Design and Characterization of SiN-based integrated optical components for Wavelength Division Multiplexing

To follow the trend of the data traffic and to limit the size of the hyperscale data centers, communication solutions offering small footprint, low cost and low power consumption are needed. Optical interconnects used in data centers are mostly short reach (approximately 100 m) basedon GaAs-based 850 nm vertical-cavity surface emitting lasers (VCSELs) and OM4 multimode fibers (MMF). However, with 1 km-long optical links, the use of VCSEL-MMF at 850 nm becomes challenging at high data rates (Tb/s) due to large modal dispersion and high propagation loss. Therefore, other cost-effective methods are needed to compensate these limits. Single mode GaAs-based VCSELs have been demonstrated at 1060 nm of wavelength, where the chromatic dispersion is lower, for optical links ranging between 300 m and 10 km. This solution could be a better alternative than InP-based distributed feedback laser sources at 1310 nm in terms of cost and energy dissipation. As the modulation bandwidth of GaAs-based single mode VCSELs is limited to around 30 GHz, reaching the capacity target then requires a wavelength division multiplexing scheme with parallel single-core fibers (SCFs) or even multi-core fibers (MCFs).In this thesis we discuss different types of demultiplexers at 1060 nm of wavelength. The proposed designed demultiplexers are arrayed waveguide gratings (AWGs) and cascaded Mach-Zehnder interferometers (MZIs). These two technologies are compared in terms of transmission,bandwidth, crosstalk, and footprint with the number of output channels. Grating couplers at 1060 and 850 nm for on-chip coupling are also studied. The goal is to couple the light coming from a single mode fiber or a VCSEL with the lowest possible loss and back reflection

Design of the Novel Wavelength Triplexer Using Multiple Polymer Microring Resonators

We report about new design of wavelength triplexer using multiple polymer optical microring resonators. Triplexer consists of two downstream wavelength channels operating at 1490 ± 10 nm, 1555 ± 10 nm and one upstream wavelength channel operating at 1310 ± 50 nm. The parallel coupled double ring resonator was used for separation of the optical signal band at 1555 nm and filtered out signal bands 1310 nm and 1490 nm. The serially coupled triple optical microring resonator was used for separation of the optical signal band at 1490 nm and filtered out signal bands 1310 nm and 1555 nm. The design was done by using FullWAVETM software by the finite-difference time-domain method. Simulation showed that optical losses for band at 1555 nm were -3 dB and crosstalk between signal bands 1555 nm and 1490 nm was 24 dB. Calculated optical losses for channel 1490 nm were less than -2.5 dB and signal bands at 1555 nm was filtered out with less than 18 dB loss. The bands at 1310 nm were fully filtered out from both downstream wavelength channels operating at bands 1490 nm and 1555 nm

Compact wavelength de-multiplexer design using slow light regime of photonic crystal waveguides

Cataloged from PDF version of article.We demonstrate the operation of a compact wavelength de-multiplexer using cascaded single-mode photonic crystal waveguides utilizing the slow light regime. By altering the dielectric filling factors of each waveguide segment, we numerically and experimentally show that different frequencies are separated at different locations along the waveguide. In other words, the beams of different wavelengths are spatially dropped along the transverse to the propagation direction. We numerically verified the spatial shifts of certain wavelengths by using the two-dimensional finite-difference time-domain method. The presented design can be extended to de-multiplex more wavelengths by concatenating additional photonic crystal waveguides with different filling factors. (C) 2011 Optical Society of Americ

Interleavers

The chapter describes principles, analysis, design, properties, and implementations of optical frequency (or wavelength) interleavers. The emphasis is on finite impulse response devices based on cascaded Mach-Zehnder-type filter elements with carefully designed coupling ratios, the so-called resonant couplers. Another important class that is discussed is the infinite impulse response type, based on e.g. Fabry-Perot, Gires-Tournois, or ring resonators

Single-Order Transmission Diffraction Gratings based on Dispersion Engineered All-dielectric Metasurfaces

A single-order transmission diffraction grating based on dispersion engineered all-dielectric metasurfaces is proposed and its wavelength discriminating properties have been theoretically described and confirmed using numerical simulations. The metasurface is designed using a 2D array of all-dielectric resonators, which emulates a Huygens source configuration to achieve a perfect match to free-space in broad bandwidth. Using a holey dielectric nanodisk structure as the unit cell, the resonant wavelength is tapered across the metasurface to engineer the wavelength dependent spatial phase gradient, to emulate a dispersive prism. Consequently, different wavelengths are steered towards different directions and thus are discriminated on the output image plane. Due to subwavelength periodicities involved, the wavelength discrimination is achieved directly in the zeroth diffraction order of the device, unlike conventional diffraction gratings, thereby providing a high efficiency wavelength discriminating device.Comment: 5 pages, 5 figure

Wafer-level processing of ultralow-loss Si3N4

Photonic integrated circuits (PICs) are devices fabricated on a planar wafer that allow light generation, processing, and detection. Photonic integration brings important advantages for scaling up the complexity and functionality of photonic systems and facilitates their mass deployment in areas where large volumes and compact solutions are needed, e.g., optical interconnects. Among the material platforms available, silicon nitride (Si3N4) displays excellent optical properties such as broadband transparency, moderately high refractive index, and relatively strong nonlinearities. Indeed, Si3N4 integrated waveguides display ultralow-loss (few decibels per meter), which enables efficient light processing and nonlinear optics. Moreover, Si3N4 is compatible with standard complementary metal oxide semiconductor (CMOS) processing techniques,which facilitates the manufacture scalability required by mass deployment of PICs. However, the selection of a single photonic platform sets limitations to the device functionalities due to the intrinsic properties of the material and the fundamental limitation of optical waveguiding. Multilayer integration of different platforms can overcome the limitations encountered in a singleplatform PIC.This thesis presents the development of advanced techniques for the waferlevel manufacturing of ultralow-loss Si3N4 devices and approaches to enable their interface with active components like modulators and chip-scale comb sources (microcombs). The investigation covers the tailoring of a waveguide to the functionality required, the wafer-scale manufacturing of Si3N4, and how to overcome the limitations of a single platform on a wafer. These studies enable high-yield fabrication of microcombs, the integration of two Si3N4 platforms on the same wafer, and a strategy to efficiently couple to an integrated LiNbO3 layer to expand the chip functionality and scale up the complexity of the PIC

INTEGRATED CHIRPED-GRATING SPECTROMETER-ON-A-CHIP

In this dissertation we demonstrate a new structure based on waveguide coupling atop a silicon wafer using a chirped grating to provide the dispersion that leads to a high-resolution, compact, fully integrable and CMOS-compatible spectrometer. Light is both analyzed and detected in a single, completely monolithic component which enables realizing a high-resolution portable spectrometer with an extremely compact footprint. The structure is comprised of a SiO2/Si3N4/SiO2 waveguide on top of a silicon wafer. Grating regions are fabricated on the top cladding of the waveguide. The input light is incident on a chirped grating area known as the collection area. Because of the local variation of the grating pitch across the collection area, different wavelengths of light are coupled into the waveguide at different lateral positions across the collection area. Guided light is then outcoupled through second grating region known as the detection area to the array of photodiodes placed either atop the second grating region or below the second grating region in silicon chip. Therefore, spectral information is encoded in the chirped grating coupler, which is fabricated in a single lithography step, independent of the number of channels. For these initial experiments, a separate detection array was used. In future iterations, these detectors can be integrated into the underlying silicon, resulting in a fully integrated spectrometer on a chip. Varying the input angle of the light will vary the measurement spectral range. This will result in an inexpensive spectrometer on chip, with adjustable resolution and spectral coverage controlled by the grating chirp and the input angle

Low-Mass Planar Photonic Imaging Sensor

Continuing on the successful progress of NIAC Phase I, this report summarizes the technical progress achieved under NIAC Phase II during the performance period September 19, 2014-June 18, 2017. During this period, the research team has made the following accomplishments: designed and layout a silica photonic integrated circuit (PIC) as a two baseline interferometric imager; constructed an experiment to utilize the two baselines for complex visibility measurement on a point source and a variable width slit; analyzed and studied the testbed results. (in collaboration with Lockheed Martin); designed and layout Si3N4 PICs for the low-resolution and high-resolution SPIDER telescope; fabricated the multi-layer Si3N4 PIC for low and high resolution SPIDER telescope; characterize the optical throughput and heater response for Si3N4 PIC for low and high resolution SPIDER telescopes; carried out imaging experiments using the Si3N4 PIC low-resolution version (in collaboration with Lockheed Martin); investigated signal-to-noise (SNR) ratio of SPIDER imager compared to the conventional panchromatic imager (in collaboration with Lockheed Martin); fulfilled the SNR simulation upon SPIDER imager (in collaboration with Lockheed Martin)

Low-Mass Planar Photonic Imaging Sensor

Continuing on the successful progress of NIAC (NASA Innovative Advanced Concepts) Phase I, this report summarizes the technical progress achieved under NIAC Phase II during the performance period September 19, 2014 to June 18, 2017. During this period, the research team has made the following accomplishments: designed and layout a silica photonic integrated circuit (PIC) as a two baselineinterferometric imager; constructed an experiment to utilize the two baselines for complex visibility measurementon a point source and a variable width slit; analyzed and studied the testbed results (in collaboration with Lockheed Martin); designed and layout Si3N4 PICs for the low-resolution and high-resolution SPIDER (Segmented Planar Imaging Detector for Electro-Optical Reconnaissance) telescope; fabricated the multi-layer Si3N4 PIC for low and high resolution SPIDER telescope; characterized the optical throughput and heater response for Si3N4 PIC for low and highresolution SPIDER telescopes; carried out imaging experiments using the Si3N4 PIC low-resolution version (in collaboration with Lockheed Martin); investigated signal-to-noise (SNR) ratio of SPIDER imager compared to the conventional panchromatic imager (in collaboration with Lockheed Martin); fulfilled the SNR simulation upon SPIDER imager (in collaboration with Lockheed Martin)