FABRICATION-TOLERANT WAVEGUIDES AND RESONATORS

• US 20110026879A1
• Filed: 10/15/2010
• Published: 02/03/2011
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Barwicz, Tymon, Popovic, Milos
• Granted Patent: US 8,068,706 B2
• Time in Patent Office: Days
• US Class Current: 385/28
• CPC Class Codes: G02B 6/107 Subwavelength-diameter waveguides, e.g. nanowires
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/1223 high refractive index type, i.e. high-contrast waveguides
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/3133 the optical waveguides being made of semiconducting materials
• CPC Class Codes: G02F 2201/063 ridge; rib; strip loaded
• CPC Class Codes: G02F 2201/125 delta-beta
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/585 Add/drop devices
• CPC Class Codes: H04J 14/021 Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
• CPC Class Codes: H04Q 2213/1301 Optical transmission, optical switches

Abstract

An optical waveguide having a core region with a substantially rectangular cross-section with a selected aspect ratio of width to height. Embodiments include devices incorporating the optical waveguide and methods for using the optical waveguide.

Claims

1. A method of propagating optical signals through a waveguide with low loss and low device sensitivity to fabrication imperfections, the method including the steps of:

providing an optical waveguide comprising a core region including a core material and having a substantially rectangular cross-section with an aspect ratio of width to height of about 1.8;

1, the cross-section supporting at least two TE modes and only one TM mode, and the optical waveguide having at least one TE mode with a higher effective index than the TM mode; and

propagating light in the optical waveguide solely in the TM mode.

2. The method of claim 1, wherein the core material comprises a semiconductor and is substantially transparent within an operating wavelength range having a free-space center wavelength.

3. The method of claim 2, wherein the free-space center wavelength is about 1.5 μ

m.

4. The method of claim 1, wherein a core refractive index of the core material is approximately equal to a refractive index of crystalline silicon.

5. The method of claim 1, wherein the optical waveguide further comprises a cladding region surrounding the core region, the cladding region (i) comprising at least one cladding material having a refractive index, and (ii) having a maximum cladding refractive index equal to the largest refractive index of the at least one cladding material.

6. The method of claim 5, wherein a core refractive index of the core material is at least 1.5 times as large as the maximum cladding refractive index.

7. The method of claim 5, wherein the maximum cladding refractive index is approximately equal to a refractive index of silica.

8. The method of claim 1, wherein the aspect ration, the height, and the width of the cross-section cooperate to support the single TM mode.

9. The method of claim 8, wherein the cross-section encompasses a largest possible area corresponding to the given aspect ratio.

10. The method of claim 1, wherein the optical waveguide comprises:

a slanted sidewall defining a sidewall angle with respect to a top portion of the optical waveguide,

wherein the sidewall angle is less than 5 degrees.

11. The method of claim 1, wherein an area of the cross-section is less than or equal to about 0.403−

0.285×

[sech(1.65×

A_R)]^0.36 square micrometers.

12. The method of claim 11, wherein the area of the cross-section is equal to or greater than about 0.047+0.057×

[sech(3×

A_R)]^0.44 square micrometers.

13. A method of propagating optical signals through a waveguide with low loss and low device sensitivity to fabrication imperfections, the method including the steps of:

providing an optical waveguide having a cross-section with an aspect ratio of width to height of about 1.8;

1, the cross-section supporting at least two TE modes and only one TM mode, and the optical waveguide having at least one TE mode with a higher effective index than the TM mode; and

propagating light in the optical waveguide solely in the TM mode.