Integrated 3-dimensional multi-layer thin-film optical couplers and attenuators

• US 6,542,671 B1
• Filed: 12/12/2001
• Issued: 04/01/2003
• Est. Priority Date: 12/12/2001
• Status: Expired due to Fees

• Current Assignee: Super Talent Electronics, Inc.
• Original Assignee: Super Light Wave Corporation
• Inventors: Ma, Abraham C., Chu, Tzu-Yih
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US09/683,306
• Time in Patent Office: 475 Days
• Field of Search: 385/47, 385/14, 385/132
• US Class Current: 385/47
• CPC Class Codes: G02B 2006/12109 Filter
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
• CPC Class Codes: G02B 6/29364 Cascading by a light guide path between filters or filtering operations, e.g. fibre interconnected single filter modules

Abstract

An integrated optical device has two waveguide layers that are patterned to provide 2-dimensional interconnected networks of waveguides. A filter layer between the two waveguide layers is made by sputter deposition of thin films with alternating indexes of refraction. Light traveling vertically through the filter layer experiences an interferometric effect. A deflecting bump is formed in the plane of the lower waveguide layer. The bump is isotropicly etched, undercutting a photo-mask over the bump, producing a rounded, concave profile to the bump. High-index material is deposited over the bump and patterned to form a waveguide that has light deflected by the bump upward. The filter is formed over the bump to receive the deflected light. The filter reflects some light back down to the bump to another waveguide in the first layer. Light transmitted vertically up through the filter is bent to the horizontal plane of the upper waveguide layer.

Claims

1. A three-dimensional integrated optical network comprising:

a substrate having a top surface;

a lower waveguide layer, formed above the substrate, containing optical waveguides in a lower plane substantially parallel to the top surface;

a deflecting bump, formed above the substrate and formed in the lower plane of the lower waveguide layer, the deflecting bump formed before the lower waveguide layer is formed, the lower waveguide layer bending upward over the deflecting bump;

a filter, formed over the deflecting bump, the filter receiving incident light from the lower waveguide layer that is deflected upward out of the lower plane by the deflecting bump, the filter reflecting a reflected portion of the incident light back down to the deflecting bump which bends the reflected portion back into a waveguide in the lower plane of the lower waveguide layer; and

an upper waveguide layer containing optical waveguides in an upper plane that is above and substantially parallel to the lower plane and the top surface;

wherein the filter transmits a transmitted portion of the incident light, the transmitted portion of light being transmitted upward through the filter and bent into the upper plane by a waveguide from the upper waveguide layer that contacts the filter,

whereby the filter receives light deflected upward from the lower waveguide layer by the deflecting bump, the filter transmitting light upward to the upper waveguide layer and reflecting light back downward to the lower waveguide layer.

2. The three-dimensional integrated optical network of claim 1 wherein the deflecting bump is has a curved vertical profile that is produced by etching with at least a partially isotropic etch that undercuts a mask that defines the deflecting bump, the lower waveguide layer formed over the deflecting bump so that the lower waveguide layer curves upward above the lower plane to contact a lower surface of the filter above the deflecting bump,

whereby the lower waveguide layer contacts the filter above the deflecting bump with the curved vertical profile.

3. The three-dimensional integrated optical network of claim 2 wherein the filter is formed by repeatedly and alternately depositing a first film with a first index of refraction and a second film with a second index of refraction to form a stack of alternating first and second films, wherein the first index of refraction does not equal the second index of refraction,

whereby the filter is an alternating stack of thin films.

4. The three-dimensional integrated optical network of claim 3 wherein the filter includes a gradient film with a gradient index of refraction, an index of refraction increasing or decreasing with distance above the top surface,

wherein the gradient film acts as a gradient-index lens to focus light for the filter.

5. The three-dimensional integrated optical network of claim 4 wherein the gradient film is formed below the filter but above the lower waveguide layer, or is formed above the filter but below the upper waveguide layer.

6. The three-dimensional integrated optical network of claim 2 wherein the waveguide from the upper waveguide layer contacts the filter through an upper opening in an upper isolating layer above the filter layer but below the upper waveguide layer, wherein the upper opening has a curved vertical profile produced by etching with at least a partially isotropic etch that undercuts a mask that defines the upper opening, the upper waveguide layer formed over the upper opening and the upper isolating layer so that the upper waveguide layer curves downward below the upper plane to contact a top surface of the filter through the upper opening,

whereby the upper waveguide layer contacts the filter through the upper opening with the curved vertical profile.

7. The three-dimensional integrated optical network of claim 6 wherein the incident light travels to the filter in an input waveguide in the lower waveguide layer, while the reflected portion of light travels away from the filter in a reflected-output waveguide in the lower waveguide layer, while the transmitted portion of light travels away from the filter in a transmitted-output waveguide in the upper waveguide layer.

8. The three-dimensional integrated optical network of claim 7 wherein the lower waveguide layer is patterned to include other waveguides besides the input waveguide and the reflected-output waveguide;

wherein the upper waveguide layer is patterned to include other waveguides besides the transmitted-output waveguide,

whereby the lower waveguide layer and upper waveguide layer contain a network of waveguides.

9. The three-dimensional integrated optical network of claim 8 further comprising:

a second deflecting bump formed above the substrate and formed in the lower plane of the lower waveguide layer, the second deflecting bump formed before the lower waveguide layer is formed, the waveguide layer bending upward over the second deflecting bump;

a second input waveguide and a second reflected-output waveguide in the lower waveguide layer;

a second transmitted-output waveguide in the upper waveguide layer;

a second filter formed in a filter layer that contains the filter, the second filter being formed over the second deflecting bump, the second filter receiving light from the second input waveguide in the lower waveguide layer and reflecting light to the second reflected-output waveguide in the lower waveguide layer and transmitting light upward to the second transmitted-output waveguide in the upper waveguide layer,

whereby at least two filters are integrated on the substrate using the lower waveguide layer and the upper waveguide layer to route light.

10. The three-dimensional integrated optical network of claim 9 wherein the reflected-output waveguide is a same waveguide as the second input waveguide;

whereby the second filter receives light reflected from the filter, and whereby the second reflected-output waveguide and the second transmitted-output waveguide output light that is filtered twice.

11. The three-dimensional integrated optical network of claim 9 further comprising:

a third input waveguide and a third reflected-output waveguide in the upper waveguide layer;

a third transmitted-output waveguide in the lower waveguide layer;

a third filter formed in the filter layer, the third filter receiving light from the third input waveguide in the upper waveguide layer and reflecting light to the third reflected-output waveguide in the upper waveguide layer and transmitting light downward to the third transmitted-output waveguide in the lower waveguide layer,

whereby light is transmitted downward through the third filter but upward through the filter and the second filter.

12. The three-dimensional integrated optical network of claim 11 wherein the lower waveguide layer and the upper waveguide layer are formed from a high-refractive-index material and are surrounded by isolating layers formed from a low-refractive-index material;

wherein the deflecting bump is formed from the low-refractive-index material.

13. The three-dimensional integrated optical network of claim 12 further comprising:

an optical absorber, coupled to receive light from a waveguide in the upper waveguide layer, the optical absorber absorbing the light and generating heat; and

a heat sink, attached to the optical absorber, for drawing heat away from the optical absorber,

whereby light is absorbed and generated heat removed.

14. An integrated multi-layer optical device comprising:

input waveguide means, formed using a first waveguide layer of optical conducting material, for conducting an input beam of light in a horizontal direction;

deflect means, formed from an optical isolator material, for deflecting light in the input waveguide means to a vertical direction from the horizontal direction;

filter means, receiving light from the input waveguide means that is deflected to the vertical direction by the deflect means, for reflecting a reflected portion of received light and for vertically transmitting a transmitted portion of received light;

reflected-output waveguide means, formed using the first waveguide layer, for conducting the reflected portion of received light collected from the filter means; and

transmitted-output waveguide means, formed using a second waveguide layer, for conducting the transmitted portion of received light vertically transmitted through the filter means,

whereby the input beam is vertically transmitted through the filter means to the second waveguide layer and reflected to the first waveguide layer.

15. The integrated multi-layer optical device of claim 14 further comprising:

second deflect means, formed from the optical isolator material, for deflecting light to a vertical direction from the horizontal direction;

second filter means, receiving light deflected by the second deflect means from the reflected-output waveguide means or from another waveguide in the first waveguide layer, for reflecting a second reflected portion of received light and for vertically transmitting a second transmitted portion of received light;

second reflected-output waveguide means, formed using the first waveguide layer, for conducting the second reflected portion of received light collected from the second filter means; and

second transmitted-output waveguide means, formed using the second waveguide layer, for conducting the second transmitted portion of received light vertically transmitted through the second filter means,

whereby at least two filters are integrated on the integrated multi-layer optical device.

16. The integrated multi-layer optical device of claim 15 wherein the second filter means is formed from a same filter layer as the filter means.

17. The integrated multi-layer optical device of claim 14 further comprising:

second deflect means, formed from the optical isolator material, for deflecting light to a vertical direction from the horizontal direction, the second deflect means formed in a plane of the second waveguide layer;

second filter means, receiving light deflected by the second deflect means from the transmitted-output waveguide means or from another waveguide in the second waveguide layer, for reflecting a second reflected portion of received light and for vertically transmitting a second transmitted portion of received light;

second reflected-output waveguide means, formed using the second waveguide layer, for conducting the second reflected portion of received light collected from the second filter means; and

second transmitted-output waveguide means, formed using a third waveguide layer, for conducting the second transmitted portion of received light vertically transmitted through the second filter means,

whereby at least two filters and three waveguide layers are integrated on the integrated multi-layer optical device.

18. A multi-layer optical coupler comprising:

a substrate for supporting the multi-layer optical coupler;

a bump formed on the substrate, with a curved edge for guiding light from a first horizontal plane to an upward direction;

an input waveguide formed by patterning a lower waveguide layer of high-refractive index material, the input waveguide guiding light in the first horizontal plane to the bump and guiding light up over the bump;

a reflected-output waveguide formed by patterning of the lower waveguide layer, the reflected-output waveguide collecting light reflected downward near the bump and guiding light in the first horizontal plane;

a first low-refractive-index layer, formed over lower waveguides formed by patterning the lower waveguide layer and formed over the substrate between the lower waveguides that include the input waveguide and the reflected-output waveguide;

wherein a top surface of the first low-refractive-index layer is planarized to have a substantially flat top surface, the first low-refractive-index layer having a first opening over the bump that exposes the input waveguide and the reflected-output waveguide over the bump;

a filter formed over the first opening and contacting the input waveguide and the reflected-output waveguide over the bump, the filter upwardly transmitting a transmitted portion of light and downwardly reflecting a reflected portion of light;

a second low-refractive-index layer, formed over the filter and over the first low-refractive-index layer, having a second opening over a portion of a top surface of the filter; and

a transmitted-output waveguide formed by patterning an upper waveguide layer of high-refractive index material, the transmitted-output waveguide guiding light in a second horizontal plane that is parallel to and above the first horizontal plane;

wherein the transmitted-output waveguide includes a portion that descends below the second horizontal plane through the second opening to contact the top surface of the filter;

wherein the transmitted-output waveguide receives the transmitted portion of light transmitted upwardly through the filter, the transmitted-output waveguide bending the transmitted portion of light into the second horizontal plane;

whereby light is guided from the first horizontal plane of waveguides upwardly to the filter and transmitted through the filter to the second horizontal plane of waveguides and reflected downwardly to the first horizontal plane of waveguides.

19. The multi-layer optical coupler of claim 18 wherein the bump has a second curved edge for guiding reflected light from the filter to the reflected-output waveguide in the first horizontal plane.

20. The multi-layer optical coupler of claim 19 further comprising:

additional bumps formed on the substrate;

additional filters formed in a filter layer that includes the filter, the additional filters formed over the additional bumps formed on the substrate;

wherein waveguides in the lower waveguide layer make contact with the additional filters through additional openings in the first low-refractive-index layer under the additional filters;

wherein waveguides in the upper waveguide layer make contact with top surfaces of the additional filters through additional openings in the second low-refractive-index layer above the additional filters,

whereby a network of the additional filters and waveguides is integrated on the substrate.