TY  - JOUR
AU  - Murari, Krishna
AU  - Cirmi, Giovanni
AU  - Cankaya, Huseyin
AU  - STEIN, GREGORY J.
AU  - DEBORD, BENOIT
AU  - GÉRÔME, FREDERIC
AU  - Ritzkowsky, Felix
AU  - BENABID, FETAH
AU  - Kärtner, Franz
TI  - Sub-50 fs pulses at 2050 nm from a picosecond Ho:YLF laser using a two-stage Kagome-fiber-based compressor 
JO  - Photonics research
VL  - 10
IS  - 3
SN  - 2327-9125
CY  - Washington, DC
PB  - OSA
M1  - PUBDB-2022-00117
SP  - 637 - 645
PY  - 2022
AB  - The high-energy few-cycle mid-infrared laser pulse beyond 2 μm is of immense importance for attosecond science and strong-field physics. However, the limited gain bandwidth of laser crystals such as Ho:YLF and Ho:YAG allows the generation of picosecond (ps) long pulses and, hence, makes it challenging to generate few-cycle pulse at 2 μm without utilizing an optical parametric chirped-pulse amplifier (OPCPA). Moreover, the exclusive use of the near-infrared wavelength has limited the generation of wavelengths beyond 4 μm (OPCPA). Furthermore, high harmonic generation (HHG) conversion efficiency reduces dramatically when driven by a long-wavelength laser. Novel schemes such as multi-color HHG have been proposed to enhance the harmonic flux. Therefore, it is highly desirable to generate few-cycle to femtosecond pulses from a 2 μm laser for driving these experiments. Here, we utilize two-stage nonlinear spectral broadening and pulse compression based on the Kagome-type hollow-core photonic crystal fiber (HC-PCF) to compress few-ps pulses to sub-50 fs from a Ho:YLF amplifier at 2 μm at 1 kHz repetition rate. We demonstrate both experimentally and numerically the compression of 3.3 ps at 140 μJ pulses to 48 fs at 11 μJ with focal intensity reaching 10<sup>13</sup> W/cm<sup>2</sup>. Thereby, this system can be used for driving HHG in solids at 2 μm. In the first stage, the pulses are spectrally broadened in Kagome fiber and compressed in a silicon-based prism compressor to 285 fs at a pulse energy of 90 μJ. In the second stage, the 285 fs pulse is self-compressed in air-filled HC-PCF. With fine-tuning of the group delay dispersion (GDD) externally in a 3 mm window, a compressed pulse of 48 fs is achieved. This leads to a 70-fold compression of the ps pulses at 2050 nm. We further used the sub-50 fs laser pulses to generate white light by focusing the pulse into a thin medium of YAG.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000762637400005
DO  - DOI:10.1364/PRJ.441674
UR  - https://bib-pubdb1.desy.de/record/473562
ER  -