ABSTRACT
We report the fabrication of a novel fiber-optic sensor device, based on the use of a microsphere conformally coated with a thin layer of zinc oxide (ZnO) by atomic layer deposition (ALD), and its use as a refractive index sensor. The microsphere was prepared on the tip of a single-mode optical fiber, on which a conformal ZnO thin film of 200 nm was deposited using an ALD process based on diethyl zinc (DEZ) and water at 100 °C. The modified fiber-optic microsphere was examined using scanning electron microscopy and Raman spectroscopy. Theoretical modeling has been carried out to assess the structure performance, and the performed experimental measurements carried out confirmed the enhanced sensing abilities when the microsphere was coated with a ZnO layer. The fabricated refractive index sensor was operating in a reflective mode of a Fabryâ»Pérot configuration, using a low coherent measurement system. The application of the ALD ZnO coating enabled for a better measurement of the refractive index of samples in the range of the refractive index allowed by the optical fiber. The proof-of-concept results presented in this work open prospects for the sensing community and will promote the use of fiber-optic sensing technologies.
ABSTRACT
This manuscript presents a theoretical analysis of a diamond-based integrated optics structure for applications in biosensors. The geometrical, optical, and sensitivity properties of an integrated optical structure were theoretically analyzed and optimized for biosensor applications. The analysis focused on determining the waveguide properties, including the effective refractive index Neff as a function of refractive index nw and thickness dw of waveguide layer, refractive index of the hemoglobin cover layer ncH and substrate layer ns, homogeneous sensitivity dNeff/dncH, and modal field distribution of guided waveguide modes. The analysis was completed for two types of waveguide layer materials: undoped or boron-doped diamond films with or without the hemoglobin cover layer. The presented experimental results form a base for developing biosensor structures based on integrated optics for determining the properties of hemoglobin.
ABSTRACT
In this work we present the fabrication and characterization of a diamond film which can be utilized in the construction of optical sensors for the investigation of biological samples. We produced a nitrogen-doped diamond (NDD) film using a microwave plasma enhanced chemical vapor deposition (MWPECVD) system. The NDD film was investigated with the use of scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. The NDD film was used in the construction of the fiber optic sensor. This sensor is based on the Fabry-Pérot interferometer working in a reflective mode and the NDD film is utilized as a reflective layer of this interferometer. Application of the NDD film allowed us to obtain the sensor of hemoglobin concentration with linear work characteristics with a correlation coefficient (R²) equal to 0.988.
