Publications

2010
Manipatruni, Sasikanth, Kyle Preston, Long Chen, and Michal Lipson. “Ultra-low voltage, ultra-small mode volume silicon microring modulator.” Optics Express 18 (2010): 18235-18242. Abstract
We show GHz modulation in a 2.5 um radius silicon micro-ring, with only 150 mV peak-peak drive voltage and an electro-optic modal volume of only 2 um3. The swing voltage and the micro-ring modulator are the smallest demonstrations so-far in silicon. The presented approach lays the ground work for a new class of high speed low voltage modulators enabling, seamless integration of nanophotonics with low voltage digital CMOS nano-electronics.
ultra-low_voltage_ultra-small_mode_volume_silicon_microring_modulator.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
Biberman, Aleksandr, Benjamin G. Lee, Amy C. Turner-Foster, Mark A. Foster, Michal Lipson, Alexander L. Gaeta, and Keren Bergman. “Wavelength multicasting in silicon photonic nanowires.” Optics Express 18 (2010): 18047-18055. Abstract
We demonstrate a scalable, energy-efficient, and pragmatic method for high-bandwidth wavelength multicasting using FWM in silicon photonic nanowires. We experimentally validate up to a sixteen-way multicast of 40-Gb/s NRZ data using spectral and temporal responses, and evaluate the resulting data integrity degradation using BER measurements and power penalty performance metrics. We further examine the impact of this wavelength multicasting scalability on conversion efficiency. Finally, we experimentally evaluate up to a three-way multicast of 160-Gb/s pulsed-RZ data using spectral and temporal responses, representing the first on-chip wavelength multicasting of pulsed-RZ data.
wavelength_multicasting_in_silicon_photonic_nanowires.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
Broaddus, Daniel H., Mark A. Foster, Imad H. Agha, Jacob T. Robinson, Michal Lipson, and Alexander L. Gaeta. “Silicon-waveguide-coupled high-Q chalcogenide microspheres.” Optics Express 17 (2009): 5998-6003. Abstract
We fabricate high-Q arsenic triselenide glass microspheres through a three-step resistive heating process. We demonstrate quality factors greater than 2x10(6) at 1550 nm and achieve efficient coupling via a novel scheme utilizing index-engineered unclad silicon nanowires. We find that at powers above 1 mW the microspheres exhibit high thermal instability, which limits their application for resonator-enhanced nonlinear optical processes. (C) 2009 Optical Society of America
Dai, Yitang, Xianpei Chen, Yoshitomo Okawachi, Amy C. Turner-Foster, Mark A. Foster, Michal Lipson, Alexander L. Gaeta, and Chris Xu. “1 mu s tunable delay using parametric mixing and optical phase conjugation in Si waveguides: reply.” Optics Express 17 (2009): 16029-16031. Abstract
We address the primary claim in the Comment by N. Alic et al. that our scheme for generating 1-mu s tunable delays via Si-based waveguides in [Opt. Express 17, 7004-7010 (2009)] cannot support wavelength transparency by showing experimentally that the addition of a third conversion stage to reconvert to the input wavelength has minimal effect on the performance of our delay scheme. (C) 2009 Optical Society of America
Dai, Yitang, Xianpei Chen, Yoshitomo Okawachi, Amy C. Turner-Foster, Mark A. Foster, Michal Lipson, Alexander L. Gaeta, and Chris Xu. “1 mu s tunable delay using parametric mixing and optical phase conjugation in Si waveguides.” Optics Express 17 (2009): 7004-7010. Abstract
We demonstrate continuously tunable optical delays as large as 1.1 mu s range for 10 Gb/s NRZ optical signals based on four-wave mixing (FWM) process in silicon waveguide. The large delay range is made possible by a novel wavelength-optimized optical phase conjugation scheme, which allows for tunable dispersion compensation to minimize the residual group-velocity dispersion (GVD) for the entire tuning range. (C) 2009 Optical Society of America
Lira, Hugo L. R., Sasikanth Manipatruni, and Michal Lipson. “Broadband hitless silicon electro-optic switch for on-chip optical networks.” Optics Express 17 (2009): 22271-22280. Abstract
We report on the demonstration of a broadband (60 GHz), spectrally hitless, compact (20 mu m x 40 mu m), fast (7 ns) electro-optical switch. The device is composed of two coupled resonant cavities, each with an independently addressable PIN diode. This topology enables operation of the switch without perturbing adjacent channels in a wavelength division multiplexing (WDM) system. (C) 2009 Optical Society of America
Wiederhecker, Gustavo S., Long Chen, Alexander Gondarenko, and Michal Lipson. “Controlling photonic structures using optical forces.” Nature 462 (2009): 633-U103. Abstract
The use of optical forces to manipulate small objects is well known. Applications include the manipulation of living cells by optical tweezers(1) and optical cooling in atomic physics(2). The miniaturization of optical systems ( to the micro and nanoscale) has resulted in very compliant systems with masses of the order of nanograms, rendering them susceptible to optical forces(3-6). Optical forces have been exploited to demonstrate chaotic quivering of microcavities(7), optical cooling of mechanical modes(8-11), actuation of a tapered-fibre waveguide and excitation of the mechanical modes of silicon nano-beams(12,13). Despite recent progress in this field(14-17), it is challenging to manipulate the optical response of photonic structures using optical forces; this is because of the large forces that are required to induce appreciable changes in the geometry of the structure. Here we implement a resonant structure whose optical response can be efficiently statically controlled using relatively weak attractive and repulsive optical forces. We demonstrate a static mechanical deformation of up to 20 nanometres in a silicon nitride structure, using three milliwatts of continuous optical power. Because of the sensitivity of the optical response to this deformation, such optically induced static displacement introduces resonance shifts spanning 80 times the intrinsic resonance linewidth.
Lee, Benjamin G., Aleksandr Biberman, Amy C. Turner-Foster, Mark A. Foster, Michal Lipson, Alexander L. Gaeta, and Keren Bergman. “Demonstration of Broadband Wavelength Conversion at 40 Gb/s in Silicon Waveguides.” Ieee Photonics Technology Letters 21 (2009): 182-184. Abstract
We present ultra-broadband wavelength conversion in silicon photonic waveguides at a data rate of 40 Gb/s. The dispersion-engineered device demonstrates a conversion bandwidth spanning the entire S-, C-, and L-bands of the ITU grid. Using a continuous-wave C-band pump, an input signal of wavelength 1513.7 nm is up-converted across nearly 50 nm at a data rate of 40 Gb/s, and bit-error-rate measurements are performed on the converted signal.
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
Gondarenko, Alexander, Jacob S. Levy, and Michal Lipson. “High confinement micron-scale silicon nitride high Q ring resonator.” Optics Express 17 (2009): 11366-11370. Abstract
We demonstrate high confinement, low-loss silicon nitride ring resonators with intrinsic quality factor (Q) of 3*10(6) operating in the telecommunication C-band. We measure the scattering and absorption losses to be below 0.065dB/cm and 0.055dB/cm, respectively. (C) 2009 Optical Society of America
Okawachi, Yoshitomo, Reza Salem, Mark A. Foster, Amy C. Turner-Foster, Michal Lipson, and Alexander L. Gaeta. “High-resolution spectroscopy using a frequency magnifier.” Optics Express 17 (2009): 5691-5697. Abstract
We experimentally demonstrate a spectral magnifier using an imaging system with two time-lenses based on four-wave mixing in a Si nanowaveguide. We achieve a magnification factor of 105 with a frequency resolution of 1 GHz. The system offers potential as a tool for single-shot, high resolution spectral measurements. (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.
Salem, Reza, Mark A. Foster, Amy C. Turner-Foster, David F. Geraghty, Michal Lipson, and Alexander L. Gaeta. “High-speed optical sampling using a silicon-chip temporal magnifier.” Optics Express 17 (2009): 4324-4329. Abstract
We demonstrate a single-shot technique for optical sampling based on temporal magnification using a silicon-chip time lens. We demonstrate the largest reported temporal magnification factor yet achieved (>500) and apply this technique to perform 1.3 TS/s single-shot sampling of ultrafast waveforms and to 80-Gb/s performance monitoring. This scheme offers the potential of developing a device that can transform GHz oscilloscopes into instruments capable of measuring signals with THz bandwidths. (C) 2009 Optical Society of America
Chen, Long, Kyle Preston, Sasikanth Manipatruni, and Michal Lipson. “Integrated GHz silicon photonic interconnect with micrometer-scale modulators and detectors.” Optics Express 17 (2009): 15248-15256. Abstract
We report an optical link on silicon using micrometer-scale ring-resonator enhanced silicon modulators and waveguide-integrated germanium photodetectors. We show 3 Gbps operation of the link with 0.5 V modulator voltage swing and 1.0 V detector bias. The total energy consumption for such a link is estimated to be similar to 120 fJ/bit. Such a compact and low power monolithic link is an essential step towards large-scale on-chip optical interconnects for future microprocessors. (C) 2009 Optical Society of America
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
Dong, Po, Long Chen, Qianfan Xu, and Michal Lipson. “On-chip generation of high-intensity short optical pulses using dynamic microcavities.” Optics Letters 34 (2009): 2315-2317. Abstract
We experimentally demonstrate generation of high-intensity short optical pulses obtained by the controlled ultrafast release of the stored energy confined in silicon microcavities. This is achieved using ultrafast tuning of the coupling from a coupled-ring cavity to an external waveguide on time scales shorter than cavity photon lifetime. (C) 2009 Optical Society of America
Manipatruni, Sasikanth, Jacob T. Robinson, and Michal Lipson. “Optical Nonreciprocity in Optomechanical Structures.” Physical Review Letters 102 (2009). Abstract
We demonstrate that optomechanical devices can exhibit nonreciprocal behavior when the dominant light-matter interaction takes place via a linear momentum exchange between light and the mechanical structure. As an example, we propose a microscale optomechanical device that can exhibit a nonreciprocal behavior in a microphotonic platform operating at room temperature. We show that, depending on the direction of the incident light, the device switches between a high and low transparency state with more than a 20 dB extinction ratio.
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.

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