Intracavity optical parametric oscillator at 1572-nm wavelength pumped by passively Q-switched diode-pumped Nd:YAG laser

An intracavity optical parametric oscillator (IOPO) based on bulk KTP crystal was constructed with a Nd:YAG slab as an active medium pumped by a 300-W diode array and Cr:YAG as a passive Q-switch. A signal pulse of 1.9-mJ energy at 1572-nm wavelength was demonstrated. In the cavity, optimized with respect to single-pulse energy, a five-fold shortening of signal-pulse duration with respect to 1064-nm pump radiation was observed. A twice as large level of signal peak power of 650 kW, compared to the pump laser in the same cavity without the IOPO, was achieved. A conversion efficiency of 44% with respect to the 1064-nm pump beam and 3.8% with respect to diode pump energy was demonstrated. Received: 15 October 2002 / Revised version: 19 February 2003 / Published online: 16 April 2003 RID="*" ID="*"Corresponding author. Fax: +48-22/666-8950, E-mail: wzendzian@wat.edu.pl     

Low threshold narrow pulse width eye-safe intracavity optical parametric oscillator at 1573 nm

We demonstrate a low threshold operation of a KTP-based intracavity optical parametric oscillator, emitting at 1573 nm, driven by a cw diode-end-pumped actively Q-switched Nd:YVO₄ laser. Diode-pump threshold around 0.86 W is achieved, which, to the best of our knowledge, is the lowest one under the similar experimental conditions. Owning to the efficient cavity-dumping effect, a signal pulse width as short as 1.4 ns and peak power higher than 3 kW is obtained, at the incident diode-pump power of 1.3 W and A-O modulating frequency of 9 kHz. Moreover, threshold characteristic for the IOPO is also studied, which is in well agreement with the experimental results.     

High-repetition-rate eye-safe optical parametric oscillator intracavity pumped by a diode-pumped Q-switched Nd:YVO<Subscript>4</Subscript> laser

A high-repetition-rate eye-safe optical parametric oscillator (OPO), using a non-critically phase-matched KTP crystal intracavity pumped by an acousto-optically (AO) Q-switchedNd:YVO₄ laser, is experimentally demonstrated. It is found that the average OPO signal power at 1573 nm can be efficiently increased by increasing the pulse repetition rate. Moreover, the intracavity OPO process effectively shortens the pulse width so that it is in the range 5∼8 ns for pulse repetition rates of 10 to 80 kHz. As a result of the relatively short pulse, the peak power at 1573 nm is higher than 2 kW at a pulse repetition rate of 80 kHz. Received: 10 July 2002 / Published online: 26 February 2003 RID="*" ID="*"Corresponding author. Fax: +886-35/729-134, E-mail: yfchen@cc.nctu.edu.tw     

Widely tunable optical parametric oscillator driven by a pulsed diode-pumped nonlinear-mirror mode-locked Nd:YAG laser

We report on the development of a pulsed diode end-pumped Nd:YAG laser mode-locked by a nonlinear mirror and stabilized by an acousto-optical modulator. With the introduction of appropriate intracavity loss, the laser is able to generate 22.8 ps pulses with the energy of 4.5 μJ. After amplification and frequency doubling stages, the second harmonic radiation is used to non-collinearly synchronously pump a β-barium borate optical parametric oscillator in a walk-off compensated scheme. The system demonstrates a wide-tuning range from 635 nm to 2.55 μm for the signal output, with maximum average conversion efficiency as high as 42%.     

Investigation of passively synchronized dual-wavelength Q-switched lasers based on V:YAG saturable absorber

In this paper the results of a theoretical and experimental investigation of synchronized passive Q-switching of two Nd:YVO₄-based solid-state lasers operating at two different wavelengths, is described. A V:YAG saturable absorbing material was used as a passive Q-switch performing the synchronization of the two laser fields. This material provides Q-switching operation at both 1064 and 1342 nm wavelengths simultaneously, saturating the same energy level. By adjusting the pump power of both lasers, it was possible to optimize the overlap of the two pulse trains and to switch between different states of synchronization. A theoretical model based on rate equations, which has been developed in order to investigate optical performance of the laser system, is in a good agreement with the experimental results. The principle of synchronized Q-switching can lead to new, pulsed all-solid-state light sources at new wavelengths based on sum-frequency mixing processes.     

A passively Q-switched Yb:YAG microchip laser

We present a diode-pumped passively Q-switched Yb:YAG microchip laser, using a semiconductor saturable absorber mirror. We obtained pulses with 1.1-μJ energy, 530-ps duration, 1.9-kW peak power, and a repetition rate of 12 kHz. The laser is oscillating in a single longitudinal mode. Received: 23 October 2000 / Published online: 7 February 2001     

Efficient passively Q-switched operation of a diode-pumped Nd:GGG laser with a Cr:YAG saturable absorber

The continuous-wave (cw) and passive Q-switching operation of a diode-end-pumped gadolinium gallium garnet doped with neodymium (Nd:GGG) laser at 1062 nm was realized. A maximum cw output power of 6.9 W was obtained. The corresponding optical conversion efficiency was 50.9%, and the slope efficiency was determined to be 51.4%. By using Cr⁴⁺:YAG crystals as saturable absorbers, Q-switching pulse with average output power of 1.28 W, pulse width of 4 ns and repetition rate of 6.2 kHz were obtained. The single-pulse energy and peak power were estimated to be 206 μJ and 51.6 kW, respectively. The conversion efficiency of the output power from cw to Q-switching operation was as high as 84.7%.     

High-repetition-rate eyesafe intracavity optical parametric oscillator

Received: 15 December 1997/Revised version: 27 April 1998     

Instability and satellite pulse of passively Q-switching Nd:LuVO4 laser with Cr:YAG saturable absorber

This work presents experimental results concerning a passively Q-switching Nd:LuVO₄ laser with a Cr⁴⁺:YAG saturable absorber operated in a three-element cavity. When the pump power exceeded 5.47 W, the system transfers stable pulse train into spatial-temporal instability. Furthermore, the chaotic pulse train accompanied the generation of a satellite pulse. The experimental results reveal that the mechanisms of instability and generation of the satellite pulse are governed by the multitransverse mode competition.     

Passively Q-switched diode-pumped Cr:YAG/Nd:GdVO4 monolithic microchip laser

The realization of high repetition rate passively Q-switched monolithic microlaser is a challenge since a decade. To achieve this goal, we report here on the first passively Q-switched diode-pumped microchip laser based on the association of a Nd:GdVO₄ crystal and a Cr⁴⁺:YAG saturable absorber. The monolithic design consists of 1 mm long 1% doped Nd:GdVO₄ optically contacted on a 0.4 mm long Cr⁴⁺:YAG leading to a plano-plano cavity. A repetition rate as high as 85 kHz is achieved. The average output power is approximately 400 mW for 2.2 W of absorbed pump power and the pulse length is 1.1 ns.     

Compact efficient diode-pumped Nd:YVO4 Q-switched blue laser with intracavity frequency tripling

We demonstrate a compact efficient diode-pumped acousto-optically Q-switched intracavity-frequency-tripled Nd:YVO₄ blue laser. The optimum polarization state is experimentally investigated to optimize the output performance. Greater than 280 mW of 447-nm average power at a repetition rate of 25 kHz was generated with a 15-W diode pump power. At 25 kHz, the pulse width is shorter than 15 ns and the peak power is higher than 800 W.     

Short pulse, high peak power, diode pumped, passively Q-switched 946 nm Nd:YAG laser

We report on generation of 946 nm laser pulses of a few nanosecond duration and up to 3.7 kW peak power from a compact diode-pumped passively Q-switched Nd:YAG laser. This power is 2.5 times as much as what previously has been obtained from this type of a laser. The short pulses with the record high peak power may be particularly attractive for laser range finding type applications.     

Diode-pumped passively Q-switched mode-locked Nd:YLF laser with uncoated GaAs saturable absorber

We have demonstrated passively Q-switched mode-locked all-solid-state Nd:YLF laser with an uncoated GaAs wafer as saturable absorber and output mirror simultaneously. Q-switched mode-locking pulses laser with about 100% modulation depth were obtained. The average output power is 890 mW at the incident pump power of 5.76 W, corresponding to an optical slop efficiency of 20%. The temporal duration of mode-locked pulses was about 21 ps. At the Q-switched repetition rate of 30 kHz, the energy and peak power of a single pulse near the maximum of the Q-switched envelope was estimated to be about 1.6 μJ and 76 kW.     

Observation of Antiphase State in a Self-Q-switched Nd,Cr:YAG Laser

We experimentally investigate the antiphase dynamics phenomenon in a self-Q-switched Nd, Cr：YAG laser operating at 946 nm. Due to the effect of spatial hole burning, the Q-switched pulses sequences of one, two and three modes at different pump power are observed. The experimental results show that the pulse sequences display classic antiphase dynamics.     

Pulse compression in AO Q-switched diode-pumped Nd:GdVO4 laser with Cr4+:YAG saturable absorber

By simultaneously using both an acoustic-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, for the first time, a diode-pumped doubly Q-switched Nd:GdVO₄ laser has been realized. The pulse duration is obviously compressed in contrast to the actively acoustic-optic Q-switched laser. By considering the Gaussian transversal distribution of the intracavity photon density and the longitudinal distribution of the photon density along the cavity axis as well as the influence of turnoff time of the acoustic-optic (AO) Q-switch, we provide the coupled rate equations for a diode-pumped doubly Q-switched Nd:GdVO₄ laser with both an acoustic-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber. These coupled rate equations are solved numerically, and the dependence of pulse width, pulse energy and peak power on the incident pump power at different pulse repetition rates is obtained. The numerical solutions of equations agree well with the experimental results.This revised version was published online in August 2005 with a corrected cover date.     

Passively Q-switched Nd:YAG pumped UV lasers at 280 and 374 nm

Pulsed UV lasers at the wavelengths of 374 and 280 nm are realized by cascaded second harmonic generation (SHG) and sum frequency generation (SFG) processes using a Nd:YAG laser at 1123 nm. The Nd:YAG laser is longitudinally pumped and passively Q-switched, and it has a high peak power of 3.2 kW. The UV peak powers at 280 and 374 nm are 100 and 310 W, with pulse lengths of 6 and 8 ns, respectively. Spectral broadening of 374 nm laser by stimulated Raman scattering is studied in single mode pure silica core UV fiber. Realizations of UV lasers enabling compact design at 280 and 374 nm wavelengths are demonstrated.     

Short pulse passively Q-switched Nd:GdYVO4 laser using a GaAs mirror

We report on a diode pumped passively Q-switched Nd:Gd_0.64Y_0.36VO₄ laser with a Cr⁴⁺:YAG saturable absorber. We show experimentally that by using an appropriately coated GaAs wafer as output coupler, the Q-switched pulse width can be significantly suppressed. Stable Q-switched pulse train with pulse width of 2.2 ns, peak power of 26.3 kW, repetition rate of 15.38 kHz have been obtained under an absorbed pump power of 8.54 W. The physical mechanism of pulse width narrowing by the GaAs wafer was also experimentally investigated.     

Diode-pumped passively Q-switched Nd:LuVO4 laser at 916 nm

We demonstrate a passively Q-switched Nd:LuVO₄ laser at 916 nm by using a Nd, Cr:YAG crystal as the saturable absorber. As we know, it is the first time to realize the laser with a simple linear resonator. When the incident pump power increased from 14.6 W to 23.7 W, the pulse width of the Q-switched laser decreased from 24 ns to 21 ns. The pulse width was insensitive to the incident pump power in the experiment. The average output power of 288 mW with repetition rate of 39 kHz was obtained at an incident pump power of 22.5 W, with the optical-to-optical efficiency and slope efficiency 1.3% and 3.6%, respectively.     

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.     

Diode end-pumped Q-switched high-power intracavity frequency-doubled Nd:GdVO4/KTP green laser

A diode-laser-array end-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green laser, formed with a three-mirror folded resonator, has been demonstrated. With 15 W of pump power incident upon the Nd:GdVO₄ crystal, a maximum average green output power of 3.75 W was obtained at 50 kHz of pulse repetition frequency, giving an optical conversion efficiency of 25%, whereas the effective intracavity frequency-doubling efficiency was determined to be 72%. At the incident pump power of 12.8 W, the shortest laser pulse was achieved at a pulse repetition rate of 10 kHz, the resulting pulse width, single pulse energy, and peak power were measured to be 35 ns, 108 μJ, and 3.1 kW, respectively. Received: 18 May 2000 / Published online: 20 September 2000