arXiv subjects

Juliet T. Gopinath

Publications and source records attributed to Juliet T. Gopinath.

8 recordsLinked to original sources

arXiv2026

High-performance source of indistinguishable polarization-entangled photons with a local oscillator reference for quantum networking

Optical quantum networking protocols impose stringent requirements on the states produced by sources of entanglement. We demonstrate a free-space, compact, source of indistinguishable pairs of polarization entangled photons, with an integrated local oscillator reference as a significant step towards this goal. This source achieves $(99.11 \pm 0.01) \%$ polarization entanglement visibility, $(96.3 \pm 0.6) \%$ successive-photon Hong-Ou-Mandel interference visibility, $(68.0 \pm 0.1$) \% heralded efficiency as detected, and $(88.6 \pm 0.2) \%$ interference visibility with a local oscillator. This simultaneous achievement of state-of-the-art metrics demonstrates an adaptable platform for quantum networking.

quant-ph↗

arXiv2025

Ultrahigh-Q chalcogenide micro-racetrack resonators

High-quality factor microresonators are an attractive platform for the study of nonlinear photonics, with diverse applications in communications, sensing, and quantum metrology. The characterization of loss mechanisms and nonlinear properties in a microresonator is a necessity for the development of photonic integrated circuits. Here, we demonstrate a high-quality chalcogenide ($Ge_{23}Sb_{7}S_{70}$) micro-racetrack resonator utilizing Euler curves. The racetrack geometry is studied to minimize loss at both the straight-curved waveguide junction and through the waveguide curve. The material absorption, intrinsic quality factor, and nonlinear index are extracted by a comprehensive model fit to laser wavelength resonance scans. The micro-racetrack resonator possesses an absorption loss of $0.43 dB/m$, an intrinsic quality factor of $4.5 \times 10^6$, and nonlinear index of $1.28 \times 10^{-18} m^2/W$, in a waveguide cross-section less than $1 μm^2$. Our results yield state-of-the-art nonlinear microresonators and establish $Ge_{23}Sb_{7}S_{70}$ as a low-loss PIC platform.

physics.optics↗

arXiv2025

Nonlinear Symmetry Breaking to Enhance the Sagnac Effect in a Microresonator Gyroscope

Optical gyroscopes based on the Sagnac effect have been widely used for inertial navigation in aircrafts, submarines, satellites and unmanned robotics. With the rapid progress in the field of ultrahigh-quality whispering gallery mode and ring resonators in recent years, these devices offer the promise of a compact alternative to ring-laser gyroscopes (RLGs) and fiber-optic gyroscopes (FOGs). Yet, successful commercialization of a microresonator gyroscope has been hindered by the scaling of the Sagnac effect with resonator area. While several techniques have been proposed to enhance the Sagnac effect in microresonators, these enhancements also amplify the thermal noise in the microresonator. Here, we present a novel approach to measuring the Sagnac signal in chip-scale devices that overcomes this fundamental noise limitation to achieve unprecedented performance in a 200 μm optical resonator - the smallest reported to date. Our proof-of-concept design shows a 10^4 enhancement of the Sagnac signal while simultaneously suppressing thermal noise by 27 dB and environmental contributions to noise by 22 dB. We believe this approach offers a pathway for integrated photonic gyroscopes with sensitivities that match or exceed RLGs and FOGs.

physics.optics↗

arXiv2025

Cascaded Multiparameter Quantum Metrology

We present an innovative, platform-independent concept for multiparameter sensing where the measurable parameters are in series, or cascaded, enabling measurements as a function of position. With temporally resolved detection, we show that squeezing can give a quantum enhancement in sensitivity over that of classical states by a factor of $e^{2r}$, where $r \approx 1$ is the squeezing parameter. As an example, we have modeled an interferometer that senses multiple phase shifts along the same path, demonstrating a maximal quantum advantage by combining a coherent state with squeezed vacuum. Further classical modeling with up to 100 phases shows linear scaling potential for adding nodes to the sensor. The approach represents a new paradigm in multiparameter quantum metrology, and can be applied to remote sensing, geophysical surveying, and infrastructure monitoring.

quant-ph↗

arXiv2022

Cascaded forward Brillouin lasing in a chalcogenide whispering gallery mode microresonator

We report the first observation of cascaded forward stimulated Brillouin scattering in a microresonator platform. We have demonstrated 25 orders of intramodal Stokes beams separated by a Brillouin shift of 34.5 MHz at a sub-milliwatt threshold at 1550 nm. An As$_2$S$_3$ microsphere of diameter 125 $μm$ with quality factor $1\times 10^6$ was used for this demonstration. Theoretical modeling is used to support our experimental observations of Brillouin shift and threshold power. We expect our work will advance the field of forward stimulated Brillouin scattering in integrated photonics with applications in gas sensing and photonic radio frequency sources.

physics.optics↗

arXiv2019

Multi-functional integrated photonics in the mid-infrared with suspended AlGaAs on silicon

The microscale integration of mid- and longwave-infrared photonics could enable the development of fieldable, robust chemical sensors, as well as highly efficient infrared frequency converters. However, such technology would be defined by the choice of material platform, which immediately determines the strength and types of optical nonlinearities available, the optical transparency window, modal confinement, and physical robustness. In this work, we demonstrate a new platform, suspended AlGaAs waveguides integrated on silicon, providing excellent performance in all of these metrics. We demonstrate low propagation losses within a span of nearly two octaves (1.26 to 4.6 $μ$m) with exemplary performance of 0.45 dB/cm at $λ= 2.4$ $μ$m. We exploit the high nonlinearity of this platform to demonstrate 1560 nm-pumped second-harmonic generation and octave-spanning supercontinuum reaching out to 2.3 $μ$m with 3.4 pJ pump pulse energy. With mid-IR pumping, we generate supercontinuum spanning from 2.3 to 6.5 $μ$m. Finally, we demonstrate the versatility of the platform with mid-infrared passive devices such as low-loss 10 $μ$m-radius bends, compact power splitters with 96 $\pm$ 1% efficiency and edge couplers with 3.0 $\pm$ 0.1 dB loss. This platform has strong potential for multi-functional integrated photonic systems in the mid-IR.

physics.app-ph↗

arXiv2017

Efficient Modal Decomposition of Vortex Beams via Holographically Reconstructed Phase

We use phase-shifting digital holography to measure the amplitude and phase of twisted light. In our experiment, a spatial light modulator generates the studied vortex beams in addition to a co-propagating reference beam with a controllable relative phase. We show complex field measurements for single and superposition Laguerre Gaussian (LG) modes, demonstrate full modal decompositions into LG and orbital angular momentum (OAM) power spectral bases, provide error analysis and demonstrate high insensitivity to detector misalignment to show the robustness of the technique. This enables rapid determination of OAM spectra with low uncertainty, allowing us to report the first vortex beams with 99.9% purity.

physics.optics↗

arXiv2016

Ionic liquid-based variable focus electrowetting optics with bandwidths spanning the visible to mid-infrared

Infrared optical materials and devices are important for a wide range of applications in the defense, scientific, and consumer markets. For imaging, spectroscopy, microscopy and persistent surveillance, adaptive optic systems that span the visible to infrared region are particularly useful. We address this need with novel electrowetting lens and prism elements that operate from 400 to 5000 nm. In contrast to conventional electrowetting devices that use polar liquids, limited by high absorption in the infrared region, we present room-temperature ionic liquid-based (RTIL, N-Propyl-Nmethylpyrrolidinium Bis(fluorosulfonyl)imide, Pyr1333a, Solvionic) lens and prism elements with unprecedented spectral bandwidths. Our electrowetting lenses tune over 20 diopters and have been demonstrated at 588, 1550 and 3000 nm wavelengths. Additionally, we have demonstrated prism elements with a steering angle of 0.56° at 1550 nm.

physics.optics↗