Ultrabroadband Integrated Electro-Optic Frequency Comb in Lithium Tantalate

Abstract

Chip-scale optical frequency combs have unlocked a wide range of applications, from coherent sensing, low-noise microwave synthesis to massively parallel coherent optical telecommunications and computations. Recent advances in thin-film lithium niobate (LiNbO<inf>3</inf>) have enabled integrated electro-optic combs (EO combs) [1,2]. However, current lithium niobate EO combs is limited by birefringence-induced mode-crossings and the inefficient microwave power usage, limiting the maximum attainable bandwidth below 150nm. In this work, we address both challenges by co-designing monolithic integrated microwave resonators with lithium tantalate (LiTaO<inf>3</inf>) photonics integrated circuits [3], which has 17 times lower birefringence. We demonstrated a >450nm span EO comb with 30GHz repetition rate.