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.
We demonstrate asynchronous, single-shot characterization of an ultrafast, high-repetition-rate pulse source using a time-lens-based temporal magnifier. We measure a 225 GHz repetition-rate pulse train from a microresonator-based frequency comb. In addition, we show that such a system can be used as a frequency compressor for real-time, high-speed RF spectral characterization. (C) 2012 Optical Society of America
We investigate optical crosstalk on a signal in a silicon nanowaveguide due to the presence of another signal by direct radio frequency crosstalk level measurements in a pump-probe configuration and by bit-error-rate-based characterization. We quantify this degradation as a function of the modulation frequency and power of the auxiliary signal. Our results indicate that two-photon and free-carrier absorption are primary facilitators of crosstalk in silicon nanowaveguides.
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.
We demonstrate power insensitive silicon microring resonators without the need for active feedback control. The passive control of the resonance is achieved by utilizing the compensation of two counteracting processes, free carrier dispersion blueshift and thermo-optic redshift. In the fabricated devices, the resonant wavelength shifts less than one resonance linewidth for dropped power up to 335 mu W, more than fivefold improvement in cavity energy handling capability compared to regular microrings. (C) 2012 Optical Society of America
We demonstrate electrically driven nonreciprocity on a silicon chip. By achieving an indirect interband photonic transition, we show that the transmission coefficients between two single-mode waveguides become dependent on the propagation directions only in the presence of the electrical drive. Our structure is characterized by a nonsymmetric scattering matrix identical to a linear magneto-optical device.
We demonstrate a stable complementary metal-oxide-semiconductor-compatible on-chip multiple-wavelength source by filtering and modulating individual comb lines from a parametric optical frequency comb generated in a silicon nitride microring resonator. We show comb operation in a stable lownoise state. Bit-error rate measurements demonstrate negligible power penalty from six independent frequency comb lines when compared with a tunable diode laser baseline. Open eye diagrams confirm the fidelity of the 10 Gb/s data transmitted at the comb frequencies and the suitability of this device for use as a fully integrated silicon-based wavelength-division-multiplexing source.
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
We demonstrate a new class of passively temperature stabilized resonant silicon electro-optic modulators. The modulators consist of a ring resonator coupled to a Mach-Zehnder interferometer with tailored thermal properties. We demonstrate 2 GHz continuous modulation over a temperature range of 35 degrees C and describe the scalability and design rules for such a device. (C) 2012 Optical Society of America
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.
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
Current optical communication systems rely almost exclusively on multimode fibres for short- and medium-haul transmissions, and are now expanding into the long-haul arena. Ultra-high bandwidth applications are the main drive for this expansion, based on the ability to spatially multiplex data channels in multimode systems. Integrated photonics, on the other hand, although largely responsible for today's telecommunications, continues to operate almost strictly in the single-mode regime. This is because multimode waveguides cannot be compactly routed on-chip without significant inter-mode coupling, which impairs their data rate and prevents the use of modal multiplexing. Here we propose a platform for on-chip multimode devices with minimal inter-mode coupling, opening up the possibilities for integrated multimode optics. Our work combines a novel theoretical approach-large-scale inverse design of transformation optics to maximize performance within fabrication constraints-with unique grayscale-lithography fabrication of an exemplary device: a low-crosstalk multimode waveguide bend.
We demonstrate a low-cost colorless optical network unit (ONU) utilizing silicon photonic components for wavelength division multiplexed passive-optical-networks. At the ONU, a waveguide-coupled microring works as a demultiplexer for separating the downstream signal from the centrally distributed continuous-wave (CW) light. The 10-Gb/s downstream signal is received using a waveguide-integrated germanium photodetector while the CW light is further modulated at 5 Gb/s using a silicon microring modulator for upstream signal generation. Error-free transmission over 25-km single mode fiber is achieved with 0.2- and 0.4-dB power penalties for the downstream and upstream signals, respectively. Complementary metal-oxide semiconductor-compatible silicon photonic technology offers the potential for monolithic integration and mass production.
We experimentally demonstrate selective control of the Q and transmission of an individual resonance of an optical microcavity by optically controlling its intracavity loss via inverse Raman scattering. A strongly overcoupled resonance is brought into critical coupling with continuous tuning of the on-resonance transmission by >9 dB and reduction of the intrinsic Q factor by more than a factor of five. Adjacent resonances experience minimal disturbance and can be selectively controlled by tuning the control beam to the appropriate control resonance. These dynamics are analogous to Zeno effects observed in decoherence-driven atomic ensembles and two-level systems.
A vital element in integrated optofluidics is dynamic tuning and precise control of photonic devices, especially when employing electronic techniques which are challenging to utilize in an aqueous environment. We overcome this challenge by introducing a new platform in which the photonic device is controlled using electro-optical phase tuning. The phase tuning is generated by the thermo-optic effect using an on-chip electric microheater located outside the fluidic channel, and is transmitted to the optofluidic device through optical waveguides. The microheater is compact, high-speed (> 18 kHz), and consumes low power (similar to mW). We demonstrate dynamic optical trapping control of nanoparticles by an optofluidic resonator. This novel electro-optofluidic platform allows the realization of high throughput optofluidic devices with switching, tuning, and reconfiguration capability, and promises new directions in optofluidics. (C) 2012 Optical Society of America
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
We demonstrate the generation of error-free binary-phase-shift-keyed (BPSK) data at 5 Gb/s using a silicon microring modulator. The microring-modulated BPSK signal is propagated at fiber lengths up to 80 km, maintaining error-free performance, while demonstrating resilience to chromatic dispersion. Bit-error-rate measurements and eye diagrams show near equivalent performance of a microring-based BPSK modulator as compared to commercial LiNbO3 phase modulators. (C) 2012 Optical Society of America
We describe and demonstrate the use of a feedback control system to thermally stabilize a silicon microring modulator subjected to a thermally volatile environment. Furthermore, we establish power monitoring as an effective and appropriate mechanism to infer the temperature drift of a microring modulator. Our demonstration shows that a high-performance silicon microring-based device, normally inoperable in thermally volatile environments, can maintain error-free performance when a feedback control system is implemented. (C) 2012 Optical Society of America
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
We demonstrate simultaneous switching of wavelength-division-multiplexed (WDM) data consisting of four 44-Gb/s channels (176 Gb/s total) through an electro-optically active second-order microring switch with a 0.7-ns rise and a 3.4-ns fall time. The higher order microring device allows fast simultaneous switching of multiple high data rate WDM channels. We verify the correct active switching operation and low resultant power penalties on both switch output ports. The ability to switch multiple high data rate channels simultaneously at high speed with low power consumption makes higher order ring switches attractive components for silicon photonic switching fabrics.