A new way of holding optical fibers is helping the Department of the Air Force (DAF) test and assess integrated photonic devices much more quickly.
Dr. Matt Smith, Dr. Erin Sheridan, and contractors Andrew Brownell and Nick Barton – all of whom are affiliated with the Air Force Research Laboratory (AFRL) Information Directorate (RI) – recently received a patent from the U.S. Patent and Trademark Office related to the placement of optical fibers on these devices. The patented innovation uses 3-D printing technology to create a structure with an embedded vacuum channel matching the 125-micrometer radius of an optical fiber. One micrometer is one one-millionth of a meter. The inclusion of the vacuum channel allows optical fibers to be held in place with a vacuum until placement is complete.
“Integrated photonic devices” are optical chips that function like electrical circuits, but that use light instead of electricity. They consist of silicon waveguides or closely related materials and have varied applications to a wide variety of fields, such as quantum optics, communications, sensing, and Light Detection and Ranging (LiDAR). Quantum optics approaches, for example, use single photons to encode information in a quantum state, facilitating secure, tamper-proof communications. Using integrated photonic devices can reduce the Size, Weight, and Power (SWAP) of many existing optical systems; it can also enable new applications.
However, using integrated photonic devices in the field requires that they be “packaged” in a robust way that allows light signals to be inserted and extracted from them. The packaging process entails attaching optical fibers to the chips, which then allows the devices to interface with other systems, such as a telecommunications network. The fibers must be glued to the chips, and the fibers must be placed within a few micrometers of each other without the fibers or the alignment systems interfering with each other. While being glued to the device, the fibers must be precisely and exactly held to ensure accurate placement.
As one might imagine, the precision required is difficult to achieve and, in the past, has been accomplished by employing bulky items such as fiber arrays and mechanical grippers. The simplest approach involves taping fibers to bulky metal arms. The arms are positioned beside the chip while fibers are glued to the chip, and then the arms are removed. Using this method limits the number of fibers that could be used at a time. In addition to the general clunkiness involved, removing the fiber from the metal arm without breaking the fiber or its connection to the chip also requires diligent care. As a result, the packaging process has, in the past, therefore often been painstaking, time-consuming, and prone to failure.
The RI team’s innovation, however, uses 3-D printing methods to create novel positioning arms designed to facilitate easier placement of fibers without interference. These structures are printed with embedded vacuum channels, which are customizable to fit the radius of the fiber, the minimum spacing between fibers, and the edge facets of the chip. Fibers can be easily placed and held against these vacuum channels. The fibers are held in place only by the vacuum force, so once they have been successfully attached to the chip, it is very easy to release the vacuum and remove the fiber from the 3-D printed arm without worrying that connection will be damaged. Overall, then, the RI team’s invention makes the packaging process faster and simpler to complete than before.
As a result, DAF’s mission may be accelerated. DAF has applications for integrated photonic devices in a wide array of aircraft, drones, terrestrial long-haul communication networks, and other optical systems. Maintaining a technological advantage over adversaries requires that DAF continually test and assess new chips in a rapidly evolving technology landscape. The patented technology allows DAF to package integrated photonic devices far more quickly and take them into the field for practical testing. As a result, DAF will be able to pursue key mission objectives more efficiently and more easily than before.
Additionally, as Dr. Smith noted, this technology will likely have many applications to other use cases in industry and academia, as packaged integrated photonic devices are becoming quite ubiquitous in today’s world. They are used in devices ranging from LiDAR for self-driving cars to optical transceivers for high-speed internet. By statute, federal laboratories are required to promote the widest possible application of taxpayer-funded discoveries, and the RI team’s achievement will go a long way in meeting this obligation.
The RI team’s patent application was facilitated by RI’s Office of Research and Technology Application (ORTA). DAF ORTAs protect DAF’s interests in new discoveries achieved in DAF research laboratories. DAF ORTAs work with DAF scientists and engineers to navigate the patent application and issuance process, ensuring that DAF’s intellectual property interests are preserved. After patent issuance, many technologies are licensed to external entities for further development, and DAF ORTAs also facilitate this process. DAF ORTAs coordinate their activities with the DAF Technology Transfer and Transition (T3) Program Office, which oversees individual ORTAs and performs ORTA functions for DAF laboratories lacking a designated ORTA.
United States Patent and Trademark Office Patent # 12,523,822
About AFRL
The Air Force Research Laboratory, or AFRL, is the primary scientific research and development center for the Department of the Air Force. AFRL plays an integral role in leading the discovery, development, and integration of affordable warfighting technologies for our air, space, and cyberspace forces. With a workforce spanning across nine technology areas and 40 other operations around the globe, AFRL provides a diverse portfolio of science and technology ranging from fundamental to advanced research and technology development. For more information, visit www.afresearchlab.com.