Large-Scale Photonics Integration: Data Communications to Optical Beamforming

Integrated photonics is an emerging technology that has begun to transform our way of life with the same amount of impact that integrated CMOS electronics has. Currently, photonics integration is orders of magnitude less complicated than its electronics counterparts. Nonetheless, it serves as one of the main driving forces to meet the exponentially increasing demand for high-speed and low-cost data transfer in the Information Age. It also promises to provide solutions for next-generation high-sensitivity image sensors and precision metrology and spectroscopy instruments. In this thesis, integrated photonics architectures for solid-state photonic beamforming and processing are investigated for high-resolution and high sensitivity lens-free transceiver applications. Furthermore, high-efficiency integrated electro-optical modulators aiming to meet the demand of high-density photonic integration with improved modulation efficiency, small footprint, and lower insertion loss are investigated. Two integrated photonic solid-state beamforming architectures incorporating two-dimensional apertures are explored. First, a novel transceiver architecture for remote sensing, coherent imaging, and ranging applications is demonstrated. It reduces system implementation complexity and offers a methodology for very-large-scale coherent transceiver beamforming applications. Next, a transmitter beamforming architecture inspired by the diffraction pattern of the slit annular ring is analyzed and demonstrated. This transceiver architecture can be used for coherent beamforming applications such as imaging and point-to-point optical communication. Finally, a coherent imager architecture for high-sensitivity three-dimensional imaging and remote-sensing applications is present. This novel architecture can suppress undesired phase fluctuations of the optical carrier signal in the illumination and reference paths, providing higher resolution and higher acquisition speed than previous implementations. Moreover, several compact, high-speed CMOS compatible modulators that enable high-density photonic integration are explored. Ultra-compact and low insertion loss silicon-organic-hybrid modulators are designed and implemented for high-speed beamforming and high-efficiency complex signal modulation applications. Finally, a novel integrated nested-ring assisted modulator topology is analyzed and implemented for high-density and high modulation efficiency applications.</p

Large-Scale Crosstalk-Corrected Thermo-Optic Phase Shifter Arrays in Silicon Photonics

We introduce a thermo-optic phase shifter (TOPS) array architecture with independent phase control of each phase shifter for large-scale and high-density photonic integrated circuits with two different control schemes: pulse amplitude modulation (PAM) and pulse width modulation (PWM). We realize a compact spiral TOPS and a 288-element high-density row-column TOPS array with this architecture and drive TOPS with waveforms of both control schemes and of different array sizes. We present a thermal excitation model and a finite difference method-based simulation to simulate large-scale TOPS arrays and compare both schemes experimentally and theoretically. We also analyze the effects of thermal crosstalk in the realized TOPS array and implement a thermal crosstalk correction algorithm with the developed model. The high-density TOPS array architecture and the thermal crosstalk correction algorithm pave the way for high-density TOPS arrays with independent phase control in large-scale photonic integrated circuits interfaced with electronics limited in voltage swing and bandwidth.Comment: 12 pages and 19 figures accepted to IEEE JSTQE for publicatio

High sensitivity active flat optics optical phased array receiver with a two-dimensional aperture

Optical phased arrays (OPAs) on integrated photonic platforms provide a low-cost chip-scale solution for many applications. Despite the numerous demonstrations of OPA transmitters, the realization of a functional OPA receiver presents a challenge due to the low received signal level in the presence of noise and interference that necessitates high sensitivity of the receiver. In this paper, an integrated receiver system is presented that is capable of on-chip adaptive manipulation and processing of the captured waveform. The receiver includes an optoelectronic mixer that down-converts optical signals to radio frequencies while maintaining their phase and amplitude information. The optoelectronic mixer also provides conversion gain that enhances the system sensitivity and its robustness to noise and interference. Using this system, the first OPA receiver with a two-dimensional aperture of 8-by-8 receiving elements is demonstrated which can selectively receive light from 64 different angles. The OPA receiver can form reception beams with a beamwidth of 0.75° over an 8° grating-lobe-free field of view

Breaking FOV-Aperture Trade-Off with Multi-Mode Nano-Photonic Antennas

Nano-photonic antennas are one of the key components in integrated photonic transmitter and receiver systems. Conventionally, grating couplers, designed to couple into an optical fiber, suffering from limitations such as large footprint and small field-of-view (FOV) have been used as on-chip antennas. The challenge of the antenna design is more pronounced for the receiver systems, where both the collected power by the antenna and its FOV often need to be maximized. While some novel solutions have been demonstrated recently, identifying fundamental limits and trade-offs in nano-photonic antenna design is essential for devising compact antenna structures with improved performance. In this paper, the fundamental electromagnetic limits, as well as fabrication imposed constraints on improving antenna effective aperture and FOV are studied, and approximated performance upper limits are derived and quantified. By deviating from the conventional assumptions leading to these limits, high-performance multi-mode antenna structures with performance characteristics beyond the conventional perceived limits are demonstrated. Finally, the application of a pillar multi-mode antenna in a dense array is discussed, an antenna array with more than 95% collection efficiency and 170∘ FOV is demonstrated, and a coherent receiving system utilizing such an aperture is presented

Breaking FOV-Aperture Trade-Off with Multi-Mode Nano-Photonic Antennas

Nano-photonic antennas are one of the key components in integrated photonic transmitter and receiver systems. Conventionally, grating couplers, designed to couple into an optical fiber, suffering from limitations such as large footprint and small field-of-view (FOV) have been used as on-chip antennas. The challenge of the antenna design is more pronounced for the receiver systems, where both the collected power by the antenna and its FOV often need to be maximized. While some novel solutions have been demonstrated recently, identifying fundamental limits and trade-offs in nano-photonic antenna design is essential for devising compact antenna structures with improved performance. In this paper, the fundamental electromagnetic limits, as well as fabrication imposed constraints on improving antenna effective aperture and FOV are studied, and approximated performance upper limits are derived and quantified. By deviating from the conventional assumptions leading to these limits, high-performance multi-mode antenna structures with performance characteristics beyond the conventional perceived limits are demonstrated. Finally, the application of a pillar multi-mode antenna in a dense array is discussed, an antenna array with more than 95% collection efficiency and 170∘ FOV is demonstrated, and a coherent receiving system utilizing such an aperture is presented

High sensitivity active flat optics optical phased array receiver with a two-dimensional aperture

Optical phased arrays (OPAs) on integrated photonic platforms provide a low-cost chip-scale solution for many applications. Despite the numerous demonstrations of OPA transmitters, the realization of a functional OPA receiver presents a challenge due to the low received signal level in the presence of noise and interference that necessitates high sensitivity of the receiver. In this paper, an integrated receiver system is presented that is capable of on-chip adaptive manipulation and processing of the captured waveform. The receiver includes an optoelectronic mixer that down-converts optical signals to radio frequencies while maintaining their phase and amplitude information. The optoelectronic mixer also provides conversion gain that enhances the system sensitivity and its robustness to noise and interference. Using this system, the first OPA receiver with a two-dimensional aperture of 8-by-8 receiving elements is demonstrated which can selectively receive light from 64 different angles. The OPA receiver can form reception beams with a beamwidth of 0.75° over an 8° grating-lobe-free field of view

A handheld magnetic sensing platform for antigen and nucleic acid detection

The core requirements for point-of-care (POC) diagnostics necessitate low-cost, portability, easily integrated sample preparation, and quick measurement time. Frequency-shift based magnetic sensing is a measurement technique utilizing a complementary metal-oxide-semiconductor (CMOS) integrated-circuit (IC) chip for magnetic label detection. The sensing scheme leverages the low-cost manufacturing of IC chips while demonstrating the potential for multiplexing capabilities. In this article, we present modifications to this scheme for POC viability. We introduce a handheld reusable reader and a disposable open-well cartridge for the detection of nucleic acids and antigens. The diagnostic system utilizes a novel “magnetic freezing” technique to reduce measurement time, obviates baseline measurement before or during biological assay, and reduces sensor noise. We utilize these enhancements for the room temperature, amplification-free detection of a 31 base-pair DNA oligomer and the interferon-γ (IFN-γ) protein. We have demonstrated reliable measurements down to 100 pM for the DNA assay and 1 pM for the protein

A Nonuniform Sparse 2-D Large-FOV Optical Phased Array With a Low-Power PWM Drive

Integrated optical phased arrays (OPAs) capable of adaptive beamforming and beam steering enable a wide range of applications. For many of these applications, a large scale 2-D OPA with full phase control for each radiating element is essential to achieve a functional low-cost solution. However, the scalability of such OPAs has been hampered by the optical feed distribution difficulties in a planar photonics process, as well as the high power consumption associated with having a large number of phase control units. In this paper, we present a two-chip solution low-power scalable OPA with a nonuniform sparse aperture, providing radiation pattern adjustment and feed distribution feasibility in a CMOS compatible silicon photonics process. The demonstrated OPA with a 128-element aperture achieves the highest reported grating-lobe-free field-of-view (FOV)-to-beamwidth ratio of 16°/0.8°, which is equivalent to a 484-element uniform array. This translates to at least 400 resolvable spots, 30 times more than the state-of-the-art 2-D OPAs. Moreover, by utilizing compact phase shifters in a row–column power delivery grid, we reduce the number of required drivers from 144 to 37. A high-swing pulsewidth modulation (PWM) driving circuit featuring breakdown voltage multipliers and soft turn-on activation significantly reduces the power consumption of the system. The electronic driver chip and the integrated photonic chip are fabricated on a 65-nm CMOS process and a thick silicon-on-insulator (SOI) silicon photonics process, occupying 1.7 mm^2 and 2.08 mm^2 of active area, respectively

IQ Photonic Receiver for Coherent Imaging With a Scalable Aperture

Silicon photonics (SiP) integrated coherent image sensors offer higher sensitivity and improved range-resolution-product compared to direct detection image sensors such as CCD and CMOS devices. Previous generations of SiP coherent imagers suffer from relative optical phase fluctuations between the signal and reference paths, which results in random phase and amplitude fluctuations in the output signal. This limitation negatively impacts the SNR and signal acquisition times. Here, we present a coherent imager system that suppresses the optical carrier signal and removes non-idealities from the relative optical path using a photonic in-phase (I) and quadrature (Q) receiver via a 90&#x00B0; hybrid detector. Furthermore, we incorporate row-column read-out and row-column addressing schemes to address the electro-optical interconnect density challenge. Our novel row-column read-out architecture for the sensor array requires only $2N$ interconnects for N2 sensors. An $8\times 8$ IQ sensor array is presented as a proof-of-concept demonstration with $1.2\times 10^{-5}$ resolution over range accuracy. Free-space FMCW ranging with $250 \mu \text {m}$ resolution at 1 m distance has been demonstrated using this sensor array

A Low Power PWM Optical Phased Array Transmitter with 16° Field-of-View and 0.8° Beamwidth

An optical phased array (OPA) transmitter system with a high-swing electrical PWM driver achieving the highest reported grating-lobe-free field-of-view to beamwidth ratio of 16°/0.8° for a two-dimensional aperture is presented. This ratio translates to 400 resolvable spots-which is 30x more numerous than the state-of-the-art. This scalable OPA, with a sparsely populated aperture, overcomes optical routing difficulties in planar photonic processes while maintaining the desired transmitter beam characteristics. To reduce the power consumption, a row-column electrical connection grid for the 144 optical phase shifters decreases the number of electrical drivers from 144 to 37. The PWM driver chip incorporates a breakdown-voltage multiplying architecture to increase the output voltage swing. The 65nm CMOS electronic driver chip and the photonic chip, fabricated through a standard silicon photonics process, occupy 1.7mm² and 2.08mm² of active area respectively