Current Research Topics

Silicon Photonics  We view silicon photonics as a versatile platform on which optical instruments used to be table-sized can be miniaturized and integrated on a chip. Optical interferometers, optical cavities and spectrometers can all be carved into a silicon chip. We use these chips to investigate various optical phenomena, to characterize optical properties of novel materials and to achieve high-speed signal processing.

Nano-Opto-Mechanics (NOMS) Light-matter interaction is inevitably accompanied with mechanical effects or optical forces. This is simply because each photon carries a quantum of momentum. When light is absorbed, reflected, deflected, or diffracted by the material under illumination, transfer of momentum occurs and a corresponding force is generated. We aim to generate, enhance and control optical forces in advanced nanophotonic systems with a focus on developing brand new device functionalities and demonstrating novel optomechanical effects. On a highly integrated silicon photonics platform, novel photonic devices incorporating photonic crystal cavities and plasmonic structures will be developed to enhance optical forces. New optical functions will be realized by utilizing mechanical displacement induced by optical forces. The research will lead to a new class of photonic devices based on optomechanical principles for a wide range of applications including RF/microwave photonics, tunable photonics, MEMS and NEMS transduction.

Funding: AFOSR (YIP program)

Graphene Optoelectronics Graphene and other novel 2D materials have remarkable optoelectronic properties that can be optimally utilized through integration in planar photonic circuits. The research will be the first steps toward incorporating 2D materials in large scale integrated (LSI), silicon-based photonic circuits and systems for optical communication and computation.

Flexible photonics Flexible microelectronics has shown tremendous promise in a broad spectrum of applications, especially those which cannot be addressed by the conventional microelectronic technology based on rigid materials and constructions. The similar principles can be applied to photonic devices. We are working on flexible silicon photonics based on plastic substrates for tunable photonic systems, flexible optical sensors and biophotonic probes.

Funding: NSF (ECCS-EPMD)

Spin-optical interconnection In all-spin based computation systems, spin information needs to be transmitted over distance longer than the spin diffusion length in channel materials. Such interconnects are indispensable for an all-spin computing architecture to connect multiple computing modules and connect processing units with second level memory blocks. For this purpose we are developing spin-optical links, which consist of spin-optical transmitter, optical-spin receiver and optical waveguides, to achieve high-speed, low-power interconnects for future all-spin computers.

Funding: C-SPIN (supported by DARPA and SRC)

Acoustic Photonics Acousto-optics exploits the interactions between lightwaves and sound waves. Actively generated acoustic wave in an optical material acts as a traveling phase grating and can deflect incident light wave through Bragg diffraction and shift its frequency through Doppler effect. In this project, we build integrated photonic and acoustic devices in which actively generated acoustic waves strongly interact with confined and guided optical waves. We will investigate various types nonlinear optical phenomena induced by the strong interaction between photons and phonons, both confined in the nanoscale.

Funding: NSF (ECCS-EPMD)

Mid-Infrared Photonics Recently, the mid-infrared spectral range has attracted tremendous scientific and technological interest, spurred by the development of quantum cascade lasers (QCLs) and fiber lasers. We are developing silicon photonic devices working in the mid-IR range for sensing applications.

Funding: NSF (CMMI-SSS)

Optogenetic neural probe We will develop the next generation opto-electrical neural probes for multimodal interrogation of brain activity. The work will be a collaboration with Prof.Sotiris Masmanidis in the Department of Neurobiology at UCLA. The new probe will integrate large arrays of nanophotonic wave-guides and microelectrodes to achieve active control and readout of neural activities. On these probes, the waveguides will emit light pulses to selectively activate or silence a local, optically excitable neuronal population, while the microelectrodes will record the network activity resulting from this stimulation. The research aims to provide neuroscientists with powerful new tool to decipher the neural-circuitry of behavior, leveraging recent advances in optogenetic techniques.

Funding: NSF (CBET-biophotonics)

Nano-electro-mechanics (NEMS) We are interested in nanoscale mechanical devices and systems. Specifically, we study noise processes, feedback control, synchronization, and nonlinear phenomena in NEMS and the use of NEMS for various sensing applications.

Chemical and biochemical Sensors