Garrett A. Ejzak

Integrated silicon-photonic module for generating widely tunable, narrow-line RF using injection-locked lasers

We have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. This system is based on injection seeding one laser with a selectable high-order sideband obtained from a second laser that is phase modulated by a narrow-line, low-frequency RF reference oscillator. When these coherent optical outputs are mixed on a fast photodiode, RF output is obtained, with linewidth and phase noise characteristics that are limited by the reference oscillator. The RF output can be tuned over a wide range, in multiples of the reference frequency, and can be fine-tuned by tuning the reference oscillator. In this paper, we present the results of our efforts to develop an integrated version of this system, based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips. We describe the fabrication process of the integrated module using heterogeneous integration techniques, and present preliminary results including two lasers operating simultaneously on a single silicon-photonic chip.

Toward a widely tunable narrow linewidth RF source through heterogenous silicon photonic integration

By mixing two lasers together it, is possible to generate RF signals from near DC to hundreds of GHz. Through the use of a narrow-linewidth low-frequency oscillator, optical modulator, and injection locking, much higher frequency outputs can be produced that still retain the narrow linewidth of the low frequency oscillator. Here we focus on the design and implementation of an integrated device including photonic sources and modulators to realize the system described above. Specifically, we report on the creation and mixing of two tunable lasers on a silicon platform with a heterogeneously integrated gain medium realized in a III-V material system.

A Widely Tunable Narrow Linewidth RF Source Integrated in a Heterogeneous Photonic Module

Generating radio-frequency signals over the entire spectrum, from 1 to 100 GHz, typically requires the use of multiple oscillators designed only for specific narrow bands of operation within that spectrum. An optoelectronic system based on modulation side-band-injection-locked lasers is capable of generating RF frequencies tunable over a span of more than seven octaves with low phase noise . We present the results of our efforts to develop a heterogeneously integrated version of this system based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips. Towards that end, we have successfully demonstrated an integrated laser module and achieved tunable RF generation with a ~ 1 Hz linewidth.

Toward a widely tunable narrow linewidth RF source utilizing an integrated heterogenous silicon photonic module

A system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers has been developed. By injection seeding one laser with a sideband obtained from a second laser that is phase modulated by a spectrally pure low-frequency RF reference oscillator and then mixing these coherent optical outputs on a fast photodiode, RF with the same linewidth and phase noise characteristics as the reference oscillator can be produced. By using harmonics of the reference oscillator the RF output can be tuned over a much wider range than the reference oscillator while maintaining its narrow linewidth.Here we present the results of our efforts to develop an integrated version of this system, based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips.Towards that goal we have successfully demonstrated an integrated module and shown tunable RF generation with a 1 Hz linewidth.

Development of a widely tunable narrow linewidth RF generator using a hybrid silicon photonic platform

We have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. Here we focus on the design and implementation of an integrated module and analysis of the produced RF.

Toward an integrated silicon-photonic module for widely tunable narrow-line RF source using injection-locking

Through the use of a narrow-linewidth low-frequency oscillator, optical modulator, and injection locking, we have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. Here we focus on the design and implementation of an integrated device including photonic sources and modulators to realize the system described above. Specifically, we report on the creation and mixing of two tunable lasers on a silicon platform with a heterogeneously integrated gain medium realized in a III-V material system.

Real-time atmospheric imaging and processing with hybrid adaptive optics and hardware accelerated lucky-region fusion (LRF) algorithm

Atmospheric turbulences can significantly deteriorate the performance of long-range conventional imaging systems and create difficulties for target identification and recognition. Our in-house developed adaptive optics (AO) system, which contains high-performance deformable mirrors (DMs) and the fast stochastic parallel gradient decent (SPGD) control mechanism, allows effective compensation of such turbulence-induced wavefront aberrations and result in significant improvement on the image quality. In addition, we developed advanced digital synthetic imaging and processing technique, “lucky-region” fusion (LRF), to mitigate the image degradation over large field-of-view (FOV). The LRF algorithm extracts sharp regions from each image obtained from a series of short exposure frames and fuses them into a final improved image. We further implemented such algorithm into a VIRTEX-7 field programmable gate array (FPGA) and achieved real-time video processing. Experiments were performed by combining both AO and hardware implemented LRF processing technique over a near-horizontal 2.3km atmospheric propagation path. Our approach can also generate a universal real-time imaging and processing system with a general camera link input, a user controller interface, and a DVI video output.

512

The demand for high-speed and/or high-temperature infrared (IR) scene projectors has led to the development of systems based on IR light-emitting-diode (LED) arrays. Using mid-wave (3--5 μm) superlattice LED arrays, a 512 × 512 pixel scene projection system operating at 100 Hz has been fully developed. These LEDs, flip-chip bonded to a read-in integrated circuit, display temperatures of up to 1350 K when cooled to liquid nitrogen temperature (77 K). Using custom drive electronics and packaging, the array has been nonuniformity corrected (NUCed) and has survived hundreds of hours of operation at multiple facilities. This system is fully configurable by the user and has a digital visual interface to display content.

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“Lucky-region” fusion (LRF) is a synthetic imaging technique that has proven successful in enhancing the quality of images distorted by atmospheric turbulence. The LRF algorithm extracts sharp regions of an image obtained from a series of short exposure frames, and fuses the sharp regions into a final, improved image. In our previous research, the LRF algorithm had been implemented on a PC using the C programming language. However, the PC did not have sufficient processing power to handle real-time extraction, processing and reduction required when the LRF algorithm was applied to real-time video from fast, high-resolution image sensors rather than single picture images. This document describes a hardware implementation of the LRF algorithm on a VIRTEX-7 field programmable gate array (FPGA) to achieve real-time image processing. The novelty in our approach is the creation of a “black box” LRF video processing system with a general camera link input, a user controller interface, and a camera link or DVI video output. We also describe a custom hardware simulation environment we have built to test our LRF implementation.

512, 100 Hz Mid-Wave Infrared LED Microdisplay System

In this effort, we describe our recent progress towards demonstrating optical gain in erbium-doped lithium niobate and its potential for use in Erbium-Doped Waveguide Amplifiers (EDWAs) and lasers. By introducing erbium into lithium niobate, we have the potential for both gain at telecom wavelengths and electro-optic modulation in a single material. This has many possible applications, including high speed, narrow band tunable lasers for RF generation and other applications. We focus on lithium niobate grown in the presence of erbium available with a uniform doping profile from Roditi International. In this work we discuss photoluminescence, amplified spontaneous emission, gain, and lasing in titanium-indiffused waveguides.