Da-Wun Chen

Diode-pumped 1-W continuous-wave Er:YAG 3-?m laser

We have demonstrated 1.15 W of Gaussianlike (M(2) = 2) cw output at 2.94 mum from a diode laser end-pumped monolithic laser crystal composed of Er-doped yttrium aluminum garnet (YAG) bonded to undoped YAG. The laser was pumped with two polarization-coupled 2.5-W flared laser diodes that provided a 45-mum pump waist with a low N.A. (<0.04) . Output at 2.94 mum was generated with a 34% slope efficiency and a greater-than-unity quantum efficiency.

Multiwatt continuous-wave and Q-switched Er:YAG lasers at 1645 nm: performance issues

The cw and Q-switched performance of Er:YAG lasers operating at 1645 nm were measured. Guided by previous work in the literature, we sought to improve efficiency at low pulse repetition frequencies by decreasing the doping level from 0.5 to 0.25 at.% to reduce upconversion losses. Only a small improvement was obtained with this first-time-tested lower-doped material. Measurements of the fluorescence due to upconversion directly indicated that loss due to this process could not account for the observed power loss at low pulse repetition frequencies. Enhanced green emission during Q-switched operation, resulting from two-photon absorption of 1645 nm intracavity laser light, is reported for what we believe to be the first time. Measurements indicated that the output loss from this process is negligible.

Narrowband Er:YAG nonplanar ring oscillator at 1645 nm

We report 1645 nm narrowband operation of a monolithic Er:YAG nonplanar ring oscillator resonantly pumped at 1532 nm. Unidirectional cw power up to 0.5 W was obtained with a measured linewidth of 21 kHz.

Continuous-Wave 4.3-mu Intracavity Difference Frequency Generation in an Optical Parametric Oscillator

We have achieved 150 mW of cw output at 4.3mum, using difference frequency mixing in a singly resonant optical parametric oscillator (OPO). We pumped the OPO cavity, which contains periodically poled LiNbO(3) (PPLN), with a 14-W 1.06-mum Nd:YAG laser to generate a signal at 1.7 mum and an idler at 2.8 mum. Mixing of the two waves at the same crystal temperature and grating spacing yielded emission in the mid IR. This technique avoids the mid-IR absorption-high-threshold problem, which has limited the cw performance of PPLN OPOs at wavelengths beyond 4 mum. Provided that tunability is not required, this method is a simple alternative to multiple-crystal configurations.

Low noise 10-W cw OPO generation near 3 /spl mu/m MgO doped PPLN

Over 10 W of near diffraction-limited output at 3-/spl mu/m was achieved from a singly resonant OPO pumped by a 50-W ytterbium fiber laser. Excellent frequency and power stabilities were observed using 5% MgO doped PPLN.

Semimonolithic Nd:YAG ring resonator for generating cw single-frequency output at 1.06 μm

We report 2.1 W of unidirectional single-frequency laser output from a novel Nd:YAG ring laser longitudinally pumped by a laser diode bar. The resonator requires only a single discrete optic and magnet, in addition to the laser medium, for stable multiwatt single-frequency operation. Undoped YAG is diffusion bonded to the Nd:YAG laser crystal at the pump face to eliminate residual spatial hole burning and improve thermal conductivity. This new laser design can be scaled to higher powers through more facile diode access and is useful for cw intracavity doubling.

Single-frequency low-threshold continuous-wave 3-μm periodically poled lithium niobate optical parametric oscillator

A low-threshold (350-mW) stable single-frequency continuous-wave optical parametric oscillator was demonstrated. Tunable idler output up to 450 mW was obtained near 3 μm by resonating both the signal wave and a single-frequency 1.06-μm Nd: YAG pump laser in a periodically poled lithium niobate optical-parametric-oscillator ring resonator. Tunable output wavelengths from 2.9 μm to 3.25 μm were also demonstrated. By inserting an etalon, we achieved an absolute midinfrared single-frequency stability of +/-0.01 nm.

High Performance 1645-nm Er:YAG Laser

The performance of the resonantly fiber-laser pumped Er:YAG lasers at 1645 nm using 0.25% and 0.5% doped crystals were compared in cw and Q-switched operation. Superior performance of the 0.25% crystals was observed.