分类： 光学 >> 量子光学 提交时间： 2023-02-19
Lei Wan
Zhiqiang Yang
Wenfeng Zhou
Meixun Wen
Tianhua Feng
Siqing Zeng
Dong Liu
Huan Li
Jingshun Pan
Ning Zhu
Weiping Liu
Zhaohui Li
摘要： A highly efficient on-chip acousto-optic modulator, as a key component, occupies an exceptional position in microwave-to-optical conversion. Homogeneous thin-film lithium niobate is preferentially employed to build the suspended configuration forming the acoustic resonant cavity to improve the modulation efficiency of the device. However, the limited cavity length and complex fabrication recipe of the suspended prototype restrain further breakthrough in the modulation efficiency and impose challenges for waveguide fabrication. In this work, based on a nonsuspended thin-film lithium niobate-chalcogenide glass hybrid Mach-Zehnder interferometer waveguide platform, we propose and demonstrate a built-in push-pull acousto-optic modulator with a half-wave-voltage-length product as low as 0.03 V cm, presenting a modulation efficiency comparable to that of the state-of-the-art suspended counterpart. Based on the advantage of low power consumption, a microwave modulation link is demonstrated using our developed built-in push-pull acousto-optic modulator. The nontrivial acousto-optic modulation performance benefits from the superior photoelastic property of the chalcogenide membrane and the completely bidirectional participation of the antisymmetric Rayleigh surface acoustic wave mode excited by the impedance-matched interdigital transducer, overcoming the issue of amplitude differences of surface acoustic waves applied to the Mach-Zehnder interferometer two arms in traditional push-pull acousto-optic modulators.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The multimode waveguide bends (MWBs) with very compact sizes are the key building blocks in the applications of different mode-division multiplexing (MDM) systems. To further increase the transmission capacity, the silicon multimode waveguide bends for dual polarizations are of particular interest considering the very distinct mode behaviors under different polarizations in the silicon waveguides. Seldom silicon MWBs suitable for both polarizations have been studied. In this paper we analyze several dual-polarization-MWBs based on different bending curve functions. These special curve-based silicon MWBs have the advantages of easy fabrication and low loss compared with other structures based on the subwavelength structures such as gratings. A comparison is made between the free-form curve, Bezier curve, and Euler curve, which are used in the bending region instead of a conventional arc. The transmission spectra of the first three TE and TM modes in the silicon multimode waveguide with a core thickness of 340 nm are investigated. The simulation results indicate that in the premise of the same effective radius which is only 10 in this paper, the 6-mode MWB based on the free-form curve has the optimal performances, including an extremely low loss below 0.052dB and low crosstalk below -25.97dB for all six modes in the wide band of 1500-1600 nm. The MWBs based on the Bezier and Euler curve have degraded performances in terms of the loss and crosstalk. The results of this paper provide an efficient design method of the polarization insensitive silicon MWBs, which may leverage the researches for establishing complicated optical transmission systems incorporating both the MDM and polarization-division multiplexing (PDM) technology.
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