Multimode Optomechanical Weighting of a Single Nanoparticle

Abstract

We demonstrate multimode optomechanical sensing of individual nanoparticles with a radius between 75 and 150 nm. A semiconductor optomechanical disk resonator is optically driven and detected under ambient conditions, as nebulized nanoparticles land on it. Multiple mechanical and optical resonant signals of the disk are tracked simultaneously, providing access to several pieces of physical information about the landing analyte in real time. Thanks to a fast camera registering the time and position of landing, these signals can be employed to weight each nanoparticle with precision. Sources of error and deviation are discussed and modeled, indicating a path to evaluate the elasticity of the nanoparticles on top of their mere mass. The device is optimized for the future investigation of biological particles in the high megadalton range, such as large viruses.

Free-access optomechanical liquid probes using a twin-microbottle resonator

“…The signal-to-noise ratios (i.e., the ratios between the peak top level and the noise floor level) are 3.2 and 1.7, which result in displacement sensitivity (i.e., the minimum detectable displacement) of 4.5 × 10 −18 normalm/Hz in our optomechanical setup and temperature condition [25°C for both the room (air) and water]. This sensitivity is on a level similar to that in microdisks ( 7 , 10 , 12 ) and microcapillaries ( 5 , 6 , 8 ) and will be further improved by constructing a balanced homodyne interferometer ( 35 ). Combining the efficient transduction between two mechanical modes and the strong optomechanical coupling enables us to detect the thermal motion when the TMBR is immersed in liquid.…”

“…Recently, two innovative optomechanical approaches have been demonstrated to maintain the optical sensitivity ( 5 , 8 , 10 , 12 ). The first approach is based on a glass microcapillary.…”

“…When the optical WGMs are almost completely confined in the capillary wall and isolated from the liquid flowing inside the channel, the high optical Q is conserved, enabling an optical detection of the thermal motion and an optical drive of the mechanical RBMs ( 14 , 15 ). The second approach is based on a droplet-covered GaAs microdisk ( 7 , 10 , 12 ), which forms the optical WGMs and the mechanical RBMs. Because the refractive index of GaAs (3.3 at telecom wavelengths) is higher than that of typical viscous media, the light is confined in the optical cavity, leading to a high optical Q in liquid (>10 5 ).…”

“…Moreover, if some molecules or particles adhere to a mechanical resonator, then the mechanical resonance changes. Thus, the optomechanical probe also allows chemical and biological sensing in liquid (8)(9)(10)(11)(12). However, the sensitivity in liquid is orders of magnitude lower than that in air, because the optical Q deteriorates because of light loss to the surrounding medium whose refractive index is higher than that of the optical cavity (11,13), in addition to the damped small amplitude of the mechanical modes.…”

Optomechanical measurement of single nanodroplet evaporation with millisecond time-resolution

“… 23 . The co-existence of optical and mechanical modes in the structure provides a dual detection approach for an analyte that would land on the disk 24 . In our experiments, this landing analyte is additionally imaged in real-time thanks to a ×100 magnification microscope objective coupled to a fast camera with 1 kHz frame acquisition rate.…”