US-20260130007-A1 - SUPER-LUMINESCENT DIODE AND EXTERNAL CAVITY LASER INCLUDING THE SAME

Abstract

Disclosed are a super-luminescent diode and an external cavity laser including the same. The diode includes a substrate including a gain region, a window region spaced apart from the gain region, and a tapered region between the window region and the gain region, an active waveguide layer including a lower waveguide layer provided on the substrate and extending from the gain region to the window region, and an upper waveguide layer provided on the lower waveguide layer and extending from the gain region to the tapered region, and a clad layer provided on the lower waveguide layer and the upper waveguide layer of the active waveguide layer. The lower waveguide layer and the upper waveguide layer may include asymmetric separate confinement heterostructure (SCH) layers.

Inventors

• Su Hwan Oh
• Kisoo Kim
• Hongseung KIM

Assignees

• ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE

Dates

Publication Date

20260507

Application Date

20250904

Priority Date

20241107

Claims (20)

1. 1 . A super-luminescent diode comprising: a substrate including a gain region, a window region spaced apart from the gain region, and a tapered region between the window region and the gain region; an active waveguide layer including a lower waveguide layer provided on the substrate and extending from the gain region to the window region, and an upper waveguide layer provided on the lower waveguide layer and extending from the gain region to the tapered region; and a clad layer provided on the lower waveguide layer and the upper waveguide layer of the active waveguide layer, wherein each of the lower waveguide layer and the upper waveguide layer comprises asymmetric separate confinement heterostructure (SCH) layers.
2. 2 . The super-luminescent diode of claim 1 , wherein the lower waveguide layer and the upper waveguide layer are tapered in opposite directions in the tapered region.
3. 3 . The super-luminescent diode of claim 1 , wherein the lower waveguide layer comprises: a first lower SCH layer having an energy bandgap higher than that of the substrate; a second lower SCH layer provided on the first lower SCH layer, the second lower SCH layer being thinner than that of the first lower SCH layer and having an energy bandgap higher than that of the first lower SCH layer; and a third lower SCH layer provided on the second lower SCH layer and having an energy bandgap higher than that of the second lower SCH layer.
4. 4 . The super-luminescent diode of claim 3 , wherein the upper waveguide layer comprises: a fourth lower SCH layer provided on the third lower SCH layer and having an energy bandgap higher than that of the third lower SCH layer; and a core layer provided on the fourth lower SCH layer and including quantum well structures and barrier layers between the quantum well structures.
5. 5 . The super-luminescent diode of claim 4 , wherein the upper waveguide layer is provided on the core layer and further comprises a first upper SCH layer having same energy bandgap as that of the fourth lower SCH layer.
6. 6 . The super-luminescent diode of claim 5 , wherein the upper waveguide layer is provided on the first upper SCH layer and further comprises a second upper SCH layer having same energy bandgap as that of the third lower SCH layer.
7. 7 . The super-luminescent diode of claim 6 , wherein the upper waveguide layer is provided on the second upper SCH layer and further comprises a third upper SCH layer having same energy bandgap as that of the second lower SCH layer.
8. 8 . The super-luminescent diode of claim 7 , wherein the upper waveguide layer is provided on the third upper SCH layer and further comprises a fourth upper SCH layer having same energy bandgap as that of the first lower SCH layer.
9. 9 . The super-luminescent diode of claim 8 , wherein each of the first lower SCH layer, the second lower SCH layer, the third lower SCH layer, the fourth lower SCH layer, the core layer, the first upper SCH layer, the second upper SCH layer, the third upper SCH layer, and the fourth upper SCH layer comprises InGaAsP.
10. 10 . The super-luminescent diode of claim 1 , further comprising: an ohmic contact layer on the clad layer; an upper electrode on the ohmic contact layer; and a lower electrode under the substrate.
11. 11 . An external cavity laser comprising: an element substrate; a super-luminescent diode provided at one side of the element substrate; a mirror provided at another side of the element substrate; and an optical filter provided between the mirror and the super-luminescent diode, wherein the super-luminescent diode comprises: a substrate including a gain region, a window region spaced apart from the gain region, and a tapered region between the window region and the gain region; an active waveguide layer including a lower waveguide layer provided on the substrate and extending from the gain region to the window region, and an upper waveguide layer provided on the lower waveguide layer and extending from the gain region to the tapered region; and a clad layer provided on the lower waveguide layer and the upper waveguide layer of the active waveguide layer, wherein each of the lower waveguide layer and the upper waveguide layer comprises asymmetric separate confinement heterostructure (SCH) layers.
12. 12 . The external cavity laser of claim 11 , further comprising: a first coating layer provided at one side of the super-luminescent diode; and a second coating layer provided at another side of the super-luminescent diode.
13. 13 . The external cavity laser of claim 12 , wherein the first coating layer comprises a half-transmissive coating layer or a total-reflective coating layer, and the second coating layer comprises an anti-reflective layer.
14. 14 . The external cavity laser of claim 11 , wherein the filter comprises: a filter substrate; half-transmissive layers on the filter substrate; and transmissive layers between the half-transmissive layers.
15. 15 . The external cavity laser of claim 11 , further comprising a lens provided between the filter and the super-luminescent diode.
16. 16 . A super-luminescent diode manufacturing method comprising: providing a lower waveguide layer and an upper waveguide layer on a substrate including a gain region, a window region spaced apart from the gain region, and a tapered region between the gain region and the window region; removing a portion of the upper waveguide layer in the tapered region and the window region to taper the upper waveguide layer in the tapered region in one direction; and removing a portion of the upper waveguide layer in the gain region and a portion of the lower waveguide layer and the upper waveguide layer in the gain region, the tapered region, and the window region to taper the lower waveguide layer in a direction opposite to the tapering direction of the upper waveguide layer, wherein each of the upper waveguide layer and the lower waveguide layer comprises asymmetric SCH layers.
17. 17 . The super-luminescent diode manufacturing method of claim 16 , further comprising providing a current blocking layer on walls of the lower waveguide layer and the upper waveguide layer.
18. 18 . The super-luminescent diode manufacturing method of claim 17 , further comprising: providing a clad layer on the current blocking layer, the upper waveguide layer, and the lower waveguide layer; providing an ohmic contact layer on the clad layer; providing an upper electrode on the ohmic contact layer; and providing a lower electrode on a lower surface of the substrate.
19. 19 . The super-luminescent diode manufacturing method of claim 16 , wherein the lower waveguide layer comprises: a first lower SCH layer having an energy bandgap higher than that of the substrate; a second lower SCH layer provided on the first lower SCH layer, being thinner than the first lower SCH layer, and having an energy bandgap higher than that of the first lower SCH layer; and a third lower SCH layer provided on the second lower SCH layer and having an energy bandgap higher than that of the second lower SCH layer.
20. 20 . The super-luminescent diode manufacturing method of claim 19 , wherein the upper waveguide layer comprises: a fourth lower SCH layer provided on the third lower SCH layer and having an energy bandgap higher than that of the third lower SCH layer; a core layer provided on the fourth lower SCH layer and including quantum well structures and barrier layers between the quantum well structures; a first upper waveguide layer provided on the core layer and having same energy bandgap as that of the fourth lower SCH layer; a second upper SCH layer provided on the first upper SCH layer and having same energy bandgap as that of the third lower SCH layer; a third lower SCH layer provided on the second upper SCH layer and having same energy bandgap as that of the second lower SCH layer; and a fourth upper SCH layer provided on the third upper SCH layer and having same energy bandgap as that of the first lower SCH layer.

Description

CROSS-REFERENCE TO RELATED APPLICATION This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application No. 10-2024-0156660, filed on Nov. 7, 2024, the entire contents of which are hereby incorporated by reference. BACKGROUND The present disclosure herein relates to a super-luminescent diode, and more particularly, to a super-luminescent diode operating at high power and high efficiency and an external cavity laser including the same. Typically, a super-luminescent diode (SLD) is a light source having an intermediate feature of a light-emitting diode (LED) and a laser diode (LD), and has recently emerged as a light source of an optical sensor. Such an SLD is applied as a light source of a fiber-optic gyroscope used as a navigation device in a vehicle, a ship, an aircraft, etc., optical coherence tomography that is a diagnostic imaging technique for examining, with high resolution, multiple faces of micro-structure in a living tissue, and an external cavity laser (ECL). SUMMARY The present disclosure provides a super-luminescent diode capable of operating at high power and high efficiency, and an external cavity laser including the same. An embodiment of the inventive concept provides a super-luminescent diode comprising: a substrate including a gain region, a window region spaced apart from the gain region, and a tapered region between the window region and the gain region; an active waveguide layer including a lower waveguide layer provided on the substrate and extending from the gain region to the window region, and an upper waveguide layer provided on the lower waveguide layer and extending from the gain region to the tapered region; and a clad layer provided on the lower waveguide layer and the upper waveguide layer of the active waveguide layer. Here, each of the lower waveguide layer and the upper waveguide layer may include asymmetric separate confinement heterostructure (SCH) layers. In an embodiment, the lower waveguide layer and the upper waveguide layer may be tapered in opposite directions in the tapered region. In an embodiment, the lower waveguide layer may comprise: a first lower SCH layer having an energy bandgap higher than that of the substrate; a second lower SCH layer provided on the first lower SCH layer, being thinner than the first lower SCH layer, and having an energy bandgap higher than that of the first lower SCH layer; and a third lower SCH layer provided on the second lower SCH layer and having an energy bandgap higher than that of the second lower SCH layer. In an embodiment, the upper waveguide layer may comprise: a fourth lower SCH layer provided on the third lower SCH layer and having an energy bandgap higher than that of the third lower SCH layer; and a core layer provided on the fourth lower SCH layer and including quantum well structures and barrier layers between the quantum well structures. In an embodiment, the upper waveguide layer may be provided on the core layer and further include a first upper SCH layer having same energy bandgap as that of the fourth lower SCH layer. In an embodiment, the upper waveguide layer may be provided on the first upper SCH layer and further include a second upper SCH layer having same energy bandgap as that of the third lower SCH layer. In an embodiment, the upper waveguide layer may be provided on the second upper SCH layer and further include a third upper SCH layer having same energy bandgap as that of the second lower SCH layer. In an embodiment, the upper waveguide layer may be provided on the third upper SCH layer and further include a fourth upper SCH layer having same energy bandgap as that of the first lower SCH layer. In an embodiment, each of the first lower SCH layer, the second lower SCH layer, the third lower SCH layer, the fourth lower SCH layer, the core layer, the first upper SCH layer, the second upper SCH layer, the third upper SCH layer, and the fourth upper SCH layer may InGaAsP. In an embodiment, the super-luminescent diode may further include: an ohmic contact layer on the clad layer; an upper electrode on the ohmic contact layer; and a lower electrode under the substrate. In an embodiment of the inventive concept, an external cavity laser comprises: an element substrate; a super-luminescent diode provided at one side of the element substrate; a mirror provided at another side of the element substrate; and an optical filter provided between the mirror and the super-luminescent diode. Here, the super-luminescent diode may comprise: a substrate including a gain region, a window region spaced apart from the gain region, and a tapered region between the window region and the gain region; an active waveguide layer including a lower waveguide layer provided on the substrate and extending from the gain region to the window region, and an upper waveguide layer provided on the lower waveguide layer and extending from the gain region to the tapered region; and a clad layer provi