COMPARISON OF ULTRASHORT-PULSE FREQUENCY-RESOLVED-OPTICAL-GATING TRACES FOR 3 COMMON BEAM GEOMETRIES

We recently introduced frequency-resolved optical gating (FROG), a tec hnique for measuring the intensity and phase of an individual, arbitra ry, ultrashort laser pulse. FROG can use almost any instantaneous opti cal nonlinearity, with the most common geometries being polarization g ate, self-diffraction, and second-harmonic generation. The experimenta lly generated FROG trace is intuitive, visually appealing, and can yie ld quantitative information about the pulse parameters (such as tempor al and spectral width and chirp). However, the qualitative and the qua ntitative features of the FROG trace depend strongly on the geometry u sed. We compare the FROG traces for several common ultrashort pulses f or these three common geometries and, where possible, develop scaling rules that allow one to obtain quantitative information about the puls e directly from the experimental FROG trace. We illuminate the importa nt features of the various FROG traces for transform-limited, linearly chirped, self-phase modulated, and nonlinearly chirped pulses, pulses with simultaneous linear chirp and self-phase modulation, and pulses with simultaneous linear chirp and cubic phase distortion, as well as double pulses, pulses with phase jumps, and pulses with complex intens ity and phase substructure.