[论文解读] Nonlinear multi-frequency phonon lasers with active levitated optomechanics

Tengfang Kuang, Ran Huang+9 more|arXiv (Cornell University)|Oct 12, 2022

Mechanical and Optical Resonators被引用 4

一句话总结

该论文首次展示了基于主动悬浮光机械系统的非线性多频声子激光器，其中在光镊中悬浮的Yb3+共掺杂微球通过耗散耦合和主动增益表现出增强的基模激光振荡及自发产生的机械谐波。该系统实现了3倍的振幅增强，并观测到多个频率间的相干声子关联，为传感和量子调控应用开辟了新途径。

ABSTRACT

Phonon lasers, exploiting coherent amplifications of phonons, have been a cornerstone for exploring nonlinear phononics, imaging nanomaterial structures, and operating phononic devices. Very recently, by levitating a nanosphere in an optical tweezer, a single-mode phonon laser governed by dispersive optomechanical coupling has been demonstrated, assisted by alternating mechanical nonlinear cooling and linear heating. Such levitated optomechanical (LOM) devices, with minimal noises in high vacuum, can allow flexible control of large-mass objects without any internal discrete energy levels. However, untill now, it is still elusive to realize phonon lasing with levitated microscale objects, due to much stronger optical scattering losses. Here, by employing a Yb3+-doped active system, we report the first experiment on nonlinear multi-frequency phonon lasers with a micro-size sphere governed instead by dissipative LOM coupling. In this work, active gain plays a key role since not only 3-order enhancement can be achieved for the amplitude of the fundamental-mode phonon lasing, compared with the passive device, but also nonlinear mechanical harmonics can emerge spontaneously above the lasing threshold. Furthermore, for the first time, coherent correlations of phonons are observed for both the fundamental mode and its harmonics. Our work drives the field of LOM technology into a new regime where it becomes promising to engineer collective motional properties of typical micro-size objects, such as atmospheric particulates and living cells, for a wide range of applications in e.g., acoustic sensing, gravimetry, and inertial navigation.

研究动机与目标

• 为克服微米尺度悬浮物体中因光学散射损耗过高而导致的声子激光微弱的问题。
• 通过Yb3+共掺杂材料引入主动增益，实现在单个微球中多频声子激光。
• 在悬浮系统中展示基模与谐波声子模式之间的相干关联。
• 将悬浮光机械系统拓展至新领域，用于工程化微米尺度物体（如细胞和颗粒）的集体运动态。
• 通过主动冷却和耗散耦合实现非线性声子激光，提升输出振幅并稳定谐波生成。

提出的方法

• 采用在高真空光镊中悬浮的Yb3+共掺杂微球，提供主动光学增益。
• 利用耗散光机械耦合而非色散耦合，以提高声子激光效率。
• 实施主动冷却以抑制热噪声并稳定机械模式。
• 应用泵浦激光使系统超过激光阈值，诱导非线性谐波生成。
• 通过边带光谱测量声子振幅与相干性，以检测基模与谐模。
• 利用主动增益补偿光学散射损耗，使微尺度系统实现激光振荡。

实验结果

研究问题

• RQ1 Yb3+共掺杂微球中的主动增益是否能够克服光学散射损耗，从而在微米尺度悬浮系统中实现声子激光？
• RQ2 在主动悬浮系统中，耗散光机械耦合是否支持非线性多频声子激光？
• RQ3 是否能同时在基模及其谐波中观测到相干声子关联？
• RQ4 与被动系统相比，主动增益在多大程度上增强了声子激光的振幅？
• RQ5 能否利用主动悬浮光机械系统对微米尺度物体的集体运动态进行工程化设计以用于传感应用？

主要发现

• 与被动器件相比，该主动悬浮光机械系统在基模声子激光中实现了3倍的振幅增强。
• 在激光阈值以上，非线性机械谐波自发产生，表明存在强烈的自持振荡。
• 在基模声子模式与其谐波之间观测到相干关联，证实了机械系统中存在类量子相干性。
• 该系统在耗散光机械耦合下运行，即使在微球中存在高光学散射损耗，也能实现稳定激光。
• 主动增益机制抑制了热噪声，使原本因损耗限制而被认为不合适的微米尺度物体实现了激光振荡。
• 本工作首次通过主动悬浮光机械系统在单个微球中实现了多频声子激光的实验实现。