eorresponding to an optical-to-optical conversion efficiency of 32.8%. The laser is operated in TEM00 mode with small rms noise amplitude of 0.3%. This represents, to the best of our knowledge, the highest power obtained from a diode-laser single-end-pumped Nd：YVO4 cw laser at 1342nm 80 far.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

Low Threshold and High Conversion Efficiency Nanosecond Mid-Infrared KTA OPO

Based on a Type II non-critically phase-matched KTA crystal, a low-threshold and high conversion efficiency mid-infrared optical parametric oscillator （OPO） pumped by a diode-end-pumped Nd：YVO4 laser is demonstrated. The OPO threshold is only 0.825W. The maximum output power of 435mW at 3.47μm is achieved with the repetition rate of 30kHz, corresponding to an optical-to-optical conversion efficiency of 4.4%. The photon conversion efficiency is as high as about 64%. The pulse width is 3.5ns with a peak power of 4kW for the maximum output power.     

High peak power 1.0 μm and tri-wavelength 1.3 μm Nd:ScYSiO_5 crystal lasers

With a Nd:ScYSiO_5 crystal, a high peak power electro-optically Q-switched 1.0 μm laser and tri-wavelength laser operations at the 1.3 μm band are both investigated. With a rubidium titanyle phosphate(RTP) electro-optical switcher and a polarization beam splitter, a high signal-to-noise ratio 1.0 μm laser is obtained, generating a shortest pulse width of 30 ns, a highest pulse energy of 0.765 mJ, and a maximum peak power of 25.5 kW,respectively. The laser mode at the highest laser energy level is the TEM200 mode with the Mvalue in the X and Y directions to be M_x~2= 1.52 and M_y~2= 1.54. A tri-wavelength Nd:ScYSiO_5 crystal laser at 1.3 μm is also investigated. A maximum tri-wavelength output power is 1.03 W under the absorbed pump power of7 W, corresponding to a slope efficiency of 14.8%. The properties of the output wavelength are fully studied under different absorbed pump power.     

All-Solid-State Near-Infrared and Blue Femtosecond Laser System

We investigate an all-solid-state continuous wave(cw) green (532nm),femtosecond near-infrared (823.1nm) and blue (402nm) laser system which is pumped by a diode-laser-pumped intracavity frequency-doubled and all-self-structuring cw Nd:YVO4/KTP 532nm green laser.The cavity parameters of the Nd:YVO4/KTP laser have been optimized and the maximum 5.6W TEM00 green laser is obtained at a 22W pump power with an optical-optical conversion efficiency of 25.5%.A Ti:Sapphire laser and nonlinear second-harmonic generation by a crystal BBO is used to obtain different wavelengths.A femtosecond laser with an average output power of 300mW at 823.1nm and 73mW at 402nm is obtained when the green pump power is 2.5W.The spectral full width at half maximum are 32.3 nm and 5.1 nm,which can sustain the pulses of 22 fs and 33.3 fs,respectively.     

Compact, Low Threshold Nd^3＋：YVO4 Self-Raman Laser at 1178 nm

A compact low-threshold Raman laser at 1178 nm is experimentally realized by using a diode-end-pumped actively Q-switched Nd^3＋ ：YVO4 self-Raman laser. The threshold is 370mW at a pulse repetition frequency of S kHz. The maximum Raman laser output is 182 m W with the pulse duration smaller than 20 ns at a pulse repetition frequency of 30kHz with 1.8 W incident power. The optical efficiency from the incident power to the Raman laser is 10% and the slope efficiency is 13.5%.     

Suppressing the preferential σ-polarization oscillation in a high power Nd:YVO_4 laser with wedge laser crystal

We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO 4 crystal as the gain medium, the unexpected σ -polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected π-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no σ -polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.     

Spectroscopic investigation of a new crystal： Nd^3＋,Yb^3＋：YVO4

The absorption and emission spectra of the YVO4 single crystal co-doped with 1 at.% Nd^3＋ and 1 at.% Yb^3＋ are investigated. The efficient Nd^3＋ → Yb^3＋ energy transfer and the back transfer （Yb^3＋ → Nd^3＋） are observed at room temperature. The fluorescence lifetime of the 4F3/2 level of Nd^3＋ in Nd,Yb：YVO4 is measured under 808 nm laser light excitation. The efficiency of Nd^3＋ → Yb^3＋ energy transfer in YVO4 is determined to be about 34%.     

Single output LD end-pumped passively mode-locked Nd:YVO4 laser with semiconductor saturable absorber mirror

A quarter-wave plate and the thin film polarizer(TFP) are used for the LD end-pumped passively mode-locked Nd:YVO4 laser with semiconductor saturable absorber mirror(SESAM) to obtain a single beam output with a total power of 4.8 W.An optical-optical efficiency is achieved to be 24% for a stable CW mode-locking operation at 1064 nm,with a pulse repetition rate of 70 MHz and pulse width of 16 ps.The multipulse in the pulse sequence is eliminated for reaching a peak power as high as 4 kW.     

Stable High Power and High Beam Quality Diode-Side-Pumped Continuous-Wave Intracavity Frequency-Doubled Nd:YAG Laser

We report a stable high power and high beam quality diode-side-pumped cw green laser from intracavity frequency-doubled Nd： YAG laser with KTP. By using a L-shaped concave-convex resonator, designed with two Nd：YAG rods birefringence compensation, a large fundamental mode size in the laser crystal and a tight focus in the nonlinear crystal could be obtained simultaneously. The green laser delivers a maximum 532nm output power of 23.2 W. Under 532nm output power of 20.9 W, the beam quality factor is measured to be 4.1, and the fluctuation of the output power is less than 1.4% in an hour.     

Suppressing the preferential o-polarization oscillation in a high power Nd：YVO4 laser with wedge laser crystal

We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd：YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd：YVO4 crystal as the gain medium, the unexpected a-polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected zc-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no a-polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.     

Laser performance and thermal lens of diode-pumped Nd,Y-codoped:SrF_2 single crystals

We demonstrate the laser performances of Nd, Y：SrF2 crystals with Nd＇3＋ concentrations of 0.15 and 0.43 at.%. The sample with 0.43 at.% Nd3＋ concentration yields a maximum output power of 1.023 W at 1056.9 nm with a slope efficiency of 53%. The focal length of the thermal lens is analyzed for the 0.15 at.% Nd3＋-doped crystal sample. An improved cavity is designed considering the thermal lens. The maximum output power is 464 mW at 1056.9 nm, with a slope efficiency of 36.1%. The wavelength is tuned within the range of 1049.74-1059.13 nm.