Group: Single Frequency Lasers

The Single Frequency Lasers group (SFL) has been split off the group Solid State Photonics (SSP) at the end of 2006. Particularly the laser development for earth-bound gravitational wave observatories has been transferred to this new group.

Currently, a multi-stage, single-frequency high power laser system is being developed for the next generation of gravitational wave detectors. This system is based on a high power oscillator which will be coupled to the existing 35 W systems. This combination will allow a power scaling of up to 200 W while the excellent beam quality and single-frequency emission will be maintained. This development of the high power oscillator is done in several stages. In 2008, the “functional prototype” has been built. With this prototype, all laser system specifications have been demonstrated. In mid 2009, the “engineering prototype” has been realized (Figs. 1 and 2). This prototype had been designed to fulfill all optical specifications and come as close as possible to the final design regarding the mechanical design.

Within the cluster of excellence QUEST, the Junior Research Group “3rd generation gravitational wave detector laser source” has been established within the group SFL. This Junior Research Group is responsible for the development of laser sources and concepts for the third generation of gravitational wave detectors. Here, two wavelength ranges are addressed simultaneously: 1064 nm and 1550 nm. In the 1 µm range previous results with fiber amplifiers are building the basis for further power scaling up into the kW range. This goal will be realized by a combination of fiber and solid state amplifiers systems. In these investigations, the focus will be laid on the conservation of the excellent beam quality and the frequency and power stability. In the 1.55 µm range, which is already well understood in the small single regime due to the activities in the telecom industry, fundamental experiments are carried out in order to scale the output power towards some 100 W. In particular, Er-doped and Er/Yb-codoped fiber amplifiers are compared. Like in the 1 µm range, the conservation of a pure TEM00 emission and the impact of various parameters on the frequency and power stability are the most important issues in the investigations.

Figure 1: Mechanical design of the engineering prototype


Figure 2: Actual realisation of the engineering prototype