High peak-power stretcher-free femtosecond fiber amplifier using passive spatio-temporal coherent combining

L Daniault,D N Papadopoulos,P Georges,Y Zaouter,M Hanna,E Mottay,F Druon

doi:10.1364/oe.20.021627

Abstract

We report on the passive coherent combining of up to 8 temporally and spatially separated ultrashort pulses amplified in a stretcher-free ytterbium-doped fiber system. An initial femtosecond pulse is split into 4 temporal replicas using divided-pulse amplification, and subsequently divided in two counter-propagating beams in a Sagnac interferometer containing a fiber amplifier. The spatio-temporal distribution of the peak-power inside the amplifier allows the generation of record 3.1 µJ and 50 fs pulses at 1 MHz of repetition rate with 52 MW of peak-power from a stretcher-free fiber amplifier and without additional nonlinear post-compression stages.

Highlights

During the last decade, ytterbium-doped fiber amplifiers have been established as efficient femtosecond laser sources
We report on the passive coherent combining of up to 8 temporally and spatially separated ultrashort pulses amplified in a stretcherfree ytterbium-doped fiber system
An initial femtosecond pulse is split into 4 temporal replicas using divided-pulse amplification, and subsequently divided in two counter-propagating beams in a Sagnac interferometer containing a fiber amplifier

Summary

Introduction

Ytterbium-doped fiber amplifiers have been established as efficient femtosecond laser sources. Passive CBC experiments in the femtosecond regime have been recently demonstrated, exhibiting high robustness to environmental perturbations, no control electronics, and the ability to reach the multi-GW level [7, 8] This has been achieved using a Sagnac interferometer (SI) that allows two counter-propagating beams to share the exact same optical path and be self-phase-matched. We demonstrate in this paper that passive coherent combining concepts, both in time (DPA) and space (SI), can be implemented together in a stretcher-free architecture in order to notably scale the energy and deliver 50 fs 3.1 μJ compressed pulses at 1 MHz repetition rate, exhibiting a peak power of 52 MW These performances correspond to unprecedented operation of a fiber amplifier in the stretcher-free amplification regime. They demonstrate that passive coherent combining both in the spatial and temporal domains is compatible with broadband spectra supporting sub-100 fs pulses, and B-integrals exceeding 20 rad

Efficient spatio-temporal splitting and combining

Stretcher-free amplification and experimental results

Conclusion