Researchers in Egypt, Kuwait, Saudi Arabia and India Simulate a Parity-Time Symmetric Terahertz Sensor for Frozen Oral Cancer Tissue: What the Scientific Reports Paper of 31 October 2026 Shows
What a simulated terahertz sensor for frozen oral cancer tissue shows, and what it has not yet tested
Quentir Medicine Monitor
Evidence-based insights for quantum medicine.
Three researchers working in Egypt, Kuwait, Saudi Arabia and India have designed, on a computer, a layered sensor meant to tell frozen oral cancer tissue from frozen healthy tissue with terahertz radiation. The device is a one-dimensional photonic crystal: thin alternating layers of silicon dioxide and porous silicon stacked on both sides of a central gap that would hold the tissue sample. Its distinctive feature is parity-time symmetry, a design rule taken from quantum mechanics in which layers that amplify light are balanced against layers that absorb it.
The paper, by Zaky A. Zaky of Beni-Suef University and the Gulf University for Science and Technology in Kuwait, Ali Hennache of Imam Mohammad Ibn Saud Islamic University in Riyadh and Abinash Panda of the CMR Institute of Technology in Bengaluru, appeared in the open-access journal Scientific Reports on 31 October 2026. Its headline figure is a transmittance-based sensitivity of 2.4 × 1011 percent per refractive index unit in the band between 0.9 and 1.1 terahertz. Every performance figure for the sensor comes from numerical simulation. No sensor was built for the study, and no new tissue was measured for it.
The authors' clinical target is oral cancer, and they cite more than 400,000 new oral cancer diagnoses a year and note that about 90 percent of oral cancers are squamous cell carcinomas. They list the drawbacks of diagnosis by visual inspection, palpation, vital staining and biopsy: results that vary with the clinician, pain, a risk of bleeding or infection, cost, waiting time and sampling error. The sensor in this paper would still examine excised tissue, so it would not remove the need to take a sample, and any gain in speed, cost or consistency remains untested.
The Scientific Reports article describes a stack of silicon dioxide and porous silicon bilayers repeated on each side of a defect layer 40 micrometers thick, all on a substrate. Without the defect, the stack blocks terahertz waves between about 0.58 and 0.72 terahertz. The defect opens a narrow transmission peak inside that blocked band, and the frequency and height of the peak depend on the refractive index of whatever fills the gap. Cancerous and healthy oral tissue bend and absorb terahertz waves differently, so the peak moves when one replaces the other. The authors computed this with the transfer matrix method, a standard calculation of how a wave passes through a stack of layers.
The tissue properties in the model come from a single earlier experiment. The authors fitted polynomial curves to the refractive index and absorption that Yookyeong Carolyn Sim, Joo-Hiuk Son and colleagues reported in Biomedical Optics Express in July 2013. That study imaged seven oral tissues resected from four patients between 0.2 and 1.2 terahertz, at minus 20 °C and at 20 °C, and compared the maps with histology. Freezing gave a larger spectral difference between oral cancer and normal mucosa than room temperature did, which is why the new design targets tissue held at minus 20 °C.
The authors also tuned the porosity of the porous silicon layers between 0 and 35 percent. Higher porosity raised the defect peak toward full transmission, while the peak broadened from about 0.003 to 0.005 terahertz at low porosity to 0.017 terahertz at 35 percent, and the frequency sensitivity fell from 0.028 terahertz per refractive index unit at zero porosity. Above 25 percent the blocked band began to leak and the peak became unstable. The authors chose 25 percent porosity as their balance of spectral resolution, transmission and sensing performance.