Generation of adjustable femtosecond double pulses by diffraction of a chirped femtosecond pulse from volume Bragg gratings

Abstract

Based on Kogelnik’s coupled wave theory, femtosecond double pulses with adjustable pulse shape and interval are generated by diffraction of a chirped femtosecond pulse from transmitted volume Bragg gratings (VBGs). It is found that duration of the diffracted double pulses depends on the chirped parameter of the incident femtosecond pulse. When the chirp parameter is larger than zero, the double pulses are compressed. However, when it is less than zero, the double pulses are broadened. The degree of compression and broadening of the double pulses are different from each other. Moreover, the pulse interval between the double pulses is determined mainly by thickness and refractive index modulation of the VBG. This paper provides a theoretical foundation to design proper VBGs for generating femtosecond double pulses with different waveform.