Optical isolators,the photonic analogs of electronic diodes,are essential for ensuring the unidirectional flow of light in optical systems,thereby mitigating the destabilizing effects of back reflections.Thin-film lithium niobate(TFLN),hailed as“the silicon of photonics,”has emerged as a pivotal material in the realm of chip-scale nonlinear optics,propelling the demand for compact optical isolators.We report a breakthrough in the development of a fully passive,integrated optical isolator on the TFLN platform,leveraging the Kerr effect to achieve an impressive 10.3 dB of isolation with a minimal insertion loss of 1.87 dB.Further theoretical simulations have demonstrated that our design,when applied to a microring resonator with a Q factor of 5×10^(6),can achieve 20 dB of isolation with an input power of merely 8 mW.This advancement underscores the immense potential of lithium niobate-based Kerr-effect isolators in propelling the integration and application of high-performance on-chip lasers,heralding a new era in integrated photonics.
Erbium-doped lithium niobate(LN)on insulator active devices,such as lasers and amplifiers,have received increasing attention.The nonlinear optical oscillation in them at high power destabilizes the output of signals and cannot be ignored.In this study,we reported the experimental observation and theoretical analysis of the nonlinear optical oscillation in erbiumdoped lithium niobate-on-insulator(LNOI)microring resonators while scanning the pump wavelength.Under the same pump power,the number of oscillation cycles decreases when the wavelength scanning rate increases from 10.6 to 33.9 nm/μs.A theoretical model based on the competition between the thermo-optic nonlinearity and the photorefractive effect was introduced to interpret the oscillation in transmission.A series of parameters were obtained from the comparison between the theoretical and experimental results;some of them,the relaxation rates of the thermal and the electric field,are significantly different from those of undoped LNOI microcavities.This work provides a valuable reference for future applications of active LNOI devices.
The expansive spectral coverage and superior optical properties of lithium niobate(LN)offer a comprehensive suite of tools for exploring novel functionalities.Achieving high-quality(Q)photonic resonator cavities is crucial for enhancing light-matter interactions.However,this task is challenging as the device performance is heavily dependent on the fabrication quality of the LN.In this paper,we present experimental validation of an etchless approach to fabricating high-Q photonic crystal nanobeam cavities(PCNBCs).We successfully fabricate PCNBCs with Q factors exceeding 105 while maintaining high transmittance by capitalizing on the low waveguide loss and high fabrication tolerance of TE-polarized mode.Remarkably,the Q factor achieved here exceeds previous reports on etchless LN PCNBCs by over an order of magnitude.Benefiting from this advancement,we further explore a variety of optical functions,including thermo-optic tuning,optically induced bistability,and Fano line shapes generation.These findings present promising prospects for a versatile platform technique,facilitating the development of high-performance electro-optic or acousto-optic modulators,optical logic devices,and quantum photonics,highlighting its significant impact in the field of photonic integration.
This paper presents the design,fabrication,and characterization of a high-performance heterogeneous silicon on insulator(SOI)/thin film lithium niobate(TFLN)electro-optical modulator based on wafer-scale direct bonding followed by ion-cut technology.The SOI wafer has been processed by an 8 inch standard fabrication line and cut into 6 inch for direct bonding with TFLN.The hybrid SOI/LN electro-optical modulator operated at the wavelength of 1.55μmis composed of couplers on the Si layer and aMach-Zehnder interferometer(MZI)structure on theLNlayer.The fabricated device exhibits a stable value of the product of half-wave voltage and length(V_(π)L)of around 2.9 V·cm.It shows a good low-frequency electro-optic response flatness and supports 96 Gbit/s data transmission for the NRZ format and 192 Gbit/s data transmission for the PAM-4 format.
This article introduces a method of achieving high polarization extinction ratio using a subwavelength grating structure on a lithium niobate thin film platform,and the chip is formed on the surface of the lithium niobate thin film.The chip,with a length of just 20μm,achieved a measured polarization extinction ratio of 29 dB at 1550 nm wavelength.This progress not only proves the possibility of achieving a high extinction ratio on a lithium niobate thin film platform,but also offers important technical references for future work on polarization beam splitters,integrated fiber optic gyroscopes,and so on.
YANG Yong-KangGUO Hong-JieCHEN Wen-BinQU Bai-AngYU Zhi-GuoTAN Man-QingGUO Wen-TaoLIU Hai-Feng
