Patrick A. Berry

Thermal effects in Cr/sup 2+/:ZnSe thin disk lasers

We report the modeling and experimental characterization of thermal lensing in Cr/sup 2+/:ZnSe face cooled laser disks using the phase shift interferometry technique. The thermal lens powers of the 1 mm and 0.5 mm thick disks were strong (23 and 7 diopters at 8 W pumping). The thermal lens power scaled with disk thickness and pump power, and temperatures were reached in the disks such that nonradiative relaxation was significant. Laser output greater than 4 W average power was achieved using face cooled thin disks of Cr/sup 2+/:ZnSe.

High-power, widely-tunable Cr 2+ :ZnSe master oscillator power amplifier systems

We demonstrate high-power Cr(2+):ZnSe master oscillator power amplifier (MOPA) pure continuous wave (CW) laser systems with output power of 14 W and amplifier gain greater than 2X. In addition, we develop a theoretical model for this type of amplification and show single-knob tunability at high powers over 400 nm.

Compact mid-infrared Cr:ZnSe channel waveguide laser

We demonstrate a mid-infrared channel waveguide laser in Cr:ZnSe operating at 2573 nm. The compact cavity has a total footprint of less than 3 cm2 and produces a maximum power output of 18.5 mW. The depressed index cladding structures guide across the entire emission band of Cr:ZnSe, from 1.9 μm to 3.4 μm, indicating the viability of the device for integrated and robust continuously tunable mid-infrared sources.

840 mW continuous-wave Fe:ZnSe laser operating at 4140 nm

We report the demonstration of high-power (840 mW) continuous-wave laser oscillation from Fe2+ ions in zinc selenide. The output spectrum of the Fe:ZnSe laser had a line-center near 4140 nm with a linewidth of 80 nm. The beam quality was measured to be M2≤1.2 with a maximum slope efficiency of 47%. Small shifts observed in output wavelength with increased output power were attributed to thermal effects. No thermal roll-off of slope efficiency was observed at the maximum of output power.

Fabrication and power scaling of a 1.7 W Cr:ZnSe waveguide laser

We report the fabrication and operation of a Cr:ZnSe buried channel waveguide laser operating at 2500 nm with a linewidth of 10 nm and a maximum power output of 1.7 W. Ultrafast laser inscription is used to fabricate the depressed cladding waveguide in a polycrystalline Cr:ZnSe sample. A thermal model is developed and predicts performance degradation at higher pump levels due to thermal quenching of the lifetime. This prediction is supported by the experimental results.

Compact Cr:ZnS channel waveguide laser operating at 2333 nm

A compact mid-infrared channel waveguide laser is demonstrated in Cr:ZnS with a view to power scaling chromium laser technology utilizing the thermo-mechanical advantages of Cr:ZnS over alternative transition metal doped II-VI semiconductor laser materials. The laser provided a maximum power of 101 mW of CW output at 2333 nm limited only by the available pump power. A maximum slope efficiency of 20% was demonstrated.

Mid-infrared laser emission from Fe:ZnSe cladding waveguides

The authors present a mid-IR depressed cladding waveguide laser in Fe:ZnSe. The laser produced a maximum output power of 76 mW at 4122 nm and laser thresholds as low as 154 mW were demonstrated. This represents a 44% reduction in threshold power compared with the bulk laser system demonstrated in this paper. The waveguide laser was found to have a narrow spectral linewidth of 6 nm FHWM compared to the 50 nm typical of bulk Fe:ZnSe lasers.

A Passively

We report the demonstration of high-average-power passively Q-switched laser oscillation from Fe2+ ions in zinc selenide. A semiconductor saturable absorber mirror was used as a passive Q-switch element. Using a 60% R outcoupler, the pump-limited output power was 515 mW. The spectral center of the laser was 4045 nm. The pulse repetition frequency (PRF) at maximum power was ~ 850 kHz with a corresponding minimum pulsewidth of 64 ns Full-Width Half-Maximum. The pulse energy and peak power were and 8.3 W, respectively. The average output power was limited only by available pump power and increased with a slope efficiency of 22%. No thermal rolloff of slope-efficiency was observed. The beam quality was measured to be M2 ≤ 2.6. The temporal stability of the pulsed output was characterized. Thermal effects were shown to play a significant role in determining the PRF of the output.

Q

We report demonstration of efficient continuous-wave lasing from chromium-doped zinc selenide using anti-reflection microstructures (ARMs) in place of thin-film AR coatings or Brewster angle cavity geometries. ARM textures are more resistant to laser-induced damage than coatings, exhibit low-loss, wide angular acceptance, broad wavelength effectiveness, and are not susceptible to water absorption. Slope-efficiencies of 68% were achieved, which compares favorably to the thin-film control samples at 58% for the same cavity. ARMs hold promise for near-term power scaling and wavelength agility of transition-metal-ion doped II-VI lasers.

-Switched, CW-Pumped Fe:ZnSe Laser

Mid-infrared waveguides were fabricated in ZnSe using ultrafast laser inscription to directly write a cladding region in the material. Single-mode guiding at 3.39 µm was achieved with propagation losses of 1.9 dB·cm−1.