Measuring global winds from space using eye-safe coherent laser radar is an important on-going NASA technology and instrument development effort that will ultimately improve the fidelity of meteorological climate models, near-term weather forecasting, and commercial aviation management and optimization. Activities like NASA LaRC’s “Wind-SP” coherent lidar program are pushing these laser and lidar technologies forward with regard to high-energy eye-safe transmitter lasers, low-noise fast-tunable master and local oscillator lasers, and active optical alignment and lag-angle compensation functionalities specific to space-based applications. Currently critical extended-wavelength (e.g. 2.05 mm sensitive) InGaAs photodiode/photoreceiver technology is mature enough to supply devices necessary for efficient lidar signal capture, but only at lower detection bandwidths that in turn require complicated and expensive photonic solutions to handle the multi-GHz platform-induced Doppler shifts experienced in a low-earth-orbit application. In this Phase I/Phase II effort we propose to push the performance of such coherent lidar signal photoreceivers to a level that would completely eliminate the need for complex master/local oscillator laser offset-locking subsystems that are currently required to compensate for the large frequency offsets from a space platform. This innovation will significantly lower the lidar system complexity, cost, size, weight, and electrical power requirements of future wind lidars from space, greatly improving the flexibility of deployment in terms of feasible launch vehicles and satellite platforms. In Phase I we will work with partner Discovery Semiconductors Inc. to develop and test early prototypes and identify the most appropriate path toward realization of such wideband, high-quantum-efficiency InGaAs devices, and produce optimal devices and associated lower-complexity coherent lidar system architecture in Phase II.
Potential NASA Applications of the proposed extended-wavelength wide-band high-efficiency lidar photoreceiver technology include on-going and future measurement of global winds from space; ground-based and airborne coherent lidar programs; eye-safe remote laser spectroscopy applications for measurement of atmospheric constituents like CO2, water vapor, and methane; and other shortwave-IR wavelength instrument developments requiring wide-band photon-counting-sensitive coherent detection in the 1.5-to-2.0 micron wavelength region.
Development of high-QE, wide-bandwidth extended-InGaAs photodiodes/photoreceivers optimized for heterodyne detection would find immediate use in DoD laser remote sensing applications for identifying and tracking very fast-moving hard targets. Beyond Photonics is developing commercial wind lidar products that would use such devices. IR laser spectroscopy and instrument development would benefit.