Pulse shaping with a phase-shifted fiber Bragg grating for antisymmetric pulse generation

Pulses of arbitrary temporal shape can be generated by spectrally filtering a short pulse. Frequency selective reflectors, such as fiber Bragg gratings, can be designed to obtain the desired pulse shape. The required distribution of the refractive index modulation, amplitude and phase, can be calculated using inverse scattering techniques. For weak gratings, under the Born approximation, the impulse response of the grating is directly related to the refractive index distribution. The specified refractive index can be photo-written in an optical fiber using standard phase-mask scanning techniques. Two Bragg gratings were specially designed to shape a train of gaussian pulses into antisymmetric Hermite-Gauss pulses. The first grating had a length of 40 mm producing a spectral response over 0.05 nm (peak-to-peak). This grating was interrogated by 100 ps pulses produced by a CW tunable laser with an external modulator. The second grating (L = 10 mm and Delta lambda = 0.18 nm) was interrogated with a mode-locked fiber laser (7 ps). The pulses were characterized in the frequency and time domain. The antisymmetric pulses were propagated in standard fiber to verify the presence of the phase shift between the two lobes. These Hermite-Gauss pulses could be used to study antisymmetric dispersion-managed soliton pulses.