RESUMO
We present the design of an optomechanical device that allows sensitive transduction of the orbital angular momentum of light. An optically induced twist imparted on the device is detected using a photonic crystal cavity optomechanical system. This device allows the measurement of the orbital angular momentum of light when photons are absorbed by the mechanical element or the detection of the presence of photons when they are scattered into new orbital angular momentum states by a sub-wavelength grating patterned on the device. Such a system allows the detection of optical pulses with an l = 1 orbital angular momentum field that have an average photon number of 3.9 × 103 at a 5 MHz repetition rate, assuming that detector noise is not limiting measurement sensitivity. This scheme can be extended to higher order orbital angular momentum states.
RESUMO
Hexagonal boron nitride (hBN) is an emerging layered material that plays a key role in a variety of two-dimensional devices, and has potential applications in nanophotonics and nanomechanics. Here, we demonstrate the first cavity optomechanical system incorporating hBN. Nanomechanical resonators consisting of hBN beams with average dimensions of 12 µm × 1.2 µm × 28 nm and minimum predicted thickness of 8 nm were fabricated using electron beam induced etching and positioned in the optical near-field of silicon microdisk cavities. Of the multiple devices studied here a maximum 0.16 pm/[Formula: see text] sensitivity to the hBN nanobeam motion is demonstrated, allowing observation of thermally driven mechanical resonances with frequencies between 1 and 23 MHz, and largest mechanical quality factor of 1100 for a 23 MHz mode, at room temperature in high vacuum. In addition, the role of air damping is studied via pressure dependent measurements. Our results constitute an important step toward realizing integrated optomechanical circuits employing hBN.