Temporal pulse division in hollow fiber compressors

We propose a detailed analysis of a temporal multiplexing technique suited to the post-compression of energetic femtosecond laser pulses in gas-filled hollow-core fibers down to the few-cycle regime. Twofold temporal division and combination are achieved using two birefringent plates with specific crystallographic orientation. We demonstrate a simple interferometric method for measuring the relative spectral phase between two replicas, which gives a measure of the phase mismatch in the combining plate, as well as that induced by eventual cross-phase modulation or ionization during propagation in the fiber. We present the experimental conditions required for producing few-cycle pulses with high fidelity. This passive combination technique will aid the energy scaling of hollow fiber compressors to the multi-millijoule level.