Investigation of PbSe Quantum Dot-Doped Glass Fibers with Broadband Mid-Infrared Emission

Objective Broadband tunable mid-infrared (MIR) light sources have attracted much attention in practical applications such as spectral sensors, medical treatment, and environmental monitoring. At present, MIR emission from luminescent glass is primarily achieved through rare-earth ion doping. Its adjustable range, however, is relatively limited. As PbSe quantum dots (QDs) have a narrow band gap and a large Bohr radius, they are easily capable of achieving quantum confinement effect. PbSe QDs formed in germanate glass with low phonon energy can produce broadband tunable MIR emission spanning the wavelength range of 1. 8-2. 8 mu m. Using the melting-in-tube fiber drawing method, we successfully prepared all-solid-state PbSe QD-doped glass fiber and obtained broadband tunable emission covering 1.8-2.8 mu m. Therefore, PbSe QD-doped glass fiber is expected to be used for broadband tunable MIR light sources. Methods PbSe QD-doped germanate glass was prepared using the melting-quenching method and was selected as the core glass of glass fiber. The core glass and cladding glass were prepared into an optical fiber preform by cold working, which included rounding, perforating, polishing, and cleaning. Following that, the optical fiber preform was suspended in a resistance furnace and drawn into an optical fiber using the melting-in-tube method. The softening temperature of the cladding glass was 840 degrees C, according to the DSC curve. The PbSe QD-doped glass fiber was successfully drawn at 1000 degrees C after several attempts at various temperatures. At a heating rate of 6 degrees C min(-1), the resistance furnace was heated to 1000 degrees C. The cladding glass tube was then softened and the core glass was molten at this point. The precursor fiber was then quickly drawn without crystallization. Finally, the precursor fiber was heat treated to induce controllable precipitation of PbSe QDs in the glass fiber. Results and Discussions PbSe QD-doped glass was prepared by the melting-quenching method. The XRD spectra in Fig. 2 proved that PbSe QDs were precipitated in the heat-treated glass. Under 808 nm laser excitation, PbSe QD-doped glass could achieve broad MIR emission covering 1.8-2.8 mu m [Fig. 3( b)]. The melt-in-tube melting was used to successfully fabricate PbSe QD-doped glass fiber without crystallization. We observed from the EPMA test in Fig. 4 that the optical fiber had a good core-cladding structure with no obvious elemental migration between the fiber core and cladding. TEM was used to examine the distribution and size of QDs in a heat-treated fiber at 440 t. PbSe QD-glass fibers under different heat treatment schedules exhibited intense tunable MIR emission covering 1. 8-2.8 ttm when excited using an 808 nm laser (Fig. 7). Different heat treatments can be used to adjust the position of the emission peak. Finally, the PbSe QD-doped glass fiber had an optical loss of 17.19 dBm/m (Fig. 8). Conclusions This study presented the preparation and characterization of an all-solid-state PbSe QD-doped glass fiber with tunable broadband MIR emission. Based on the selection and optimization of the basic glass system, a size-controllable PbSe QD-doped glass was prepared and achieved broadband tunable emission in the MIR regions of 1.82.8 ttm. The core glass was a PbSe QD-doped borosilicate glass, and the cladding glass was a PbSe QD-doped borosilicate glass. The PbSe QD-doped glass fiber was successfully prepared using the melt-in-tube melting, and it was then characterized using EPMA. There was no evidence of elemental migration in the glass fibers, which had a complete core-cladding structure. When excited by an 808 nm laser, PbSe QD-doped glass fibers produced broadband tunable emission within 1.8-2.8 mu m, which was expected to be used as a broadband tunable MIR light source. Key words fiber optics; PbSe quantum dos; glass fiber; mid-infrared broadband emission; melt-in-tube melting