Crystals

Research

12 pages, 3200 KiB

Open AccessArticle

Growth, Structure, and Spectroscopic Properties of a Disordered Nd:SrLaGaO₄ Laser Crystal

by Shanshan Fang, Ling Liang, Wei Wang, Yiyang Lin, Yijian Sun, Guoliang Gong, Chaoyang Tu and Herui Wen

Crystals 2024, 14(2), 174; https://doi.org/10.3390/cryst14020174 - 09 Feb 2024

Viewed by 769

Abstract

A disordered Nd:SrLaGaO₄ (Nd:SLG) laser crystal was successfully grown via the Czochralski (CZ) technique. The crystal structure, refractive index, polarized absorption spectra, and stimulated emission spectra were measured. The spectroscopic properties were studied intensively with the Judd–Ofelt (J-O) theory. The maximum absorption [...] Read more.

A disordered Nd:SrLaGaO₄ (Nd:SLG) laser crystal was successfully grown via the Czochralski (CZ) technique. The crystal structure, refractive index, polarized absorption spectra, and stimulated emission spectra were measured. The spectroscopic properties were studied intensively with the Judd–Ofelt (J-O) theory. The maximum absorption cross sections of π- and σ-polarization at 806 nm were calculated to be 3.73 × 10⁻²⁰ and 4.05 × 10⁻²⁰ cm², corresponding to FWHMs of 6.00 and 6.10 nm, respectively. The maximum emission cross sections of π- and σ-polarization at 1076 nm were 3.97 × 10⁻²⁰ and 4.12 × 10⁻²⁰ cm², with FWHMs of 30.21 and 19.44 nm, respectively. The decay life of the Nd³⁺:⁴F_3/2 energy level was fitted to be 0.152 ms, and the fluorescence quantum efficiency was 72.72%. The inhomogeneous broadening in spectra benefiting from the disordered structure indicates the Nd:SLG crystal is a promising gain medium for ultrafast laser and tunable laser generations in the near infrared region. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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11 pages, 5768 KiB

Open AccessArticle

Optimal Doping Concentrations of Nd³⁺ Ions in CYGA Laser Crystals

by Siliang Lu, Juncheng Tan, Zhen Li, Peixiong Zhang and Zhenqiang Chen

Crystals 2024, 14(2), 168; https://doi.org/10.3390/cryst14020168 - 07 Feb 2024

Viewed by 641

Abstract

The kinetic process of the excited state population of Nd³⁺ ion in Nd: CaY_0.9Gd_0.1AlO₄ (Nd: CYGA) crystal were studied in detail to estimate the optimal doping concentration, which maximize ~1 μm fluorescence emission from the ⁴F [...] Read more.

The kinetic process of the excited state population of Nd³⁺ ion in Nd: CaY_0.9Gd_0.1AlO₄ (Nd: CYGA) crystal were studied in detail to estimate the optimal doping concentration, which maximize ~1 μm fluorescence emission from the ⁴F_3/2 state to the ⁴I_9/2 state of Nd³⁺. The analysis was accomplished by revealing the dependence of the excited state population on the doping concentration in a relatively convenient way in theory. After comparing the theoretical prediction results with the experimental findings and approximating the results obtained using the aforementioned method, the optimal relative doping concentration of Nd: CYGA was determined to be 2.1 at.%, which closely matched the 2.0 at.% obtained through experimental comparison. This verifies the effectiveness and accuracy of the proposed method. In particular, it is worth mentioning that in this method only one doping concentration of the crystal is required to obtain the optimal concentration, which may be used to guide the concentration optimization process for improving efficiency and saving resources. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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12 pages, 3559 KiB

Open AccessArticle

Growth and Characterization of Yb: CALYGLO Crystal for Ultrashort Pulse Laser Applications

by Zebin Wang, Jian Liu, Peng Chen, Peng Liu, Jie Ma, Xiaodong Xu, Yong Wei, Kheirreddine Lebbou and Jun Xu

Crystals 2024, 14(2), 120; https://doi.org/10.3390/cryst14020120 - 25 Jan 2024

Cited by 2 | Viewed by 768

Abstract

Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was [...] Read more.

Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10⁻²⁰ cm² for σ polarization and 5.32 × 10⁻²⁰ cm² for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10⁻²⁰ cm² at 980 nm for σ polarization and 2.28 × 10⁻²⁰ cm² at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at ²F_5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y³⁺ in the crystal is partially replaced by Lu³⁺ and Gd³⁺, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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12 pages, 2949 KiB

Open AccessArticle

Piezoelectric Elements with PVDF–TrFE/MWCNT-Aligned Composite Nanowires for Energy Harvesting Applications

by Mariya Aleksandrova, Tsvetozar Tsanev, Berek Kadikoff, Dimiter Alexandrov, Krasimir Nedelchev and Ivan Kralov

Crystals 2023, 13(12), 1626; https://doi.org/10.3390/cryst13121626 - 23 Nov 2023

Viewed by 960

Abstract

A self-sustainable power supply function with flexibility, mechanical stability, and lightweight quality is among the required properties for pressure sensors and other low-power-consuming electronics and wearable devices. In this work, a poly(vinylidene fluoride-trifluoroethylene)/multi-walled carbon nanotube (P(VDF–TrFE)/MWCNT) composite was prepared to increase the electrical [...] Read more.

A self-sustainable power supply function with flexibility, mechanical stability, and lightweight quality is among the required properties for pressure sensors and other low-power-consuming electronics and wearable devices. In this work, a poly(vinylidene fluoride-trifluoroethylene)/multi-walled carbon nanotube (P(VDF–TrFE)/MWCNT) composite was prepared to increase the electrical conductivity of the piezoelectric polymer and, thus, improve its electrical power generation capabilities. It was soaked by injection molding through an anodic aluminum oxide membrane to align vertically with the dipoles and exclude the possibility of dipole moment quenching. The composite membrane-type element exhibited an excellent piezoelectric coefficient d₃₃ of 42 pC/N at a frequency of 50 Hz and an applied force intensity of 10 N, while the sensitivity was ~375 µV/g, which is favorable for self-powered pressure sensor application. The resulting composite element was utilized to generate the piezoelectric signal and to investigate the dependence of the electromechanical behavior on the surface roughness, morphology, and contact interface resistance. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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10 pages, 3880 KiB

Open AccessArticle

An Axicon-Based Annular Pump Acousto-Optic Q-Switched Nd:GdVO₄ Self-Raman Vortex Laser

by Jie Liu, Yanmin Duan, Wenjie Mao, Xinxin Jin, Zhihong Li and Haiyong Zhu

Crystals 2023, 13(10), 1484; https://doi.org/10.3390/cryst13101484 - 12 Oct 2023

Cited by 2 | Viewed by 805

Abstract

We report, for the first time, the generation of a 1173 nm acousto-optic Q-switched self-Raman vortex laser with an axicon-based annular pump system. A 20 mm long Nd:GdVO₄ crystal was used as the self-Raman crystal. Both the fundamental field and the first-Stokes [...] Read more.

We report, for the first time, the generation of a 1173 nm acousto-optic Q-switched self-Raman vortex laser with an axicon-based annular pump system. A 20 mm long Nd:GdVO₄ crystal was used as the self-Raman crystal. Both the fundamental field and the first-Stokes field were investigated using the respective output couplers. In comparison with both vortex fields, a noticeable beam cleaning-up effect and pulse compression were observed from the 1063 nm fundamental field to the 1173 nm first-Stokes field. A Stokes field carrying a unitary topological charge was achieved. Finally, the average output power of the first-Stokes vortex emission reached 454 mW under an incident pump power of 19.5 W, corresponding to a pulse width of 45.7 ns. It was beneficial to apply a high peak power from the Q-switched laser and self-Raman conversion to expand the applications of the vortex laser beam. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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16 pages, 6310 KiB

Open AccessArticle

Design and Performance Enhancement of a Piezoelectric Micromachined Ultrasonic Transducer Based on NBBT Lead-Free Piezoelectric Single-Crystal Thin Film

by Yaqi Liu, Qiaozhen Zhang, Mingzhu Chen, Xiaonan Liu, Jiye Yang, Feifei Wang, Yanxue Tang, Bin Miao, Jiadong Li and Xiangyong Zhao

Crystals 2023, 13(9), 1394; https://doi.org/10.3390/cryst13091394 - 19 Sep 2023

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Abstract

Piezoelectric micromachined ultrasonic transducers (PMUTs) have attracted widespread attention due to their high performance, miniaturization, and easy integration with semiconductor processes. In this paper, a PMUT device based on high-performance and lead-free Na_0.5Bi_0.5TiO₃-BaTiO₃ (NBBT) piezoelectric single-crystal [...] Read more.

Piezoelectric micromachined ultrasonic transducers (PMUTs) have attracted widespread attention due to their high performance, miniaturization, and easy integration with semiconductor processes. In this paper, a PMUT device based on high-performance and lead-free Na_0.5Bi_0.5TiO₃-BaTiO₃ (NBBT) piezoelectric single-crystal thin films was designed for the application of medical high-frequency ultrasonics. Three-dimensional modeling and analysis of PMUT elements on the proposed structure were performed via the finite element method. The relationship between structure configuration in terms of the top electrode and the cavity shape of the bottom was studied. The PMUT properties and its device performance, including resonant frequency, effective electromechanical coupling factor (

k_{e f f}^{2}

), and the static sensitivity of different device structures, were analyzed. In addition, by rotating the Euler Angle

γ

of the NBBT piezoelectric single-crystal film, the static sensitivity and

k_{e f f}^{2}

of the model are improved to 1.34 when

γ

is rotated to 45 ± 5°. It was shown that the PMUT using rotated NBBT demonstrated an enhanced relative pulse-echo sensitivity of −46 dB and a bandwidth of 35% when the reflective surface was 200 μm. We conclude that the PMUT in accordance with an NBBT piezoelectric single-crystal film designed by simulation offers a high frequency, larger

k_{e f f}^{2}

, and high sensitivity, which provides application prospects in high-resolution and high-frequency medical ultrasonic imaging. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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13 pages, 8055 KiB

Open AccessArticle

Bulk Polystyrene-BaF₂ Composite Scintillators for Highly Efficient Radiation Detection

by Xiang Li, Mingxue Deng, Yun Shi, Xuejun Qi, Shaohan Wang, Yugui Lu, Yong Du and Junfeng Chen

Crystals 2023, 13(9), 1334; https://doi.org/10.3390/cryst13091334 - 31 Aug 2023

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Abstract

Organic–inorganic composite scintillators, demonstrating advantages of easy large-area preparation and a high detection efficiency, have shown enormous potential application prospects in radiation detection and imaging. In this study, bulk polystyrene (PS) composite scintillators were successfully prepared by embedding inorganic BaF₂ particles with [...] Read more.

Organic–inorganic composite scintillators, demonstrating advantages of easy large-area preparation and a high detection efficiency, have shown enormous potential application prospects in radiation detection and imaging. In this study, bulk polystyrene (PS) composite scintillators were successfully prepared by embedding inorganic BaF₂ particles with a loading amount of up to 80 wt% during the polymerization process of the plastic scintillator. The inorganic BaF₂ particles were uniformly dispersed in the organic matrix. With the increase of the loading amounts of BaF₂ particles, the X-ray-excited luminescence intensity of the PS-BaF₂ composite scintillators was about eight times higher than that of the commercial pure plastic scintillator. The scintillation counts under the gamma ray (59.5 KeV) irradiation also showed that the detection efficiency was obviously enhanced by BaF₂ particle loading. More importantly, their scintillation pulse retains the decay kinetics of the organic matrix without loading the slow-decay component of BaF₂. This work provides a promising solution for the application of the PS-BaF₂ composite scintillator in high-efficiency radiation detection and large-area imaging. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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11 pages, 9081 KiB

Open AccessArticle

Growth and Scintillation Properties of Na⁺-Doped CsCu₂I₃ Single Crystals

by Chang Shu, Qinhua Wei, Dongdong Liu, Wen Li, Hang Yin, Huanying Li, Gao Tang and Laishun Qin

Crystals 2023, 13(8), 1157; https://doi.org/10.3390/cryst13081157 - 26 Jul 2023

Cited by 2 | Viewed by 986

Abstract

CsCu₂I₃ crystal is a promising Cu-based halide material for scintillation detection. In this paper, Na⁺ ion-doped CsCu₂I₃ crystals with a size of ϕ12 mm × 50 mm were grown successfully using the vertical Bridgman method, and [...] Read more.

CsCu₂I₃ crystal is a promising Cu-based halide material for scintillation detection. In this paper, Na⁺ ion-doped CsCu₂I₃ crystals with a size of ϕ12 mm × 50 mm were grown successfully using the vertical Bridgman method, and the properties were systematically investigated. CsCu₂I₃:Na crystals exhibit yellow light emission peaking at 575 nm and a large Stokes shift of 1.55 eV. Based on the results of the XRD and XPS, the Na⁺ was introduced successfully. The optical absorption spectra show that the band gap of CsCu₂I₃ crystals was narrowed when the Na⁺ was doped. The photoluminescence quantum efficiency (PLQY) is improved from 16.4% to 19.6%. Finally, the X-ray-induced afterglow, and scintillation (energy resolution, light yield and decay time) under a ¹³⁷Cs source were measured and discussed. These results illustrate that CsCu₂I₃:Na crystals have potential applications in the radiation detection field. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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11 pages, 4115 KiB

Open AccessArticle

Growth and Characterization of All-Inorganic Halide Perovskite CsPbF₃ Single Crystals

by Xinlong Yan, Kan Zhang, Chan Guo, Yi Lu, Kuiyao Du, Chen Peng, Xiaodie Hu, Yuzhen Jia, Bai Xu, Ruichen Wang, Weiheng Duan, Hetong Han, Zhaohui Song, Shiguo Liu and Fan Yang

Crystals 2023, 13(5), 765; https://doi.org/10.3390/cryst13050765 - 04 May 2023

Cited by 2 | Viewed by 1921

Abstract

Lead-based halide perovskite semiconductors have demonstrated considerable potential in optoelectronic applications. However, the lack of high-quality crystals suitable for research has led to rare reports on CsPbF₃ single crystals. Good quality CsPbF₃ single crystals were successfully grown using the Bridgman method. [...] Read more.

Lead-based halide perovskite semiconductors have demonstrated considerable potential in optoelectronic applications. However, the lack of high-quality crystals suitable for research has led to rare reports on CsPbF₃ single crystals. Good quality CsPbF₃ single crystals were successfully grown using the Bridgman method. The structure, luminescence, and electrical properties of crystals were investigated. At room temperature, the crystal structure was determined to be cubic perovskite, with a calculated bandgap of 3.68 eV. The measured emission spectrum showed one broad emission peak at approximately 400 nm. Three decay time constants were obtained from a sum of exponential functions fit to the fluorescence decay curve: 0.4 ns, 2.4 ns, and 15.0 ns for fast, middle, and slow decay times, respectively. The decay times excited by pulsed X-ray were measured to be 2.2 ns and 10.2 ns, indicating that CsPbF₃ is an ultrafast scintillator. Furthermore, the electrical properties demonstrated that CsPbF₃ exhibits high ion mobility, which is approximately 20 times that of electron mobility. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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13 pages, 2191 KiB

Open AccessArticle

Effects of Preparation Atmosphere and Doping Concentration on Scintillation and Photoluminescence Properties of Lu₂O₃:Eu Scintillation Single Crystals

by Wenbin Du, Baoqi Lu, Qianli Li, Zhan Xu, Haihang Yu and He Feng

Crystals 2023, 13(4), 680; https://doi.org/10.3390/cryst13040680 - 14 Apr 2023

Cited by 1 | Viewed by 977

Abstract

Lu₂O₃:1%Eu and Lu₂O₃:8%Eu series single crystals were grown by optical floating zone method under air, N₂, and H₂-Ar mixed atmosphere (5 vol%H₂ and 95 vol%Ar). The effects of preparation atmosphere [...] Read more.

Lu₂O₃:1%Eu and Lu₂O₃:8%Eu series single crystals were grown by optical floating zone method under air, N₂, and H₂-Ar mixed atmosphere (5 vol%H₂ and 95 vol%Ar). The effects of preparation atmosphere and doping concentration on the scintillation and photoluminescence properties have been investigated and discussed. Correlated measurements of afterglow curves, X-ray excited luminescence spectra, photoluminescence excitation and photoluminescence, photoluminescence decay, and thermal stimulated luminescence curves were performed. Although Eu(S₆) luminescence can be significantly depressed under oxidizing atmosphere, Lu₂O₃:8%Eu grown under weak reducing atmosphere presents the lowest afterglow intensity. This phenomenon was explained by different interstitial oxygen atom concentrations in the samples. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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