Optical multilayer structure, optical switching device, and image display

• US 6,940,631 B2
• Filed: 07/02/2001
• Issued: 09/06/2005
• Est. Priority Date: 07/03/2000
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ishikawa, Hiroichi
• Primary Examiner(s): THOMPSON, TIMOTHY J
• Application Number:
  US09/897,571
• Publication Number:
  US 20020070931A1
• Time in Patent Office: 1,527 Days
• Field of Search: 359/291, 359/290, 359/247, 359/318, 359/223, 359/224
• US Class Current: 359/291
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 5/284 of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates etalons for fibre optic multiplexing G02B6/29358; etalons for spectral measurement G01J3/26
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: G02B 5/286 having four or fewer layers, e.g. for achieving a colour effect
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3524 the optical element being refractive
• CPC Class Codes: G02B 6/3544 2D constellations, i.e. with switching elements and switched beams located in a plane
• CPC Class Codes: G02B 6/355 1x2 switch, i.e. one input and a selectable single output of two possible outputs
• CPC Class Codes: G02B 6/3572 Magnetic force magnetic forces controlling reflecting elements in general G02B26/085; magneto-optic devices G02F1/09
• CPC Class Codes: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: G02B 6/3594 Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams

Abstract

An optical multilayer structure has a substrate, a light-absorbing first layer in contact with the substrate, a gap portion having a changeable size capable of causing an optical interference phenomenon, and a second layer. By changing the size of the gap portion, an amount of reflection, transmission, or absorption of incident light can be changed. For example, the substrate is made of carbon (C), the first layer is made of tantalum (Ta), and the second layer is made of silicon nitride (Si₃N₄). Also in a visible light area, high response is realized. Consequently, the optical multilayer structure can be suitably used for an image display. The optical multilayer structure may be obtained by stacking, on a substrate made of a metal such as chromium (Cr), a first transparent layer made of a material having a high refractive index such as TiO₂ (n=2.40), a second transparent layer made of a material having a low refractive index such as MgF₂ (n=1.38), a gap portion having a changeable size capable of causing an optical interference phenomenon, and a third transparent layer made of a material having a high refractive index such as TiO₂.

Claims

1. An optical multilayer structure comprising:

a substrate;

a light-absorbing first layer;

a gap portion having a changeable size capable of causing an optical interference phenomenon; and

a second layer;

wherein when a complex index of refraction of the substrate is N_s (=n_s−

i·

k_s, where n_s denotes a refractive index, k_s denotes an extinction coefficient, and i represents an imaginary unit), a complex index of refraction of the first layer is N₁ (=n₁−

i·

k₁, where n₁ denotes a refractive index, and k₁ denotes an extinction coefficient), a refractive index of the second layer is n₂, and a refractive index of an incident medium is 1.0, the relation of the following Expression (1) is satisfied

{(n₁−

(n₂²+1)/2)²+k₁²−

((n₂²−

1)/2)²}{(n_s−

(n₂²+1)/2)²+k_s²−

((n₂²−

1)/2)²}<

0 

 

(1).

2. An optical multilayer structure according to claim 1, wherein the first layer, the gap portion, and the second layer are stacked in accordance with this order on the substrate.

3. An optical multilayer structure according to claim 1, wherein the second layer is made of a transparent material.

4. An optical multilayer structure according to claim 1, wherein the substrate is a light-absorbing substrate or a substrate on which a light absorbing film is formed.

5. An optical multilayer structure according to claim 1, wherein the substrate is made of a transparent material or a translucent material.

6. An optical multilayer structure according to claim 1, further comprising driving means for changing an optical size of the gap portion,

wherein the size of the gap portion is changed by the driving means, thereby changing an amount of reflection, transmission, or absorption of incident light.

7. An optical multilayer structure according to claim 6, wherein the optical size of the gap portion is changed by the driving means in a binary manner or continuously between an odd multiple of λ

/4 and an even multiple λ

/4 (including

     0), thereby changing the amount of reflection, transmission, or absorption of incident light in a binary manner or continuously.

8. An optical multilayer structure according to claim 1, wherein at least one of the first and second layers is a composite layer made of two or more layers having optical characteristics different from each other.

9. An optical multilayer structure according to claim 3, wherein the second layer is a silicon nitride film.

10. An optical multilayer structure according to claim 9, wherein the second layer is made by a silicon nitride layer and a transparent conductive layer.

11. An optical multilayer structure according to claim 6, wherein at least one of the first and second layers partly includes a transparent conductive layer, and the driving means changes the optical size of the gap portion by an electrostatic force generated by application of a voltage to the transparent conductive film.

12. An optical multilayer structure according to claim 11, wherein the transparent conductive film is made of ITO, SnO₂, or ZnO.

13. An optical multilayer structure according to claim 1, wherein the gap portion is filled with air, transparent gas, or transparent liquid.

14. An optical multilayer structure according to claim 1, wherein the gap portion is in vacuum.

15. An optical multilayer structure according to claim 1, wherein the light-absorbing first layer is made of any one of metal, metal oxide, metal nitride, carbide, and semiconductor.

16. An optical multilayer structure according to claim 4, wherein the light-absorbing substrate or light-absorbing thin film is made of any one of metal, metal oxide, metal nitride, carbide, and semiconductor.

17. An optical multilayer structure according to claim 1, wherein an optical thickness of the second layers is λ

/4 or less (λ

;

design wavelength of incident light).

18. An optical multilayer structure according to claim 1, wherein the first layer is made of silicon and the optical thickness of the second layer is λ

/2 or less (λ

;

design wavelength of incident light).

19. An optical multilayer structure according to claim 1, wherein the substrate is made of carbon, graphite, carbide, or a transparent material, and the optical thickness of the second layer is λ

/4 or less (λ

;

design wavelength of incident light).

20. An optical multilayer structure according to claim 1, wherein the substrate is made of carbon, graphite, carbide, or a transparent material, the first layer is made of silicon, and the optical thickness of the second layer is λ

/4 or less (λ

;

design wavelength of incident light).

21. An optical multilayer structure according to claim 6, wherein the driving means changes an optical size of the gap portion by using a magnetic force.

22. An image display for displaying a two-dimensional image by irradiating a plurality of optical switching devices arranged one-dimensionally or two-dimensionally with light,

the optical switching device comprising:

an optical multiplayer structure having a substrate, a light-absorbing first layer, a gap portion having a changeable size capable of causing an optical interference phenomenon, and a second layer; and

driving means for changing an optical size of the gap portion.