Fiber-coupled external cavity DFB-laser

Narrow-linewidth, compact and robust laser systems are of high interest, especially with prospects for portable quantum metrological applications. We realized an external cavity DFB-laser incorporating an intra-cavity EOM in a fully fiber-coupled manner. Additional active feedback on the EOM, by referencing a high finesse cavity, enabled us to reach low kHz-linewidths. We analyzed the laser spectrum by means of delayed self-heterodyne measurements to reconstruct the power spectral density. This is achieved by utilizing a data-driven power spectrum equalization approach. The presented laser setup is successfully used to create an ultracold gas by laser cooling on a narrow atomic transition of ${}^{40}$Ca at 1978 nm.