Figure 1: Experimental setup for phase measurement of optical frequency comb modes.
From: Phase steps and resonator detuning measurements in microresonator frequency combs
(a) An amplified external cavity diode laser generates an optical frequency comb in a microresonator. The comb output is sent into a waveshaper that allows to control phases and amplitudes of individual comb modes. A first feedback loop is used to flatten the amplitude of the comb modes. Subsequently, the phases of the comb modes are retrieved by iteratively changing the phases until the shortest possible pulse with highest peak power is measured in an autocorrelator. The measured phases are corrected for the dispersion of the setup, which is measured with a reference pulse. Amp, Erbium-doped fibre amplifier; ECDL, external cavity diode laser; OSA, optical spectrum analyser; PBS, polarizing beam splitter; PD, photodiode; Pol, polarization controller; SHG, second harmonic generation. (b) Sinusoidal change of the autocorrelation peak response when changing the phase of a single comb mode out of 10 modes. The error on the retrieved phase (position of the peak of the sine) is <0.03 radians.
