FINITE DIFFERENCE TIME DOMAIN SIMULATIONS OF HYBRID NEUROTRANSDUCERS BASED OPTICAL MICROLASERS

摘要

Different pathologies such as Alzheimer's, Parkinson's, Wilson's diseases, and chronic traumatic encephalopathy due to blasts and impacts affect the brain functions altering the neuronal electrical activity. An important aspect of the brain study is the use of non-invasive, non-surgical methodologies that are suitable to the well-being of the patients. Only a portion of the electromagnetic field can be detected by applying sensors outside the scalp; in addition, surgery is often involved if sensors are applied in the subcutaneous region of the skull. Optical techniques applied to biomedical research and diagnostics have been spread during the last decades. For example, near infrared light (NIR) of spectral range goes from 800 nm to 1300 nm, it is harmless radiation for the living tissue, and can penetrate the living matter in depth as, it turns out that most of the living matter is transparent to the NIR light. Optical microlasers have been recently proposed as neurotransducers for minimally invasive neuron activity detection for the next generation of brain-computer interface (BCI) systems. They are lightweight, require low power consumption and exhibit low latency. This novel sensor that can be made of biocompatible material is coupled with a voltage sensitive dye; the fluorescence of the dye, which is excited by an external light source, is used to generate optical (laser) modes. Any variation in the neurons' membrane electric potential via evanescent field's perturbation turn affect the shifting of these laser modes. In order to reduce the energy required to power these devices and to improve their optical emission, metal nanoparticles can be coupled in order to use their plasmonic effect. In this paper, finite-difference time-domain (FDTD) numerical technique is used to analyze the performances on a dye-doped microlaser. Purcell effect and resonant wavelengths are observed.