Reconstruction of polarization-shaped laser pulses after a hollow-core fiber using backreflection

We present a method to reconstruct the pulse shape of polarization-shaped femtosecond laser pulses after a hollow-core photonic crystal fiber by reflecting the pulses back through the fiber. First, a procedure is introduced to receive the optical fiber properties and generate parametrically shaped pulses after propagation through the fiber. Changes of the fiber's birefringence by mechanical stress are examined to investigate the correlation between the pulse shapes after one and two passes through the fiber. Finally, we demonstrate the characterization of the pulse after one pass through the fiber by calculating the pulse shape from the measured pulse after two passes.