Fe:ZnSe and other transition metals have broad upper and lower energy manifolds which give rise to broad absorption and fluorescence bands in the mid-IR spectral region. Energy transfer between Fe<sup>2+</sup> ions via re-absorption of fluorescence (due to the spectral overlap of these bands) and phonon-assisted energy transfer (due to the lattice dynamics of ZnSe) becomes more probable with increasing Fe<sup>2+</sup> concentration. Here we treat these processes as additional terms in the rate equations which govern the spontaneous decay of the Fe<sup>2+</sup> ion. This treatment gives insight into anomalous behavior seen in the thermal lifetime of the Fe:ZnSe system. We also apply the model to other transition metal doped II-VI materials.
This paper describes using a hot isostatic pressing (HIP) to improve II-VI crystal characteristics and diffuse metal ions into laser host crystals. Thin layers of metal are sputtered onto the surface of zinc selenide and zinc sulfide crystals prior to being HIP treated. The pre and post treatment optical properties for these materials are measured using various methods and at a variety of dopant concentrations.
We describe a variety of technological advances in the development of efficient, powerful, and continuously tunable Cr:ZnSe lasers operating in the 2.3-2.7 μm spectral region. This includes the development of compact "single chip" waveguide Cr:ZnSe lasers, waveguide mode-locked Cr:ZnSe lasers, and the creation of homogeneously broadened laser material.
In addition to the well-established <sup>5</sup>I<sub>7</sub> to <sup>5</sup>I<sub>8</sub> transition at 2.09 μm in holmium doped laser materials, there also exists a less energetic transition from the <sup>5</sup>I<sub>6</sub> level to <sup>5</sup>I<sub>7</sub> at 2.95 μm. As there has been a recent increase in interest and applications for 3.0 μm light, this material stands to be a viable alternative to other rare earth doped laser systems. Unfortunately, the wavelength required to directly pump the <sup>5</sup>I<sub>6</sub> level at 1.13 μm is not convenient for commercial laser diodes. Furthermore, the emission lifetime of the <sup>5</sup>I<sub>7</sub> state is longer than the <sup>5</sup>I<sub>6</sub> level, leading to a suppression of lasing due to “bottlenecking” in the material. To overcome these effects, we investigated the activation and deactivation of holmium doped yttrium aluminum garnet (YAG) using ytterbium and praseodymium respectively. By including ytterbium ions in the host material, readily available 914 nm diode light can be used to resonantly excite the <sup>5</sup>I<sub>6</sub> level in holmium. Similarly, the presence of praseodymium resonantly de-excites the <sup>5</sup>I<sub>7</sub> state, reducing its lifetime, and making the material more suitable for lasing. Here, we report the absorption and photoluminescence spectra of this triply doped Yb,Ho,Pr:YAG crystal. In addition, the emission lifetime for both the 2.09 μm and 2.95 μm transitions are reported and compared to a Yb,Ho:YAG control sample.