Silicon Integrated Arrays: From Microwave to IR

Integrated chips have enabled realization and mass production of complex systems in a small form factor. Through process miniaturization many novel applications in silicon photonics and electronic systems have been enabled. In this thesis I have provided several examples of innovations that are only enabled by integration. I have also demonstrated how electronics and photonics circuits can complement each other to achieve a system with superior performance.</p

A 1-D heterodyne lens-free optical phased array camera with reference phase shifting

This paper presents the first integrated silicon photonics optical phased array (OPA) receiver with imaging capabilities. A 32-element 1D OPA with an overall aperture size of 96x50 μm^2 is used to generate an electrically steerable “gazing beam”. The OPA receiver elements couple the incident light to on-chip waveguides which is processed as a phased array receiver. To minimize signal loss and enhance sensitivity, a heterodyne architecture with phase shifters in the local reference path is utilized. The OPA receiver can provide fully programmable angular selectivity with a grating-lobe-free field-of-view of 30° and a gazing beamwidth of 0.74°

An 8x8 Heterodyne Lens-less OPA Camera

This paper presents an 8x8 optical phased array (OPA) receiver that operates as a lens-less camera using a heterodyne architecture on a thin silicon-photonics integrated SOI substrate. It has a receiving beam width of 0.75° and beam steering range of 8°

Self-equalizing photodiodes, a hybrid electro-optical approach to tackle bandwidth limitation in high-speed signaling

In this paper we provide the design details of self-equalizing photodetectors which enable higher data rate transmission by improving the overall bandwidth of the bandwidth limited transmission link, through a hybrid electro-optical solution. Two different self-equalizing photodiodes, one having fixed equalization and the other being programmable are presented as proof of concept

A self-equalizing photo detector

A self-equalizing photo-detector (SEPD) that mitigates the bandwidth limitations of electro-optical components of optical communication systems is demonstrated, enabling higher rate of data transmission, using slower components. Unlike other all-optical equalization schemes, SEPD is optically wide band, thus does not require wavelength tuning

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

Electronic Two-Dimensional Beam Steering for Integrated Optical Phased Arrays

This paper presents electrical beam steering in an integrated 4x4 2D optical phased array (OPA) on a silicon on insulator (SOI) process enabling fast and repeatable beam steering for next generation projection, tracking, and imaging

Nanophotonic projection system

Low-power integrated projection technology can play a key role in development of low-cost mobile devices with built-in high-resolution projectors. Low-cost 3D imaging and holography systems are also among applications of such a technology. In this paper, an integrated projection system based on a two-dimensional optical phased array with fast beam steering capability is reported. Forward biased p-i-n phase modulators with 200MHz bandwidth are used per each array element for rapid phase control. An optimization algorithm is implemented to compensate for the phase dependent attenuation of the p-i-n modulators. Using rapid vector scanning technique, images were formed and recorded within a single snapshot of the IR camera

An Adjustable Self Equalizing Photo Detector

An optically-wideband adjustable self-equalizing photo-detector (ASEPD), capable of reviving eye closure due to limited bandwidth of electro-optical components in an optical link, is presented. The ASEPD enables use of various slower electro-optical components in faster data links

Nanophotonic coherent imager

An integrated silicon nanophotonic coherent imager (NCI), with a 4 × 4 array of coherent pixels is reported. In the proposed NCI, on-chip optical processing determines the intensity and depth of each point on the imaged object based on the instantaneous phase and amplitude of the optical wave incident on each pixel. The NCI operates based on a modified time-domain frequency modulated continuous wave (FMCW) ranging scheme, where concurrent time-domain measurements of both period and the zero-crossing time of each electrical output of the nanophotonic chip allows the NCI to overcome the traditional resolution limits of frequency domain detection. The detection of both intensity and relative delay enables applications such as high-resolution 3D reflective and transmissive imaging as well as index contrast imaging. We demonstrate 3D imaging with 15μm depth resolution and 50μm lateral resolution (limited by the pixel spacing) at up to 0.5-meter range. The reported NCI is also capable of detecting a 1% equivalent refractive index contrast at 1mm thickness