Abstract
Photonic crystal slab sensors are extensively researched for label-free detection due to their sensitivity to changes in the refractive index of surrounding media. However, their application in imaging and endoscopy remains relatively underexplored. This thesis introduces a novel approach to endoscopic technology by designing a photonic crystal slab-based spectral sensor that can be incorporated at the tip of an endoscopic probe. The system incorporates hyperspectral imaging to analyze the optical properties of targeted biological or agricultural tissues in real time. In biomedical diagnostics, it can aid in the early detection of diseases, including the identification of cancer cells. In agriculture, it allows for non-invasive imaging of plant roots to identify plant disease conditions, root-microbial interactions, nutrient uptake, etc. What makes this sensor unique is its ability to capture the reflection spectrum from biological tissues and reconstruct it into detailed spectral mapping for further analysis. The photonic crystal slab itself is highly miniaturized—measuring 34 µm × 34 µm—making it compatible with navigating narrow human arteries such as terminal arterioles, which are as small as 50 µm in diameter. To enhance its sensing capability, the design employs a 3×3 matrix of photonic crystal slab arrays, each with precisely engineered geometrical parameters such as periodicity and structural dimensions. These parameters determine the distinct spectral response of each array. The reflection spectra collected from these arrays are processed through an image reconstruction algorithm to create detailed spectral maps. Simulations of the sensor in a gastrointestinal environment were conducted using COMSOL Multiphysics 5.6. Results revealed that cancer cells exhibit higher light absorption in the visible spectrum range (400 nm to 700 nm) than normal cells due to their higher refractive index, providing a basis for distinguishing between healthy and cancerous tissues. For agricultural applications, the photonic crystal-equipped endoscopic probe is capable of reaching root zones as narrow as 0.04 mm, enabling simultaneous collection of spectral and visual data from delicate plant root areas, which are difficult to reach otherwise. This capability supports early disease detection, stress assessment, and evaluation of nutrient uptake in plants. In conclusion, the integration of a photonic crystal slab-based spectral sensor into an endoscopic system marks a significant advancement for both biomedical diagnostics and precision agriculture. Future developments will focus on physical implementation of this technology for widespread use in clinical and agricultural applications.
Date of publication
Spring 5-3-2025
Document Type
Thesis
Language
english
Persistent identifier
http://hdl.handle.net/10950/4852
Committee members
Shawana Tabassum, Premananda Indic, Tahsin Khajah
Degree
Master of Science in Electrical Engineering
Recommended Citation
Sarker, Tasnim, "PHOTONIC CRYSTAL-BASED HYPERSPECTRAL IMAGING FOR IN VIVO SENSING AND ENDOSCOPY APPLICATIONS" (2025). Electrical Engineering Theses. Paper 67.
http://hdl.handle.net/10950/4852