Difference Frequency Generation and Gas Sensing
Difference frequency generation (DFG) is a means of creating a longer wavelength of light by combining two shorter wavelengths within a non-linear crystal. This approach is most commonly utilized for creating a narrow wavelength for gas sensing applications. Typically, this is utilized in the 1.5-4 um wavelength range for common gases such as CO, CO2, CH4, N2O, and H2O.
Frequency stabilized lasers from IPS are utilized for the “fixed” laser source since the laser wavelength is extremely stable and can be precisely specified. This allows the customer to accurately select the “scanning” laser source wavelength to scan the desired DFG wavelength band by temperature tuning.
Gas sensing applications are generally based on absorption spectroscopy techniques where the DFG wavelength attenuation is measured within a multi-pass gas cell. Accordingly, power and wavelength stability are critical performance characteristics for both the fixed and tunable laser sources for which IPS lasers are ideal.