N212-118 TITLE: Integrated Low-Jitter Mode-Locked Source for Optical Signal Processing Applications

RT&L FOCUS AREA(S): Microelectronics

TECHNOLOGY AREA(S): Air Platforms;Electronics

OBJECTIVE: Develop a compact, low-timing jitter, semiconductor mode-locked for optical signal processing applications.

DESCRIPTION: Emerging optical signal processing methods utilize the broadband nature of the optical spectrum to perform radio frequency (RF) signal processing in the optical domain. Examples of this include time-stretch analog analog-to to-digital converters [Ref 1], photonic sampling [Ref 2] and the use of optical speckle to perform compressive RF sensing [Ref 3]. Both applications require pulsed optical sources with a wide wide-optical envelope and low low-timing jitter. To date, fiber-based mode-locked lasers [Ref 4] have been used for this application and have met the performance requirements for these applications such as ultra wideband electronic warfare receivers. To allow a reduction of size and power of these emerging optical signal processing techniques, there is a need to develop compact (on the order of 100 cubic centimeters (cc), efficient semiconductor sources that can be chip-scale integrated in compact implementations, and can meet the requirements for implementation on size-and-power constrained Navy platforms. The developed source must be compatible with further integration of additional functionality such as analog optical modulators and low-loss optical waveguides. The mode-locked optical source should operate in the 1.5-micron band with average output power exceeding 10 milliwatts (mW). The pulse repetition rate should be in the 10-100 megahertz (MHz) range, with pulse timing jitter less than 100 femtoseconds (fs), and an optical envelope exceeding 10 nanometers (nm).

PHASE I: Develop, design, and demonstrate the feasibility of an approach for a mode-locked or pulsed optical source that operates in the 1.5 micron � band with average output power exceeding 10 milliwatts (mW), 10-100 MHz pulse repetition rate, pulse timing jitter less than 100 fs, and an optical envelope exceeding 10 nanometers (nm). Develop a model for an optical signal processing system of interest for the Navy. Develop further application--specific requirements specifications for the mode-locked source. Through simulations or practical supporting measurement show that the proposed optical source will meet these requirements. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Fabricate and demonstrate a laser source that meets requirements defined in Phase I. Develop a prototype packaged laser demonstrator. Ensure, that at the end of Phase II, this packaged laser should be at Technology Readiness Level (TRL) 4 [Ref 5], with performance measured in a laboratory environment.

PHASE III DUAL USE APPLICATIONS: Complete development, perform final testing, and integrate and transition the final solution to future naval airborne electronic warfare and wideband radar systems.

As pointed out in the Description, this technology can be applied to time-stretch analog-to-digital converters, photonic sampling and the use of optical speckle to perform compressive RF sensing.

REFERENCES:

1. Valley, G. C. "Photonic analog-to-digital converters." Optics Express, 15(5), 2007, pp. 1955-1982. https://doi.org/10.1364/OE.15.001955.
2. Misra, A., Kress, C., Singh, K., Preußler, S., Scheytt, J. C. and Schneider, T. "Integrated source-free all optical sampling with a sampling rate of up to three times the RF bandwidth of silicon photonic MZM." Optics Express, 27(21), 2019, pp. 29972-29984. https://doi.org/10.1364/OE.27.029972.
3. Sefler, G. A., Shaw, T. J. and Valley, G. C. "Demonstration of speckle-based compressive sensing system for recovering RF signals." Optics express, 26(17), 2018, pp. 21390-21402. https://doi.org/10.1364/OE.26.021390.
4. Kim, J. and Song, Y. "Ultralow-noise mode-locked fiber lasers and frequency combs: principles, status, and applications." Advances in Optics and Photonics, 8(3), 2016, pp. 465-540. https://doi.org/10.1364/AOP.8.000465.
5. Research Directorate, Defense, Research and Engineering (DDR&E). "Technology readiness assessment (TRA) Deskbook. Department of Defense, July 2009, pp. C-4-C-5. http://www.acqnotes.com/Attachments/Technology%20Readiness%20Assessment%20Deskbook.pdf.

KEYWORDS: Low jitter Lasers; Mode Locked Lasers; Photonic Sampling; Optical Speckle; Direct RF Conversion; Optical Compressive Sensing