Temperature and pulse-duration dependence of second-harmonic generation in CdGeAs2

Area of Science:

• Optics and Photonics
• Laser Physics
• Nonlinear Optics

Background:

• Carbon dioxide (CO2) lasers are crucial sources for mid-wave infrared (MWIR) applications.
• Frequency doubling is a key technique to access shorter wavelengths from existing laser sources.
• CdGeAs2 is a nonlinear optical crystal with potential for infrared frequency conversion.

Purpose of the Study:

• To investigate and optimize the frequency doubling process of a transversely excited atmospheric (TEA) CO2 laser.
• To determine the optimal operating temperature for maximizing frequency-doubled energy output.
• To characterize the temporal properties and peak power of the generated second-harmonic beam.

Main Methods:

• A TEA CO2 laser operating at 9.55 microm was used as the fundamental source.
• A CdGeAs2 nonlinear crystal was employed for frequency doubling.
• The crystal temperature was systematically varied from 80 K to 295 K.
• The temporal profile of the frequency-doubled beam at 4.775 microm was analyzed to determine peak power.

Main Results:

• Optimized frequency doubling of the CO2 laser was achieved using the CdGeAs2 crystal.
• Maximum mid-wave infrared pulse energy of 16.65 mJ was obtained.
• A peak power of 92 kW was measured for the frequency-doubled output at 4.775 microm.
• The study identified optimal temperature ranges for efficient frequency conversion.

Conclusions:

• The frequency doubling of a TEA CO2 laser at 9.55 microm using CdGeAs2 is an effective method for generating MWIR radiation at 4.775 microm.
• The achieved high pulse energy and peak power demonstrate the suitability of this technique for applications like lidar.
• Further optimization may enhance the efficiency and power output for broader technological implementation.