Parametrically polarization-shaped pulses via a hollow-core photonic crystal fiber

We present a procedure to generate parametrically shaped pulses after propagation through a microstructured hollow-core photonic crystal fiber. The properties of the fiber are characterized and employed to analytically design sequences of subpulses which are available after the fiber. In these sequences, each subpulse can be individually controlled in its physically intuitive parameters: position in time, energy, phase, and chirp as well as the polarization state with orientation, ellipticity, and helicity. Various endoscopic applications may arise from this approach.

Figure 1

(a) Experimental setup. The ultrashort laser pulses are shaped in phase, amplitude, and polarization by two double liquid crystal modulators situated in the Fourier plane of a 4$f$-line. The pulses are coupled into a photonic-crystal hollow-core fiber with the help of a telescope and a collimator. After propagation through the fiber, the pulses are characterized using autocorrelation and cross-correlation measurements. (b) A micrograph of the fiber (from [17]).

Figure 2

Pulses after transmission through the fiber. (a) A linearly polarized short pulse enters the fiber oriented at 45${}^{°}$ to the optical axis of the fiber. (b) A pair of compensated orthogonally polarized pulses with a difference phase of zero produces a single linearly polarized pulse oriented at $+$45${}^{°}$ respective to the axes of the fibers.

Figure 3

Complex amplified polarization-shaped pulse sequences after propagation through the hollow-core fiber. The time-dependent polarization and intensity are accompanied by a three-dimensional representation of the pulse.

Figure 4

Investigation of nonlinearities. The autocorrelation time is measured in dependence of the pulse energy for two linearly polarized pulses.