Experimental demonstration of reservoir computing on a silicon photonics chip.

In today's age, companies employ machine learning to extract information from large quantities of data. One of those techniques, reservoir computing (RC), is a decade old and has achieved state-of-the-art performance for processing sequential data. Dedicated hardware realizations of RC could enable speed gains and power savings. Here we propose the first integrated passive silicon photonics reservoir. We demonstrate experimentally and through simulations that, thanks to the RC paradigm, this generic chip can be used to perform arbitrary Boolean logic operations with memory as well as 5-bit header recognition up to 12.5 Gbit s(-1), without power consumption in the reservoir. It can also perform isolated spoken digit recognition. Our realization exploits optical phase for computing. It is scalable to larger networks and much higher bitrates, up to speeds >100 Gbit s(-1). These results pave the way for the application of integrated photonic RC for a wide range of applications.

Excitability in optically injected microdisk lasers with phase controlled excitatory and inhibitory response.

We demonstrate class I excitability in optically injected microdisk lasers, and propose a possible optical spiking neuron design. The neuron has a clear threshold and an integrating behavior, leading to an output rate-input rate dependency that is comparable to the characteristic of sigmoidal artificial neurons. We also show that the optical phase of the input pulses has influence on the neuron response, and can be used to create inhibitory, as well as excitatory perturbations.

Cascadable excitability in microrings.

To emulate a spiking neuron, a photonic component needs to be excitable. In this paper, we theoretically simulate and experimentally demonstrate cascadable excitability near a self-pulsation regime in high-Q-factor silicon-on-insulator microrings. For the theoretical study we use Coupled Mode Theory. While neglecting the fast energy and phase dynamics of the cavity light, we can still preserve the most important microring dynamics, by only keeping the temperature difference with the surroundings and the amount of free carriers as dynamical variables of the system. Therefore we can analyse the microring dynamics in a 2D phase portrait. For some wavelengths, when changing the input power, the microring undergoes a subcritical Andronov-Hopf bifurcation at the self-pulsation onset. As a consequence the system shows class II excitability. Experimental single ring excitability and self-pulsation behaviour follows the theoretic predictions. Moreover, simulations and experiments show that this excitation mechanism is cascadable.

A low-power high-speed InP microdisk modulator heterogeneously integrated on a SOI waveguide.

We report on the modulation characteristics of indium phosphide (InP) based microdisks heterogeneously integrated on a silicon-on-insulator (SOI) waveguide. We present static extinction ratios and dynamic operation up to 10 Gb/s. Operation with a bit-error rate below 1 × 10(-9) is demonstrated at 2.5, 5.0 and 10.0 Gb/s and the performance is compared with that of a commercial modulator. Power penalties are analyzed with respect to the pattern length. The power consumption is calculated and compared with state-of-the-art integrated modulator concepts. We demonstrate that InP microdisk modulators combine low-power and low-voltage operation with low footprint and high-speed. Moreover, the devices can be fabricated using the same technology as for lasers, detectors and wavelength converters, making them very attractive for co-integration.

10 Gbit/s all-optical NRZ-OOK to RZ-OOK format conversion in an ultra-small III-V-on-silicon microdisk fabricated in a CMOS pilot line.

We report the demonstration of an all-optical, bias free and error-free (bit-error-rate ~10(-12)), 10 Gbit/s non-return-to-zero (NRZ) to return-to-zero (RZ) data format conversion using a 7.5 µm diameter III-V-on-silicon microdisk resonator. The device is completely processed in a 200 mm CMOS pilot line. The data format conversion is based on the phenomenon of pulse carving of an NRZ optical data stream by an optical clock. The underlying physical effect for the pulse carving is the change in the refractive index caused by the generation of free-carriers in a pump -probe configuration. We believe it to be the first NRZ-to-RZ format convertor built on a hybrid III-V-on-silicon technology platform.

Ultrafast and bias-free all-optical wavelength conversion using III-V-on-silicon technology.

Using a 7.5 µm diameter disk fabricated with III-V-on-silicon fabrication technology, we demonstrate bias-free all-optical wavelength conversion for non-return-to-zero on-off keyed pseudorandom bit sequence (PRBS) data at the speed of 10 Gbits/s with an extinction ratio of more than 12 dB. The working principle of such a wavelength converter is based on free-carrier-induced refractive index modulation in a pump-probe configuration. We believe it to be the first bias-free on-chip demonstration of all-optical wavelength conversion using PRBS data. All-optical gating measurements in the pump-probe configuration with the same device have revealed that it is possible to achieve wavelength conversion beyond 20 Gbits/s.