Bachelor of Technology, Indian Institute of Technology, Kharagpur, ECE (2011)
Doctor of Philosophy, Cornell University (2017)
Experimental band structure spectroscopy along a synthetic dimension.
2019; 10 (1): 3122
There has been significant recent interest in synthetic dimensions, where internal degrees of freedom of a particle are coupled to form higher-dimensional lattices in lower-dimensional physical structures. For these systems, the concept of band structure along the synthetic dimension plays a central role in their theoretical description. Here we provide a direct experimental measurement of the band structure along the synthetic dimension. By dynamically modulating a resonator at frequencies commensurate with its mode spacing, we create a periodically driven lattice of coupled modes in the frequency dimension. The strength and range of couplings can be dynamically reconfigured by changing the modulation amplitude and frequency. We show theoretically and demonstrate experimentally that time-resolved transmission measurements of this system provide a direct readout of its band structure. We also realize long-range coupling, gauge potentials and nonreciprocal bands by simply incorporating additional frequency drives, enabling great flexibility in band structure engineering.
View details for DOI 10.1038/s41467-019-11117-9
View details for PubMedID 31311928
A single photonic cavity with two independent physical synthetic dimensions.
Science (New York, N.Y.)
The concept of synthetic dimensions has generated interest in many branches of science ranging from ultracold-atomic physics to photonics, as it provides a versatile platform for realizing effective gauge potentials and topological physics. Previous experiments have augmented the real-space dimensionality by one additional physical synthetic dimension. We endow a single ring resonator with two independent physical synthetic dimensions. Our system consists of a temporally modulated ring resonator with spatial coupling between the clockwise and counterclockwise modes, creating a synthetic Hall ladder along the frequency and pseudospin degrees of freedom for photons propagating in the ring. We observe a wide variety of rich physics, including effective spin-orbit coupling, magnetic fields, spin-momentum locking, a Meissner-to-vortex phase transition, and signatures of topological chiral one-way edge currents, completely in synthetic dimensions. Our experiments demonstrate that higher-dimensional physics can be studied in simple systems by leveraging the concept of multiple simultaneous synthetic dimensions.
View details for DOI 10.1126/science.aaz3071
View details for PubMedID 31780626
On-chip dual-comb source for spectroscopy.
2018; 4 (3): e1701858
Dual-comb spectroscopy is a powerful technique for real-time, broadband optical sampling of molecular spectra, which requires no moving components. Recent developments with microresonator-based platforms have enabled frequency combs at the chip scale. However, the need to precisely match the resonance wavelengths of distinct high quality-factor microcavities has hindered the development of on-chip dual combs. We report the simultaneous generation of two microresonator combs on the same chip from a single laser, drastically reducing experimental complexity. We demonstrate broadband optical spectra spanning 51 THz and low-noise operation of both combs by deterministically tuning into soliton mode-locked states using integrated microheaters, resulting in narrow (<10 kHz) microwave beat notes. We further use one comb as a reference to probe the formation dynamics of the other comb, thus introducing a technique to investigate comb evolution without auxiliary lasers or microwave oscillators. We demonstrate high signal-to-noise ratio absorption spectroscopy spanning 170 nm using the dual-comb source over a 20-μs acquisition time. Our device paves the way for compact and robust spectrometers at nanosecond time scales enabled by large beat-note spacings (>1 GHz).
View details for PubMedID 29511733
View details for PubMedCentralID PMC5834308
Quantum interference between transverse spatial waveguide modes.
2017; 8: 14010
Integrated quantum optics has the potential to markedly reduce the footprint and resource requirements of quantum information processing systems, but its practical implementation demands broader utilization of the available degrees of freedom within the optical field. To date, integrated photonic quantum systems have primarily relied on path encoding. However, in the classical regime, the transverse spatial modes of a multi-mode waveguide have been easily manipulated using the waveguide geometry to densely encode information. Here, we demonstrate quantum interference between the transverse spatial modes within a single multi-mode waveguide using quantum circuit-building blocks. This work shows that spatial modes can be controlled to an unprecedented level and have the potential to enable practical and robust quantum information processing.
View details for PubMedID 28106036
View details for PubMedCentralID PMC5263888
- On-Chip Optical Squeezing PHYSICAL REVIEW APPLIED 2015; 3 (4)
- Smooth double barriers in quantum mechanics AMERICAN JOURNAL OF PHYSICS 2010; 78 (12): 1352–60
- Large expert-curated database for benchmarking document similarity detection in biomedical literature search DATABASE-THE JOURNAL OF BIOLOGICAL DATABASES AND CURATION 2019
- Broadband enhancement of thermal radiation OPTICS EXPRESS 2019; 27 (12): A818–A828
- Loss of polarization of elliptically polarized collapsing beams PHYSICAL REVIEW A 2019; 99 (3)
- Experimental Demonstration of Dynamical Input Isolation in Nonadiabatically Modulated Photonic Cavities ACS PHOTONICS 2019; 6 (1): 162–69
Long-Term Stabilization and Operation of a Soliton Micro-Comb for 9-Days
View details for Web of Science ID 000482226301402
Absence of frequency ranges of undirectional propagation in nonreciprocal plasmonics
View details for Web of Science ID 000482226302198
Experimental Band Structure Spectroscopy along the Synthetic Dimension
View details for Web of Science ID 000482226300311
Pulse shortening in two coupled rings under amplitude modulations with parity-time symmetry
View details for Web of Science ID 000482226302433
- Pulse shortening in an actively mode-locked laser with parity-time symmetry APL PHOTONICS 2018; 3 (8)
Compact narrow-linewidth integrated laser based on a low-loss silicon nitride ring resonator
2017; 42 (21): 4541–44
We design and demonstrate a compact, narrow-linewidth integrated laser based on low-loss silicon nitride waveguides coupled to a III-V gain chip. By using a highly confined optical mode, we simultaneously achieve compact bends and ultra-low loss. We leverage the narrowband backreflection of a high-Q microring resonator to act as a cavity output mirror, a single-mode filter, and a propagation delay all in one. This configuration allows the ring to provide feedback and obtain a laser linewidth of 13 kHz with 1.7 mW output power around 1550 nm. This demonstration realizes a compact sub-millimeter silicon nitride laser cavity with a narrow linewidth.
View details for DOI 10.1364/OL.42.004541
View details for Web of Science ID 000414097200077
View details for PubMedID 29088208
- Ultra-low-loss on-chip resonators with sub-milliwatt parametric oscillation threshold OPTICA 2017; 4 (6): 619–24
- On-chip broadband ultra-compact optical couplers and polarization splitters based on off-centered and non-symmetric slotted Siwire waveguides JOURNAL OF OPTICS 2016; 18 (10)
Tunable squeezing using coupled ring resonators on a silicon nitride chip
2016; 41 (2): 223–26
We demonstrate continuous tuning of the squeezing-level generated in a double-ring optical parametric oscillator by externally controlling the coupling condition using electrically controlled integrated microheaters. We accomplish this by utilizing the avoided crossing exhibited by a pair of coupled silicon nitride microring resonators. We directly detect a change in the squeezing level from 0.5 dB in the undercoupled regime to 2 dB in the overcoupled regime, which corresponds to a change in the generated on-chip squeezing factor from 0.9 to 3.9 dB. Such wide tunability in the squeezing level can be harnessed for on-chip quantum-enhanced sensing protocols that require an optimal degree of squeezing.
View details for DOI 10.1364/OL.41.000223
View details for Web of Science ID 000369050100008
View details for PubMedID 26766679
Optical nonlinearities in high-confinement silicon carbide waveguides
2015; 40 (17): 4138–41
We demonstrate strong nonlinearities of n2=8.6±1.1×10(-15) cm2 W(-1) in single-crystal silicon carbide (SiC) at a wavelength of 2360 nm. We use a high-confinement SiC waveguide fabricated based on a high-temperature smart-cut process.
View details for DOI 10.1364/OL.40.004138
View details for Web of Science ID 000360810200055
View details for PubMedID 26368731
Tunable frequency combs based on dual microring resonators
2015; 23 (16): 21527–40
In order to achieve efficient parametric frequency comb generation in microresonators, external control of coupling between the cavity and the bus waveguide is necessary. However, for passive monolithically integrated structures, the coupling gap is fixed and cannot be externally controlled, making tuning the coupling inherently challenging. We design a dual-cavity coupled microresonator structure in which tuning one ring resonance frequency induces a change in the overall cavity coupling condition. We demonstrate wide extinction tunability with high efficiency by engineering the ring coupling conditions. Additionally, we note a distinct dispersion tunability resulting from coupling two cavities of slightly different path lengths, and present a new method of modal dispersion engineering. Our fabricated devices consist of two coupled high quality factor silicon nitride microresonators, where the extinction ratio of the resonances can be controlled using integrated microheaters. Using this extinction tunability, we optimize comb generation efficiency as well as provide tunability for avoiding higher-order mode-crossings, known for degrading comb generation. The device is able to provide a 110-fold improvement in the comb generation efficiency. Finally, we demonstrate open eye diagrams using low-noise phase-locked comb lines as a wavelength-division multiplexing channel.
View details for DOI 10.1364/OE.23.021527
View details for Web of Science ID 000361036400122
View details for PubMedID 26367998
Overcoming Si3N4 film stress limitations for high quality factor ring resonators
2013; 21 (19): 22829–33
Silicon nitride (Si₃N₄) ring resonators are critical for a variety of photonic devices. However the intrinsically high film stress of silicon nitride has limited both the optical confinement and quality factor (Q) of ring resonators. We show that stress in Si₃N₄ films can be overcome by introducing mechanical trenches for isolating photonic devices from propagating cracks. We demonstrate a Si₃N₄ ring resonator with an intrinsic quality factor of 7 million, corresponding to a propagation loss of 4.2 dB/m. This is the highest quality factor reported to date for high confinement Si₃N₄ ring resonators in the 1,550 nm wavelength range.
View details for DOI 10.1364/OE.21.022829
View details for Web of Science ID 000325547200104
View details for PubMedID 24104169
- Splitting of degenerate states in one-dimensional quantum mechanics EUROPEAN PHYSICAL JOURNAL PLUS 2012; 127 (3)
- Design of Tunable Couplers Using Magnetic Fluid Filled Three-Core Optical Fibers IEEE PHOTONICS TECHNOLOGY LETTERS 2012; 24 (3): 164–66
Light-assisted templated self assembly using photonic crystal slabs
2011; 19 (12): 11422–28
We explore a technique which we term light-assisted templated self-assembly. We calculate the optical forces on colloidal particles over a photonic crystal slab. We show that exciting a guided resonance mode of the slab yields a resonantly-enhanced, attractive optical force. We calculate the lateral optical forces above the slab and predict that stably trapped periodic patterns of particles are dependent on wavelength and polarization. Tuning the wavelength or polarization of the light source may thus allow the formation and reconfiguration of patterns. We expect that this technique may be used to design all-optically reconfigurable photonic devices.
View details for DOI 10.1364/OE.19.011422
View details for Web of Science ID 000292865500044
View details for PubMedID 21716373
- Capillary optical fibers: design and applications for attaining a large effective mode area JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2011; 28 (6): 1431–38