High stability airborne CO2lasers

The construction and field test results of a 50 Watt sealed-off and a 100 Watt flowing airborne CO2laser of high frequency stability are described. A short-term stability of 10¹⁰and a long-term stability of 10⁸has been achieved. The lasers feature: • Cavity construction of ultra-low expansion quartz (ULE-quartz) with a thermal expansion coefficient of 2 × 10^-8(°C^-1). • Internal mirror system with angular alignment and piezoelectric frequency adjustment. • Folded plasma tube construction for rigidity and compactness. • Diffraction limited TEM∞mode oscillation and linear polarization due to folding. The appearance of the specific rotation-vibration transitions as a function of cavity length has been experimentally determined for the two airborne devices and a series of similar devices ranging in cavity length from 35 cm to 275 cm. The results indicate that the number of lines is inversely proportional to the cavity length and the width of oscillation of a specific transition is constant and independent of the cavity length.