Modeling of light transmission in multilayer epitaxial AlN/GaN structures for biomedical pyrosensors

Abstract

The spectral-pulse diversity of modern lasers currently used for subcutaneous surgeries provides ample opportunities for the realization of rather complex modes of radiation exposure and allows the simultaneous performance of diagnostic, therapeutic and surgical procedures; this in turn leads to an urgent need for appropriate spectrally indifferent sensors oriented for in vivo operation. In the present work, we propose the use of weakly absorbing epitaxial GaN/AlN/GaN structures as a basis for the fabrication of pass-through pyrometric sensors embedded in a subcutaneous light guide. The use of such sensors in vivo will allow the local study of the absorption or scattering of intracavitary tissues in a wide spectral range, as well as the real-time control of the pulse structure of the laser beam. For such structures, a mathematical model of light propagation taking into account absorption and heat generation was constructed and a computational algorithm for obtaining post-pulse temperature distributions and for calculating the pyrocoefficient at different values of thickness and donor concentration of absorbing GaN layers was developed in the MATLAB environment. A criterion for the efficiency of the sensor performance was proposed, based on which the optimal ratios between the thickness values of AlN and GaN layers for different values of the absorption coefficient αGaN were obtained. Key words: subcutaneous operations, laser therapy, laser surgery, pyroeffect, pyrosensors, aluminum nitride, epitaxial technologies, multilayer GaN/AlN structures.