Multilayer thin film dielectric bandpass filter

• US 5,926,317 A
• Filed: 11/06/1996
• Issued: 07/20/1999
• Est. Priority Date: 11/06/1996
• Status: Expired due to Term

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: JDS Fitel, Inc. (Lumentum Holdings Inc.)
• Inventors: Cushing, David Henry
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US08/743,734
• Time in Patent Office: 986 Days
• Field of Search: 359/588, 359/590, 359/589, 359/580, 359/900
• US Class Current: 359/588
• CPC Class Codes: G02B 5/288 comprising at least one thin film resonant cavity, e.g. in bandpass filters
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A design for producing bandpass filters with passbands that are centered at the same wavelength for each mode of polarization. Filters are of the all-dielectric type that consist of single and multiple cavities of bandpasses. All of the layers are of the Quarter Wave type for ease of manufacture with the possible exception of the last few layers being modified to reduce reflection into a new media. The basic structure of the multi-layer bandpass filter is as follows: (XY)ⁿ (YY)(XX)^m (YY)(YX)ⁿ where n and m are integers and wherein X is one of a high refractive index layer and a low refractive index layer; and, wherein Y is the other of the high and low refractive index layer, X and Y being opposite indexes of refraction.

Claims

1. A multi-layer bandpass filter comprising:

a resonant cavity, including, a first quarter-wave stack;

a half-wave array of;

one half-wave low index material, one half-wave or multiple thereof of high index material, and one half-wave low index material, and a second quarter-wave stack, wherein the first and second quarter wave stack each have an even number of layers, and wherein the layers of the two stacks are substantially opposite in order.

2. A multi-layer bandpass filter as defined in claim 1, wherein the first stack is the mirror of the second stack.

3. A bandpass filter as defined in claim 1, comprising a plurality of resonant cavities, each cavity being spaced by a quarter-wave of low index material.

4. A bandpass filter as defined in claim 1 further comprising at least one half wave layer added to at least one predetermined layer of at least one of the stacks to fine tune relative positions of diverse polarization peaks in a response of the bandpass filter.

5. A bandpass filter comprising:

a plurality of resonant cavities wherein the cavities each include, a first stack of high and low index quarter-wave layers;

a half-wave array of;

one half-wave low index material, one half-wave or multiple thereof of high index material, and one half-wave low index material; and

, a second stack of low and high index quarter-wave layers, wherein the first and second quarter wave stacks each have an even number of layers, and wherein the cavities are separated by a quarter wave of low index material.

6. A bandpass filter as defined in claim 5, wherein the first stack is the mirror of the second stack.

7. A bandpass filter as defined in claim 5 further comprising at least one half wave layer added to at least one predetermined layer of at least one of the stacks to fine tune relative positions of diverse polarization peaks in a response of the bandpass filter.

8. A bandpass filter comprising:

a plurality of resonant cavities wherein the cavities each include, a first stack of high and low index quarter-wave layers;

a half-wave array of;

one half-wave high index material, one half-wave or multiple thereof of low index material, and one half-wave high index material; and

, a second stack of low and high index quarter-wave layers, wherein the first and second quarter wave stacks each have an odd number of layers, and wherein the cavities are separated by a quarter wave of low index material.

9. A bandpass filter as defined in claim 8, wherein the first stack is the mirror of the second stack.

10. A bandpass filter as defined in claim 8 further comprising at least one half wave layer added to at least one predetermined layer of at least one of the stacks, thereby increasing the thickness of at least one of the stack layers to fine tune relative positions of diverse polarization peaks in a response of the bandpass filter.

11. A multi-layer bandpass filter wherein some of the multi-layers are a high refractive index material and some of the layers are of an opposite character, low refractive index material, the filter comprising a resonant cavity having a half-wave or multiple half-wave spacer layer of a first predetermined refractive index sandwiched between and contacting half-wave layers of an opposite character with respect to the spacer layer, said half-wave layers of opposite character being sandwiched between layers defining two quarter-wave stacks of alternating high and low index material, the quarter-wave layers adjacent and contacting the half-wave layers of opposite character being of substantially the same opposite refractive index, said quarter-wave stacks further comprising at least one half wave layer added to at least one predetermined layer of at least one of the stacks to fine tune relative positions of diverse polarization peaks in a response of the bandpass filter.

12. A multi-layer bandpass filter comprising the following layer structure:

(XY)ⁿ (YY)(XX)^m (YY)(YX)ⁿ where n and m are integers and wherein X is one of a high refractive index layer and a low refractive index layer; and

, wherein Y is the other of the high and low refractive index layer, X and Y having indexes of refraction opposite in character and substantially the same optical thicknesses; and

wherein (XY)ⁿ and (YX)ⁿ are quarter-wave stacks wherein the filter further comprises half wave layers are added to predetermined layers of at least one of (XY)ⁿ and (YX)ⁿ to fine tune relative positions of diverse polarization peaks in a response of the bandpass filter.

13. In a bandpass filter having a half wave spacer layer of high index material in-between two reflective stacks of alternating low and high index material wherein the two stacks are oppositely ordered, a method of providing a filter that is less sensitive to the polarization of incident light, said method comprising the step of:

providing at least one half wave layer of low index material adjacent to the spacer layer and the two reflective stacks.