Optical detection of radio waves through a nanomechanical transducer
Optical detection of radio waves through a nanomechanical transducer
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DOI：
10.1038/nature13029
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发表时间：
2014-03-06
期刊：
影响因子：
64.8
通讯作者：
Polzik, E. S.
中科院分区：
文献类型：
--
作者：
Bagci, T.;Simonsen, A.;Polzik, E. S.
微弱射频和微波信号的低损耗传输及灵敏恢复是一个普遍存在的挑战，在射电天文学、医学成像、导航以及经典和量子通信中至关重要。将射频信号高效上转换到光载波上，能够使其通过光纤而非铜线传输，从而大幅降低损耗，并且能够利用在量子受限信号检测中常规使用的一系列成熟的量子光学技术。腔光力学研究（1,2）表明，纳米机械振荡器能够与微波（3 - 5）或光场（6,7）强烈耦合。在此，我们根据近期的一项提议（8），利用一个高品质的纳米薄膜展示了一种具有这两种功能的室温光电机械换能器。小于10伏的电压偏置足以在射频谐振电路的电压波动和薄膜的位移之间诱导出强耦合（4,6,7），而薄膜位移同时与从其表面反射的光耦合。射频信号被检测为具有量子受限灵敏度的光相移。相应的半波电压在微伏范围内，比标准光调制器低几个数量级。换能器的噪声——除了已测量到的谐振电路的800皮伏每平方根赫兹的约翰逊噪声外——由光的量子噪声和薄膜的热波动组成，在射电天文学和核磁共振成像的潜在应用中主导着噪声基底。当通过选择机电协同系数约为150以及光功率为1毫瓦来平衡时，推断出这些贡献中的每一项均为60皮伏每平方根赫兹。薄膜的噪声温度为300开尔文除以协同系数。对于所观测到的最高协同系数6800，这导致预计噪声温度为40毫开尔文以及灵敏度极限为5皮伏每平方根赫兹。我们对经典电子信号进行全光、超低噪声检测的方法为低频量子信号到光域的相干上转换奠定了基础（8 - 11）
Low-loss transmission and sensitive recovery of weak radio-frequency and microwave signals is a ubiquitous challenge, crucial in radio astronomy, medical imaging, navigation, and classical and quantum communication. Efficient up-conversion of radio-frequency signals to an optical carrier would enable their transmission through optical fibres instead of through copper wires, drastically reducing losses, and would give access to the set of established quantum optical techniques that are routinely used in quantum-limited signal detection. Research in cavity optomechanics(1,2) has shown that nanomechanical oscillators can couple strongly to either microwave(3-5) or optical fields(6,7). Here we demonstrate a room-temperature optoelectromechanical transducer with both these functionalities, following a recent proposal(8) using a high-quality nanomembrane. A voltage bias of less than 10 V is sufficient to induce strong coupling(4,6,7) between the voltage fluctuations in a radio-frequency resonance circuit and the membrane's displacement, which is simultaneously coupled to light reflected off its surface. The radio-frequency signals are detected as an optical phase shift with quantum-limited sensitivity. The corresponding half-wave voltage is in the microvolt range, orders of magnitude less than that of standard optical modulators. The noise of the transducer-beyond the measured 800 pV Hz(-1/2) Johnson noise of the resonant circuit-consists of the quantum noise of light and thermal fluctuations of the membrane, dominating the noise floor in potential applications in radio astronomy and nuclear magnetic imaging. Each of these contributions is inferred to be 60 pV Hz(-1/2) when balanced by choosing an electromechanical cooperativity of similar to 150 with an optical power of 1 mW. The noise temperature of the membrane is 300 K divided by the cooperativity. For the highest observed cooperativity of 6,800, this leads to a projected noise temperature of 40 mK and a sensitivity limit of 5 pV Hz(-1/2). Our approach to all-optical, ultralow-noise detection of classical electronic signals sets the stage for coherent up-conversion of low-frequency quantum signals to the optical domain(8-11).