Miller, Steven A, Mengjie Yu, Xingchen Ji, Austin G Griffith, Jaime Cardenas, Alexander L Gaeta, and Michal Lipson. “Low-Loss Silicon Platform for Broadband Mid-Infrared Photonics.” arXiv:1703.03517 (2017). Publisher's Version Abstract
Broadband mid-infrared (mid-IR) spectroscopy applications could greatly benefit from today's well-developed, highly scalable silicon photonics technology; however, this platform lacks broadband transparency due to its reliance on absorptive silicon dioxide cladding. Alternative cladding materials have been studied, but the challenge lies in decreasing losses while avoiding complex fabrication techniques. Here, in contrast to traditional assumptions, we show that silicon photonics can achieve low-loss propagation in the mid-IR from 3 - 6 um wavelength, thus providing a highly scalable, well-developed technology in this spectral range. We engineer the waveguide cross section and optical mode interaction with the absorptive cladding oxide to reduce loss at mid-IR wavelengths. We fabricate a microring resonator and measure an intrinsic quality (Q) factor of 10^6 at wavelengths from 3.5 to 3.8 um. This is the highest Q demonstrated on an integrated mid-IR platform to date. With this high-Q silicon microresonator, we also demonstrate a low optical parametric oscillation threshold of 5.2 mW, illustrating the utility of this platform for nonlinear chip-scale applications in the mid-IR.
Ji, Xingchen, Felippe AS Barbosa, Samantha P Roberts, Avik Dutt, Jaime Cardenas, Yoshitomo Okawachi, Alex Bryant, Alexander L Gaeta, and Michal Lipson. “Ultra-low-loss on-chip resonators with sub-milliwatt parametric oscillation threshold.” Optica 4, no. 6 (2017): 619. Publisher's Version Abstract
On-chip optical resonators have the promise of revolutionizing numerous fields including metrology and sensing; however, their optical losses have always lagged behind their larger discrete resonator counterparts based on crystalline materials and flowable glass. Silicon nitride (Si3N4) ring resonators open up capabilities for optical routing, frequency comb generation, optical clocks and high precision sensing on an integrated platform. However, simultaneously achieving high quality factor and high confinement in Si3N4 (critical for nonlinear processes for example) remains a challenge. Here, we show that addressing surface roughness enables us to overcome the loss limitations and achieve high-confinement, on-chip ring resonators with a quality factor (Q) of 37 million for a ring with 2.5 {\mu}m width and 67 million for a ring with 10 {\mu}m width. We show a clear systematic path for achieving these high quality factors. Furthermore, we extract the loss limited by the material absorption in our films to be 0.13 dB/m, which corresponds to an absorption limited Q of at least 170 million by comparing two resonators with different degrees of confinement. Our work provides a chip-scale platform for applications such as ultra-low power frequency comb generation, high precision sensing, laser stabilization and sideband resolved optomechanics.
1609.08699.pdf optica-4-6-619.pdf
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.
Dutt, Avik, Chaitanya Joshi, Xingchen Ji, Jaime Cardenas, Yoshitomo Okawachi, Kevin Luke, Alexander L. Gaeta, and Michal Lipson. “On-chip dual comb source for spectroscopy.” arXiv:1611.07673 [physics] (2016). Publisher's Version Abstract
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 an on-chip dual comb source. Here, we report the first simultaneous generation of two microresonator combs on the same chip from a single laser. The combs span a broad bandwidth of 51 THz around a wavelength of 1.56 \$\textbackslashmu\$m. We demonstrate low-noise operation of both frequency combs by deterministically tuning into soliton mode-locked states using integrated microheaters, resulting in narrow (\$\textless\$ 10 kHz) microwave beatnotes. We further use one mode-locked 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 broadband high-SNR absorption spectroscopy of dichloromethane spanning 170 nm using the dual comb source over a 20 \$\textbackslashmu\$s acquisition time. Our device paves the way for compact and robust dual-comb spectrometers at nanosecond timescales.
Dutt, Avik, Steven Miller, Kevin Luke, Jaime Cardenas, Alexander L. Gaeta, Paulo Nussenzveig, and Michal Lipson. “Tunable Squeezing Using Coupled Ring Resonators on a Silicon Nitride Chip.” Opt. Lett. 41 (2016): 223. Publisher's Version Abstract
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.
Mouradian, Sara L., Tim Schroeder, Carl B. Poitras, Luozhou Li, Jordan Goldstein, Edward H. Chen, Michael Walsh, et al.. “Scalable Integration of Long-Lived Quantum Memories into a Photonic Circuit.” Physical Review X 5 (2015). Abstract
We demonstrate a photonic circuit with integrated long-lived quantum memories. Precharacterized quantum nodes-diamond microwaveguides containing single, stable, negatively charged nitrogen-vacancy centers-are deterministically integrated into low-loss silicon nitride waveguides. These quantum nodes efficiently couple into the single-mode waveguides with >1 Mcps collected into the waveguide, have narrow single-scan linewidths below 400 MHz, and exhibit long electron spin coherence times up to 120 mu s. Our system facilitates the assembly of multiple quantum nodes with preselected properties into a photonic integrated circuit with near unity yield, paving the way towards the scalable fabrication of quantum information processors.
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.
Zhang, Mian, Shreyas Shah, Jaime Cardenas, and Michal Lipson. “Synchronization and Phase Noise Reduction in Micromechanical Oscillator Arrays Coupled through Light.” Physical Review Letters, 2015. Abstract
Synchronization of many coupled oscillators is widely found in nature and has the potential to revolutionize timing technologies. Here, we demonstrate synchronization in arrays of silicon nitride micromechanical oscillators coupled in an all-to-all configuration purely through an optical radiation field. We show that the phase noise of the synchronized oscillators can be improved by almost 10 dB below the phase noise limit for each individual oscillator. These results open a practical route towards synchronized oscillator networks.
Graphene electro-optic modulator with 30 GHz bandwidth
Phare, Christopher T., Yoon-Ho Daniel Lee, Jaime Cardenas, and Michal Lipson. “Graphene electro-optic modulator with 30 GHz bandwidth.” Nature Photonics 9 (2015): 511. Abstract
Graphene has generated exceptional interest as an optoelectronic material(1,2) because its high carrier mobility(3,4) and broadband absorption(5) promise to make extremely fast and broadband electro-optic devices possible(6-9). Electro-optic graphene modulators previously reported, however, have been limited in bandwidth to a few gigahertz(10-15) because of the large capacitance required to achieve reasonable voltage swings. Here, we demonstrate a graphene electro-optic modulator based on resonator loss modulation at critical coupling(16) that shows drastically increased speed and efficiency. Our device operates with a 30 GHz bandwidth and with a state-of-the-art modulation efficiency of 15 dB per 10 V. We also show the first high-speed large-signal operation in a graphene modulator, paving the way for fast digital communications using this platform. The modulator uniquely uses silicon nitride waveguides, an otherwise completely passive material platform, with promising applications for ultra-low-loss broadband structures and nonlinear optics.
Stern, Brian, Xiaoliang Zhu, Christine P. Chen, Lawrence D. Tzuang, Jaime Cardenas, Keren Bergman, and Michal Lipson. “On-chip mode-division multiplexing switch.” Optica 2, no. 6 (2015): 530-535. Abstract
Leveraging the spatial modes of multimode waveguides using mode-division multiplexing on an integrated photonic chip allows unprecedented scaling of bandwidth density for on-chip communication. Switching channels between waveguides is critical for future scalable optical networks, but its implementation in multimode waveguides must address how to simultaneously control modes with vastly different optical properties. Here we present a platform for switching signals between multimode waveguides based on individually processing the spatial mode channels using single-mode elements. Using this wavelength-division multiplexing-compatible platform, we demonstrate a 1×2 multimode switch for a silicon chip that routes four data channels with low (<−16.8  dB) crosstalk. We show bit-error rates below 10−9 and power penalties below 1.4 dB on all channels while routing 10 Gb/s data when each channel is input and routed separately. The switch exhibits an additional power penalty of less than 2.4 dB when all four channels are simultaneously routed. These results enable individual processing of multimode signals and high-bandwidth, flexible optical networks.
Cardenas, Jaime, Mengjie Yu, Yoshitomo Okawachi, Carl B. Poitras, Ryan K. W. Lau, Avik Dutt, Alexander L. Gaeta, and Michal Lipson. “Optical nonlinearities in high-confinement silicon carbide waveguides.” Optics Letters 40 (2015): 4138-4141. Publisher's Version Abstract
We demonstrate strong nonlinearities of n(2) = 8.6 +/- 1.1 x 10(-15) cm(2) 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. (C) 2015 Optical Society of America
Cardenas, Jaime, Carl B. Poitras, Kevin Luke, Lian-Wee Luo, Paul Adrian Morton, and Michal Lipson. “High Coupling Efficiency Etched Facet Tapers in Silicon Waveguides.” IEEE Photonics Technology Letters 26 (2014): 2380-2382. Publisher's Version Abstract
We demonstrate a platform based on etched facet silicon inverse tapers for waveguide-lensed fiber coupling with a loss as low as 0.7 dB/facet. This platform can be fabricated on a wafer scale enabling mass-production of silicon photonic devices with broadband, high-efficiency couplers.
Miller, Steven, Kevin Luke, Yoshitomo Okawachi, Jaime Cardenas, Alexander L. Gaeta, and Michal Lipson. “On-chip frequency comb generation at visible wavelengths via simultaneous second- and third-order optical nonlinearities.” Optics Express 22 (2014): 26517-26525. Publisher's Version Abstract
Microresonator-based frequency comb generation at or near visible wavelengths would enable applications in precise optical clocks, frequency metrology, and biomedical imaging. Comb generation in the visible has been limited by strong material dispersion and loss at short wavelengths, and only very narrowband comb generation has reached below 800 nm. We use the second-order optical nonlinearity in an integrated high-Q silicon nitride ring resonator cavity to convert a near-infrared frequency comb into the visible range. We simultaneously demonstrate parametric frequency comb generation in the near-infrared, second-harmonic generation, and sum-frequency generation. We measure 17 comb lines converted to visible wavelengths extending to 765 nm. (C) 2014 Optical Society of America
Guha, Biswajeet, Jaime Cardenas, and Michal Lipson. “Athermal silicon microring resonators with titanium oxide cladding.” Optics Express 21 (2013): 26557-26563. Abstract
We describe a novel approach for CMOS-compatible passively temperature insensitive silicon based optical devices using titanium oxide cladding which has a negative thermo-optic (TO) effect. We engineer the mode confinement in Si and TiO2 such that positive TO of Si is exactly cancelled out by negative TO of TiO2. We demonstrate robust operation of the resulting device over 35 degrees. (C) 2013 Optical Society of America
Cardenas, Jaime, Mian Zhang, Christopher T. Phare, Shreyas Y. Shah, Carl B. Poitras, Biswajeet Guha, and Michal Lipson. “High Q SiC microresonators.” Optics Express 21 (2013): 16882-16887. Abstract
We demonstrate photonic devices based on standard 3C SiC epitaxially grown on silicon. We achieve high optical confinement by taking advantage of the high stiffness of SiC and undercutting the underlying silicon substrate. We demonstrate a 20 mu m radius suspended microring resonator with Q=14,100 fabricated on commercially available SiC-on-silicon substrates. (C) 2013 Optical Society of America
Cardenas, Jaime, Paul A. Morton, Jacob B. Khurgin, Austin Griffith, Carl B. Poitras, Kyle Preston, and Michal Lipson. “Linearized silicon modulator based on a ring assisted Mach Zehnder inteferometer.” Optics Express 21 (2013): 22549-22557. Abstract
We demonstrate a Linearized Ring Assisted Mach-Zehnder Interferometer (L-RAMZI) modulator in a miniature silicon device. We measure a record high degree of linearization for a silicon device, with a Spurious Free Dynamic Range (SFDR) of 106dB/Hz(2)/(3) at 1GHz, and 99dB/Hz(2)/(3) at 10GHz. (c) 2013 Optical Society of America
Johnson, Adrea R., Yoshitomo Okawachi, Jacob S. Levy, Jaime Cardenas, Kasturi Saha, Michal Lipson, and Alexander L. Gaeta. “Chip-based frequency combs with sub-100 GHz repetition rates.” Optics Letters 37 (2012): 875-877. Abstract
By fabricating high-Q silicon-nitride spiral resonators, we demonstrate frequency combs spanning over 200 nm with free spectral ranges (FSRs) of 80, 40, and 20 GHz using cascaded four-wave mixing. We characterize the RF beat note for the 20 GHz FSR comb, and the measured linewidth of 3.6 MHz is consistent with thermal fluctuations in the resonator due to amplitude noise of the pump source. These combs represent an important advance towards developing a complementary metal-oxide-semiconductor (CMOS)-based system capable of linking the optical and electronic regimes. (C) 2012 Optical Society of America
Morton, Paul A., Jaime Cardenas, Jacob B. Khurgin, and Michal Lipson. “Fast Thermal Switching of Wideband Optical Delay Line With No Long-Term Transient.” Ieee Photonics Technology Letters 24 (2012): 512-514. Abstract
We present results for a broad bandwidth continuously tunable optical delay line based on the balanced side-coupled integrated space sequence of resonators scheme. A tunable delay of up to 345 ps is obtained without distortion of the optical signal. Fast thermal switching speed under 10 mu s is achieved without any measurable long-term transient by utilizing a novel balanced thermal tuning scheme.
Griffith, Austin, Jaime Cardenas, Carl B. Poitras, and Michal Lipson. “High quality factor and high confinement silicon resonators using etchless process.” Optics Express 20 (2012): 21341-21345. Abstract
We demonstrate high quality factor and high confinement in a silicon ring resonator fabricated by a thermal oxidation process. We fabricated a 50 mu m bending radius racetrack resonator, with a 5 mu m coupling region. We achieved an intrinsic quality factor of 760,000 for the fundamental TM mode, which corresponds to a propagation loss of 0.9 dB/cm. Both the fundamental TE and TM modes are highly confined in the waveguide, with effective indices of 3.0 for the TE mode and 2.9 for the TM mode. (C) 2012 Optical Society of America
Luo, Lian-Wee, Gustavo S. Wiederhecker, Jaime Cardenas, Carl Poitras, and Michal Lipson. “High quality factor etchless silicon photonic ring resonators.” Optics Express 19, no. 7 (2011): 6284-6289. Abstract
We demonstrate high quality factor etchless silicon photonic ring resonators fabricated by selective thermal oxidation of silicon without the silicon layer being exposed to any plasma etching throughout the fabrication process. We achieve a high intrinsic quality factor of 510,000 in 50 mu m-radius ring resonators, corresponding to a ring loss of 0.8 dB/cm. The device has a total chip insertion loss of 2.5 dB, achieved by designing etchless silicon inverse nanotapers at both the input and output of the chip. (C) 2011 Optical Society of America