N251-073 TITLE: Robust Fiber-to-Photonic Integrated Circuits (PIC) Coupling for the Near-Infrared (NIR)

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Microelectronics;Quantum Science;Space Technology

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: Develop a robust method of achieving efficient optical coupling between PICs and single mode optical fiber operating at NIR wavelengths relevant for quantum sensing (700 nm to 900 nm).

DESCRIPTION: Atomic accelerometers and clocks are important elements of advanced inertial navigation and timing systems. In recent years, there has been significant effort to reduce the size, weight, and power (SWaP) of various subsystems. For the laser subsystem in particular, this is typically anticipated to be accomplished by a transition from bulk optics to PICs [Ref 1].

One challenge of this transition is the efficient on- and off-coupling of light between PICs and off chip components such as laser sources and sensor elements such as vapor cells. Single-mode polarization-maintaining fiber provides a convenient mode of transferring light between subcomponents because it maintains optical mode quality and decouples the mechanical interface between subcomponents. It is also crucial in the testing and development of subcomponents, as it enables light to be coupled to external instruments for analysis and component testing.

Mature processes exist for robust fiber attachment at telecommunications wavelengths [Refs 2, 3]. These include grating coupling, prism coupling, and edge coupling into tapered waveguides. Active alignment techniques involving the attachment of one fiber at a time ensure coupling efficiency but at the expense of being labor intensive. Passive and multi-fiber alignment techniques may reduce labor at the expense of reduced coupling efficiency. While coupling losses on the order of 1 dB are achievable at telecom wavelengths, losses at wavelengths relevant for quantum sensing (700 nm to 900 nm) are typically less efficient. Quantum sensors often utilize high optical powers (up to 1 W), which impacts the robustness of fiber interconnects and demands greater efficiencies. The goal of this SBIR topic is to develop robust PIC to fiber connections that are labor efficient, optical power efficient, and robust to high power operation.

Target specifications for the desired process include:

• Optical power handling: Up to 1 W continuous wave

• Optical wavelength: 700 nm to 900 nm (any photonic architecture compatible with this range is acceptable for demonstration purposes)

• Fiber type: Single mode polarization maintaining

• Coupling loss: 1 dB

PHASE I: Perform a design and materials study to assess the feasibility of the proposed technology or process to meet the target specifications listed in the description. Prepare a final report that must include an assessment of:

• The SWaP implications of the proposed technique (particularly the size and density of fiber connections)

• A discussion of the technology’s compatibility with PIC architectures

• The scalability of the approach and the labor involved in making fiber connections both for an envisioned production environment for low quantity prototypes, low rate production, and full rate production

The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a PIC-fiber attachments in Phase II.

PHASE II: Demonstrate the proposed fiber attachment technique and characterize its performance against the target goals listed in the Description. At the conclusion of Phase II, deliver five (5) representative photonic chips demonstrating fiber attachments on both the input and output of a waveguide.

PHASE III DUAL USE APPLICATIONS: Continue development to assist the Government in integrating the technology with other PIC components.

In addition to advancing a quantum sensing capability for military/strategic applications, this technology will improve the SWaP and lower the development cost of commercial photonic components that utilize wavelengths down to the visible spectrum, including, Light Detection and Ranging (LIDAR) systems, spectrometers, data communications, and quantum technologies.

REFERENCES:

1. Sanna, Matteo; Baldazzi, Alessio; Piccoli, Gioele; Azzini, Stefano; Ghulinyan, Mher and Lorenzo Pavesi, "SiN integrated photonic components in the visible to near-infrared spectral region." Opt. Express 32, 2024, pp. 9081-9094. https://doi.org/10.1364/OE.514505

2. Lu, Z.; Yin, P. and Shi, K. "Bent Metal-Clad Waveguides for Fiber-to-Waveguide and 3D Chip-to-Chip Light Coupling Applications,. Frontiers in Optics 2016, OSA Technical Digest (online), Optica Publishing Group, paper JTh2A.161. https://doi.org/10.1364/FIO.2016.JTh2A.161

3. Nauriyal, Juniyali; Song, Meiting; Zhang, Yi; Granados-Baez, Marissa and Cardenas, Jaime. "Fiber array to chip attach using laser fusion splicing for low loss." Opt. Express 31, 2023, pp, 21863-21869. https://doi.org/10.1364/OE.492752

KEYWORDS: Photonic integrated circuit; PIC; optical fiber interconnect; silicon nitride photonics; optical fiber attachment; grating coupler; edge coupler

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