Third-harmonic generation in a plasma formed by optical breakdown of air in the field of femtosecond laser pulses with high repetition rate

A study was made of third-harmonic generation in a field of 200-fs pulses representing amplified radiation of a titanium-doped sapphire laser in an optical break-down plasma formed in air at atmospheric pressure. It was shown that a low-temperature laser plasma can be used for harmonic generation at a repetition rate up to 1 kHz and with a power conversion efficiency of 7 × 10^–4.