Theoretical prediction on the wavelength–temperature shift in pulsed TE CO2 lasers

The wavelength–temperature shift observed in pulsed TE CO2 lasers is discussed theoretically by means of Six-temperature model rate equations for tunable TE CO2 lasers. Numerical calculations of the temperature–wavelength shift in a pulsed TE CO2 laser with a simple plano-concave stable resonator, whether excited by conventional low-inductance fast-discharge scheme or by a long-pulse Pulser/sustainer discharge scheme, show that the laser output wavelengths are within the 10P branch as the ambient temperature varies from 228 to 338 K, but will change as the ambient temperature varies. The laser output wavelengths will move to the transition lines with longer wavelengths in the 10P branch as the ambient temperature increases and vice versa. The calculated results also illustrate that near the ambient temperature of 310 K, the laser is more likely to operate on multi-transition lines. Considering this wavelength–temperature shift, the chilling device adopted in high-power high repetition rate TE CO2 lasers is important in maintaining a stable laser output spectra as well as a stable laser output power. The numerical results also suggest that a frequency agile resonator is highly recommended if stable laser output spectra are required in TE CO2 lasers.