Many optoelectronic devices embedded in a silicon photonic chip, like photodetectors, modulators, and attenuators, rely on waveguide doping for their operation. However, the doping level of a waveguide is not always reflecting in an equal amount of free carriers available for conduction because of the charges and trap energy states inevitably present at the S i / S i O 2 interface. In a silicon-on-insulator technology with 10 15 c m − 3 p -doped native waveguides, this can lead to a complete depletion of the core from free carriers and to a consequently very high electrical resistance. This Letter experimentally quantifies this effect and shows how the amount of free carriers in a waveguide can be modified and restored to the original doping value with a proper control of the chip substrate potential. A similar capability is also demonstrated by means of a specific metal gate integrated above the waveguide that allows fine control of the conductance with high locality level. This paper highlights the linearity achievable in the conductance modulation that can be exploited in a number of possible applications.

To overcome the problem of low intensity of Brillouin scattered light from thermal phonons, we stimulated the Brillouin scattering by inducing coherent phonons in a glass sample. To develop a completely noncontact measurement method, we induced phonons at 500–800 MHz by a picosecond pulse laser technique and studied how these affect the scattered light. Results show an increase in the intensity of scattered light if the stimulation with the pulse laser is performed. At a distance of 0.75 mm between the pulse laser and the probe laser, we were able to observe an increase of 34 times in the intensity of scattered light. By using a much smaller pulse length of the laser, we can expect stimulation in the GHz range in the future.

On-chip optical power monitors are essential elements to calibrate, stabilize, and reconfigure photonic integrated circuits. Many applications require in-line waveguide detectors, where a trade-off has to be found between large sensitivity and high transparency to the guided light. In this work, we demonstrate a transparent photoconductor integrated on standard low-doped silicon-on-insulator waveguides that reaches a photoconductive gain of more than 106 and an in-line sensitivity as high as −60 dBm. This performance is achieved by compensating the effect of electric charges in the cladding oxide through a bias voltage applied to the chip substrate or locally through a gate electrode on top of the waveguide, allowing one to tune on demand the conductivity of the core to the optimum level.

This paper demonstrates the possibility of automatically stabilizing the working condition of an integrated Silicon Photonics microring modulator with a novel dithering-based control scheme. The proposed feedback strategy leverages a realtime acquisition of the modulator non-linear transfer function (TF) and operates by setting the target locking point to the zero of the TF second derivative, i.e. where the ring slope is maximum. This results in a control algorithm that is both power-independent and calibration-free. The paper shows that the operating point identified in this way has a negligible difference with respect to the optimum working condition of minimum Transmitter Penalty normally targeted and that the employed dithering signal does not affect the modulation quality. The control performances, made possible by an FPGA-based platform ensuring a 30 ms response time, are assessed in a 50 Gbit/s routing scenario, demonstrating effective compensation of wavelength and thermal variations and successful transmission even in demanding environments.

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