GPS World, September 2018

Inertial Ranging eLoran Wi Fi Bluetooth CLOCKS AND GYROS T he U S Defense Advanced DARPA Wants Photonic Integrated Circuits Research Projects Agency DARPA Microsystems Technology Office is soliciting research proposals for the development of a new class of atom based systems using integrated photonics and trapped atoms to enable high performance robust portable clocks and gyroscopes The military researchers are asking industry to develop relatively simple portable photonic integrated circuits PICs for high performance position navigation and timing PNT devices as an alternative to GPS for when satnav signals are not available A PIC or integrated optical circuit similar to an electronic integrated circuit integrates multiple photonic having to do with light functions providing capabilities for information signals imposed on optical wavelengths typically in the visible spectrum or near infrared 850 1650 nanometers A PhI Program The Atomic Photonic Integration A PhI program seeks to develop trapped atom based highperformance PNT devices reducing the complexity of these atomic systems by using PICs According to the DARPA document the PICs will replace the optical assembly behind devices such as sensitive and accurate angle sensors and clocks while still enabling the necessary trapping cooling manipulation and interrogation of atoms A PhI aims to demonstrate that compact PICs can replace the optical bench of conventional free space optics for high performance trapped atom gyroscopes and trapped atom clocks without degrading the performance of the underlying physics package Physics Atomic systems using trapped atoms have the potential to be made portable while maintaining their accuracy due to the atomic traps small size and the inherent isolation a trap offers an atomic system from the environment especially from acceleration Currently these systems are bulky heavy and not notably portable because of the complexity of the optical systems used to create the trap In the past efforts to miniaturize the hundreds to thousands of optical components in such benchtop systems have relied on removing optical elements miniaturizing the remaining elements and tightly integrating them in a small package The products deliver degraded performance with the need to maintain very tight optical alignment causing both poor environmental robustness and poor tolerance to design errors Effective miniaturized atomic systems cannot be achieved at a reasonable cost with this approach Recent developments in PIC research suggest that on chip optical frequency combs based on microresonators optical frequency synthesis novel on off chip 12 GPS WORLD WWW GPSWORLD COM SEPTEMBER 2018 coupling wavelength demultiplexers and on chip phased arrays for dynamic manipulation of light fields can replace optical systems with readily manufacturable low cost chips without the alignment sensitivity of conventional free space optics Gyroscopes A PhI also seeks to develop proof of concept trapped atom gyroscopes a matter wave analog of the interferometric fiberoptic gyroscope Such a miniaturization effort could generate an order of magnitude improvement in angular sensitivity and dynamic range over current free space products A PhI hopes to develop portable high performance navigation and timing systems the miniaturization of the optics of atomic systems without a decrease in performance Subsequent work the RFP asserts will be required to incorporate the necessary compact and robust lasers and electronics to achieve a fully functioning highperformance portable PNT system High energy photons emission abstract illustration GiroScience Shutterstock com