Edge emitting laser and method of manufacturing the same

Abstract

This disclosure provides a side-emitting laser and its fabrication method, which can be applied in the field of optoelectronic devices. The side-emitting laser includes: an N-plane metal electrode disposed on a substrate of the side-emitting laser; a resonant cavity disposed on the N-plane metal electrode; and a P-plane metal electrode disposed on the resonant cavity. The P-plane metal electrode includes: a first gain grating disposed at a first end of the P-plane metal electrode; and a second gain grating disposed at a second end of the P-plane metal electrode opposite to the first end. The resonant cavity includes multiple semiconductor layers, each including a refractive index grating layer. The grating periods of the refractive index grating layer, the first gain grating, and the second gain grating are the same. The refractive index grating layer is used to select the mode of the resonant light to obtain mode light. The refractive index grating layer is also used to combine the first gain grating and the second gain grating to increase the mode light, so that the resonant cavity generates laser light with a linewidth less than 10 kHz.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor laser technology, and in particular to a side-emitting laser and its fabrication method. Background Technology

[0002] With the continuous development of science and technology, people have increasingly higher requirements for the transmission rate, sensitivity, and capacity of communication. To meet these demands, it is necessary to continuously narrow the laser linewidth. Narrow-linewidth lasers are widely used in fields such as coherent laser communication, laser sensing, space laser communication, precision measurement, and spectroscopy, where high requirements are placed on laser linewidth and phase noise. A narrower laser linewidth corresponds to a lower noise level, which makes the modulation process clearer and facilitates laser resolution and identification. Current methods for narrowing the linewidth include using external cavity lasers and distributed feedback Bragg lasers. Summary of the Invention

[0003] In view of the above, this disclosure provides a side-emitting laser and a method for fabricating the same, in order to partially solve at least one of the aforementioned technical problems.

[0004] According to one aspect of this disclosure, a side-emitting laser is provided.

[0005] The edge-emitting laser includes: an N-face metal electrode disposed on a base plate of the edge-emitting laser; a resonant cavity disposed on the N-face metal electrode; and a P-face metal electrode disposed on the resonant cavity. The P-face metal electrode includes: a first gain grating disposed at a first end of the P-face metal electrode; and a second gain grating disposed at a second end of the P-face metal electrode opposite to the first end. The resonant cavity includes multiple semiconductor layers, each of which includes at least one refractive index grating layer. The grating periods of the refractive index grating layer, the first gain grating, and the second gain grating are the same. The refractive index grating layer is used to select the mode of the resonant light to obtain mode light. The refractive index grating layer is also used to combine the first gain grating and the second gain grating to amplify the mode light, so that the resonant cavity generates a laser with a linewidth of less than 10 kHz based on the amplified mode light. The resonant light is the light emitted when the excitation light resonates in the resonant cavity, and the excitation light is obtained by the resonant cavity based on an external current.

[0006] According to embodiments of this disclosure, the refractive index grating layer is further configured to: when a first current is injected into the resonant cavity at the positions of the first gain grating and the second gain grating, in conjunction with the first gain grating, inject the first current into the high refractive index portion of the refractive index grating corresponding to the first gain grating, so that the high refractive index portion corresponding to the first gain grating gains the mode light; and in conjunction with the second gain grating, inject the first current into the high refractive index portion of the refractive index grating corresponding to the second gain grating, so that the high refractive index portion corresponding to the second gain grating gains the mode light, wherein the high refractive index portion of the refractive index grating appears periodically on the refractive index grating.

[0007] According to an embodiment of this disclosure, the side-emitting laser further includes a second current injection window disposed between the first gain grating and the second gain grating; the side-emitting laser is configured such that when the second current injection window injects a second current into the resonant cavity, the second current is injected at a 1 / 4 wavelength phase shift of the refractive index grating layer; the 1 / 4 wavelength phase shift of the refractive index grating layer is determined according to the grating parameters of the refractive index grating layer.

[0008] According to embodiments of this disclosure, the semiconductor layer further includes: a substrate, an N-type confinement layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type confinement layer, a contact layer, an isolation layer, and the refractive index grating layer; the substrate, the N-type confinement layer, the N-type waveguide layer, the active layer, the P-type waveguide layer, and the refractive index grating layer are planar thin film layers grown sequentially from the N-plane metal electrode to the P-plane metal electrode; the P-type confinement layer is a three-dimensional thin film layer with protrusions and non-protrusions grown on the refractive index grating layer, and the cross-section obtained by cutting along the direction of the wide side of the edge-emitting laser is convex, the wide side of the edge-emitting laser is perpendicular to the growth direction, and the shorter side of the edge-emitting laser is present; the isolation layer is grown on the non-protrusion portion of the P-type confinement layer, and the contact layer and the isolation layer are grown sequentially on the protrusion portion of the P-type confinement layer, wherein the isolation layer on the non-protrusion portion of the P-type confinement layer is not in contact with the contact layer.

[0009] According to an embodiment of this disclosure, the refractive index grating layer includes: a refractive index grating bottom layer, a refractive index grating etched layer, and a refractive index grating capping layer; the refractive index grating bottom layer is a planar thin film layer disposed on a P-type waveguide layer; the refractive index grating etched layer is a three-dimensional thin film layer with protrusions and non-protrusions disposed on the refractive index grating bottom layer, and the protrusions and non-protrusions of the refractive index grating etched layer are periodically alternated along the direction of the long side of the edge-emitting laser, the long side of the edge-emitting laser is perpendicular to the growth direction, and the longer side of the edge-emitting laser is the longer side; the refractive index grating capping layer is a three-dimensional thin film layer with protrusions and non-protrusions disposed on the refractive index grating etched layer, and the protrusions of the refractive index grating capping layer are embedded in the non-protrusions of the refractive index grating etched layer, and the protrusions of the refractive index grating capping layer are embedded in the protrusions of the refractive index grating etched layer.

[0010] According to an embodiment of this disclosure, the doping concentration of the substrate is greater than the doping concentration of the N-type waveguide; wherein, the N-type confinement layer is used to reduce the absorption loss of free carriers in the side-emitting laser, and the free carriers are particles that move freely in the conduction band or valence band of the resonant cavity due to doping.

[0011] According to an embodiment of this disclosure, the first gain grating, the second gain grating, and the second current injection window are disposed on the P-surface metal electrode corresponding to the protrusion of the P-type confinement layer along the direction of the long side of the edge-emitting laser. The long side of the edge-emitting laser is perpendicular to the growth direction, and the edge-emitting laser is the longer side.

[0012] According to an embodiment of this disclosure, the first gain grating has periodically arranged protrusions, and the protrusions of the first gain grating correspond one-to-one with the protrusions of the refractive index grating etching layer in the growth direction; the second gain grating has periodically arranged protrusions, and the protrusions of the second gain grating correspond one-to-one with the protrusions of the refractive index grating etching layer in the growth direction.

[0013] According to another aspect of this disclosure, a method for fabricating a side-emitting laser is provided.

[0014] The fabrication method includes: sequentially growing a substrate, an N-type confinement layer, an N-type waveguide layer, an active layer, and a P-type waveguide layer using metal-organic chemical vapor deposition (MOCVD); growing a refractive index grating layer on the P-type waveguide layer, the refractive index grating layer comprising a refractive index grating bottom layer, a refractive index grating etched layer, and a refractive index grating cap layer; growing the refractive index grating bottom layer and the refractive index grating etched layer on the P-type waveguide layer using MOCVD; etching equally spaced grating grooves on the refractive index grating etched layer using photolithography to obtain a refractive index grating structure; growing the refractive index grating cap layer on the refractive index grating etched layer using MOCVD; and growing the refractive index grating layer on the refractive index grating layer using MOCVD. A P-type confinement layer and a contact layer are grown in the next step. Using photolithography, both sides of the P-type confinement layer and the contact layer are etched along the growth direction to obtain a P-type confinement layer with a convex cross-section in the direction parallel to the grating groove. The contact layer is grown on the protrusion of the P-type confinement layer. An isolation layer is grown on the P-type confinement layer and the contact layer using plasma-enhanced chemical vapor deposition. An electrode pattern is etched on the isolation layer using photolithography. A P-side metal electrode is obtained based on the electrode pattern using electroplating. An N-side metal electrode is grown on the side of the substrate away from the N-type confinement layer using electroplating to obtain a multilayer structure. The multilayer structure is then cleaved to obtain the edge-emitting laser of a predetermined size.

[0015] According to embodiments of this disclosure, obtaining a P-side metal electrode based on an electrode pattern includes: simultaneously growing a first P-side metal electrode layer and a second P-side metal electrode layer on the electrode pattern using an electroplating method.

[0016] According to embodiments of this disclosure, by using a first gain grating and a second gain grating, both periodically aligned with the refractive index grating, disposed at both ends of the P-plane metal electrode, current is injected into the high-refractive-index portion of the refractive index grating while current is not injected into the low-refractive-index portion. This improves the carrier concentration contrast between the high and low refractive-index portions of the grating, increases the coupling factor, and thereby improves the reflectivity of the edge-emitting laser. Consequently, the laser output power is increased, and the increased output power further reduces the linewidth. Based on the above technical means, the problem of wide linewidth in existing semiconductor lasers is at least partially overcome, achieving a reduction in linewidth. Attached Figure Description

[0017] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of the structure of a side-emitting laser according to an embodiment of the present disclosure is shown.

[0019] Figure 2 The diagram schematically illustrates a front view cross-section of an edge-emitting laser according to an embodiment of the present disclosure.

[0020] Figure 3 The diagram schematically illustrates a left-side cross-section of an edge-emitting laser according to an embodiment of the present disclosure.

[0021] Figure 4 A flowchart illustrating a method for fabricating a side-emitting laser according to an embodiment of the present disclosure is shown.

[0022] 1-N surface metal electrodes;

[0023] 2-Substrate;

[0024] 3-N type doped confinement layer;

[0025] 4-Undoped confinement layer;

[0026] 5-N type waveguide layer;

[0027] 6-Active Layer;

[0028] 7-P type waveguide layer;

[0029] 8-Refractive index grating layer;

[0030] 9-P type confinement layer;

[0031] 10 - Contact layer;

[0032] 11-Isolation layer;

[0033] 12-P surface metal electrode;

[0034] 13-Resonant cavity. Detailed Implementation

[0035] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0036] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0037] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0038] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0039] In realizing the concept of this disclosure, the inventors discovered at least the following problems in the related technology:

[0040] Current methods for narrowing linewidth include using external cavity lasers and using distributed feedback Bragg lasers.

[0041] When narrowing the linewidth using an external cavity laser, the external cavity laser is required to provide the laser energy. However, the volume gratings and blazed gratings that make up an external cavity laser are relatively expensive, and their large size and complex structure make them difficult to integrate. Distributed feedback Bragg lasers, on the other hand, have a large laser linewidth, which reduces laser quality.

[0042] When single-mode output is achieved using a distributed feedback Bragg laser, multi-longitudinal-mode oscillations occur within the laser cavity. When these longitudinal modes oscillate stably within the cavity, standing waves are generated. These standing waves are relatively stationary with respect to the resonant cavity medium. Particles are consumed at antinodes but remain at nodes, resulting in spatial longitudinal non-uniformity in the intensity distribution within the cavity. As pump power increases, the spatial hole-burning effect leads to multi-longitudinal-mode oscillations, broadening the output laser linewidth. Specifically, the spatial hole-burning effect occurs at the 1 / 4 phase shift position corresponding to the distributed feedback Bragg laser grating, increasing the laser linewidth and reducing laser quality.

[0043] In order to at least partially solve the technical problems existing in the related technologies, this disclosure provides a side-emitting laser and a method for fabricating the same, which can be applied to the field of semiconductor laser technology.

[0044] Figure 1 A schematic diagram of the structure of a side-emitting laser according to an embodiment of the present disclosure is shown.

[0045] like Figure 1 As shown, the edge-emitting laser 100 may include: an N-plane metal electrode 1, a resonant cavity 13, and a P-plane metal electrode 12.

[0046] The N-face metal electrode 1 is disposed on the base plate of the edge-emitting laser 100.

[0047] The resonant cavity 13 is disposed on the N-side metal electrode 1.

[0048] The P-side metal electrode 12 is disposed on the resonant cavity 13.

[0049] The P-plane metal electrode 12 may include: a first gain grating disposed at a first end of the P-plane metal electrode; and a second gain grating disposed at a second end of the P-plane metal electrode, opposite to the first end. The resonant cavity 13 includes multiple semiconductor layers, each including at least one refractive index grating layer. The grating periods of the refractive index grating layer, the first gain grating, and the second gain grating are the same. The refractive index grating layer is used to select the mode of the resonant light to obtain mode light. The refractive index grating layer is also used to combine the first gain grating and the second gain grating to amplify the mode light, so that the resonant cavity 13 generates laser light with a linewidth less than 10 kHz based on the amplified mode light. The resonant light is the light emitted when the excitation light resonates in the resonant cavity 13, and the excitation light is obtained by the resonant cavity 13 based on an external current.

[0050] According to embodiments of this disclosure, the refractive index grating layer may include a refractive index grating, which may be composed of alternating high refractive index positions and low refractive index positions. Thus, the refractive index grating can reflect light waves of a specific wavelength that match the refractive index grating, based on the refractive index differences of different wavelengths, for a series of light waves of different wavelengths.

[0051] According to embodiments of this disclosure, the refractive index values ​​of the high and low refractive index positions of the refractive index grating, as well as the structural parameters of the high and low refractive index positions of the refractive index grating, can be adjusted to achieve the adjustment of the structural parameters of the refractive index grating, such as the grating period and the refractive index modulation depth, so as to enable the refractive index grating to select light waves of different wavelengths. The embodiments of this disclosure are not limited herein.

[0052] According to embodiments of this disclosure, the first gain grating and the second gain grating can be configured as gratings with structural parameters such as the period and refractive index modulation depth of the refractive index grating, so that the first gain grating and the second gain grating can be matched with the refractive index grating, thereby achieving selective gain of light waves of a specific wavelength by the first gain grating and the second gain grating. The light wave of the specific wavelength can be a wavelength matched with the refractive index grating, and the selective gain can be the gain of energy of the light wave of the specific wavelength performed at the high refractive index position of the refractive index grating by matching the first gain grating and the second gain grating with the refractive index grating.

[0053] According to embodiments of this disclosure, after adding a first gain grating and a second gain grating, the positions of the first gain grating and the second gain grating relative to the refractive index grating can be adjusted to align the high refractive index positions of the first gain grating and the refractive index grating, as well as the high refractive index positions of the second gain grating and the refractive index grating. This allows the resonant light to oscillate back and forth through the refractive index grating within the resonant cavity. Additionally, the coupling coefficient of light waves of a specific wavelength in the high reflectivity portion of the refractive index grating can be increased by using the first gain grating and the second gain grating disposed on both sides of the P-plane metal electrode.

[0054] According to embodiments of this disclosure, a current can be applied to the resonant cavity 13 through the N-side metal electrode 1 and the P-side metal electrode 12. Under the action of the externally injected current, the resonant cavity 13 utilizes a refractive index grating layer to select light waves of a specific wavelength. Furthermore, due to the addition of a first gain grating and a second gain grating to process the light waves of a specific wavelength, the coupling coefficient of the light waves of a specific wavelength at the high refractive index position of the refractive index grating in the refractive index grating layer can be increased. The increase in the coupling coefficient corresponds to an increase in the reflectivity of the light waves of a specific wavelength, thereby improving the output power of the laser corresponding to the light waves of a specific wavelength, thus achieving compression of the laser linewidth of the edge-emitting laser 100.

[0055] According to embodiments of this disclosure, the refractive index grating layer can also be used to: inject a first current into the resonant cavity at the positions of the first gain grating and the second gain grating, in conjunction with the first gain grating, inject the first current into the high refractive index portion of the refractive index grating corresponding to the first gain grating so that the high refractive index portion corresponding to the first gain grating amplifies the mode light; in conjunction with the second gain grating, inject the first current into the high refractive index portion of the refractive index grating corresponding to the second gain grating so that the high refractive index portion corresponding to the second gain grating amplifies the mode light, wherein the high refractive index portion of the refractive index grating appears periodically on the refractive index grating.

[0056] According to embodiments of this disclosure, when a first gain grating is disposed at the first end of a P-plane metal electrode and a second gain grating is disposed at the second end of a P-plane metal electrode opposite to the first end of the P-plane metal electrode, a first current can be injected into both the first and second gain gratings simultaneously. Since the high refractive index positions of the first gain grating and the refractive index grating, and the high refractive index positions of the second gain grating and the refractive index grating can be aligned, the first current can be injected into the high refractive index position of the refractive index grating between the first gain grating and the refractive index grating, and vice versa. This achieves energy gain for light waves of a specific wavelength by matching the first and second gain gratings with the refractive index grating and processing them at the high refractive index position of the refractive index grating.

[0057] According to an embodiment of this disclosure, the side-emitting laser 100 may further include: a second current injection window disposed between the first gain grating and the second gain grating;

[0058] The side-emitting laser 100 can be configured such that, when a second current is injected into the resonant cavity through the second current injection window, the second current is injected at a 1 / 4 wavelength phase shift of the refractive index grating layer; the 1 / 4 wavelength phase shift of the refractive index grating layer is determined according to the grating parameters of the refractive index grating layer.

[0059] According to embodiments of this disclosure, when a specific wavelength of light is selected by the refractive index grating of the refractive index grating layer, ideally, the refractive index grating can reflect only one wavelength of light. However, in practical applications, a spatial hole-burning effect may occur at the 1 / 4 phase shift position corresponding to the refractive index grating. That is, the number of particles at this 1 / 4 phase shift position is small, resulting in untimely charge transfer and causing spatial longitudinal non-uniformity of the light intensity distribution within the cavity. This spatial longitudinal non-uniformity of the light intensity distribution may lead to a decrease in the saturated output power of the side-emitting laser 100 and the occurrence of multi-wavelength lasing, thereby increasing the linewidth of the side-emitting laser 100. The output power of the laser includes the saturated output power.

[0060] According to embodiments of this disclosure, in actual use, the laser wavelength required by the side-emitting laser 100 needs to be matched with relevant instruments. Therefore, the side-emitting laser 100 may only require a few specific wavelengths. Furthermore, the specific structural parameters of the refractive index grating can be adjusted according to the actual needs of the side-emitting laser 100. Thus, even with specific refractive index grating structural parameters, the corresponding 1 / 4 phase shift position of the refractive index grating will have a certain displacement, and the range of the 1 / 4 phase shift position can be determined within the side-emitting laser 100.

[0061] According to embodiments of this disclosure, the situation where a second current is injected into the resonant cavity through the second current injection window can be represented by the following formula (1).

[0062] I2=NeSv (1)

[0063] Where I2 is the second current; N is the number of electrons per unit volume; e is the electron charge; S is the cross-sectional area of ​​the side-emitting laser; and v is the directional movement velocity of the electrons.

[0064] According to embodiments of this disclosure, the spatial hole burning effect caused by untimely charge migration at the 1 / 4 phase shift position corresponding to the refractive index grating can be alleviated by increasing a larger second current, thereby increasing the saturated output power.

[0065] According to the embodiments of this disclosure, the following formula (2) can be used to express that when a first current is injected into the resonant cavity at the positions of the first gain grating and the second gain grating, the first current is injected into the high refractive index portion of the refractive index grating corresponding to the first gain grating in combination with the first gain grating, so that the high refractive index portion corresponding to the first gain grating can gain the mode light.

[0066]

[0067] Where K1 is the coupling coefficient, and the relationship between the coupling coefficient and the real part eigenvalues ​​of the coupling coefficient is as follows: Δn eff The change in the real part of the effective refractive index; i is the imaginary parameter; Δn , eff Change in the imaginary part of the effective refractive index; n eff Λ is the effective refractive index; K is the period of the refractive index grating; K is the real part eigenvalue of the coupling coefficient; K ′ is the imaginary part characteristic of the coupling coefficient.

[0068] According to embodiments of this disclosure, when a first current is injected into the resonant cavity at the positions of the first gain grating and the second gain grating, the imaginary part characteristic of the coupling coefficient increases, thereby increasing the coupling coefficient.

[0069] According to embodiments of this disclosure, the compression of the laser linewidth of the edge-emitting laser can be achieved by adding a first gain grating and a second gain grating using the following formulas (3) and (4).

[0070] Γ=KL (3)

[0071] Where Γ is the reflectivity and L is the cavity length of the resonant cavity.

[0072]

[0073] Where Δv is the linewidth of the edge-emitting laser; α is the linewidth broadening factor; h is Planck's constant; v0 is the resonant frequency; P is the output power; Δv LD The cold cavity linewidth.

[0074] According to embodiments of this disclosure, increasing the coupling coefficient will increase the reflectivity, which in turn can increase the output power of the laser, thereby narrowing the linewidth.

[0075] According to embodiments of this disclosure, the value of the second current can be set to be greater than the value of the first current. When the first current is injected into the resonant cavity at the positions of the first gain grating and the second gain grating, and the second current is injected into the resonant cavity through the second current injection window, the injected second current can increase the number of electrons at the 1 / 4 phase shift position in the resonant cavity, reducing the spatial hole burning effect caused by the untimely migration of electrons. The spatial hole burning effect can be alleviated, which can increase the saturated output power and thus compress the linewidth of the side-emitting laser 100. Furthermore, due to the introduction of the first gain grating and the second gain grating on both sides of the resonant cavity, the coupling coefficient of the side-emitting laser 100 can also be increased, thereby improving the output power of the laser and further compressing the linewidth of the side-emitting laser 100.

[0076] According to embodiments of this disclosure, the first gain grating, the second current injection window, and the second gain grating can be configured to be equally distributed on the P-plane metal electrode 12. However, this is not a limitation. Those skilled in the art can also design the size of the intervals of the first gain grating, the second current injection window, and the second gain grating according to actual needs, so that when a second current is injected into the resonant cavity through the second current injection window, the number of particles at the 1 / 4 phase shift position in the resonant cavity increases. Embodiments of this disclosure do not limit this.

[0077] The following is based on Figure 1 The described edge-emitting laser 100, through Figures 2-3 The side-emitting laser 100 of the present disclosure will be described in detail.

[0078] Figure 2 The diagram schematically illustrates a front view cross-section of an edge-emitting laser according to an embodiment of the present disclosure.

[0079] Figure 3 The diagram schematically illustrates a left-side cross-section of an edge-emitting laser according to an embodiment of the present disclosure.

[0080] like Figure 2As shown, the edge-emitting laser 100 may include: an N-face metal electrode 1, a substrate 2, an N-type doped confinement layer 3, an undoped confinement layer 4, an N-type waveguide layer 5, an active layer 6, a P-type waveguide layer 7, a refractive index grating layer 8, a P-type confinement layer 9, a contact layer 10, an isolation layer 11, and a P-face metal electrode 12. The N-face metal electrode 1 can be positioned below the edge-emitting laser 100, with the direction from the N-face metal electrode 1 to the P-face metal electrode 12 being upward.

[0081] According to embodiments of this disclosure, the substrate 2, the N-type doped confinement layer 3, the undoped confinement layer 4, the N-type waveguide layer 5, the active layer 6, the P-type waveguide layer 7, the refractive index grating layer 8, the P-type confinement layer 9, the contact layer 10, and the isolation layer 11 are semiconductor layers included in the resonant cavity 13.

[0082] According to embodiments of this disclosure, the material of the N-side metal electrode 1 can be a single metal material composed of any one of Au, Ge, Ni and Au, or a mixed metal material composed of the above elements.

[0083] According to embodiments of this disclosure, substrate 2 can be a highly doped substrate, specifically an N-type doped GaAs substrate, so that a better ohmic contact can be formed between substrate 2 and N-plane metal electrode 1, thereby achieving an effective transition between metal materials and semiconductor materials.

[0084] According to the embodiments of this disclosure, the specific value of the doping concentration of substrate 2 can be adjusted by those skilled in the art according to actual needs, and the embodiments of this disclosure do not limit this. The specific values ​​of the doping concentration corresponding to other semiconductor layers appearing in the embodiments of this disclosure can also be described based on this, and will not be repeated hereafter.

[0085] According to embodiments of this disclosure, the material of the N-type doped confinement layer 3 can be Al x Ga 1-x In an N-type doped material composed of As, where x is a positive number less than 1, the sum of x and the two components corresponding to 1-x (here referring to the Al component corresponding to x and the Ga component corresponding to 1-x) must always be 1. Those skilled in the art can adjust the specific values ​​of the components according to actual needs, and the embodiments of this disclosure do not limit this. Furthermore, the components corresponding to "x" (i.e., "1-x") appearing in the embodiments of this disclosure can all be explained based on this, and will not be elaborated further thereafter.

[0086] According to embodiments of this disclosure, the undoped confinement layer 4 can be made of Al x Ga 1-x An undoped material composed of As. Through an N-face metal electrode 1 of metallic material, a highly doped substrate 2, an N-type doped confinement layer 3, and an undoped confinement layer 4, an effective transition between metallic and semiconductor materials is further achieved.

[0087] According to embodiments of this disclosure, the N-type waveguide layer 5 can be an undoped material made of GaAs.

[0088] According to embodiments of this disclosure, the doping concentration of the substrate is greater than the doping concentration of the N-type doped confinement layer. The N-type doped confinement layer is used to reduce the absorption loss of free carriers in the edge-emitting laser 100. Free carriers are particles generated by doping in the resonant cavity that move freely within the conduction or valence band of the resonant cavity.

[0089] According to the embodiments of this disclosure, the undoped confinement layer 4 and the N-type waveguide layer 5 may not be doped. After passing through the structural layers of substrate 2, N-type doped confinement layer 3, undoped confinement layer 4 and N-type waveguide layer 5, the doping concentration gradually decreases to no doping. The reduction in doping concentration can reduce the absorption loss of free carriers, which is beneficial to improving the output power of the side-emitting laser 100.

[0090] According to embodiments of this disclosure, the active layer 6 can be a double quantum well structure, or a double barrier structure. The double quantum well structure comprises two barrier layers on either side and a well layer between the barrier layers. The barrier layers can be made of In... x Ga 1-x The material is composed of As, and the well layer can be composed of GaAs.

[0091] According to embodiments of this disclosure, the P-type waveguide layer 7 can also be an undoped material composed of GaAs.

[0092] According to embodiments of this disclosure, the refractive index grating layer may include: a refractive index grating bottom layer, a refractive index grating etched layer, and a refractive index grating capping layer.

[0093] According to embodiments of this disclosure, the refractive index grating bottom layer is a planar thin film layer disposed on a P-type waveguide layer. The refractive index grating etched layer is a three-dimensional thin film layer with protrusions and non-protrusions disposed on the refractive index grating bottom layer, wherein the protrusions and non-protrusions of the refractive index grating etched layer are periodically alternated along the direction of the long side of the edge-emitting laser, the long side of the edge-emitting laser being perpendicular to the growth direction, and the longer side of the edge-emitting laser being the longer side. The refractive index grating capping layer is a three-dimensional thin film layer with protrusions and non-protrusions disposed on the refractive index grating etched layer, wherein the protrusions of the refractive index grating capping layer are embedded in the non-protrusions of the refractive index grating etched layer, and the protrusions of the refractive index grating capping layer are embedded in the refractive index grating etched layer.

[0094] According to embodiments of this disclosure, the refractive index grating bottom layer and the refractive index grating top layer can be doped materials composed of GaAs; the refractive index grating etching layer can be composed of In... x Ga 1-x Doped materials composed of phosphorus (P).

[0095] According to embodiments of this disclosure, in Figure 2 In the schematic diagram of the front view cross-section of the edge-emitting laser 100 shown, a fracture occurs in the P-plane metal electrode 12, which can be caused by... Figure 3 The schematic diagram of the left-side cross-section of the side-emitting laser shown supplements the structure.

[0096] like Figure 3 As shown, the substrate 2, N-type doped confinement layer 3, undoped confinement layer 4, N-type waveguide layer 5, active layer 6, P-type waveguide layer 7, and refractive index grating layer 8 of the resonant cavity 13 are planar thin film layers grown sequentially from the substrate 2 to the refractive index grating layer 8, i.e., in the upward direction. After the resonant cavity 13 is fabricated, the P-plane metal electrode 12 and the N-plane metal electrode 1 are formed. The P-type confinement layer 9 is a three-dimensional thin film layer with protrusions and non-protrusions grown on the refractive index grating layer 8, and its cross-section along the wide side of the edge-emitting laser is convex. An isolation layer 11 is directly grown on the non-protrusion portion of the P-type confinement layer 9, and a contact layer 10 and an isolation layer 11 are sequentially grown on the protrusion portion of the P-type confinement layer 9. The isolation layer 11 on the non-protrusion portion of the P-type confinement layer 9 can be in contact with the contact layer 11. Therefore, it is possible to obtain... Figure 2 The schematic diagram of the front view cross section of the side-emitting laser shown shows the fault P-plane metal electrode 12.

[0097] According to embodiments of this disclosure, based on Figure 2 The schematic diagram of the front view cross section of the side-emitting laser shown is as follows: Figure 3 The schematic diagram shown is a left-side cross-section of the side-emitting laser, which can be configured... Figure 2 The upward-facing side shown in the cross-section of the front view of the edge-emitting laser is the high side characterizing the thickness of the edge-emitting laser. It can also be set... Figure 2 The side perpendicular to the height shown in the cross-section of the front view of the edge-emitting laser is the long side of the laser. Figure 3 In the schematic diagram of the left cross-section of the edge-emitting laser shown, the side perpendicular to the height side is the wide side. The wide side of the edge-emitting laser is perpendicular to the growth direction and is shorter than the long side of the edge-emitting laser.

[0098] According to embodiments of this disclosure, the protrusion height of the protrusion of the P-type confinement layer 9 can be set to be higher than the thickness of the isolation layer 11 and the P-surface metal electrode 12 on the non-protrusion of the P-type confinement layer 9.

[0099] According to embodiments of this disclosure, the P-type confinement layer 9 can be made of Al x Ga 1-x P-type doped materials composed of As.

[0100] According to embodiments of this disclosure, the contact layer 10 may be a P-type doped material composed of GaAs.

[0101] According to embodiments of this disclosure, the isolation layer 11 may be an undoped material composed of SiO2.

[0102] According to embodiments of this disclosure, the first gain grating, the second gain grating, and the second current injection window can be disposed on the P-surface metal electrode 12 corresponding to the protrusion of the P-type confinement layer 9 along the direction of the long side of the edge-emitting laser.

[0103] According to embodiments of this disclosure, a first gain grating has periodically arranged protrusions, and the protrusions of the first gain grating correspond one-to-one with the protrusions of the refractive index grating etching layer in the growth direction; a second gain grating has periodically arranged protrusions, and the protrusions of the second gain grating correspond one-to-one with the protrusions of the refractive index grating etching layer in the growth direction.

[0104] According to embodiments of this disclosure, the material of the P-side metal electrode 12, i.e. the first gain grating and the second gain grating on the P-side metal electrode 12, can be a single metal material composed of any one of Ti, Pt and Au, or a mixed metal material composed of the above elements.

[0105] According to embodiments of this disclosure, an isolation layer 11 may be provided between the first gain grating, the second gain grating, and the P-plane metal electrode 12, so that when the first current is injected, photons are selectively injected into the high refractive index portion of the refractive index grating, thereby increasing the carrier concentration contrast between the high and low refractive index regions of the refractive index grating.

[0106] Figure 4 A flowchart illustrating a method for fabricating a side-emitting laser according to an embodiment of the present disclosure is shown.

[0107] like Figure 4 As shown, the method 400 for fabricating a side-emitting laser may include operations S410 to S490.

[0108] In operation of S410, a substrate, an N-type doped confinement layer, an N-type waveguide layer, an active layer, and a P-type waveguide layer are grown sequentially using metal-organic chemical vapor deposition.

[0109] In operation S420, a refractive index grating layer is grown on the P-type waveguide layer. The refractive index grating layer includes a refractive index grating bottom layer, a refractive index grating etched layer, and a refractive index grating capping layer.

[0110] According to embodiments of this disclosure, operation S420 may include operations S421 to S423.

[0111] In operation S421, a refractive index grating underlayer and a refractive index grating etching layer are grown on a P-type waveguide layer using metal-organic chemical vapor deposition. In operation S422, equidistant grating grooves are etched on the refractive index grating etching layer using photolithography to obtain a refractive index grating structure. In operation S423, a refractive index grating capping layer is grown on the refractive index grating etching layer using metal-organic chemical vapor deposition.

[0112] In operation of S430, a P-type confinement layer and a contact layer are sequentially grown on the refractive index grating layer using metal-organic chemical vapor deposition.

[0113] By operating the S440 and using photolithography, the two sides of the P-type confinement layer and the contact layer are etched in the growth direction to obtain a P-type confinement layer with a "convex" cross-section in the direction parallel to the grating groove. The contact layer is grown on the protrusion of the P-type confinement layer.

[0114] In operation with S450, an isolation layer is grown on the P-type confinement layer and contact layer using plasma-enhanced chemical vapor deposition.

[0115] When operating the S460, electrode patterns are etched on the isolation layer using photolithography.

[0116] In operation S470, a P-side metal electrode is obtained based on the electrode pattern using electroplating.

[0117] In operation S480, an N-face metal electrode is grown on the side of the substrate away from the N-type confinement layer to obtain a multilayer structure.

[0118] By operating S490, the multi-layer structure is cleaved to obtain an edge-emitting laser of a preset size.

[0119] According to an embodiment of this disclosure, operation S470 may further include: simultaneously growing a first P-side metal electrode layer and a second P-side metal electrode layer on the isolation layer using electroplating; and etching a preset pattern on the protrusion of the P-type confinement layer using photolithography.

[0120] According to embodiments of this disclosure, the following setup can be implemented: an N-plane metal electrode 1 (Au) is deposited on a thinned substrate 2 in the opposite direction to the growth of the semiconductor layer structure via PECVD (Plasma Enhanced Chemical Vapor Deposition). The thickness of the N-plane metal electrode 1 is 300 nm. The substrate 2 is an N-type doped GaAs substrate with a doping concentration of 4 × 10⁻⁶. 18 cm -3 The thickness of substrate 2 after thinning, i.e., the actual thickness of substrate 2 in the edge-emitting laser, is 140-150 μm. The N-type doped confinement layer 3 is Al. 0.26 Ga0.74 As, doping concentration is 2.4 × 10⁻⁶ 18 The 3-cm layer has a thickness of 1800nm. The undoped confinement layer 4 is Al. 0.26 Ga 0.74 The N-type waveguide layer 5 is made of GaAs and has a thickness of 100 nm. The active layer 6 consists of two barrier layers of In0.21Ga0.79As and a well layer of GaAs between them. The gain peak of the active layer 6 is at 1060 nm, and its specific thickness can be determined by the gain peak. The P-type waveguide layer 7 is made of GaAs and has a thickness of 400 nm. The refractive index grating layer 8 includes: a 30 nm GaAs refractive index grating bottom layer and a 100 nm P-type doped In0.21As well as a 100 nm P-type doped In0.79As well. 0.5 Ga 0.5 The refractive index grating etching layer and the 100nm material are both P-type doped GaAs refractive index grating capping layers. The grating is etched on the grating etching layer using a combination of holographic exposure and wet etching. Both the grating etching layer and the refractive index grating capping layer have a doping concentration of 5 × 10⁻⁶. 17 cm -3 P-type confinement layer 9 is Al 0.47 Ga 0.53 As, doping concentration is 1×10 18 cm -3 The thickness is 1800 nm. Contact layer 10 is p-type highly doped GaAs with a doping concentration of 2 × 10⁻⁶. 20 cm -3 The contact layer 10, with a thickness of approximately 150 nm and high doping, facilitates good ohmic contact with the P-side metal electrode. The isolation layer 11, made of SiO2, is approximately 300 nm thick and is located on the contact layer 10 on the protrusion of the P-type confinement layer 9. Grooves are etched at the positions of the first and second gain gratings of the P-side metal electrode 12 down to the contact layer to form a grating structure; grooves are also etched at the position of the second current injection window down to the contact layer to form the second current injection window; the remaining portion is covered by SiO2 to isolate current injection. The P-side metal electrode 12 is made of Ti and is obtained by ion sputtering, with a thickness of 300 nm. The P-side metal electrode 12 can be divided into three parts: the middle part is injected with the second current, and the two sides are injected with the first current.

[0121] According to embodiments of this disclosure, an edge-emitting laser with a long side of 1.5 mm and a short side of 0.55 mm can be obtained through cleaving. Those skilled in the art can also cut edge-emitting lasers with other long and short side values ​​according to actual needs; embodiments of this disclosure do not limit this.

[0122] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features recited in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not expressly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0123] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A side-emitting laser, comprising: N-face metal electrodes are disposed on the base plate of the edge-emitting laser; The resonant cavity is disposed on the N-plane metal electrode; as well as A P-plane metal electrode is disposed on the resonant cavity; The P-plane metal electrode includes: The first gain grating is disposed at the first end of the P-plane metal electrode; The second gain grating is disposed at the second end of the P-plane metal electrode, which is opposite to the first end of the P-plane metal electrode. The resonant cavity includes multiple semiconductor layers, and each of the multiple semiconductor layers includes at least one refractive index grating layer. The grating periods of the refractive index grating layer, the first gain grating, and the second gain grating are the same. The refractive index grating layer is used to select the mode of the resonant light to obtain the mode light; The refractive index grating layer is also used to combine the first gain grating and the second gain grating to amplify the mode light so that the resonant cavity generates a laser with a linewidth of less than 10 kHz based on the amplified mode light. The resonant light is the light when the excitation light resonates in the resonant cavity, and the excitation light is obtained by the resonant cavity based on the external current. The edge-emitting laser, wherein the refractive index grating layer is further used for: When a first current is injected into the resonant cavity at the positions of the first gain grating and the second gain grating, In conjunction with the first gain grating, the first current is injected into the high-refractive-index portion of the refractive index grating corresponding to the first gain grating, so that the high-refractive-index portion corresponding to the first gain grating amplifies the mode light; and In conjunction with the second gain grating, the first current is injected into the high-refractive-index portion of the refractive-index grating corresponding to the second gain grating, so that the high-refractive-index portion corresponding to the second gain grating amplifies the mode light. The high refractive index portion of the refractive index grating appears periodically on the refractive index grating.

2. The edge emitting laser of claim 1, further comprising: The second current injection window is located between the first gain grating and the second gain grating; The side-emitting laser is configured as follows: When the second current is injected into the resonant cavity through the second current injection window, the second current is injected at a 1 / 4 wavelength phase shift of the refractive index grating layer; The 1 / 4 wavelength phase shift of the refractive index grating layer is determined based on the grating parameters of the refractive index grating layer.

3. The edge-emitting laser according to claim 1, wherein the semiconductor layer further comprises: Substrate, N-type confinement layer, undoped confinement layer, N-type waveguide layer, active layer, P-type waveguide layer, P-type confinement layer, contact layer, isolation layer and the refractive index grating layer; The substrate, the N-type confinement layer, the undoped confinement layer, the N-type waveguide layer, the active layer, the P-type waveguide layer, and the refractive index grating layer are planar thin film layers grown sequentially from the N-plane metal electrode to the P-plane metal electrode. The P-type confinement layer is a three-dimensional thin film layer with protrusions and non-protrusions grown on the refractive index grating layer, and the cross-section obtained by cutting it along the direction of the wide side of the edge-emitting laser is convex. The wide side of the edge-emitting laser is perpendicular to the growth direction, and the shorter side of the edge-emitting laser is also mentioned. The isolation layer is grown on the non-protruding portion of the P-type limiting layer, and the contact layer and the isolation layer are grown sequentially on the protruding portion of the P-type limiting layer, wherein the isolation layer on the non-protruding portion of the P-type limiting layer does not contact the contact layer.

4. The side-emitting laser according to claim 3, wherein, The refractive index grating layer includes: a refractive index grating bottom layer, a refractive index grating etched layer, and a refractive index grating capping layer; The refractive index grating bottom layer is a planar thin film layer disposed on a P-type waveguide layer; The refractive index grating etching layer is a three-dimensional thin film layer with protrusions and non-protrusions disposed on the bottom layer of the refractive index grating. The protrusions and non-protrusions of the refractive index grating etching layer are periodically alternated along the direction of the long side of the edge-emitting laser. The long side of the edge-emitting laser is perpendicular to the growth direction, and the longer side of the edge-emitting laser is the longer side. The refractive index grating cap layer is a three-dimensional thin film layer with protrusions and non-protrusions disposed on the refractive index grating etching layer, wherein the protrusions of the refractive index grating cap layer are embedded in the non-protrusions of the refractive index grating etching layer, and the protrusions of the refractive index grating cap layer are embedded in the refractive index grating etching layer.

5. The side-emitting laser according to claim 3, wherein, The doping concentration of the substrate is greater than the doping concentration of the N-type confinement layer; The N-type confinement layer is used to reduce the absorption loss of free carriers in the side-emitting laser. The free carriers are particles that move freely in the conduction band or valence band of the resonant cavity due to doping.

6. The edge-emitting laser according to claim 2, wherein, The first gain grating, the second gain grating, and the second current injection window are disposed on the P-plane metal electrode corresponding to the protrusion of the P-type confinement layer along the direction of the long side of the edge-emitting laser. The long side of the edge-emitting laser is perpendicular to the growth direction, and the edge-emitting laser is the longer side.

7. The edge-emitting laser according to claim 4, wherein, The first gain grating has periodically arranged protrusions, and the protrusions of the first gain grating correspond one-to-one with the protrusions of the refractive index grating etching layer in the growth direction; and The second gain grating has periodically arranged protrusions, and the protrusions of the second gain grating correspond one-to-one with the protrusions of the refractive index grating etching layer in the growth direction.

8. A method for fabricating a side-emitting laser, comprising: Using metal-organic chemical vapor deposition, a substrate, an N-type confinement layer, an N-type waveguide layer, an active layer, and a P-type waveguide layer are grown sequentially. A refractive index grating layer is grown on the P-type waveguide layer, wherein The refractive index grating layer includes a refractive index grating bottom layer, a refractive index grating etched layer, and a refractive index grating cap layer; The refractive index grating underlayer and the refractive index grating etching layer are grown on the P-type waveguide layer using metal-organic chemical vapor deposition. Using photolithography, equally spaced grating grooves are etched on the refractive index grating etching layer to obtain a refractive index grating structure. The refractive index grating capping layer is grown on the refractive index grating etching layer using metal-organic chemical vapor deposition. A P-type confinement layer and a contact layer were sequentially grown on the refractive index grating layer using metal-organic chemical vapor deposition. Using photolithography, the two sides of the P-type confinement layer and the contact layer are etched in the growth direction to obtain the P-type confinement layer with a "convex" cross-section in the direction parallel to the grating groove. The contact layer is grown on the protrusion of the P-type confinement layer. An isolation layer is grown on the P-type confinement layer and the contact layer using plasma-enhanced chemical vapor deposition. Electrode patterns are etched on the isolation layer using photolithography. A P-plane metal electrode is obtained based on the electrode pattern using an electroplating method; An N-face metal electrode is grown on the side of the substrate away from the N-type confinement layer using an electroplating method to obtain a multilayer structure; as well as The multi-layer structure is cleaved to obtain the edge-emitting laser of a preset size.

9. The preparation method according to claim 8, wherein, The process of obtaining the P-plane metal electrode based on the electrode pattern includes: Using electroplating, a first P-side metal electrode layer and a second P-side metal electrode layer are simultaneously grown on the electrode pattern.

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