Walking along a beach one may notice debris being washed ashore from the vast oceans. Then, turning your head up at night you even might noticed a shooting star or a bright spot passing by. Chances are, that you witnessed space debris, endangering future space flight in lower earth orbit. If it was possible to turn cm-sized debris into shooting stars the problem might be averted. Unfortunately, these fragments counting in the 100 thousands are not controllable. To possibly regain control we demonstrate how to exert forces on a free falling debris object from a distance by ablating material with a high energy ns-laser-system. Thrust effects did scale as expected from simulations and led to speed gains above 0.3 m/s per laser pulse in an evacuated micro-gravity environment.

A longitudinal mode-locked state can be converted to a transverse mode-locked state by exploiting the spectral and spatial filtering of an empty optical resonator. Carrier and amplitude modulation sidebands were simultaneously transmitted by the conversion resonator, yielding phase-locked superpositions of up to five transverse modes. Equivalently, an amplitude-modulated beam was converted into a beam that periodically moved across the transverse plane. Precise control over the spatial beam shape during oscillation was gained by independently altering the set of transverse modes and their respective powers, which demonstrated an increased level of control in the generation of transverse mode-locked states.

Coherent beam combining and the development of thin-disk lasers have provided the ability to increase the output power of solid-state laser systems. Here, coherent beam combining by active phase control of one multipass thin-disk laser amplifier and one similar multipass setup is demonstrated with powers below 100 mW. Piston phase disturbances are measured via optical heterodyne detection and compensated for by piezo mirrors. For one double pass over the disk, a root mean square phase error of λ/69 was achieved. Mechanical vibrations < 5 kHz inside the multipass setup caused by the water cooling of the disk are the main source of phase noise. Thermal effects by the pumping diodes with 1 kW of optical power are negligible.