Temperature-dependent terahertz dielectric modulation of a high-performance magneto-optic CeF3 crystal
Introduction
Single crystals of Rare-earth garnets (Tb3Ga5O12 and Tb3Sc2Al3O12) as superior magneto-optical materials have attracted attention due to their large Faraday rotation angles [[1], [2], [3]]. As compared to the conventionally used terbium-gallium garnet (TGG), CeF3 has a much wider transparent region in visible and near-infrared wavelengths (300–2500 nm) [4]. Both CeF3 and TGG crystals are paramagnetic. However, the magneto-optical properties of CeF3 are better than TGG in visible-near infrared waveband [5,6]. In numerous previous works, crystal growth and scintillation characteristics of CeF3 in visible and infrared regions have been studied in detail. However, the optical properties of CeF3 in THz range still remain to be shown.
Terahertz (THz) [7] research has gained a new momentum and benefits from recent breakthroughs in the areas of quantum electrodynamics [8,9], ultrafast magnetic phenomena [10], imaging [11], spectroscopy [12], telecommunication network [13] etc. THz time-domain spectroscopy (THz-TDS) has proven to be an effective tool in condensed matter physics [14], which is used for the noninvasive and contactless electrical and optical characterizations of various materials.
Mikhaylovskiy et al. reported the inverse Faraday effect (IFE) in TGG [15]. Based on the IFE, Gorelov et al. reported THz Cherenkov radiation in TGG [16]. In addition, high frequency magnetic excitations are operated for TGG crystal by a magnetic field of a THz broadband pulse, which is in agreement with the theory of paramagnetic resonance in the multi-sublattice system [17]. Recently, Li et al. reported dielectric characterization at THz frequency in terbium scandium aluminum garnet (TSAG) [18]. CeF3 has lower optical loss and better magnetic-optical performance compared with TGG and TSAG. In this Letter, we focus our studies on dielectric response of CeF3 crystals in THz range. According to the data, the amplitude of Fourier transform amplitude spectra curves increases with lowering temperature. The weak loss indicates that CeF3 crystals are good candidates for high-permittivity insulation materials in optoelectronic devices in THz frequency ranges.
Section snippets
Experimental procedure
The CeF3 crystal (35 mm by 95 mm long) was successfully grown by the Bridgman-Stockbarger (BS) method using a resistance heating system [19]. Obtained crystal was cut to slices, that were polished down to 1.8 mm thickness. The both-side polished sample has crystal orientation <001> with c-axis perpendicular to the surface.
A schematic view of the experimental setup and its operation principle is given in Fig. 1. A Ti: sapphire-based (MaiTai HP, Spectra-Physics) mode-locked laser system (800 nm
Results and discussion
In order to investigate the optical properties of CeF3 single crystal, the time-domain THz waveform transmitted thought the sample with the thickness of 1.8 mm was measured at different temperatures, as shown in Fig. 2(a). In the figure, the green line is a reference signal Eref(t), which is a representative THz time-domain pulse waveform recorded under a dry N2 environment at room temperature. The rest lines represent the transmitted THz waveforms of the CeF3 crystal in the time domain were
Conclusion
In conclusion, complex refractive index and loss tangent of CeF3 single crystal have been determined in different temperatures. To the best of our knowledge, this is the first time when optical performance and dielectric response of CeF3 single crystal to THz pulse were characterized using THz-TDS technique. Refractive index values of CeF3 between 0.4 and 1.4 THz shows a monotonous rise, which is similar to the observation in TSAG crystal. The change in the value of the complex refractive index
Credit author contribution statement
Huifang Li: Investigation, Formal analysis, Writing original draft, Writing review & editing. Wuxin Ge: Investigation, Formal analysis. Jugeng Li: Investigation, Formal analysis. Yun Dai: Investigation. Junfeng Chen: Resources. Liangbi Su: Validation. Zuanming Jin: Investigation, Writing original draft, Formal analysis. Guohong Ma: Validation. Xiang Li: Supervision, Validation. Anhua Wu: Supervision, Methodology, Validation.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (NSFC) (51872309, 61975110, 11674213, 61735010, U1832106), NSFC- BRFFR joint project (52011530018), Science and Technology Commission of Shanghai Municipality (19520710900, 18511109700), the International Partnership Project of Chinese Academy of Sciences (121631KYSB20180045).
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