The combination of advanced functional materials with high optical performance and cutting-edge micro/nano fabrication technology has ushered in a new era for integrated photonics.Thin-film lithium niobate(TFLN)has emerged as a promising material platform for the next generation photonic integrated circuits(PICs),owing to its wide transparency window from UV to mid-IR,moderately high refractive index that enables dense photonic integration while maintaining a suitable mode-size in the single-mode lithium niobate(LN)ridge waveguide,and large electro-optic(EO)as well as nonlinear optical coefficients which are critical for high-speed EO tuning and high-efficiency wavelength conversion applications.Photolithography assisted chemo-mechanical etching(PLACE),a technique developed specifically for fabricating high quality(high-Q)large-scale PICs on TFLN,has enabled fabrication of a series of building blocks of PICs ranging from high-Q micro-resonators and low-loss waveguides to waveguide amplifiers,arrayed waveguide grating(AWG)and electro optically tunable/programmable photonic circuits,showing high optical performance,such as,1.2 × 108-ultra-high-Q micro-resonator,0.025-dB/cm ultra-low-loss continuously tunable delay line,20-dB gain waveguide amplifier and 1.5-mW total power consumption matrix operation devices.Aiming at high-throughput manufacturing of the PIC devices and systems,we have developed an ultra-high-speed high-resolution laser lithography fabrication system employing a high repetition-rate femtosecond laser and a high-speed polygon laser scanner,achieving infinite field of vision(IFOV)processing,by which a lithography fabrication efficiency of 4.8 cm2/h has been achieved at a spatial resolution of 200 nm.Using the high-speed femtosecond laser lithography system,we successfully fabricate photonic structures of large footprints with reasonable propagation loss.By combining the previous femtosecond scan scheme for smoothing mask edges with a high-speed polygon scan scheme for patterning the waveguide groove part,we further improve the propagation loss.We also demonstrate wafer-scale fabrication of microelectrode structures,showing high uniformity in the fabrication process,and high-speed Mach-Zehnder interferometer(MZI)modulators.By characterizing EO performance of the MZI modulator,we achieve a voltage-length product of 1.86 V cm and a measured 3-dB bandwidth up to 70 GHz.With the continuous advances in the high-repetition-rate femtosecond laser,high-speed electronic shutter/controller and high-speed host data transmission technology,we expect the fabrication efficiency and propagation loss can be further promoted by 1-2 orders of magnitude.This will have a profound implication as miniaturization will play a central role in future society.
关键词
薄膜铌酸锂/光子集成电路/光刻/飞秒激光微加工
Key words
thin film lithium niobate/photonic integrated circuit/photolithography/femtosecond laser micromachining
维普
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