Application of the time-domain and frequency-domain radiative measurement signals in retrieving the spectral complex refractive index of microalgae

Time-domain (TD) and frequency-domain (FD) pulse lasers are employed as the measurement lasers to retrieve the spectral complex refractive indices of microalgae, respectively. The finite volume method and an improved quantum-behaved particle swarm optimization algorithm are employed as the direct and inverse problem algorithms. The sensitivity analyses of measurement signals with respect to spectral complex refractive index are studied firstly. Then, the spectral complex refractive indices of Chlamydomonas reinhardtii (C. reinhardtii CC125) are retrieved by TD and FD pulse lasers, respectively. Finally, fitness function values and radiative properties of C. reinhardtii CC125 calculated by retrieval results are also studied. Results show that TD sampling region ct ∈[L, L + ct_p] and dimensionless FD sampling region ω⌢^∗∈[5,10] are the effective sensitivity regions to improve the retrieval accuracy. The incident TD pulse laser can obtain more accurate results. Retrieval results of real part n show better accuracy and robustness than those of imaginary part k.