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High Performance Compact Medium-Power Long-Wave Infrared (LWIR) Laser System for Shipboard Deployment

Description:

TECHNOLOGY AREA(S): Sensors, Electronics, Battlespace 

OBJECTIVE: Develop a compact long-wave infrared (LWIR) laser system for the Navy. 

DESCRIPTION: Airborne threats to surface ships, whether anti-ship cruise missiles, drones, or aircraft, benefit from passive sensing technology spanning the infrared (IR) spectrum. Passive sensors are widely available, compact, require little power, and generate little waste heat. Furthermore, because passive sensors are not dependent on discrete energy transitions, they are sensitive across contiguous wavelength bands. That is, passive sensors – either discrete photodiodes or focal plane arrays – “see” across a band of the spectrum. Sensor availability in the long-wave infrared (LWIR) wavelength band offers advantages in certain environments. At times, signature contrast and atmospheric affects favor LWIR propagation in many regions of the globe and certain combinations of humidity and turbulence favor higher contrast imaging in the LWIR. Where space and power allow, prudence dictates that sensing in multiple IR bands (for example, mid-wave IR – from 3 to 5 micro meters - combined with LWIR) be employed together for maximum effect. This presents a significant challenge to ship self-defense systems that must likewise counter threats across multiple bands. Active IR sensors and IR countermeasures require lasers as sources. Optimally, laser sources should cover the broadest range possible within their band to ensure availability. For example, broad coverage in the LWIR band minimizes the vulnerability to counter-countermeasures and allows for optimal transmission at wavelengths favorable for atmospheric propagation. The requirement for broad spectral coverage is achievable, however, it complicates the desire for compactness. Furthermore, the ship’s response system, whether attempting to simply illuminate and detect the threat or apply countermeasures, must transmit sufficient power to achieve the maximum range and the high power-density required presents thermal management challenges. These issues are highly relevant because system performance is enhanced when the laser aperture is mounted high on the ship’s superstructure, making optimization of size, and by inference efficiency, significant considerations and challenges. The Navy seeks development of a compact LWIR laser system as described above. It should be noted that a “laser system” is considered, in this case, to include technologies where beam combining from multiple individual lasers (or some alternate technology) is used to achieve the requirements (as distinct from a single LWIR laser solution). The laser system is also understood to incorporate any power conversion, packaging, and control required for the system to function as an integrated source of single-beam LWIR laser output. The laser system should cover the entire LWIR band and allow for maximum atmospheric transmission while incorporating means to optimize beam quality for maximum atmospheric propagation. The power output should be 100W or greater in continuous wave (CW) operation. However, technologies that offer scalability of output power are most attractive. In addition to CW operation, the laser system shall also be capable of providing pulsed output. Physical constraints imposed by the application make minimization of the laser system volume the primary consideration. As a requirement, the laser system shall occupy a combined volume of no more than 8ft3 with a goal of less than 4ft3. Due to the compact packaging this imposes, it is desirable to maximize the efficiency – not so much to conserve ship’s power as to reduce the cooling requirements for the laser system. The proposed solution should indicate the expected power conversion efficiency and show that this efficiency serves the objectives of the proposed solution. The efficiency is here defined as the transmitted average laser beam power divided by the average input electrical power drawn by the laser system. The requirement for this topic is strictly the laser system; aiming and positioning systems such as gimbals are not part of the desired technology. 

PHASE I: Define and develop a concept for a LWIR laser system meeting the objectives provided in the description above. Demonstrate the feasibility of its concept in meeting Navy needs and establish that the laser system can be feasibly produced. Feasibility will be established by a combination of initial concept design, analysis, and modeling. The Phase I Option, if awarded, will include the initial design specifications and capabilities description to build a prototype in Phase II. Develop a Phase II plan. 

PHASE II: Based on the Phase I results and the Phase II Statement of Work (SOW), design, develop, test, and deliver a prototype LWIR laser system for evaluation and demonstration that it meets the parameters in the description. The demonstration will take place at a Government- or company-provided facility. Provide an affordability analysis that proposes best-practice manufacturing methods to prepare the laser technology for Phase III transition. Prepare a Phase III development plan to transition the technology for Navy production and other potential military uses. 

PHASE III: Support the Navy in transitioning the technology to the Combined electro-optic and infrared (EO/IR) Surveillance and Response System (CESARS) architecture for further experimentation and refinement. The LWIR laser system implementation will be a fully functional system that can be added to the CESARS architecture. Produce/license the final product and provide for insertion into CESARS and acquisition programs resulting from CESARS in partnership with the acquisition program prime contractor. LWIR laser technology, as sought for this effort, is primarily applicable to military applications. However, the range of potential military applications is wide. The commercial applications of this technology are primarily in scientific and instrumentation areas such as materials research and spectroscopy. 

REFERENCES: 

1: Sanchez-Rubio, Antonio. "Wavelength Beam-Combined Laser Diode Arrays." MIT Lincoln Laboratory Tech Notes, 2012. https://www.ll.mit.edu/publications/technotes/TechNote_beamcombining.pdf

2:  Mecherle, G. Stephen. "Laser diode combining for free space optical communication." Proc. SPIE 0616, Optical Technologies for Communication Satellite Applications, 281 (May 15, 1986)

3:  doi:10.1117/12.961064. http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1241781

4:  Fan, T. Y. "Laser beam combining for high-power, high-radiance sources." IEEE Journal of Selective Topics in Quantum Electronics, 11, 2005, 567-577. http://ieeexplore.ieee.org/document/1516122/

5:  Leger, J. R., et al. (editors). "Special Issue on Laser Beam Combining and Fiber Laser Systems." IEEE Journal of Selected Topics in Quantum Electronics, Vol. 15, No. 2, March/April 2009. http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4799145

KEYWORDS: LWIR Laser; IR Sensors; LWIR Propagation; IR Countermeasure; Beam Combining; Laser Source 

CONTACT(S): 

Myron Pauli 

(202) 404-7675 

myron.pauli@nrl.navy.mil 

Hector Martin 

(202) 767-6081 

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