Multiwavelength narrowband high-reflection filters with low-reflection sidebands.

We propose a novel method for the construction of multiwavelength narrowband high-reflection filters consisting of a reflection mirror, a middle structure, and an induced-reflection match stack (IRMS). The results show that the peak position of the proposed reflection filters is identical to that of the transmission filters consisting of the same middle structure and two flanking high-reflection dielectric film stacks. The range in which multiple reflection peaks occur is determined by the degree of overlapping of the forbidden band in the reflection mirror and the conducting band in the middle structure. This range can be extended by changing the dielectric coefficients of the dielectric film stack or by substituting the dielectric reflection mirror with a silver mirror.

Narrowband high-reflection filters with wide and low-reflection sidebands.

Narrowband high-reflection filters with the structure sub|H(LH)(m1)alpha L(HL)(m2)Cr(beta)M|air are proposed. The effects of the Cr layer and the matching stack consisting of dielectric multilayer on the reflection characteristics of the filters are analyzed. The distribution of the internal electric field and the optical absorption is also calculated. The analysis indicates that the improvement of the sidebands could be reached by applying the matching stack without impairing the maximal reflectance and half-width of the reflection band. Wide and flat reflection sidebands could be realized by applying a relatively thicker metal layer. However, lowering the sideband reflection could only be achieved by adding appropriate matching stacks. Large m(1)-m(2) could increase the maximal reflectance, while large m(2) or n(H)/n(L) would reduce the width of the reflection band. In the Cr layer, the least average intense electric field occurred at the central wavelength, the relatively high electric field intensity exists at the wavelengths outside the central wavelength region. The optical absorption of the filter depends strongly on the electric field intensity inside the Cr layer.

Two-chamber integrated multichannel narrowband filter prepared by a multistep etching method.

A new, to the best of our knowledge, method, which combines the multistep ion-etching method with a traditional narrowband filter coating technique, is developed to prepare a two-chamber integrated multichannel filter. The influence of film deposition and etch technique on the shape and height of the narrow transmittance peaks is analyzed. A 32-channel narrowband integrated filter is fabricated with a homemade ion-etching machine and a coating machine. Every channel is distinctly separated and the FWHM is 1% of its central wavelength. The feasibility of the technique will be useful in the fabrication of a higher integrated multichannel narrowband filter.