We turned on the high-power laser amplifier (NKT photonics Koheras Boostik) for the first time today, producing a high-power beam (did not measure the power yet, amplifier specs says it should be ~1.5W).

The input beam for the amplifier is supplied by the seed laser (Thorlabs ULN15TK), which produces ~50 mW of optical power. To attenuate this power to below the amplifiers max input power spec, the amplifier input power is controlled through a paddle polarisation controller and a polarising beamsplitter (PBS). One of the output ports of the PBS is connected to the input of the amplifier, the beam from the unused PBS output port can be used a monitor or dumped (see attached photo). Touching the non-polarisation maintaining fibres (yellow) upstream of the PBS results in power fluctuations of the seed beam and should be avoided (though they are clamped down so the effect of accidental touches is minimal).

The output of the amplifier is directed through the corner of a beamsplitter cube to create a low power beam from the reflection of the front surface AR coating. The high-power transmitted beam is dumped. The low power beam will be used to characterise the amplifier output.