Asymmetric one-dimensional photonic crystal for optical sensing in the visible spectral range

18th International Summer School on Vacuum, Electron and Ion Technologies

Lalova, A.^1 ; Todorov, R.^1

Acad. J. Malinowski Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 109, 1113 Sofia, Bulgaria^1

关键词: Concentration ranges;    High refractive index;    Layer by layer deposition;    Multi-layered structure;    One dimensional photonic crystal;    Photonic band-gap structures;    Two-layer structures;    Visible spectral range;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/514/1/012014/pdf
DOI  :  10.1088/1742-6596/514/1/012014

来源: IOP

【 摘 要 】

A gas sensor based on an asymmetric one-dimensional (1D) photonic band gap structure with one defect layer was designed and fabricated through layer-by-layer deposition of spin-coated poly methyl methacrylate (PMMA) and vacuum-deposited As2S3. Initially, the thickness variations, Δd, were determined of the thin films resulting from the poly methyl methacrylate exposure to chloroform vapor in the concentration range 100-9000 ppm. It was found that the value of Δd depends on the gas concentration and the exposure time. A two-layer structure was prepared consisting of PMMA and vacuum-deposited As2S3. Further, the permeability of thin As2S3films to chloroform vapors was investigated. The asymmetric photonic structure consisted of 11 alternating layers of As2S3and PMMA. The defect PMMA layer was located before the last high-refractive-index film of chalcogenide glass. The thickness of the defect layer of PMMA was pre-calculated so that the pass band be centered at the wavelength of 550 nm. An offset was observed of the position of the pass band to the larger wavelengths after exposure to chloroform vapor. The multilayered structure proposed is promising for optical sensor applications.