Keith G. Petrillo

Ultralow-power all-optical processing of high-speed data signals in deposited silicon waveguides

Utilizing a 6-mm-long hydrogenated amorphous silicon nanowaveguide, we demonstrate error-free (BER < 10(-9)) 160-to-10 Gb/s OTDM demultiplexing using ultralow switching peak powers of 50 mW. This material is deposited at low temperatures enabling a path toward multilayer integration and therefore massive scaling of the number of devices in a single photonic chip.

Full 160-Gb/s OTDM to 16x10-Gb/s WDM conversion with a single nonlinear interaction.

We experimentally demonstrate full simultaneous error-free demultiplexing of a 160-Gb/s OTDM data stream to 16x10-Gb/s WDM channels in a single nonlinear optical device. A temporal Fourier processor based upon a four-wave mixing (FWM) time lens is used to perform the demultiplexing operation. The FWM pump pulses are chirped such that they temporally overlap to allow for continuous operation; a necessary feature for full demultiplexing. We identify the fundamental challenges of operating in this continuous regime and characterize their impact on the system performance. We determine the main performance impairments to be crosstalk from adjacent WDM channels and crosstalk arising from non-degenerate FWM amongst the OTDM signal and the temporally overlapping pump pulses.

Scalable ultrahigh-speed optical transmultiplexer using a time lens.

We present a scalable approach to optical time division multiplexing using an all-optical transmultiplexer incorporating a time lens. With simply a single nonlinear device we numerically demonstrate direct conversion from time-division multiplexing (TDM) to wavelength division multiplexing (WDM) with an industry standard 100-GHz channel spacing. Data rates at 1.28 Tb/s are realized in simulation. Additionally, various pump shapes are investigated to minimize distortions and reverse operation of the device (WDM to TDM conversion) is shown.

Synchronization of clocks through 12 km of strongly turbulent air over a city

We demonstrate real-time, femtosecond-level clock synchronization across a low-lying, strongly turbulent, 12-km horizontal air path by optical two-way time transfer. For this long horizontal free-space path, the integrated turbulence extends well into the strong turbulence regime corresponding to multiple scattering with a Rytov variance up to 7 and with the number of signal interruptions exceeding 100 per second. Nevertheless, optical two-way time transfer is used to synchronize a remote clock to a master clock with femtosecond-level agreement and with a relative time deviation dropping as low as a few hundred attoseconds. Synchronization is shown for a remote clock based on either an optical or microwave oscillator and using either tip-tilt or adaptive-optics free-space optical terminals. The performance is unaltered from optical two-way time transfer in weak turbulence across short links. These results confirm that the two-way reciprocity of the free-space time-of-flight is maintained both under strong turbulence and with the use of adaptive optics. The demonstrated robustness of optical two-way time transfer against strong turbulence and its compatibility with adaptive optics is encouraging for future femtosecond clock synchronization over very long distance ground-to-air free-space paths.

Highly sensitive ultrafast pulse characterization using hydrogenated amorphous silicon waveguides

We experimentally demonstrate frequency resolved optical gating (FROG) via four-wave mixing (FWM) in ultrahigh nonlinearity hydrogenated amorphous silicon waveguides. We demonstrate FROG characterization using a FWM architecture that mimics second harmonic generation (SHG) FROG for pulsewidths as low as 360 fs. Additionally, we demonstrate for the first time a FWM architecture analogous to third harmonic generation (THG) FROG and validate its ability to overcome the direction of time ambiguity of the SHG-like architecture. Both architectures allow for sensitivities suitable for future telecommunications signals.

Highly-sensitive ultrafast pulse characterization utilizing four-wave mixing in an amorphous silicon nanowaveguide

We demonstrate frequency-resolved optical gating using four-wave mixing in a hydrogenated amorphous silicon nanowaveguide. The ultrahigh nonlinearity and the wide conversion bandwidth of this device allow characterization of sub-ps pulses with high sensitivity.

Ultralow-power 160-to-10Gb/s optical demultiplexing using four-wave mixing in deposited silicon waveguides

Utilizing a 6-mm-long hydrogenated amorphous silicon nanowaveguide, we demonstrate error-free (BER <; 10-9) 160-to-10 Gb/s OTDM demultiplexing using ultralow switching peak powers of 50 mW. This material is deposited at low temperatures enabling a path toward multilayer integration and therefore massive scaling of the number of devices in a single photonic chip.

Simulation and experimental demonstration of coherent OCDMA using spectral line pairing and heterodyne detection

A fully coherent optical code-division multiple access (OCDMA) scheme that combines spectral phase encoding (SPE) and spectral line pairing to generate signals through heterodyne decoding is proposed. A simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). A 16 user 100% load system transmitting at 40 Gbits is simulated, and a 4 user 50% load system transmitting at 4.25 Gbit/s is experimentally demonstrated for the first time.

Experimental demonstration of coherent OCDMA using heterodyne detection

We present the first experimental demonstration of a practical, fully coherent, optical code division multiple access (OCDMA) scheme that can fully suppress multiple access interference (MAI) and speckle noise without phase locking or thresholding and gating. The scheme is sourced from an optical comb generator and uses spectral phase encoding and a heterodyne receiver with balanced detection. Here we present results for a four-user configuration at 50% load. At 4.5 Gbits/s per user, the system achieves a signal to MAI ratio of 648 at a bit error rate of 10(-7).

Bit-error rate improvement through all-optical signal regeneration in deposited silicon waveguides

We demonstrate all-optical signal regeneration using a Mamyshev design in a hydrogenated amorphous silicon (a-Si:H) waveguide. Bit-error-rate improvement of 2 dB is achieved with 5.2 W peak power at telecommunication data rates (10 GHz).