How Bragg reflectors work: Bragg reflectors comprise of alternating layers of high (nH) and low (nL) refractive index materials of thickness tH and tL respectively. Light reflected at each interface interacts, and undergoes cons constructive and destructive interference, resulting in light of certain colour to be reflected. The wavelength of light that is reflected back (λ0) and bandwidth (Δλ) of reflectivity peak is given by the equations below. Bragg reflectors that reflect light in the visible region have 100 nm thick layers.
Sensing principle: The analytes may change the optical thickness of alternating layers of high and low refractive index materials, resulting in the peak wavelength to change. This change in peak wavelength in response to analytes forms the basis of sensing by Bragg reflectors.
We are currently working to fabricate Bragg reflector sensors using two different approaches. Stay tuned for more information.