High Harmonic Generation in Ar and N2 Gas Mixture Using Ultrashort High Power Laser System

Abstract

High harmonic generation (HHG) has been accepted as a tool for tabletop based generation of light source in the XUV and soft x ray region. HHG can produce coherent optical pulses having pulse duration in the femtosecond or even attosecond time region. In this paper, generation of high harmonics are produced by using high power laser system having optical pulses at 6mj pulse energy with pulse duration of 50fs at 10Hz repetition rate. High harmonics in pure Ar, N2 and mixture of the Ar-N2 are used as a generation medium to produce high harmonics. The harmonic signal is increased or decreased depending on the experimental condition. Harmonic yield produced in Ar is stronger than harmonic yield produced in N2 gas. Generation of high order harmonics are observed up to 35H (~54eV corresponding photon energy), and harmonic order from N2 gas is 33H. The mixture of two gas species cause to enhancement of 35H order, which is weakly observed in pure N2 gas. The mechanism of high harmonic generation is explained that strong harmonic signal generated in pure Ar gas helps increase the ionization rate of N2 gas. Thus, the harmonic signal in Ar-N2 is boosted compared the harmonic signal produced in pure N2. The enhancement factor of harmonic yield is from ~2 to 5 for per harmonic order.