Mani Hossein-Zadeh

High-Q microphotonic electro-optic modulator

Abstract A microphotonic mm-wave modulator using simultaneous RF and optical resonance in an electro-optic medium is presented. Theory and simulation of modulator operation is discussed, and experimental results demonstrating modulation using simultaneous resonance in the mm-wave range are reported.

Fiber-taper coupling to Whispering-Gallery modes of fluidic resonators embedded in a liquid medium.

We demonstrate efficient coupling to the optical Whispering- Gallery (WG) modes of a fluidic resonator consisting of a droplet embedded in a liquid medium. Unlike previous experiments the droplet is not levitated in an optical or electrostatic trap and free space coupling is replaced by phase-matched, waveguide coupling using a fiber-taper. We have observed critical coupling to fundamental WG modes of a 600 mum diameter water droplet at 980 nm. The experimental challenges towards making, stabilizing and coupling to the droplet resonators are addressed in this paper.

An Optomechanical Oscillator on a Silicon Chip

The recent observation on radiation-pressure-driven self-sustained oscillation in high- Q optical microresonators has created new possibilities for development of photonic devices that benefit from unique functionalities offered by these ¿optomechanical oscillators¿ (OMOs). Here, we review the physics, fundamental characteristics, and potential applications of OMOs using the silica microtoroidal OMO as an example.

Photonic RF Down-Converter Based on Optomechanical Oscillation

We demonstrate all-optical radio-frequency (RF) down-conversion in a silica microtoroid optomechanical (OM) oscillator. Preliminary results show that the OM oscillator can simultaneously serve as mixer and local oscillator in a photonic homodyne RF-receiver architecture.

Free ultra-high-Q microtoroid: a tool for designing photonic devices

We describe techniques that enable fabrication of a new class of photonic devices based on free UH-Q microresonators. Preliminary results show that free silica microtoroids with Qs above 30 million can be fabricated and transferred to different platforms for integration with a variety of photonic devices.

Sub-pg mass sensing and measurement with an optomechanical oscillator

Mass sensing based on mechanical oscillation frequency shift in micro/nano scale mechanical oscillators is a well-known and widely used technique. Piezo-electric, electronic excitation/detection and free-space optical detection are the most common techniques used for monitoring the minute frequency shifts induced by added mass. The advent of optomechanical oscillator (OMO), enabled by strong interaction between circulating optical power and mechanical deformation in high quality factor optical microresonators, has created new possibilities for excitation and interrogation of micro/nanomechanical resonators. In particular, radiation pressure driven optomechanical oscillators (OMOs) are excellent candidates for mass detection/measurement due to their simplicity, sensitivity and all-optical operation. In an OMO, a high quality factor optical mode simultaneously serves as an efficient actuator and a sensitive probe for precise monitoring of the mechanical eigen-frequencies of the cavity structure. Here, we show the narrow linewidth of optomechanical oscillation combined with harmonic optical modulation generated by nonlinear optical transfer function, can result in sub-pg mass sensitivity in large silica microtoroid OMOs. Moreover by carefully studying the impact of mechanical mode selection, device dimensions, mass position and noise mechanisms we explore the performance limits of OMO both as a mass detector and a high resolution mass measurement system. Our analysis shows that femtogram level resolution is within reach even with relatively large OMOs.

14.6-GHz LiNbO/sub 3/ microdisk photonic self-homodyne RF receiver

Nonlinear optical modulation combined with simultaneous photonic and RF resonance in an LiNbO/sub 3/ microdisk modulator is used to create a self-homodyne photonic RF receiver. Carrier and sidebands are mixed in the optical domain, and the modulated optical signal is detected using a photodetector. The photodetector has a bandwidth matched to the baseband signal. It filters out the high-frequency components and generates the baseband photocurrent. Receiver operation is demonstrated by demodulating up to 100-Mb/s digital data from a 14.6-GHz carrier frequency without any high-speed electronic components. A bit error rate of 10/sup -9/ is measured for 10-Mb/s downconverted digital data at -15-dBm received RF power. Preliminary results of employing this photonic RF receiver in a short-distance Ku-band wireless link demonstrate the potential of using high-quality optical microresonators in RF receiver applications.

Thermo-optomechanical oscillator for sensing applications

We demonstrate a thermo-optomechanical oscillator based on high-Q optical resonance and study its application in sensing. The unique bifrequency oscillation that carries the signature of local thermo-optic and global thermo-mechanical effects is analyzed and characterized.

Observation of injection locking in an optomechanical rf oscillator

We demonstrate injection locking of a radiation pressure driven optomechanical oscillator through external optical modulation of the optical pump power near optomechanical oscillation frequency.

Observation of optical spring effect in a microtoroidal optomechanical resonator

We present experimental evidence of the optical spring effect in a silica microtoroid resonator. The variation of the measured mechanical resonant frequency as a function of optical power, optical coupling, and optical detuning is in very good agreement with a model for radiation-pressure-induced rigidity in a silica microtoroid.