Measurements of a Silicon Photonic ROADM (Project Report CIAN2-3-Y3)

A multi-university partnership led by UCSD collaborated with Sandia National Labs in an NSF-funded silicon photonics multi-project wafer (MPW) project. This is a report of the ROADM +VOA (reconfigurable optical add drop multiplexer + variable optical attenuator) device made using silicon photonics, including passive and doped silicon waveguides and metalization.

Low-Noise Mixed-Signal Electronics for Closed-Loop Control of Complex Photonic Circuits

An increasing research effort is being carried out to profit from the advantages of photonics not only in long-range telecommunications but also at short distances, to implement board-to-board or chip-to-chip interconnections. In this context, Silicon Photonics emerged as a promising technology, allowing to integrate optical devices in a small silicon chip. However, the integration density made possible by Silicon Photonics revealed the difficulty of operating complex optical architectures in an open-loop way, due to their high sensitivity to fabrication parameters and temperature variations. In this chapter, a low-noise mixed-signal electronic platform implementing feedback control of complex optical architectures is presented. The system exploits the ContactLess Integrated Photonic Probe, a non-invasive detector that senses light in silicon waveguides by measuring their electrical conductance. The CLIPP readout resolution has been maximized thanks to the design of a low-noise multichannel ASIC, achieving an accuracy better than −35 dBm in light monitoring. The feedback loop to stabilize the behaviour of photonic circuits is then closed in the digital domain by a custom mixed-signal electronic platform. Experimental demonstrations of optical communications at high data-rate confirm the effectiveness of the proposed approach.

Design Improvements of a Silicon Photonic ROADM (Project Report CIAN2-1-Y4)

This was a project “Silicon Photonics Device Manufacturing and Test” under the re-organized Thrust 2 “Subsystem Integration and Silicon Nanophotonics” of an NSF-funded Center. This is a report of the 2nd generation ROADM (reconfigurable optical add drop multiplexer) device made using silicon photonics, including passive and doped silicon waveguides and metalization.

Nonlinear loss characterization of continuous wave guiding in silicon wire waveguides

Accurate propagation loss characterization of silicon waveguides is increasingly demanded for silicon-photonics-(Si-Ph) applications with high-power continuous-wave-(CW) light sources. We report on nonlinear loss parameters of silicon wire waveguides for 1.31-μm-wavelength CW light extracted from transmission data measured for different lengths and polarizations. Such parameters were, so far, unavailable, although they are required for accurately modeling Si-Ph optical circuits. More-than-ten-times enhancement of two-photon absorption from prior results for short pulse light was observed at power densities ranging up to 4.7×1011 W/m2 while free carrier absorption was suppressed. We estimate the nonlinear loss of the waveguide using the parameter values obtained

Tailorable Brillouin Light Scattering in a Lithium Niobate Waveguide

Stimulated Brillouin scattering (SBS) lasers based on silicon waveguides with large SBS gain have been widely used in frequency tunable laser emissions, mode-locked pulse lasers, low-noise oscillators, optical gyroscopes and other fields. However, among SBS lasers, the realization of Brillouin laser output often requires a longer waveguide length, which not only increases waveguide loss but also increase the size of the device. As a new medium, lithium niobate has been fabricated into a new type of hybrid structure. Meanwhile, the width of a suspended waveguide is adjusted to tune the phonon frequency of an SBS laser based on lithium niobate substrate. Simulation results show that the tunable forward SBS effect is realized in a lithium niobate-suspended optical waveguide, showing a larger forward stimulated Brillouin scattering gain of 0.31 W−1m−1. The tunable phonon frequency ranges from 1 to 15 GHz. Therefore, utilizing the photon–phonon conversion effect, the waveguide system with LiNbO3 will pave a new way forward with better integration.

A review of silicon subwavelength gratings: building break-through devices with anisotropic metamaterials

Silicon photonics is playing a key role in areas as diverse as high-speed optical communications, neural networks, supercomputing, quantum photonics, and sensing, which demand the development of highly efficient and compact light-processing devices. The lithographic segmentation of silicon waveguides at the subwavelength scale enables the synthesis of artificial materials that significantly expand the design space in silicon photonics. The optical properties of these metamaterials can be controlled by a judicious design of the subwavelength grating geometry, enhancing the performance of nanostructured devices without jeopardizing ease of fabrication and dense integration. Recently, the anisotropic nature of subwavelength gratings has begun to be exploited, yielding unprecedented capabilities and performance such as ultrabroadband behavior, engineered modal confinement, and sophisticated polarization management. Here we provide a comprehensive review of the field of subwavelength metamaterials and their applications in silicon photonics. We first provide an in-depth analysis of how the subwavelength geometry synthesizes the metamaterial and give insight into how properties like refractive index or anisotropy can be tailored. The latest applications are then reviewed in detail, with a clear focus on how subwavelength structures improve device performance. Finally, we illustrate the design of two ground-breaking devices in more detail and discuss the prospects of subwavelength gratings as a tool for the advancement of silicon photonics.