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Semiconductor Lasers

In 2010, the SemiconductorLasers Group designed and fabricated record high-power

MDL Fabricates Record High-Power, Single-Spatial-Mode Lasers at ~2.05 µm

The NRC Committee on Earth Science and Applications from Space has recommended the proposed Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission to produce global atmospheric column CO2 measurements using laser remote sensing of CO2, with the goal of enhancing understanding of the role of this gas in the global carbon cycle. The sensitivity analysis for space-based CO2 LIDAR measurements has identified transitions in the 1.57- and 2.05-μm absorption bands that are suitable for making global measurements of CO2. Though both wavelengths could be used for this measurement, JPL has adopted the 2.05 μm absorption line as a long-term preference due to significantly larger CO2 absorption line strength and significantly less water absorption interference.

Close up view of a junction side up 2-mm laser.

The current laser transmitter used in JPL’s Laser Absorption Spectrometer instrument uses optically pumped solid-state lasers for both the seed and the amplifier. Replacement of the seed laser with a monolithic semiconductor laser would greatly improve the instrument stability and long-term reliability. In collaboration with the State University of New York at Stony Brook, we are investigating the viability of GaSb-based laterally coupled distributed feedback lasers as injection seeds.

In 2010, MDL researchers designed and fabricated record high-power, single-spatial-mode diode lasers operating near 2.05 µm with room-temperature continuous-wave output power exceeding 100 mW. In spite of the low thermal conductivity of the GaSb substrate, the junction-side-up mounted lasers have low thermal resistance of 22 K/W and CW characteristic temperature of 107 K.

Above: CW light-current-voltage (LIV) characteristics of laser at 10, 25, and 40°C