Bandwidth scaling of silicon modulator-based combs using multi-carriers and frequency offset locking

Optical frequency combs can be generated on-chip in silicon modulators through large signal modulation of an optical carrier. In this paper, a technique for bandwidth scale frequency combs generated from linear silicon modulators is proposed and experimentally demonstrated. This is accomplished by locking two frequency combs using a heterodyne optical frequency locked loop. We demonstrate here a proof of concept experiment of bandwidth-scaling of optical frequency combs generated in a silicon PN-modulator by frequency locking two 10 GHz repetition rate combs (6 lines each, 20-dB bandwidth), individually generated from two lasers offset by 50 GHz to each other using their respective overlapping comb lines. The resultant beat signal is stabilized at a heterodyne offset of 75 MHz to within a 3 dB linewidth of 4.305 MHz to achieve a bandwidth-scaled composite comb with 11 lines.