Full intensity profile analysis of ultrashort laser pulses using four-wave mixing or third harmonic generation

Abstract

New methods are proposed for the measurement of the full temporal intensity profile I( t) of ultrashort laser based on recording of a triple intensity-autocorrelation function. The possibilities offered by two third-order nonlinear processes, degenerate four-wave mixing (DFWM) and noncollinear third-harmonic generation (THG) are investigated from this aspect. In both cases double time-delay methods are considered first, where three replica pulses of profile I( t) with adjustable delays between them are used as input and the integral output intensity is monitored. The same information may be obtained in single-delay or single-shot schemes as well by using appropriate input beam expansions and a one- or two-dimensional detector array respectively, The methods considered have at least subpicosecond resolution. DFWM methods, in particular, are very convenient due to their wavelength-independence in a broad interval including UV.