Heterodyne coherent detection of phase modulation in a mid-infrared unipolar device
Hamza Dely, Baptiste Chomet, Thomas Bonazzi, Djamal Gacemi, Angela Vasanelli, Axel Evirgen, Olivier Lopez, Benoît Darquié, Filippos Kapsalidis, Jérôme Faist, Carlo Sirtori
Abstract
Phase modulation is demonstrated in a quantum Stark effect modulator designed to operate in the mid-infrared at wavelength around 10 µm. Both phase and amplitude modulation are simultaneously resolved through the measurement of the heterodyne signal arising from the beating of a quantum cascade laser with a highly stabilized frequency comb. The highest measured phase shift is more than 5 degrees with an associated intensity modulation of 5 %. The experimental results are in full agreement with our model in which the complex susceptibility is precisely described considering the linear voltage dependent Stark shift of the optical resonance.