Devices based on surface plasmon interference filters

• US 6,297,907 B1
• Filed: 08/31/1998
• Issued: 10/02/2001
• Est. Priority Date: 09/02/1997
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Wang, Yu
• Primary Examiner(s): Chang, Audrey
• Assistant Examiner(s): Curtis, Craig
• Application Number:
  US09/144,519
• Time in Patent Office: 1,128 Days
• Field of Search: 345/88, 348/744, 349/105, 349/106, 349/196, 359/585, 359/578, 359/579
• US Class Current: 359/585
• CPC Class Codes: G02B 27/288 Filters employing polarising elements, e.g. Lyot or Solc filters G02B5/3016 takes precedence
• CPC Class Codes: G02F 1/195 by using frustrated reflection digital reflection using controlled total internal reflection G02F1/315
• CPC Class Codes: G02F 2203/10 plasmon

Abstract

Devices based on surface plasmon filters having at least one metal-dielectric interface to support surface plasmon waves. A multi-layer-coupled surface plasmon notch filter is provided to have more than two symmetric metal-dielectric interfaces coupled with one another to produce a transmission spectral window with desired spectral profile and bandwidth. Such notch filters can form various color filtering devices for color flat panel displays.

Claims

1. An optical device, comprising:

a first array of prisms formed of a transparent material, each prism having at least a first prism facet and a second prism facet intersecting said first prism facet at a prism apex;

at least one metal layer and an electro-optical dielectric layer contacting each other to form a metal-dielectric interface on each prism facet, wherein said dielectric layer has a refractive index less than a refractive index of said first and second arrays of prisms, and wherein said metal-dielectric interface generates a surface plasmon wave in response to a p-polarized input light beam to transmit light at a selected wavelength within a bandwidth according to a control voltage from said metal layer to said dielectric layer and reflects light of other wavelengths; and

a second array of prisms substantially identical to said first array, disposed to engage to said first array in such a way that each prism facet in said second array conformably contacts said metal-dielectric interface formed on a respective prism facet of said first array, wherein said second array couples an input light beam to said metal-dielectric interface and the said first and second arrays are configured so that said input light beam is respectively reflected once by metal-dielectric interfaces on two adjacent prism facets of said first array to produce a desired color and a desired grey scale.

2. The device as in claim 1, further comprising a polarization layer disposed relative to said second array.

3. The device as in claim 2, further comprising a lens array disposed between said polarization layer and said second array, wherein each lens in said lens array is positioned over two adjacent prism facets of two different prisms in said first array.

4. A device, comprising,

a first tunable optical filter disposed to receive an input light beam to produce a first reflected beam and configured to include at least one metal layer and one electro-optical dielectric layer which form a metal-dielectric interface to generate a surface plasmon wave in response to a p-polarized input beam to transmit light at a first selected wavelength within a first bandwidth according to a first control voltage and to reflect light at other wavelengths;

a second tunable optical filter disposed relative to said first tunable optical filter to receive said first reflected light beam, said second tunable optical filter having at least one metal layer and one electro-optical dielectric layer to form a metal-dielectric interface that generates a surface plasmon wave in response to a p-polarized input beam to transmit light at a second selected wavelength within a second bandwidth according to a second control voltage and to reflect light at other wavelengths,

wherein said second optical filter reflects said first reflected light beam to produce a second reflected light beam with a selected color different than a color of said input light beam, and

wherein each of said first and second tunable optical filters comprises;

a first coupling element having a first coupling surface and operable to couple a p-polarized input electromagnetic wave to have a propagation component parallel to said first coupling surface;

a first metallic film formed on said first coupling surface and operable to produce free electron oscillations in response to excitation of said p-polarized input electromagnetic wave, wherein said first metallic film is configured to allow penetration of evanescent fields;

a first dielectric layer having a first surface in direct contact with said first metallic film to form a first metal-dielectric interface and a second surface opposing said first surface;

a second metallic film substantially identical to said first metallic film and formed on said second surface of said first dielectric layer to form a second metal-dielectric interface that is substantially symmetric to said first metal-dielectric interface with respect to said first dielectric layer;

a second dielectric layer having a first surface in direct contact with said second metallic film to form a third metal-dielectric interface and a second surface opposing said first surface;

a third metallic film substantially identical to said second and first metallic films and formed on said second surface of said second dielectric layer to form a fourth metal-dielectric interface that is substantially symmetric to said third metal-dielectric interface with respect to said second dielectric layer; and

a second light coupling element configured to have a second coupling surface which is in direct contact with said third metallic film and operable to couple an electromagnetic wave propagating in said third metallic film along said second coupling surface into an output electromagnetic wave,

wherein said first, second, third, and fourth metal-dielectric interfaces are operable to support surface plasmon waves and to transfer energy of a selected spectral component in said p-polarized input electromagnetic wave from said first coupling surface to said second coupling surface by coupling a selected surface plasmon mode on said first metal-dielectric interface to said fourth metal-dielectric interface.

5. The device as in claim 4, wherein said first and second dielectric layers are formed of an electro-optic material and said first and third metallic films are applied with different voltages to change an optical thickness of said dielectric layers to tune a center wavelength of said selected spectral component.

6. The device as in claim 4, wherein said first and second dielectric layers have a thickness on the order of about one wavelength of said input electromagnetic wave.

7. The device as in claim 4, wherein said first and second coupling elements comprise prisms which are made of a dielectric material having a dielectric constant higher than a dielectric constant of said first and second dielectric layers.

8. The device as in claim 4, further comprising a spatial light modulator positioned to receive said second reflected beam from said second optical filter, said spatial light modulator having an array of light-modulating pixels to modulate said second reflected beam to produce an image.

9. The device as in claim 8, wherein said spatial light modulator includes a liquid crystal panel.

10. The device as in claim 4, further comprising an optical integrator positioned in an optical path of said input light beam to increase uniformity of a spatial intensity distribution of said input light beam.