Abstract-Metrology of Complex Refractive Index for Solids in the Terahertz Regime Using Frequency Domain Spectroscopy

S. R. Chick, B. Murdin,  G. Matmon, M Naftaly,

https://arxiv.org/ftp/arxiv/papers/1805/1805.03590.pdf

Frequency domain spectroscopy allows an experimenter to establish optical properties of solids in a wide frequency band including the technically challenging 10 𝑇𝐻𝑧 region, and in other bands enables metrological comparison between competing techniques. We advance a method for extracting the optical properties of high-index solids using only transmission-mode frequency domain spectroscopy of plane-parallel Fabry-Perot optical flats. We show that different data processing techniques yield different kinds of systematic error, and that some commonly used techniques have inherent systematic errors which are underappreciated. We use model datasets to cross-compare algorithms in isolation from experimental errors, and propose a new algorithm which has qualitatively different systematic errors to its competitors. We show that our proposal is more robust to experimental non-idealities such as noise or apodization, and extract the complex refractive index spectrum of crystalline silicon as a practical example. Finally, we advance the idea that algorithms are complementary rather than competitive, and should be used together as part of a toolbox for better metrology

Abstract-Optical response from terahertz to visible light of electronuclear transitions in LiYF4:Ho3+

G. Matmon, S. A. Lynch, T. F. Rosenbaum, A. J. Fisher, and G. Aeppli

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.205132

Because of its role as a model system with tunable quantum fluctuations and quenched disorder, and the desire for optical control and readout of its states, we have used high-resolution optical absorption spectroscopy to measure the crystal-field excitations for Ho3+ ions in LiHoxY1−xF4 from the terahertz to visible regimes. We show that many of the excitations yield very narrow lines visibly split even by the nuclear hyperfine interaction, making Ho3+ in LiHoxY1−xF4 a candidate host for optically addressable electronuclear qubits with quality factors as high as Q=4.7×105, where the higher-lying levels are electronic singlets. Optical transitions in the easily accessible near- and mid-infrared are narrow enough to allow readout of the ground-state electronuclear qubits responsible for the interesting magnetism of LiHoxY1−xF4. While many of the higher-lying states have been observed previously, we also report here detailed spectra of terahertz excitations. The strengths of the electric and magnetic dipole crystal-field transition lines of five of the lowest excited spin-orbit manifolds of dilute LiYF4:Ho3+ were calculated and compared with measurement. The magnitude of the nuclear hyperfine coupling was used to assign the correct upper and lower states to transition lines.

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Abstract-Optical response from the terahertz domain to visible light of electronuclear transitions in LiYF4:Ho3+

G. Matmon, S. A. Lynch, T. F. Rosenbaum, A. J. Fisher, and G. Aeppli

https://journals.aps.org/prb/accepted/f707bK9eF5316d0a710c2a75f5c802098c53e8fb8

Because of its role as a model system with tunable quantum fluctuations and quenched disorder, and the desire for optical control and readout of its states, we have used high resolution optical absorption spectroscopy to measure the crystal field excitations for \mathrm{Ho}3+ ions in \mathrm{LiHo}_x\mathrm{Y}1-x\mathrm{F}_4 from the THz to visible regimes. We show that many of the excitations yield very narrow lines visibly split even by the nuclear hyperfine interaction, making \mathrm{Ho}3+ in \mathrm{LiHo}_x\mathrm{Y}1-x\mathrm{F}_4 a candidate host for optically addressable electro-nuclear qubits with quality factors as high as Q=4.7\times10^5, where the higher lying levels are electronic singlets. Optical transitions in the easily accessible near and mid-infrared are narrow enough to allow readout of the ground state electronuclear qubits responsible for the interesting magnetism of \mathrm{LiHo}_x\mathrm{Y}1-x\mathrm{F}_4. While many of the higher-lying states have been observed previously, we also report here detailed THz domain excitations. The strengths of the electric- and magnetic dipole crystal field transition lines of five of the lowest excited spin-orbit manifolds of dilute LiYF4:Ho3+ were calculated and compared with measurement. The magnitude of the nuclear hyperfine coupling was used to assign the correct upper and lower states to transition lines.