Raman lasing and soliton mode-locking in lithium niobate microresonators

Abstract

The recent advancement in lithium niobate on insulator (LNOI) technology is revolutionizing the optoelectronic industry as devices of higher performance, lower power consumption, and smaller footprint can be realized due to the high optical confinement in the structures. The LNOI platform offers both large c (2) and c (3) nonlinearities along with the power of dispersion engineering, enabling brand new nonlinear photonic devices and applications towards the next generation of integrated photonic circuits. However, the Raman scattering, one of the most important nonlinear phenomena, have not been extensively studied, neither was its influences in dispersion-engineered LNOI nano-devices. In this work, we characterize the Raman radiation spectra in a monolithic lithium niobate (LN) microresonator via selective excitation of Raman-active phonon modes. Remarkably, the dominant mode for Raman oscillation is observed in the backward direction for a continuous-wave pump threshold power of 20 mW with a reportedly highest differential quantum efficiency of 46 %. In addition, we explore the effects of Raman scattering on Kerr optical frequency combs generation. We achieve, for the first time, soliton modelocking on a X-cut LNOI chip through sufficient suppression of the Raman effect via cavity geometry control. Our analysis of the Raman effect provides guidance for the development of future chip-based photonic devices on the LNOI platform.

Microstructure and domain engineering of lithium niobate crystal films for integrated photonic applications

“…Nevertheless, microresonators with specific structures need to be designed to achieve highly efficient nonlinear frequency conversion 80 . Moreover, cascaded Raman scattering and frequency-doubled emission of Raman lines were observed at the microring resonators with a Q value of up to 10 6 88 , 89 . An innovative tuneable coupling scheme to optimize the coupling was demonstrated for nonlinear optical processes by changing the distance between the coupling waveguide and the WGR in the z-direction.…”

Nonlinear wave mixing in lithium niobate thin film

“…In addition, there are other nonlinear phenomena in LNTF but are not included in the previous paragraphs due to the space limit. They are Raman lasing [86] and acousto-optics effects [87]. LN with large electromechanical transduction efficiency can be used in acousto-optic coupling for Brillouin integrated photonics.…”

Kerr-Raman Optical Frequency Combs in Silica Microsphere Pumped Near Zero Dispersion Wavelength

“…Many regimes of OFC generation achieved in on-chip WGMRs were also investigated in silica MSs and even observed for the first time, which enabled a significant progress in understanding nonlinear physics or discovering new effects. For example, Raman lasing was first demonstrated in a silica MS [14] and after that investigated on the basis of this and other platforms [15][16][17][18][19][20][21][22]. Kerr and Kerr-Raman OFCs generation was also investigated experimentally in a silica MS [16].…”