SBIR-STTR Award

In order to provide 100 GHz clock signals for the next generation of highly parallel optical signal processors, Semi-Custom Logic, Inc., (SLI), proposes to develop a miniature integrated Tunable GigaHertz Optical Clock Generator (TGOCG) that can provide ultra-stable high speed clock recovery with tunability from 1 GHz to 100 GHz. Current clock generation techniques are limited by the available bandwidth of the electronic approach, or the bulky configuration and fixed rate of the optical approach. SLI's TGOCG is based on mature GaAs/InP technology, which can provide miniature configuration and high integration capability with standard opto-electronic integrated circuits (OEIC). SLI's TGOCG will provide a cost-effective clock generation solution for the next generation of diversified optical systems. The wideband clock tunability (1-100 GHz) will significantly benefit military applications. For commercial applications, a stable short pulse train is needed for optical fiber networks and high bit rate time division multiplexed systems.

Keywords:
Kerr Effect Non-Linear Directional Coupling Clock Generator

During Phase I of this project, Semi-Custom Logic, Inc. (SLI) accomplished the design and simulation of a Tunable Gigahertz Optical Clock Generator (TGOCG) with clock frequencies from multi-GHz to 100 + GHz and 20-30% tunability by dynamically varying the DC current bias. This seminal achievement has set a new lofty standard for a novel intrinsic opto-electronic clock generator without complex and bulky high frequency circuit implementation. Typical optical clock generators either suffer by requiring the sophisticated external high frequency modulator or expensive and intricate integrated circuit designs. SLI's TGOCG's dramatic frequency tunability is based on the intrinsic nonlinear Kerr effect of GaAs/AlGaAs semiconductor lasers with an integrated non-linear directional coupler (NLDC). Because of the Kerr effect of GaAs/AlGaAs, the index of refraction in an NLDC varies with temporal local light intensity. Therefore, the fraction of light transferred from one waveguide to the other depends on the input light intensity, as well as on the geometric structure of the NLDC. Because the fraction of the light that bounces back depends on the input light intensity itself, the NLDC is an intensity-dependent external cavity of the semiconductor laser. With this unique design, SLI's TGOCG does not use expensive and demanding submicron lithography technology or require a large amount of wafer real estate. Additionally, the transition from research to commercial production can be made in a very timely fashion and will likely attract manufacturing and marketing partners. This ultra high speed tunable optical clock generator can and will significantly impact and benefit future optical signal processing and optical communications.

Keywords:
Kerr Effect Non-Linear Directional Coupling Clock Generator