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-end-pumped passively Q-switched 1319 nm Nd:YAG ceramic laser with a V<Superscript>3+</Superscript>:YAG saturable absorber

The performance of a LD-end-pumped passively Q-switched Nd:YAG ceramic laser at 1319 nm with a V³⁺:YAG saturable absorber was demonstrated for the first time to the best of our knowledge. The average output power of 1.8 W was obtained under the pump power of 23.7 W, corresponding to the optical conversion efficiency of 7.8% and slope efficiency of 9%. The minimum pulse width was 128 ns with the pulse repetition rate of 230 kHz, which was attained with a T = 2.8% output coupler at the pump power of 23.7 W.     

Analysis of a laser-diode end-pumped passively Q-switched Nd:GdVO4 laser with V3+:YAG saturable absorber

By considering both the transversal and longitudinal Gaussian spatial distribution of the intracavity photon density, a couple of rate equations describing a laser-diode end-pumped passively Q-switched Nd:GdVO₄ laser with V³⁺:YAG saturable absorber have been proposed. Solving these space-dependent rate equations numerically, we obtain the dependences of pulse width, pulse repetition rate, single-pulse energy and peak power on pump power. In the experiment, a laser-diode end-pumped Nd:GdVO₄ laser passively Q-switched by a V³⁺:YAG saturable absorber has been realized, and the experimental results are consistent with the theoretical calculations.     

Diode end-pumped passively Q-switched Nd:YAG ceramic laser with Cr4+:YAG saturable absorber

We report on a diode end-pumped passively Q-switched Nd:YAG ceramic laser. By using a Cr⁴⁺:YAG single crystal with an 80% initial transmission as the saturable absorber, stable Q-switched pulses with a 126-μJ pulse energy, a 12-ns pulse width, and an 8.4-kHz pulse repetition rate have been obtained. The Q-switching performance of the laser under different saturable absorption strengths and output couplings was experimentally investigated.     

Pulse compression in diode-pumped doubly Q-switched Nd:GdVO<Subscript>4</Subscript> laser with both V<Superscript>3+</Superscript>:YAG and Co<Superscript>2+</Superscript>:LMA saturable absorber

By simultaneously using both a V³⁺:YAG and a Co²⁺:LaMgAl₁₁O₁₉ saturable absorber in the cavity, for the first time to our knowledge, a diode-pumped doubly Q-switched Nd:GdVO₄ laser has been realized. The dependence of pulse width, pulse repetition rate, pulse energy and peak power on the incident pump power are measured. Under the absorbed pump power of 8.59 W, both the pulse temporal profile of the passive double-switching with the pulse width of 25.29 ns, and the passive single-switching just using V³⁺:YAG with pulse width of 30.46 ns are obtained. The pulse duration is partly compressed in contrast to the purely passively Q-switched laser with V³⁺:YAG.     

Analysis of laser-diode end-pumped intracavity frequency-doubled,passively Q-switched and mode-locked Nd:YVO<Subscript>4</Subscript> laser

Simultaneous Q-switching and mode locking in a laser-diode end-pumped intracavity frequency-doubled Nd:YVO₄/KTP green laser using a Cr⁴⁺:YAG saturable absorber with 81% initial transmission is experimentally demonstrated. At an incident pump power of 6 W, 300 mW of average green power was obtained, which is around four times higher than the cw green power obtained without the Cr⁴⁺:YAG crystal. The repetition rate of the mode-locked green pulses was 400 MHz and the individual mode-locked pulse width was measured to be 500 ps. The repetition rate of the Q-sw itched envelope of the mode-locked pulses was 15 kHz at 6 W of incident pump power. The energy of the mode-locked pulse at the peak of the Q-sw itched envelope was estimated to be 1 J and the peak power was estimated to be 2.4 kW. The measured width and the total energy of the Q-sw itched envelope of the mode-locked pulses was 47 ns and 21 J, respectively, at the maximum incident pump power. An analysis of the system by incorporating a nonlinear loss term due to the intracavity second-harmonic generation to the general recurrence relation for the mode-locked pulses under the Q-sw itched envelope at the fundamental wavelength has been presented. Using a hyperbolic secant square function to model the mode-locked pulse, the temporal shape of a single Q-sw itched pulse at the second-harmonic wavelength has been reconstructed. The theoretical calculations of the pulse parameters like pulse energy, peak power, pulse width and pulse-symmetry factor have shown fairly good agreement with the experimental results. PACS 42.55.Rz; 42.55.Xi; 42.60.By     

Passively Q-switched intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>/LBO green laser with a Cr<Superscript>4+</Superscript>:YAG saturable absorber

This work presents experimental results concerning a passively Q-switched intracavity frequencydoubled Nd:LuVO₄/LBO green laser with a Cr⁴⁺:YAG saturable absorber operated at the wavelength of 0.53 μm. A maximal output power of 1.28 W was obtained at a pump power of 16.34 W, and peak power, pulse width as well as repetition frequency were 1.48 kW, 41 ns and 21 kHz, respectively.     

Dual-wavelength oscillation at 1064 and 1342 nm in a passively Q-switched Nd:YVO<Subscript>4</Subscript> laser with V<Superscript>3+</Superscript>:YAG as saturable absorber

The efficient dual-wavelength oscillation at 1064 and 1342 nm in the passively Q-switched laser based on Nd:YVO₄/V³⁺:YAG is successfully obtained, as demonstrated in this paper. A total average output power of 2.2 W is obtained with 1.3 W for 1064 nm and 0.9 W for 1342 nm under the incident pump power of 7.7 W, corresponding to a total optical-optical conversion efficiency of 28.2%. The pulse widths are 58 and 54 ns for 1064 and 1342 nm, respectively, with the repetition rate of 89 kHz. Moreover, a rate equation model considering the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density is presented to characterize the dual-wavelength passive Q-switching operation.     

LD-pumped passively Q-switched Nd:GdVO<Subscript>4</Subscript> laser at 1342 nm with high initial transmission V:YAG saturable absorber

We have realized, for the first time to our knowledge, the passive Q-switching operation of an LD-pumped Nd:GdVO₄ laser at 1342 nm with V:YAG saturable absorber of initial transmission as high as 96%. This laser is investigated under different transmissions of the output coupler. The dependences of average output power, pulse width, pulse repetition rate, single-pulse energy and peak power on incident pump power are also measured. The shortest pulse width of 80 ns, the maximum single-pulse energy of 19.5 μJ and the highest peak power of 244 W are obtained with the output coupler of T = 15% and the pump power of 7.93 W. We find a special experimental phenomenon that the pulse repetition rate begins to drop after reaching the peak with the increase of the pump power. This phenomenon is analyzed and the theoretical calculations are consistent with the experimental results.     

Passively Q-switched GdVO<Subscript>4</Subscript>/Nd:GdVO<Subscript>4</Subscript> laser with Cr<Superscript>4+</Superscript>:YAG saturable absorber under direct 879 nm diode pumping to the emitting level

A passively Q-switched 1.06 μm laser with Cr⁴⁺:YAG saturable absorber by direct 879 nm diode pumping grown-together composite GdVO₄/Nd:GdVO₄ crystal to the emitting level was demonstrated in this paper. The characteristics of pulsed laser were investigated by using two kinds of Cr⁴⁺:YAG crystal with the initial transmissivity of 80 and 90%, respectively. When the T ₀ = 90% Cr⁴⁺:YAG was used, an average output power of 1.59 W was achieved at an incident pump power of 10 W. The pulse width and repetition rate were 64.5 ns and 170 kHz, respectively. The thermal lens effect of laser crystal was analyzed.     

High repetition rate passive Q-switching of diode-pumped Nd:GdVO<Subscript>4</Subscript> laser at 912 nm with V<Superscript>3+</Superscript>:YAG as the saturable absorber

The character of a diode-pumped passively Q-switched Nd:GdVO₄/V³⁺:YAG 912 nm laser was demonstrated for the first time to our knowledge. With an absorbed pump power of 7.4 W, an average output power of 360 mW with a Q-switched pulse width of 328 ns at a pulse repetition rate of 163 kHz was obtained. The Q-switching efficiency was found to be 32.7%. Our work further indicated V³⁺:YAG could be an effective fast passive Q-switch for 0.9 μm radiation.     

Doubly passively Q-switched laser with V<Superscript>3+</Superscript>:YAG and Co:LMA saturable absorbers

By using both V³⁺:YAG and Co:LMA saturable absorbers, a doubly passively Q-switched laser is realized for the first time. The shorter pulse with the higher peak power is generated in comparison to the singly passively Q-switched laser with V³⁺:YAG or Co:LMA saturable absorber. The experimental results shows that it is possible to obtain a shorter pulse with the higher peak power in a doubly passively Q-switched laser.     

A high beam quality laser-diode end-pumped Nd:GdVO<Subscript>4</Subscript> slab laser

An 83 W, near-diffraction-limited LD end-pumped Nd:GdVO₄ slab laser with hybrid resonator was presented with the pumping power of 238 W, the slope efficiency and optical-to-optical conversion efficiency were 39.4 and 34.9%, respectively. At the output power of 70 W, beam quality M² factors were 1.2 in stable direction and 1.3 in unstable direction.     

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.     

Millijoule intracavity OPO driven by a passively Q-switched Nd:YVO<Subscript>4</Subscript> laser with AlGaInAs quantum-well saturable absorber

We originally demonstrate the use of an AlGaInAs periodic quantum-well absorber to achieve a quasi-continuous-wave (QCW) diode-pumped passively Q-switched Nd:YVO₄ laser with an intracavity optical parametric oscillator (OPO). With a diode-pumping energy of 35 mJ, the output pulse energy and the pulse width at 1573 nm are found to be 1.58 mJ and 26 ns, respectively. The pulse repetition rate can be up to 100 Hz with the overall OPO beam quality M² factor to be better than 1.5.     

Doubly passively Q-switched and mode-locked laser with V<Superscript>3+</Superscript>:YAG and Co:LMA saturable absorbers

By using both V³⁺:YAG and Co:LMA saturable absorbers, an xenon-lamp-pumped doubly passively Q-switched and mode-locked (QML) Nd:YAG laser at 1.3 μm in a straight cavity is realized for the first time. The modulation depth of QML pulse has nearly reached 100%. The experimental results shows that the doubly passively Q-switched and mode-locked (QML) laser can generate shorter Q-switch envelope pulse with higher average peak power in comparison to the singly passively QML laser with V³⁺:YAG or Co:LMA saturable absorber.     

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 Nd:YVO<Subscript>4</Subscript> laser with a carbon nanotube saturable absorber

A diode end-pumped passively Q-switched Nd:YVO₄ laser with a transmission-type single-walled carbon nanotube saturable absorber is first demonstrated in this paper. The maximum continuous wave (CW) output power of 477 mW is obtained at the incident pump power of 1490 mW with the output transmission T = 10%, resulting in slope efficiency of 41.3%. For Q-switching operation, the measured pulse duration of 332 ns, the pulse energy of 326 nJ and the peak power of 982 mW are respectively obtained.     

Transverse mode locking of Stokes radiation in diode end-pumped Nd:YVO<Subscript>4</Subscript> laser passively Q-switched by Cr<Superscript>4+</Superscript>:YAG

Transverse mode locking of the Stokes component generated in the mode of stimulated Raman scattering self-conversion by a pulsed diode end-pumped Nd:YVO₄/Cr:YAG laser is implemented for the first time under conditions of frequency degeneracy of cavity modes.     

Control of the pulse width in a diode-pumped passively Q-switched Nd:YVO<Subscript>4</Subscript>/KTP green laser with GaAs saturable absorber

By varying the positions of the saturable absorber in the laser axis and the pump beam waist in the gain medium, respectively, we have theoretically and experimentally studied the control of the pulse width in a diode-pumped passively Q-switched Nd:YVO₄/KTP green laser with GaAs saturable absorber. A rate equation model is introduced, in which the intracavity photon density is assumed to be Gaussian spatial distribution, the longitudinal variation of the intracavity photon density and the pump beam spatial distribution are also considered. The experimental results are consistent with the numerical calculations of the rate equations.