Influence of the Nd3+ Dopant Content in Bi3TeBO9 Powders on Their Optical Nonlinearity

Second harmonic generation measurements for neodymium-doped bismuth–tellurium borate (Bi3TeBO9:Nd3+) powders are shown for the first time. Using undoped and low-content Nd3+-doped samples associated with the strongest nonlinear optical response, studies of temperature-dependent second-harmonic generation near the absorption edge were conducted. Spectroscopic measurements of the investigated powders revealed characteristic Nd3+ absorption bands and helped to estimate the corresponding energy band gaps for the chosen samples. The influence of low Nd3+-content on the absorption edge shift, as well as on the enhancement of second-harmonic generation and its temperature attenuation, is discussed. Temperature-dependent X-ray diffraction measurements enabled researchers to calculate the thermal expansion coefficients for undoped and Nd3+-doped Bi3TeBO9 and to assess the impact of this phenomenon on its acentricity. Thermogravimetric studies demonstrated the absence of phase transitions for the chosen samples up to their incongruent melting points. Energy Dispersive X-ray Spectroscopy measurements verified the uniformity of Nd3+ distribution in doped Bi3TeBO9 powders. The suitability of polycrystalline Bi3TeBO9:Nd3+ as media for the self-frequency doubling devices for potential optoelectronic and biomedical applications was assessed. The finest fractions of deagglomerated and suspended powders were extracted and demonstrated near-nanostructural morphology of separated particles, as revealed by means of atomic force microscopy.