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

Abstract

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-3}$</tex-math></inline-formula> for both phase modulation patterns. Other fractional Talbot conditions, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1/3$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1/6$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1/8$</tex-math></inline-formula> , 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.