Powerful Nanosecond Pulses by Stable Passive Mode-Locking of TEA CO₂ Lasers

Abstract

Passive mode-locking of a double-discharge TEA CO2 laser using SF6 as bleachable absorber has been achieved on several rot–vib transitions of the 00°1–10°0 band. Stable pulses shorter than 2 ns and having peak powers in the 100–200 MW range have been regularly obtained. The experimental conditions and operating characteristics of the laser required to achieve stability are described.

Suppression of mode-locking by excited-state absorption in a saturable absorber

“…Such anharmonic effects have been previously reported for sF6 (Oppenheim and Melman 1971) and ethylene (Ressler and Crain 1972). The predicted suppression of mode-locking in the limit that -9 > 0 may be inferred from the earlier experimental work of Fortin et al(1972), in which they report highly stable mode-locking of CO2 laser radiation using SF6 over laser lines PI8 to P26 and significant instability of mode-locking over other laser lines. The vibrational energy-level diagram for sF6 (Burak et a1 1971) with the inclusion of excited-state levels is well approximated by the superposition of the two systems considered in this report with a partial relaxation on the infinitely fast transition v2 --f v3.…”

Increased reliability of passive mode-locking a multi-atmosphere TE CO2 laser by injection mode-locking

“…Passive mode-locking of the TE CO 2 laser has been demonstrated by a number of authors [1][2][3] using several types of saturable absorbers. The shortest pulses have been generated using p-type germanium yielding pulses as short as 400 ps at one atmosphere gas pressure [4] and 150 ps at ten atmospheres [3].…”