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High Power MegaWatt (MW) Class Grating for High Energy Laser (HEL) System


RT&L FOCUS AREA(S): Directed energy


The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop a new high peak power broad bandwidth efficient diffraction grating for MegaWatt (MW) class continuous wavelength (CW) and ultrashort pulse laser (USP) technology.

DESCRIPTION: High efficiency Volume Bragg Gratings (VBGs) in photo-thermo-refractive (PTR) glass provide unmatched optical filtering capabilities with optical densities as high as 50 dB and linewidths as narrow as 1 cm-1. In this area, the Navy has reviewed recent advances in VBG technologies that enabled key improvements of high efficiency grating properties and led to development of unique VBG-based optical filters for RAMAN spectroscopy and other applications. Currently commercial VBG operates with laser beams that have only narrow band (< 1 nm) linewidth for spectral beam combination At present narrow linewidth (< 1 nm) KW class CW laser are very expensive.. Broad linewidths around 5 nm are more stable and cost-effective. Spectral beam combination (SBC) using current VBG is limited to its operating at spectral range. The proposed broadband VBG can combine multi wavelengths within 200nm bandwidth and has the potential to increase power > MW in a very cost-effective approach to fabricate high-energy laser (HEL) for navy battle space supremacy. The proposed broadband grating (> 200 nm) shall be able to increase laser power greater than MW class using spectral beam combination and shall also have high damage threshold to compress the high peak power (> GW) femtosecond laser.

VBGs in photo-thermo-reflective (PTR) glass has been used for various applications, such as longitudinal and transverse mode selection in diode, solid-state laser resonators, stretchers and compressors for picosecond and femtosecond lasers, and mirrors for high brightness dense spectral beam combining angular beam deflectors/magnifiers. Theoretical and experimental studies of VBGs, their properties and the possibility to make much thicker VBGs in PTR glass compared to polymer-based materials or thin oxide and semiconductor films allow for fabrication of optical filters with linewidths orders of magnitude narrower than those by other techniques.

Volume Bragg Gratings (VBGs) have become an essential component of high-power laser technologies by allowing SBC, stretching and compression of ultrashort laser pulses, frequency stabilization, etc. An innovative compact efficient VBG technology has potential applications due to its high efficiency and high-power laser-radiation damage threshold. However, their high efficiency is limited to a narrow spectral bandwidth, and is typically accompanied by a narrow angular bandwidth.

The Navy seeks an innovative compact, efficient high-power Volume Bragg Grating (VBG) that could exhibit near 99% optical efficiency in broad bands of spectrum (> 200 nm) at 1 to 2 µm optical wavelength. Of particular interest are infrared operation wavelength with a broad spectral range of angles, which can be inexpensively manufactured (i.e., using affordable standard optical material processing equipment’s and affordability that does not required any special manufacturing process and equipment) in sizes exceeding 200mm. The technology has to offer the versatility of controlling the spectral bandwidth of diffraction for adaptation to specific application needs. Emerging grating technologies such as diffractive wave plates and metamaterials appear promising for the technology objectives. The Navy seeks the inclusion of recent advances in VBG technologies or any new innovation that shall meet the proposed volume of around 4 inch3, and ease of manufacturing that enable fabrication of very high efficiency (> 90%) reflecting gratings with broad linewidth >200nm at 1 to 2µm wavelength.

Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. Owned and Operated with no Foreign Influence as defined by DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been be implemented and approved by the Defense Counterintelligence Security Agency (DCSA). The selected contractor and/or subcontractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract as set forth by DCSA and NAVSEA in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advance phases of this contract.

PHASE I: Develop a concept for an innovative, spectral and angular broadband, high diffraction efficiency grating technology that will support ultrafast lasers for pico second/femto second pulse compressor for > 10 mJ pulses at kHz repetition rate or spectral beam combining MW class high energy laser (HEL). Demonstrate the feasibility of the technology for scaling to large area. Through modeling and simulation, demonstrate the feasibility for combining spectrally broadband laser beams > 200 nm. The Phase I Option, if exercised, will include a proposed design that will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Develop the required technology and incorporate it into a prototype device for high power CW laser Spectral beam combining (SBC) and for ultrafast lasers CPA beam compression technology. Demonstrate that the technology meets the requirements as described. Perform SBC and high power testing for beam combination, and peak power pulse compression to generate GW class of pulse femtosecond laser. Follow on testing will refine the prototype into technology for operational use. Deliver the prototype diffraction grating for the purpose of femtosecond pulse compression or SBC of MW class laser system. Deliver the prototype VBG for -MW class CW HEL SBC and femtosecond laser > 10 mJ per pulse beam compression and evaluation of its power and EO efficiency in a HEL prototype system that can meet Navy performance goals (> 200 nm spectral bandwidth) by the US Navy.

It is probable that the work under this effort will be classified under Phase II (see Description section for details).

PHASE III DUAL USE APPLICATIONS: Assist the Navy to transition the Phase II prototype of the high power compact efficient broad linewidth VBG to Navy use for the purpose of HEL technology integration at 1 to 2 um MW class laser. Assist in the integration of the laser system into a submarine or other Navy platform to advance the future Navy warfighting capability. Transition this technology into commercial markets, such as automobile and aircraft industries that employ very high power lasers for cutting, drilling, and welding applications.


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