Abstract
In a canonical optomechanical system, mechanical vibrations are dynamically encoded on an optical probe field which reciprocally exerts a backaction force. Due to the weak single photon coupling strength achieved with macroscopic oscillators, most of existing experiments were conducted with large photon numbers to achieve sizeable effects, thereby causing a dilution of the original optomechanical non-linearity. Here, we investigate the optomechanical interaction of an ultrasensitive suspended nanowire inserted in a fiber-based microcavity mode. This implementation allows to enter far into the hitherto unexplored ultrastrong optomechanical coupling regime, where one single intracavity photon can displace the oscillator by more than its zero point fluctuations. To fully characterize our system, we implement nanowire-based scanning probe measurements to map the vectorial optomechanical coupling strength, but also to reveal the intracavity optomechanical force field experienced by the nanowire. This work establishes that the single photon cavity optomechanics regime is within experimental reach.
Highlights
The field of optomechanics has gone through many impressive developments over the last decades [1]
We show here that the large force sensitivity of the nanowire, combined with the large coupling strength achieved thanks to the small-modevolume microcavity mode allows us to detect optical forces corresponding to modulations of the mean intracavity photon number smaller than unity
We have realized a dual characterization of the optomechanical interaction, via nanowire-mediated scanning probe measurements of the intracavity field and mapping of the intracavity optomechanical force field using intracavityphoton-number modulations smaller than unity
Summary
The field of optomechanics has gone through many impressive developments over the last decades [1]. We employ subwavelength-sized nanowires, which produce significant photon scattering out of the cavity mode, so we operate in the single-photon adiabatic regime ðΩm ≪ g0 ≪ κÞ, where the cavity field instantaneously follows mechanically induced perturbations This regime opens perspectives for exploring the optomechanical interaction at the single mean intracavity photon level, which should be within experimental reach at cryogenic temperatures. It represents an interesting resource for quantum optics since the optomechanical interaction to the nanowire is sufficient to generate nonclassical states of light down to very small mean photon numbers and in a broad frequency range, not restricted to the vicinity of the mechanical resonance [5,20]. We discuss the perspectives of this approach, or which allowing us to largely enter the emerging field of the single-photon and adiabatic regimes of cavity optomechanics and introduce some of the phenomena that would become accessible when working with cryogenically cooled nanowires
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