A Micro-Integrated Mode-Locked Extended-Cavity Diode Laser Emitting in the Wavelength Range Around 780 nm

Mode-locked ultra-short pulse lasers are invaluable tools in a multitude of applications ranging from medical imaging to quantum optical sensors testing fundamental physics. One application that can benefit from an optical frequency comb (OFC) generated by such a laser is the test of the Universality of Free Fall (UFF) using potassium (K) and rubidium (Rb) ultra-cold quantum gases in micro-gravity. By means of an OFC, the frequency difference of only about 13 nm (767 nm, K, to 780 nm, Rb) can easily be bridged. This allows for use of compact robust space-suitable mode-locked diode lasers instead of, e.g., highly complex mode-locked fiber lasers. Here, we present an important step in this direction, i.e. a micro-integrated passively mode-locked extended-cavity diode laser (ECDL) module providing a spectral bandwidth of more than 10 nm in the wavelength range around 780 nm.