High-frequency temporal structure of laser and phase-conjugated signals at intracavity degenerate four-wave mixing of CO2 and CO laser radiation in their inverted medium

摘要

Abstract: The high frequency temporal structure of probe and phase conjugation (PC) signals under degenerate four-wave mixing (DFWM) of long pulse carbon-dioxide and carbon laser radiation in their inverted media has been studied experimentally with nanosecond resolution over the full pulse length. The multiline and single spectral line pulses of electron-beam controlled discharge (EBCD) carbon-dioxide and carbon lasers with pulse length of approximately 10 - 20 microseconds and approximately 200 - 300 microseconds, accordingly, are characterized by complicated temporal behavior with a periodic structure (approximately 100 ns) on account of mode beating with a depth of modulation up to 100%. On the round-trip period carbon-dioxide and carbon laser pulse consists of several spikes (for free-running mode) or a single spike in case of mode locking with pulse length of approximately 10 ns. A plasma mirror is used for carbon-dioxide laser to operate in the latter mode of operation. The time history of PC signal has a complicated behavior and structure differed from that of probe laser signal on large (greater than or equal to 100 ns) and small (approximately 10 - 100 ns) temporal scale. A relative influence of amplitude and phase mechanisms of creating diffraction gratings inside active medium, and also the influence of small scale and large scale gratings and spike synchronism conditions on the PC signal is discussed. !5