II-VI Lasers Research Articles

2 mJ room temperature Fe:CdTe laser tunable from 5.1 to 6.3 μm.

We report a room temperature (RT) operation of a Fe:CdTe laser pumped by a Q-switched 2.94μm Er:Y3Al2(AlO4)3 laser. The Fe:CdTe laser produced 2mJ of output energy at λ=5.55 μm with slope efficiency of 16% with respect to absorbed pump energy. With the use of an intracavity prism, the spectral tuning was demonstrated in the 5.1-6.3μm range, being the longest wavelength tuning achieved for Fe2+:II-VI lasers. The lifetime of the upper laser level was measured to be 530ns at RT.

Frontiers of Mid-IR Lasers Based on Transition Metal Doped Chalcogenides

Enabling broad tunability, high peak and average power, ultrashort pulse duration, and all known modes of laser operation—transition-metal (TM)-doped II–VI chalcogenides are the materials of choice for direct lasing in the mid-IR. The host materials feature broad infrared transparency, high thermal conductivity, low phonon cutoff, low optical losses, and are available as either single crystals or polycrystalline ceramics. Doped with TM ions, these media exhibit a four-level energy structure, the absence of excited state absorption, as well as broad absorption and emission bands. Doped single-crystals of high optical quality are difficult to grow; however, the advent of postgrowth diffusion doped ceramics has resulted in significant progress in laser development. Here, we summarize recent experimental laser results on Cr and Fe doped II–VI chalcogenides providing access to the 1.8–6 μm spectral range with a high (>60%) efficiency, multi-Watt-level [140 W in continuous wave (CW)] output powers, tunability of >1000 nm, short-pulse (<16 fs) multi-Watt oscillation, and multi-Joule output energies in free running and gain-switched regimes. We also review recent results on hybrid fiber-bulk (Er-fiber/Er:YAG, Tm-fiber: Ho:YAG/YLF) systems combining high efficiency of CW fiber lasers with high pulse energies of bulk materials and serving as pump sources of gain-switched Cr:II-VI 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.

Efficient mid-infrared Cr:ZnSe channel waveguide laser operating at 2486 nm

We report a Cr:ZnSe channel waveguide laser operating at 2486nm. A maximum power output of 285mW is achieved and slope efficiencies as high as 45% are demonstrated. Ultrafast laser inscription is used to fabricate the depressed cladding waveguide in a polycrystalline Cr:ZnSe sample. Waveguide structures are proposed as a compact and robust solution to the thermal lensing problem that has so far limited power scaling of transition metal doped II-VI lasers.

Progress in mid-IR Cr^2+ and Fe^2+ doped II-VI materials and lasers [Invited

Recent progress in fabrication and mid-IR lasing of transition metal doped II-VI single crystal and thermo-diffusion doped polycrystalline and hot-pressed ceramic gain media as well as nano and micro-crystalline laser active powders, powders in the liquid suspension, polymer-film, thin film waveguides and chalcogenides glass composites is reported.

A novel approach for improved green-emitting II-VI lasers

New concepts to improve the performance of green-emitting laser diodes, based on the ZnSe system, are presented. The benefits of implantation-induced disordering (IID) and a novel alleged contact structure are discussed. Using IID, index-guided lasers with low thresholds are fabricated. The introduction of Li/sub 3/N-containing contacts leads to an acceptor indiffusion resulting in an increased p-type doping level and thereby extremely reduced turn-on voltages, threshold current densities, increased wall-plug efficiencies, and extended continuous-wave lifetimes.

BeCdSe/(Be,Zn)Se Quantum Well as a New Active Region for Blue-Green II-VI Lasers and Light-Emitting Diodes

BeCdSe/(Be,Zn)Se Quantum Well as a New Active Region for Blue-Green II-VI Lasers and Light-Emitting Diodes

Room-temperature CW operation of II-VI lasers grown on ZnSe substrates cleaned with hydrogen plasma

Room-temperature CW operation of II-VI lasers grown on ZnSe substrates cleaned with hydrogen plasma

Microgun-pumped semiconductor laser

We demonstrate the feasibility of a novel microgun-pumped semiconductor laser. This is the most compact (a few cm3) and the lowest threshold electron-beam-pumped semiconductor laser ever reported. The electron source is provided by a 104–105/mm2 array of field emissive microtip cathodes each of 1.5 μm diam. The laser operates below 10 kV and below 1 A/cm2. Laser action in a quasi-cw mode with 5 μs pulses at 2 kHz has been obtained between 90 and 300 K with CdTe-CdMnTe graded index separate confinement quantum-well heterostructures, as well as with GaAs-GaAlAs structures. Since neither doping nor ohmic contacts are needed, the microgun laser can use all direct gap semiconductors. It appears as a viable solution for making compact II-VI lasers in the visible domain.

Lead salt quantum effect structures

Lead salt (IV-VI) compounds have been grown epitaxially by a variety of growth techniques, such as molecular-beam epitaxy and hot-wall epitaxy. Recently, compositional superlattices and quantum-well heterostructures have been grown that exhibit strong quantum optical effects. These structures have been used to fabricate midinfrared diode lasers with greatly improved operating temperatures. Thus, it appears that these devices will continue to maintain a significant advantage over II-VI and III-V compound diode lasers. Doping superlattices have been made which possess enhanced minority carrier properties. Ferromagnetic ordering in PbSnTe-MnTe alloys suggests potential areas for future work in magnetic field sensitivity devices. Lead salt quantum-effect structures are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Threshold in electron-beam end-pumped II-VI lasers

Electron-beam end-pumped lasers from different bulk grown II-VI compounds have been experimentally studied and compared under similar preparation and excitation conditions. The reasons for the lasing threshold variations are discussed. The first results on e-beam pumped CdMnTe lasers and end-pumped CdTe lasers are reported. The order of lowest to highest threshold is found to be from CdSe, ZnCdSe, CdS, CdTe, CdMnTe, and ZnSe. The comparisons between lasing conditions are used to evaluate the contribution of the intrinsic semiconductor parameters to lasing threshold. Experiments with a large number of samples indicate that the influence of intrinsic and extrinsic parameters on lasing threshold are in most cases comparable. Therefore, for most bulk II-VI lasers, the average threshold pump power density reductions with the elimination of extrinsic factors are expected to be less than several times. These findings are further supported by our threshold and relative slope efficiency measurements on lasers with different output mirror couplings.

Characteristics of Optically Pumped Platelet Lasers of ZnO, CdS, CdSe, and CdS0.6Se0.4 Between 300° and 80°K

The behavior of platelet lasers of ZnO, CdS, CdSe, and CdSe0.4S0.6 pumped by a pulsed Xenon laser at 3646 Å is described. Single-mode operation of CdSe and ZnO over the full temperature range 80° to 300°K is observed. Absolute threshold-temperature curves and absolute input-output efficiency curves are presented and found to differ significantly from results of electron-beam pumped platelets. These results are predicted by an analysis of the cavity configuration including the effects of spatial inhomogeneity of the gain. The importance of this inhomogeneity for interpretation of experimental gain-loss mechanism in II-VI lasers is emphasized, and the implications of the spectral and threshold data for current theoreies of the gain process are discussed. Neither the exciton-LO phonon nor the non-LO phonon theories, in their present form, appear able to explain all the data.

Optically Pumped Thin-Platelet Semiconductor Lasers

Thin vapor-grown platelets of Cd(SeS) and thin platelets of GaAs and Ga(AsP) prepared from bulk wafers have been pumped as lasers with Ga(AsP) diode lasers used as the optical excitation sources. Continuous laser emission at 77°K in the visible spectrum has been obtained from thin Cd(SeS) platelets pumped with a cw He–Ne laser. Thin platelets of Cd(SeS) have been found to be essentially transparent to their own laser emission, and a mechanism responsible for laser action is discussed to account for this behavior. The mode and oscillator behavior of thin platelet II-VI and III-V lasers is discussed. Experimental effects due to many-body interactions of charge carriers in a III-V semiconductor platelet laser have been obtained; these are manifest in the shift of laser emission to longer wavelengths with increasing excitation under conditions of negligible crystal heating