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@ARTICLE{Demirbas:606464,
      author       = {Demirbas, Uemit and Rentschler, Christian and Zhang, Zhelin
                      and Pergament, Mikhail and Matlis, Nicholas and Kärtner,
                      Franz},
      title        = {{T}emperature dependence of {TH}z generation efficiency,
                      {TH}z refractive index, and {TH}z absorption in
                      lithium-niobate around 275 {GH}z},
      journal      = {Optical materials express},
      volume       = {14},
      number       = {7},
      issn         = {2159-3930},
      address      = {Washington, DC},
      publisher    = {Optica},
      reportid     = {PUBDB-2024-01599},
      pages        = {1886},
      year         = {2024},
      abstract     = {We used pulse trains with 800-fs long pulses and adjustable
                      time delay to investigate the temperature dependence of THz
                      generation in a periodically pooled lithium niobate (PPLN)
                      crystal with a poling period of 400 µm. By adjusting the
                      PPLN temperature (78-350 K), multicycle, narrowband (sub-10
                      GHz) THz pulses with tunable central frequency in the
                      253-287 GHz range were obtained. Internal conversion
                      efficiency values up to $0.45\%$ were demonstrated at a peak
                      fluence value of 150 mJ/cm2 at 78 K. Via scanning the
                      incident pulse-train frequency, we measured the frequency
                      response of the crystal at different temperatures, which
                      enabled us to determine the temperature dependence of the
                      refractive index and thermo-optic coefficient of the PPLN
                      crystal around 275 GHz with very high precision. We further
                      studied the variation of THz generation efficiency with
                      temperature in detail to understand the temperature
                      dependence of THz absorption in PPLN material. Here, we
                      observed that it is difficult to isolate the temperature
                      dependence of absorption with high accuracy from the THz
                      efficiency data, as the efficiency depends on many other
                      factors that could also be temperature-dependent. Overall,
                      the results presented in this manuscript demonstrate the
                      capability of the tunable-frequency pulse-train excitation
                      approach in mapping fundamental properties of nonlinear
                      crystals at relatively low THz frequencies, where other
                      characterization methods, such as THz time-domain
                      spectroscopy, have difficulties.},
      cin          = {FS-CFEL-2},
      ddc          = {620},
      cid          = {I:(DE-H253)FS-CFEL-2-20120731},
      pnm          = {631 - Matter – Dynamics, Mechanisms and Control
                      (POF4-631) / AXSIS - Frontiers in Attosecond X-ray Science:
                      Imaging and Spectroscopy (609920)},
      pid          = {G:(DE-HGF)POF4-631 / G:(EU-Grant)609920},
      experiment   = {EXP:(DE-H253)AXSIS-20200101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001266706400005},
      doi          = {10.1364/OME.528491},
      url          = {https://bib-pubdb1.desy.de/record/606464},
}