arXiv subjects

Alkim Bozkurt

Publications and source records attributed to Alkim Bozkurt.

4 recordsLinked to original sources

arXiv2026

A micromechanical frequency reference with parts-per-trillion holdover stability

Microelectromechanical (MEMS) resonators are widely used in timekeeping applications, and recent advances in fabrication, materials, and encapsulation technology have advanced their potential as high stability frequency references. However, for holdover applications that require the highest levels of long-term frequency stability, compact vapor atomic clocks remain dominant. In this work, we demonstrate a 268 MHz MEMS clock that achieves record fractional frequency stability of ~8 parts-per-trillion at an averaging time of 8 hours, competitive with chip-scale atomic clocks. We achieved this using a single-crystal silicon electrostatic resonator that has no currently known intrinsic drift mechanism and is protected from the environment with a wafer-level encapsulation. We specifically identify gain variations in the sustaining electronics as the dominant limitation in conventional phase-locked oscillator architectures -- originating from temperature sensitivity and drifts in the electronic components -- and overcome this by implementing a frequency-locked loop architecture based on dual-frequency resonance tracking (DFRT). This novel approach removes the specific gain of the supporting electronics as a frequency determining variable in the oscillator. When combined with dual-mode tracking and ratiometric temperature stabilization of the resonator, this approach enables a dramatic enhancement to long-term frequency stability and establishes gain-insensitive DFRT locking as a general paradigm for high-stability MEMS clocks.

physics.app-ph↗

arXiv2022

Electro-optic transduction in silicon via GHz-frequency nanomechanics

Interfacing electronics with optical fiber networks is key to the long-distance transfer of classical and quantum information. Piezo-optomechanical transducers enable such interfaces by using GHz-frequency acoustic vibrations as mediators for converting microwave photons to optical photons via the combination of optomechanical and piezoelectric interactions. However, despite successful demonstrations, efficient piezo-optomechanical transduction remains out of reach due to the challenges associated with hybrid material integration and increased loss from piezoelectric materials when operating in the quantum regime. Here, we demonstrate an alternative approach in which we actuate 5-GHz phonons in a conventional silicon-on-insulator platform. In our experiment, microwave photons resonantly drive a phononic crystal oscillator via the electrostatic force realized in a charge-biased narrow-gap capacitor. The mechanical vibrations are subsequently transferred via a phonon waveguide to an optomechanical cavity, where they transform into optical photons in the sideband of a pump laser field. Operating at room temperature and atmospheric pressure, we measure a microwave-to-optical photon conversion efficiency of $1.8 \times 10^{-7}$ in a 3.3 MHz bandwidth, and demonstrate efficient phase modulation with a half-wave voltage of $V_π= 750 $ mV. Our results mark a stepping stone towards quantum transduction with integrated devices made from crystalline silicon, which promise efficient high-bandwidth operation, and integration with superconducting qubits. Additionally, the lack of need for piezoelectricity or other intrinsic nonlinearities makes our approach adaptable to a wide range of materials for potential applications beyond quantum technologies.

physics.optics↗

arXiv2022

A quantum electromechanical interface for long-lived phonons

Controlling long-lived mechanical oscillators in the quantum regime holds promises for quantum information processing. Here, we present an electromechanical system capable of operating in the GHz-frequency band in a silicon-on-insulator platform. Relying on a novel driving scheme based on an electrostatic field and high-impedance microwave cavities based on TiN superinductors, we are able to demonstrate a parametrically-enhanced electromechanical coupling of ${g/2 π} = 1.1$ MHz, sufficient to enter the strong-coupling regime with a cooperativity of $\mathcal{C} = 1200$. The absence of piezoelectric materials in our platform leads to long mechanical lifetimes, finding intrinsic values up to $τ_\text{d} = 265~ μ$s ($Q = 8.4 \times {10}^6$ at $ω_\mathrm{m}/2π= 5$ GHz) measured at low-phonon numbers and millikelvin temperatures. Despite the strong parametric drives, we find the cavity-mechanics system in the quantum ground state by performing sideband thermometry measurements. Simultaneously achieving ground-state operation, long mechanical lifetimes, and strong coupling sets the stage for employing silicon electromechanical resonators as memory elements and transducers in hybrid quantum systems, and as a tool for probing the origins of acoustic loss in the quantum regime.

quant-ph↗

arXiv2022

Deep sub-wavelength localization of light and sound in dielectric resonators

Optomechanical crystals provide coupling between phonons and photons by confining them to commensurate wavelength-scale dimensions. We present a new concept for designing optomechanical crystals capable of achieving unprecedented coupling rates by confining optical and mechanical waves to deep sub-wavelength dimensions. Our design is based on a dielectric bowtie unit cell with an effective optical/mechanical mode volume of $7.6 \times 10^{-3} {(λ/n_{\textrm{Si}})}^3$/$ 1.2 \times 10^{-3} {λ_{\textrm{mech}}}^3$. We present results from numerical modeling, indicating a single-photon optomechanical coupling of 2.2 MHz with experimentally viable parameters. Monte Carlo simulations are used to demonstrate the design's robustness against fabrication disorder.

physics.optics↗