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Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit ...

Rochester Institute of Technology

rochester institute of technology

We experimentally demonstrate ultrafast all-optical modulation using a micrometer-sized silicon photonic integrated device. The device transmission is strongly modulated by photoexcited carriers generated by low-energy pump pulses. A p-i-n junction is integrated on the structure to permit control of the generated carrier lifetimes. When the junction is reverse biased, carriers are extracted from the device in a time as short as 50 ps, permitting greater than 5 Gbit/s modulation of optical signals on a silicon chip.

Ultrafast all-optical modulation on a silicon chip.

We show the existence of direct photonic transitions between modes of a silicon optical microcavity spaced apart in wavelength by over 8 nm. This is achieved by using ultrafast tuning of the refractive index of the cavity over a time interval that is comparable to the inverse of the frequency separation of modes. The demonstrated frequency mixing effect, i.e., the transitions between the modes, would enable on-chip silicon comb sources which can find wide applications in optical sensing, precise spectroscopy, and wavelength-division multiplexing for optical communications and interconnects.

Inducing photonic transitions between discrete modes in a silicon optical microcavity.

We demonstrate a new technique for high resolution imaging of near field profiles in highly confining photonic structures. This technique, Transmission-based Near-field Scanning Optical Microscopy (TraNSOM), measures changes in transmission through a waveguide resulting from near field perturbation by a scanning metallic probe. Using this technique we compare different mode polarizations and measure a transverse optical decay length of lambda/15 in sub-micron Silicon On Insulator (SOI) waveguides. These measurements compare well to theoretical results.

Imaging highly confined modes in sub-micron scale silicon waveguides using Transmission-based Near-field Scanning Optical Microscopy.

We demonstrate a 1x2 all-optical comb switch using a 200 mum diameter silicon ring resonator with a switching time of less than 1 ns. The switch overcomes the small bandwidth of the traditional ring resonator, and works for wavelength division multiplexing applications. The device has a footprint of ~0.04 mm(2) and enables switching of a large number (~40) of wavelength channels spaced by ~0.85 nm.

All-optical compact silicon comb switch.

We experimentally demonstrate a tunable delay element that is inherently insensitive to free-carrier loss and achieves up to 300ps of delay. It is capable of arbitrarily storing and releasing a pulse of light through dynamic tuning of a system of microcavities. The inherent storage time is more than 32 times the duration of the stored pulse.

Controlled storage of light in silicon cavities.

We demonstrate the generation of amplitude-shift-keying (ASK) optical signals using a system of parallel microring resonators. By independently modulating two symmetric microring resonators arranged in a Mach-Zehnder configuration, we realize the generation of three levels. The proposed scheme can be extended to any number of logic levels, which effectively increases the data rate of an optical link using slower modulators. Here, we separately utilize thermo-optic and ultrafast all-optical modulation schemes to generate ASK signals on a silicon photonic chip.

Generation of amplitude-shift-keying optical signals using silicon microring resonators.

In this work, we experimentally demonstrate a novel broadband optical time division multiplexer (OTDM) on a silicon chip. The fabricated devices generate 20 Gb/s and 40 Gb/s signals starting from a 5 Gb/s input signal. The proposed design has a small footprint of 1mm x 1mm. The system is inherently broadband with a bandwidth of over 100nm making it suitable for high-speed optical networks on chip.

Optical time division multiplexer on silicon chip.

We experimentally measure the optical nonlinearities in hydrogenated-amorphous silicon (a-Si:H) waveguides through the transmission of ultra-short pulses. The measured two-photon absorption coefficient beta is 4.1 cm/GW and we obtain a 3.5pi nonlinear phase shift at 4.1 W coupled input power corresponding to a nonlinear refractive index n(2) of 4.210(-13) cm(2)/W. The measured nonlinear coefficient gamma = 2003 (Wm)(-1) is at least 5 times the value in crystalline silicon. The measured free carrier absorption coefficient sigma = 1.910(-16) cm(2) agrees with the values predicted from the Drude-Lorenz model. It is seen that a-Si:H exhibits enhanced nonlinear properties at 1550 nm and is a promising platform for nonlinear silicon photonics.

Optical nonlinearities in hydrogenated-amorphous silicon waveguides.

We demonstrate broadband all-optical modulation in low loss hydrogenated-amorphous silicon (a-Si:H) waveguides. Significant modulation (approximately 3 dB) occurs with a device of only 15 microm without the need for cavity interference effects in stark contrast to an identical crystalline silicon waveguide. We attribute the enhanced modulation to the significantly larger free-carrier absorption effect of a-Si:H, estimated here to be alpha = 1.6310(-16)N cm(-1). In addition, we measured the modulation time to be only tau(c) approximately 400 ps, which is comparable to the recombination rate measured in sub-micron crystalline silicon waveguides, illustrating the strong dominance of surface recombination in similar sized (460 nm x 250 nm) a-Si:H waveguides. Consequently, a-Si:H could serve as a high performance platform for backend integrated CMOS photonics.

Stefan F. Preble

Microsystems Engineering

Rochester Institute of Technology

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Stefan F. Preble

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Microsystems Engineering

Rochester Institute of Technology

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Microsystems Engineering