Journal Article

PUBDB-2024-01599

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Temperature dependence of THz generation efficiency, THz refractive index, and THz absorption in lithium-niobate around 275 GHz

Demirbas, U.Extern*DESY* ; Rentschler, C.CFEL*DESY* ; Zhang, Z.Extern*DESY* ; Pergament, M.CFEL*DESY* ; Matlis, N.CFEL*DESY* ; Kärtner, F. (Corresponding author)CFEL*XFEL.EU*DESY*

2024
Optica Washington, DC

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Please use a persistent id in citations: doi:10.1364/OME.528491  doi:10.3204/PUBDB-2024-01599

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.

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Contributing Institute(s):

1. Ultrafast Lasers & X-rays Division (FS-CFEL-2)

Research Program(s):

1. 631 - Matter – Dynamics, Mechanisms and Control (POF4-631) (POF4-631)
2. AXSIS - Frontiers in Attosecond X-ray Science: Imaging and Spectroscopy (609920) (609920)

Experiment(s):

1. AXSIS: Frontiers in Attosecond X-ray Science, Imaging and Spectroscopy

Appears in the scientific report 2024

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