Abstract

We previously reported the synthesis of arbitrarily shaped picosecond pulses by spatial filtering in a fiber and grating pulse compressor.¹ Here we describe high-resolution shaping and encoding of femotsecond pulses using a modified nondispersive grating apparatus. Elementary examples include the femtosecond odd pulse (a pulse doublet abruptly phase shifted by π at t = 0)¹ and high-frequency femtosecond tone bursts with beat frequencies as high as 2.6 THz. To illustrate further the high degree of complexity which may be incorporated into the shaped waveforms, we discuss frequency domain phase coding of femtosecond pulses. Pseudorandom binary phase masks, fabricated according to the optimal m-sequence codes,² are utilized to scramble the phases of the various optical frequency components; In this way, intense femtosecond pulses are encoded into picosecond duration pseudonoise bursts. Subsequent unscrambling of the spectral phases (decoding) allows the original femtosecond pulse to be restored without broadening. We anticipate that high-resolution pulse shaping will have important applications in coherent time domain spectroscopy and optical communications; as one example we discuss a proposed optical spread spectrum communications switch based on encryption and decoding of ultrashort pulses.

© 1987 Optical Society of America