Optical bandpass filter
AssigneeThe Governors of the University of Alberta
InventorRay DeCorby
Life of this patent
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Abstract
A tunable resonant tunneling gap for resonant tunneling across the tunneling gap. By adjusting the width of the tunneling gap and adjusting an angle of incidence of light onto the tunneling gap, a pass-band shape and center wavelength may be tuned. The tunneling gap may be an air gap between lenses coated with matching Bragg reflectors. The air gap may be adjusted for example using piezo actuators connecting between the lenses. The angle of incidence may be adjusted for example by rotating the lenses, and thus the tunneling gap, relative to an incident beam of light.
Claims14
A method for tuning a resonant tunneling optical filter operating in a frustrated total internal reflection regime, the method comprising:
- providing a resonant tunneling optical filter comprising two hemi-cylindrical or hemi-spherical coupling prisms each having a flat surface coated with a uniform thin film stack specified to enable admittance-matched resonant tunnelling of a selected linear polarization state and wavelength of incident light while reflecting an orthogonal linear polarization of incident light over a wavelength range of interest, the coupling prims having their coated surfaces separated by a tunneling gap of adjustable width and having gap interfaces subject to total internal reflection, the resonant tunneling being mediated by surface states at the interfaces of the tunneling gap;
- adjusting an angle of incidence of light onto the resonant tunneling optical filter to cause a variation in resonant energy and frequency of the surface states;
- adjusting a width of the tunneling gap of the resonant tunneling optical filter to cause a variation in mutual coupling between the surface states;
- and
- the angle of incidence and the width of the tunneling gap being adjusted in combination wherein the angle of incidence is selected to provide a desired center wavelength and the tunneling gap is selected to provide a desired shape of a passband of the resonant tunneling optical filter.
A resonant tunneling optical filter operating in a frustrated total internal reflection regime and comprising two hemi-cylindrical or hemi-spherical lenses as input/output coupling prisms, each lens having a respective flat face facing the flat face of the other lens, in which the respective flat faces are each coated with respective thin film stacks, the flat faces being separated in use by an air gap with interfaces subject to total internal reflection, the thin film stacks arranged to provide resonant tunneling across the air gap, the resonant tunneling being mediated by surface states at the interfaces of the air gap, and the air gap being adjustable in thickness, in which adjusting the thickness of the air gap causes a variation in mutual coupling between the surface states, and a center wavelength and shape of a resonant tunneling passband being adjustable by combined adjustments of the air gap thickness and the angular orientation of the air gap relative to a collimated light beam inside the coupling prisms;
- wherein adjusting the angular orientation of the air gap relative to the collimated light beam causes a variation in resonant energy and frequency of the surface states.
Dependencies are inferred from the claim text.