Differentiation of biological tissue based on angle-resolved scattering distribution using fiber-coupled single-mode light source with spectrally controllable emission characteristics

In today's world, more and more emphasis is placed on non-invasive, label-free diagnostic types in order to avoid the destruction of tissue structures. One example is Flow cytometry, which allows the differentiation of single cells. In order to realize a spectrally and angularly resolved scattered light measurement setup, which allows both the differentiation of cell clusters and provides information about the cell state, a special multispectral light source in the visible/near infrared wavelength range was developed. For this purpose, single-mode fiber-coupled laser diodes of defined wavelengths are coupled into a polarization-maintaining fiber using a developed wavelength-selective coupler and an optical switch. The desired polarization is set by a polarization-maintaining fiber using paddles. A developed electronical circuit with integrated temperature control enables the selection of the wavelengths as well as the control of the laser diodes. In addition to that, the light source achieves the required modulated operation in the nanosecond range to generate short pulses of 600 ns with a peak pulse power of about 3 mW for time-resolved data acquisition. The fiber-based system can be flexibly integrated into a scattered light measurement setup, and principal component analysis was used to differentiate between the tissues of pig heart, pig liver, pig stomach, and sheep tendon based on the scattered light.