Color Center Lasers: State of the Art and Recent Developments

Abstract

Tunable lasers using color centers in alkali halide crystals are well established laser systems in the near infrared spectral region (see e.g. [1] – [6]. The wavelength range from 0,8 µm up to almost 4 µm can, in principle, be covered using different types of color centers in various alkali halides. This is shown in Fig. 1 where the emission bands are displayed. Unfortunately, the performance of some of the laser systems (e.g. F₂ ⁺, (F₂ ⁺)*) is not always ideal with respect to the generation of the desired centers, their stability during laser operation and the shelf lifetime of the crystals. In particular, the wavelength range below 2.2 µm was difficult to be covered with stable and reliable color center crystals.