Abstract

Group delay dispersion (GDD) causes a variable delay vs. wavelength and is a ubiquitous, and often irritating, phenomenon in ultrafast laser labs. The pulse compressor, however, can introduce negative GDD [1] and compensate for it. Unfortunately, this device, even when it uses only two prisms, is as unwieldy as it is essential. To vary the GDD over a wide range of values, the separations between the two prisms must be varied, which involves several aligmnent parameters. Also, when not perfectly aligned, pulse compressors yield (very undesirable) angular dispersion, pulse-front tilt, spatial chirp, and one-dimensional beam magnification. Because pulse compressors must internally generate massive amounts of all of these distortions in order to operate, even residual amounts of them in the output pulse can be a serious problem. The device is also very inconvenient to tune in wavelength: both prisms must be carefully rotated by precisely the same amount, or else all of the above distortions occur. Finally, the device is quite bulky. To obtain the desired amount of negative GDD, the prism or grating separations can be quite large (> 1 m).

© 2007 IEEE