Lasing without Gain Inertial Sensors

Non-Hermitian coupled-resonators (CRs) have demonstrated increases in sensitivity of ~1000, which could enable more rapid and precise inertial measurements, with smaller sensors, translating to greater spacecraft autonomy. One subclass of these utilizes an atomic fast-light medium inside a laser cavity, but are restricted to the transition wavelength of the medium and are not easily miniaturized. A second subclass consists of arrays of microresonators that possess parity-time (PT) symmetry. These are easily microfabricated and operate at any lasing wavelength, but display power oscillations and are susceptible to laser intensity noise. But we have found that by breaking PT-symmetry, lasing occurs even though the sum of the gain coefficients is negative. These lasing without gain (LWG) gyros can be made to operate without the power oscillations and sensitivity to intensity fluctuations. Proof-of-principle CIF results have demonstrated the LWG concept in a linear Helium-Neon CR system and in this TIP we are developing an LWG gyro.

Address a critical need for improved onboard autonomous navigation technologies to support next-generation space missions, in particular for minimization of mass, power and volume while increasing performance, avoiding navigation from becoming a constraint in planning and executing missions, and eliminating Earth from the real time decision loop. The benefit is that a measurement made at a particular measurement rate for a particular size gyro could be more precise. So faster, more precise measurements can be made, with smaller gyros. The greatest benefits would be in situations requiring rapid changes in attitude or position, or where knowledge of the environment may be limited or obscured. Such scenarios include entry, descent, and landing, surface operations with rovers, formation flying or automated rendezvous and docking, and missions to small bodies including sample return and kinetic impactor missions. The increase in precision translates to reduced error ellipses that would enable pinpoint landings for improved access to engineering and mining needs as well as to more interesting and complex science targets. With sufficient advancement, lasing without gain (LWG) inertial measurement units (IMUs) could be incorporated into lunar, Martian, Europa, and other landers. They would work in conjunction with terrain-relative navigation technologies such as LIDAR camera-based systems to provide an overall solution for precision landings. LWG IMUs, however, do not rely on external signals, and so could potentially enable precision landings even in conditions that obscure these other methods. LWG IMUs could also be markedly faster than these other technologies, providing tighter controls when necessary. In addition, LWG inertial sensors are well suited to microfabrication, so their mass, volume, and power could potentially be a fraction that of commonly-used IMUs. Applications for national defense include smart munitions, missiles, and UAVs operating in GPS-denied environments. In addition to the navigation benefits, this work could open up new science possibilities such as improved measurements of fundamental physical constants, ground-based measurements of the general relativity Lense-Thirring frame-dragging effect, and enhancement of the sensitivity-bandwidth product for interferometric gravitational wave detectors.

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