Passively stable 0.7-octave microcombs in thin-film lithium niobate microresonators

The optical frequency comb based on microresonators(microcombs)is an integrated coherent light source and has the potential to promise a high-precision frequency standard;self-reference and a long-term stable microcomb are the keys to this realization.Here,we demonstrated a 0.7-octave spectrum Kerr comb via dispersion engineering in a thin-film lithium niobate microresonator,and the single-soliton state can be accessed passively with long-term stability over 3 h.With such a robust broadband coherent comb source using thin-film lithium niobate,a fully stabilized microcomb can be expected for massive practical applications.

High peak power femtosecond cylindrical vector beams generation in a chirped-pulse amplification laser system

Cylindrical vector beams(CVBs),with non-uniform state of polarizations,have become an indispensable tool in many areas of science and technology.However,little research has explored high power CVBs at the femtosecond regime.In this paper,we report on tne generation of high quality CVBs with high peak power and femtosecond pulse duration in a fiber chirped-pulse amplification laser system.The radially(azimuthally)polarized vector beam has been obtained with a pulse duration of 4A0 fs[430 fs]and a maximum average output power of 20.36 W[20.12 W].The maximum output pulse energy is〜20μJ at a repetition rate of 1 MHz,corresponding to a high peak power of-46 MW.The comparison between simulated intensity profiles and measured experimental results suggests that the generated CVBs have a remarkable intensity distribution.The proposed configuration of our laser system provides a promising solution for high quality CVBs generation with the characteristics of high peak power,ultrashort pulse duration,and high mode purity.

Heterogeneous integrated phase modulator based on two-dimensional layered materials

Silicon nitride,with ultralow propagation loss and a wide transparency window,offers an exciting platform to explore integrated photonic devices for various emerging applications.It is appealing to combine the intrinsic optical properties of two-dimensional layered materials with high-quality optical waveguides and resonators to achieve functional devices in a single chip.Here we demonstrate a micro-ring resonator-based phase modulator integrated with few-layer MoS_(2).The ionic liquid is employed directly on the surface of MoS_(2) to form a capacitor configuration.The effective index of the composite MoS_(2)–SiN waveguide can be modulated via adjusting bias voltages to achieve different charged doping induced electro-refractive responses in MoS_(2) film.The maximum effective index modulation of the composite MoS_(2)–SiN waveguide can be achieved to 0.45×10^(−3).The phase tuning efficiency is measured to be 29.42 pm/V,corresponding to a V_(π)L of 0.69 V·cm.Since the micro-ring resonator is designed near the critical coupling regime,the coupling condition between the bus waveguide and micro-ring resonator can also be engineered from under-coupling to over-coupling regime during the charged doping process.That can be involved as a degree of freedom for the coupling tailoring.The ability to modulate the effective index with two-dimensional materials and the robust nature of the heterostructure integrated phase modulator could be useful for engineering reliable ultra-compact and low-power-consumption integrated photonic devices.