Abstract

High resolution shaping of femtosecond pulses can be achieved by spatial masking of optical frequency components which are spatially dispersed within a special grating and lens apparatus.^1,2 Previously masking was performed with patterned amplitude and phase masks fabricated by microlithography, and this approach allowed generation of shaped ultrashort pulses ranging from square pulses to coded pseudonoise bursts. In this paper we extend the scope of our pulse shaping technique by using a programmable liquid crystal multielement modulator as a replacement for the prefabricated masks. In particular, we demonstrated pulse shaping with a nematic liquid crystal phase modulator controlled by a linear array of thirty-two individual electrodes spaced on 100-μm centers. We tested the multielement modulator by using 80-fs, 0.62-μm pulses from a CPM ring dye laser and verified that we could generate various shaped pulses, such as odd pulses² and terahertz rate pulse trains, by adjusting the individual electrode voltages. The modulator could be reprogrammed and a new pulse shape selected with a response time of the order of 100 ms. Futhermore, we have demonstrated gray level (continuous) control of the individual phases, a degree of control not available from prefabricated phase masks.

© 1989 Optical Society of America