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Low Noise Photonic Oscillator in Short-Wave Infrared (SWIR) Band


OBJECTIVE: Perform feasibility study to develop very narrow, stable photonics oscillator capable of operation in Short-Wave Infrared (SWIR) band. DESCRIPTION: High-performance SWIR transceiver plays the critical role in sensing, ranging, jamming and fire control systems for airborne systems. Laser radar (LADAR) systems operating in SWIR band carry particular importance as they provide the access to low-loss sensing and communication window. Indeed, SWIR band is populated by important spectral fingerprints of jet/rocket propulsion systems; LADAR target acquisition and fire control possesses qualitatively larger range than that in conventional near infrared (NIR) band. In order to realize the advantage inherent to SWIR-band LIDAR band, it is necessary to provide local oscillators with performance that is at least comparable or better than the existing NIR devices. Specifically, this means that SWIR photonics oscillator should possess a) linewidth below 30Hz; b) relative intensity noise (RIN) below -160dB/Hz in immediate carrier vicinity and c) sufficient optical power. If realized, SWIR-band oscillator would qualitatively improve the performance of high-sensitivity systems such as synthetic aperture radars (SAR), LIDARs and airborne data links [1]. The performance of the state-of-the-art oscillators fundamentally depends on the cavity construction and its underlying stability [2]. Indeed, spectrally narrow emission from a stable laser requires that a highly resonant cavity be brought to thermal and mechanical equilibrium. While passively or actively stabilized cavities can, at least in principle, be fabricated equally well in both NIR and SWIR bands, materials providing optical gain in NIR band are vastly superior. Worse, the SWIR gain mechanisms rely on less efficient, noisy and narrow-band processes [3]. Consequently, new approach to construction of highly stable, low-noise photonics oscillators operating in SWIR band is required. A new path towards the construction of SWIR oscillator should address the following set of minimum requirements: 1) Spectral band coverage up to minimum of 2200nm; preferred coverage includes contiguous NIR/SWIR bands; 2) Spectral linewidth commensurate with long rage coherent sensing and communication requirements; maximal linewidth below 30Hz; 3) Minimum optical power of 100mW. Any solution that combines the above technical targets with frequency agility (tunability) is particularly encouraged. If the practical SWIR oscillator can match the state-of-the-art NIR performance, the resulting device would provide fundamentals for re-engineering of high-performance SAR/LIDAR systems, doubling their range and inherent sensitivity. PHASE I: Perform feasibility study for practical design of narrow SWIR oscillator possessing a) spectral linewidth below 30Hz, b) operating in minimum spectral range defined by 1900nm (or lower) and 2200nm (or higher) and c) minimum 100mW of optical power in continuous (CW) or quasi-CW operational regime. Phase I is expected to derive the formal plan for Phase II effort. PHASE II: Using the design from Phase I, practical device design should be derived and subcomponents tested. Phase II work design is expected to result in prototype unit construction. The prototype must support at least two of three critical parameters: linewidth, full SWIR coverage and higher than 100mW power. PHASE III: A demonstrator SWIR oscillator compatible with pollution (carbon) and HF sensing requirement should be assembled and tested. Two separate applications (commercial/military) should be targeted by specifically designing the fieldable units. REFERENCES: 1. Zachary J. Lemnios,"Transforming US Defense R & D to Meet 21st Century Challenges,"NDIA 11th Annual Science and Engineering Technology Conference, 13 April 2010. 2. D. Eliyahu, D. Seidel, and L. Maleki,"RF amplitude and phase-noise reduction of an optical link and an opto-electronic oscillator,"IEEE Trans Microwave Theory Tech., vol 56, pp. 449-456, 2008. 3. T.B.Simpson, Jia-Ming Liu, Nicholas Usechak and Vassilios Kovanis,"Tunable Photonic Microwave Oscillator Self-Locked by Polarization-Rotated Optical Feedback,"Timing and Frequency Symposium Proceedings, IEEE 2012.
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