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Supercontinuum-based nondisruptive scattering analyses of mouse fibroblast L929 cells before and after necrosis," J.Abstract. The scattering properties of biological tissue are highly dependent on the structure size, refractive index, and wavelength of the incident light. Furthermore, these scattering characteristics are strongly influenced by movements of the scattering objects. A method is developed to determine the angular-and spectral-resolved scattering properties that enabled the characterization of biological nano-and microscaled cell structures. Nanosecond pulses from a spectrally filtered supercontinuum light source are captured and time-resolved to depress background noise and minimize disruptive effects of the biological cells. The scattering characteristics of a monolayer of mouse fibroblast L929 cells are measured at defined wavelengths in a standard cell culture plate. Because of the size and distribution of the scattering structures, a Fourier transform-based Mie scattering scheme is used to analyze the data. The system is tested to detect structural changes of mouse fibroblast L929 cells before and after poisoning with Triton X100. The final result is the development of a contamination-free method to study pathological changes in cell cultures, necrosis, or other cell-damaging effects.

Low-coherence-interferometry (LCI) is a powerful and widely used measurement approach in the fields of biomedicine, surface analysis, and imaging. Many techniques, such as optical coherence tomography (OCT) or Dispersion-Encoded-LCI (DE-LCI) derive from LCI. This work focuses on the DE-LCI measurement approach for profilometry. An estimation of axial displacement in the measuring arm of extremely low resolved DE-LCI spectrograms was achieved by instrumentalizing an artificial intelligence (AI) based analysis t echnique. It was proven effective even for spectrograms that partially fall below the Nyquist criterion. The presented estimation strategy considers the very low-resolution distorted data to be some kind of "fingerprint" o f t he c omplete i nitial s ignal, which cannot be interpreted directly by classic deterministic models. It was shown, that this resolution limitation could be exceeded for certain boundary conditions with the introduced artificial neural network t opology. The benefits of the proposed AI-Model are demonstrated in a series of reference measurements of the surface topography of an uncoated Si-reference object. The spectral resolution was varied throughout the process. The relation between the absolute axial resolution and full measurement range was used to evaluate the final m easurement dynamic. Resistance to noise and mechanical displacement, especially the displacement of the reference and the typical detector noise is presented and discussed for the proposed estimation approach. The described novel method allows overcoming central instrumental limitations, namely the spectral resolution of the used instrument, while increasing measurement dynamics significantly. T his i s c rucial f or D E-LCI s ensors a pplications a s w ell a s for in-line and high-speed DE-LCI metrology purposes.

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.

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