Real-time biosensor application of structurally chiral medium for detection and sensing of plasma in human blood

In this work, we theoretically investigated a unique and sensitive optical biosensor for detecting and sensing blood plasma using a structurally chiral medium. The proposed biosensor is a defective one-dimensional structure made from a structurally chiral material with 4 ¯ 2 m point group symmetry where the defect layer is considered as a channel for the blood plasma. The transmission and reflection of the structure are investigated utilizing the transfer matrix method for the circularly polarized waves. It is shown that a defect mode is created in the middle of the circular Bragg photonic band gap for the right-handed circularly polarized waves and experiences a red shift by increasing the blood plasma concentration. Also, it is observed that the sensitivity of the sensor can be increased by increasing the thickness of the defect layer. In addition, we reveal that the increase of the tilt angle of the structurally chiral medium results in the decrease of photonic band gap width and causes to blue-shift of the defect mode. As a result, the performance of the sensor decreases by increasing the tilt angle. The proposed structure has an easy and efficient manufacturing process, high stability and cost-effectiveness and can provide real-time blood plasma biosensors.