Lasers with composite cavity of two semiconductors

Abstract

To provide lasers with a composite cavity of two semiconductors.SOLUTION: A laser may include a lower semiconductor structure and an upper semiconductor structure. The lower semiconductor structure may include a lower waveguide along a top side of the lower semiconductor structure. The upper semiconductor structure may include an upper waveguide along a bottom side of the upper semiconductor structure. The upper semiconductor structure may be positioned over the top side of the lower semiconductor structure such that a first portion of the upper waveguide vertically overlaps a second portion of the lower waveguide. A coupler between the upper waveguide and the lower waveguide may couple optical energy of the upper waveguide to the lower waveguide. The lower waveguide may comprise semiconductor material having a wider bandgap than semiconductor material of the upper waveguide.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001]

[0001] This application is a non-provisional application and claims the benefit of U.S. Provisional Application No. 63 / 389,468, filed July 15, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates generally to laser devices. [Background technology]

[0003] A vertical cavity surface emitting laser (VCSEL) has a laser cavity sandwiched between and defined by two mirror stacks. VCSELs are typically fabricated on a semiconductor substrate (often a GaAs or InP substrate), with a bottom mirror stack formed on top of the substrate, which is then covered by the laser cavity and the top mirror stack. Each mirror stack includes many epitaxial layers of alternating refractive index values ​​(e.g., alternating between "high" and "low" refractive index values). The cavity region itself includes an active region, which may be formed, for example, by one or more quantum well structures. When light passes from one refractive index layer to the other, a portion of the light is reflected, creating a diffractive Bragg reflector (DBR) structure. With a sufficient number of alternating layers, a high percentage of the light is reflected, creating a standing wave pattern throughout the cavity. Summary of the Invention

[0004] A laser having a two semiconductor composite cavity is shown and / or described with reference to at least one of the drawings and more fully described in the claims.

[0004] These and other advantages, aspects and novel features of the present disclosure, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings. [Brief description of the drawings]

[0005]

[0005] The various features and advantages of the present disclosure may be more clearly understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters indicate like structural elements and in which: [Figure 1]

[0006] FIG. 2 shows a cross-sectional view of a vertical coupler portion of a laser with a two semiconductor composite cavity. [Diagram 2]

[0007] FIG. 2 shows a plan view of the laser depicted in FIG. 1 with a composite cavity of two semiconductors. [Diagram 3]

[0008] FIG. 2 shows a side view of the laser depicted in FIG. 1 with a two semiconductor composite cavity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006]

[0009] The following description illustrates various aspects of the disclosure by providing examples of the disclosure. Such examples are non-limiting, and therefore the scope of various aspects of the disclosure should not be limited by any particular features of the examples provided. In the following description, the phrases "for example" and "exemplary" are non-limiting and generally synonymous with "for example, and not limited to this example," "for example, and not limited to," and the like.

[0007]

[0010] As used herein, "and / or" means any one or more of the items in the list connected by "and / or." For example, "x and / or y" means any one or more of the three element set {(x), (y), (x, y)}. As another example, "x, y, and / or z" means any element of the seven element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z."

[0008]

[0011] The terms used herein are for the purpose of describing specific examples only and are not intended to limit the disclosure. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise. It is further understood that as used in this specification, the terms "comprises," "includes," "comprises," "includes," "has," "having," and the like specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0009]

[0012] In the present specification, terms such as first, second, etc. may be used to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, for example, a first element, first component, or first portion described below can be referred to as a second element, second component, or second portion without departing from the teachings of the present disclosure. Similarly, various spatial terms such as "top", "bottom", "side", etc. may be used to distinguish one element from another in a relative manner. However, it should be understood that components can be oriented in different ways. For example, a semiconductor device or package can be oriented on its side so that its "top" surface faces horizontally and its "side" surface faces vertically without departing from the teachings of the present disclosure.

[0010]

[0013] In the drawings, thicknesses or sizes of layers, regions and / or components may be exaggerated for clarity. Thus, the scope of this disclosure should not be limited by such thicknesses or sizes. Additionally, in the drawings, like reference numerals may refer to like elements throughout the discussion. Numbered elements with an apostrophe (') may be similar to correspondingly numbered elements without the apostrophe.

[0011]

[0014] Unless otherwise noted, the term "coupled" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements. For example, if element A is coupled to element B, element A may be in direct contact with element B or indirectly connected to element B by an intervening element C. Similarly, the terms "over" or "on" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements.

[0012]

[0015] Composite cavity lasers (CCLs) include a composite laser cavity consisting of a cavity from two semiconductor materials. CCLs can be fabricated using a pair of two semiconductor structures, where the upper part of the cavity is formed through a superstructure comprising a semiconductor material with a narrow band gap energy (e.g., GaAs or InP) and the lower part of the cavity is formed through a substructure comprising a semiconductor material with a wide band gap energy (e.g., SiC, AlN or diamond). The cavity parts can be coupled together through a coupler (e.g., a vertical grating coupler (VGC) or an evanescent taper coupler (ETC)). The upper part of the cavity can provide gain and distributed mirrors (e.g., a grating section forming a distributed feedback structure or a distributed Bragg reflector structure) for the active laser action of the narrow band gap semiconductors. The coupler is connected to the upper part of the cavity via a coupler that ... lower part of the cavity via a coupler that is connected to the upper part of the cavity via a coupler that is connected to the upper part of the cavity via a coupler that is connected to the lower part of the cavity via a coupler that is connected to the upper part of the cavity via a coupler that is connected to the upper part of the cavity via a coupler that is connected to the lower part of the cavity via a coupler that is connected to the upper part of the cavity via a coupler that is connected to the lower part of the cavity via a coupler that is connected to the upper part of the cavity via a coupler that is connected to the lower part of the cavity via a couple The laser light or other optical energy may be guided into the lower portion of the cavity, which may provide a lower loss waveguide to the output facet of the lower structure. The upper laser portion of the CCL may be formed, for example, by one or more quantum well structures.

[0013]

[0016] 1 to 3 depict an embodiment of a laser 10. The laser 10 may be implemented as a composite cavity laser (CCL), in which two semiconductor structures 100, 200 comprising semiconductor materials of different bandgaps are integrated together. In particular, the laser 10 may comprise an upper semiconductor structure 100 providing an upper cavity 110 formed with a first semiconductor material and a lower semiconductor structure 200 providing a lower cavity 210 formed with a second semiconductor material having a wider bandgap than the first semiconductor material.

[0014]

[0017] The upper semiconductor structure 100 may comprise an upper structure upper surface 101, an upper structure lower surface 102, and an upper structure side surface 103 between the upper structure upper surface 101 and the upper structure lower surface 102. Similarly, the lower semiconductor structure 200 may comprise a lower structure upper surface 201, a lower structure lower surface 202, and a lower structure side surface 203 between the lower structure upper surface 201 and the lower structure lower surface 202.

[0015]

[0018] The upper cavity 110 of the upper semiconductor structure 100 may be formed from a first semiconductor material or a first semiconductor substrate having a first bandgap. The lower cavity 210 of the lower semiconductor structure 200 may be formed from a second semiconductor material or a second semiconductor substrate having a second bandgap that is larger or wider than the first bandgap. Due to such difference in bandgaps, the upper semiconductor structure 100 may be referred to herein as a narrow bandgap (NBG) structure 100 and the lower semiconductor structure 200 may be referred to herein as a wide bandgap (WBG) structure 200. In operation, the NBG structure 100 may provide gain, laser processing and vertical coupling functions. The WBG structure 200 may provide cooling, waveguiding and photonic functions.

[0016]

[0019] As shown, the NBG structure 100 may comprise an upper waveguide 120 along a lower surface 102 of the NBG structure 100. The upper waveguide 120 may comprise one or more laser structures, such as a distributed Bragg reflector (DBR) structure or a distributed feedback (DFB) structure. As depicted, the upper waveguide 120 comprises a DBR structure 130 between a first contact 140 (e.g., an n-contact) and a second contact 150 (e.g., a p-contact). The upper waveguide 120 of the NBG structure 100 may further comprise a DFB structure 160 between the DBR structure 130 of the upper waveguide 120 and a coupler 170. The NBG structure 100 may further comprise a dielectric 180 encapsulating the upper waveguide 120 and the contacts 140, 150. As shown, the dielectric 180 may provide and / or define the upper surface 101 of the upper structure and the side surface 103 of the upper structure.

[0017]

[0020] The WBG structure 200 may include a lower waveguide 220 along a top surface of the WBG structure 200. The lower waveguide 220 may be buried within a top surface of the lower semiconductor structure 200. The WBG structure 200 may also include an optional DBR structure 230 between the lower waveguide 220 and an output facet 240 of the WBG structure 200.

[0018]

[0021] As shown, the lower surface 102 of the upper structure may be coupled to, formed on, or engaged with the upper surface 201 of the lower structure. Additionally, the upper waveguide 120 may be positioned above the lower waveguide 220 of the WBG structure 200 such that the first portion 190 of the upper waveguide 120 vertically overlaps the second portion 290 of the lower waveguide 220.

[0019]

[0022] The coupler 170 is incorporated within the overlapping portion of the upper waveguide 120 and the lower waveguide 220. The WBG structure 200 may include a first portion 190 of the upper waveguide 120 and a second portion 290 of the lower waveguide 220. The coupler 170 may be embedded in and / or positioned between the overlapping portions 190, 290 of the upper waveguide 120 and the lower waveguide 220. The coupler 170 may couple laser light and / or other optical energy from the first portion 190 of the upper waveguide 120 to the second portion 290 of the lower waveguide 220 of the WBG structure 200.

[0020]

[0023] To this end, the coupler 170 may include a vertical grating coupler (VGC) on one or more surfaces of the upper waveguide 120. The VGC may include a vertical grating that couples the optical energy of the upper waveguide 120 to the lower waveguide 220 via the overlapping portions 190, 290 of the upper and lower waveguides 120, 220. Alternatively, the coupler 170 may include an evanescent taper coupler (ETC) in one or more tapered portions 190, 290 of the upper and / or lower waveguides 120, 220. The ETC may couple the optical energy of the upper waveguide 120 to the lower waveguide 220 without the aid of a grating. Nevertheless, the coupler 170 (e.g., a VGC or ETC) may function as an intracavity optical coupler between the upper waveguide 120 of the NBG structure 100 and the lower waveguide 220 of the WBG structure 200. In this manner, the laser 10 of FIGS. 1-3 may form a composite laser cavity having an upper cavity 110 and a lower cavity 210 formed from semiconductors having different bandgaps.

[0021]

[0024] As mentioned above, the upper cavity 110 may be implemented by a semiconductor material having a narrower bandgap than the semiconductor material used to implement the lower cavity 210. In particular, the upper cavity 110 may be implemented by a narrow bandgap semiconductor material, such as InP, GaAs, or associated quantum wells with alloy layers. For example, the upper cavity 110 may be implemented by a semiconductor material having a bandgap of about 1.34 eV, about 1.42 eV, less than 2 eV, less than 3 eV, or within a range between any two of the above values. In various embodiments, the upper cavity 110, the DBR structure 130, the DFB structure 160, and the coupler 170 may be implemented in a manner similar to a typical semiconductor laser structure, except that they have a very thin lower cladding layer thickness (e.g., less than 1 micron). The very thin lower cladding layer thickness can efficiently transfer heat to the lower semiconductor structure 200, which may exhibit a higher thermal conductivity.

[0022]

[0025] In various embodiments, the WBG structure 200 and its lower cavity 210 may be implemented with a wide bandgap semiconductor material or substrate, such as SiC, AlN, diamond, etc. For example, the WBG structure 200 may be implemented with a semiconductor material having a bandgap of about 3 eV, about 3.3 eV, about 5.47, about 6.2, greater than 3 eV, greater than 5 eV, greater than 6 eV, or within a range between any two of the above values. The lower waveguide 220 of the WBG structure 200 may guide laser light or other optical energy from the upper waveguide 120 of the NBG structure 100 to an output facet 240 of the lower semiconductor structure 200.

[0023]

[0026] The WBG structure 200 may establish a composite laser cavity through its own coupler or the coupler 170 of the NBG structure 100 with a partially reflective output facet. Furthermore, the WBG structure 200 may provide better thermal removal of heat from the NBG structure 100 for higher optical output and efficiency. The lower waveguide 220 of the WBG structure 200 may provide a lower refractive index than that of the upper waveguide 120. The lower refractive index may provide a larger optical mode at the output facet 240 and may allow for lower loss coupling with an external optical fiber compared to the upper waveguide 120. The lower refractive index of the lower waveguide 220 may also increase reliability at high optical output at the output facet 240 with less optical damage generated by the reduced density. The lower waveguide 220 of the WBG structure 200 may also provide an optical output coupler that combines different emission wavelengths from multiple NBG structures 100 to form a multi-color laser emitter.

[0024]

[0027] Although the present disclosure includes references to specific examples, those skilled in the art will recognize that various changes may be made and equivalents may be substituted without departing from the scope of the disclosure. Additionally, modifications may be made to the disclosed examples without departing from the scope of the disclosure. Therefore, it is not intended that the disclosure be limited to the disclosed examples, but rather that the disclosure include all examples that fall within the scope of the appended claims. [Explanation of symbols]

[0025] 10 Laser 100 Upper semiconductor structure, NBG structure 101 Upper surface of superstructure 102 Underside of superstructure 103 Side of the Superstructure 110 Upper Cavity 120 Upper waveguide 130 DBR structure 140 First Contact 150 Second Contact 160 DFB structure 170 Combiner 180 Dielectric 190 overlapping portion, first portion, tapered portion 200 Lower semiconductor structure, WBG structure 201 Upper surface of substructure 202 Underside of substructure 203 Side of the Substructure 210 Lower Cavity 220 Lower Waveguide 230 DBR structure 240 Output Facets 290 overlapping portion, second portion, tapered portion

Claims

1. an upper semiconductor substrate having an upper semiconductor substrate upper surface and an upper semiconductor substrate lower surface; a lower semiconductor substrate having a lower semiconductor substrate upper surface and a lower semiconductor substrate lower surface; a composite laser cavity including an upper cavity in the upper semiconductor substrate, a lower cavity in the lower semiconductor substrate, and a coupler for coupling laser light between the upper cavity and the lower cavity; 1. A laser comprising: the upper semiconductor substrate has a first bandgap; the lower semiconductor substrate has a second bandgap wider than the first bandgap; a lowermost surface of the upper semiconductor substrate overlies an uppermost surface of the lower semiconductor substrate; laser.

2. 10. The laser of claim 1, wherein the upper cavity of the composite laser cavity comprises a distributed feedback (DFB) structure.

3. 3. The laser of claim 2, wherein the upper cavity of the composite laser cavity includes a distributed Bragg reflector (DBR) structure.

4. 10. The laser of claim 1, wherein the lower cavity of the composite laser cavity includes a distributed Bragg reflector (DBR) structure.

5. 10. The laser of claim 1, wherein the lower cavity outputs laser light from an output facet of the lower semiconductor substrate.

6. 10. The laser of claim 1, the lower semiconductor substrate has a side surface between the upper surface of the lower semiconductor substrate and the lower surface of the lower semiconductor substrate, the lower cavity outputs laser light from an output facet along the side of the lower semiconductor substrate. laser.

7. 10. The laser of claim 1, wherein the upper cavity partially overlaps the lower cavity.

8. 8. The laser of claim 7, wherein the coupler comprises a vertical grating, the vertical grating coupling laser light between overlapping portions of the upper and lower cavities.

9. 8. The laser of claim 7, wherein the coupler comprises an evanescent tapered coupler that couples laser light between overlapping portions of the upper and lower cavities.

10. 10. The laser of claim 1, wherein the upper semiconductor substrate lower surface is physically coupled to the lower semiconductor substrate upper surface.

11. 10. The laser of claim 1, the first band gap is less than 2 eV; the second band gap is greater than 3 eV; laser.

12. 10. The laser of claim 1, the first band gap is between 1.34 eV and 2 eV; the second band gap is between 3 eV and 6 eV; laser.

13. 10. The laser of claim 1, wherein the lower cavity of the composite laser cavity has a lower refractive index than the upper cavity of the composite laser cavity.

14. 10. The laser of claim 1 wherein the upper cavity lower cladding layer is less than 1 micron thick.

15. 15. The laser of claim 14, wherein the lower cladding layer is physically bonded to the upper surface of the lower semiconductor substrate.

16. 16. The laser of claim 15, wherein the lower semiconductor substrate exhibits a higher thermal conductivity than the upper semiconductor substrate.

Images