The spectroscopic and energy transfer characteristics of the rare earth ions used for silicate glass fibre lasers operating in the shortwave infrared

The continuing growth in the research and development of high power diode-pumped fibre lasers relates to the exceptional thermal management provided by the extended geometry of the fibre and the small quantum defect associated with the 1 μm emitting Yb³⁺ ion. Lengthening the emission wavelength of diode-pumped fibre lasers further into the infrared is important for many applications ranging from medicine to defence; however, extending the emission wavelength remains a challenge. This review will examine in detail the spectroscopy and the energy transfer processes that impact Tm³⁺-doped and Ho³⁺-doped silicate glasses that are used for fibre lasers in the 1.9 μm to 2.1μm region of the shortwave infrared spectrum. We will explore a number of important applications that function in the shortwave infrared region that will benefit from using these light sources and I will suggest the reasons for choosing silicate glass over other glasses as the host material for this wavelength range. A Tm³⁺-doped aluminosilicate glass in a glass-working lathe in the process of being collapsed into a preform ready for drawing into double clad optical fibre. The red glow that can be observed in the centre of the preform is the thermoluminescence from the Tm³⁺ ions being heated to approximately 2000 °C.