Mid-IR fluoride fibers: materials, fabrication, and fiber laser applications

Shunbin Wang; Shijie Jia; Yiguang Jiang; Long Zhang; Pengfei Wang; Yichun Liu

doi:10.3788/PI.2025.R07

Photonics Insights, Volume. 4, Issue 3, R07(2025)

Mid-IR fluoride fibers: materials, fabrication, and fiber laser applications

Shunbin Wang¹, Shijie Jia², Yiguang Jiang³, Long Zhang^3、*, Pengfei Wang^4,5、*, and Yichun Liu^4,5

Author Affiliations

¹Qingdao Innovation and Development Center, Harbin Engineering University, Qingdao, China

²College of Physics and Optoelectronic Engineering, Harbin Engineering University, Harbin, China

³Infrared Optical Materials Research Center, Advanced Laser and Optoelectronic Functional Materials Department, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, China

⁴School of Physics, Key Laboratory of UV-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, Changchun, China

⁵State Key Laboratory of Integrated Optoelectronics, Northeast Normal University, Changchun, China

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Figures & Tables(37)

Fig. 1. Overall characteristics and applications of fluoride fibers.

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Fig. 2. Glass-forming region in (a) ${ZrF}_{4} - {BaF}_{2} - NaF$ ternary systems, (b) ${ZrF}_{4} - {BaF}_{2} - {LaF}_{3}$ ternary systems stabilized by 4% ${AlF}_{3}$ , and (c) ${ZrF}_{4} - {BaF}_{2} - NaF$ ternary systems stabilized by 4% ${AlF}_{3}$ ^[42].

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Fig. 3. Glass-forming region in (a) ${AlF}_{3} - {SrF}_{2} - {MgF}_{2} - {YF}_{3}$ system^[66], (b) ${AlF}_{3} - {RF}_{2} - {YF}_{3}$ system^[67], and (c) ${AlF}_{3} - {YF}_{3} - {PbF}_{2}$ system^[78].

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Fig. 4. Transmission spectra of several fluoride glass.

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Fig. 5. Transmission spectra of (a) ZBLAN and (b) ZBYA glass before and after immersing in deionized water. (c) Spectral comparison of ZBLAN and ZBYA glass samples after 24 h immersion in deionized water. (d) Weightlessness comparison of ZBLAN and ZBYA glass samples after immersing in deionized water^[126] (Copyright © 2022 Optica Publishing Group).

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Fig. 6. Transmission spectra of the typical fluoroaluminate glass before immersion and after drying^[128].

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Fig. 7. Transmission spectra of core glass before and after immersing in water^[129].

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Fig. 8. Hot-jointing.

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Fig. 9. Built-in casting method: (a) traditional built-in casting, (b) rotational casting, (c) jacketing, (d) modified built-in casting, (e) lifting, and (f) suction casting.

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Fig. 10. (a) Rod-in-tube and (b) extrusion.

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Fig. 11. Structure of fiber drawing tower.

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Fig. 12. (a) Double crucible fiber drawing and (b) single crucible fiber drawing.

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Fig. 13. Schematic diagrams of resonators used for fiber lasers with (a) single-end co-propagating pump, (b) single-end counter-propagating pump, (c) dual end pumps, and (d) monolithic all-fiber cavity.

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Fig. 14. Energy level structures of (a) ${Er}^{3 +}$ , (b) ${Ho}^{3 +}$ , and (c) ${Dy}^{3 +}$ ions.

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Fig. 15. Published laser power from RE-doped fiber laser as a function of operating wavelength^{[206–218" target="_self" style="display: inline;">–218]}.

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Fig. 16. Experimental setups for the high-power heavily ${Er}^{3 +}$ -doped ZBLAN double-clad fiber laser. (a) Experimental setup of the 10-W-level fluoride fiber laser at 2.78 µm^[223] (Copyright © 2006 Optical Society of America). (b) Experimental setup of the cascade laser operating at $\sim 2.8$ and $\sim 1.6 µ m$ ^[227] (Copyright © 2017 Optical Society of America). (c) Experimental setup of the 42 W fluoride fiber laser at 2.824 µm^[228] (Copyright © 2018 Optical Society of America).

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Fig. 17. Experimental setups for the ${Ho}^{3 +} / \Pr^{3 +}$ -doped fluoroaluminate fiber lasing at $\sim 2.9 μ m$ . (a) Experimental setup of the 173 mW fluoroaluminate glass fiber laser at 2.866 µm^[230] (Copyright © 2020 Optical Society of America). (b) Experimental setup of the tunable ${Ho}^{3 +} / \Pr^{3 +}$ co-doped ${AlF}_{3}$ fiber laser operating at $λ \sim 2.8 42 - 2.9 38 μ m$ ^[231] (Copyright © 2021 Optical Society of America). (c) Experimental setup of the 2.86 µm fiber laser with a fiber Bragg grating high reflector (HR) and Fresnel-reflection output coupler (LR)^[233] (Copyright © 2022 Optical Society of America).

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Fig. 18. Schematic of the mid-infrared fiber laser system developed by Tianjin University. (a) Experimental setup of the 33.8 W fluoride fiber laser at 2.87 µm^[236]. (b) Experimental schematic of the all-fiber low-feedback 2.8 µm Er-doped ZBLAN fiber laser^[239] (Copyright © 2025 Optical Society of America).

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Fig. 19. (a) Schematic diagram of the resonantly pumped ${Dy}^{3 +}$ dope ZBLAN fiber laser^[240] (Copyright © 2016 Optical Society of America) and (b) experimental setup of the 10-W-level Dy-doped fluoride fiber laser at 3.24 µm^[242] (Copyright © 2019 Optical Society of America).

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Fig. 20. (a) Energy-level diagram of erbium-doped ZBLAN showing the pumping scheme for a typical mid-IR lasing transition that is pumped using the conventional technique and the DWP concept^[251] (Copyright © 2014 Optical Society of America). (b) Experimental setup of the monolithic DWP ${Er}^{3 +} : {ZrF}_{4}$ fiber laser (HR-FBG, high-reflectivity FBG; LR-FBG, low-reflectivity FBG)^[254] (Copyright © 2017 Optical Society of America). (c) Experimental setup of the 3.55 µm ${Er}^{3 +} : {ZrF}_{4}$ DWP all-fiber laser system^[259] (Copyright © 2022 Optical Society of America).

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Fig. 21. 3.5 µm laser of 16.4 W from Er-doped fluoride fiber. (a) Experimental setup, (b) 3.5 µm output power curve, and (c) 3.5 µm laser spectrum^[264].

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Fig. 22. (a) 3920 nm laser cavity layout with 1.7 W output, (b) silica-to- ${ZrF}_{4}$ , and (c) ${ZrF}_{4} - to - {InF}_{3}$ splices. (d) Cross section of the ${Ho}^{3 +} : {InF}_{3}$ fiber^[267] (Copyright © 2024 Optical Society of America) and (e) experimental setup of the 3.8 µm monolithic ${Er}^{3 +} : {ZrF}_{4}$ DWP all-fiber laser system^[268].

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Fig. 23. Schematic setup for SC generation^[270].

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Fig. 24. Supercontinuum laser system pumped by noise-like pulses. (a) Experimental setup, (b) output spectrum evolution with pump power, (c) output power, and (d) power conversion efficiency versus pump power at different pulse widths^[277] (Copyright © 2023 Optical Society of America).

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Fig. 25. Supercontinuum laser based on 1.9–4.9 µm ${InF}_{3}$ fiber. (a) Experimental setup, (b) supercontinuum spectrum based on ${InF}_{3}$ fiber, and (c) SC power with respect to the output power of the SMF2^[280] (Copyright © 2020 Optical Society of America).

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Fig. 26. Absorption strength of some typical trace gas molecules in the mid-infrared range^[295].

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Fig. 27. Absorption spectrum of water molecules^[302].

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Fig. 28. Transmission efficiency of indium fluoride fiber under experimental conditions^[345].

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Table 1. Maximum Phonon Energy of Fluoride Glass
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Table 1. Maximum Phonon Energy of Fluoride Glass
Glass Fluorozirconate glass Fluoroaluminate glass Fluoroindate glass
Maximum phonon energy ( ${cm}^{- 1}$ ) 550–600 600–650 480–520

Table 2. Typical Compositions and Thermal Characteristic Temperatures of Fluoride Glasses

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Table 2. Typical Compositions and Thermal Characteristic Temperatures of Fluoride Glasses


Type of glass	Nominal components [% (mole fraction)]	Tg (°C)	ΔT (°C)	Ref.
Fluorozirconate glass	${20 ZrF}_{4} - {10 ZnF}_{2} - {20 AlF}_{3} - {5 YF}_{3} - {10 BaF}_{2} - 35 LiF$	320	72	[119]
${20 ZrF}_{4} - {10 ZnF}_{2} - {20 AlF}_{3} - {5 YF}_{3} - {10 BaF}_{2} - 30 LiF - 5 KF$	250	140	[119]
${57 ZrF}_{4} - {34 BaF}_{2} - {5 LaF}_{3} - {3 AlF}_{3}$	316	82	[120]
${53 ZrF}_{4} - {20 BaF}_{2} - {4 LaF}_{3} - {3 AlF}_{3} - 20 NaF$	268	80	[121]
${50 ZrF}_{4} - {33 BaF}_{2} - {10 YF}_{3} - {7 AlF}_{3}$	340	75	[122]
Fluoroaluminate glass	$30.2 {AlF}_{3} - 10.6 {BaF}_{2} - 20 .2 {CaF}_{2} - 8.3 {YF}_{3} - 13.2 {SrF}_{2} - 3.5 {MgF}_{2} - 10 .2 {ZrF}_{4} - 3.8 NaF$	393	135	[123]
${30 AlF}_{3} - {15 BaF}_{2} - {20 YF}_{3} - {25 PbF}_{2} - {10 MgF}_{2}$	367	138	[78]
${30 AlF}_{3} - {10 BaF}_{2} - {15 CaF}_{2} - {15 YF}_{3} - {20 PbF}_{2} - {5 MgF}_{2}$	365	125	[78]
${37 AlF}_{3} - {12 BaF}_{2} - {15 CaF}_{2} - {15 YF}_{3} - {9 SrF}_{2} - {12 MgF}_{2}$	426	126	[124]
${35 AlF}_{3} - {10 BaF}_{2} - {20 CaF}_{2} - {15 YF}_{3} - {10 SrF}_{2} - {10 MgF}_{2}$	428	81	[88]
Fluoroindate glass	${50 InF}_{3} - {10 BaF}_{2} - {40 YF}_{3}$	333	83	[125]
${40 InF}_{3} - {20 BaF}_{2} - {20 SrF}_{2} - {20 ZnF}_{2}$	301	87	[98]
${40 InF}_{3} - {15 BaF}_{2} - {20 SrF}_{2} - {5 CaF}_{2} - {20 ZnF}_{2}$	292	91	[98]
${30 InF}_{3} - {15 BaF}_{2} - {20 SrF}_{2} - {30 ZnF}_{2} - 5 NaF$	291	89	[98]
${15 InF}_{3} - {20 GaF}_{3} - {15 ZnF}_{2} - {30 PbF}_{2} - {20 CdF}_{2}$	248	112	[125]

Table 3. Comparison of Properties of Several Classic Fluoride Glasses^*

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Table 3. Comparison of Properties of Several Classic Fluoride Glasses^*


Type of glass	Fluorozirconate glass	Fluoroaluminate glass	Fluoroindate glass
Component	ZBYA	ZBLAN	ABCYSM	AZYSB	ABCYSMLZ	IZBGSPLYL
$v$	0.22	0.31	0.31	—	0.23	0.295
$α$ ( $10^{- 6} / K$ )	19.4	17.2	15.66	19.12	17.45	20.93
$E$ (Gpa)	55.9	58.3	72.74	67.92	61	57.07
$σ F$ ( $Mpa \cdot m^{1 / 2}$ )	0.45	0.32	0.574	0.8	0.44	0.219
$R_{s}$ ( $W / m^{1 / 2}$ )	0.197	0.138	0.367	0.320	0.296	0.219
Ref.	[126]	[126,127]	[128]	[79]	[128]	[129]

Table 4. Water Immersion Results for Typical Fluoride Glass

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Table 4. Water Immersion Results for Typical Fluoride Glass


Type of glass	Fluorozirconate glass	Fluoroaluminate glass	Fluoroindate glass
Component	ZBLAN	ZBYA	AYF	IZBGSLPN
Weight loss (%)	2.003	0.79	0.027	0.12
$T_{3000 nm}$ (%) before immersion	90.8	91.1	94.5	—
$T_{3000 nm}$ (%) after drying	0	13.9	91.7	—
Ref.	[126]	[126]	[128]	[129]

Table 5. Key Properties of Fluorozirconate, Fluoroaluminate, and Fluoroindate Glasses

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Table 5. Key Properties of Fluorozirconate, Fluoroaluminate, and Fluoroindate Glasses


Property	Fluorozirconate (e.g., ZBLAN)	Fluoroaluminate (e.g., AYF)	Fluoroindate (e.g., IZBGSPLYL)
Typical composition	${ZrF}_{4} - {BaF}_{2} - {LaF}_{3} - {AlF}_{3} - NaF$	${AlF}_{3} - {BaF}_{2} - {CaF}_{2} - {YF}_{3} - {SrF}_{2} - {MgF}_{2}$	${InF}_{3} - {ZnF}_{2} - {BaF}_{2} - {GaF}_{3} - {SrF}_{2} - LiF - {YF}_{3} - {LaF}_{3}$
Maximum phonon energy ( ${cm}^{- 1}$ )	$\sim 580$	$\sim 590$	$\sim 420$
Infrared cut-off edge band (μm)	$\sim 9$	$\sim 8.5$	$\sim 11$
Thermal stability $Tg / Δ T$	Moderate 260/98	High 425/78	Low to moderate 260/79
Chemical durability	Moderate (prone to hydrolysis)	High (resistant to moisture)	Low to moderate (improved with ${GaF}_{3}$ )
Rare-earth solubility	High ( ${Er}^{3 +}$ , ${Ho}^{3 +}$ , and ${Dy}^{3 +}$ )	Moderate (limited by ${Al}^{3 +}$ coordination)	High ( ${In}^{3 +}$ accommodates RE ions)
Fabrication challenge	Crystallization during cooling	High melting temperatures ( $> 1$ ,200°C)	Volatility of ${InF}_{3}$ during melting
Primary application	Mid-IR fiber lasers (2.7–3.8 µm)	High-power lasers, harsh environments	Extended mid-IR lasers (3–5 µm)

Table 6. Performance Parameters of Typical Commercial Fluoride Fibers

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Table 6. Performance Parameters of Typical Commercial Fluoride Fibers


Company	Fiberlabs	Thorlabs	Le Verre Fluoré
Fiber	Fluoroaluminate	ZBLAN	ZBLAN	Fluoroindate	ZBLAN	Fluoroindate
Transmission range (μm)	0.35–3.5	0.3–4	0.29–4.5	0.3–5.5	0.3–4.3	0.3–5.5
Core index	1.46	1.51	—	—	—	—
Core diameter (μm)	200	9	9	9	6.5	16
Numerical aperture	0.22	0.16–0.26	0.19	0.26	0.08–0.35	0.2
Fiber loss (dB · m⁻¹)	$< 0.1 @ 2.9 µ m$	0.3@4 µm	$< 0.2 @ 2.3 - 3.6 μm$	$< 0.45 @ 3.2 - 4.6 μm$	$\leq 0.05 @ 0.3 - 3.4 μm$	$\leq 0.2 @ 3.4 - 4.0 μm$
RE-doped fiber loss (dB · m⁻¹)	—	${Er}^{3 +}$ -doped 0.3@2.0 µm	—	—	${Er}^{3 +}$ -doped 0.2@2.0 µm	${Ho}^{3 +}$ -doped 0.7@1.5 µm 0.3@3.0 µm
Core deviation (%)	$< 5.0$	$< 1 1.1$	$< 5.6$	$< 5.6$	—	—

Table 7. Summary of the Literature on continuous-wave (CW) Mid-IR 2.7–3.0 µm Fluoride Fiber Lasers

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Table 7. Summary of the Literature on continuous-wave (CW) Mid-IR 2.7–3.0 µm Fluoride Fiber Lasers


λ_Output (μm)	λ_Pump (nm)	Slope efficiency (%)	Output power	Year	Fiber host	Ref.
2.714	476.5		250 µW	1988	${Er}^{3 +} : ZBLAN$	[219]
2.79	970	25	1.04 W	1999	${Er}^{3 +} : ZBLAN$	[222]
2.785	975	21.3	9 W	2006	${Er}^{3 +} : ZBLAN$	[223]
2.938	980	22	30.5 W	2015	${Er}^{3 +} : ZBLAN$	[226]
2.825	976	50	13 W	2017	${Er}^{3 +} : ZBLAN$	[227]
2.824	980	22.9	41.6 W	2018	${Er}^{3 +} : ZBLAN$	[228]
2.838	980	15.2	35 W	2019	${Er}^{3 +} : ZBLAN$	[229]
2.9	1150	10.4	173 mW	2020	${Ho}^{3 +} / \Pr^{3 +} : {AlF}_{3}$	[230]
2.84	1150	10.3	1.13 W	2021	${Ho}^{3 +} / \Pr^{3 +} : {AlF}_{3}$	[231]
2.8 (quasi-CW)	976	29	70 W	2021	${Er}^{3 +} : ZBLAN$	[232]
2.863	1150	17.7	1.006 W	2021	${Ho}^{3 +} / \Pr^{3 +} : {AlF}_{3}$	[233]
2.9	1150	24	2.16 W	2022	${Ho}^{3 +} / \Pr^{3 +} : ZBYA$	[126]
2.8	1720	23.7	660 mW	2022	${Er}^{3 +} : ZBLAN$	[234]
2.864	1150	21.14	1.35 W	2022	${Ho}^{3 +} / \Pr^{3 +} : {InF}_{3}$	[235]
2.87	976	26.4	33.8 W	2023	${Er}^{3 +} : ZBLAN$	[236]
2.86	1642+	53.7	1.65 W	2024	${Ho}^{3 +} : {InF}_{3}$	[237]
1976
2.866	1150	29.3	4.25 W	2024	${Ho}^{3 +} / \Pr^{3 +} : {AlF}_{3}$	[238]
2.87	1150	29	5.82 W	2024	${Ho}^{3 +} : {AlF}_{3}$	[128]
2.8	976	22.1	12.5 W	2025	${Er}^{3 +} : ZBLAN$	[239]

Table 8. Summary of the Literature on CW Mid-IR $\sim 3.5 µ m$ Fluoride Fiber Lasers

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Table 8. Summary of the Literature on CW Mid-IR $\sim 3.5 µ m$ Fluoride Fiber Lasers


$λ_{Output}$ (μm)	$λ_{Pump}$ (nm)	Slope efficiency (%)	Output power	Year	Institution	Ref.
3.45	653	3	8.5 mW	1991	Technische Universität Braunschweig	[249]
3.5	974 + 1973	6.5	40 mW	2013	The University of Adelaide	[250]
3.604	985 + 1973	16	260 mW	2014	The University of Adelaide	[251]
3.5	985 + 1973	27.3	370 mW	2015	The University of Adelaide	[252]
3.44	974 + 1976	19	1.5 W	2015	Laval University	[253]
3.55	976 + 1976	26.4	5.6 W	2017	Laval University	[254]
3.68	970 + 1973	25.14	0.62 W	2017	Shanghai Jiao Tong University	[255]
3.42	976 + 1976	38.6	3.4 W	2019	Laval University	[256]
$\sim 3.5$	976 + 1973	48	1.72 W	2019	Hunan University	[257]
$\sim 3.5$	655 + 1981	31.5	1.72 W	2021	University of Electronic Science and Technology of China	[258]
3.55	980 + 1976	51.3	14.9 W	2021	Laval University	[259]
3.54	976 + 1973	10.33	2.32 W	2022	Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences	[260]
$\sim 3.5$	659	10.7	0.95 W	2022	University of Electronic Science and Technology of China	[261]
3.47	1990	36	7.2 W	2023	Tianjin University	[262]
2.8/3.6	980 + 1150	6.9	0.96 W/0.32 W	2024	Harbin Engineering University	[263]
3.46	976 + 1990	37.8	16.4 W	2024	Tianjin University	[264]
3.549	981 + 1976	41.7	10.1 W	2024	Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences	[265]

Table 9. Research Progress of Supercontinuum Lasers Based on Fluoride Fibers

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Table 9. Research Progress of Supercontinuum Lasers Based on Fluoride Fibers


Fiber	Pump laser wavelength (μm)	Supercontinuum spectrum range (μm)	Output power (W)	Ref.
ZBLAN	1.54	0.8–4.0	10.5	[272]
1.9–2.6	1.90–3.35	30	[273]
1.9–2.6	2.0–4.1	20.6	[274]
1.9–2.4	1.9–4.0	5.4	[275]
2	1.90–3.68	33.1	[277]
Fluoroindate	2.75	2.4–5.4		[278]
1.8–2.6	1–5	1	[279]
1.9–2.6	1.9–4.9	11.8	[280]

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Shunbin Wang, Shijie Jia, Yiguang Jiang, Long Zhang, Pengfei Wang, Yichun Liu, "Mid-IR fluoride fibers: materials, fabrication, and fiber laser applications," Photon. Insights 4, R07 (2025)

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Paper Information

Category: Review Articles

Received: Apr. 29, 2025

Accepted: Jun. 24, 2025

Published Online: Aug. 1, 2025

The Author Email: Long Zhang (lzhang@siom.ac.cn), Pengfei Wang (pfwang@nenu.edu.cn)

DOI:10.3788/PI.2025.R07

CSTR:32396.14.PI.2025.R07

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Maximum Phonon Energy of Fluoride Glass

Table 1. Maximum Phonon Energy of Fluoride Glass

Table 2. Typical Compositions and Thermal Characteristic Temperatures of Fluoride Glasses

Table 2. Typical Compositions and Thermal Characteristic Temperatures of Fluoride Glasses

Table 3. Comparison of Properties of Several Classic Fluoride Glasses*

Table 3. Comparison of Properties of Several Classic Fluoride Glasses*

Table 4. Water Immersion Results for Typical Fluoride Glass

Table 4. Water Immersion Results for Typical Fluoride Glass

Table 5. Key Properties of Fluorozirconate, Fluoroaluminate, and Fluoroindate Glasses

Table 5. Key Properties of Fluorozirconate, Fluoroaluminate, and Fluoroindate Glasses

Table 6. Performance Parameters of Typical Commercial Fluoride Fibers

Table 6. Performance Parameters of Typical Commercial Fluoride Fibers

Table 7. Summary of the Literature on continuous-wave (CW) Mid-IR 2.7–3.0 µm Fluoride Fiber Lasers

Table 7. Summary of the Literature on continuous-wave (CW) Mid-IR 2.7–3.0 µm Fluoride Fiber Lasers

Table 8. Summary of the Literature on CW Mid-IR ∼3.5 µm Fluoride Fiber Lasers

Table 8. Summary of the Literature on CW Mid-IR ∼3.5 µm Fluoride Fiber Lasers

Table 9. Research Progress of Supercontinuum Lasers Based on Fluoride Fibers

Table 9. Research Progress of Supercontinuum Lasers Based on Fluoride Fibers

Table 3. Comparison of Properties of Several Classic Fluoride Glasses^*

Table 3. Comparison of Properties of Several Classic Fluoride Glasses^*

Table 8. Summary of the Literature on CW Mid-IR $\sim 3.5 µ m$ Fluoride Fiber Lasers

Table 8. Summary of the Literature on CW Mid-IR $\sim 3.5 µ m$ Fluoride Fiber Lasers