Focused laser radiation over shorter distances is an established tool for many applications such as laser materials processing and medicine. Using high power and high beam quality laser sources, it is also possible to transfer and focus energy over large distances. The alignment of the laser beam can thereby be easily and very rapidly controlled by tilting and tuning a reflector. For this reason such long range laser effectors are particularly suited for hitting fast moving objects with laser radiation.
These properties open up a variety of applications. One example is power transmission using laser radiation for energy delivery – for instance for solar-powered unmanned aerial vehicles (UAVs) to make them usable at night. Even satellites could be supplied with energy in this way to compensate for the deterioration of solar cells, significantly increasing the mission duration.
Important safety applications for long range laser effectors include the protection of infrastructure against attack by mortar shells and missiles, and also the protection of aircrafts during take off or landing against surface-to-air missiles.
The beam shaping and guidance is a significant component of such a system. It must guarantee both optimum focusing of the beam onto the target and tracking of the beam on the target – even if the propagation through the atmosphere leads to marked disturbances in the beam position and beam profile.
For this purpose, methods are being developed at the Institute of Technical Physics for target tracking and the compensation of atmospheric disturbances. These methods are tested on a laser test range.
Specific requirements arise for the laser source for long range laser effectors: • The emission wavelength must lie outside of atmospheric absorptions.• The beam quality must be extremely high for optimum focusability.• The effector system should be compact and efficient.
Based on currently available technology, diode pumped solid state lasers – in particular slab lasers, fibre lasers and disc lasers – are regarded as the best suited beam sources for this purpose. At present fibre lasers offer the highest output power with excellent beam quality, however, the maximum output power of a single fibre is limited.
Current research at the Institute of Technical Physics is focused on the radiation sources, the development of compact high power disc lasers and on concepts to couple several laser sources.