ALUMINOPHOSPHATE GLASS COMPOSITION

Abstract

The invention relates to phosphate-based glasses suitable for use as a solid laser medium, doped with Er3+ and sensitized with Yb, in “eye-safe” applications. In particular, the invention relates to improving the physical properties of such phosphate-based laser glass composition, particularly with regards to strength of the glass structure and improved thermal shock resistance.

Claims

1. A phosphate glass composition comprises (based on mol %): TABLE-US-00012 P.sub.2O.sub.5 55.00-65.00 Al.sub.2O.sub.3  4.00-20.00 K.sub.2O 4.00-8.00 Na.sub.2O  8.00-18.50 Li.sub.2O 00.0-2.00 Rb.sub.2O 0.00-2.00 Cs.sub.2O 0.00-2.00 SiO.sub.2  0.00-12.00 MO 0.00-7.00 Bi.sub.2O.sub.3 0.00-3.00 TeO.sub.2 0.00-3.00 GeO.sub.2 0.00-1.00 Nb.sub.2O.sub.3 0.00-2.00 Nb.sub.2O.sub.5 0.00-2.00 Cr.sub.2O.sub.3 0.00-0.50 CeO.sub.2 0.00-0.30 Er.sub.2O.sub.3 0.03-1.00 Yb.sub.2O.sub.3  5.00-10.00 R.sub.2O 12.00-25.00 wherein R.sub.2O=the sum of the amounts of Li.sub.2O, Na.sub.2O, K.sub.2O, Rb.sub.2O and Cs.sub.2O; MO=the sum of the amounts of MgO, CaO, SrO, BaO, and ZnO; and wherein the sum of Al.sub.2O.sub.3, SiO.sub.2, and Na.sub.2O is 20.00-28.00 mol %.

2. A glass composition according to claim 1, wherein the amount of P.sub.2O.sub.5 is 55.00-60.00 mol %.

3. A glass composition according to claim 1, wherein the amount of P.sub.2O.sub.5 is 57.00-60.00 mol %.

4. A glass composition according to claim 1, wherein the amount of Al.sub.2O.sub.3 is 5.00-7.00 mol %.

5. A glass composition according to claim 1, wherein the amount of Al.sub.2O.sub.3 is 10.00-12.00 mol %.

6. A glass composition according to claim 1, wherein the amount of Al.sub.2O.sub.3 is 15.00-18.00 mol %.

7. A glass composition according to claim 1, wherein the amount of K.sub.2O is 5.00-7.00 mol %.

8. A glass composition according to claim 1, wherein the amount of K.sub.2O is 5.50-6.5 mol %.

9. A glass composition according to claim 1, wherein the amount of Na.sub.2O is 9.00-16.00 mol %.

10. A glass composition according to claim 1, wherein the amount of Na.sub.2O is 10.00-15.00 mol %.

11. A glass composition according to claim 1, wherein the amount of Li.sub.2O is 0.00-1.00 mol %.

12. A glass composition according to claim 1, wherein the amount of Rb.sub.2O is 0.00-1.00 mol %.

13. A glass composition according to claim 1, wherein the amount of Cs.sub.2O is 0.00-1.00 mol %.

14. A glass composition according to claim 1, wherein the amount of SiO.sub.2 is 0.00-11.00 mol %.

15. A glass composition according to claim 1, wherein the amount of SiO.sub.2 is 4.00-11.00 mol %.

16. A glass composition according to claim 1, wherein the amount of MO is 0.00-6.00 mol %.

17. A glass composition according to claim 1, wherein the amount of MO is 0.00-5.00 mol %.

18. A glass composition according to claim 1, wherein the amount of TeO.sub.2 is 0.00-2.50 mol %.

19. A glass composition according to claim 1, wherein the amount of TeO.sub.2 is 0.00-2.00 mol %.

20. A glass composition according to claim 1, wherein the amount of GeO.sub.2 is 0.00-0.50 mol %.

21. A glass composition according to claim 1, wherein the amount of GeO.sub.2 is 0.00-0.10 mol %.

22. A glass composition according to claim 1, wherein the amount of Nb.sub.2O.sub.5 is 0.50-2.00 mol %.

23. A glass composition according to claim 1, wherein the amount of Nb.sub.2O.sub.5 is 0.50-1.50 mol %.

24. A glass composition according to claim 1, wherein the amount of Sb.sub.2O.sub.3 is 0.05-0.30 mol %.

25. A glass composition according to claim 1, wherein the amount of Sb.sub.2O.sub.3 is 0.05-0.20 mol %.

26. A glass composition according to claim 1, wherein the amount of Cr.sub.2O.sub.3 is 0.01-0.10 mol %.

27. A glass composition according to claim 1, wherein the amount of Cr.sub.2O.sub.3 is 0.02-0.05 mol %.

28. A glass composition according to claim 1, wherein the amount of CeO.sub.2 is 0.00-0.20 mol %.

29. A glass composition according to claim 1, wherein the amount of CeO.sub.2 is 0.10-0.20 mol %.

30. A glass composition according to claim 1, wherein the amount of Er.sub.2O.sub.3 is 0.03-0.10 mol %.

31. A glass composition according to claim 1, wherein the amount of Er.sub.2O.sub.3 is 0.03-0.08 mol %.

32. A glass composition according to claim 1, wherein the amount of Er.sub.2O.sub.5 is 0.05-0.08 mol %.

33. A glass composition according to claim 1, wherein the amount of Yb.sub.2O.sub.3 is 6.00-10.00 mol %.

34. A glass composition according to claim 1, wherein the amount of Yb.sub.2O.sub.3 is 7.00-10.00 mol %.

35. A glass composition according to claim 1, wherein the amount of R.sub.2O is 14.00-22.00 mol %.

36. A glass composition according to claim 1, wherein the amount of R.sub.2O is 15.00-21.00 mol %.

37. A glass composition according to claim 1, wherein the amount of the sum of Al.sub.2O.sub.3, SiO.sub.2, and Na.sub.2O is 22.00-28.00 mol %.

38. A glass composition according to claim 1, wherein the amount of the sum of Al.sub.2O.sub.3, SiO.sub.2, and Na.sub.2O is 25.00-28.00 mol %.

39. In a solid state laser system comprising a solid gain medium and a pumping source, the improvement wherein said solid gain medium is a glass having a composition in accordance with claim 1.

40. A method for generating a laser beam pulse comprising flashlamp pumping or diode pumping a glass composition according to claim 1.

Description

EXAMPLES

[0048] In the present case, 21 modifications of the LG940 glass were prepared. Initially, glasses were prepared the prescribed proportions of various powdered raw materials were mixed together such that the total amount of each batch would produce approximately 200 g of cast glass. These batches were placed into fused silica crucibles and placed into a resistance furnace at temperatures exceeding 1,000° C. Once melted and refined, the molten glass was cast and annealed over a period of time. Those glasses that were determined to be a good fit for the thermodynamical conditioning involved in standard manufacturing processes (e.g., readily formed a glass and showed a decrease in the thermal expansion coefficient) were repeated at a larger scale (e.g., 0.5 L). The larger scale melting was accomplished using electrical induction, and the molten liquid was stirred and refined at temperatures in excess of 1,000° C. Once the casting and forming processes were complete, samples for measurements were fabricated from these glasses. All required properties and measurements for analysis were completed on each manufactured composition.

[0049] Density is measured using the Archimedes method with a standard accuracy of ±0.003 g/cm.sup.3. The coefficient of thermal expansion, CTE, (α.sub.20-300° C., ±0.03 ppm/° C.) and the glass transformation point, T.sub.g, (±5° C.) are determined using the dilatometric analysis. Dilatometric, beam bending (3-point) and softening point methods are used to determine the temperature corresponding to particular viscosities, including annealing point (3.16×10.sup.14 poise), strain point (1×10.sup.13 poise) and softening point (3.98×10.sup.7 poise). High temperature rheometry is used to determine the melt viscosity around the working point of the glass (1×10.sup.4 poise). These individual points were then fit using the well-known Volger-Fulcher-Tammann (VFT) model.

[0050] Differential thermal analysis (DTA) is used to examine the relative devitrification stability of each composition. Hardness and fracture toughness are measured using a Vickers indentation method with a 3N load. Young's modulus is determined using an impulse excitation technique. Refractive index measurements are made using a standard V-block method and these are then used to calculate values for dispersion, V′″ refractive index at the lasing wavelength, and the nonlinear refractive index, n2. Transmission curves are obtained using a Perkin Elmer Lambda 900® or Lambda 1050® spectrophotometer using prescribed scan conditions within the window of 200 nm to 2500 nm. The dn/dT measurements are made using the solid etalon method. The measurement is made at respective wavelengths for the ions of interest and over a temperature range from 25° C.-30° C. The instrument measures the temperature dependent shift in wavelength of the interference fringe (Δλ) as the temperature is cycled up and down through the temperature range. The collected data is then used to calculate the dn/dT of the sample over the temperature interval. See S. George et al., SPIE Photonics West, Paper No. 9342-46, PW15L-LA101-71, 2015 presentation, hereby incorporated by reference.

[0051] The presence of hydroxyl impurities in the glass can non-radiatively quench the laser excited state. See G. C. Righini et al., “Photoluminescence of Rare-Earth-Doped Glasses,” Rivista del Nuovo Cimento, 28(12), 1-53 (2005). Conventional melt-quenching processes used for manufacturing glasses can introduce residual OH″ species relatively easily, which will then affect the fluorescence decay of Er.sup.3+ ions at 1.5 μm, resulting in reduced quantum efficiencies. The impact is typically most noticeable in the lifetime measurements. As a result, the residual hydroxyl content is monitored for all the glasses produced by utilizing the absorption features present near 3333 cm.sup.−1 (3.0 μm) and 3000 cm.sup.−1 (3.333 μm). The method utilized assumes proportionality between the concentration of the OR species and the measured absorption. The amplitude of the hydroxyl absorption at the two prior mentioned wavelengths allows for the estimation of concentration by the Beer-Lambert law. The ppm level concentrations in the glass are not explicitly calculated, but rather are set a value for maximum tolerable level for absorption. For a laser grade glass gain element, the absorption is desirably less than 2.0 cm.sup.−1 and most preferably less than 1.8 cm.sup.−1 at the wavelength of 3000 nm regardless of the active ion present in the glass.

[0052] Fluorescence emission lifetime measurements are completed on a 10 mm cube sample and also on a powdered glass layer (in order to avoid self-pumping by the Er ions, leading to longer decay times from the cubed samples). The samples are prepared from each melt with two adjacent sides polished and the remaining four sides being fine ground. The samples are excited through one polished face at nominally 980 nm with a laser diode, and emission is collected thorough the orthogonal polished face. The fluorescence lifetimes of erbium and ytterbium are measured separately by selecting 1550 nm and 1000 nm emitted light with 10 nm FWHM interference filters. Careful analysis of the temporal emission from ytterbium also allows for the determination of energy transfer efficiency for each of the samples doped with both erbium and ytterbium. The fluorescence lifetime, designated as τ, is then calculated by fitting the data from t=0 to a point where the intensity has fallen to less than 1/e of its initial value. Additional details are described in S. George et al. SPIE Photonics West, Paper No. 9342-46, PW15L-LA101-71, 2015 presentation, hereby incorporated by reference. See also http://www.pti.nj.com/brochures/QuantaMaster.pdf, E. Desurvire, Erbium-doped Fiber Amplifiers Principles and Applications, John Wiley and Sons, pg. 244-245 (1994), and S. George et al, Tougher Glasses for Eye-safe Lasers, Proc. SPIE 9466, Laser Technology for Defense and Security XI, 94660E (20 May 2015) [http://spie.org/Publications/Proceedings/Paper/10.1117/12.2176235?origin id=x4318], hereby incorporated by reference.

[0053] The QuantaMaster™ 50 NIR steady state spectrofluorometer from Photon Technology International [See D. E. McCumber, Phys. Rev. 134, A299 (1964)] is used for all emission measurements. The instrument uses a TE-cooled InGaAs detector where the sensitivity is enhanced by using an optical chopper to modulate the excitation light and a lock-in amplifier on the detector end.

[0054] Laser properties of radiative lifetime and cross sections for stimulated absorption and emission as a function of wavelength are calculated for Er and Yb doped glasses by a simplification of Judd-Ofelt (JO) theory often referred to in the literature as the Fuchtbauer-Ladenburg (FL) relation. A brief description is provided in S. George et al, Tougher Glasses for Eye-safe Lasers, Proc. SPIE 9466, Laser Technology for Defense and Security XI, 94660E (20 May 2015), hereby incorporated by reference. Additional details are provided in S. George et al. SPIE Photonics West, Paper No. 9342-46, PW15L-LA101-71, 2015 presentation, http:/www.pti-nj.com/brochures/QuantaMaster.pdf, E. Desurvire, Erbium-doped Fiber Amplifiers Principles and Applications, John Wiley and Sons, pg. 244-245 (1994), hereby incorporated by reference.

[0055] Radiative lifetime is determined by the following equation (1):

1/τ.sub.rad=8πcn.sup.2[(2J′+1)/λ.sup.4.sub.abs max(2J+1)]∫α(λ)dλ  (1)

where J′ and J are the total momentum of the lower and upper levels, in the case of erbium 15/2 and 13/2, respectively, and the integration is taken from 1400 nm to 1700 nm.

[0056] The emission cross section is then determined by the following equation (2):

σ.sub.emm(λ)=λ.sup.4g(λ)/[8πcn.sup.2τ.sub.rad]  (2)

where g(λ) is the lineshape function obtained from the emission data, I(λ), collected with a PTI QM50 fluorescence spectrometer, g(λ)=I(λ)∫I(λ)dλ (equation (3)).

[0057] The compositions of the 22 glasses prepared in the initial small scale manufacturing (200 g) are listed in Tables 1A and 1B below. During the initial small scale manufacturing of the 22 glasses (LG940 and 21 modifications), one composition (Example 14) showed to be wholly unsuitable for the melt-quenching processes utilized. Two more compositions (Examples 13 and 22) showed tendencies for devitrification. The remaining nineteen glasses were stable for all processes. A set of properties including refractive index (measured at the Fraunhofer “D” line, the center of the yellow sodium double emission at 589 nm), dispersion, density, coefficient of thermal expansion (CTE), glass transition temperature (Tg), and the fluorescence lifetimes for Er and Yb were collected on these 19 glasses. Based on these properties, seven compositions were selected for larger scale manufacturing and detailed characterization. Table 2 lists standard material properties of the 7 glasses for comparison. Nominal ion concentrations in all of these glasses are 0.2×10.sup.20 ions/cm.sup.3 Er and 23.5×10.sup.20 ions/cm.sup.3 Yb.

[0058] From a glass strength perspective, low CTE, high thermal conductivity, and a high value for fracture toughness are key properties. Fracture of a laser component occurs when induced stresses exceed the tensile strength during pumping. The theoretical tensile strength of a defect free material may be approximated by the following equation (4)

σ.sub.max≈E/10.  (4)

where E is the Young's modulus (GPa). See, e.g., R. Feldman et al., “Thermochemical strengthening of Nd:YAG laser rods”, Proc. SPIE 6190, Solid State Lasers and Amplifiers II, 619019 (Apr. 17, 2006).

[0059] In the real world, there is a very large difference between the theoretical fracture limit of a material in the Giga-Pa range and the achievable component fracture limit in a cavity which is in the Mega-Pa limit. The discrepancy is especially large in the case of an actively cooled laser rod under repetitive heat load. The descriptive formalism starts with the heat dissipated by a rod per unit volume as a function of the absorbed pump power. In the case of Er, there is also energy transfer upconversion that affects the dissipated heat in a gain material, but this is ignored in the simple treatment. A fraction of the absorbed laser pump energy may be converted into heat by quantum defect heating. The total heat dissipated by the laser rod, P.sub.h, is then a function of optical pump power and the fractional thermal load, as shown in equation (5):

P.sub.h=(1−λP/λL)P.sub.p.  (5)

[0060] Thermal gradients exist in a cooled laser rod (or in other geometries like a slab), where the center of the rod is hotter than the surface of the rod that is in contact with the cooling medium. In this case, the power of the heat dissipated can be related to the temperature differential by equation (6):

P.sub.h=T(0)−T(r.sub.0).Math.4πKL  (6)

where T(0) and T(r.sub.0) are the temperatures at the rod center and the rod surface, K is the thermal conductivity of the material, and L is the total length of the rod. Then, the edge to center heat differential is proportional to the absorbed power and the thermal conductivity and these temperature gradients induce mechanical stresses tangentially, radially, and axially in gain component. When these stresses exceed the tensile strength of the rod, it leads to fracture. See, e.g., W. Koechner, Solid State Laser Engineering, 6th ed., Springer, Berlin, (2006) p. 439-481.

[0061] In the rod case, then, the total surface stress (to rupture) is the vector sum of the tangential and axial components and takes into account the fundamental material properties, as shown in equation (7):

σ.sub.T=[αE/8πK(1−v)].Math.P.sub.hL=√2σ.sub.φ.  (7)

where K is the thermal conductivity is the thermal conductivity measured at 90° C. (K.sub.90C) [W/mK], v is the Poissons ratio, E is Young's modulus (GPa), α is the linear coefficient of thermal expansion (K.sup.−1), and σ.sub.φ is the hoop(tangential) stress. See, e.g., R. Feldman et. al., “Thermochemical strengthening of Nd:YAG laser rods”, Proc. SPIE 6190, Solid State Lasers and Amplifiers II, 619019 (Apr. 17, 2006) and W. Koechner, Solid State Laser Engineering, 6th ed., Springer, Berlin, (2006) p. 439-481.

[0062] Further, the actual rupture stress is a function of the surface finish of a component and related by equation (8):

σ.sub.T=[αE/8πK(1−v)].Math.P.sub.hL=YK.sub.IC/√a  (8)

where K.sub.IC is the indentation fracture toughness (MPa.Math.m.sup.1/2), Y is a fracture orientation/geometry factor and is on the order of unity, and a is the average depth of surface flaws introduced during the grinding and polishing steps of the fabrication procedure.

[0063] In terms of heat dissipated per unit length in the rod, this then becomes equation (9), wherein R.sub.s is thermal shock resistance:

P.sub.h=[8πK(1−v)/αE].Math.σT.Math.L=8πR.sub.sL  (9)

[0064] For materials development purposes, the intrinsic material properties from equation 9 are used as the TM-FOM in order to evaluate the suitability by comparative ranking. Thus, the TM-FOM is described by the thermal shock resistance parameter as set forth in equation (10):

TM-FOM=R.sub.s=K(1−v)K.sub.IC/αE [W/m.sup.1/2]  (10)

See, for example, W. Koechner, Solid State Laser Engineering, 6th ed., Springer, Berlin, (2006) p. 439-481; J. H. Campbell, J. S. Hayden, and A. Marker, High-Power Solid-State Lasers: a Laser Glass Perspective. International Journal of Applied Glass Science, 2: 3-29(2011); and W. F. Krupke, M. D. Shinn, J. E. Marion, J. A. Caird, and S. E. Stokowski, “Spectroscopic, optical, and thermomechanical properties of neodymium- and chromium-doped gadolinium scandium gallium garnet,” J. Opt. Soc. Am. B 3, 102-114 (1986).

[0065] Equation (10) directly provides the maximum thermal load that a surface cooled glass component can tolerate before total failure, especially when considering higher repetition rate operation. Therefore, the best materials will have the largest value for R.sub.s (TM-FOM).

[0066] TM-FOMs are compared in Table 3 for the seven compositions selected for larger scale manufacturing.

[0067] A concise treatment of thermally induced wavefront distortions arising from gain material properties is described in Davis et al., “Thermal lensing of laser materials”, in Laser-Induced Damage in Optical Materials: 2014, Gregory J. Exarhos; Vitaly E. Gruzdev; Joseph A. Menapace; Detlev Ristau; M J Soileau, Editors, Proceedings of SPIE Vol. 9237 (SPIE, Bellingham, W A 2014), 92371. In this paper, the classic case of a uniformly heated cylindrical rod with its outer surface at a constant temperature is presented, such as what would be encountered in the case of a CW-pumped, strongly-cooled rod under steady-state conditions. For the relative ranking of materials during development, as presented in this paper, the thermo-optic response is considered with respect to the change in index as a function of temperature as shown in equation (11):

(T)=n(To)+(n/dT)(T−To).  (11)

[0068] With regard to the medium in which the index change takes place, the following relationship is known from W. Koechner, Solid State Laser Engineering, 6th ed., Springer, Berlin, (2006) p. 439-481:

(dn.sub.abs/dT)=n.sub.med(dn.sub.rel/dT)+n.sub.rel(dn.sub.med/dT)  (12)

where n.sub.abs (absolute) refers to the refractive index with respect to vacuum and n.sub.rel (relative) index with respect to the medium of interest (e.g., air). The dn.sub.med/dT of air is non-negligible amount at −0.93 ppm/K, and this can produce significant differences between measured values of dn.sub.abs/dT and dn.sub.rel/dT [Davis et al., “Thermal lensing of laser materials”, in Laser-Induced Damage in Optical Materials: 2014, Exarhos et al. (eds); Proceedings of SPIE Vol. 9237 (SPIE, Bellingham, W A 2014), 92371].

[0069] For purposes here, where internal changes in refractive index are encountered, dn.sub.abs/dT is the relevant property. The temperature induced dioptric power of the gain material can be related to the dissipated heat in the rod (P.sub.h) and the thermal conductivity by equation (13)

D.sub.thermo=(P.sub.h/πr.sub.o.sup.2K)(dn.sub.abs/dT).  (13)

The data collected for the experimental glasses is compared in table 4.

[0070] Absorption due to the water molecules present in the glass structure was assessed and is presented in table 5 for the glasses being evaluated. As stated previously; for a laser grade glass gain element, the absorption must be less than 2.0 cm.sup.−1 and most preferably less than 1.8 cm.sup.−1 at the wavelength of 3000 nm regardless of the active ion present in the glass.

[0071] The J-O calculated and the measured lifetimes for the Er.sup.3+ laser ion and the measured lifetimes for the Yb sensitizing ion are presented in table 6. An estimate of the quantum yield can be obtained from calculated and measured lifetime ratios [J. S. Hayden, Y. T. Hayden, J. H. Campbell; Effect of composition on the thermal, mechanical, and optical properties of phosphate laser glasses. Proc. SPIE 1277, High-Power Solid State Lasers and Applications, 121 (Aug. 1, 1990)]. This is also given in table 6. The quantum efficiencies will never be unity due to the fact that various nonradiative loss mechanisms will impact the emission lifetime. Significant shortening of the lifetime is observed in the presence of hydroxyl species and transition metal ion impurities such as Cu.sup.2+, Ni.sup.2+, Fe.sup.2+, Co.sup.2+, etc. In the absence of hydroxyl and ionic impurities, measured lifetimes tend to be longer than the calculated radiative lifetimes due to the Er self-pumping as observed in the data presented in table 6. The only exception is Example 17, which shows a shorter measured lifetime than the calculated lifetime. This fits the expected result, considering the high OH-absorption found in table 5 for this particular glass.

[0072] Calculated laser properties for the Er3 laser ion is given in table 7. As mentioned above L-FOMs are calculated by the equation L-FOM=σ.sub.em*(τ.sub.meas/τ.sub.rad).

TABLE-US-00004 TABLE 1A Examples of Phosphate-based Glass Compositions (mol %) doped with Er.sup.3+ and sensitized with Yb.sup.3+ Metal Oxide EXAMPLES Content 2 3 4 5 6 7 8 9 10 11 P.sub.2O.sub.5 54.80 58.00 58.00 58.00 58.00 58.00 58.00 58.00 58.00 58.00 Al.sub.2O.sub.3 7.35 7.35 8.35 6.35 6.35 6.35 6.35 11.35 16.35 6.352 K.sub.2O 6.46 5.70 5.47 5.47 5.97 5.97 4.97 5.97 5.97 5.97 Na.sub.2O 22.67 18.99 18.24 19.74 18.74 19.72 19.74 14.74 9.74 14.74 MgO 0.500 5.000 Li.sub.2O 1.000 SiO.sub.2 1.000 TeO.sub.2 Bi.sub.2O.sub.3 GeO.sub.2 Nb.sub.2O.sub.3 0.80 0.85 0.845 0.85 0.85 0.84 0.85 0.85 0.85 0.85 Sb.sub.2O.sub.3 0.09 0.010 0.10 0.10 0.10 0.20 0.10 0.10 0.10 0.10 Cr.sub.2O.sub.3 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 CeO.sub.2 0.14 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Er.sub.2O.sub.5 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 Yb.sub.2O.sub.5 8.60 8.77 8.77 8.77 8.77 8.76 8.77 8.77 8.77 8.77 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

TABLE-US-00005 TABLE 1B Examples of Phosphate-based Glass Compositions (mol %) doped with Er.sup.3+ and sensitized with Yb.sup.3+ Metal Oxide EXAMPLES Content 12 13 14 15 16 17 18 19 20 21 22 P.sub.2O.sub.5 58.00 58.00 57.70 58.00 58.00 58.00 58.00 58.00 58.00 57.70 58.00 Al.sub.2O.sub.3 6.35 21.35 26.2 6.35 6.35 6.35 6.35 6.35 6.35 6.32 6.35 K.sub.2O 5.97 3.97 2.96 3.97 2.97 5.97 3.97 2.97 5.97 5.95 5.97 Na.sub.2O 9.74 6.74 2.72 6.74 2.74 9.74 6.74 2.74 17.74 17.66 17.74 MgO 10.00 15.00 20.00 Li.sub.2O SiO.sub.2 10.00 15.00 20.00 TeO.sub.2 2.00 Bi.sub.2O.sub.3 2.00 GeO.sub.2 2.00 Nb.sub.2O.sub.3 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.84 0.85 Sb.sub.2O.sub.3 0.10 0.10 0.10 0.10 0.10 0.010 0.10 0.10 0.10 0.10 0.100 Cr.sub.2O.sub.3 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 CeO.sub.2 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Er.sub.2O.sub.5 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.07 0.06 Yb.sub.2O.sub.5 8.77 8.77 9.25 8.77 8.77 8.77 8.77 8.77 8.77 9.16 8.77 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

TABLE-US-00006 TABLE 2 Material Properties of Glasses Selected for Larger Scale Manufacture Examples Property LG940 4 9 10 11 17 20 21 Refractive Index at 587 nm @ 30° C./hr, n.sub.d 1.5385 1.5385 1.5409 1.5389 1.5391 1.5352 1.5414 1.5583 Dispersion (Abbe Number), V.sub.d 61.84 62.33 62.62 62.44 62.05 62.42 60.77 55.76 Density, ρ [g/cm.sup.3] 3.11 3.10 3.10 3.07 3.09 3.06 3.11 3.26 Linear Coefficient of Thermal Expansion, 119.6 108.6 93.0 78.7 104.3 89.9 113.1 113.1 α.sub.20-300C [10.sup.−7/K] Glass Transition Temperature, Tg [° C.] 456 465 503 541 476 501 451 450 Thermal Conductivity @ 25° C., K.sub.25C [W/mK] 0.50 0.56 0.60 0.64 0.60 0.57 0.54 0.54 Thermal Conductivity @ 90° C., K.sub.90C [W/mK] 0.60 0.60 0.66 0.69 0.60 0.61 0.58 0.58 Young's Modulus, E [GPa] 57.2 60.34 64.80 69.08 61.08 60.24 57.92 59.43 Poisson Ratio, ν 0.26 0.26 0.25 0.24 0.25 0.25 0.26 0.26 Indentation Fracture Toughness for 4.0N Load, 0.61 0.66 0.68 0.76 0.62 0.76 0.64 0.61 K.sub.IC [MPa .Math. m.sup.1/2] Knoop Hardness, HK 380 402.5 430.8 455.0 401.5 412.6 371.4 372

TABLE-US-00007 TABLE 3 TM-FOM Comparison Examples LG940 4 9 10 11 17 20 21 FOM.sub.TM = K.sub.90° C.K.sub.IC(1-ν)/(αE) 0.39 0.45 0.56 0.72 0.44 0.64 0.42 0.39 [W/m.sup.1/2] % improvement from LG940 −14% 43% 85% 13% 64% 6% −1%

TABLE-US-00008 TABLE 4 Thermal-Optical Response Glasses Optical/Thermal/Physical Property LG940 4 9 10 11 17 20 21 Refractive Index at 587 nm @ 30° C./hr, n.sub.d 1.5385 1.5385 1.5409 1.5389 1.5391 1.5352 1.5414 1.5583 Linear Coefficient of Thermal Expansion, 119.6 108.6 93.0 78.7 104.3 89.9 113.1 113.1 α.sub.20-300C [10.sup.−7/K] Thermal Conductivity @ 90° C., K.sub.90C [W/mK] 0.60 0.60 0.66 0.68 0.60 0.60 0.57 0.58 dn/dT @ 1500 nm (absolute) ppm/° C. −5.0 −2.7 −0.7 1.7 −2.1 −0.3 −3.2 −3.0 dn/dT @ 1500 nm (rel. to air) ppm/° C. −3.6 −1.3 0.8 3.2 −0.7 1.2 −1.7 −1.6 TL-FOM from dioptric power, 1/K*dn/dT −8.3 −4.5 −1.1 2.5 −3.5 −0.5 −5.5 −5.2

TABLE-US-00009 TABLE 5 Hydroxyl Content Glasses 9 9 17 17 Property LG940 4 (0.5 L) (3.0 L) 10 11 (0.5 L) (3.0 L) 20 21 OH absorbtion @ 3.0 μm [cm.sup.−1] 0.35 0.78 0.56 0.33 0.39 0.59 1.54 0.45 0.72 0.54 OH absorption @ 3.33 μm [cm.sup.−1] 0.66 1.42 0.92 0.50 0.54 1.06 3.04 0.83 1.31 0.99

TABLE-US-00010 TABLE 6 Calculated and Measured Lifetimes Glasses Property LG940 4 9 10 11 17 20 21 Calculated Radiative Lifetime 8.2 8.3 9.6 10.3 8.8 8.9 8.7 8.6 (ms) Measured fluorescence 9.4 9.5 9.8 10.5 9.5 8.4 9.4 9.4 Lifetime (ms) Er Measured fluorescence 6.8 9.7 10.2 10.2 10.0 8.3 9.2 9.4 Lifetime (ms) Yb Quantum yield (Er ion) 0.87 0.87 0.98 0.98 0.93 1.06 0.93 0.91 (τ.sub.rad/τ.sub.meas.)

TABLE-US-00011 TABLE 7 Er Laser Properties (J-O Method) Examples Laser Property LG940 4 9 10 11 17 20 21 Emission Cross Section, σ.sub.em 0.77 0.76 0.67 0.65 0.72 0.70 0.72 0.67 [×10.sup.−20 cm.sup.2] Peak Emission Wavelength (nm) 1535.1 1535.0 1535.4 1535.7 1535.4 1534.9 1534.9 1534.2 Effective Linewidth (nm) 50.1 49.8 48.8. 46.8 49.4 50.4 50.5 53.3 Linewidth FWHM (nm) 30.3 29.8 28.6 26.5 29.7 30.1 30.8 33.6 Radiative Lifetime (ms) 8.2 8.3 9.6 10.3 8.8 8.9 8.7 8.6 Peak Gain Coefficient at 50% 0.018 0.016 0.015 0.014 0.018 0.015 0.017 0.017 Population Inversion (cm.sup.−1) Wavelength of 50% Inversion 1551.3 1556.1 1537.8 1549.5 1537.6 1537.1 1537.6 1557.2 (nm) L-FOM, 0%  −1%  3%  −4%  0% 11% 0% −8% % improvement from LG940 TM-FOM, 0% −14% 43%   85% 13% 64% 6% −1% % improvement from LG940

[0073] The entire disclosure[s] of all applications, patents and publications, cited herein, are incorporated by reference herein.

[0074] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0075] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.