arXiv subjects

Siddharth Tallur

Publications and source records attributed to Siddharth Tallur.

27 records · Page 2Linked to original sources

arXiv2019

Synchronization of Chaotic Oscillators With Partial Linear Feedback Control

We present a methodology for synchronization of chaotic oscillators with linear feedback control. The proposed method is based on analyzing the chaotic oscillator as a multi-mode linear system and deriving sufficient conditions for asymptotic stability. The oscillators are synchronized in a master-slave configuration, wherein a subset of the state variables for implementing the feedback control, enabling applications in cryptography for message encryption using the unused chaotic state variables. Controller stability is ensured through conventional root-locus technique for designing appropriate loop gain. We validate the methodology presented here with numerical simulations and experimental results obtained using an operational amplifier (op-amp) based electronic chaotic oscillator circuit.

nlin.CD↗

arXiv2013

Rayleigh scattering boosted multi-GHz displacement sensitivity in whispering gallery opto-mechanical resonators

Finite photon lifetimes for light fields in an opto-mechanical cavity impose a bandwidth limit on displacement sensing at mechanical resonance frequencies beyond the loaded cavity photon decay rate. Opto-mechanical modulation efficiency can be enhanced via multi-GHz transduction techniques such as piezo-opto-mechanics at the cost of on-chip integration. In this paper, we present a novel high bandwidth displacement sense scheme employing Rayleigh scattering in photonic resonators. Using this technique in conjunction with on-chip electrostatic drive in silicon enables efficient modulation at frequencies up to 9.1GHz. Being independent of the drive mechanism, this scheme could readily be extended to piezo-opto-mechanical and all optical transduced systems.

physics.optics↗

arXiv2013

A silicon electromechanical photodetector

Opto-mechanical systems have enabled wide-band optical frequency conversion and multi-channel all-optical radio frequency amplification. Realization of an on-chip silicon communication platform is limited by photodetectors needed to convert optical information to electrical signals for further signal processing. In this paper we present a coupled silicon micro-resonator, which converts near-IR optical intensity modulation at 174.2MHz and 1.198GHz into motional electrical current. This device emulates a photodetector which detects intensity modulation of continuous wave laser light in the full-width-at-half-maximum bandwidth of the mechanical resonance. The resonant principle of operation eliminates dark current challenges associated with convetional photodetectors.

physics.optics↗

arXiv2013

Comparison of f-Q scaling in wineglass and radial modes in ring resonators

Low phase noise MEMS oscillators necessitate resonators with high f-Q. Resonators achieving high f-Q (mechanical frequency-quality factor product) close to the thermo-elastic damping (TED) limit have been demonstrated at expense of feed-through. Here we present a study comparing frequency scaling of quality factors of wineglass and radial modes in a ring resonator using an opto-mechanical two port transmission measurement. Higher harmonics of the wineglass mode show an increasing trend in the f-Q product, as compared to a saturation of f-Q for radial modes. The measured f-Q of 5.11e13Hz at 9.82GHz in air at room temperature for a wineglass mode is close to the highest measured values in silicon resonators.

physics.optics↗

arXiv2012

Electro-mechanically induced GHz rate optical frequency modulation in silicon

We present a monolithic silicon acousto-optic frequency modulator (AOFM) operating at 1.09GHz. Direct spectroscopy of the modulated laser power shows asymmetric sidebands which indicate coincident amplitude modulation and frequency modulation. Employing mechanical levers to enhance displacement of the optical resonator resulted in greater than 67X improvement in the opto-mechanical frequency modulation factor over earlier reported numbers for silicon nanobeams.

physics.optics↗

arXiv2012

Acousto-optic frequency modulator

Frequency modulation of a continuous wave laser source enables generation of photons at multiple frequencies from a single pump laser. Such multiple closely spaced laser lines are important for high data rate QAM in dense-WDM networks. In this paper we present a monolithic silicon acousto-optic frequency modulator (AOFM) operating at 1.09GHz. We demonstrate frequency modulation of a 1564nm wavelength pump laser, resulting in generation of sideband laser lines spaced by 0.009nm.

physics.optics↗

arXiv2012

Simultaneous radiation pressure induced heating and cooling of an opto-mechanical resonator

Cavity opto-mechanics enabled radiation-pressure coupling between optical and mechanical modes of a micro-mechanical resonator gives rise to dynamical backaction, enabling amplification and cooling of mechanical motion. Due to a combination of large mechanical oscillations and necessary saturation of amplification, the noise floor of the opto-mechanical resonator increases, rendering it ineffective at transducing small signals, and thereby cooling another mechanical resonance of the system. Here we show amplification of one mechanical resonance in a micro-mechanical ring resonator while simultaneously cooling another mechanical resonance by exploiting two closely spaced optical whispering gallery mode cavity resonances.

physics.optics↗

arXiv2011

A Monolithic Radiation-Pressure Driven, Low Phase Noise Silicon Nitride Opto-Mechanical Oscillator

Cavity opto-mechanics enabled radiation pressure (RP) driven oscillators shown in the past offer an all optical Radio Frequency (RF) source without the need for external electrical feedback. However these oscillators require external tapered fiber or prism coupling and non-standard fabrication processes. In this work, we present a CMOS compatible fabrication process to design high optical quality factor opto-mechanical resonators in silicon nitride. The ring resonators designed in this process demonstrate low phase noise RP driven oscillations. Using integrated grating couplers and waveguide to couple light to the micro-resonator eliminates 1/f^3 and other higher order phase noise slopes at close-to-carrier frequencies present in previous demonstrations. We present an RP driven OMO operating at 41.97MHz with a signal power of -11dBm and phase noise of -85dBc/Hz at 1kHz offset with only 1/f^2 noise down to 10Hz offset from carrier.

physics.optics↗

arXiv2010

Phase Noise Modeling of Opto-Mechanical Oscillators

We build upon and derive a precise far from carrier phase noise model for radiation pressure driven opto-mechanical oscillators and show that calculations based on our model accurately match published phase noise data for such oscillators. Furthermore, we derive insights based on the equations presented and calculate phase noise for an array of coupled disk resonators, showing that it is possible to achieve phase noise as low as -80 dBc/Hz at 1 kHz offset for a 54 MHz opto-mechanical oscillator.

physics.optics↗