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@ARTICLE{Wu:276321,
      author       = {Wu, Xiaojun and Zhou, Chun and Huang, Wenqian Ronny and
                      Ahr, Frederike and Kärtner, Franz X.},
      title        = {{T}emperature dependent refractive index and absorption
                      coefficient of congruent lithium niobate crystals in the
                      terahertz range},
      journal      = {Optics express},
      volume       = {23},
      number       = {23},
      issn         = {1094-4087},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PUBDB-2015-04552},
      pages        = {29729 - 29737},
      year         = {2015},
      abstract     = {Optical rectification with tilted pulse fronts in lithium
                      niobate crystals is one of the most promising methods to
                      generate terahertz (THz) radiation. In order to achieve
                      higher optical-to-THz energy efficiency, it is necessary to
                      cryogenically cool the crystal not only to decrease the
                      linear phonon absorption for the generated THz wave but also
                      to lengthen the effective interaction length between
                      infrared pump pulses and THz waves. However, the refractive
                      index of lithium niobate crystal at lower temperature is not
                      the same as that at room temperature, resulting in the
                      necessity to re-optimize or even re-build the tilted pulse
                      front setup. Here, we performed a temperature dependent
                      measurement of refractive index and absorption coefficient
                      on a 6.0 $mol\%$ MgO-doped congruent lithium niobate wafer
                      by using a THz time-domain spectrometer (THz-TDS). When the
                      crystal temperature was decreased from 300 K to 50 K, the
                      refractive index of the crystal in the extraordinary
                      polarization decreased from 5.05 to 4.88 at 0.4 THz,
                      resulting in ~1° change for the tilt angle inside the
                      lithium niobate crystal. The angle of incidence on the
                      grating for the tilted pulse front setup at 1030 nm with
                      demagnification factor of −0.5 needs to be changed by 3°.
                      The absorption coefficient decreased by $60\%$ at 0.4 THz.
                      These results are crucial for designing an optimum tilted
                      pulse front setup based on lithium niobate crystals.},
      cin          = {FS-CFEL-2},
      ddc          = {530},
      cid          = {I:(DE-H253)FS-CFEL-2-20120731},
      pnm          = {6211 - Extreme States of Matter: From Cold Ions to Hot
                      Plasmas (POF3-621) / AXSIS - Frontiers in Attosecond X-ray
                      Science: Imaging and Spectroscopy (609920) / CUI - Hamburger
                      Zentrum für ultraschnelle Beobachtung (194651731)},
      pid          = {G:(DE-HGF)POF3-6211 / G:(EU-Grant)609920 /
                      G:(GEPRIS)194651731},
      experiment   = {EXP:(DE-H253)CFEL-Exp-20150101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000366611500041},
      pubmed       = {pmid:26698455},
      doi          = {10.1364/OE.23.029729},
      url          = {https://bib-pubdb1.desy.de/record/276321},
}