Transition-metal-doped chalcogenide lasers

Abstract

INTRODUCTIONBroadly tunable near-and mid-infrared lasers are of interest for a variety of scientific, remote-sensing, and military applications. Uses include high-resolution optical spectroscopy; metrology; pumping of nonlinear optical-frequency converters, such as optical parametric oscillators (OPOs); standoff chemical sensing; optical communications through poor visibility conditions; multispectral detection and imaging; and infrared countermeasures. Tunable laser sources in the 2-3-m region include Cr 2ϩ -doped chalcogenide lasers; cryogenic materials, such as color-center lasers; limited tunability systems, such as Tm lasers, gas or chemical lasers, and semiconductor lasers; and nonlinear optical devices, such as OPOs. 1 Coherent radiation sources in the 3-4-m band include the previously named sources, leadsalt diode lasers, and nonlinear frequency mixers.Transition-metal-doped chalcogenide lasers are of high interest because of their versatility, broad room-temperature wavelength tunability, demonstrated high optical efficiencies, potential to be scaled to high powers via direct-diode pumping, and relative novelty. To date, continuous-wave (CW), gain-switched, and mode-locked laser operation has been demonstrated. Material advantages can include broad absorption and emission bands, highfluorescence quantum efficiencies at room temperature, moderate-gain cross sections, and minimal susceptibility to loss mechanisms, such as excitedstate absorption or up conversion. Additionally, the materials can be produced by a variety of methods, including several direct-growth techniques and diffusion doping. The principal material disadvantages include a high dn/dT (the change in refractive index with temperature) and, for some applications, a short energy-storage time. The high dn/dT is an issue because it can lead to strong thermal lensing, which complicates high-power laser designs.In this paper, I briefly review fundamental chalcogenide-laser material properties, the current state-of-the-art of CW and pulsed Cr 2ϩ -and Fe 2ϩ -doped chalcogenide lasers, and selected recent research results. A short discussion is also provided for laser-active Cr 2ϩ -doped ternary-compound II-VI semiconductors. Because many subject areas are only briefly summarized, I have attempted to provide liberal references for the interested reader. MATERIAL PROPERTIESThe seminal work in this field is the paper by DeLoach and colleagues at Lawrence Livermore National Laboratory (Livermore, CA), 2 which provides a thorough discussion of the spectroscopic features of Cr 2ϩ , Fe 2ϩ , Co 2ϩ , and Ni 2ϩ ions in several zinc-chalcogenide hosts. It is worth noting that the luminescent properties of transition-metal-doped chalcogenides had been described several decades earlier by a number of researchers; 3-7 however, the Livermore work was pivotal because it focused on the laser critical features of these materials and described the first reported laser action from this class of materials.Broadly tunable mid-infrared lasers are desirable for a number o...

Comparison of the optical properties of diffusion-doped polycrystalline Cr:ZnSe and Cr:CdTe windows

“…Room-temperature lasing in the 2-3 mm range has been reported from several Cr 2+ -doped II-VI's including Cr:ZnS [1,2], Cr:ZnSe [1][2][3], Cr:Cd 0.85 Mn 0.15 Te [4], Cr:Cd 0.55 Mn 0.45 Te [5], Cr:CdTe [6], and Cr:CdSe [7]. The lasing center in these materials has been assigned to Cr 2+ ions occupying tetrahedral cation (Zn, Cd) lattice sites.…”

“…The optical properties of transition-metal-doped chalcogenide semiconductors have attracted significant attention for applications in tunable mid-infrared (MIR) lasers [1][2][3][4][5][6][7][8][9][10]. Room-temperature lasing in the 2-3 mm range has been reported from several Cr 2+ -doped II-VI's including Cr:ZnS [1,2], Cr:ZnSe [1][2][3], Cr:Cd 0.85 Mn 0.15 Te [4], Cr:Cd 0.55 Mn 0.45 Te [5], Cr:CdTe [6], and Cr:CdSe [7].…”

Optical absorption and reflectivity spectra of highly chromium doped CdTe alloy and layer

“…Chromium doped II-VI semiconductors are currently of great interest as mid-infrared solid-state laser materials and as saturable absorbers for passive Q-switching [1][2][3][4][5]. A tunable laser operation of chromium ions in the region 2 -3 µm (e.g., ZnSe:Cr, CdSe:Cr, and CdMnTe:Cr) has been reported [5].…”

“…New Cr doped laser host materials are being sought for extending the current laser wavelength coverage as well as for improving laser efficiency. The optical centers in these materials have been assigned to the Cr 2+ ions occupying tetrahedral lattice sites [1][2][3][4][5].…”

Structure characterization of MBE-grown (Zn,Cr)Se layers

“…The chromium as a dopant has also attracted a lot of attention because of an effective Cr 2+ photoluminescence at wavelengths near 2.4 m. It is one of the reasons why the wide-gap, Cr-doped II-VI semiconducting compounds like ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, Cd 1−x Zn x Te, Cd 1−x Mg x Te or Cd 1−x Mn x Te have been an object of intensive studies during the last decade (for detail see e.g., Refs. [21][22][23]). Cr-doped ZnSe is a particularly interesting material because of a small lattice mismatch between ZnSe and GaAs, which could be very useful for several optoelectronic devices.…”