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Nitesh Chauhan

Publications and source records attributed to Nitesh Chauhan.

17 recordsLinked to original sources

Nanophotonic dispersion engineering in tantala-based microresonators with ultralow-loss claddings

Integrated photonics optimized to leverage low loss, nonlinear-optical processes and optoelectronic integration requires robust optical cladding materials and associated fabrication process flows. We develop low-loss silicon dioxide (SiO$_2$) claddings with tantalum pentoxide (Ta$_2$O$_5$, tantala) integrated photonics to realize robust, high intrinsic quality factor ($Q_i$) microresonators and photonic-crystal resonators (PhCRs) for soliton microcomb generation. Specifically, we introduce a full-wafer, low-temperature process compatible with two tantala-based films: pure tantala and an amorphous metal-oxide mixture of titanium dioxide (TiO$_2$, titania) and tantala. Combining tantala with titania enhances the film's resistance to damage from the SiO$_2$ cladding deposition process, offering access to high $Q_i$ above $4 \times 10^6$ in fully cladded microresonators. Our platform supports low-loss edge couplers, group-velocity dispersion engineering by waveguide geometry, access to nanophotonic structures particularly to control phase-matching, and high dimensional tolerance in devices across an entire wafer. Using the platform, we explore the generation of high-efficiency, dark-soliton microcombs with repetition frequency from 50 GHz to 500 GHz, which supports applications such as photonic artificial intelligence acceleration, electronic signaling, and optical data communication.

physics.optics

A Scalable All-to-All Reconfigurable Ising Solver Using Pulsed Time-Division Multiplexing

Physics-based computing platforms, such as those based on the Ising model, are an important pillar of future hardware systems built for the artificial intelligence (AI) era. Such platforms show promise for solving nondeterministic polynomial (NP) time problems that are difficult for traditional processing units to solve efficiently as problem size grows. Here, we present a scalable optoelectronic Ising machine architecture, demonstrated with 64 all-to-all connected spins using pulsed time-division multiplexing. The 65 nm CMOS Ising chip integrates the coupling and nonlinear mechanisms in an active area of 3.1 mm2, eliminating the need for benchtop equipment within the loop. The feedback loop of the Ising machine is closed using a compact high-bandwidth, low-loss optical fiber, seamlessly combining optical scalability with the ultradense reconfigurability of integrated electronics. The chip operates at 1 GHz with 4-bit coupling weights and is benchmarked with NP-complete Boolean satisfiability problems consisting of three literals (3-SAT) and clause-to-variable ratios of 32/32, 40/24, and 48/16. Nanosecond annealing times represent at least a three order-of-magnitude improvement over previously reported all-to-all connected works. Time and energy to solutions for 100% 3-SAT clause accuracy are as low as 7.4 us and 2.9 uJ, respectively, achieving more than an order-of-magnitude decrease in time and energy to solution compared to the state of the art. All-to-all connection is demonstrated using MaxCut problems with 100% graph densities. The chip's ability to effectively solve 2-, 3-SAT, and MaxCut problems highlights its reconfigurability and versatility. Furthermore, combining mature CMOS integration with scalable photonic links allows for significant reduction in computation time and energy, addressing the pressing requirements of AI and future hyperscale datacenters.

physics.optics

Ultra-Low-Noise Brillouin Hybrid Synthetic Laser for Sub-Hertz Lattice Clock Spectroscopy

Frequency-stable lasers enable high-fidelity quantum state manipulation, which forms the basis of optical atomic clocks, quantum sensing, and quantum computation. Performing state manipulations at increasingly high speeds requires attention to laser frequency noise at high Fourier (carrier-offset) frequencies that cannot be addressed by traditional cavity stabilization alone. Scalable operations also benefit from device miniaturization. Here, we demonstrate a hybrid laser stabilization approach that combines ultrahigh frequency stability of a cryogenic silicon cavity with high-Fourier-frequency noise suppression of an integrated Brillouin laser. The combined system suppresses frequency noise over a Fourier span of more than 7 decades, yielding a <1 Hz phase-integrated linewidth and 0.2 Hz^2/Hz frequency noise at Fourier frequencies above 10 MHz. The performance of this hybrid laser is confirmed by sub-Hz Rabi spectroscopy with a three-dimensional ^{87}Sr lattice clock. This work demonstrates record-low frequency noise at 698 nm over an extensive Fourier frequency range and highlights the promise of precision clock spectroscopy using a chip-scale integrated laser technology.

physics.optics

Nanophotonic control of collective many-body states in Kerr solitons

Spatially periodic systems of coupled bosons are governed by on-site interactions and tunneling between sites, opening a rich phase space of many-body behavior. Here, we explore nanophotonic control of collective many-body light states in a driven-dissipative Kerr microresonator. We demonstrate a non-equilibrium Mott insulator to superfluid transition that arises from the interplay of spatially local Kerr interactions that generate and mediate interference among discrete frequency modes. A photonic-crystal (PhC) lattice bandgap inscribed on the resonator controls linear mode coupling while preserving self-mode Kerr interactions. By increasing the PhC bandgap, we suppress nonlinear cross-mode coupling to access the Mott-insulator phase, wherein the soliton spectrum forms a flattop frequency comb with large and uniform power per mode. In contrast, reducing the PhC bandgap restores cross-mode coupling and drives a delocalized superfluid regime characterized by long-range phase coherence and a spectrum with non-uniform power distribution. Our work shows that many-body physics creates collective states in driven-dissipative systems, enabling advances in programmable photonics and quantum-optical computing.

physics.optics

Blue to Near-IR Integrated PZT Silicon Nitride Modulators for Quantum and Atomic Applications

Modulation and control of lasers and optical signals is necessary for trapped-ion and cold neutral atom quantum systems. Given the diversity of atomic species, experimental modalities, and architectures, integrated optical modulators designed to operate across the visible to near-infrared spectrum are a key step towards portable, robust, and compact quantum computers, clocks, and sensors. Integrated optical modulators that are wavelength-independent, CMOS-compatible, and capable of maintaining low waveguide losses and a high resonator quality factor, DC-coupled broadband frequency response, and low power consumption, are essential for scalable photonic integration. Yet progress towards these goals has remained limited. Here we demonstrate four types of integrated stress-optic lead zirconate titanate (PZT) silicon nitride modulators: a coil Mach-Zehnder modulator, a coil pure phase modulator, and bus-coupled and add-drop ring resonator modulators, with operation from 493 nm to 780 nm. The coil MZM operates at 532 nm with a V$π$ of 2.8V, a 0.4 MHz 3-dB bandwidth, and an extinction ratio of 21.5dB. The coil phase modulator operates at 493 nm with a V$π$ of 2.8V and low residual amplitude modulation of -34 dB at a 1kHz offset. The bus-coupled ring resonator modulator operates at 493 nm and the add-drop ring resonator modulator operates at 780 nm. The ring-based modulators have an intrinsic quality factor of 3.4 million and 1.9 million, a linear tuning strength of 0.9 GHz/V and 1 GHz/V, and a 3-dB bandwidth of 2.6 MHz and 10 MHz, respectively. All four modulator designs maintain the low optical waveguide loss of SiN, are DC coupled with broadband frequency response, operate independent of wavelength, and consume only tens of nW per actuator. Such solutions unlock the potential for further integration with other precision SiN components to realize chip-scale atomic and quantum systems.

physics.optics

Sub-Doppler rubidium atom cooling using a programmable agile integrated PZT-on-SiN resonator

Programmability and precise control of laser frequency are essential for quantum experiments and applications such as atomic clocks, quantum computers, and cold-atom sensors. Current systems use bulky, power-hungry modulators and frequency shifters which are difficult to integrate and limit portability and scalability. We report an electrically controllable, agile optical frequency source based on a semiconductor laser stabilized to a photonic-integrated, lead zirconate titanate (PZT)-actuated resonator cavity. We demonstrate this approach with precision programmable frequency control of a 780-nm laser that can periodically reference to rubidium spectroscopy followed by fast, programmable, arbitrary frequency tuning sequences for quantum control. We use this approach to demonstrate sub-Doppler cooling of rubidium-87 without any external modulators, achieving atom-cloud temperatures as low as 16 $μ$K. The device achieves a tuning strength up to 1 GHz/V with 11 MHz modulation bandwidth while consuming only 10 nW of electrical power. This work establishes a route toward compact, low-power, and chip-scale laser systems for next-generation quantum and atomic sensing technologies.

physics.optics

Octave Spanning Visible to SWIR Integrated Coil-Stabilized Brillouin Lasers

Narrow linewidth stabilized lasers are central to precision applications that operate across the visible to short-wave infrared wavelengths, including optical clocks, quantum sensing and computing, ultra-low noise microwave generation, and fiber sensing. Today, these spectrally pure sources are realized using multiple external cavity tabletop lasers locked to bulk-optic free-space reference cavities. Integration of this technology will enable portable precision applications with improved reliability and robustness. Here, we report wavelength-flexible design and operation, over more than an octave span, of an integrated coil-resonator-stabilized Brillouin laser architecture. Leveraging a versatile two-stage noise reduction approach, we achieve low linewidths and high stability with chip-scale laser designs based on the ultra-low-loss, CMOS-compatible silicon nitride platform. We report operation at 674 and 698 nm for applications to strontium neutral and trapped-ion clocks, quantum sensing and computing, and at 1550 nm for applications to fiber sensing and ultra-low phase noise microwave generation. Over this range we demonstrate frequency noise reduction from 1 Hz to 10 MHz resulting in 1.0 Hz -17 Hz fundamental and 181 Hz - 630 Hz integral linewidths and an Allan deviation of 6.5 x 10-13 at 1 ms for 674 nm, 6.0 x 10-13 at 15 ms for 698 nm, and 2.6 x10-13 at 15 ms for 1550 nm. This represents the lowest achieved linewidths and highest stability for integrated stabilized Brillouin lasers over an order of magnitude improvement in operating wavelength range. These results unlock the potential of integrated, ultra-low-phase-noise stabilized lasers for precision applications and further integration in systems-on-chip solutions.

physics.optics

Multi-laser stabilization with an atomic-disciplined photonic integrated resonator

Precision atomic and quantum experiments rely on ultra-stable narrow linewidth lasers constructed using table-top ultra-low expansion reference cavities. These experiments often require multiple lasers, operating at different wavelengths, to perform key steps used in state preparation and measurement required in quantum sensing and computing. This is traditionally achieved by disciplining a cavity-stabilized laser to a key atomic transition and then transferring the transition linewidth and stability to other lasers using the same reference cavity in combination with bulk-optic frequency shifting such as acousto-optic modulators. Transitioning such capabilities to a low cost photonic-integrated platform will enable a wide range of portable, low power, scalable quantum experiments and applications. Yet, today's bulk optic approaches pose challenges related to lack of cavity tunability, large free spectral range, and limited photonic integration potential. Here, we address these challenges with demonstration of an agile photonic-integrated 780 nm ultra-high-Q tunable silicon nitride reference cavity that performs multiple critical experimental steps including laser linewidth narrowing, high resolution rubidium spectroscopy, dual-stage stabilization to a rubidium transition, and stability transfer to other lasers. We achieve up to 20 dB of frequency noise reduction at 10 kHz offset, precision spectroscopy over a 250 MHz range, and dual-stage locking to rubidium with an Allan deviation of $8.5 \times 10^{-12}$ at 1 s and up to 40 dB reduction at 100 Hz. We further demonstrate the transfer of this atomic stability to a second laser, via the rubidium-disciplined cavity, and demonstrate multi-wavelength Rydberg electrometry quantum sensing. These results pave the path for integrated, compact, and scalable solutions for quantum sensing, computing and other atomic and trapped ion applications.

physics.optics

A Kerr soliton Ising machine for combinatorial optimization problems

The growing challenges of scaling digital computing motivate new approaches, especially through the dynamical evolution of physical systems that mimic neural networks and combinatorial optimization problems. While light is a hyper efficient information carrier, intrinsically weak light interactions make direct information processing difficult to implement. Recently, specialized nonlinear photonics have opened new controls over light fields with extraordinary bandwidth, coherence, and the emergence of strong interactions among nonlinear eigenstates like solitons. We harness an ensemble of hundreds of Kerr-nonlinear microresonator solitons and implement an analog feedback network to create an Ising machine with fully programmable all-to-all interactions. By increasing the feedback for self, on-diagonal interactions, each soliton exhibits a universal spin-like bifurcation. Using this palette of interactions amongst the entire soliton ensemble, we encode the Ising machine to solve the benchmark Boolean satisfiability problem (SAT). The combination of uniform soliton interactions and the compatibility of our Ising machine with high-speed data interconnects enables rapid and precise solutions of complex SAT problems. Indeed, the soliton properties bound the tradeoff of optical power and time use by the machine at approximately 10 mW and 1 $μ$s for a single feedback step. We performed >10,000 trials on more than 100 randomly generated SAT instances to evaluate the Ising machine, demonstrating the potential to exceed the performance of benchmark digital SAT solvers. Our work highlights the convergence of optical nonlinearity, ultralow loss photonics, and optoelectronic circuits, which can be combined for a wide range of computation-acceleration tasks.

physics.optics

Sub-100 Hz Intrinsic Linewidth 852 nm Silicon Nitride External Cavity Laser

We demonstrate an external cavity laser with intrinsic linewidth below 100 Hz around an operating wavelength of 852 nm, selected for its relevance to laser cooling and manipulation of cesium atoms. This system achieves a maximum CW output power of 24 mW, wavelength tunability over 15 nm, and a side-mode suppression ratio exceeding 50 dB. This performance level is facilitated by careful design of a low-loss integrated silicon nitride photonic circuit serving as the external cavity combined with commercially available semiconductor gain chips. This approach demonstrates the feasibility of compact integrated lasers with sub-kHz linewidth centering on the needs of emerging sensor concepts based on ultracold atoms and can be further extended to shorter wavelengths via selection of suitable semiconductor gain media.

physics.optics

Trapped ion qubit and clock operations with a visible wavelength photonic coil resonator stabilized integrated Brillouin laser

Integrating precise, stable, ultra-low noise visible light lasers into atomic systems is critical for advancing quantum information sciences and improving scalability and portability. Trapped ions are a leading approach for high-fidelity quantum computing, high-accuracy optical clocks, and precision quantum sensors. However, current ion-based systems rely on bulky, lab-scale precision lasers and optical stabilization cavities for optical clock and qubit operations, constraining the size, weight, scalability, and portability of atomic systems. Chip-scale integration of ultra-low noise lasers and reference cavities operating directly at optical clock transitions and capable of qubit and clock operations will represent a major transformation in atom and trapped ion-based quantum technologies. However, this goal has remained elusive. Here we report the first demonstration of chip-scale optical clock and qubit operations on a trapped ion using a photonic integrated direct-drive visible wavelength Brillouin laser stabilized to an integrated 3-meter coil-resonator reference cavity and the optical clock transition of a $^{88}$Sr$^+$ ion trapped on a surface electrode chip. We also demonstrate for the first time, to the best of our knowledge, trapped-ion spectroscopy and qubit operations such as Rabi oscillations and high fidelity (99%) qubit state preparation and measurement (SPAM) using direct drive integrated photonic technologies without bulk optic stabilization cavities or second harmonic generation. Our chip-scale stabilized Brillouin laser exhibits a 6 kHz linewidth with the 0.4 Hz quadrupole transition of $^{88}$Sr$^+$ and a self-consistent coherence time of 60 $μ$s via Ramsey interferometry on the trapped ion qubit. Furthermore, we demonstrate the stability of the locked Brillouin laser to 5$\times10^{-13}/ \sqrtτ$ at 1 second using dual optical clocks.

quant-ph

Chip-Scale, Sub-Hz Fundamental Sub-kHz Integral Linewidth 780 nm Laser through Self-Injection-Locking a Fabry-Pérot laser to an Ultra-High Q Integrated Resonator

Today's state of the art precision experiments in quantum, gravimetry, navigation, time keeping, and fundamental science have strict requirements on the level and spectral distribution of laser frequency noise. For example, the laser interaction with atoms and qubits requires ultra-low frequency noise at multiple offset frequencies due to hyperfine atomic transitions, motional sidebands, and fast pulse sequencing. Chip-scale integration of lasers that meet these requirements is essential for reliability, low-cost, and weight. Here, we demonstrate a significant advancement in atomic precision light sources by realizing a chip-scale, low-cost, 780 nm laser for rubidium atom applications with record-low 640 mHz (white noise floor at 0.2 Hz$^2$/Hz) fundamental and 732 Hz integral linewidths and a frequency noise that is multiple orders of magnitude lower than previous hybrid and heterogeneous self-injection locked 780 nm lasers and lower noise than bulk microresonator implementations. The laser is a Fabry-Pérot laser diode self-injection locked to an ultra-high Q photonic integrated silicon nitride resonator. This performance is enabled by a 145 million resonator Q with a 30 dB extinction ratio, the highest Q at 780 nm, to the best of our knowledge. We analyze the impact of our frequency noise on specific atomic applications including atomic frequency references, Rydberg quantum gates, and cold atom gravimeters. The photonic integrated resonator is fabricated using a CMOS foundry-compatible, wafer-scale process, with demonstrated integration of other components showing promise for a full system-on-a-chip. This performance is scalable to other visible atomic wavelengths, opening the door to a variety of transitions across many atomic species and enabling low-power, compact, ultra-low noise lasers impacting applications including quantum sensing, computing, clocks and more.

physics.optics

Photonic integrated beam delivery in a rubidium 3D magneto-optical trap

Cold atoms are important for precision atomic applications including timekeeping and sensing. The 3D magneto-optical trap (3D-MOT), used to produce cold atoms, will benefit from photonic integration to improve reliability and reduce size, weight, and cost. These traps require the delivery of multiple, large area, collimated laser beams to an atomic vacuum cell. Yet, to date, beam delivery using an integrated waveguide approach has remained elusive. We report the demonstration of a 87Rb 3D-MOT using a fiber-coupled photonic integrated circuit to deliver all beams to cool and trap > 1 x 10^6 atoms to near 200 μK. The silicon nitride photonic circuit transforms fiber-coupled 780 nm cooling and repump light via waveguides to three mm-width non-diverging free-space cooling and repump beams directly to the rubidium cell. This planar, CMOS foundry-compatible integrated beam delivery is compatible with other components, such as lasers and modulators, promising system-on-chip solutions for cold atom applications.

physics.optics

36 Hz integral linewidth laser based on a photonic integrated 4.0-meter coil resonator

Laser stabilization sits at the heart of many precision scientific experiments and applications, including quantum information science, metrology and atomic timekeeping. These systems narrow the laser linewidth and stabilize the carrier by use of Pound-Drever-Hall (PDH) locking to a table-scale, ultra-high quality factor (Q), vacuum spaced Fabry-Perot reference cavity. Integrating these cavities, to bring characteristics of PDH stabilization to the chip-scale, is critical to reduce their size, cost, and weight, and enable a wide range of portable and system-on-chip applications. We report a significant advance in integrated laser linewidth narrowing, stabilization and noise reduction, by use of a photonic integrated 4.0-meter-long coil resonator to stabilize a semiconductor laser. We achieve a 36 Hz 1/π-integral linewidth, an Allan deviation (ADEV) of 1.8x10^{-13} at 10 ms measurement time, and a 2.3 kHz/sec drift, to the best of our knowledge the lowest integral linewidth and highest stability demonstrated for an integrated reference cavity. Two coil designs, stabilizing lasers operating at 1550 nm and 1319 nm are demonstrated. The resonator is bus coupled to a 4.0-meter-long coil, with a 49 MHz free spectral range (FSR), a mode volume of 1.0x10^{10} μm^3 and a 142 million intrinsic Q, fabricated in a CMOS compatible, ultra-low loss silicon nitride waveguide platform. Our measurements and simulations show that the thermorefractive noise floor for this particular cavity is reached for frequencies down to 20 Hz in an ambient environment with simple passive vibration isolation and without vacuum or thermal isolation. The TRN limited performance is estimated to be an 8 Hz 1/π integral linewidth and ADEV of 5x10^{-14} at 10 ms, opening a stability regime that heretofore has only been available in fundamentally un-integrated systems.

physics.optics

Photonic circuits for laser stabilization with ultra-low-loss and nonlinear resonators

Laser-frequency stabilization with on-chip photonic integrated circuits will provide compact, low cost solutions to realize spectrally pure laser sources. Developing high-performance and scalable lasers is critical for applications including quantum photonics, precision navigation and timing, spectroscopy, and high-capacity fiber communications. We demonstrate a significant advance in compact, stabilized lasers to achieve a record low integral emission linewidth and precision carrier stabilization by combining integrated waveguide nonlinear Brillouin and ultra-low loss waveguide reference resonators. Using a pair of 56.4 Million quality factor (Q) Si$_3$N$_4$ waveguide ring-resonators, we reduce the free running Brillouin laser linewidth by over an order of magnitude to 330 Hz integral linewidth and stabilize the carrier to 6.5$\times$10$^{-13}$ fractional frequency at 8 ms, reaching the cavity-intrinsic thermorefractive noise limit for frequencies down to 80 Hz. This work demonstrates the lowest linewidth and highest carrier stability achieved to date using planar, CMOS compatible photonic integrated resonators, to the best of our knowledge. These results pave the way to transfer stabilized laser technology from the tabletop to the chip-scale. This advance makes possible scaling the number of stabilized lasers and complexity of atomic and molecular experiments as well as reduced sensitivity to environmental disturbances and portable precision atomic, molecular and optical (AMO) solutions.

physics.optics

Visible light photonic integrated Brillouin laser

Narrow linewidth visible light lasers are critical for atomic, molecular and optical (AMO) applications including atomic clocks, quantum computing, atomic and molecular spectroscopy, and sensing. Historically, such lasers are implemented at the tabletop scale, using semiconductor lasers stabilized to large optical reference cavities. Photonic integration of high spectral-purity visible light sources will enable experiments to increase in complexity and scale. Stimulated Brillouin scattering (SBS) is a promising approach to realize highly coherent on-chip visible light laser emission. While progress has been made on integrated SBS lasers at telecommunications wavelengths, barriers have existed to translate this performance to the visible, namely the realization of Brillouin-active waveguides in ultra-low optical loss photonics. We have overcome this barrier, demonstrating the first visible light photonic integrated SBS laser, which operates at 674 nm to address the 88Sr+ optical clock transition. To guide the laser design, we use a combination of multi-physics simulation and Brillouin spectroscopy in a 2 meter spiral waveguide to identify the 25.110 GHz first order Stokes frequency shift and 290 MHz gain bandwidth. The laser is implemented in an 8.9 mm radius silicon nitride all-waveguide resonator with 1.09 dB per meter loss and Q of 55.4 Million. Lasing is demonstrated, with an on-chip 14.7 mW threshold, a 45% slope efficiency, and linewidth narrowing as the pump is increased from below threshold to 269 Hz. To illustrate the wavelength flexibility of this design, we also demonstrate lasing at 698 nm, the wavelength for the optical clock transition in neutral strontium. This demonstration of a waveguide-based, photonic integrated SBS laser that operates in the visible, and the reduced size and sensitivity to environmental disturbances, shows promise for diverse AMO applications.

physics.optics

422 Million Q Planar Integrated All-Waveguide Resonator with a 3.4 Billion Absorption Limited Q and Sub-MHz Linewidth

High Q optical resonators are a key component for ultra-narrow linewidth lasers, frequency stabilization, precision spectroscopy and quantum applications. Integration of these resonators in a photonic waveguide wafer-scale platform is key to reducing their cost, size and power as well as sensitivity to environmental disturbances. However, to date, the intrinsic Q of integrated all-waveguide resonators has been relegated to below 150 Million. Here, we report an all-waveguide Si3N4 resonator with an intrinsic Q of 422 Million and a 3.4 Billion absorption loss limited Q. The resonator has a 453 kHz intrinsic linewidth and 906 kHz loaded linewidth, with a finesse of 3005. The corresponding linear loss of 0.060 dB/m is the lowest reported to date for an all-waveguide design with deposited upper cladding oxide. These are the highest intrinsic and absorption loss limited Q factors and lowest linewidth reported to date for a photonic integrated all-waveguide resonator. This level of performance is achieved through a careful reduction of scattering and absorption loss components. We quantify, simulate and measure the various loss contributions including scattering and absorption including surface-state dangling bonds that we believe are responsible in part for absorption. In addition to the ultra-high Q and narrow linewidth, the resonator has a large optical mode area and volume, both critical for ultra-low laser linewidths and ultra-stable, ultra-low frequency noise reference cavities. These results demonstrate the performance of bulk optic and etched resonators can be realized in a photonic integrated solution, paving the way towards photonic integration compatible Billion Q cavities for precision scientific systems and applications such as nonlinear optics, atomic clocks, quantum photonics and high-capacity fiber communications systems on-chip.

physics.optics