Generation of Expanded Optical Frequency Combs

Abstract

We present a method to expand optical frequency combs (OFC) using self-phase modulation in an optical fiber. The initial OFC is generated using a resonant electro-optic modulator and exhibits a span of less than 10 THz. The span of a broadened OFC can reach up to 50 THz in the 1.5 µm wavelength domain. Second-Harmonic Generation (SHG) of this OFC has also been demonstrated. The span of a second-harmonic comb can also reach up to 50 THz but in the 0.8 µm region. We also demonstrate an innovative method to make frequency-difference measurements between two laser signals when the difference frequency between the lasers is larger than the span of the OFC.