Title: Integrated Micro-Photonics for Remote Earth Science Sensing Lidar (IMPRESS)
Presenting Author: Joseph Fridlander
Organization: UCSB
Co-Author(s): Jonathan Klamkin, Larry Coldren, Mark Stephen, Jefferey Chen, Stephan Kawa, Kenji Numata, Joseph Fridlander, Victoria Rosborough, Fengqiao Sang

We will present updates and future work on the development of a photonic integrated circuit (PIC) for active sensing of CO2 emissions. Goddard Space Flight Center has spent several years developing an atmospheric CO2 sensor based on laser spectroscopy that uses a tunable laser to scan through a CO2 gas absorption centered at 1572 nm. The current laser transmitter implementation uses mature technologies and meets all the optical performance requirements but is relatively bulky and inefficient compared to an integrated photonic solution. The seed laser being developed is a pulsed laser with tunable wavelength output. Consecutive pulses are emitted at different wavelengths that step across the absorption feature of interest. The wavelength of each pulse is individually locked to an exact value. This is achieved by using a master laser locked to the center of the CO2 absorption as an absolute reference and using offset locking to tune a slave laser by means of an optical phase-locked loop (OPLL). Our designed PIC variants are fabricated on a monolithic indium phosphide integration platform. The main integrated design elements on chip include a distributed feedback master laser diode, a phase modulator, a sampled grating distributed Bragg reflector slave laser diode, a Mach-Zehnder modulator, a semiconductor optical amplifier, a high-speed photodiode, and directional and multi-mode-interference couplers. The first-generation PICs have been fabricated at UCSB and measurements show lasers are successfully lasing and widely tunable at 1572 nm. Further characterization of individual PIC devices are ongoing and full system measurements are expected to begin soon. At the same time electronic circuitry is being developed to demonstrate a flight capable system for a satellite platform such as a CubeSat. The PIC architecture is also suitable for gas spectroscopy at other wavelengths.