Analysis of a laser-diode end-pumped intracavity frequency-doubled passively Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/KTP laser with a semiconductor saturable absorber

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency-doubled Nd:GdVO₄/KTP green laser with a semiconductor saturable absorber is presented. Nearly 100% modulation depth for the mode-locked green pulses can be achieved at any pump power over 1.92 W. The width of the mode-locked green pulse was estimated to be about 150 ps. The mode-locked pulse interval within the Q-switched envelope of 320 ns and the repetition rate of 97.5 kHz were obtained, at an incident pump power of 4.4 W. The repetition rate of the mode-locked green pulses inside the Q-switched envelope was 140 MHz.     

Diode-pumped passively Q-switched intracavity frequency doubled Nd:GdVO4/KTP green laser

A compact diode-pumped passively Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green-pulse laser was demonstrated, using Cr⁴⁺:YAG as a saturable absorber in a simple flat–flat cavity. With a 5.9 W incident pump power, a passively Q-switched green laser was obtained with an average power of 397 mW, repetition rate of 40 kHz, and pulse width of 40 ns, when the initial transmission of Cr⁴⁺:YAG was 85%. The shortest pulse width of 30 ns, the highest green peak power of 696 W and the maximum pulse energy of 21 μJ were obtained when the initial transmission of Cr⁴⁺:YAG was 70%. Under CW green operation, we obtained 440 mW output power.     

Second Stokes 1129 nm generation in gray-trace resistance KTP intracavity driven by a diode-pumped Q-switched Nd:YVO4 laser

A gray-trace resistance KTP (GTR-KTP) second Stokes Raman laser intracavity driven by a diode-pumped acousto-optic Q-switched Nd:YVO₄ laser was first demonstrated in this paper. With an incident pump power of 9.5 W, the intracavity GTR-KTP Raman laser, operating at the repetition rate of 20 kHz, produced the maximum average output power of 860 mW at 1129 nm. The minimum pulse width obtained in this GTR-KTP Raman laser was 10.8 ns. When the GTR-KTP was substituted with a common KTP, a lower average output power of 720 mW and longer pulse width of 15.9 ns were obtained in the common KTP Raman laser under the same pump condition and cavity setup as the GTR-KTP Raman laser. Experimental results indicated that the decreased absorption at the fundamental and Stokes wave in GTR-KTP was beneficial to improve the stimulated Raman scattering performance.     

Q-switched and continuous-wave mode-locking of a diode-pumped Nd:Gd0.64Y0.36VO4−Cr4+:YAG laser

We report on a diode-pumped passively mode-locked Nd:Gd_0.64Y_0.36VO₄ laser with a Cr⁴⁺:YAG saturable absorber. Q-switched mode locking (QML) with 90% modulation depth was obtained. The peak power of the mode-locked pulse near the maximum of the Q-switched envelope was estimated to be about 1.7 MW at the pump power of 12 W. Besides QML, continuous-wave mode locking was also experimentally realized, for the first time to our knowledge, in the laser under a strong intracavity pulse energy fluence. The mode-locked pulse width is about 2.96 ps at a repetition rate of 161.3 MHz.     

Efficient sub-nanosecond intracavity optical parametric oscillator pumped with a passively Q-switched Nd:GdVO<Subscript>4</Subscript> laser

An efficient diode-pumped passively Q-switched Nd:GdVO₄/Cr⁴⁺:YAG laser was employed to generate a high-repetition-rate, high-peak-power eye-safe laser beam with an intracavity optical parametric oscillator (OPO) based on a KTP crystal. The conversion efficiency for the average power is 8.3% from pump diode input to OPO signal output and the slope efficiency is up to 10%. At an incident pump power of 14.5 W, the compact intracavity OPO cavity, operating at 46 kHz, produces average powers at 1571 nm up to 1.2 W with a pulse width as short as 700 ps. PACS 42.60.Gd; 42.65.Yj; 42.55.X     

Diode-pumped passively Q-switched yellow laser with SrWO4 Raman crystal and ceramic Nd:YAG gain medium

A diode-pumped passively Q-switched Nd:YAG/SrWO₄/KTP yellow laser is presented for the first time. As high as 1.02 W average output power was obtained at a pump power of 14.0 W with a pulse repetition frequency of 21.9 kHz and the corresponding diode-to-yellow conversion efficiency was 7.29%. The highest pulse energy of 56.2 μJ was obtained at a pump power of 7.2 W.     

Control of the pulse duration in a diode-pumped passively Q-switched intracavity frequency-doubling laser

Different techniques to control the pulse duration of a diode-pumped passively Q-switched intracavity frequency-doubled laser are studied, which shows that varying the pump beam radius in the gain medium and mode-spot sizes on a saturable absorber are two efficient ways to control the pulse duration. The output pulse durations obtained from a diode-pumped passively Q-switched Nd:GdVO₄/KTP laser with a GaAs wafer can be controlled in a wide range over 100 ns, which indicates a simple way of controlling the pulse duration of the intracavity frequency-doubled passively Q-switched laser.     

Diode-pumped Q-switched Nd:GdVO4/KTP green laser formed with a flat–flat resonator

A diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green laser formed with a flat–flat resonator was demonstrated. 3.05 W of average green output power at pulse repetition frequency (PRF) of 40 kHz was obtained with an optical conversion efficiency of 18.4%, the effective intracavity frequency-doubling efficiency was 57%. At the incident pump power of 15 W, the shortest laser pulse occurred at PRF of 25 kHz with FWHM width of 14 ns, yielding the highest peak power of 7.44 kW; while the largest pulse energy of 0.14 mJ was achieved at PRF of 15 kHz.     

Diode-pumped Q-switched intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>/KTP green laser

A simple and compact diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:LuVO₄/KTP green laser were demonstrated successfully for the first time. At an incident pump power of 6.5 W, an average output power of 663 mW, a pulse width of 26 ns were obtained with a PRF of 10 kHz. The pulse energy and peak power of the green light were determined to be 66.3 μJ and 2.55 kW, respectively.     

Diode-pumped passively Q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with a GaAs saturable absorber

By using a-cut Nd:Lu_0.15Y_0.85VO₄ mixed crystal as laser gain medium, a diode-pumped passively Q-switched and mode-locked (QML) laser with a GaAs saturable absorber in a Z-type folded cavity is demonstrated for the first time. The Q-switched mode-locked laser pulses with about 90% modulation depth are obtained as long as the pump power reached the oscillation threshold. The repetition rate of the passively Q-switched pulse envelope ranges from 50 to 186 kHz as the pump power increases from 0.915 to 6.520 W. Under an incident pump power of 6.52 W, the QML pulses with the largest average output power of 694 mW, the shortest pulse width of 200 ns and the highest pulse energy of 3.73 μJ are obtained. The mode-locked pulse width inside the Q-switched envelope is estimated to be about 275 ps. The experimental results show that Nd:Lu_0.15Y_0.85VO₄ is a promising mixed crystal for QML laser.     

Diode-pumped Q-switched laser with intracavity sum frequency mixing in periodically poled KTP

We report on a diode pumped Q-switched yellow-orange laser, with intracavity sum-frequency generation, in a periodically poled KTiOPO₄ crystal in a diode-pumped Q-switched dual-wavelength laser at 1064 and 1342 nm. The conversion efficiency is measured as a function of crystal temperature, incident pump power, and pulse repetition rate. Under optimal phase-matching conditions, the highest yellow-orange average power was 610 mW at a pump power of 17 W. PACS 42.60.Gd; 42.55.Rz; 42.55.Xi     

Highly efficient diode-pumped actively Q-switched Nd:YAG-SrWO(4) intracavity Raman laser

A highly efficient diode-pumped actively Q-switched intracavity Raman laser with SrWO(4) as the Raman-active medium is presented. As high as 23.8% diode-to-Stokes optical conversion efficiency is obtained with an incident pump power of 7.17 W and a pulse repetition rate of 15 kHz.     

Q-switched and mode-locked diode-pumped Nd:YVO4 laser with an intracavity composite semiconductor saturable absorber

We have demonstrated a passively Q-switched and mode-locked Nd:YVO₄ laser with an intracavity composite semiconductor saturable absorber (ICSSA). Stable Q-switched and mode-locked pulses with Q-switched envelope pulse duration of 180 ns and pulse repetition rate of 72 KHz have been obtained. The maximum average output power was 1.45 W at 8 W incident pump power. The repetition rate of the mode-locked pulses inside the Q-switched envelope was 154 MHz. Experimental results revealed that this ICSSA was suitable for Q-switched and mode-locked solid-state lasers.     

被动调Q自拉曼Nd∶GdVO4激光器

对激光二极管(LD)抽运的自拉曼Nd∶GdVO4被动调Q激光器进行了详细的理论和实验研究。实验中采用Nd∶GdVO4晶体同时作为激光介质和拉曼晶体,分别用了两块不同初始透射率的Cr4 ∶YAG晶体,得到并比较了采用不同初始透射率的Cr4 ∶YAG晶体时被动调Q自拉曼激光器的性能。测量了平均输出功率、脉冲宽度和脉冲重复率随抽运功率的变化关系。当Cr4 ∶YAG的初始透射率为0.91,输入功率是5.7 W时,得到的拉曼光的最高功率为244.6 mW,相应的转换效率为4.3%。通过数值求解基频光和拉曼光空间分布的速率方程并应用到被动调Q自拉曼Nd∶GdVO4激光器。获得的理论结果与实验结果大致相符。     

Diode-pumped passively Q-switched picosecond Nd:GDxY1-xVO4 self-stimulated raman laser

An efficiency of 8.2% is demonstrated for a diode-pumped passively Q-switched self-stimulated Raman laser with an a-cut mixed vanadate crystal, Nd:Gd0.8Y0.2VO4. At 2.2 W of incident pump power, the self-stimulated Raman laser produces pulses as short as 660 ps at a Stokes wavelength of 1175 nm with 2.7 microJ of energy per pulse at a 66-kHz repetition rate.     

LD-pumped passively Q-switched Nd:YVO/LBO red laser with V:YAG

An LD-pumped Nd:YVO₄ passively Q-switched by V:YAG and intracavity frequency doubled by LBO red pulse laser at 671 nm was presented. With 1.6 W incident pump power, average output power of 53 mW, pulse duration (FWHM) of 29.5 ns, pulse repetition rate of 37.2 kHz, peak power of 48.3 W and single-pulse energy of 1.43 μJ were obtained. The stability of pulse energy and repetition rate was better than 3% for 4 h.     

Eye-safe Raman laser at 1532 nm with BaWO<Subscript>4</Subscript> crystal

A diode-end-pumped actively Q-switched eye-safe intracavity Raman laser at 1532 nm is demonstrated, with Nd:YVO₄ as the laser crystal and BaWO₄ as the Raman crystal. The highest average power of 1.5 W is obtained, with an incident pump of 12 W and a pulse repetition rate of 35 kHz, corresponding to a diode-to-Stokes conversion efficiency of 12.5%.     

Passively Q-switched laser performance of a diode-pump mixed Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> crystal

A diode-pumped passively Q-switched Nd:Lu_0.15Y_0.85VO₄ laser with a GaAs output coupler is demonstrated. By using a mixed crystal Nd:Lu_0.15Y_0.85VO₄ as laser medium, the passively Q-switched laser can generate shorter pulse width with higher peak power in comparison with the passively Q-switched Nd:LuVO₄ or Nd:YVO₄ lasers under the same laser cavity. At the incident pump power 11.9 W, the minimum pulse width of 3.23 ns and the maximum peak power 1.67 kW can be obtained. The average output power and the pulse repetition rate of the laser are also measured. The experimental results show that the mixed crystal is a promising laser medium for shorter Q-switched pulse with higher peak power.     

Passive Q-switching performance with Co:LMA crystal in a diode-pumped Nd:LuVO<Subscript>4</Subscript> laser

A diode-pumped passively Q-switched Nd:LuVO₄ 1.34 μm laser using Co:LMA saturable absorber was successfully demonstrated. The average output power, pulse width, repetition rate of a-cut and c-cut Nd:LuVO₄ lasers were studied with different output couplers. The maximum average output power of 164 mW was obtained at the pump power of 10.3 W and the narrowest pulse width of 168 ns was achieved at repetition rate of 457 kHz under pump power of 8.59 W in a-cut Nd:LuVO₄ laser with T = 8%.     

Theoretical and experimental study of single mode-locking pulse generation with low repetition rate in a dual-loss-modulated QML YVO4/Nd:YVO4 laser with EO and GaAs

Using electro-optic (EO) modulator and GaAs saturable absorber, a diode-pumped doubly Q-switched and mode-locked (QML) YVO₄/Nd:YVO₄ laser at 1.06 μm is realized. The experimental results show that the number of the mode-locking pulses underneath the Q-switched envelope decreased with increasing pump power. With an output coupling of 6.5 %, the single mode-locking pulse underneath the Q-switched envelope with 1 kHz repetition rate was obtained when the pump power exceeded 4.65 W. At a pump power of 8.25 W for an output coupling of 10 %, a stable mode-locking pulse train at a repetition rate of 1 kHz was achieved with pulse energy as high as 582 μJ and pulse duration of about 580 ps, corresponding to a peak power of 1 MW. Using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled rate equations for diode-pumped doubly QML YVO₄/Nd:YVO₄ laser are given and the numerical solutions of the equations are basically in accordance with the experimental results.