N231-075 TITLE: Reduced Integrated Optical Circuits (IOC) Half-wave Voltage (Vpi) for improved Size Weight and Power (SWaP) in Interferometric Fiber-Optic Gyroscopes (IFOG)

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Hypersonics; Microelectronics; Nuclear

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 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: Reduce half-wave voltage (Vpi) in current state-of-the-art Y-branch dual phase modulator integrated optical circuits (IOC) so that they can be packaged in smaller instruments

DESCRIPTION: The performance requirements for strategic-grade inertial sensors based on optical interferometry continue to become more stringent, necessitating continued innovation for optical component technologies that require unprecedented precision and characterization of long-term bias stability, scale factor linearity, angle random walk performance, etc. [Ref 1]. One of these key components is the IOC. The IOC is typically comprised of Y-branch dual phase modulators based on waveguides and electrodes formed on the surface of a crystal, such as lithium niobate, and assembled (pigtailed) to optical fiber (one input and two output fiber ports) [Ref 2]. Current devices are limited in size by the length of the crystal required to produce a PI phase shift. Improvements to Vpi should allow the same phase shift with a shorter length and enable more tightly packaged and integrated fiber optic gyroscopes. The objective of this SBIR topic relates to advanced lithium niobate IOCs for strategic-grade inertial sensors with 1550 nm operating wavelength. The reduced Vpi shall have negligible impact on other IOC design and performance criteria resulting in a reduced overall size, overall optical insertion loss, polarization extinction ratio, and flat frequency response behavior.

PHASE I: Perform a design and materials study aimed at reducing the Vpi and Size, Weight and Power (SWaP) of the lithium niobate IOC. Target Vpi should be significantly below current annealed proton exchange (APE) and reverse proton exchange (RPE) standards which easily achieve < 10V in a 25mm long package. The study must demonstrate that Vpi reduction to an equivalent of 5 V (or lower) in a 25mm long package is feasible. The technique should be compatible with IOCs having either APE or RPE waveguides with 1550 nm operating wavelength. The study must assess performance criteria and consider all aspects of device fabrication. The study shall include a preliminary assessment of long-term environmental stability assuming a design life of 30 years at 50 �C based on a materials physics analysis, including Mean Time Between Failure (MTBF), Mean Time to Failure (MTTF) and Failure In Time (FIT) values, along with identification of the assumptions, methods, activation energy, and confidence levels associated with these values. The study shall justify the feasibility/practicality of the approach for achieving reduced Vpi and SWaP with negligible impact on other IOC design and performance criteria, including overall optical insertion loss and polarization extinction ratio (PER). The study shall estimate the effects of the change to Vpi on IOC design and performance criteria relative to a control prototype design that does not include the new feature. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build prototype solutions in Phase II, as well as a test plan for an accelerated aging study (minimum 5 year real-time equivalent) to be conducted in Phase II.

PHASE II: Based on the Phase I results, design, fabricate, and characterize six (6) prototype IOCs, complete with fiber-optic pigtails and electrical connections suitable for incorporation into test beds for interferometric inertial sensors. Characterization must comprise evaluation electrical measurements including Vpi frequency response and residual intensity modulation (RIM), and optical measurements including optical insertion loss, chip PER, optical return loss (ORL) or coherent backscatter, and wavelength dependent loss (WDL). An accelerated aging study involving IOCs at elevated temperatures under vacuum must be performed to develop a predictive model of long-term environmental stability. The prototypes should be delivered by the end of Phase II.

PHASE III DUAL USE APPLICATIONS: Based on the prototypes developed in Phase II, continuing development must lead to productization of IOCs suitable for interferometric inertial sensors. While this technology is aimed at military/strategic applications, phase modulators are heavily used in many optical circuit applications, including in telecom industry hardware. A phase modulator with significantly reduced SWaP is likely to bring value to many existing commercial applications including LIDAR, satellite free space communications and other radar applications. Also, this technology could be leveraged to bring IFOG technology toward a price point that could make it more attractive to the commercial markets.

REFERENCES:

1.       Adams, Gary, and Gokhale, Michael. "Fiber optic gyro based precision navigation for submarines." Proceedings of the AIAA Guidance, Navigation and Control Conference, Denver, CO, USA, August 2000: 2�6. https://arc.aiaa.org/doi/pdf/10.2514/6.2000-4384

2.       Wooten, Ed L. et al. "A review of lithium niobate modulators for fiber-optic communications systems," IEEE Journal of selected topics in Quantum Electronics 6, January 2000: 69-82. https://ieeexplore.ieee.org/document/826874

 

KEYWORDS: Integrated Optical Circuit; Phase Modulator; Lithium Niobate; Waveguides; Inertial Sensor; Fiber-optic Gyroscope

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