Cepstral Analysis of Photonic Nanojet-Illuminated Biological Cells

─ It is currently believed that nanometerscale internal refractive index fluctuations within biological cells change significantly during the initial stages of ultra early-stage cancer development well in advance of these changes becoming more pronounced and histologically detectable. Here, backscattered cepstral results of photonic nanojet-illuminated cells are investigated as a means to offer unique advantages for determining the internal structure and composition of cells at sub-diffraction (nanometer) scales. Specifically, the finite-difference time-domain (FDTD) method is employed to obtain the backscattered cepstrum of photonic-nanojet illuminated human colorectal HT-29 cells. Analysis of the backscattered cepstrum of the HT29 cells indicates a clear means to distinguish between cells having larger and smaller levels of internal refractive index fluctuations before these changes are histologically detectable. Further, we find that the surface reflection is reduced for the case of nanojet-illuminated cells compared to flat surfaces. Index Terms ─ Biological media, cancer, cepstrum, FDTD, photonic nanojet.