Gallium lanthanum sulphide (GLS), a crystalline optical glass composed of gallium sulfide and lanthanum sulfide, is a highly anticipated alternative to toxic arsenic-based glasses. As a very important optical material, GLS has been widely used in a wide range of optoelectronic fields, and can be used as polished optical elements, thin and thick films, and optical fibers. Alfa Chemistry can custom manufacture optical components of almost any shape and size according to customer requirements using GLS materials. Contact us if you require assistance.
Advantages and Uses of Gallium Lanthanum Sulphide Materials
For optoelectronic applications, GLS crystal materials are thermally stable up to 550 ℃ and optically clear from visible to infrared wavelengths. In terms of optics, GLS has a high refractive index, a transmission window that extends to roughly 10 µm and covers the majority of visible wavelengths, as well as a low maximal leptonic energy of 450 cm-1.
Fig 1. Optical transmission of GLS glass measured in region of (a) electronic absorption edge, (b) loss minimum and (c) infrared (multiphonon) absorption edge. (Bastock P, et al. 2015)
Advantages and Uses of Gallium Arsenide Materials
Thermally, because GLS glass has a low heat conductivity and a strong temperature dependence in terms of its refractive index, it exhibits substantial thermal lensing effects. The high glass transition temperature of GLS, however, makes it resistant to heat deterioration and possesses strong chemical endurance. Additionally, its vitreous nature is non-toxic, unlike many sulfides based on arsenic. Its high lanthanum content provides good rare earth solubility and ion dispersion in the glass matrix of the active device, giving it a unique edge over other sulfides.
GLS can be present in both the glass and crystalline phases. It is a semiconductor in the glass phase with a band gap of 2.6 eV, and a wavelength of 475 nm. GLS glasses consequently appear dark orange. Additionally, GLS may be produced and processed on a larger scale without the need for sealed ampoule processing, which makes it safer and more affordable. Additionally crucial, impurity levels have greatly decreased, leading to better performance, particularly in the OH- and SH- absorption bands about 3 and 4 µm.
Fig 2. GLS glass discs polished for optical characterization. (Bastock P, et al. 2015)
Properties of Gallium Lanthanum Sulphide Materials
| Density | 4.04 g/cc |
| Molecular Weight | 276.9 |
| Solubility | Negligible in water |
| Class/Structure | Amorphous glass |
| Melting Point | 830 °C |
| Hardness | Knoop 206 with 200g indenter |
| Refractive Index | 2.398 at 1.014 μm |
| Transmission Range | 0.5 to 10 μm |
| Reflection Loss | 29% at 1.014 μm |
| Absorption Coefficient | <0.005 cm-1 |
| dn/dT | +75x10-6 /°C |
| Youngs Modulus (E) | 59 GPa |
| Shear Modulus (G) | 23 GPa |
| Bulk Modulus (K) | 24.5 GPa |
| Thermal Expansion | 10x10-6 /°C at 273K |
| Thermal Conductivity | 0.43 W/m/K at 273K |
| Dielectric Constant | 8.1 at 1KHz |
| Specific Heat Capacity | 0.54 J g-1 K-1 |
| Poisson Ratio | 0.24 |
About refractive index parameters.
"No" means ordinary light.
| µm | No | µm | No | µm | No |
|---|---|---|---|---|---|
| 0.546 | 2.522 | 0.579 | 2.500 | 0.644 | 2.467 |
| 0.668 | 2.458 | 0.707 | 2.466 | 1.014 | 2.398 |
| 1.367 | 2.379 | 1.710 | 2.371 |
Reference
- Bastock P, et al. (2015). "Properties of Gallium Lanthanum Sulphide Glass." in CLEO: 2015, OSA Technical Digest (online) (Optica Publishing Group, 2015). paper STh1G.1.