Carrier envelope phase stabilization with a true common-path collinear ƒ–2ƒ interferometer

Abstract

A variety of technologies have been so far demonstrated for the carrier-envelope phase (CEP) control of mode-locked oscillators. An instrumental part of these technologies is the configuration of interferometers and the application of feedback control. Of the devices, the collinear ƒ–2ƒ interferometer developed in this work is compact and robust against disturbances because the optical paths of the ƒ and 2ƒ components are collinear within the interferometer. To compensate for the delay time between the ƒ and 2ƒ components, a birefringent time plate made of α-BBO is installed in the interferometer. We achieved an in-loop CEP stability of 27 mrad (rms) using conventional feedback control with an acousto-optic modulator to control the pump power. We believe that the collinear ƒ–2ƒ interferometer offers the best choice as an interferometer for CEP stabilization of the front-end oscillator in the chirped-pulse amplification system.