Third-order nonlinear optical properties of mono and biphasic β-tricalcium phosphate in continuous wave regime

β-Tricalcium phosphate (β-TCP) powders were prepared using wet chemical method and the powders are heat-treated at different temperatures (800 to 1300 °C). The quantitative Rietveld refinement analysis reveals ~ 99% of mono β-TCP phase in the sample heat-treated at 1200 °C and sample heat-treated at 1300 °C contains ~ 93.4% of β-TCP phase and ~ 6.0% of α-TCP. The vibrational modes of PO₄³⁻ groups namely ν₁, ν₂, ν₃ and ν₄ were characterized using FTIR and laser Raman studies. SEM analysis illustrates that the particle sizes are in the micrometer range and the samples are crystalline in nature. SEM studies also highlights the presence of additional smaller granules of α-TCP over the large crystallites of β-TCP for the sample heat-treated at 1300 °C. In the photoluminescence spectra, multiple emission bands are observed in the region between 340 and 540 nm and are attributed to the non-radiative recombination processes due to thermal effects. The optical nonlinear absorption coefficient and optical nonlinear refractive index of the β-TCP samples were examined using the Z-scan technique. A peak nonlinear refractive index and nonlinear absorption coefficient values of 10⁻⁴ cm²/W and 10⁻¹ cm/W, respectively, were observed from the Z-scan studies. The self-defocusing effect has been observed in the present samples under continuous wave illumination which can be useful to identify their candidature in optical limiting applications.