Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 20: Optical Properties

HL 20.1: Talk

Tuesday, April 2, 2019, 14:00–14:15, H31

Second-Order Nonlinear Susceptibility of KNbO₃ — •Nils Mengel¹, Florian Dobener¹, Simone Sanna², and Sangam Chatterjee¹ — ¹Institute of Experimental Physics I and Center for Materials Research, Justus-Liebig-Universität Giessen, D-35392 Giessen — ²Institute of Theoretical Physics and Center for Materials Research, Justus-Liebig-Universität Giessen, D-35392 Giessen

Nonlinear effects offer numerous scientific and economic usability. From low-cost applications, e. g., laser pointers, to complex systems, such as optical parametric amplifiers, nonlinear materials play an important role in almost any spectroscopy related field. Some materials are able to convert the photon energies of available laser sources to photons of higher energy, thus making them key to extend laser excitation to the blue, UV and X-ray regions. The second-order (χ⁽²⁾) is the first and, generally, strongest nonlinear term emerging from the Taylor extension of the susceptibility, describing the doubling of the incident frequency. However, its wavelength dependency is somewhat unclear, since most of the materials are only characterized at standard wavelengths such as 532, 1064 or 808nm, as corresponding laser sources were early available.

Here, χ⁽²⁾ of potassium niobate (KNbO₃) is measured in a relative setup, corrected by the well-characterized nonlinear effects of alpha-quartz. KNbO₃ is an interesting material showing high second-order susceptibilities and resonances in the spectral excitation range of a Ti:sapphire laser. The measured spectra are in agreement with corresponding DFT calculations.