We describe how photon-phonon interactions can be used to achieve large optical non-reciprocity and ideal optical isolation with integrated photonics. Our experiments rely on breaking time-reversal symmetry within dielectrics (e.g. silica, aluminum nitride, lithium niobate) using the Brillouin scattering nonlinearity. We show how the breaking of time-reversal symmetry can also be used to suppress disorder-induced backscattering in optical resonators.
Optical resonators have enabled the label-free measurement of nanoparticles suspended in liquids, down to the resolution of individual viruses and large molecules, but are only able to quantify optical properties (refractive index, scattering, fluorescence). Additionally, these sensors are fundamentally limited by the random diffusion of particles to the sensing region, and thus only measure a tiny fraction of the analyte. We have developed a microfluidic optomechanical resonator capable of sensing freely flowing nanoparticles using the action of phonons that are coupled to light. The phonon mode of the system casts a nearly perfect net for measuring density, viscoelasticity, and compressibility of the particles that flow through, without being limited by random diffusion. Information on the mechanical properties of the particles is encoded in the light scattered from the thermal fluctuations of the phonon mode. We have also developed a new electro-opto-mechanical method for improving the sensing speed achievable with this technique. We demonstrate real-time particle transit measurements as fast as 400 microseconds, without any post-processing. We discuss how this novel technique can be used for ultra-high throughput analysis of mechanical properties of biological particles in liquids, enabling a new form of flow cytometry.
(invited by Prof. Giuseppe Leo)
Microscale resonators that simultaneously exhibit high-Q optical and mechanical resonances are routinely used to study the coupling between light and vibration. We have learned recently that Brillouin scattering (traveling-wave light-sound interactions) within these resonators can enable nonreciprocal optical transmission through a waveguide, which can be reconfigured optically and on demand. In this talk, we describe the basic theory and experimental demonstrations of Brillouin Optomechanics, and describe how it allows the breaking of time-reversal symmetry by means of traveling phonon modes. We experimentally demonstrate ultra-low loss optical isolation using a simple resonator system. Our results demonstrate that chip-scale optical isolation is much more accessible than previously thought.
Resonant optical sensors have enabled the label-free measurement of nanoparticles suspended in liquids, down to the resolution of individual viruses and large molecules, but are only able to quantify optical properties (refractive index, scattering, fluorescence). Additionally, these sensors are fundamentally limited by the random diffusion of particles to the sensing region, and thus only quantify a tiny fraction of the analyte. We have developed a microfluidic optomechanical resonator capable of sensing flowing nanoparticles using the action of phonons that are coupled to light. The phonon mode of the system casts a nearly perfect net for measuring density, viscoelasticity, and compressibility of the particles that flow through, without being limited by random diffusion. Information on the particle mechanical properties is encoded in the light scattered from the thermal fluctuations of the phonon mode, and measurements at a timescale of below 20 milliseconds have been demonstrated previously. In this work, we develop a new experimental method for improving the signal-to-noise ratio (SNR) and sensing speed achievable with this technique, by implementing electro-opto-mechanical transduction. We demonstrate real-time particle transit measurements as fast as 400 microseconds, a factor of 50x improvement in speed, without any post-processing. We discuss how this novel technique can be used for ultra-high throughput analysis of mechanical properties of biological particles in liquids, enabling a new form of flow cytometry.
Microscale resonators that simultaneously exhibit high-Q optical and mechanical resonances are routinely used to study the coupling between light and vibration. We have learned recently that Brillouin scattering (traveling-wave light-sound interactions) within simple dielectric whispering-gallery resonators can enable nonreciprocal optical transmission through a waveguide, which can be reconfigured optically and on demand. In this talk, we describe the basic theory and experimental demonstrations of Brillouin Optomechanics, and describe how it allows the breaking of time-reversal symmetry by means of traveling phonon modes. We experimentally demonstrate ultra-low loss optical isolation using a simple resonator system. Our results demonstrate that chip-scale optical isolation is much more accessible than previously thought.
(invited by Prof. Xudong Fan)
Laser cooling of solids can be achieved through various photon up-conversion processes including anti-Stokes photoluminescence
and anti-Stokes light scattering. While it has been shown that cooling using photoluminescence-based
methods can achieve efficiency comparable to that of thermoelectric cooling, the reliance on specific
transitions of the rare-earth dopants limits material choice. Light scattering, on the other hand, occurs in all
materials, and has the potential to enable cooling in most materials. We show that by engineering the photonic
density of states of a material, one can suppress the Stokes process, and enhance the anti-Stokes radiation.
We employ the well-known diamond-structured photonic crystal patterned in crystalline silicon to demonstrate
theoretically that when operating within a high transparency regime, the net energy removal rate from phonon
annihilation can overcome the optical absorption. The engineered photonic density of states can thus enable
simultaneous cooling of all Raman-active phonon modes and the net cooling of the solid.
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