Publications

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.
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_sic_nonlinearities_ol_2015.pdf
2014
Lau, Ryan K. W., Michael R. E. Lamont, Austin G. Griffith, Yoshitomo Okawachi, Michal Lipson, and Alexander L. Gaeta. “Octave-spanning mid-infrared supercontinuum generation in silicon nanowaveguides.” Optics Letters 39 (2014): 4518-4521. Publisher's Version Abstract
We report, to the best of our knowledge, the first demonstration of octave-spanning supercontinuum generation (SCG) on a silicon chip, spanning from the telecommunications c-band near 1.5 m to the mid-infrared region beyond 3.6 mu m. The SCG presented here is characterized by soliton fission and dispersive radiation across two zero group-velocity dispersion wavelengths. In addition, we numerically investigate the role of multiphoton absorption and free carriers, confirming that these nonlinear loss mechanisms are not detrimental to SCG in this regime. (C) 2014 Optical Society of America
lau_supercontinuum_si_2014.pdf
2012
Saha, Kasturi, Yoshitomo Okawachi, Jacob S. Levy, Ryan K. W. Lau, Kevin Luke, Mark A. Foster, Michal Lipson, and Alexander L. Gaeta. “Broadband parametric frequency comb generation with a 1-mu m pump source.” Optics Express 20 (2012): 26935-26941. Abstract
We report the first experimental demonstration of broadband frequency comb generation from a single-frequency pump laser at 1-mu m using parametric oscillation in a high-Q silicon-nitride ring resonator. The resonator dispersion is engineered to have a broad anomalous group velocity dispersion region near the pump wavelength for efficient parametric four-wave mixing. The comb spans 55 THz with a 230-GHz free spectral range. These results demonstrate the powerful advantage of dispersion engineering in chip-based devices for producing combs with a wide range of pump wavelengths. (C) 2012 Optical Society of America
Ophir, Noam, Ryan K. W. Lau, Michael Menard, Reza Salem, Kishore Padmaraju, Yoshitomo Okawachi, Michal Lipson, Alexander L. Gaeta, and Keren Bergman. “First Demonstration of a 10-Gb/s RZ End-to-End Four-Wave-Mixing Based Link at 1884 nm Using Silicon Nanowaveguides.” Ieee Photonics Technology Letters 24 (2012): 276-278. Abstract
We demonstrate a double-stage four-wave mixing (FWM) scheme in silicon nanowaveguides which allows effective optical time-division-multiplexed data generation and reception in the 2-mu m region. The scheme is based on a first mixing stage which unicasts a high-speed return-to-zero stream from the C-band to 1884-nm, followed by a second mixing stage which wavelength converts the data from 1884-nm down to the O-band for detection. The 10-Gb/s data traverses an aggregate record distance of 909 nm in the cascaded wavelength-conversion and unicast stages, with a power penalty of 2.5 dB. This scheme effectively overcomes the lack of commercially-available high-performance sources and receivers at 2 mu m by relying on telecommunication band components along with ultrabroad FWM silicon devices.
Ophir, Noam, Ryan K. W. Lau, Michael Menard, Xiaoliang Zhu, Kishore Padmaraju, Yoshitomo Okawachi, Reza Salem, Michal Lipson, Alexander L. Gaeta, and Keren Bergman. “Wavelength conversion and unicast of 10-Gb/s data spanning up to 700 nm using a silicon nanowaveguide.” Optics Express 20 (2012): 6488-6495. Abstract
We report extremely large probe-idler separation wavelength conversion (545 nm) and unicast (700 nm) of 10-Gb/s data signals using a dispersion-engineered silicon nanowaveguide. Dispersion-engineered phase matching in the device provides a continuous four-wave-mixing efficiency 3-dB bandwidth exceeding 800 nm. We report the first data validation of wavelength conversion (data modulated probe) and unicast (data modulated pump) of 10-Gb/s data with probe-idler separations spanning 60 nm up to 700 nm accompanied with sensitivity gain in a single device. These demonstrations further validate the silicon platform as a highly broadband flexible platform for nonlinear all-optical data manipulation. (C) 2012 Optical Society of America
2011
Lau, Ryan K. W., Michael Menard, Yoshitomo Okawachi, Mark A. Foster, Amy C. Turner-Foster, Reza Salem, Michal Lipson, and Alexander L. Gaeta. “Continuous-wave mid-infrared frequency conversion in silicon nanowaveguides.” Optics Letter 36, no. 7 (2011): 1263-1265. Abstract
We report the first demonstration of cw wavelength conversion from the telecommunications band to the mid-IR (MIR) region via four-wave mixing in silicon nanowaveguides. We measure a parametric bandwidth of 748nm by converting a 1636nm signal to produce a 2384nm idler and show continuously tunable wavelength conversion from 1792 to 2116nm. This report indicates that the advantages of silicon photonics may be leveraged to create devices for a large range of MIR applications that require cw operation. (C) 2011 Optical Society of America
continuous-wave_mid-infrared_frequency_conversion_in_silicon_nanowaveguides.pdf