Publications

2017
Lee, Brian S., Mian Zhang, Felippe A. S. Barbosa, Steven A. Miller, Aseema Mohanty, Raphael St-Gelais, and Michal Lipson. “On-chip thermo-optic tuning of suspended microresonators.” Opt. Express 25 (2017): 12109–12120. Publisher's Version Abstract
Suspended optical microresonators are promising devices for on-chip photonic applications such as radio-frequency oscillators, optical frequency combs, and sensors. Scaling up these devices demands the capability to tune the optical resonances in an integrated manner. Here, we design and experimentally demonstrate integrated on-chip thermo-optic tuning of suspended microresonators by utilizing suspended wire bridges and microheaters. We demonstrate the ability to tune the resonance of a suspended microresonator in silicon nitride platform by 9.7 GHz using 5.3 mW of heater power. The loaded optical quality factor (QL  92,000) stays constant throughout the detuning. We demonstrate the efficacy of our approach by completely turning on and off the optical coupling between two evanescently coupled suspended microresonators.
Quantum Interference between Transverse Spatial Waveguide Modes
Mohanty, Aseema, Mian Zhang, Avik Dutt, Sven Ramelow, Paulo Nussenzveig, and Michal Lipson. “Quantum Interference between Transverse Spatial Waveguide Modes.” Nature Communications 8 (2017): 14010. Publisher's Version Abstract
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.
quantum_interference_between_transverse_spatial_waveguide_modes.pdf
2016
Griffith, Austin G., Mengjie Yu, Yoshitomo Okawachi, Jaime Cardenas, Aseema Mohanty, Alexander L. Gaeta, and Michal Lipson. “Coherent mid-infrared frequency combs in silicon-microresonators in the presence of Raman effects.” Opt. Express 24 (2016): 13044–13050. Publisher's Version Abstract
We demonstrate the first low-noise mid-IR frequency comb source using a silicon microresonator. Our observation of strong Raman scattering lines in the generated comb suggests that interplay between Raman and four-wave mixing plays a role in the generated low-noise state. In addition, we characterize, the intracavity comb generation dynamics using an integrated PIN diode, which takes advantage of the inherent three-photon absorption process in silicon.
coherent_mid-infrared_frequency_combs_in_silicon-microresonators_in_the_presence_of_raman_effects.pdf
2015
Griffith, Austin G., Ryan K. W. Lau, Jaime Cardenas, Yoshitomo Okawachi, Aseema Mohanty, Romy Fain, Yoon Ho Daniel Lee, et al.. “Silicon-chip mid-infrared frequency comb generation.” Nature Communications 6 (2015). Abstract
Optical frequency combs are a revolutionary light source for high-precision spectroscopy because of their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared spectral region (2-20 mm) is important for molecular gas detection owing to the presence of a large number of absorption lines in this wavelength regime. Microresonator-based frequency comb sources can provide a compact and robust platform for comb generation that can operate with relatively low optical powers. However, material and dispersion engineering limitations have prevented the realization of an on-chip integrated mid-infrared microresonator comb source. Here we demonstrate a complementary metal-oxide-semiconductor compatible platform for on-chip comb generation using silicon microresonators, and realize a broadband frequency comb spanning from 2.1 to 3.5 mm. This platform is compact and robust and offers the potential to be versatile for use outside the laboratory environment for applications such as real-time monitoring of atmospheric gas conditions.