Mid-IR waveguide lasers in transition metal doped II-VI semiconductors

• Main Author: Lancaster, Adam
• Other Authors: Kar, Ajoy K.
• Published: Heriot-Watt University 2017
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.754491

This thesis focuses on the development of compact Mid-IR waveguide laser systems in transition metal doped II-VI semiconductors. These waveguide lasers have been developed to produce high brightness and compact sources in the Mid-IR. The wavelength tuneable operation of Cr:ZnSe waveguides was investigated. The waveguides were fabricated using ultrafast laser inscription. The waveguide laser demonstrated a tuning range of 2080 - 2883 nm, with more than 15 mW of output power across the full range. This resulted in a tuneable bandwidth of 39 THz, which is the widest range demonstrated by a Mid-IR waveguide laser. Modelocking of a Cr:ZnSe waveguide laser was investigated using a SESAM. This resulted in the demonstration of a CW modelocked laser with a PRF of 308 MHz, pulse energy of 0.3 nJ and a pulse width of 638 fs. In addition, a CW modelocked laser was demonstrated with a PRF of 1.03 GHz, this is the fastest PRF of any Cr:ZnSe laser demonstrated. Other transition metal doped II-VI semiconductors were investigated. Waveguides were developed in Cr:ZnS because of its improved thermal properties compared with Cr:ZnSe for future power scaling applications. The Cr:ZnS waveguide laser emitted 97 mW at a central wavelength of 2333 nm. Waveguide laser operation was investigated in Fe:ZnSe for laser operation in the 3.7 to 5 μm spectral band. Firstly, low-loss laser waveguide parameters were investigated in Fe:ZnSe. The passive characterisation found the waveguide propagation losses to be as low as 0.4 dB/cm, which is much lower than those demonstrated in other ULI cladding waveguides in Cr:ZnSe and Cr:ZnS. The low-loss waveguides were inserted inside a cryostat for CW laser operation. A free running CW laser operation with an Fe:ZnSe waveguide laser was demonstrated. An output power of 76 mW was produced at 4122 nm with a pump power of 908 mW. This work highlights the operational wavelength versatility of ULI fabricated depressed cladding waveguides.