Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2511.05370 · Physical Review Research

Spectroscopy and Coherence of an Excited-State Transition in $\text{Tm}^{3+}$:$\text{YAlO}_{3}$ at Telecommunication Wavelength

Luozhen Li, Akshay Babu Karyath, Mohsen Falamarzi Askarani, Maria Gieysztor, Hridya Meppully Sasidharan, Joshua A. Slater, Aaron D. Marsh, Philip J. T. Woodburn, Charles W. Thiel, Rufus L. Cone, Sara Marzban, Nir Alfasi, Patrick Remy, Wolfgang Tittel

quant-phSubmitted Nov 7, 2025• Announced Nov 10, 2025• 0 citations• Revised Nov 10, 2025 (v2)
v1 · Nov 7, 2025v2 · Nov 10, 2025v3 · May 12, 2026
arXivHTMLPDF

Abstract

We characterize the spectroscopic and coherence properties of the 1451.37 nm excited-state zero-phonon line (ZPL) between the $^{3}F_{4}$ and the $^{3}H_{4}$ manifolds of a thulium-doped yttrium aluminum perovskite ($\text{Tm}^{3+}$:$\text{YAlO}_{3}$) crystal at temperatures around 1.5 K. We measure the absorption spectrum between the $^{3}H_{6}$ - $^{3}F_{4}$ and $^{3}F_{4}$ - $^{3}H_{4}$ manifolds, the inhomogeneous broadening of the $^{3}F_{4}$ - $^{3}H_{4}$ (excited-state) ZPL, and the lifetimes of the higher-lying and lower-lying excited states. We also investigate spectral hole-burning spectra with varying magnetic fields, which provides insight into hyperfine and superhyperfine interactions. Using again spectral holes but also optical free induction decays (FIDs), we assess optical coherence times, finding a maximum of 1.1 $μs$ when a 2T magnetic field is applied. Our results -- the first to demonstrate coherence of an excited-state transition in a rare-earth crystal -- suggest the possibility of exploiting such transitions for quantum technology.

DOI
10.1103/73jf-lvyk
Comments
The main text contains 7 pages with 3 figures and 43 references. Supplemental material is attached after the main text

Related papers

Optical characterization of excited-state spin Hamiltonians and clock transitions at telecommunication wavelength in Tm3+:YAlO3

Akshay Babu Karyath, Luozhen Li, Julien Bertrand +6 more

The zero-phonon line (ZPL) between the two excited-state manifolds 3F4 and 3H4 of the trivalent thulium ion in yttrium aluminum perovskite (Tm3+:YAlO3) lies within the telecom E-band at around 1451 nm and exhibits an optical coherence time of a few μs at cryogenic temperatures. To improve this time in view of potential applications, e.g. single-photon sources and optical quantum memory, we characterized the magnetic properties of the lowest Stark levels of these two manifolds. Varying the external magnetic field amplitude and orientation, we measured the enhanced nuclear Zeeman splitting by probing the field-dependent frequency detuning of side holes created by means of spectral hole burning, and we characterized the inhomogeneous line shift caused by the quadratic Zeeman interaction. Together, this allowed us to establish the spin Hamiltonians for the lowest Stark level of the 3F4 and 3H4 manifolds, and to predict optical clock transitions for particular orientations and magnitudes of the magnetic field

quant-pharXiv:2609.31194•Sep 28, 2026•0 citations

Optical decoherence studies of Tm3+:Y3Ga5O12

Charles W. Thiel, Neil E. Sinclair, Wolfgang Tittel +1 more

Decoherence of the 795 nm $^{3}\mathrm{H}{}_{6}$ to $^{3}\mathrm{H}{}_{4}$ transition in $1%{\mathrm{Tm}}^{3+}:{\mathrm{Y}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ (Tm:YGG) is studied at temperatures as low as 1.2 K. The temperature, magnetic field, frequency, and time scale (spectral diffusion) dependence of the optical coherence lifetime is measured. Our results show that the coherence lifetime is impacted less by spectral diffusion than other known thulium-doped materials. Photon echo excitation and spectral hole burning methods reveal uniform decoherence properties and the possibility to produce full transparency for persistent spectral holes across the entire 56 GHz inhomogeneous bandwidth of the optical transition. Temperature-dependent decoherence is well described by elastic Raman scattering of phonons with an additional weaker component that may arise from a low density of glass-like dynamic disorder modes (two-level systems). Analysis of the observed behavior suggests that an optical coherence lifetime approaching 1 ms may be possible in this system at temperatures below 1 K for crystals grown with optimized properties. Overall, we find that Tm:YGG has superior decoherence properties compared to other Tm-doped crystals and is a promising candidate for applications that rely on long coherence lifetimes, such as optical quantum memories and photonic signal processing.

arXiv:1410.6096•Physical Review B•Dec 1, 2014•21 citations

Optical spectroscopy and decoherence studies of Yb3+ :YAG at 968 nm

Thomas Böttger, Charles W. Thiel, R. L. Cone +2 more

The $^{2}F_{7/2}\ensuremath{\leftrightarrow}^{2}F_{5/2}$ optical transitions of $\mathrm{Y}{\mathrm{b}}^{3+}$ doped into ${\mathrm{Y}}_{3}\mathrm{A}{\mathrm{l}}_{5}{\mathrm{O}}_{12}$ (YAG) were studied for potential quantum information and photonic signal processing applications. Absorption and fluorescence spectroscopy located the energy levels of the ground $^{2}F_{7/2}$ and excited $^{2}F_{5/2}$ manifolds, allowing inconsistencies between previous assignments of crystal field splittings in the literature to be resolved. These measurements reveal an unusually large splitting between the first and second levels in both the ground and excited multiplets, potentially providing for reduced sensitivity to thermally induced decoherence and spin-lattice relaxation. Spectral hole burning through two-level saturation was observed, determining the excited state lifetime to be 860 \ensuremath{\mu}s and resolving ambiguities in previous fluorescence measurements that were caused by the large radiation trapping effects in this material. Optical decoherence measurements using two-pulse photon echoes gave a homogeneous linewidth of 18 kHz for an applied magnetic field of 1 T, narrowing to 5 kHz at 2.5 T. The observed decoherence was described by spectral diffusion attributed to $\mathrm{Y}{\mathrm{b}}^{3+}\mathrm{\ensuremath{-}}\mathrm{Y}{\mathrm{b}}^{3+}$ magnetic dipole interactions. Laser absorption determined an inhomogeneous linewidth of 3.6 GHz for this transition in this 0.05%-doped crystal, which is narrower than for any other rare-earth-ion transition previously studied in the YAG host. The temperature dependence of the transition energy and linewidth of the lowest $^{2}F_{7/2}$ to lowest $^{2}F_{5/2}$ transition centered at 968.571 nm measured from 4 K to 300 K was well described by phonon scattering at higher temperatures, with an additional anomalous linear temperature-dependent broadening at temperatures below 80 K. Two magnetically inequivalent subgroups of $\mathrm{Y}{\mathrm{b}}^{3+}$ ions were identified when a magnetic field was applied along the $\ensuremath{\langle}111\ensuremath{\rangle}$ axis, as expected for the ${D}_{2}$ sites in the cubic symmetry crystal, with ground and excited state effective $g$-values of ${g}_{\mathrm{g}}=3.40$ (3.34) and ${g}_{\mathrm{e}}=1.04$ (2.01), respectively. Together with the convenient diode laser wavelength of this transition, our study suggests that $\mathrm{Y}{\mathrm{b}}^{3+}$:YAG is a promising material system for spectral hole burning and quantum information applications.

Physical review. B./Physical review. B•Jul 26, 2016•28 citations

Optical coherence and energy-level properties of a Tm3+ -doped LiNbO3 waveguide at subkelvin temperatures

Neil E. Sinclair, Daniel Oblak, Erhan Sağlamyürek +3 more

We characterize the optical coherence and energy-level properties of the 795-nm $^{3}\mathrm{H}_{6}$ to $^{3}\mathrm{H}_{4}$ transition of ${\mathrm{Tm}}^{3+}$ in a ${\mathrm{Ti}}^{4+}$:$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ waveguide at temperatures as low as 0.65 K. Coherence properties are measured with varied temperature, magnetic field, optical excitation power and wavelength, and measurement timescale. We also investigate nuclear spin-induced hyperfine structure and population dynamics with varying magnetic field and laser excitation power. Except for accountable differences due to different ${\mathrm{Ti}}^{4+}$- and ${\mathrm{Tm}}^{3+}$-doping concentrations, we find that the properties of ${\mathrm{Tm}}^{3+}$:${\mathrm{Ti}}^{4+}$:$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ produced by indiffusion doping are consistent with those of a bulk-doped ${\mathrm{Tm}}^{3+}$:$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ crystal measured under similar conditions. Our results, which complement previous work in a narrower parameter space, support using rare-earth ions for integrated optical and quantum signal processing.

arXiv:2101.08863•Physical review. B./Physical review. B•Apr 12, 2021•12 citations

Hyperfine structure, optical dephasing, and spectral-hole lifetime of single-crystalline Pr3+:La2(WO4)3

O. Guillot-Noël, Philippe Goldner, Y. Le Du +4 more

Most of the experiments related to quantum information applications, involving rare-earth doped inorganic crystals, are performed on yttrium orthosilicate single crystals. The work presented here is motivated by the search of new compounds which can be used in the field of quantum computing and/or quantum storage. Relaxation times and hyperfine structure of the $^{3}H_{4}(0)\ensuremath{\rightarrow}^{1}D_{2}(0)$ transition in 1.4% ${\mathrm{Pr}}^{3+}:{\mathrm{La}}_{2}{(\mathrm{W}{\mathrm{O}}_{4})}_{3}$ at $4\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ have been measured by photon-echo and spectral-hole-burning techniques. The hyperfine splittings of the ground $^{3}H_{4}(0)$ and the excited $^{1}D_{2}(0)$ states are $14.9\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$, $24.6\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$ and $5.0\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$, $7.3\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$, respectively. An inhomogeneous linewidth of $18.8\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ was measured. A homogeneous linewidth of $25.3\ifmmode\pm\else\textpm\fi{}2.0\phantom{\rule{0.3em}{0ex}}\mathrm{kHz}$ was obtained with or without an external magnetic field of about $14\phantom{\rule{0.3em}{0ex}}\mathrm{mT}$. The fluorescence dynamics of the $^{1}D_{2}$ level obtained by a direct excitation in the $^{3}H_{4}\ensuremath{\rightarrow}^{1}D_{2}$ transition gives a nonexponential decay which indicates energy-transfer processes. This decay can be accurately fitted by the Inokuti-Hirayama model [J. Chem. Phys. 43, 1978 (1965)] with a radiative lifetime of $61\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ giving a minimal homogeneous linewidth of $2.6\phantom{\rule{0.3em}{0ex}}\mathrm{kHz}$. The spectral-hole lifetime due to population redistribution within the ground hyperfine levels is $16\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.3em}{0ex}}\mathrm{s}$. The results obtained for the ${\mathrm{La}}_{2}{(\mathrm{W}{\mathrm{O}}_{4})}_{3}$ compound make this crystal an interesting host for quantum applications.

Physical Review B•May 15, 2007•19 citations

Optical characterizations of densely doped Tm3+:KYW crystals at low temperatures

Yisheng Lei, Trevor Kling, Mahdi Hosseini

Abstract We investigate the optical lifetime, decay characteristics, spectral linewidth and energy level properties of thulium ions doped in a KY(WO 4 ) 2 crystal at 4 K temperature. High doping concentration of thulium ions with inhomogeneous broadening allow us to study nonradiative behaviors, instantaneous spectral diffusion, and spectral power broadening in this solid-state material. The theoretical consideration of ion–ion interactions is shown to accurately characterize the absorption, decay and other spectral behaviors of Tm 3 + ions. We observe more than ten-fold reduction in the decay time of 3H4 state and about three-fold reduction in the spectral-hole lifetime as we approach the center of the inhomogeneous broadening, corresponding to higher optical densities.

Journal of Optics•Jul 8, 2024•0 citations
Spectroscopy and Coherence of an Excited-State Transition in Tm3+\text{Tm}^{3+}Tm3+:YAlO3\text{YAlO}_{3}YAlO3​ at Telecommunication Wavelength
We characterize the spectroscopic and coherence properties of the 1451.37 nm excited-state zero-phonon line (ZPL) between the 3F4^{3}F_{4}3F4​ and the 3H4^{3}H_{4}3H4​ manifolds of a thulium-doped yttrium aluminum perovskite (Tm3+\text{Tm}^{3+}Tm3+:YAlO3\text{YAlO}_{3}YAlO3​) crystal at temperatures around 1.5 K. We measure the absorption spectrum between the 3H6^{3}H_{6}3H6​ - 3F4^{3}F_{4}3F4​ and 3F4^{3}F_{4}3F4​ - 3H4^{3}H_{4}3H4​ manifolds, the inhomogeneous broadening of the 3F4^{3}F_{4}3F4​ - 3H4^{3}H_{4}3H4​ (excited-state) ZPL, and the lifetimes of the higher-lying and lower-lying excited states. We also investigate spectral hole-burning spectra with varying magnetic fields, which provides insight into hyperfine and superhyperfine interactions. Using again spectral holes but also optical free induction decays (FIDs), we assess optical coherence times, finding a maximum of 1.1 μsμsμs when a 2T magnetic field is applied. Our results -- the first to demonstrate coherence of an excited-state transition in a rare-earth crystal -- suggest the possibility of exploiting such transitions for quantum technology.
The zero-phonon line (ZPL) between the two excited-state manifolds 3F4 and 3H4 of the trivalent thulium ion in yttrium aluminum perovskite (Tm3+:YAlO3) lies within the telecom E-band at around 1451 nm and exhibits an optical coherence time of a few μs at cryogenic temperatures. To improve this time in view of potential applications, e.g. single-photon sources and optical quantum memory, we characterized the magnetic properties of the lowest Stark levels of these two manifolds. Varying the external magnetic field amplitude and orientation, we measured the enhanced nuclear Zeeman splitting by probing the field-dependent frequency detuning of side holes created by means of spectral hole burning, and we characterized the inhomogeneous line shift caused by the quadratic Zeeman interaction. Together, this allowed us to establish the spin Hamiltonians for the lowest Stark level of the 3F4 and 3H4 manifolds, and to predict optical clock transitions for particular orientations and magnitudes of the magnetic field
Decoherence of the 795 nm 3H6^{3}\mathrm{H}{}_{6}3H6​ to 3H4^{3}\mathrm{H}{}_{4}3H4​ transition in 11%{\mathrm{Tm}}^{3+}:{\mathrm{Y}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}1 (Tm:YGG) is studied at temperatures as low as 1.2 K. The temperature, magnetic field, frequency, and time scale (spectral diffusion) dependence of the optical coherence lifetime is measured. Our results show that the coherence lifetime is impacted less by spectral diffusion than other known thulium-doped materials. Photon echo excitation and spectral hole burning methods reveal uniform decoherence properties and the possibility to produce full transparency for persistent spectral holes across the entire 56 GHz inhomogeneous bandwidth of the optical transition. Temperature-dependent decoherence is well described by elastic Raman scattering of phonons with an additional weaker component that may arise from a low density of glass-like dynamic disorder modes (two-level systems). Analysis of the observed behavior suggests that an optical coherence lifetime approaching 1 ms may be possible in this system at temperatures below 1 K for crystals grown with optimized properties. Overall, we find that Tm:YGG has superior decoherence properties compared to other Tm-doped crystals and is a promising candidate for applications that rely on long coherence lifetimes, such as optical quantum memories and photonic signal processing.
The $^{2}F_{7/2}\ensuremath{\leftrightarrow}^{2}F_{5/2}$ optical transitions of Yb3+\mathrm{Y}{\mathrm{b}}^{3+}Yb3+ doped into Y3Al5O12{\mathrm{Y}}_{3}\mathrm{A}{\mathrm{l}}_{5}{\mathrm{O}}_{12}Y3​Al5​O12​ (YAG) were studied for potential quantum information and photonic signal processing applications. Absorption and fluorescence spectroscopy located the energy levels of the ground 2F7/2^{2}F_{7/2}2F7/2​ and excited 2F5/2^{2}F_{5/2}2F5/2​ manifolds, allowing inconsistencies between previous assignments of crystal field splittings in the literature to be resolved. These measurements reveal an unusually large splitting between the first and second levels in both the ground and excited multiplets, potentially providing for reduced sensitivity to thermally induced decoherence and spin-lattice relaxation. Spectral hole burning through two-level saturation was observed, determining the excited state lifetime to be 860 \ensuremath{\mu}s and resolving ambiguities in previous fluorescence measurements that were caused by the large radiation trapping effects in this material. Optical decoherence measurements using two-pulse photon echoes gave a homogeneous linewidth of 18 kHz for an applied magnetic field of 1 T, narrowing to 5 kHz at 2.5 T. The observed decoherence was described by spectral diffusion attributed to $\mathrm{Y}{\mathrm{b}}^{3+}\mathrm{\ensuremath{-}}\mathrm{Y}{\mathrm{b}}^{3+}$ magnetic dipole interactions. Laser absorption determined an inhomogeneous linewidth of 3.6 GHz for this transition in this 0.05%-doped crystal, which is narrower than for any other rare-earth-ion transition previously studied in the YAG host. The temperature dependence of the transition energy and linewidth of the lowest 2F7/2^{2}F_{7/2}2F7/2​ to lowest 2F5/2^{2}F_{5/2}2F5/2​ transition centered at 968.571 nm measured from 4 K to 300 K was well described by phonon scattering at higher temperatures, with an additional anomalous linear temperature-dependent broadening at temperatures below 80 K. Two magnetically inequivalent subgroups of Yb3+\mathrm{Y}{\mathrm{b}}^{3+}Yb3+ ions were identified when a magnetic field was applied along the $\ensuremath{\langle}111\ensuremath{\rangle}$ axis, as expected for the D2{D}_{2}D2​ sites in the cubic symmetry crystal, with ground and excited state effective ggg-values of gg=3.40{g}_{\mathrm{g}}=3.40gg​=3.40 (3.34) and ge=1.04{g}_{\mathrm{e}}=1.04ge​=1.04 (2.01), respectively. Together with the convenient diode laser wavelength of this transition, our study suggests that Yb3+\mathrm{Y}{\mathrm{b}}^{3+}Yb3+:YAG is a promising material system for spectral hole burning and quantum information applications.
We characterize the optical coherence and energy-level properties of the 795-nm 3H6^{3}\mathrm{H}_{6}3H6​ to 3H4^{3}\mathrm{H}_{4}3H4​ transition of Tm3+{\mathrm{Tm}}^{3+}Tm3+ in a Ti4+{\mathrm{Ti}}^{4+}Ti4+:LiNbO3\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}LiNbO3​ waveguide at temperatures as low as 0.65 K. Coherence properties are measured with varied temperature, magnetic field, optical excitation power and wavelength, and measurement timescale. We also investigate nuclear spin-induced hyperfine structure and population dynamics with varying magnetic field and laser excitation power. Except for accountable differences due to different Ti4+{\mathrm{Ti}}^{4+}Ti4+- and Tm3+{\mathrm{Tm}}^{3+}Tm3+-doping concentrations, we find that the properties of Tm3+{\mathrm{Tm}}^{3+}Tm3+:Ti4+{\mathrm{Ti}}^{4+}Ti4+:LiNbO3\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}LiNbO3​ produced by indiffusion doping are consistent with those of a bulk-doped Tm3+{\mathrm{Tm}}^{3+}Tm3+:LiNbO3\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}LiNbO3​ crystal measured under similar conditions. Our results, which complement previous work in a narrower parameter space, support using rare-earth ions for integrated optical and quantum signal processing.
Most of the experiments related to quantum information applications, involving rare-earth doped inorganic crystals, are performed on yttrium orthosilicate single crystals. The work presented here is motivated by the search of new compounds which can be used in the field of quantum computing and/or quantum storage. Relaxation times and hyperfine structure of the $^{3}H_{4}(0)\ensuremath{\rightarrow}^{1}D_{2}(0)$ transition in 1.4% Pr3+:La2(WO4)3{\mathrm{Pr}}^{3+}:{\mathrm{La}}_{2}{(\mathrm{W}{\mathrm{O}}_{4})}_{3}Pr3+:La2​(WO4​)3​ at 4K4\phantom{\rule{0.3em}{0ex}}\mathrm{K}4K have been measured by photon-echo and spectral-hole-burning techniques. The hyperfine splittings of the ground 3H4(0)^{3}H_{4}(0)3H4​(0) and the excited 1D2(0)^{1}D_{2}(0)1D2​(0) states are $14.9\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$, $24.6\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$ and $5.0\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$, $7.3\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$, respectively. An inhomogeneous linewidth of $18.8\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ was measured. A homogeneous linewidth of $25.3\ifmmode\pm\else\textpm\fi{}2.0\phantom{\rule{0.3em}{0ex}}\mathrm{kHz}$ was obtained with or without an external magnetic field of about 14mT14\phantom{\rule{0.3em}{0ex}}\mathrm{mT}14mT. The fluorescence dynamics of the 1D2^{1}D_{2}1D2​ level obtained by a direct excitation in the $^{3}H_{4}\ensuremath{\rightarrow}^{1}D_{2}$ transition gives a nonexponential decay which indicates energy-transfer processes. This decay can be accurately fitted by the Inokuti-Hirayama model [J. Chem. Phys. 43, 1978 (1965)] with a radiative lifetime of $61\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ giving a minimal homogeneous linewidth of 2.6kHz2.6\phantom{\rule{0.3em}{0ex}}\mathrm{kHz}2.6kHz. The spectral-hole lifetime due to population redistribution within the ground hyperfine levels is $16\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.3em}{0ex}}\mathrm{s}$. The results obtained for the La2(WO4)3{\mathrm{La}}_{2}{(\mathrm{W}{\mathrm{O}}_{4})}_{3}La2​(WO4​)3​ compound make this crystal an interesting host for quantum applications.
Abstract We investigate the optical lifetime, decay characteristics, spectral linewidth and energy level properties of thulium ions doped in a KY(WO 4 ) 2 crystal at 4 K temperature. High doping concentration of thulium ions with inhomogeneous broadening allow us to study nonradiative behaviors, instantaneous spectral diffusion, and spectral power broadening in this solid-state material. The theoretical consideration of ion–ion interactions is shown to accurately characterize the absorption, decay and other spectral behaviors of Tm 3 + ions. We observe more than ten-fold reduction in the decay time of 3H4 state and about three-fold reduction in the spectral-hole lifetime as we approach the center of the inhomogeneous broadening, corresponding to higher optical densities.