Atmospheric methane trends over the last few years have been increasing at a rate of 7-12 parts per billion (ppb) per year after brief a pause in the first decade of this century. The reasons for the pause and subsequent increase remains unclear. Thus, there is a critical need for additional, precise and accurate methane observations to understand the natural and anthropogenic processes that drive the trends in atmospheric methane and to constrain its sources, and sinks. At NASA Goddard Space Flight Center (GSFC), in collaboration with Freedom Photonics Inc., we have been developing a lidar to measure atmospheric methane using Integrated Path Differential Absorption (IPDA) from an airborne platform as a precursor to a future space mission. In this paper we present the design of a laser transmitter operating at ~1651 nm based on a newly developed Distributed Bragg Grating (DBR) seed laser and an Optical parametric oscillator (OPO). The DBR is rapidly step-tuned over the methane absorption at several discrete wavelengths. This multi-wavelength approach enables us to sample the entire methane lineshape and reduce systematic errors.
The use of photonic integrated circuits and components in many areas across the general area of laser systems is increasing. Example applications of such systems include free space optical communication, remote standoff sensing, solid state and fiber laser pumping, LIDAR for autonomous vehicles, and atomic laser systems for position, navigation, and timing. In this talk we will review the design, performance, and robustness of Freedom Photonics high performance integrated photonic components for these applications and others, focusing in particular on recent advancements in our products at 780 nm, 1060 nm, 1310 nm, and at 1550 nm.
High power, high efficiency diode lasers operating in the 15xx nm wavelength range are needed for a variety of applications, including eye-safe infrared illuminators and resonant diode pumps for Erbium-based high energy laser systems. We have demonstrated high power, high efficiency lasers at 1532 nm with integrated wavelength control. We have engineered the epitaxial structure in InP to mitigate losses and to include a buried distributed feedback (DFB) grating layer for wavelength control.
We have demonstrated 15xx nm lasers generating >3 W at 36% EO efficiency. We have also demonstrated multi-Watt DFB broad area lasers with >99% of the power concentrated in a narrow spectral width <1 nm. These lasers are being packaged into fiber-coupled modules.
Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with approximately 25 times the radiative forcing of carbon dioxide (CO2) per molecule. CH4 also contributes to pollution in the lower atmosphere through chemical reactions leading to ozone production. Recent developments of LIDAR measurement technology for CH4 have been previously reported by Goddard Space Flight Center (GSFC). In this paper, we report on a novel, high-performance tunable semiconductor laser technology developed by Freedom Photonics for the 1650nm wavelength range operation, and for LIDAR detection of CH4. Devices described are monolithic, with simple control, and compatible with low-cost fabrication techniques. We present 3 different types of tunable lasers implemented for this application.