Gallium phosphide offers an attractive combination of a high refractive index ($n>3$ for vacuum wavelengths up to 4 μm) and a wide electronic bandgap (2.26 eV), enabling optical cavities with small mode volumes and low two-photon absorption at telecommunication wavelengths. Heating due to strongly confined light fields is therefore greatly reduced. Here, we investigate the benefits of these properties for cavity optomechanics. Utilizing a recently developed fabrication scheme based on direct wafer bonding, we realize integrated one-dimensional photonic crystal cavities made of gallium phosphide with optical quality factors as high as $1.1\times {10}^5$. We optimize their design to couple the optical eigenmode at $\sim 200\mathrm{THz}$ via radiation pressure to a co-localized mechanical mode with a frequency of 3 GHz, yielding sideband-resolved devices. The high vacuum optomechanical coupling rate ($g_0=2\pi \times 400\mathrm{kHz}$) permits amplification of the mechanical mode into the so-called mechanical lasing regime with input power as low as $\sim 20\mathrm{\mu W}$. The observation of mechanical lasing implies a multiphoton cooperativity of $C>1$, an important threshold for the realization of quantum state transfer protocols. Because of the reduced thermo-optic resonance shift, optomechanically induced transparency can be detected at room temperature even in non-sideband-resolved devices in addition to the normally observed optomechanically induced absorption. Considering that GaP is also piezoelectric, these results establish GaP as an attractive material for future electro–opto-mechanical systems.

中文翻译：

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具有一维磷化镓光子晶体腔的光力学

磷化镓提供了高折射率的诱人组合（$ñ>3$适用于高达4μm的真空波长）和宽的电子带隙（2.26 eV），从而实现了具有小模量的光腔，并且在电信波长下的双光子吸收率低。因此，大大减少了由于强烈限制的光场而产生的热量。在这里，我们研究了这些特性对腔体光力学的好处。利用最近开发的基于直接晶圆键合的制造方案，我们实现了由磷化镓制成的集成一维光子晶体腔，其光学品质因数高达$1.1\times {10}^5$。我们优化他们的设计以耦合光学本征模$〜200\mathrm{太赫兹}$通过辐射压力达到频率为3 GHz的共定位机械模式，从而产生了边带分辨器件。高真空光机耦合率（$G_0=\mathrm{2个}\pi \times 400\mathrm{千赫}$）允许将机械模式放大到所谓的机械激射状态，输入功率低至 $〜20\mathrm{微瓦}$。机械激光的观察暗示了多光子的协同作用。$C>\mathrm{1个}$，这是实现量子状态转移协议的重要门槛。由于减少了热光共振位移，因此，除了通常观察到的光机械感应吸收之外，即使在非边带分辨的设备中，也可以在室温下检测光机械感应的透明性。考虑到GaP也是压电的，这些结果使GaP成为了未来机电系统的诱人材料。