Diode-pumped doubly Q-switched Nd:GdVO<Subscript>4</Subscript> laser

By using both an acoustooptical (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, a diode-pumped doubly Q-switched Nd:GdVO₄ laser, which can generate short pulses with high peak powers and symmetric temporal profiles, has been demonstrated. A peak power of 3.05 kW with a corresponding pulse width of 16 ns has been achieved at an incident pump power of 7.7 W. A reasonable analysis about the experimental results has been given by considering the ground-state absorption and excited-state absorption of a Cr⁴⁺:YAG crystal.     

Diode-pumped Actively Q-switched Nd:GdVO<Subscript>4</Subscript> Green Laser with Periodically Poled KTP

A diode-pumped actively Q-switched Nd:GdVO₄ green laser with periodically poled KTP (PPKTP) and Acoustic-optic (AO) modulator has been realized. The dependences of pulse energy, pulse width, and peak power on incident pump power are measured. At the pump power of 4.1 W and repetition rate of 10 kHZ, we can obtain a 19.2 ns pulse with pulse energy of 0.11 mJ and peak power of 5.8 kW, which are almost three times of that in the conventional KTP green laser, respectively. A rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the Gaussian spatial distribution of the intracavity photon density is taken into account. The numerical solutions of the rate equations agree with the experimental results.     

Diode-pumped passively mode-locked Nd:GdVO<Subscript>4</Subscript> laser with a GaAs saturable absorber mirror

We report on a diode end-pumped passively mode-locked Nd:GdVO₄ laser. By using a GaAs wafer simultaneously as the saturable absorber and the output coupler, stable continuous-wave mode locking was achieved. The pulse width was measured to be 18.9 picoseconds at a repetition rate of 370 MHz. The most remarkable property of the laser is that its repetition rate can be changed from 370 MHz to 3.348 GHz by simply changing the cavity length. An average output power of 3.46 W at a 3.348 GHz repetition rate was obtained with a 14 W pump power. To our knowledge, this is the first demonstration of a passively mode-locked Nd:GdVO₄ laser using a GaAs wafer as the saturable absorber. PACS 42.55.Rz; 42.60.Fc; 42.55.Xi.     

Analytical and experimental studies on the diode-pumped,simultaneously Q-switched and mode-locked c-cut Nd:GdVO<Subscript> 4</Subscript>/KTP green laser with LT-GaAs absorber

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency doubled c-cut Nd:GdVO₄/KTP green laser with a LT-GaAs saturable absorber is presented. More than 90% modulation depth for the mode-locked green pulses has been achieved. Using the hyperbolic secant function methods, a developed rate equation model for Q-switched and mode-locked lasers considering the Gaussian spatial distribution of the intracavity photon intensity, the influences of continuous pump rate, the upper state lifetime of the active medium, and the excited-state lifetime of the saturable absorber, was proposed. With this developed model, the theoretical results are in good agreement with the experimental results and the width of the mode-locked green pulse was estimated to be about 380 ps.     

Cavity-dumped mode-locked Nd:GdVO<Subscript>4</Subscript> laser at low repetition rate

We report a cavity-dumped mode-locked Nd:GdVO₄ laser with semiconductor saturable absorber mirrors at low repetition rate. In this laser system, a single mode-locked laser pulse is generated, amplified and cavity-dumped by means of electro-optic modulator at 1 to 10 Hz repetition rate. The energy of the pulse is about 150 nJ and the pulse duration is determined to be 10 ps.     

Diode single-end-pumped AO Q-switched Nd:GdVO<Subscript>4</Subscript> 266 nm laser

By simple extra-cavity frequency conversion, the performance of a diode single-end-pumped AO Q-switched Nd:GdVO₄/KTP/BBO 266 nm laser was demonstrated. Under the incident pump power of 14.32 W, the maximum average output power at 266 nm was 374 mW at the repetition of 20 kHz; the opticaloptical conversion efficiency was 2.6%. The corresponding pulse width was 5 ns, with the single-pulse energy and peak power calculated to be 18.7 μJ and 3.74 kW, respectively. The dependence of the operational parameters on the pump power was also investigated experimentally.     

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 short pulse passively Q-switched 912 nm Nd:GdVO<Subscript>4</Subscript>/Cr:YAG laser at high repetition rate operation

A diode-end-pumped passively Q-switched 912 nm Nd:GdVO₄/Cr:YAG laser is demonstrated for the first time. In a concave-piano cavity, pulsed 912 nm laser performance is investigated using two kinds of Cr:YAG crystal with different unsaturated transmission (T _U) of 95% and 90% at 912 nm as the saturable absorbers. When the T _U = 90% Cr:YAG is used, as much as 2.6 W average output power for short pulsed 912 nm laser is achieved at an absorbed pump power of 34.0 W, corresponding to an optical efficiency of 7.6% and a slope efficiency of 20.3%. Moreover, 10.5 ns duration pulses and up to 2.3 kW peak power is obtained at the repetition rate around 81.6 kHz.     

AlGaInAs/InP eye-safe laser pumped by a Q-switched Nd:GdVO<Subscript>4</Subscript> laser

An AlGaInAs quantum-well structure grown on a Fe-doped InP transparent substrate is developed to be a gain medium in a high-peak-power nanosecond laser at 1570 nm. Using an actively Q-witched 1064 nm laser to pump the gain chip, an average output power of 135 mW is generated at a pulse repetition rate of 30 kHz and an average pump power of 1.25 W. At a pulse repetition rate of 20 kHz, the peak output power is up to 290 W at a peak pump power of 2.3 kW.     

Diode-pumped passively Q-switched and Q-switch mode-locked Nd:YVO<Subscript>4</Subscript> laser using single-wall carbon nanotube based saturable absorber

We present the performance of diode end-pumped Nd:YVO₄ laser in Q-switched and Q-switched mode-locking oscillation using a single-walled carbon nanotube based saturable absorber, which was fabricated using similar vertical evaporation technique. The average output power, repetition rate and pulse width of the Q-switched laser output were studied with different output couplers. The maximum average output power was 130 mW. For Q-switched mode-locking operation, the repetition rate of the mode-locked pulses concentrated in the Q-switched envelope was 58 MHz. The repetition rate of the Q-switched envelope maintained at 18 kHz, while the pulse width decreased along with the increasing of pump power. The maximum average output power was 53 mW.     

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 Tm:GdVO<Subscript>4</Subscript> lasers with double etalons

Diode end-pumped single-frequency Tm:GdVO₄ laser at room temperature was reported. The maximal output power of single-frequency is as high as 51 mW by using two uncoated fused YAG etalons, which are respectively 0.05 mm thick and 1 mm thick. We obtained the single frequency Tm:GdVO₄ laser at 1919.7 nm. The slope efficiency is 1.4%. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

Theoretical and experimental studies on the self-Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/KTP green laser

A diode-pumped self-Q-switched and mode-locked intracavity frequency doubled Nd:GdVO₄/KTP green laser is presented. The self mode-locking is self-starting and stable. About 100% modulation depth for the self-mode-locked green pulses has been achieved. We propose a developed rate equation model for self-Q-switched and mode-locked lasers, using the hyperbolic secant function methods and the theory of Kerr-lens mode-locking. This will consider the cascading of second-order nonlinearities of KTP crystal, the third-order nonlinearity of the laser medium, influences of the continuous pump rate, and the stimulated radiation lifetime of the active medium. With the model developed, theoretical calculations are shown to be in good agreement with experimental results. The width of the mode-locked green pulse is estimated to be about 120 ps. PACS 42.60.Fc; 42.60.Gd; 42.65.Hw     

Compact efficient self-frequency Raman conversion in diode-pumped passively Q-switched Nd:GdVO<Subscript>4</Subscript> laser

I report the first demonstration of the generation of efficient sub-nanosecond self-stimulated Raman pulses by a diode-pumped passively Q-switched Nd:GdVO₄/Cr⁴⁺:YAG laser. The conversion efficiency for the average power is 7% from pump diode input to self-Raman output and the slope efficiency is up to 14%. At an incident pump power of 2.0 W, the pulse duration, pulse energy, and peak power for the Stokes wavelength of 1175.6 nm were found to be 750 ps, 6.3 J, and 8.4 kW, respectively, with a pulse-repetition rate of 22 kHz. PACS 42.55.Ye; 42.55.Xi; 42.60.Gd     

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 mode-locked Nd:CaNb<Subscript>2</Subscript>O<Subscript>6</Subscript> laser

We have experimentally demonstrated a diode-pumped passively mode-locked Nd:CaNb₂O₆ laser for the first time to our best knowledge. With a semiconductor saturable absorber mirror (SESAM) as a passive mode locker, the laser generated stable mode-locked pulses with pulse duration of 17.3 ps and repetition rate of 88.4 MHz. With a singe-emitter laser diode pumping, the maximum average output power of the mode-locked laser was 0.843 W, with a slope efficiency of 23%. The experimental results show the Nd:CaNb₂O₆ crystal is a promising laser gain medium for picosecond pulse generation.     

Diode-pumped Nd:YVO<Subscript>4</Subscript> intracavity-doubled red laser at 693 nm

It is reported that efficient continuous-wave (CW) red laser generation at 693 nm in a LBO crystal at type-I phase matching direction performed with a diode-pumped Nd:YVO₄ laser. With incident pump power of 18.2 W, output power of 278 mW at 693 nm has been obtained using a 10 mm-long LBO crystal. At the output power level of 278 mW, the output stability is better than 2.9%.     

Comparison of electro-optical and acousto-optical Q-switched,high repetition rate Nd:GdVO<Subscript>4</Subscript> laser

The differences between the performances of electro-optical (EO) and acousto-optical (AO) Q-switched, diode pumped Nd:GdVO₄ laser at high repetition rates were detailed in this paper. The results revealed that EO Q-switch was more favorable to obtain short pulse width and high peak power laser than AO Q-switch under high repetition rate operation. The minimum pulse widths at 100 kHz were 20.2 ns under EO operation and 28.7 ns under AO operation, corresponding to peak powers of 3.1 kW and 2.2 kW, respectively. The corresponding values at 10 kHz were 5.3 ns, 9.0 ns and 77.4 kW, 45.6 kW, respectively.     

Diode-pumped high-repetition-rate acousto-optically Q-switched Nd:YVO<Subscript>4</Subscript> laser operating at 914 nm

A diode-pumped high-repetition-rate acousto-optically (A-O) Q-switched Nd:YVO₄ laser operating at 914 nm was reported in this paper. Employing a compact linear laser cavity, at an operating repetition rate of 10 kHz, a maximum average output power of 2.2 W 914 nm laser was obtained at an incident pump power of 45.3 W, corresponding to an optical conversion efficiency of 4.9% and a slope efficiency of 8.8%. Minimum pulse width of 24 ns and maximum peak power of 8.0 kW of 914 nm laser was also achieved at an incident pump power of 40.8 W. To the best of our knowledge, this is the highest peak power of 914 nm laser at 10 kHz by far. Moreover, the highest operating repetition rate of pulsed 914 nm can even reach 100 kHz.     

Actively Q-switched intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>/LBO green laser with an acousto-optic modulator

This work presents experimental results concerning an actively Q-switched intracavity frequency-doubled Nd:LuVO₄/LBO green laser with an acousto-optic modulator operated at the wavelength of 0.53 μm. The green average output power of 2.8 W was obtained at a pump power of 16.3 W and a pulse repetition rate of 20 kHz, resulting in an optical conversion efficiency of 17%. When the pulse repetition rate is operated at 5 kHz, the shortest pulse width and the highest peak power at 0.53 μm were measured to be 26.5 ns and 8.43 kW, respectively.