Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

Abstract

EuTe possesses the centrosymmetric crystal structure m3m of rocksalt type in which the second-harmonic generation is forbidden in electric dipole approximation but the third-harmonic generation ͑THG͒ is allowed. We studied the THG spectra of this material and observed several resonances in the vicinity of the band gap at 2.2-2.5 eV and at higher energies up to 4 eV, which are related to four-photon THG processes. The observed resonances are assigned to specific combinations of electronic transitions between the ground 4f 7 state at the top of the valence band and excited 4f 6 5d 1 states of Eu 2+ ions, which form the lowest energy conduction band. Temperature, magnetic field, and rotational anisotropy studies allowed us to distinguish crystallographic and magnetic-field-induced contributions to the THG. A strong modification of THG intensity for the 2.4 eV band and suppression of the THG for the 3.15 eV band was observed in applied magnetic field. Two main features of the THG spectra were assigned to 5d͑t 2g ͒ and 5d͑e g ͒ subbands at 2.4 eV and 3.15 eV, respectively. A microscopic quantum-mechanical model of the THG response was developed and its conclusions are in qualitative agreement with the experimental results.

Tunable and switchable polarization rotation with non-reciprocal plasmonic thin films at designated wavelengths

“…10 Applying a magnetic field to magneto-optical materials can also change the nonlinear optical effects of the material. [11][12][13][14][15] These physical effects provide us with versatile approaches to develop magnetically tunable devices. 16,17 In optical applications, the Faraday effect proves to be a versatile mechanism to manipulate light.…”

Optical third harmonic generation in the magnetic semiconductor EuSe

“…21 In materials without space-inversion symmetry the THG susceptibilities are smaller in magnitude than ED-SHG nonlinearities, and in this case THG serves rather as a complimentary tool. However, THG spectroscopy is really powerful for investigating materials where ED-SHG is forbidden.…”

“…22 When both SHG and third harmonic generation (THG) processes are allowed in the same medium they can provide complementary information on crystallographic, electronic, and magnetic structures. It should be noted that THG spectroscopic studies 21 have been performed much more seldom than SHG ones. 19,[24][25][26] In this paper we report on a spectroscopic study of crystallographic and magnetic-field-induced THG in the magnetic semiconductor EuSe.…”

“…[19][20][21][22][23] Using second harmonic generation (SHG) a novel type of nonlinear optical susceptibility was discovered in EuTe and EuSe. 19 Spatially resolved SHG in EuO films disclose a submicron size of ferromagnetic domains.…”

Giant third-order magneto-optical rotation in ferromagnetic EuO

“…18 Pronounced magnetization-induced SHG and THG contributions have been observed on the binary Eu compounds and the electronic origin of the SHG and THG spectra has been discussed. [21][22][23][24] Hence, because of outstanding magnetic and optical properties and their strong connection, EuO is an ideal compound for exploring the TFR. Yet, as we will see, the results gained on EuO are instructive for understanding TFR in general.…”