Tellurite Glass and Its Application in Lasers

*Pengfei Wang, Shijie Jia, Xiaosong Lu, Yuxuan Jiang, Jibo Yu, Xin Wang, Shunbin Wang and Elfed Lewis*

## **Abstract**

This chapter provides expert coverage of the physical properties of new noncrystalline solids—tellurite glass and the latest laser applications of the material—offering insights into innovative applications for laser and sensing devices, among others. In particular, there is a focus on specialty optical fibers, supercontinuum generation and laser devices, and luminescence properties for laser applications. This chapter also addresses the fabrication and optical properties and uses of tellurite glasses in optical fibers and optical microcavities, the significance of from near infrared (NIR) to mid-infrared (MIR) emissions and the development of tellurite glass-based microcavity lasers. The important attributes of these tellurite glasses and their applications in lasers were discussed in this chapter.

**Keywords:** tellurite glass, fiber lasers, supercontinuum sources, specialty fibers, microcavity lasers

#### **1. Introduction of tellurite glass**

Tellurite glasses are noncrystalline solids with many applications in photonics, appear in a wide range of compositions, and can be operated over a large temperature range [1–4]. Tellurite glasses have been studied for more than 150 years [5], but more recent versions have been produced with purities exceeding 98.5% [6]. They are characterized by a low melting point and the absence of hygroscopic properties, and hence tellurite glasses have limited the application of phosphate and borate glasses and aroused widespread interest in the field of photonics and associated technologies. Moreover, they have high density and a low transition temperature [7, 8]. Their optical properties include relatively high refractive index, high nonlinear refractive index, high dielectric constant, as well as good chemical stability and a wide infrared (IR) transmission range (1–6 μm) [9–11].

In 1952, Stanworth [1] conducted preliminary research on the formation and structure of tellurite glass. The main raw material is TeO2 and at that time this was relatively expensive, and hence tellurite glass was considered to be of low practical value and had not been further studied. Since the late 1980s to the mid of 1990s [12, 13], considerable progress had been made in the advancement and understanding of the optical and physical properties of new tellurite glasses, including their molecular structure and bonding properties.

Research in tellurite glass-based broadband fiber amplifiers was initially concentrated around erbium-doped tellurite fibers. This was primarily due to its relatively broadband gain spectrum, which led to it attracting a great deal of research attention which has persisted up to the present. Currently, many worldclass university-based research institutions and industrial companies have investigated the potential of tellurite glass for use in fibers, and this has resulted in rapid progress. In this section, the composition, structure, and thermal stability of tellurite glasses will be considered.
