G.J. Friel

Guiding effects in Nd:YVO/sub 4/ microchip lasers operating well above threshold

Guiding of the transverse mode in Nd:YVO/sub 4/ microchip lasers is examined both experimentally and theoretically at pump powers well above threshold. It is found that thermal changes in the cavity geometry induced by intense diode pumping can be well understood using a simple model. However, an understanding of these effects is not sufficient to explain the nature of the transverse mode. Gain-related guiding effects are found to play an important role even at pump powers well above threshold. For a 0.5-mm-thick microchip laser, a difference of around 30% is observed between the minimum beam waist expected due to thermal guiding and the measured beam waist. The gain-related effects are described theoretically and their importance is demonstrated experimentally.

Microchip Nd:vanadate lasers at 1342 and 671 nm

As much as 105 mW of single-frequency output at 1342 nm was obtained from a diode-laser-pumped Nd:YVO(4) microchip laser. An intracavity frequency-doubled device generated 10 mW of single-frequency red radiation.

Polarization effects, birefringent filtering, and single-frequency operation in lasers containing a birefringent gain crystal

The effect of having a birefringent gain crystal is studied in the context of two laser systems: an intracavity frequency-doubled microchip laser and a compact single-frequency laser utilizing a birefringent filter. A model based on Jones calculus is proposed to predict the polarization and wavelength structure of the longitudinal modes and is found to be consistent with experimental measurements. The optimization of these systems is discussed, and the importance of the birefringences in the cavity and cavity length is indicated.

Self-Q-switched Nd:YVO4 microchip lasers.

We have observed giant pulses from cw pumped, monolithic Nd:YVO(4) microchip lasers, several hundred times the cw level, with pulse lengths less than 2 ns, which cannot be accounted for by conventional gain switching. These pulses occur as the second longitudinal mode starts to oscillate and can be described by the inclusion of gain-related effects in the formation of a stable cavity.

Compact low-threshold Q-switched intracavity optical parametric oscillator

We report a singly resonant pulsed intracavity KTiOPO>(4) optical parametric oscillator that uses a semi-monolithic microchip laser design. The compact (50-mm-long), low-threshold (1.3-W) cavity uses a novel quadrupole deflector Q switch to give 4-microJ pulses at 1.064 microm and 0.4-microJ signal pulses of 5.6-ns duration at 1.53 microm with a repetition frequency of 5 kHz when it is pumped with a 2-W laser diode. The signal pulses are diffraction limited and single frequency.

Compact and efficient single-frequency Nd : YVO/sub 4/ laser with variable longitudinal-mode discrimination

We show for the first time that the longitudinal-mode discrimination in a birefringently filtered laser can be tuned through the variation of the waveplating action of the gain crystal. In this way, the laser can be optimized for either high intermodal discrimination or for frequency tuning with reduced output power rolloff. Up to 760 mW of single-frequency 1064-nm output is obtained from a compact diode-pumped source that can be frequency chirped over 6.5 GHz.

Comparison between Nd:YAG and Nd:YVO/sub 4/ as gain media for a single-frequency micro-laser

Summary form only given. Microchip lasers are highly efficient and easily mass produced sources of laser radiation. Single-frequency operation, however, is difficult at output powers about 150 mW. Thus, there is great interest in developing single-frequency sources that keep the simplicity of microchip lasers yet which can be operated on a single mode at higher output powers. We have demonstrated 760 mW single frequency at 1064 nm under pumping from a 2 W diode laser. This laser employed Nd:YVO/sub 4/, as a gain medium as opposed to Nd:YAG, which has often been used in such lasers in the past. It utilized a birefringent filter consisting of a Brewster plate and a YVO/sub 4/ birefringent crystal.

Guiding effects in microchip lasers at pump powers well above threshold

Summary form only given. Microchip lasers are monolithic devices, typically consisting of a sub-millimetre thick slice of solid state gain material, which is polished to give plane parallel surfaces on to which dielectric mirrors are coated. These lasers are longitudinally pumped by a laser diode. Devices such as Nd:YVO/sub 4/ microchip lasers are highly-efficient and compact lasers which produce beams of high spatial and spectral quality.

V:YAG as passive Q-switch at 1342 nm and 1064 nm

We report the first use of V:YAG as a passive Q-switch for a diode pumped Nd/sup 3+/ laser at 1 /spl mu/m and 1.3 /spl mu/m. Previous investigations of the dynamics of the excited states and saturation of V:YAG showed that this crystal can be successfully used as a saturable absorber for pulsed lasers operating in the red and infrared spectral regions.

Self-Q-switched Nd:YVO/sub 4/ microchip lasers

Microchip lasers are typically formed by applying dielectric mirrors directly to two near-parallel surfaces of a thin slice of laser gain material. Nd:YVO/sub 4/ is a commonly used gain material because of its short absorption depth and high stimulated emission cross section. While working on gain-switched Nd:YVO/sub 4/ microchip lasers, we observed in these monolithic devices large spiking behavior, which could not be accounted for by normal gain-switching theory. Gain switching can produce peak powers in excess of a watt, several times the cw level, with pulses as short as 5 ns. However, the large spikes we observed were several hundred times the cw level with peak powers >25 W and pulses as short as 1.85 ns, more similar in nature to Q-switched pulses. We have constructed a simple model to include this effect in determining the stability of a microchip laser. The results of this model are presented in comparison to the observed experimental work, to show how the effects of gain-related cavity stability can cause self-Q-switching in a Nd:YVO/sub 4/ microchip laser.