Tissue Imaging Technique Using Near-Infrared Illumination of Whispering Gallery Mode Silicon-Based Resonator

This letter introduces a novel technique for achieving high-precision 2-D tissue imaging by exploiting the sensitivity of a whispering gallery mode (WGM) silicon resonator’s conductivity to near-infrared (NIR) illumination. The WGM silicon resonator, in conjunction with a microstrip line, acts as the primary sensing element. To ensure precise imaging, the tissue under test (TUT) specimen is meticulously positioned on the resonator at a specific distance and manipulated using a 2-D scanner with 3-mm steps. By directing NIR light emitted from a light-emitting diode (LED) through the scanning TUT sample onto the WGM resonator, variations in the silicon resonator’s conductivity are harnessed, resulting in changes in the magnitude of the transmission coefficient (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula>). The alteration in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> during scanning is contingent upon the absorption of NIR through TUT. As the TUT undergoes scanning, the measured transmission coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> parameters are transformed into a 2-D image map. This method effectively discriminates between fat and muscle tissues, underscoring the feasibility and practicality of this approach. Importantly, the proposed methodology shows promise for detecting various biosensors and holds potential applications in breast cancer detection.