Generation of Pulses From Periodically Sawtooth Phase-Modulated CW Laser Field Using the Temporal Fractional Talbot Effect

Flat-top-pulse generation with a duty ratio close to 50% is considered for a periodical sawtooth phase-modulated CW laser field propagating through a group-delay-dispersion circuit. Pulses are formed at a quarter of the Talbot condition. The proposed method is compared with a binary phase-modulated field. It is shown that well-defined square-wave-type optical pulses are formed if a quarter of the Talbot condition is satisfied with the accuracy
$10^{-3}$
for both phase modulation patterns. Other fractional Talbot conditions, i.e.,
$1/3$
,
$1/6$
and
$1/8$
, are analyzed demonstrating multilevel temporal patterns similar to spatial patterns, which were observed in Fresnel diffraction of light from a phase grating. Technical advantages of the sawtooth phase modulation compared with the binary phase modulation are discussed.