N212-D05 TITLE: DIRECT TO PHASE II – Yield Increase for High-Performance Optical Interference Filters

RT&L FOCUS AREA(S): General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Materials / Processes

OBJECTIVE: Develop processing and manufacturing techniques to significantly improve the yield of high-performance optical interference filter systems, thus reducing unit cost.

DESCRIPTION: Currently optical receiver systems use low to moderate performance interference filters to pass the desired wavelength light and block all unwanted wavelength light. As the receiver aperture size increases or the optical performance requirements (i.e., higher transmission, larger acceptance angle, lower bandpass width) increase, the cost of the optical filter increases dramatically. The cost increase is directly related to yield decrease due to limitations in coating uniformity when considering increased piece size or increased performance. For ultra-narrow high performance filters, reducing the non-uniformity to 0.1% and below is required to minimize wavelength shift and bandwidth broadening [Refs 2, 3].

In order to meet the emerging demands of large-aperture high performance optical filters while reducing costs, a system-level approach must be taken. Reducing non-uniformity to 0.01% over a large area is not feasible, but it is feasible to combine multiple high performance pieces into a single system while maintaining high fill factor. A high yield process will be required to reduce overall system cost.

This SBIR topic focuses on the development of a high yield, lower unit cost process for large area state-of-the-art (SOA) optical interference filter systems in the visible light spectrum. Filter performance goals for a filter line in the 460 to 490 nanometer range: 0.1 nm bandwidth, +/- 30 milli-iadianl acceptance angle, > 80% in-band system transmission, and > 4 orders of out of band blocking. Use MIL-STD-810 [Ref 1] for guidance on environmental storage and operating conditions.

PHASE I: For a Direct to Phase II topic, NAVAIR expects that the small business would have accomplished the following in a Phase I-type effort. It must have developed a concept for a workable prototype or design to address—at a minimum—the basic requirements of the stated objective above. The below actions would be required in order to successfully satisfy the requirements of Phase I:

• Developed a process to manufacture high-performance optical interference filter systems [Ref 4].
• Manufactured high-performance optical filter systems [Ref 4].
• Understood limitations of current processes, and identified methods and techniques to improve performance and yield of optical filter systems.

FEASIBILITY DOCUMENTATION: Proposers interested in participating in Direct to Phase II must include in their responses to this topic Phase I feasibility documentation that substantiates the scientific and technical merit and Phase I feasibility described in Phase I above has been met (i.e., the small business must have performed Phase I-type research and development related to the topic, but feasibility documentation MUST NOT be solely based on work performed under prior or ongoing federally funded SBIR/STTR work ) and describe the potential commercialization applications. The documentation provided must validate that the proposer has completed development of technology as stated in Phase I above. Documentation should include all relevant information including, but not limited to: technical reports, test data, prototype designs/models, and performance goals/results. Work submitted within the feasibility documentation must have been substantially performed by the proposer and/or the principal investigator (PI). Read and follow all of the DON SBIR 212 Direct to Phase II BAA Instructions. Phase I Proposals will NOT be accepted for this BAA.

PHASE II: Based upon the work described in the Feasibility Documentation, develop and implement a process to consistently provide high-yield, high-performance filter systems. Demonstrate process success by providing a high-performance 100 mm diameter filter system prototype with a center wavelength in the 460 to 490 nm range, 0.1 nm bandpass, +/-30 mil acceptance angle, average in-band transmission of greater than 80%, and greater than 4 orders of out-of-band blocking. During the option period, if exercised, produce a large diameter (300 mm) prototype filter system with the same or better performance as the base demonstration unit, and demonstrate the feasibility of low-volume (10) unit costs of less than $50,000.

PHASE III DUAL USE APPLICATIONS: Finalize the prototype, providing optical filter systems tailored to existing, or new, active and passive optical systems, as well as, provide integration assistance. Perform environmental testing consistent with various platform requirements and provide test results.

High-performance, low-cost optical filter systems can directly improve the performance of existing commercial LIDAR systems. Subcomponents of the filter system can be applied to short range lidar systems being considered for the autonomous automobile market, where unit cost at minimum performance is key.

REFERENCES:

1. "MIL-STD-810H, Department of Defense test method standard: Environmental engineering considerations and laboratory tests." Department of Defense, US Army Test and Evaluation Command, January 31, 2019. http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810H_55998/.
2. Macleod, H. A. "Chapter 11: Other topics: from rugate filters to photonic crystals." Thin-film optical filters (4th ed.), CRC Press, 2001. https://www.amazon.com/Thin-Film-Optical-Filters-Optics-Optoelectronics/dp/1420073028.
3. Rahmlow, T., Upton, T., Fredell, M., Finnell, T., Washkevich, S., Winchester, K., Hoppock, T. and Johnson, R. "Ultra-narrow bandpass coatings for deep space optical communications (DSOC) [Figure 9]. Omega Optical, Inc., September 13, 2017, p. 6. https://www.nasa.gov/sites/default/files/atoms/files/12_omega_optical_ultra_narrow_bandpass_coating_for_dsoc.pdf.
4. Johansen, A., Czajkowski, A., Scobey, M., Egerton, P. and Fortenberry, R. "Thin-film interference filters for LIDAR." Alluxa, April 9, 2017. https://www.alluxa.com/learning-center/white-papers/thin-film-interference-filters-for-lidar/.

KEYWORDS: Optical filter; high yield; narrowband; interference filter; thin-film; lidar