A vertical external cavity surface emitting laser

Abstract

The present application discloses a vertical external cavity surface emitting laser, including a collimating lens; a laser emitting chip located on the first side of the collimating lens, the laser emitting chip including a first electrode with a first light outlet, a first contact layer, an active layer, a second contact layer, and a second electrode with a second light outlet stacked in sequence from bottom to top, and the first light outlet is located on the focal plane of the first side of the collimating lens; a diffraction grating located on the second side of the collimating lens, the first side and the second side facing away from each other; a first top cavity mirror located on the side of the laser emitting chip away from the collimating lens or a second top cavity mirror located in the laser emitting chip. The diffraction grating has a wide tuning range and can provide a relatively flat first-order diffraction efficiency, thereby fully covering the gain spectrum range of the active layer of the laser emitting chip, making the wavelength tuning range the gain spectrum range, the wavelength tuning range is widened, and the vertical external resonant cavity increases the cavity length of the gain resonant cavity and narrows the spectral line width.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor lasers, and in particular to a vertical external cavity surface emitting laser. Background Art

[0002] Vertical-External-Cavity Surface-Emitting Laser (VECSEL) is a small semiconductor laser that emits laser light perpendicular to the surface of the semiconductor chip. During the use of VECSEL, it is usually necessary to quickly tune the wavelength. At present, the cavity length tuning principle is widely used to tune the VECSEL. The wavelength is tuned by adjusting the distance between the external cavity mirror and the chip. The tuning range is small and smaller than the gain spectrum range of the emitting chip. The wavelength tuning range of the entire VECSEL is the actual cavity length tuning range of the external cavity mirror and the chip. Due to the limitation of the cavity length tuning range, the wavelength tuning range is limited; at the same time, because the tuning range of the resonant external cavity is very short, the spectral linewidth is still wide.

[0003] Therefore, how to increase the wavelength tuning range of a vertical external cavity surface emitting laser and reduce the spectral line width is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0004] The purpose of the present application is to provide a vertical external cavity surface emitting laser to increase the wavelength tuning range of the vertical external cavity surface emitting laser and reduce the spectral line width.

[0005] In order to solve the above technical problems, the present application provides a vertical external cavity surface emitting laser, comprising:

[0006] Collimating lens;

[0007] A laser emitting chip located on the first side of the collimating lens, the laser emitting chip comprising a first electrode provided with a first light outlet, a first contact layer, an active layer, a second contact layer, and a second electrode provided with a second light outlet, which are stacked in sequence from bottom to top, and the first light outlet is located on the focal plane of the first side of the collimating lens;

[0008] a diffraction grating located on a second side of the collimating lens, the first side being opposite to the second side;

[0009] A first top cavity mirror located at a side of the laser emitting chip away from the collimating lens or a second top cavity mirror located in the laser emitting chip.

[0010] Optionally, when the second top cavity mirror is included, the second top cavity mirror is a distributed Bragg reflector or a high-reflection dielectric mirror, wherein the high-reflection dielectric mirror includes stacked multilayer dielectric films.

[0011] Optionally, when the first top cavity mirror is included, the first top cavity mirror is a plano-concave lens.

[0012] Optionally, also include:

[0013] A broadband high-reflective coating is located on the refractive surface of the plano-concave lens.

[0014] Optionally, also include:

[0015] A broadband anti-reflection coating is located on a plane of the plano-concave lens opposite to the refractive surface.

[0016] Optionally, also include:

[0017] A broadband anti-reflection coating is located on the contact surface between the first light outlet and the first contact layer.

[0018] Optionally, also include:

[0019] A broadband anti-reflection coating is located on the surface of the collimating lens.

[0020] Optionally, the collimating lens is a circular aspheric lens.

[0021] Optionally, the diffraction grating is a blazed grating or a holographic grating.

[0022] A vertical external cavity surface emitting laser provided in the present application includes a collimating lens; a laser emitting chip located on a first side of the collimating lens, the laser emitting chip including a first electrode provided with a first light outlet, a first contact layer, an active layer, a second contact layer, and a second electrode provided with a second light outlet, which are stacked in sequence from bottom to top, and the first light outlet is located on the focal plane of the first side of the collimating lens; a diffraction grating located on the second side of the collimating lens, the first side being opposite to the second side; a first top cavity mirror located on a side of the laser emitting chip away from the collimating lens or a second top cavity mirror located in the laser emitting chip.

[0023] It can be seen that the vertical external cavity surface emitting laser in the present application includes a collimating lens, a laser emitting chip, a diffraction grating, and any one of a first top cavity mirror and a second top cavity mirror. The diffraction grating has a very wide tuning range and can provide a relatively flat first-order diffraction efficiency, so that the gain spectrum range of the active layer of the laser emitting chip can be fully covered, so that the wavelength tuning range of the vertical external cavity surface emitting laser is the gain spectrum range, and the wavelength tuning range is widened. On the other hand, any one of the first top cavity mirror and the second top cavity mirror and the diffraction grating form a vertical external resonant cavity. The vertical external resonant cavity greatly expands the cavity length of the gain resonant cavity, and the resonant cavity finesse is greatly improved, so that the spectral linewidth is narrowed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A structural block diagram of a vertical external cavity surface emitting laser provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of the structure of a vertical external cavity surface emitting laser provided in an embodiment of the present application;

[0027] Figure 3 A schematic diagram of the structure of a laser emission chip provided in an embodiment of the present application;

[0028] Figure 4 A schematic diagram of the structure of another laser emission chip provided in an embodiment of the present application;

[0029] Figure 5 A schematic diagram of the structure of another laser emission chip provided in an embodiment of the present application;

[0030] In the figure, 1. collimating lens, 2. laser emitting chip, 3. diffraction grating, 4. first top cavity mirror, 21. first electrode, 22. first contact layer, 23. active layer, 24. second contact layer, 25. second electrode, 26. first light output port, 27. second light output port, 28. second top cavity mirror. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] As described in the background technology section, the wavelength tuning of the vertical external cavity surface emitting laser is currently achieved by adjusting the distance between the external cavity mirror and the chip, and the tuning range is small, resulting in a narrow wavelength tuning range and a wide spectral linewidth.

[0034] In view of this, the present application provides a vertical external cavity surface emitting laser, please refer to Figures 1 to 3 , Figure 1 A schematic diagram of the structure of a vertical external cavity surface emitting laser provided in an embodiment of the present application is shown in FIG. Figure 2 A schematic diagram of the structure of a vertical external cavity surface emitting laser provided in an embodiment of the present application is shown in FIG. Figure 3 A schematic diagram of the structure of a laser emitting chip provided in an embodiment of the present application, the vertical external cavity surface emitting laser comprises:

[0035] Collimating lens 1;

[0036] A laser emitting chip 2 located on the first side of the collimating lens 1, the laser emitting chip 2 comprising a first electrode 21 with a first light outlet 26, a first contact layer 22, an active layer 23, a second contact layer 24, and a second electrode 25 with a second light outlet 27 stacked in sequence from bottom to top, and the first light outlet 26 is located on the focal plane of the first side of the collimating lens 1;

[0037] a diffraction grating 3 located at a second side of the collimating lens 1, the first side being opposite to the second side;

[0038] The first top cavity mirror 4 located at a side of the laser emitting chip 2 away from the collimating lens 1 or the second top cavity mirror 28 located in the laser emitting chip 2 .

[0039] Preferably, the first side is a side of the collimating lens having a refractive surface with a large curvature radius.

[0040] It should be noted that the first light outlet 26 and the second light outlet 27 are arranged opposite to each other.

[0041] It can be understood that only one of the first top cavity mirror 4 and the second top cavity mirror 28 exists, that is, when the vertical external cavity surface emitting laser includes the first top cavity mirror 4, the second top cavity mirror 28 is not included; when the vertical external cavity surface emitting laser includes the second top cavity mirror 28, the first top cavity mirror 4 is not included.

[0042] Optionally, when the vertical external cavity surface emitting laser has the first top cavity mirror 4, the first top cavity mirror 4 is a plano-concave lens. In this case, the structure of the laser emitting chip 2 is as follows: Figure 3 shown.

[0043] The first light outlet 26 is located on the focal plane of the first side of the collimating lens 1, that is, the first light outlet 26 is opposite to the collimating lens 1. The function of the collimating lens 1 is to collimate the light emitted from the first light outlet 26 and make it incident on the diffraction grating 3, and focus the first-order diffraction light fed back by the diffraction grating 3 and inject it into the first light outlet 26 until it is transmitted to the active layer 23.

[0044] The diffraction grating 3 can provide a first-order diffraction efficiency of more than 95% in a wide wavelength range, can fully cover the gain spectrum range of the active layer 23 of the laser emitting chip 2, and achieve a wider wavelength tuning range.

[0045] It should be noted that in this embodiment, the diffraction grating 3 is not specifically limited and depends on the situation. For example, the diffraction grating 3 is a blazed grating or a holographic grating.

[0046] Furthermore, in this embodiment, the grating angle of the diffraction grating 3 is not specifically limited, and the wavelength of the vertical external cavity surface emitting laser is tuned by adjusting the grating angle. Similarly, in this embodiment, the number of grating lines of the diffraction grating 3 is not specifically limited, and it depends on the operating band of the vertical external cavity surface emitting laser. Similarly, in this embodiment, the grating period is not specifically limited, and it depends on the operating wavelength of the vertical external cavity surface emitting laser.

[0047] The collimating lens 1 can convert the large divergence angle light beam outputted from the first light outlet 26 into a collimated light beam with an ultra-low divergence angle, and can also convert the first-order diffraction light fed back from the diffraction grating 3 into a focused light beam incident on the first light outlet 26 to realize external cavity light feedback.

[0048] It should be noted that the structure of the active layer 23 is not specifically limited in this embodiment and depends on the situation. For example, the active layer 23 can be any one of a GaAs-based active layer 23, an InP-based active layer 23, a GaSb-based active layer 23, a quantum well structure active layer 23, and a quantum dot structure active layer 23.

[0049] Specifically, the first contact layer 22 and the second contact layer 24 form ohmic contacts with the first electrode 21 and the second electrode 25, respectively, as a low impedance interface for external drive current injection. The external drive current is injected into the active layer 23 through the first electrode 21 and the second electrode 25 to generate radiated light, providing optical gain in the working band required by the vertical external cavity surface emitting laser. The second top cavity mirror 28 provides a wide-spectrum reflector function on the top side, and the radiated light is output from the first light outlet 26, and is converted into a collimated light beam after passing through the collimating lens 1, and is incident on the diffraction grating 3. The diffraction grating 3 provides a high-efficiency first-order diffraction light (providing a high reflector function on the bottom side) returned along the original optical path, and is focused into the first light outlet 26 after passing through the collimating lens 1 until it is transmitted to the active layer 23. The radiated light oscillates back and forth between the second top cavity mirror 28 and the diffraction grating 3 to form a gain resonant cavity; or the first top cavity mirror 4 provides a wide-spectrum reflector function on one side of the top surface, and at this time the radiated light oscillates back and forth between the first top cavity mirror 4 and the diffraction grating 3 to form a gain resonant cavity.

[0050] The vertical external cavity surface emitting laser in this embodiment includes a collimating lens 1, a laser emitting chip 2, a diffraction grating 3, and any one of a first top cavity mirror 4 and a second top cavity mirror 28. The diffraction grating 3 has a very wide tuning range and can provide a relatively flat first-order diffraction efficiency, so that the gain spectrum range of the active layer 23 of the laser emitting chip 2 can be fully covered, so that the wavelength tuning range of the vertical external cavity surface emitting laser is the gain spectrum range, and the wavelength tuning range is widened. On the other hand, any one of the first top cavity mirror 4 and the second top cavity mirror 28 and the diffraction grating 3 form a vertical external resonant cavity. The vertical external resonant cavity greatly expands the cavity length of the gain resonant cavity, greatly improves the resonant cavity finesse, and narrows the spectral line width.

[0051] In one embodiment of the present application, when the vertical external cavity surface emitting laser includes the second top cavity mirror 28, the second top cavity mirror 28 is a distributed Bragg reflector or a reflective dielectric mirror, wherein the high reflective dielectric mirror includes a stacked multilayer dielectric film.

[0052] For details, please refer to Figure 4 , Figure 4 This is a schematic structural diagram of another laser emitting chip 2 provided in an embodiment of the present application. When the second top cavity mirror 28 is a distributed Bragg reflector, the second top cavity mirror 28 is located between the active layer 23 and the second contact layer 24.

[0053] For details, please refer to Figure 5 , Figure 5 This is a schematic structural diagram of another laser emitting chip 2 provided in an embodiment of the present application. When the second top cavity mirror 28 is a high-reflection dielectric mirror, the second top cavity mirror 28 is located on the surface of the second electrode 25 away from the active layer 23 .

[0054] Preferably, when the vertical external cavity surface emitting laser is a long wavelength vertical external cavity surface emitting laser, the vertical external cavity surface emitting laser includes a first top cavity mirror 4, and the laser emitting chip 2 is Figure 2 As shown in the structure, because long-wavelength vertical cavity surface emitting lasers generally adopt InP-based or GaSb-based semiconductor material systems, relative to the common near-infrared GsAs-based semiconductor material system, if a distributed Bragg reflector is included in the laser emitting chip 2, the difference between its high and low refractive indexes is small, and the working wavelength is long, which will cause the distributed Bragg reflector to be very thick and the loss to be very large; even if a high-reflection dielectric mirror is used in the laser emitting chip 2, it will be very thick, resulting in large losses and difficulty in preparation. The first top cavity mirror 4 and the diffraction grating 3 are used to form a vertical external resonant cavity, which can completely avoid the above shortcomings.

[0055] On the basis of the above embodiments, in one embodiment of the present application, the vertical external cavity surface emitting laser further includes:

[0056] The broadband high-reflective coating located on the refractive surface of the plano-concave lens can effectively improve the light feedback efficiency.

[0057] Furthermore, the vertical external cavity surface emitting laser further comprises:

[0058] The broadband anti-reflection coating located on the plane opposite to the plano-concave lens and the refractive surface can effectively reduce the optical power loss.

[0059] On the basis of any of the above embodiments, in one embodiment of the present application, the vertical external cavity surface emitting laser further includes:

[0060] The broadband anti-reflection coating is located on the contact surface between the first light outlet 26 and the first contact layer 22 to reduce Fresnel reflection of light at the first light outlet 26 and improve the light transmission efficiency of the gain resonant cavity.

[0061] Preferably, the vertical external cavity surface emitting laser further comprises: a broadband anti-reflection coating located on the surface of the collimating lens 1 to improve the transmittance of light and improve the light transmission efficiency of the gain resonant cavity.

[0062] Furthermore, broadband anti-reflection coatings are provided on both surfaces of the collimating lens 1 .

[0063] Preferably, the collimating lens 1 is a circular aspheric lens. Since the light beam emitted by the laser emitting chip 2 is generally circularly symmetrical, the circular aspheric lens can achieve a very ideal collimation effect on the light beam.

[0064] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0065] The vertical external cavity surface emitting laser provided by the present application is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A vertical external cavity surface emitting laser, characterized in that: include: Collimating lens; A laser emitting chip located on the first side of the collimating lens, the laser emitting chip comprising a first electrode provided with a first light outlet, a first contact layer, an active layer, a second contact layer, and a second electrode provided with a second light outlet, which are stacked in sequence from bottom to top, and the first light outlet is located on the focal plane of the first side of the collimating lens; A diffraction grating located on a second side of the collimating lens, the first side being opposite to the second side; the diffraction grating provides a first-order diffraction efficiency of more than 95% within a wavelength range, covering a gain spectrum range of an active layer of a laser emission chip; A second top cavity mirror located in the laser emitting chip; the second top cavity mirror and the diffraction grating form a vertical external resonant cavity; The second top cavity mirror provides a wide-spectrum reflector function on one side of the top surface. The radiated light is output from the first light outlet, converted into a collimated light beam after passing through the collimating lens, and incident on the diffraction grating. The diffraction grating provides high-efficiency first-order diffracted light returning along the original optical path, which is focused into the first light outlet after passing through the collimating lens until it is transmitted to the active layer. The radiated light oscillates back and forth between the second top cavity mirror and the diffraction grating to form a gain resonant cavity.

2. The vertical external cavity surface emitting laser according to claim 1, characterized in that: When the second top cavity mirror is included, the second top cavity mirror is a distributed Bragg reflector or a high-reflection dielectric mirror, wherein the high-reflection dielectric mirror includes stacked multi-layer dielectric films.

3. The vertical external cavity surface emitting laser according to any one of claims 1 to 2, characterized in that: Also includes: A broadband anti-reflection coating is located on the contact surface between the first light outlet and the first contact layer.

4. The vertical external cavity surface emitting laser according to claim 3, characterized in that: Also includes: A broadband anti-reflection coating is located on the surface of the collimating lens.

5. The vertical external cavity surface emitting laser according to claim 4, characterized in that: The collimating lens is a circular aspheric lens.

6. The vertical external cavity surface emitting laser according to claim 5, characterized in that: The diffraction grating is a blazed grating or a holographic grating.

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