Ultra-short optical pulse measurement using a thick nonlinear crystal

摘要

The invention provides a pulse measurement apparatus and corresponding method. The apparatus comprises: a splitter for splitting a pulse to be measured into two sub-pulses propagating along different beam paths; a non-linear medium, capable of up-conversion of radiation propagating therethrough, arranged in said beam paths; at least one element for interfering the up-converted pulses resulting from propagation of the two sub-pulses in the non-linear medium; and detection apparatus for detecting the result of the interference to obtain at least one of spectral and temporal characteristics of the pulse to be measured. In the non-linear medium, each sub-pulse can be resolved into an o-wave component and an e-wave component propagating through the medium at a predetermined angle, and the phase-matching function for up-conversion by interaction of the o-wave component with the e-wave component in the non-linear medium is selected such that up-conversion is substantially independent of frequency for one of the o-wave or e-wave over a predetermined frequency range, and is frequency selective for the other of the o-wave and e-wave. This phase-matching function produces spectrally-sheared up-converted replicas of the pulse to be measured.