Above:
Close up view of a junction side up 2-mm laser. A copper C-block and eutectic Au/Sn solder was used to attach the die.
2.05 μm Seed Laser
Record-Breaking Seed Laser for Seeing CO2
Mahmood Bagheri - Siamak Forouhar - Clifford Frez
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.
A seed laser is used to control and improve the emission of another 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 investigated the
MDL has demonstrated fiber-coupled distributed-feedback (DFB) semiconductor lasers with record high output power (more than 100 mW) 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. These modules will enable, for the first time, the use of semiconductor diode lasers in injection seeding applications of high-power lidar transmitters for 3D wind measurement and CO2 detection at the preferred wavelength of 2.0 µm and 2.05 µm, respectively.
With the recent progress in the development of optical fiber amplifiers operating near 2.05 µm wavelength, MDL’s high-power fiber-coupled semiconductor laser will be an enabling technology for a myriad of other emerging applications in this wavelength range.
CW light-current-voltage (LIV) characteristics of laser at 10, 25, and 40°C. The emission wavelength at 200 mA is shown the inset.
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In the hermetically sealed package, optical elements with anti-reflection coating layers with a single-stage optical isolator are used to suppress back-reflection into the laser cavity.
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