Anisotropic Thermo‐Optic Mach–Zehnder Interferometer on LNOI for Polarization Handling and Multiplexing

Abstract

Thin‐film lithium niobate (LN) on insulator (LNOI) is emerging as a promising integrated photonic platform. Thermo‐optic (TO) Mach–Zehnder interferometers (MZIs) on LNOI are demonstrated to be a viable and often preferred alternative to their electro‐optic counterparts for low‐speed and static applications, where stability and repeatability are crucial. Harnessing the unique and strong anisotropic TO effect of LN, a novel and versatile anisotropic TO MZI on x‐cut LNOI for polarization handling and multiplexing is proposed and experimentally implemented. Each MZI arm consists of a two‐section anisotropic TO phase shifter along the y‐ and z‐directions of the LN crystal, leading to anisotropic temperature dependence of the effective refractive indices for the transverse‐electric (TE) and transverse‐magnetic (TM) polarizations. A polarization‐insensitive switch and a polarization beam splitter are implemented with the MZI device, which features low excess loss of ≈0.2–1.8 dB and a high extinction ratio of ≈20–45 dB in the telecom C‐band (1530–1565 nm). More intriguingly, arbitrary splitting ratios and even arbitrary combinations of unitary transmission matrices can be further implemented for both polarizations simultaneously. The versatile configurations of this anisotropic TO MZI have important implications for large‐scale photonic computing and interconnect.

On-chip tunable quantum interference in a lithium niobate-on-insulator photonic integrated circuit

“…In conclusion, we have demonstrated a 2 × 2 MZI monolithically integrated on the LNOI platform. The device uses TOPS to introduce phase shifts which feature a low P π = 44.4 mW achieved with CMOS compatible voltages below 5 V. The power consumption is among the lowest ever reported in comparable structures [35,36], and can be boosted using thermal isolation trenches [37]. We showed that the thermo-optically tuned MZI can reach extinction ratios above 31 dB symmetrically on both ports and reached optical response times as low as 0.7 µs by employing an overdrive protocol.…”

Study for Photo-Induced Enhanced Raman Spectroscopy with Laser-Induced Periodic Surface Structures on Lithium Niobate on Insulator

“…Generally, LNOI is composed of a single-crystal LN film bounded to a SiO 2 interlayer with a bulk LN or Si substrate used as the carrier wafer . The excellent electro-optic, acousto-optic, ferroelectric, and nonlinear optical properties of LNOI retained from the LN crystal, − in company with its high refractive index contrast (∼0.7) and extremely compact structure, make it promising in the area of integrated photonic devices and in biophotonics applications including SERS detection. − Furthermore, the intrinsic roughness and defects formed during the fabrication process of LNOI provide additional defect levels and therefore make it more suitable for PIERS than LN bulk crystals. , However, the origin of LNOI-based PIERS is far from being thoroughly demonstrated.…”