Sean A. McDaniel

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.

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.

Cr:ZnSe laser incorporating anti-reflection microstructures exhibiting low-loss, damage-resistant lasing at near quantum limit efficiency

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.

Power scaling of ultrafast laser inscribed waveguide lasers in chromium and iron doped zinc selenide

We report demonstration of Watt level waveguide lasers fabricated using Ultrafast Laser Inscription (ULI). The waveguides were fabricated in bulk chromium and iron doped zinc selenide crystals with a chirped pulse Yb fiber laser. The depressed cladding structure in Fe:ZnSe produced output powers of 1 W with a threshold of 50 mW and a slope efficiency of 58%, while a similar structure produced 5.1 W of output in Cr:ZnSe with a laser threshold of 350 mW and a slope efficiency of 41%. These results represent the current state-of-the-art for ULI waveguides in zinc based chalcogenides.

Operation of Ho: YAG ultrafast laser inscribed waveguide lasers

We report fabrication and operation of multi-watt level waveguide lasers utilizing holmium-doped yttrium aluminum garnet (Ho:YAG). The waveguides were fabricated using ultrafast laser inscription, which relies on a chirped pulse ytterbium fiber laser to create depressed cladding structures inside the material. A variety of waveguides were created inside the Ho:YAG samples. We demonstrate output powers of ∼2  W from both a single-mode 50 μm waveguide laser and a multimode 80 μm waveguide laser. In addition, laser action from a co-doped Yb:Ho:YAG sample under in-band pumping conditions was demonstrated.

Hot isostatic pressing of transition metal ions into chalcogenide laser host crystals

This paper describes a technique using a hot isostatic pressing (HIP) for the diffusion of transition metal ions into chalcogenide laser host crystals. Thin layers of chromium metal are sputtered onto the surface of zinc selenide and zinc sulfide crystals before treatment in a HIP chamber. The transmissivities, excited state lifetimes, and diffusion rates are measured for various dopant concentrations. Efficiency, spectral output, and tuning data are also measured for a Cr:ZnSe laser. The diffusion rate of 5.48 × 10−8 cm2/s is two orders of magnitude faster than other techniques reported in the literature, and the sub 140 pm measured linewidth is more than 350 times smaller than what is typical of commercially available crystals. Preliminary results for Fe:ZnSe, Co:ZnSe, and Ni:ZnSe are presented as well.

Fe:ZnSe channel waveguide laser operating at 4122 nm

The first demonstration of a waveguide laser in Fe:ZnSe is presented. The waveguide laser produces 49 mW of output power at 4122 nm with a spectral bandwidth of 6 nm FWHM.

Gain-switched operation of ultrafast laser inscribed waveguides in Cr:ZnSe

We report the first demonstration of a gain-switched chromium-doped zinc selenide channel waveguide laser. The guided-wave structure was produced by ultrafast laser inscription and exhibited output pulse energies up to 12 μJ . The laser exhibited narrow spectral output with a linewidth less than 1 nm. The beam quality was measured to be M2 ≤ 7 with a highly multimode output profile. The laser had a maximum slope efficiency of 9.8% and no deleterious thermal effects were observed up to an average pump power of 3.3 W .

Path to doubling the efficiency of mid-IR erbium lasers

It has been experimentally shown that a Cr:ZnSe optical amplifier can be successfully used for self-amplification of the cascade Er:Y2O3 laser. This is to our best knowledge the first demonstration of an optical amplifier where both signal and pump are delivered from a single laser source. Absorption and emission spectra of the Cr:ZnSe are perfectly positioned to amplify the output of the cascade Er:Y2O3 laser, when the 1.6 μm emission of the cascade laser serves as a pump, while 2.7 μm as a signal. We have also shown that this concept is valid for any bulk or fiber cascade erbium laser.

5.9 GHz graphene based q-switched modelocked mid-infrared monolithic waveguide laser

A high repetition rate Q-switched modelocked ~2.1 µm monolithic waveguide laser is reported. Ultrafast laser inscription is used to fabricate 3D depressed cladding channel waveguides in holmium doped yttrium aluminium garnet. This results in a transversely single mode waveguide laser. With the use of a graphene based saturable output coupler, Q-switched modelocking was achieved with a pulse repetition frequency of 5.9 GHz and up to 170 mW of average output power. This first demonstration of multi-GHz repetition rate operation from a Ho3+:YAG laser provides a compact and convenient source for a number of applications.