Steering optical comb frequency by rotating polarization state

TL;DR

This paper introduces a novel polarization-based frequency control method for optical combs using an intra-cavity electro-optic modulator, achieving larger dynamic range and fewer side effects than traditional techniques.

Contribution

A new polarization tuning approach using birefringence for broadband, large-dynamic frequency control in mode-locked lasers is developed and demonstrated.

Findings

Frequency control range increased by at least an order of magnitude.

Method exhibits fewer side effects compared to traditional techniques.

Broadband and large-dynamic control achieved through polarization manipulation.

Abstract

Optical frequency combs, with precise control of repetition rate and carrier-envelope-offset frequency, have revolutionized many fields, such as fine optical spectroscopy, optical frequency standards, ultra-fast science research, ultra-stable microwave generation and precise ranging measurement. However, existing high bandwidth frequency control methods have small dynamic range, requiring complex hybrid control techniques. To overcome this limitation, we develop a new approach, where a home-made intra-cavity electro-optic modulator tunes polarization state of laser signal rather than only optical length of the cavity, to steer frequencies of a nonlinear-polarization-rotation mode-locked laser. By taking advantage of birefringence of the whole cavity, this approach results in not only broadband but also relative large-dynamic frequency control. Experimental results show that frequency control dynamic range increase at least one order in comparison with the traditional intra-cavity electro-optic modulator technique. In additional, this technique exhibits less side-effect than traditional frequency control methods.