Publications

2015
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.
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
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.
cardenas_etched_facet_2014.pdf
Luo, Lian-Wee, Noam Ophir, Christine P. Chen, Lucas H. Gabrielli, Carl B. Poitras, Keren Bergmen, and Michal Lipson. “WDM-compatible mode-division multiplexing on a silicon chip.” Nature Communications 5 (2014). Publisher's Version Abstract
Significant effort in optical-fibre research has been put in recent years into realizing mode-division multiplexing (MDM) in conjunction with wavelength-division multiplexing (WDM) to enable further scaling of the communication bandwidth per fibre. In contrast, almost all integrated photonics operate exclusively in the single-mode regime. MDM is rarely considered for integrated photonics because of the difficulty in coupling selectively to high-order modes, which usually results in high inter-modal crosstalk. Here we show the first microring-based demonstration of on-chip WDM-compatible mode-division multiplexing with low modal crosstalk and loss. Our approach can potentially increase the aggregate data rate by many times for on-chip ultrahigh bandwidth communications.
luo_wdm_mdm_natcomm_2014.pdf
2013
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
Luke, Kevin, Avik Dutt, Carl B. Poitras, and Michal Lipson. “Overcoming Si3N4 film stress limitations for high quality factor ring resonators.” Optics Express 21 (2013): 22829-22833. Abstract
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 1550 nm wavelength range. (c) 2013 Optical Society of America
2012
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
Guha, Biswajeet, Clayton Otey, Carl B. Poitras, Shanhui Fan, and Michal Lipson. “Near-Field Radiative Cooling of Nanostructures.” Nano Letters 12 (2012): 4546-4550. Abstract
We measure near field radiative cooling of a thermally isolated nanostructure up to a few degrees and show that in principle this process can efficiently cool down localized hotspots by tens of degrees at submicrometer gaps. This process of cooling is achieved without any physical contact, in contrast to heat transfer through conduction, thus enabling novel cooling capabilities. We show that the measured trend of radiative cooling agrees well theoretical predictions and is limited mainly by the geometry of the probe used here as well as the minimum separation that could be achieved in our setup. These results also pave the way for realizing other new effects based on resonant heat transfer, like thermal rectification and negative thermal conductance.
2011
Lira, Hugo L. R., Carl B. Poitras, and Michal Lipson. “CMOS compatible reconfigurable filter for high bandwidth non-blocking operation.” Optics Express 19, no. 21 (2011): 20115-20121. Abstract
We design, fabricate and characterize a CMOS-compatible, Mach-Zehnder-coupled, second-order-microring-resonator filter with large Free Spectral Range and demonstrate non-blocking thermo-optical filter reconfiguration. The device consists of 10-mu m radius silicon microring resonators, with an FSR equivalent to that of a structure consisting of 5-mu m radii microrings. The structure is reconfigurable over an 8.5 nm range without blocking other channels in the network. (C) 2011 Optical Society of America
cmos_compatible_reconfigurable_filter_for_high_bandwidth_non-blocking_operation.pdf
2010
Spadoti, Danilo H., Lucas H. Gabrielli, Carl B. Poitras, and Michal Lipson. “Focusing light in a curved-space.” Optics Express 18 (2010): 3181-3186. Abstract
We use transformation optics to demonstrate 2D silicon nanolenses, with wavelength-independent focal point. The lenses are designed and fabricated with dimensions ranging from 5.0 um x 5.0 um to 20 um x 20 um. According to numerical simulations the lenses are expected to focus light over a broad wavelength range, from 1.30 um to 1.60 um. Experimental results are presented from 1.52 um to 1.61 um.
focusing_light_in_a_curved-space.pdf
Luo, Lian-Wee, Salah Ibrahim, Arthur Nitkowski, Zhi Ding, Carl B. Poitras, S. J. Ben Yoo, and Michal Lipson. “High bandwidth on-chip silicon photonic interleaver.” Optics Express 18 (2010): 23079-23087. Abstract
We demonstrate a 120 GHz 3-dB bandwidth on-chip silicon photonic interleaver with a flat passband over a broad spectral range of 70 nm. The structure of the interleaver is based on an asymmetric Mach-Zehnder interferometer (MZI) with 3 ring resonators coupled to the arms of the MZI. The transmission spectra of this device depict a rapid roll-off on the band edges, where the 20-dB bandwidth is measured to be 142 GHz. This device is optimized for operation in the C-band with a channel crosstalk as low as -20 dB. The device also has full reconfiguration capability to compensate for fabrication imperfections.
high_bandwidth_on-chip_silicon_photonic_interleaver.pdf
Turner-Foster, Amy C., Mark A. Foster, Jacob S. Levy, Carl B. Poitras, Reza Salem, Alexander L. Gaeta, and Michal Lipson. “Ultrashort free-carrier lifetime in low-loss silicon nanowaveguides.” Optics Express 18 (2010): 3582-3591. Abstract
We demonstrate reduction of the free-carrier lifetime in a silicon nanowaveguide from 3 ns to 12.2 ps by applying a reverse bias across an integrated p-i-n diode. This observation represents the shortest free-carrier lifetime demonstrated to date in silicon waveguides. Importantly, the presence of the p-i-n structure does not measurably increase the propagation loss of the waveguide. We derive a figure of merit demonstrating equal dependency of the nonlinear phase shift on free-carrier lifetime and linear propagation loss.
ultrashort_free-carrier_lifetime_in_low-loss_silicon_nanowaveguides.pdf
Cardenas, Jaime, Mark A. Foster, Nicolas Sherwood-Droz, Carl B. Poitras, Hugo L. R. Lira, Beibei Zhang, Alexander L. Gaeta, Jacob B. Khurgin, Paul Morton, and Michal Lipson. “Wide-bandwidth continuously tunable optical delay line using silicon microring resonators.” Optics Express 18 (2010): 26525-26534. Abstract
We demonstrate a distortion free tunable optical delay as long as 135 ps with a 10 GHz bandwidth using thermally tuned silicon microring resonators in the novel balanced configuration. The device is simple, easy to control and compact measuring only 30 mu m wide by 250 mu m long.
wide-bandwidth_continuously_tunable_optical.pdf
2009
Preston, Kyle, Sasikanth Manipatruni, Alexander Gondarenko, Carl B. Poitras, and Michal Lipson. “Deposited silicon high-speed integrated electro-optic modulator.” Optics Express 17 (2009): 5118-5124. Abstract
We demonstrate a micrometer-scale electro-optic modulator operating at 2.5 Gbps and 10 dB extinction ratio that is fabricated entirely from deposited silicon. The polycrystalline silicon material exhibits properties that simultaneously enable high quality factor optical resonators and sub-nanosecond electrical carrier injection. We use an embedded p(+)n(-)n(+) diode to achieve optical modulation using the free carrier plasma dispersion effect. Active optical devices in a deposited microelectronic material can break the dependence on the traditional single layer silicon-on-insulator platform and help lead to monolithic large-scale integration of photonic networks on a microprocessor chip. (C) 2009 Optical Society of America
Lee, Benjamin G., Aleksandr Biberman, Nicolas Sherwood-Droz, Carl B. Poitras, Michal Lipson, and Keren Bergman. “High-Speed 2 x 2 Switch for Multiwavelength Silicon-Photonic Networks-On-Chip.” Journal of Lightwave Technology 27 (2009): 2900-2907. Abstract
We report the fabrication and experimental verification of a multiwavelength high-speed 2 x 2 silicon photonic switch for ultrahigh-bandwidth message routing in optical on-chip networks. The structure employs only two microring resonators in order to implement the bar and cross states of the switch. These states are toggled using an optical pump at 1.5-mu m wavelengths in-plane with the waveguide devices, though electronic, rather than optical, control schemes are envisioned for more complex systems built from these devices. Experiments characterize bit-error-rate performance in the bar and cross states during static and dynamic operation. The all-optical demonstration exhibits the ability of the switch to implement ultra-short transition times (<2ns), high extinction ratios (>10 dB), and lowpower penalties (dB) at a data rate of 10 Gb/s. Further performance improvements are expected by using electronic carrier injection via p-i-n diodes surrounding the ring waveguides. The 2 x 2 switching functionality facilitates the design of more complex routing structures, allowing the implementation of high-functionality integrated optical networ ks.
Cardenas, Jaime, Carl B. Poitras, Jacob T. Robinson, Kyle Preston, Long Chen, and Michal Lipson. “Low loss etchless silicon photonic waveguides.” Optics Express 17 (2009): 4752-4757. Abstract
We demonstrate low loss silicon waveguides fabricated without any silicon etching. We define the waveguides by selective oxidation which produces ultra-smooth sidewalls with width variations of 0.3 nm. The waveguides have a propagation loss of 0.3 dB/cm at 1.55 mu m. The waveguide geometry enables low bending loss of approximately 0.007 dB/bend for a 90 degrees bend with a 50 mu m bending radius.(C) 2009 Optical Society of America
Gabrielli, Lucas H., Jaime Cardenas, Carl B. Poitras, and Michal Lipson. “Silicon nanostructure cloak operating at optical frequencies.” Nature Photonics 3 (2009): 461-463. Abstract
The ability to render objects invisible using a cloak (such that they are not detectable by an external observer) has long been a tantalizing goal(1-6). Here, we demonstrate a cloak operating in the near infrared at a wavelength of 1,550 nm. The cloak conceals a deformation on a flat reflecting surface, under which an object can be hidden. The device has an area of 225 mu m(2) and hides a region of 1.6 mu m(2). It is composed of nanometre-size silicon structures with spatially varying densities across the cloak. The density variation is defined using transformation optics to define the effective index distribution of the cloak.
2008
Manipatruni, Sasikanth, Carl B. Poitras, Qianfan Xu, and Michal Lipson. “High-speed electro-optic control of the optical quality factor of a silicon microcavity.” Optics Letters 33 (2008): 1644-1646. Abstract
We demonstrate electro-optic ultrafast control of the optical quality factor of an on-chip silicon microcavity. The micrometer-sized cavity is formed by light confinement between two microring resonators acting as frequency selective mirrors. The ring resonators are integrated into p-i-n junctions enabling ultrafast injection and extraction of carriers. We show tuning of the cavity quality factor from 20,000 to 6,000 in under 100 ps. We demonstrate both high-Q to low-Q and low-Q to high-Q transitions. (c) 2008 Optical Society of America.

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