Microwave photonics, a field that crosscuts microwave/millimeter-wave engineering with optoelectronics, has sparked great interest from research and commercial sectors. This multidisciplinary fusion can achieve ultrawide bandwidth and ultrafast speed that were considered impossible in conventional chip-scale microwave/millimeter-wave systems. Conventional microwave-to-photonic converters, based on resonant acousto-optic modulation, produce highly efficient modulation but sacrifice bandwidth and limit their applicability for most real-world microwave signal-processing applications. In this paper, we build highly efficient and wideband microwave-to-photonic modulators using the acousto-optic effect on suspended lithium niobate thin films. A wideband microwave signal is first piezoelectrically transduced using interdigitated electrodes into Lamb acoustic waves, which directly propagates across an optical waveguide and causes refractive index perturbation through the photoelastic effect. This approach is power-efficient, with phase shifts up to $0.0166\mathrm{rad}/\surd \mathrm{mW}$ over a 45 μm modulation length and with a bandwidth up to 140 MHz at a center frequency of 1.9 GHz. Compared to the state-of-the-art, a $9\times$ more efficient modulation has been achieved by optimizing the acoustic and optical modes and their interactions.

中文翻译：

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用于微波到光子转换的铌酸锂薄膜的高效宽带声光调制

微波光子学是一个将微波/毫米波工程与光电子学交叉的领域，引起了研究和商业部门的极大兴趣。这种多学科融合可以实现在传统芯片级微波/毫米波系统中被认为不可能实现的超宽带宽和超快速度。基于谐振声光调制的传统微波到光子转换器产生高效调制，但牺牲了带宽并限制了它们在大多数实际微波信号处理应用中的适用性。在本文中，我们利用悬浮铌酸锂薄膜的声光效应构建了高效、宽带的微波到光子调制器。首先使用交叉电极将宽带微波信号压电转换为兰姆声波，该声波直接穿过光波导传播并通过光弹性效应引起折射率扰动。这种方法是节能的，相移高达$0.0166\mathrm{弧度}/\surd \mathrm{兆瓦}$超过 45 μm 的调制长度和高达 140 MHz 的带宽，中心频率为 1.9 GHz。与最先进的技术相比，$9\times$ 通过优化声学和光学模式及其相互作用，实现了更有效的调制。