Ashok Kodigala

Optical nonreciprocity plays a key role in almost every optical system, directing light flow and protecting optical components from backscattered light. Controllable forms of on-chip nonreciprocity are needed for the robust operation of increasingly sophisticated photonic integrated circuits (PICs) in the context of classical and quantum computation, networking, communications, and sensing. However, it has been challenging to achieve wideband, low-loss optical nonreciprocity on-chip. In this paper, we demonstrate strong coupling and Rabi-like energy exchange between photonic bands, possessing a continuum of modes, to unlock nonreciprocity and frequency translation over wide optical bandwidths in silicon. Using a traveling-wave phonon field to drive indirect interband photonic transitions, we demonstrate band hybridization that enables an intriguing form of nonreciprocal dissipation engineering. Using the …

Integrated photonics could bring transformative breakthroughs in computing, networking, imaging, sensing, and quantum information processing, enabled by increasingly sophisticated optical functionalities on a photonic chip. However, wideband optical isolators, which are essential for the robust operation of practically all optical systems, have been challenging to realize in integrated form due to the incompatibility of magnetic media with these circuit technologies. Here, we present the first-ever demonstration of an integrated non-magnetic optical isolator with terahertz-level optical bandwidth. The system is comprised of two acousto-optic frequency-shifting beam splitters which create a non-reciprocal multimode interferometer exhibiting high-contrast, nonreciprocal light transmission. We dramatically enhance the isolation bandwidth of this system by precisely dispersion balancing the paths of the interferometer. Using this approach, we demonstrate integrated nonmagnetic isolators with an optical contrast as high as 28 dB, insertion losses as low as -2.16 dB, and optical bandwidths as high as 2 THz (16 nm). We also show that the center frequency and direction of optical isolation are rapidly reconfigurable by tuning the relative phase of the microwave signals used to drive the acousto-optic beam splitters. With their CMOS compatibility, wideband operation, low losses, and rapid reconfigurability, such integrated isolators could address a key barrier to the integration of a wide range of photonic functionalities on a chip. Looking beyond the current demonstration, this bandwidth-scalable approach to nonmagnetic isolation opens the door to …

Quantum inertial sensors based on cold atom interferometry have been demonstrated to measure acceleration and angular velocity with excellent sensitivity and long-term stability. Significant efforts are underway to apply them in real-world environments. With the goal of elucidating the path to a compact field-deployable quantum inertial measurement unit that uses a 3-axis quantum accelerometer and a 3-axis quantum gyroscope, we present a multifaceted approach based on high data rate atom interferometry with a grating magneto-optical trap, time-multiplexed multi-axis inertial sensing, photonic integrated circuit laser systems, and membrane photonic platforms for guided atom interferometry with evanescent field modes.

Hybrid bonded silicon nitride thin-film lithium niobate (TFLN) Mach-Zehnder modulators (MZMs) at 1310 nm were designed with metal coplanar waveguide electrodes buried in the silicon-on-insulator (SOI) chip. The MZM devices showed greatly improved performance compared to earlier devices of a similar design, and similar performance to comparable MZM devices with gold electrodes made on top of the TFLN layer. Both devices achieve a 3-dB electro-optic bandwidth greater than 110 GHz and voltage-driven optical extinction ratios greater than 28 dB. Half-wave voltage-length products ( ) of 2.8 and 2.5 cm were measured for the 0.5 and 0.4 cm long buried metal and top gold electrode MZMs, respectively.

New strategies to convert signals between optical and microwave domains could play a pivotal role in advancing both classical and quantum technologies. Through recent studies, electro-optomechanical systems have been used to implement microwave-to-optical conversion using resonant optical systems, resulting in transduction over limited optical bandwidth. Here, we present an optomechanical waveguide system with an integrated piezoelectric transducer that produces electro-optomechanical transduction over a wide optical bandwidth through coupling to a continuum of optical modes. Efficient electromechanical and optomechanical coupling within this system enables bidirectional optical-to-microwave conversion with a quantum efficiency of up to 54.16 dB. When electrically driven, this system produces a low voltage acousto-optic phase modulation over a wide (100 nm) wavelength range. Through optical-to-microwave conversion, we show that the amplitude-preserving nature inherent to forward Brillouin scattering is intriguing and has the potential to enable new schemes for microwave photonic signal processing. We use these properties to demonstrate a multi-channel microwave photonic filter by transmitting an optical signal through a series of electro-optomechanical waveguide segments having distinct resonance frequencies. Building on these demonstrations, such electro-optomechanical systems could bring flexible strategies for modulation, channelization, and spectrum analysis in microwave photonics.

TFLN/silicon photonic modulators featuring active silicon photonic components are reported with a V π of 3.6 Vcm. This hybrid architecture utilizes the bottom of the buried oxide as the bonding surface which features minimum topology.

We demonstrate wideband strong coupling between two photonic bands via electrically-driven acousto-optic scattering. Based on this system, we demonstrate a non-magnetic, low-loss (< 1 dB) and broadband (59 GHz 10 dB isolation bandwidth) optical isolator.

We report nonreciprocal wave propagation with~ 10dB nonreciprocity over a 32 nm optical bandwidth based on inter-band acousto-optic scattering within a silicon photonic waveguide system.

We demonstrate an efficient non-magnetic optical isolator based on electrically-driven inter-band acousto-optic scattering in an AlN-on-SOI photonic device. The isolator exhibits< 1 dB insertion loss and 10 dB of isolation over a 50 GHz bandwidth.

The extreme miniaturization of a cold-atom interferometer accelerometer requires the development of novel technologies and architectures for the interferometer subsystems. Here, we describe several component technologies and a laser system architecture to enable a path to such miniaturization. We developed a custom, compact titanium vacuum package containing a microfabricated grating chip for a tetrahedral grating magneto-optical trap (GMOT) using a single cooling beam. In addition, we designed a multi-channel photonic-integrated-circuit-compatible laser system implemented with a single seed laser and single sideband modulators in a time-multiplexed manner, reducing the number of optical channels connected to the sensor head. In a compact sensor head containing the vacuum package, sub-Doppler cooling in the GMOT produces 15 μK temperatures, and the GMOT can operate at a 20 Hz data …

The most complicated and challenging system within a light-pulse atom interferometer (LPAI) is the laser system, which controls the frequencies and intensities of multiple laser beams over time to configure quantum gravity and inertial sensors. The main function of an LPAI laser system is to perform cold-atom generation and state-selective detection and to generate coherent two-photon process for the light-pulse sequence. Substantial miniaturization and ruggedization of the laser system can be achieved by bringing together most key functions of the laser and optical system onto a photonic integrated circuit (PIC). Here we demonstrate a high-performance silicon photonic carrier-suppressed single-sideband (CS-SSB) modulator PIC with dual-parallel Mach-Zehnder modulators (DP-MZMs) operating near 1560 nm, which can dynamically shift the frequency of the light for the desired function within the LPAI. Independent RF control of channels in SSB modulator enables the extensive study of imbalances in both the optical and RF phases and amplitudes to simultaneously reach 30 dB carrier suppression and unprecedented 47.8 dB sideband suppression with peak conversion efficiency of-6.846 dB (20.7%). Using a silicon photonic SSB modulator with timemultiplexed frequency shifting in an LPAI laser system, we demonstrate cold-atom generation, state-selective detection, and the realization of atom interferometer fringes to estimate gravitational acceleration, ????≈ 9.77±0.01 m/s2, in a Rubidium (87Rb) atom system.

We demonstrate a silicon photonic carrier-suppressed single-sideband (CS-SSB) modulator with dual-parallel Mach-Zehnder modulators (DP-MZMs) operating near 1550 nm with a measured carrier suppression of 30 dB and an ultra-high sideband suppression (SSR) of 47.8 dB at 1 GHz with peak conversion efficiency of -6.846 dB (20.7%). We extensively study the effects of imbalances in both the optical and RF phases and amplitudes on the side-band performance. Furthermore, with our silicon photonic modulator, we successfully demonstrate state-selective detection for atoms with time-multiplexed frequency shifting and atom interferometer fringes in a Rubidium (Rb) atom system to estimate gravitational acceleration. These multidisciplinary efforts demonstrate progress towards an integrated silicon photonic chip-scale laser system for atom interferometry and quantum information science applications.

Systems and methods according to present principles provide, at room temperature, a bound state in the continuum laser that harnesses optical modes residing in the radiation continuum but nonetheless may possess arbitrarily high quality factors. These counterintuitive cavities are based on resonantly trapped symmetry-compatible modes that destructively interfere. Such systems and methods may be applied towards coherent sources with intriguing topological properties for optical trapping, biological imaging, and quantum communication.

Systems and methods according to present principles provide ways to construct and use tunable exceptional point (EP) singularities in three-dimensional plasmonic nanostructures. Such structures have applications in sensing, communication, imaging, and other fields where, eg, determining sub wavelength features of interest is of value.

Singularities of open systems, known as exceptional points (EPs), have been shown to exhibit increased sensitivities, but the observation of EPs has so far been limited to wavelength-scaled systems subject to the diffraction limit. Plasmons, the collective oscillations of free electrons coupled to photons, shrink the wavelength of light to electronic and molecular length scales. We propose a novel approach to EPs based on spatial symmetry breaking and report their observation in plasmonics at room temperature. The plasmonic EPs are based on the hybridization of detuned resonances in multilayered plasmonic structures to reach a critical complex coupling rate between nanoantenna arrays, resulting in the simultaneous coalescence of the resonances and loss rates. Their utility as sensors of anti-immunoglobulin G, the most abundant immunoglobulin isotype in human serum, is evaluated. Our work opens the way to …

Deployable Cold Atom Interferometry Sensor Platforms Based On Diffractive Optics and Integrated Photonics Page 1 Deployable Cold Atom Interferometry Sensor Platforms Based On Diffractive Optics and Integrated Photonics Jongmin Lee el END Etewf Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the US Department of Energys National Nuclear Security Administration under contract DE-NA0003525. SAND2020-9489C This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the US Department of Energy or the United States Government. Page 2 Outline s Motivation for a compact atom interferometer (Al) s Sandia Development in …

A Cold Atom Interferometry Sensor Platform Based On Diffractive Optics and Integrated Photonics Page 1 A Cold Atom Interferometry Sensor Platform Based On Diffractive Optics and Integrated Photonics Peter Schwindt Mink NASA Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the US Department of Energys National Nuclear Security Administration under contract DE-NA0003525. SAND2020-5997C This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the US Department of Energy or the United States Government. Page 2 Outline • Motivation for a compact atom interferometer (Al) • Component development • Passively pumped …