Poulsen Brett, Zylstra Michael, Sabarinathan Jayshri
Opt Express. 2025 Jan 27;33(2):1736-1748. doi: 10.1364/OE.537604.
Thermal engineering can be used to exploit absorption in a silicon optical cavity. In this work, the steady state profile of the heat generated by absorption is shaped and used to generate a dynamic heterostructure in a weakly confined silicon optical cavity. This is demonstrated in an edge defect photonic crystal optomechanical cavity to produce phonon lasing and sub-GHz optical pulsing with photon-phonon cooperativity of 0.088. It is typically challenging to meet the conditions for phonon lasing. The cooperativity must be at least unity, and the cavity operated in the optomechanical sideband resolved regime. Here, our thermal design uses absorption-generated heat to modify the refractive index of the cavity and dynamically form a heterostructure, compressing the optical mode volume and relaxing the constraints on the optical quality factor, mechanical quality factor, and threshold power. The compressed mode then couples to a thermo-optical/free-carrier-dispersion limit cycle, resonantly exciting the optomechanical cavity. While edge defects have been shown to have high optomechanical sensitivity, the cavity lacks sufficient mode confinement to generate the limit cycle without the thermal heterostructure. The formation of the heterostructure results in phonon lasing and sharp optical pulsing at 30 MHz. These results demonstrate the novel use of thermal engineering to initiate phonon lasing with further improvements leading to a fully integrated, sub-GHz optical frequency comb.
热工程可用于利用硅光腔中的吸收现象。在这项工作中，吸收产生的热量的稳态分布被塑造，并用于在弱受限硅光腔中产生动态异质结构。这在边缘缺陷光子晶体光机械腔中得到了证明，以产生声子激光和光子 - 声子合作系数为0.088的亚吉赫兹光脉冲。满足声子激光的条件通常具有挑战性。合作系数必须至少为1，并且腔要在光机械边带分辨 regime 下运行。在这里，我们的热设计利用吸收产生的热量来改变腔的折射率，并动态形成异质结构，压缩光学模式体积并放宽对光学品质因数、机械品质因数和阈值功率的限制。然后，压缩模式耦合到热光/自由载流子色散极限环，共振激发光机械腔。虽然边缘缺陷已被证明具有高光机械灵敏度，但在没有热异质结构的情况下，该腔缺乏足够的模式限制来产生极限环。异质结构的形成导致了30 MHz的声子激光和尖锐的光脉冲。这些结果证明了热工程在引发声子激光方面的新颖用途，随着进一步改进将导致完全集成的亚吉赫兹光学频率梳。
