arXiv subjects

Hamidreza Kaviani

Publications and source records attributed to Hamidreza Kaviani.

9 recordsLinked to original sources

arXiv2022

High frequency torsional motion transduction using optomechanical coupled oscillators

Using light to measure an object's motion is central to operating mechanical sensors that probe forces and fields. Cavity optomechanical systems embed mechanical resonators inside optical resonators. This enhances the sensitivity of optomechanical measurements, but only if the mechanical resonator does not spoil the properties of the optical cavity. For example, cavity optomechanical detection of resonators made from optically absorbing materials, or whose geometry does not possess suitable spatial symmetry, is challenging. Here we demonstrate a system that overcomes challenges in measuring high-frequency twisting motion of a nanodisk by converting them to vibrations of a photonic crystal cavity. Optomechanical readout of the cavity then enables measurement of the nanodisk's torsional resonances with sensitivity $5.1\times 10^{-21}-1.2\times 10^{-19}\,\text{Nm}/\sqrt{\text{Hz}}$ for a mechanical frequency range of 5--800 MHz. The nanodisk can be outfitted with magnetic nanostructures or metasurfaces without affecting the optical properties of the cavity, making the system suitable for torque magnetometry and structured light sensing.

physics.optics↗

arXiv2019

Optomechanical Detection of Light with Orbital Angular Momentum

We present an optomechanical device designed to allow optical transduction of orbital angular momentum of light. An optically induced twist imparted on the device by light is detected using an integrated cavity optomechanical system based on a nanobeam slot-mode photonic crystal cavity. This device could allow measurement of the orbital angular momentum of light when photons are absorbed by the mechanical element, or detection of the presence of photons when they are scattered into new orbital angular momentum states by a sub-wavelength grating patterned on the device. Such a system allows detection of a $l = 1$ orbital angular momentum field with an average power of $3.9\times10^3$ photons modulated at the mechanical resonance frequency of the device and can be extended to higher order orbital angular momentum states.

quant-ph↗

arXiv2019

Air mode silicon nitride photonic crystals and their application to nonlinear quantum optomechanical sensing

Nanoscale photonic crystal cavity optomechanical devices enable detection of nanomechanical phenomena with a sensitivity sufficient to observe quantum effects. Here we present the design of a one-dimensional air-mode photonic crystal cavity patterned in a silicon nitride nanobeam, and show that it forms the basis for cavity optomechanical split-beam and paddle nanocavity devices useful for force detection and nonlinear quantum sensing. The air-mode of this device is advantageous for optomechanical coupling, while also having ultrahigh optical quality factor $Q_o\sim 10^6$ despite its proximity to the light-line and the relatively low refractive index of silicon nitride. Paddle nanocavities realized from this device have a quadratic coupling coefficient $g^{(2)}/2π$~=~10~MHz/nm$^{2}$, and their performance within the context of quantum optomechanics experiments is analyzed.

physics.optics↗

arXiv2019

Towards a Room-Temperature Spin-Photon Interface based on Nitrogen-Vacancy centers and Optomechanics

The implementation of quantum networks involving quantum memories and photonic channels without the need for cryogenics would be a major technological breakthrough. Nitrogen-vacancy centers have excellent spin properties even at room temperature, but phonon-induced broadening makes it challenging to interface these spins with photons at non-cryogenic temperatures. Inspired by recent progress in achieving ultra-high mechanical quality factors, we propose that this challenge can be overcome by spin-opto-mechanical transduction. We quantify the coherence of the interface by calculating the indistinguishability of the emitted photons and describe promising paths towards experimental implementation.

quant-ph↗

arXiv2015

Design and experimental demonstration of optomechanical paddle nanocavities

We present the design, fabrication and initial characterization of a paddle nanocavity consisting of a suspended sub-picogram nanomechanical resonator optomechanically coupled to a photonic crystal nanocavity. The optical and mechanical properties of the paddle nanocavity can be systematically designed and optimized, and key characteristics including mechanical frequency easily tailored. Measurements under ambient conditions of a silicon paddle nanocavity demonstrate an optical mode with quality factor $Q_o$ ~ 6000 near 1550 nm, and optomechanical coupling to several mechanical resonances with frequencies $ω_m/2π$ ~ 12-64 MHz, effective masses $m_\text{eff}$ ~ 350-650 fg, and mechanical quality factors $Q_m$ ~ 44-327. Paddle nanocavities are promising for optomechanical sensing and nonlinear optomechanics experiments.

physics.optics↗

arXiv2015

Single crystal diamond nanobeam waveguide optomechanics

Optomechanical devices sensitively transduce and actuate motion of nanomechanical structures using light. Single--crystal diamond promises to improve the performance of optomechanical devices, while also providing opportunities to interface nanomechanics with diamond color center spins and related quantum technologies. Here we demonstrate dissipative waveguide--optomechanical coupling exceeding 35 GHz/nm to diamond nanobeams supporting both optical waveguide modes and mechanical resonances, and use this optomechanical coupling to measure nanobeam displacement with a sensitivity of $9.5$ fm/$\sqrt{\text{Hz}}$ and optical bandwidth $>150$nm. The nanobeams are fabricated from bulk optical grade single--crystal diamond using a scalable undercut etching process, and support mechanical resonances with quality factor $2.5 \times 10^5$ at room temperature, and $7.2 \times 10^5$ in cryogenic conditions (5K). Mechanical self--oscillations, resulting from interplay between photothermal and optomechanical effects, are observed with amplitude exceeding 200 nm for sub-$μ$W absorbed optical power, demonstrating the potential for optomechanical excitation and manipulation of diamond nanomechanical structures.

physics.optics↗

arXiv2015

Nonlinear optomechanical paddle nanocavities

Nonlinear optomechanical coupling is the basis for many potential future experiments in quantum optomechanics (e.g., quantum non-demolition measurements, preparation of non-classical states), which to date have been difficult to realize due to small non-linearity in typical optomechanical devices. Here we introduce an optomechanical system combining strong nonlinear optomechanical coupling, low mass and large optical mode spacing. This nanoscale "paddle nanocavity" supports mechanical resonances with hundreds of fg mass which couple nonlinearly to optical modes with a quadratic optomechanical coupling coefficient $g^{(2)} > 2π\times400$ MHz/nm$^2$, and a two phonon to single photon optomechanical coupling rate $Δω_0 > 2π\times 16$ Hz. This coupling relies on strong phonon-photon interactions in a structure whose optical mode spectrum is highly non--degenerate. Nonlinear optomechanical readout of thermally driven motion in these devices should be observable for T $> 50 $ mK, and measurement of phonon shot noise is achievable. This shows that strong nonlinear effects can be realized without relying on coupling between nearly degenerate optical modes, thus avoiding parasitic linear coupling present in two mode systems.

quant-ph↗

arXiv2014

Strong micro-macro entanglement from a weak cross-Kerr nonlinearity

We study the entanglement generated by a weak cross-Kerr nonlinearity between two initial coherent states, one of which has an amplitude close to the single-photon level, while the other one is macroscopic. We show that strong micro-macro entanglement is possible for weak phase shifts by choosing the amplitude of the macroscopic beam sufficiently large. We analyze the effects of loss and discuss possible experimental demonstrations of the micro-macro entanglement based on homodyne tomography and on a new entanglement witness.

quant-ph↗

arXiv2013

Quantum Storage and Retrieval of Light by Sweeping the Atomic Frequency

We propose a quantum memory protocol based on dynamically changing the resonance frequency of an ensemble of two-level atoms. By sweeping the atomic frequency in an adiabatic fashion, photons are reversibly transferred into atomic coherences. We present a polaritonic description for this type of storage, which shares some similarities with Electromagnetically Induced Transparency (EIT) based quantum memories. On the other hand the proposed memory is also linked to the Gradient Echo Memory (GEM) due to the effective spatial gradient that pulses experience in the medium. We discuss a possible implementation of the protocol in hollow-core photonic crystal fibers.

quant-ph↗