Highly efficient acousto-optic modulation using nonsuspended thin-film lithium niobate-chalcogenide hybrid waveguides

Abstract

A highly efficient on-chip acousto-optic modulator is as a key component and occupies an exceptional position in microwave-to-optical conversion. Homogeneous thin-film lithium niobate is preferentially employed to build the suspended configuration for the acoustic resonant cavity, with the aim of improving the modulation efficiency of the device. However, the limited cavity length and complex fabrication recipe of the suspended prototype restrain further breakthroughs in 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 VπL as low as 0.03 V cm that presents a modulation efficiency comparable to that of a state-of-the-art suspended counterpart. A microwave modulation link is demonstrated using our developed built-in push-pull acousto-optic modulator, which has the advantage of low power consumption. 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 low modulation efficiency induced by the incoordinate energy attenuation of acoustic waves applied to the Mach–Zehnder interferometer with two arms in traditional push-pull acousto-optic modulators.

Perspective on Lithium-Niobate-on-Insulator Photonics Utilizing the Electro-optic and Acousto-optic Effects

“…80 For AO frequency shifters and single-sideband modulators, the operation frequency is expected to increase from MHz to GHz. 75,90,91 In addition, piezo-optomechanical crystals have also been demonstrated on thin-film LN, 77,78 which employ the interactions between photons and piezoelectrically excited phonons to achieve bidirectional transduction of both classical and quantum information between microwave and optical frequencies. This is an important emerging area that shares essentially the same operation principles as the new-generation AO devices.…”

“…It is also theoretically possible to achieve independent reconfigurations of multiple filter bands, with tunable time-variant spectral shapes by exciting several propagating acoustic waves of different frequencies simultaneously to form a time-variant synthetic waveguide grating . For AO frequency shifters and single-sideband modulators, the operation frequency is expected to increase from MHz to GHz. ,, …”

Coherent Phonon‐Induced Gigahertz Optical Birefringence and Its Manipulation in SrTiO3

“…[1] Birefringence is one of the key specifics, which arises from the electrically anisotropic of a material and it can modulate the polarization vector of an electromagnetic wave deterministically. [2] Favored by the wide range of applications, devices using birefringence have been commercially developed with long history, such as acousto-optic modulators/shifters, [3][4][5] dispersive filters, [6] polarization converters, [7] and retarder plates. Most of these devices can only work well up to megahertz (MHz) frequency.…”

Athermal Chalcogenide Microresonator Cladded With Polymer

“…C HALCOGENIDE glasses (ChGs) are one of the most broadly used optical materials due to their wide transparency window, high refractive index, low two-photon absorptions (TPA), negligible free-carrier effects and high nonlinearity [1], [2], [3]. In recent years, on-chip ChG photonic devices [1], [4], [5] can find a variety of interesting applications, including biochemical sensing [6], [7], broadband supercontinuum generation [8], [9], Raman lasing [10], [11], [12], acousto-optic modulation [13], [14] and optical frequency combs (OFCs) [15], [16]. One challenge in realizing high-performance ChG devices is the substantial thermo-refractive coefficient (TOC), which is incredibly not conducive to those phase-sensitive applications.…”