Laser sources for emission wavelengths > 1.4 µmThe risk to eyes from laser radiation with wavelengths greater than 1.4 µm is markedly lower since this radiation is not focused onto the retina. Applications such as LIDAR measurements for atmospheric research or standoff detection can be carried out at a reduced risk potential. This also results in lower requirements for screening scattered radiation for laser material processing. In addition, many procedures for frequency conversion in the mid infrared range require long wavelength pump lasers.
An example of a successful implementation of an efficient and scalable laser source with an emission wavelength of 2 µm is the Ho:YAG thin disk laser, which was developed at the Institute of Technical Physics. This laser also features the potential to generate high pulse energies.
Another category of laser materials being investigated is compound semi-conductors doped with transition metals, in particular Cr:ZnSe. This material offers a very broad amplification spectrum between 2 µm and 3 µm. It is thereby particularly suited for laser sources such as those required for remote detection applications which are based on the measurement of molecular rotational and vibrational transitions.