| 摘要 |
A filter and fabrication process for a thin film filter that is based on frustrated total internal reflection and multiple waveguide layers, in which the waveguide modes are resonantly coupled. The physics of the design is related to prism coupling of light into planar waveguides, and waveguide coupling between planar waveguides in close proximity. Embodiments include a filter that acts as a bandpass filter and polarizer, a filter that acts as a bandpass filter, polarizer and angle filter (spatial filter), a filter that is widely tunable, and a filter that is widely tunable in both peak transmission wavelength and width. Methods of fabrication are disclosed, and methods to correct for manufacturing errors in thin film deposition are described. The filter embodiments can also be used in reflection as notch filters in wavelength and angle, for a particular polarization component. |
| 主权项 |
1. A filter comprising:
an input element that is at least partially transparent to electromagnetic radiation with a wavelength at least within a first wavelength band and a direction within a first angular band, and has properties including a first refractive index; an output element that is at least partially transparent to electromagnetic radiation with a wavelength at least within the first wavelength band and a direction within the first angular band, and has properties including a second refractive index; and a thin film structure comprising a series of optically-coupled waveguide structures between the input element and the output element, the series of optically-coupled waveguide structures comprising at least a first planar waveguide structure in optical contact with the input element and a second planar waveguide structure in optical contact with the output element, each waveguide structure of the series of optically-coupled waveguide structures supporting at least a first waveguide mode and being a leaky waveguide comprising a core and cladding, wherein the first refractive index, the second refractive index, and the properties of each waveguide structure of the series of optically-coupled waveguide structures are selected to permit excitation of a resonant mode in the thin film structure, the resonant mode having an effective dispersion, by evanescent coupling of a selected polarization component of electromagnetic radiation of an angle within a second angular band that is within the first angular band and of a wavelength within a second wavelength band that is within the first wavelength band, thereby causing, in operation, transmission of the selected polarization component of electromagnetic radiation through the thin film structure without reflection of the selected polarization component of electromagnetic radiation from the thin film structure, the second wavelength band having parameters including a wavelength width and a peak transmission wavelength, and the second angular band having an angular width and a direction of maximum transmission, and wherein each optically-coupled waveguide structure of the series of optically-coupled waveguide structures comprises a first planar cladding layer, a second planar cladding layer, and a planar waveguide layer, and at least one of the first planar cladding layer, the second planar cladding layer, and the planar waveguide layer has a spatially varying thickness perpendicular to the plane of the respective first planar cladding layer, second planar cladding layer, or planar waveguide layer, whereby in operation of the filter the peak transmission wavelength of the second wavelength band varies spatially. |
