Radiation hard mode-locked laser suitable as a spaceborne frequency comb

Towards a space-qualified Kerr-lens mode-locked laser

We report a 1.5-GHz Kerr-lens mode-locked (KLM) Yb:Y₂O₃ ring laser constructed by directly bonding the cavity components onto an aluminum baseplate. Stable unidirectional operation with an output power ≥10mW was obtained for pump-diode currents of 300-500 mA, corresponding to a total electrical power consumption of 1.5 W. After repetition rate stabilization, a comparison with a conventionally constructed identical laser showed a 50% reduction in phase noise. In free-running operation the bonded laser showed superior passive repetition rate stability. The bonding process follows an already proven integration approach in space-borne instrumentation, mapping a development pathway for KLM lasers in aerospace applications.

Octave-spanning optical frequency comb based on a laser-diode pumped Kerr-lens mode-locked Yb:KYW laser for optical frequency measurement

We developed an optical frequency comb based on a Yb:KYW laser. Soft-aperture Kerr-lens mode-locking at the cavity transverse-mode degeneration enabled us to generate 360 mW from a 750 mW pump laser diode. This resulted in spectral broadening over one octave using just a photonic crystal fiber. We achieved a free-running linewidth of 15 kHz in the carrier-envelope offset frequency by optimizing the cavity group delay dispersion, crystal position, and pump laser power, which led to a residual phase noise of 0.51 rad during phase-locking. We measured the frequency drift of a cavity-stabilized laser for a clock transition in Yb171⁺.

Ultra-low phase-noise microwave generation using a diode-pumped solid-state laser based frequency comb and a polarization-maintaining pulse interleaver

We report ultra-low phase-noise microwave generation at a 9.6 GHz carrier frequency from optical frequency combs based on diode-pumped solid-state lasers emitting at telecom wavelength and referenced to a common cavity-stabilized continuous-wave laser. Using a novel fibered polarization-maintaining pulse interleaver, a single-oscillator phase-noise floor of -171 dBc/Hz at 10 MHz offset frequency has been measured with commercial PIN InGaAs photodiodes, constituting a record for this type of detector. Also, a direct optical measurement of the stabilized frequency combs' timing jitter was performed using a balanced optical cross correlator, allowing for an identification of the origin of the phase-noise limitations in the system.