Erlangen 2018 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 62: Poster: Quantum Optics and Photonics V

Q 62.85: Poster

Thursday, March 8, 2018, 16:15–18:15, Redoutensaal

Phase lock between diode lasers — Stefan Baumgärtner, Manfred Hager, Christoph Raab, Stephan Ritter, and •Stephan Falke — TOPTICA Photonics AG, Lochhamer Schlag 19, 82166 Gräfelfing/München, Germany

Light emitted by cw lasers represents an oscillator with a high quality factor, which is the ratio of the frequency of the light and the linewidth of the laser. For free-running external cavity diode lasers (ECDL) it is typically about one million. By ensuring, in addition, that the absolute frequency of the laser is fixed, one is able to efficiently drive optical transitions of atoms, molecules and ions, e.g. for laser cooling, which relies on the high quality factor of the oscillator.

To stabilize the frequency difference between two lasers, phase locks are commonly applied. This allows for difference frequencies of several GHz and for a synchronization of the two oscillators, which is essential e.g. for addressing narrow two-photon resonances. Other application examples include lasers addressing atoms in high magnetic fields or the stabilization of cw lasers using a frequency comb.

Phase locking two laser fields to each other is possible by utilizing their beat signal, typically recorded with a fast photo-detector, and a fast feedback to one of the lasers. We realized a phase lock between two ECDLs and demonstrate 99% of phase locked light between two ECDL with free running linewidth of 100 kHz. We discuss the requirements on servo and laser, leading to a roll-over of the feedback at more than 1 MHz with commercially available components.