Optical heterodyne analysis of picosecond laser pulses

We present an optical heterodyne method to analyze laser pulses of picosecond duration using a frequency stabilized nanosecond laser. Optical heterodyning requires the linewidth of the nanosecond laser to be much smaller than the linewidth of the picosecond pulse being analyzed. This condition is easily achieved for seeded single-longitudinal-mode nanosecond lasers and seeded nanosecond OPOs. The timing of the two collinear lasers is adjusted such that the picosecond laser pulse arrives near the center of the nanosecond pulse, which fills the role normally performed by a CW laser. The beat pattern between the laser pulses is measured on a streak camera and analyzed through Fourier analysis.