Frequency stabilisation of single emitters and the effect on the beam quality

We present the improvement of the lateral beam quality due to frequency stabilisation in a Dense Wavelength Division Multiplexing setup using Volume Bragg Gratings. The spectral width of each frequency stabilised channel amounts to less than 300 pm and an overall multiplexing efficiency of 86 % has been measured. The near and far field intensity distributions consist of discrete modes and were observed with a post positioned beam analysis module. When operated with frequency stabilisation, the lateral beam quality factor M² of the single emitters decreased by a factor of 1.4 on average compared to the free running source.