Abstract

Real-time pulse diagnostics for ultrafast oscillators have until recently been restricted to scanning spectrometers or autocorrelators which, although providing a convenient and intuitive monitor of the pulses, present only partial information about the temporal and spectral pulse characteristics. Users of amplified femtosecond lasers have been able to take advantage of the χ^(3)-based single-shot polarisation-gated frequency-resolved optical gating (FROG) method which provides a trace whose slope depends on the sign of the pulse chirp. Unfortunately, no equivalent intuitive and instantaneous pulse monitor has been available to users of lower power mode-locked oscillators, although recently O'Shea et al² recently reported a single-shot configuration for obtaining the second-harmonic-generation (SHG)-FROG trace. In this paper we present the first results from a new video-rate diagnostic instrument based on the sonogram (also known as the dynamic spectrogram) measurement³ which provides an intuitive display of the pulse chirp which can be used to track and manipulate the pulse characteristics in real-time.

© 2002 Optical Society of America