Research Projects

2019 CLEO

We demonstrate the first phased array operating at blue wavelengths. We show wide-angle beam steering over a 50o field-of-view with a beam width of less than 0.17o using a high confinement silicon nitride waveguide platform.

M. C. Shin, A. Mohanty, K. Watson, G. R. Bhatt, C. T. Phare, S. A. Miller, M. Zadka, B. S. Lee, X. Ji, E. Shim, I. Datta, and M. Lipson, "Chip-scale Blue Phased Array," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper JTh5B.5.

chip-scale blue phased array

We demonstrate miniature silicon nitride (SiN) pure phase modulators in the visible that are robust to fabrication variations. They offer a one-order-of-magnitude reduction in device footprint and power consumption compared to SiN waveguide phase shifters.

G. Liang, H. Huang, S. Shrestha, A. Mohanty, X. Ji, M. C. Shin, M. Lipson, and N. Yu, "Micron-scale, Efficient, Robust Phase Modulators in the Visible," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper JTh5B.4.

micron-scale visible phase shifter

We demonstrate a platform for low-power solid-state beam steering in 2D using a single wavelength. This platform, based on a metalens and a switchable emitter array, enables steering of 12.4o×26.8o using less than 83 mW.

Y. Chang, M. C. Shin, C. T. Phare, S. A. Miller, E. Shim, and M. Lipson, "Metalens-enabled low-power solid-state 2D beam steering," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SF3N.5.

metalens 2D beam steering

We demonstrate high-confinement Si3N4 resonators with intrinsic quality factor more than 1 million using standard PECVD process. We show that by addressing scattering, the loss at 1.6 μm can be as low as 0.4 dB/cm.

X. Ji, S. P. Roberts, and M. Lipson, "High Quality Factor PECVD Si3N4 Ring Resonators Compatible with CMOS Process," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SM2O.6.

highQPECVDSIN

We demonstrate that silicon metamaterial waveguides have a high tolerance to large fabrication variations. We measured only a 5% drop in the Quality factor of a resonator with a metamaterial segment compared to a 40% drop for a wire waveguide segment, with a 50 nm discontinuity.

M. Zadka, U. D. Dave, and M. Lipson, "High Tolerance of Metamaterial Waveguides to Fabrication Variations," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SF1J.7.

high tolerance of metamaterial

We demonstrate passive PT symmetry breaking between the spatial modes within a single SOI waveguide with metal deposited directly on top. By leveraging this effect, we show low propagation loss of< 1 dB for a 100 μm long, 10 μm wide waveguide partially covered with 100 nm thick metal.

U. D. Dave and M. Lipson, "Low Loss Propagation in a Metal-clad Waveguide via PT-Symmetry Breaking," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper FW4D.4.

metal-clad waveguide via PT

We demonstrate robust mode conversion up to the 12th higher order mode in silicon waveguides by using an optimized adiabatic directional coupler and using subwavelength waveguides. The conversion efficiency is better than -1.5 dB over a 75 nm bandwidth and tolerating ±30 nm fabrication variations.

U. D. Dave and M. Lipson, "Efficient Conversion to Very High Order Modes in Silicon Waveguides," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SM3J.6.

very high order modes

We demonstrate phase modulation in the near IR by electrostatically doping 2D semiconductor monolayers integrated on SiN waveguides. We show a VπL of 1.4 Vcm and 0.8 Vcm for MoS2 and WS2, respectively.

I. Datta, S. H. Chae, G. R. Bhatt, B. Li, Y. Yu, C. Park, J. Park, L. Cao, D. N. Basov, J. Hone, and M. Lipson, "Composite photonic platform based on 2D semiconductor monolayers," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper FTu3C.2.

composite 2D monolayers

We report the long-term stabilization of a soliton micro-comb over 9 days of continuous operation. Using an integrated heater, the original pump-cavity detuning is maintained with a simple active feedback method.

T. Lin, A. Dutt, X. Ji, C. T. Phare, C. Joshi, O. A. Jimenez Gordillo, M. C. Shin, A. L. Gaeta, and M. Lipson, "Long-Term Stabilization and Operation of a Soliton Micro-Comb for 9-Days," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper STu3J.5.

long-term stabilization

We demonstrate continuous scanning of a single soliton micro-comb over 88 GHz with an instantaneous linewidth of 60 kHz. We show such a system can acquire spectra of HCN with a high spectral-resolution.

T. Lin, A. Dutt, X. Ji, C. Joshi, A. L. Gaeta, and M. Lipson, "Broadband High-Resolution Scanning of Soliton Micro-Combs," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SF3H.6.

broadband high-resolution scanning

We demonstrate on-chip coupling between degenerate parametric oscillators (OPO’s) in two different silicon nitride microresonators. The system offers potential towards creating a network of OPO’s for the realization of a photonic coherent Ising machine.

Y. Okawachi, M. Yu, X. Ji, J. K. Jang, M. Lipson, and A. L. Gaeta, "Coupled Degenerate Parametric Oscillators Towards Photonic Coherent Ising Machine," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper FM1D.6.

coherent Ising machine

We experimentally demonstrate soliton mode-locked Kerr comb generation at near-visible wavelengths in a silicon nitride microresonator. We achieve the shortest wavelength to-date for mode-locked Kerr combs through dispersion engineering of a higher-order mode.

Y. Zhao, X. Ji, B. Y. Kim, P. Donvalkar, J. Jang, C. Joshi, M. Yu, R. R. Domeneguetti, F. A. S. Barbosa, P. Nussenzveig, Y. Okawachi, M. Lipson, and A. L. Gaeta, "Near-Visible Microresonator-Based Soliton Combs," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper STh3J.1.

visible soliton microcombs

We demonstrate that large pure optical phase modulation is possible in resonators operated in the strongly over-coupling regime, which suggests efficient phase modulators with high-speed operation, small footprint, low insertion loss, and low power consumption.

G. Liang, H. Huang, S. Shrestha, I. Datta, M. Lipson, and N. Yu, "Efficient Pure Phase Optical Modulator Based on Strongly Over-Coupled Resonators," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper STh3H.1.

efficient pure phase modulator

We experimentally demonstrate sub-harmonic synchronization of separated soliton-modelocked Kerr frequency combs. Through passive optical coupling between microresonators, we demonstrate entrainments between combs with mode spacings related by integer factors of 2 and 3.

J. K. Jang, X. Ji, C. Joshi, Y. Okawachi, M. Lipson, and A. L. Gaeta, "Sub-Harmonic Synchronization of Kerr Frequency Combs," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper FM1D.4.

Sub-harmonic synchronization

Continuous time (CT) Electro Optic Phase Locked Loops (EOPLLs) can significantly reduce the differential delay required in a Mach-Zehnder Interferometer (MZI) which is used to detect the chirp slope, thereby reducing the MZI area and associated loss. However, CT-EOPLLs produce inter-modulation tone at (fref+fbeat) which creates spurs at offsets of ±(fref+fbeat),±2 (fref+fbeat),±3 (fref+fbeat)… from the expected beat tone at the ranging output. In this work, we present a CT-EO-PLL which not only breaks the fundamental trade-off between chirp bandwidth and MZI delay, but also completely eliminates spurs from the PLL and laser output by using IQ single-sideband (SSB) and harmonic reject (HR) mixing. This EO-PLL, integrated in CMOS technology, suppresses the spurs at beat note by> 25dB, enabling us to detect an object at a maximum range of >3.3m, with a precision of 558µm at 2m distance.

S. Ahasan, A. Binaie, C. T. Phare, M. Lipson, and H. Krishnaswamy, "A Compact, Low Loss Integrated Continuous-Time Electro Optic-PLL with Maximum Range of > 3.3m," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SM1N.6.

EO PLL

Using a single silicon-nitride waveguide, we demonstrate an f-2f interferometer for carrier-envelope-offset frequency (fCEO) detection by simultaneous supercontinuum generation and second-harmonic generation. We measure a fCEO beatnote with a 27-dB SNR with 62-pJ pulse energies.

Y. Okawachi, M. Yu, J. Cardenas, X. Ji, M. Lipson, and A. L. Gaeta, "Silicon-Chip-Based f-2f Interferometer," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SF3H.4.

silicon f-2f interferometer

We combine microfluidic technology with microresonator-based mid-infrared dual-comb spectroscopy. We measure flow dynamics of acetone with a spectral acquisition rate of 200-kHz over 90 cm-1 span and <150 fL sample volume over a 100-ms period.

M. Yu, Y. Okawachi, A. G. Griffith, M. Lipson, and A. L. Gaeta, "Microfluidic Mid-Infrared Spectroscopy via Microresonator-Based Dual-Comb Source," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper JW2A.82.

microfluidic mid-infrared spectroscopy