1.3-ns pulse,compact passively Q-switched microchip green laser by Nd:YAG/Cr<Superscript>4+</Superscript>:YAG composite crystal

In this article, a diode-end-pumped passively Q-switched extra-cavity frequency doubled micro-type green laser by Nd:YAG/Cr⁴⁺:YAG composite crystal was demonstrated. The dependence of the average out power, pulse width and pulse repetition rate on incident pump power were measured. Under the pump power of 14 W, the minimum pulse width of 1.3 ns with repetition rate of 68.0 kHz was obtained, corresponding single-pulse energy of 8.8 μJ and peak power of 6.7 kW.     

Dual-wavelength generation at the transverse mode locking in a diode-end-pumped passively Q-switched Nd:YLF/Cr<Superscript>4+</Superscript>:YAG laser

A dual-wavelength generation at 1047 and 1053 nm is implemented in a diode-endpumped Nd:YLF laser Q-switched by Cr:YAG. This generation is obtained by the tuning of the cavity length near the regions of the transverse-mode degeneracy.     

Experimental study on passively Q-switched mode-locking diode-pumped Nd:KGW laser with Cr4+:YAG

A diode-pumped passively Q-switched and mode-locked Nd:KGW/Cr⁴⁺:YAG laser with different output couples is realized in a V-type folded cavity. About 85% modulation depth for the mode-locked pulses has been obtained. The repetition rate of the mode-locked pulses inside the Q-switched envelope was about 798 MHz.     

Single diode-pumped, 1.7 ns microchip laser by Nd:YAG/Cr<Superscript>4+</Superscript>:YAG composite crystal

A single diode-pumped passively Q-switched composite Nd:YAG/Cr⁴⁺:YAG laser, which cavity mirrors were deposited directly onto the crystal, was demonstrated in this paper. At the incident power of 2.75 W, the maximum average output power of 365 mW and the shortest pulse width of 1.7 ns were obtained, corresponding the repetition rate of 14.6 kHz. The single-pulse energy and the peak power were estimated to be 25 μJ and 14 kW, respectively. The corresponding optical-optical conversion efficiency was 13.3%.     

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.     

High-peak power,passively Q-switched,composite, all-poly-crystalline ceramics Nd:YAG/Cr<Superscript>4+</Superscript>:YAG laser and generation of 532-nm green light

Output performances of passively Q-switched, composite Nd:YAG/Cr⁴⁺:YAG lasers that consisted of bonded, all-poly-crystalline ceramics Nd:YAG and Cr⁴⁺:YAG are reported. Laser pulses at 1.06 μm with 2.5-mJ energy and 1.9-MW peak power are obtained from a 1.1-at % Nd:YAG/Cr⁴⁺:YAG ceramics that was quasi-continuous-wave (quasi-CW) pumped with a diode laser. Single-pass frequency doubling with LiB₃O₅ (LBO) nonlinear crystal at room temperature yielded green laser pulses at 532 nm of 0.36-mJ energy and 0.3-MW peak power, with a conversion efficiency of 0.27.     

Optimization of Yb:YAG/Cr<Superscript>4+</Superscript>:YAG composite ceramics passively Q-switched microchip lasers

The laser characteristics of laser-diode end-pumped Yb:YAG/Cr⁴⁺:YAG composite ceramics microchip passively Q-switched lasers were studied by solving the coupled rate equations numerically taking into account the reabsorption of Yb:YAG ceramics at laser wavelength. Effects of the reflectivity of the output coupler, the concentrations and thickness of the saturable absorbers, and pump beam area on the laser performance were investigated analytically. The simulation results of the Yb:YAG/Cr⁴⁺:YAG composite ceramics passively Q-switched microchip lasers were in good agreement with the experimental data. Better laser performance (high peak power, short pulse width and good optical-to-optical efficiency) of the composite Yb:YAG/Cr⁴⁺:YAG ceramics passively Q-switched laser can be obtained by using a thin Cr⁴⁺:YAG ceramic with high concentration, suitable reflectivity of the output coupler and proper pump beam diameter under high pump power intensity according to our simulations.     

Self-starting five optical cycle pulse generation in Cr<Superscript>4+</Superscript>:YAG laser

We report stable self-starting near-transform-limited 26-fs pulses at 250-mW output power from a Kerr-lens mode-locked (KLM) Cr⁴⁺:YAG laser using chirped mirrors in combination with prisms. The highest output power achieved in KLM regime was 600 mW at 55-fs pulse duration. The experimental results agree well with the results of theoretical analysis with respect to KLM self-starting ability and stability against continuous-wave and multi-pulse operation. Parameter ranges for stable transform-limited KLM pulses as well as the shortest achievable pulse durations are established. Using an InGaAs-InP semiconductor saturable absorber mirror we could obtain self-starting 57-fs pulses at the average output power of 200 mW. Two-photon absorption was found to be the main mechanism favoring the multiple-pulse operation. Received: 2 May 2002 / Revised version: 16 July 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +43-1/58801-38799, E-mail: sorokina@tuwien.ac.at     

High-temperature operation of a diode-pumped passively Q-switched Nd:YAG/Cr4+:YAG laser

The output performances of a diode-pumped Nd:YAG laser passively Q-switched by Cr⁴⁺:YAG saturable absorber crystal were investigated function of temperature. Increase of the temperature from 25 to 150°C increased slightly the laser pulse energy, and did not change the pulse duration. Furthermore, an increased absorbed energy of the pump radiation was necessary at temperatures higher than 25°C in order to maintain Q-switch operation. Measurements concluded that Cr⁴⁺:YAG transmission did not vary when temperature increased to 150°C. The decrease of Nd:YAG emission cross section with temperature and the changes of resonator configuration due to thermal effects were considered as main reasons for this behavior. The results of this work are valuable for designing a laser-ignition system for industrial gas engine or automotive industry.     

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.     

Efficient diode-pumped actively Q-switched Nd:YAG/BaWO4 intracavity Raman laser

Barium tungstate (BaWO4) is employed to achieve efficient stimulated Raman scattering conversion in a compact diode-pumped actively Q-switched Nd:YAG laser. With an incident pump power of 9.2 W, 1.56 W of 1181 nm first-Stokes average output power was generated at a pulse repetition rate of 20 kHz, corresponding to an optical-to-optical conversion efficiency of 16.9%.     

Single-mode high-peak-power passively Q-switched diode-pumped Nd:YAG laser

We have demonstrated an efficient, compact, passively Q-switched single-mode diode-pumped Nd:YAG laser that uses Cr(4+):YAG as a saturable absorber. Linear- and ring-cavity configurations were demonstrated. Pulse energies and widths were, respectively, 1.5mJ and 3.9ns for the linear cavity and 2.1mJ and 12ns for the ring cavity.     

High-peak-power diode-pumped passively Q-switched Nd:YVO<Subscript>4</Subscript> laser

We report on a passively Q-switched diode-pumped Nd:YVO₄ laser polarized along the a axis (corresponding to the smallest value of emission cross section at 1064 nm), generating 157-μJ pulses with 6.0-ns time duration (>20 kW peak power) and 3.6 W of average power at 1064 nm with good beam quality (M²<1.4). The selection of the polarization was performed by a novel technique relying on the birefringence of the laser crystal and on the misalignment sensitivity of the resonator. Received: 30 September 2002 / Revised version: 22 November 2002 / Published online: 19 March 2003 RID="*" ID="*"Corresponding author. Fax: +39-382/422583, E-mail: agnesi@ele.unipv.it     

A laser-diode end-pumped passively Q-switched intracavity doubling Nd:GdVO<Subscript>4</Subscript>/KTP red laser with V<Superscript>3+</Superscript>:YAG saturable absorber

Using a V³⁺:YAG saturable absorber, we realize the running of a laser-diode end-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO₄/KTP red laser. Under the absorbed pump power of 9.45 W and with V³⁺:YAG initial transmission T ₀ = 94%, the obtained average output power and pulse width were 610 mW and 15.09 ns with the repetition rate of 12.2 kHz, corresponding to the single pulse energy 50 μJ and the pulse peak power 3.34 kW.     

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.     

Timing-jitter reduced high-repetition-rate Q-switched Nd:YVO<Subscript>4</Subscript>/Cr<Superscript>4+</Superscript>:YAG micro laser with low pump power

We report a high repetition rate Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser with small pump power. Unwanted defects in pulse train, which are inherently large in passively Q-switched laser, was simply minimized by controlling temperature of Nd:YVO₄/Cr⁴⁺:YAG medium. When T ₀ = 90% Cr⁴⁺:YAG and R _OC = 90% output coupler were used, Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser showed the optimum output; maximum output power of 58 mW, optical-to-optical efficiency of 9.1%, repetition rate of 1.1 MHz, and pulse width of 57 ns were achieved with 640 mW pumping. MHz-order repetition rate in Nd:YVO₄/Cr⁴⁺:YAG Q-switched laser with low pumping (<1 W) is the highest value to the best of our knowledge.     

Experimental development of a monolithic passively Q-switched diode-pumped Nd:YAG laser

The development of a passively Q-switched Nd:YAG laser is described in quite some experimental detail involving 3 pump diode arrays (70 W, 300 W, 600 W). Emphasis is set on the influence of pump beam profile and optimum fiber diameter on achievable pulse energies in the chosen case of fiber-coupling for the pump radiation (adjustable parameters: initial transmission, mirror reflectivity and resonator length; this work having been preceded by numerical simulations not covered in this paper). The coupling optics plays a major role on basis of variable fiber-lens distance and focal length in the formation of single or even multiple pulses. Finally, a monolithic demonstrator is presented which could be employed for applications like the induction of chemical reactions in general, i.e. ignition, for instance, in more detail. Stable ns-operation with emitted pulse energies up to 15 mJ could be achieved.     

Efficient diode-pumped passively Q-switched laser with Nd:YAG/Cr:YAG composite crystal

Diffusion bonded Nd:YAG/Cr:YAG composite laser crystal has been employed to perform a compact diode-pumped passively Q-switched laser. At the incident pump power of 3.3 W and pulse repetition rate of 16.3 kHz, the maximum average output of 592 mW has been obtained, corresponding to an optical-to-optical conversion efficiency of 18%. Stable passively Q-switched operation with peak power of 6.5 kW and pulse duration of 6 ns was also achieved. It has been experimentally revealed that Nd:host/Cr:YAG composite structure is a promising material for compact cost-effective Q-switched laser sources with high-peak power and short pulse duration. In addition, thermal lens effect (TLE) in the active medium and its impact on the Q-switched laser performance have been analyzed.     

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.     

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.