No abstract

Wavelength-dependent polarization state of light carries crucial information about light-matter interactions. However, its measurement is limited to bulky, energy-consuming devices, which prohibits many modern, portable applications. Here, we propose and demonstrate a chip-scale spectropolarimeter implemented using a CMOS-compatible silicon photonics technology. Four compact Vernier microresonator spectrometers are monolithically integrated with a broadband polarimeter consisting of a 2D nanophotonic antenna and a polarimetric circuit to achieve full-Stokes spectropolarimetric analysis. The proposed device offers a solid-state spectropolarimetry solution with a small footprint of 1 × 0.6 mm 2 and low power consumption of 360 mW. Full-Stokes spectral detection across a broad spectral range of 50 nm with a resolution of 1 nm is demonstrated in characterizing a material possessing structural chirality. The proposed device may enable a broader application of spectropolarimetry in the fields ranging from biomedical diagnostics and chemical analysis to observational astronomy.

Spatial multiplexing using orbital angular momentum (OAM) modes is an efficient means of scaling up the capacity of fiber-optic communications systems; integrated multiplexers are crucial enablers of this approach. OAM modes are circularly polarized when propagating in a fiber, however, OAM generators previously demonstrated in silicon photonics use locally linearly polarized emitters. Coupling from multiplexers to fibers in those solutions results in extra loss and complexity. Moreover, many of those solutions are based on resonator structures with strong wavelength dependence, and are thus incompatible with wavelength-division multiplexing (WDM). We experimentally demonstrate on-chip generation and multiplexing of OAM modes using an array of circularly polarized 2D antennas with wide wavelength coverage. The proposed device was implemented on the standard 220-nm silicon-on-insulator platform. Optical vortex beams with OAM orders ranging from -3 to +3 in both left and right circular polarization states were generated from the same aperture across a wavelength range of 1540 nm to 1557 nm. This device could serve as a multiplexer or demultiplexer for up to 12 information bearing channels coupling into an OAM fiber, and is compatible with WDM multiplexing as well.

No abstract

As 5G communication matures, the requirement for advanced radio access networks (RAN) drives the evolution of optical access networks to support these needs. Basic RAN functions, mobile front-haul to the backbone and interconnected front-end remote radio units, must support and enable data rate surges, low-latency applications, RF coordination, etc. Wavelength division multiplexed optical access networks (WDM-OANs) provide sufficient network capacity to support the addition of RAN services, especially in unused portions of WDM. We propose and demonstrate a method for RAN overlay in WDM-OANs that employ distributed carriers. In such systems, the carrier is modulated at the central office for direct-detected downstream digital data services; later the same carrier is remodulated for the uplink. We propose the use of silicon photonics to intercept the downstream and add 5G signals. We examine the distributed-carrier power budget issues in this overlay scenario. The carrier power must be harvested for direct detection of both digital and RoF services, and yet hold in reserve sufficient power for the uplink remodulation of all services. We concentrate on the silicon photonics subsystem at the remote node to add RoF signals. We demonstrate the overlay with a fabricated chip and study strategic allocations of carrier power at the optical network units housing the radio units to support the overlay. After the successful drop and reception of both conventional WDM-OAN and the newly overlaid RoF signals, we demonstrate sufficient carrier power margin for the upstream remodulation.