TY  - JOUR
AU  - Schoenberg, Arthur
AU  - Salman, Haydar Sarper
AU  - Tajalli Seifi, Ayhan
AU  - Kumar, Sonu
AU  - Hartl, Ingmar
AU  - Heyl, Christoph
TI  - Below-threshold harmonic generation in gasjets for Th-229 nuclear spectroscopy
JO  - Optics express
VL  - 31
IS  - 8
SN  - 1094-4087
CY  - Washington, DC
PB  - Optica
M1  - PUBDB-2023-00396
SP  - 12880 - 12893
PY  - 2023
AB  - The generation of below-threshold harmonics in gas-jets constitutes a promising path towards optical frequency combs in the vacuum ultra-violet (VUV) spectral range. Of particular interest is the 150 nm range, which can be exploited to probe the nuclear isomeric transition of the Thorium-229 isotope. Using widely available high-power, high-repetition-rate Ytterbium-based laser sources, VUV frequency combs can be generated through the process of below-threshold harmonic generation, in particular 7th harmonic generation of 1030 nm. Knowledge about the achievable efficiencies of the harmonic generation process is crucial for the development of suitable VUV sources. In this work, we measure the total output pulse energies and conversion efficiencies of below-threshold harmonics in gas-jets in a phase-mismatched generation scheme using Argon and Krypton as nonlinear media. Using a 220 fs, 1030 nm source, we reach a maximum conversion efficiency of 1.1 × 10−5 for the 7th harmonic (147 nm) and 0.78 × 10−4 for the 5th harmonic (206 nm). In addition, we characterize the 3rd harmonic of a 178 fs, 515 nm source with a maximum efficiency of 0.3
LB  - PUB:(DE-HGF)16
C6  - 37157438
UR  - <Go to ISI:>//WOS:000975304700003
DO  - DOI:10.1364/OE.486338
UR  - https://bib-pubdb1.desy.de/record/517343
ER  -