Optical coupler

• US 20040264863A1
• Filed: 08/12/2004
• Published: 12/30/2004
• Est. Priority Date: 08/02/2001
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Urino, Yutaka, Suzuki, Kouichi, Hanada, Tadahiko
• Granted Patent: US 7,020,367 B2
• Time in Patent Office: Days
• US Class Current: 385/43
• CPC Class Codes: G02B 2006/12195 Tapering
• CPC Class Codes: G02B 6/12016 characterised by the input or output waveguides, e.g. tapered waveguide ends, coupled together pairs of output waveguides
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/25 Preparing the ends of light guides for coupling, e.g. cutting
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide

Abstract

An optical coupler comprises a tapered waveguide formed so that a waveguide width may be narrower as going from a predetermined starting position toward an emission end of a light signal. A difference between a first coupling factor and a second coupling factor is set within a predetermined range. The first coupling factor is the coupling factor to a waveguide having the same width as that in a first position in an inherent mode in the case where the tapered waveguide is cut in the first position. A second coupling factor is the coupling factor to a waveguide having the same width as that in a second position where is separated at a predetermined distance from the first position along a direction toward the emission end in an inherent mode in the case where the tapered waveguide is cut in the second position.

Claims

1. An optical coupler characterized by comprising a tapered waveguide formed so that a waveguide width may be narrower as going from a predetermined starting position toward an emission end of a light signal, wherein a difference between a first coupling factor to a waveguide having the same width as that in a first position in an inherent mode in the case where said tapered waveguide is cut in said first position and a second coupling factor to a waveguide having the same width as that in a second position where is separated at a predetermined distance from said first position along a direction toward said emission end in an inherent mode in the case where said tapered waveguide is cut in said second position is set within a predetermined range.

2. An optical coupler according to claim 1, wherein said difference of the first coupling factor and the second coupling factor is lower than a third value obtained by subtracting from 1 a second value resulted by raising a first value obtained by subtracting from 1 desired coupling loss to a subject, to which the light signal emitted from the emission end at a tip of said emission end is coupled, to the power of a number of division of dividing said tapered waveguide by the distance between said first position and said second position.

3. An optical coupler according to claim 1, wherein said waveguide is constituted by a silicon system glass material.

4. An optical coupler according to claim 1, wherein said waveguide is constituted by a semiconductor.

5. An optical coupler according to claim 1, wherein said waveguide is constituted by a polymeric material.

6. An optical coupler characterized by comprising a tapered waveguide formed so that a waveguide width may be narrower as going from a predetermined starting position toward an emission end of a light signal, wherein change in the width of the tapered waveguide changes toward an traveling direction of said light signal in a form of an exponential function.

7. An optical coupler according to claim 6, wherein said exponential function is expressed by W(z)=(W_i−

W_o)exp(−

α

₁z)+W_o, assuming that a waveguide width is W, a distance from a start point of said tapered waveguide is z, an initial waveguide width of the tapered waveguide is W_i, a width of said emission end is W_o, and a constant calculated from of an initial waveguide width deduction value at the time of starting of said tapered waveguide is α

₁.

8. An optical coupler according to claim 6, wherein said waveguide is constituted by a silicon system glass material.

9. An optical coupler according to claim 6, wherein said waveguide is constituted by a semiconductor.

10. An optical coupler according to claim 6, wherein said waveguide is constituted by a polymeric material.