Generation of backscattered 2?? and 3??/2 harmonics of femtosecond radiation from targets with different atomic numbers

Backscattered 2{/content/64W14FEHK3YHKQ9E/xxlarge8201.gif}{/content/64W14FEHK3YH K Q9E/xxlarge969.gif} and 3{/content/64W14FEHK3YHKQ9E/xxlarge8201.gif}{/content/64W14FEHK3YH K Q9E/xxlarge969.gif}/2 harmonics were investigated during the interaction of femtosecond radiation ({/content/64W14FEHK3YHKQ9E/xxlarge955.gif}=795 nm, t=150 fs, 10-Hz pulse repetition rate) with various targets. The harmonics were generated without changing the position of the targets from shot to shot. Various characteristics of the harmonics were analyzed and their dependences on pump radiation parameters are discussed. Efficient 2{/content/64W14FEHK3YHKQ9E/xxlarge8201.gif}{/content/64W14FEHK3YH K Q9E/xxlarge969.gif} and 3{/content/64W14FEHK3YHKQ9E/xxlarge8201.gif}{/content/64W14FEHK3YH K Q9E/xxlarge969.gif}/2 harmonics were achieved for low-Z targets, whereas only second-harmonic generation was observed for high-Z materials.