Enhanced coupling strength grating having a cover layer

Patent metadata

Field	Value
Publication number	US-10620379-B2
Application number	US-201916523291-A
Country	US
Kind code	B2
Filing date	Jul 26, 2019
Priority date	Sep 5, 2013
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

The present invention includes an optical waveguide with a grating and a method of making the same for increasing the effectiveness of the grating. In one example, the grating is at least partially covered by a liner layer disposed on at least a portion of a grating; and a cover layer disposed on the liner layer, wherein a first material selected for the core and ridges and a second material selected for the liner layer are selected to provide a difference in the index of refraction between the first and second material that is sufficient to provide a contrast therebetween.

First claim

What is claimed is:

1. A grating, comprising:
a substrate;
a core comprising a first material having an index of refraction (n core ) disposed on the substrate;
one or more ridges and one or more grooves comprising the first material formed on the core, wherein the one or more grooves are adjacent to, or between the one or more ridges, and the ridges and grooves form a grating;
a liner layer comprising a second material having an index of refraction (n liner ) disposed on at least a portion of a grating cycle;
an amorphous or crystalline cover layer comprising a third material having an index of refraction (n cover ) disposed on the liner layer;
a superstrate or air layer disposed above the cover layer; and
wherein the third material is not the same as the first material, n core ≠n liner and n liner ≠n cover .

2. The grating of claim 1 , wherein the liner layer is disposed on at least one of:
the bottom of the groove;
one or more sidewalls of the ridges;
on the top of the ridges;
two or more liner layers in the groove; or
on the sides of the ridges that do not have a top.

3. The grating of claim 1 , wherein the liner layer selected from one or more of the following optional configurations:
(a) the liner layer is not contiguous;
(b) the liner layer is disposed on a first sidewall, a second sidewall or both the first and second sidewalls of the ridges;
(c) the liner layer is defined further as one or more liner layers that are contiguous and that follow the contour of the ridges and the grooves;
(d) the liner layer is not contiguous, wherein the liner layer is defined further as being substantially parallel to a bottom of the one or more grooves, and the non-contiguous layers are separated by one or more amorphous or crystalline cover layers;
(e) the liner layer is defined further as two or more liner layers that are contiguous and that follow the contour of the ridges, and each of the two or more liner layers are separated by one or more amorphous or crystalline cover layers;
(f) the liner layer is disposed on one or more tops of the ridges, one or more grooves between the ridges, or both the top of the ridges, and the grooves between the ridges;
(g) the liner layer is disposed on a first sidewall, one or more tops of the ridges, and one or more grooves between the ridges, to provide an effective blazed grating;
(h) the liner layer is disposed on a first sidewall and one or more tops of the ridges; or
(i) the liner layer is disposed on one or more first sidewall or second sidewall of one or more waveguiding structures for grating coupling (inward or outward).

4. The grating of claim 1 , wherein the liner layer is disposed on a high index contrast Si/SiO 2 waveguide to further enhance the performance of the grating.

5. The grating of claim 1 , wherein the amorphous or crystalline cover layer is selected to provide the second difference in the index of refraction between the amorphous or crystalline cover layer and the liner layer that is similar to the first difference in the index of refraction provided between the core and the liner layer.

6. The grating of claim 1 , wherein the liner layer is selected from at least one of SiO, SiO 2 , MgF 2 , Al 2 O 3 , HfO 2 , Ta 2 O 4-5 , Sc 2 O 3 , ZrO 2 , TiO 2 , CaF 2 , ThF 4 , ZnS, ZnSe, polymers, and silicon nitride.

7. The grating of claim 1 , wherein the liner layer comprises a variable thickness to provide at least one of varying the strength of the coupling, an effective variable duty cycle, an effective variable grating depth, a Gaussian profile in a radiating coupler grating, or a near-Gaussian profile in a radiating coupler grating.

8. The grating of claim 1 , wherein the liner layer is selected to provide at least one of an optical loss or an optical gain.

9. The grating of claim 1 , wherein the optical waveguide is at least one of a distributed Bragg reflectors (DBRs) or a distributed Bragg deflectors (DBDs).

10. The grating of claim 1 , wherein the optical waveguide is defined further as comprising at least two ECS gratings to make an edge-emitting DBR laser; one ECS grating and one regular DBR grating to make an edge-emitting DBR laser; two ECS gratings with a straight ECS outcoupler grating to make a surface-emitting laser; ECS grating and one regular DBR grating with a straight ECS outcoupler grating to make a surface-emitting laser; two ECS gratings with a “fan-out” ECS outcoupler grating to make a surface-emitting laser; one ECS grating and one regular DBR grating with a “fan-out” ECS outcoupler grating to make a surface-emitting laser; two ECS gratings with a standard grating outcoupler grating to make a surface-emitting laser; one ECS grating and one regular DBR grating with a standard grating outcoupler grating to make a surface-emitting laser; one or more ECS grating output couplers with low back reflection on both ends to make a surface-normal coupled semiconductor optical amplifier (SOA) or optical gain block; or one or more ECS gratings or regular DBR gratings configures as a mirror with high reflectivity and another ECS grating as an output coupler to make a surface-emitting reflective semiconductor optical amplifier (RSOA) or an optical gain block; a hybrid external cavity laser and tunable laser using SOA or RSOA with ECS grating output couplers integrated with a waveguide or free space wavelength control optics; or an enhanced grating for high density and low loss integration of III/V laser sources for silicon photonic interconnects.

11. The grating of claim 1 , wherein the optical waveguide provides lateral optical confinement with a mesa structure and the enhanced grating is on at least one of: (1) the top surface of the mesa structure; (2) one or more lateral surfaces of the mesa structure; or (3) on the surfaces adjacent the mesa structure.

12. The grating of claim 1 , wherein an enhanced grating for grating-assisted directional couplers; enhanced grating for multiply resonant distributed feedback lasers; or an enhanced grating for multiplying resonant distributed Bragg reflector lasers; an enhanced grating in optical fibers for sampling or detecting light in optical fibers by grating outcouplers; an enhanced gratings in optical fibers for (1) sampling or detecting light in optical fibers by grating outcouplers operating near the second order Bragg condition; (2) sampling or detecting light in optical fibers by grating outcouplers operating as distributed Bragg deflectors; (3) to couple light into optical fibers; a curved, enhanced gratings to make unstable resonator semiconductor lasers; an enhanced grating to reduce the etch depth for the placement of distributed Bragg reflector gratings in semiconductor lasers, which results in simplified processing for DBR lasers; an enhanced grating to reduce the etch depth for the placement of distributed Bragg reflector gratings in photonic devices, which results in simplified processing for photonic devices; and enhanced grating to reduce the etch depth for the placement of gratings in photonic devices, which results in simplified processing for photonic devices; or an enhanced grating to reduce the etch depth for the placement of coupling gratings in photonic devices, which results in simplified processing for photonic devices.

13. The grating of claim 1 , wherein the grating comprise a period that is equal to about the wavelength of the light propagating in the optical waveguide to produce an outcoupling in about 10 to 50 grating cycles.

14. The grating of claim 1 , wherein the grating comprise a period that is equal to about one half the wavelength of the light propagating in the optical waveguide, and in

Assignees

• Univ Southern Methodist
• Orade Int Corporation
• Oracle Int Corp

Inventors

• Evans Gary A
• Butler Jerome K
• Kirk Jay B
• He Ruo-Hua
• Yao Jin
• Li Guoliang
• Zheng Xuezhe
• Krishnamoorthy Ashok V

Classifications

• G02B6/136

  by etching · CPC title

• G02B6/1223

  high refractive index type, i.e. high-contrast waveguides · CPC title

• H01S5/187

  using Bragg reflection · CPC title

• G02B2006/12176

  Etching · CPC title

• H01S5/125

  Distributed Bragg reflector [DBR] lasers · CPC title