Designing multilayer dielectric filter based on TiO2/SiO2 for fluorescence microscopy applications

Hanh Hong Mai

doi:10.18287/2412-6179-co-618

Abstract

This study presents a new construction design of a distributed Bragg reflector (DBR) filter and a Fabry–Pérot (FP) filter by using needle technique as a synthesis method. The optimized DBR and FP filters having a proper number of layers with controlling thickness TiO2/SiO2 are utilized to transmit only a certain narrow band of wavelengths while blocking the others. As a proof of concept, the filters are designed to selectively transmit only a very narrow band of wavelength at 780 nm which is the near infrared (NIR) fluorescent emission from Alexa Fluor 750 dye. The obtained results show that the optimized filters represent advanced spectral performance which can be used to improve the sensitivity and the imaging contrast in fluorescence microscopy.

Highlights

Fluorescent dyes are frequently used as cell and tissue labels in fluorescence microscopy and cell biology [1 – 3]
After conjugating onto biological specimens, they can emit a wide range of wavelength spanning from visible (VIS) to near infrared (NIR) under a continuous illumination of a light source, generates images [5 – 8]
The images obtained from specimens conjugated with NIR dyes are normally dimmer with lower imaging contrast compared to specimens conjugated with VIS dyes

Summary

Introduction

Fluorescent dyes are frequently used as cell and tissue labels in fluorescence microscopy and cell biology [1 – 3]. Speaking, the image contrast can be improved by allowing only NIR emission to reach to the detector while blocking other emissions This can be done in a fluorescence microscope by implementing band-pass filters which allow only NIR light to transmit while filtering out others. Band-pass filters based on thin film technology has been attracted a lot of attention in microscopy imaging [9 – 11] They consist of alternating layers of high and low refractive index materials with particular thicknesses. As a proof of concept, a combination of an optimized DBR and a FP filters was designed with a central wavelength of 780 nm to selectively transmit a narrow band of wavelength at 780 nm emitted from a NIR fluorescent Alexa Fluor 750 dye while blocking the others [3].

Theoretical basis

Optimization of multilayer filters

Optimization designs and discussion

Conclusion