Self-stabilized single-longitudinal-mode operation in a self-Q-switched Cr,Nd:YAG laser

Elimination of spatial hole burning in solid-state lasers using nanostructured thin films

Multimode laser emission generally takes place in homogeneously broadened gain media placed inside a standing-wave resonator due to spatial hole burning. Solutions proposed to eliminate this phenomenon have so far involved the use of intracavity elements, such as an etalon, wave plates or saturable absorbers. We propose a monolithic solution, wherein birefringent layers of TiO₂ are deposited on both laser mirrors. This solution enables one to control the contrast of the interference pattern of the standing wave inside the resonator, and thus the strength of the spatial hole burning, by rotating one mirror around the optical axis. A monochromatic laser emission is demonstrated in a quasi-continuous-wave laser-diode-pumped Yb³⁺:YAG laser experiment.

Sub-nanosecond stimulated Brillouin scattering pulse compression using HT270 for kHz repetition rate operation

With mitigation of thermal effects in a generator cell based on a rotating off-centered lens, the effects of thermal blooming, self-defocusing, and thermal convection in the amplifier cell have experimentally proven to be the main factors limiting high-repetition-rate stimulated Brillouin scattering (SBS) pulse compression. To alleviate these effects, Galden HT270, which has a large viscosity coefficient, is used and compared experimentally. The operating repetition rate using HT270 was improved from 200 Hz to 1,000 Hz, comparable to the values in the literature. With a pump energy of 50 mJ at 1,000 Hz, the pump pulse was compressed down to 820 ps using HT270 with an energy efficiency of 52.2%. If the injection energy is further increased, the SBS energy efficiency can be increased beyond this value.

Exploring transverse pattern formation in a dual-polarization self-mode-locked monolithic Yb: KGW laser and generating a 25-GHz sub-picosecond vortex beam via gain competition

Formation of transverse modes in a dual-polarization self-mode-locked monolithic Yb: KGW laser under high-power pumping is thoroughly explored. It is experimentally observed that the polarization-resolved transverse patterns are considerably affected by the pump location in the transverse plane of the gain medium. In contrast, the longitudinal self-mode-locking is nearly undisturbed by the pump position, even under the high-power pumping. Under central pumping, a vortex beam of the Laguerre-Gaussian LGp,l mode with p = 1 and l = 1 can be efficiently generated through the process of the gain competition with a sub-picosecond pulse train at 25.3 GHz and the output power can be up to 1.45 W at a pump power of 10.0 W. Under off-center pumping, the symmetry breaking causes the transverse patterns to be dominated by the high-order Hermite-Gaussian modes. Numerical analyses are further performed to manifest the symmetry breaking induced by the off-center pumping.

Passive frequency stabilization in Nd:YAG pulse laser using reflective volume Bragg grating

We demonstrate a stable Q-switched single-longitudinal-mode (SLM) Nd:YAG laser using a volume Bragg grating as the output coupler. The reflective volume Bragg grating, serving as a longitudinal selector and passive frequency stabilizer, effectively eliminates the mode hopping effect of the laser. The maximum output energy of the SLM obtained from the current experimental setup is 18.5 mJ. The maximum separation of frequencies is significantly less than the longitudinal mode separation, indicating that a stable SLM laser is achieved.

Timing jitter reduction and single-frequency operation in an acousto-optic Q-switched Cr,Nd:YAG laser

A laser-diode-pumped watt-level single-frequency combined actively and passively Q-switched (CAPQ) laser with a wavelength of 1064 nm that simultaneously uses a codoped Cr(4+),Nd(3+):YAG crystal as the gain medium and mode selector is presented. The optimum repetition period of the CAPQ laser is approximately 1.5 times the natural repetition period of the passively Q-switched laser. The averaged timing jitter is approximately 400 ns in the CAPQ laser and the repetition rate of the CAPQ laser is experimentally shown to reach a time instability of 0.2% over 10(6) pulses. The output is a stable single frequency with a linewidth of 400 MHz at 20 W pump power.

High-power monolithic unstable-resonator solid-state laser

We report the operation of a diode-pumped monolithic Q-switched unstable-resonator solid-state laser that generates 2.15-mJ, 2-ns pulses in a single transverse mode and a single longitudinal mode. We show that the unstable resonator is effective in suppressing the spatial and the temporal instability of the laser beam in a disk-shaped laser whose transverse dimension is comparable with or larger than its longitudinal dimension.

Passively Q-switched Nd:YAG ring lasers with high average output power in single-frequency operation

Applying Cr(4+):YAG saturable absorbers, we demonstrate efficient passively Q -switched operation of diode-pumped Nd:YAG lasers with a maximum average output power of more than 800 mW. Pulse durations below 3 ns, energies of 70 microJ, and peak powers of 30 kW are observed with kilohertz repetition rates. Single-frequency operation is accomplished for all output powers by a nonplanar ring geometry.

Integrated electro-optic Q switching in a domain-inverted Nd:LiTaO(3) laser

We report a novel integrated Q-switched laser constructed from a bulk domain-inverted single Nd:LiTaO(3) crystal that combines the laser gain and the electro-optic effect. The Q of the cavity is controlled electro-optically by exploitation of the deflection that occurs at the boundary of two oppositely directed domains under the application of an electric field. The integrated Q-switching element, with dimensions of 4.1 mm x 4.6 mm x 1 mm, generates 22-ns pulses at 1.08 microm with a peak power of 64 W and an operating voltage of ~600 V. The output is seen to be completely free from prelasing or afterpulsing.