An anti-backreflection high-contrast laser and fiber coupling system

Abstract

The present application discloses an anti-backreflection high-contrast laser and fiber coupling system, wherein the anti-backreflection high-contrast laser includes a first reflector layer and a light-emitting layer, the light-emitting layer being provided with a plurality of light-emitting areas, the laser beams of the light-emitting areas being emitted through an exit window on an exit layer, the first reflector layer including a grating area, the grating area including a first diffraction area and a second diffraction area provided around the first diffraction area, and the exit window and the orthographic projection of the first diffraction area on the exit layer partially overlap. The anti-backreflection high-contrast laser provided in the embodiment of the present application can control the intensity distribution of diffracted external interference light by adjusting the structure of the grating layer and the position of the exit window, reduce the intensity of the chip's light-emitting area, reduce or even eliminate the interference of external light on the VCSEL's own light field distribution lasing, and thus reduce the influence of ambient light on the VCSEL surface, improve the signal-to-noise ratio, and increase the transmission rate and distance.

Description

Technical Field

[0001] The present application generally relates to the field of optoelectronic technology, and more particularly to an anti-backreflection high-contrast laser and fiber coupling system. Background Art

[0002] Vertical-Cavity Surface-Emitting Lasers (VCSELs) offer advantages such as high speed, high integration, and cost-effectiveness. They are rapidly developing in areas such as short-distance high-speed parallel optical interconnects, Ethernet data communication networks, and data centers, and are a new type of light source in optical communications. Compared to traditional Distributed Bragg Reflectors (DBRs), High Contrast Grating (HCGs) significantly reduce the divergence angle, thereby improving optical coupling efficiency.

[0003] Back reflection is generated by any interface or scattering center in the optical network. Back reflection can propagate along the optical path or light guide and does not need to be emitted from the closest point to the signal source. When the back-reflected light signal enters the resonant cavity, the change in resonance conditions often causes a large change in the laser output, which interferes with the laser and reduces the laser's signal-to-noise ratio. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide an anti-backreflection high-contrast laser and fiber coupling system, which can use high-order diffraction to reduce or eliminate the interference of backreflected light generated by optical fiber (or other optical devices) on VCSEL, improve the signal-to-noise ratio, and increase the transmission rate and distance.

[0005] In a first aspect, an anti-backreflection high-contrast laser comprises a first reflector layer and a light-emitting layer arranged in a stacked manner, wherein a plurality of light-emitting areas are provided on the light-emitting layer, and the laser light beams of the light-emitting areas are emitted through an exit window on an exit layer, wherein the first reflector layer comprises a grating area, wherein the grating area comprises a first diffraction area and a second diffraction area arranged around the first diffraction area, and the exit window and the orthographic projection of the first diffraction area on the exit layer partially overlap.

[0006] Furthermore, the grating region is a plurality of grating bodies arranged in a periodic array, and the grating body includes a grating bar and a grating groove arranged along the array direction. The grating pitch of the grating body is equal to the width of the grating bar in one grating body plus the width of the grating groove. In the grating bodies arranged in the periodic array, the grating pitches of the grating bodies are all equal. The back-reflected light source located outside the laser passes through the grating region to generate alternating light and dark diffraction stripes on the output layer.

[0007] Preferably, the exit layer is an oxide layer, and an unoxidized region and an oxide region surrounding the unoxidized region are provided on the oxide layer, and the unoxidized region is used to define the exit window.

[0008] Preferably, the emission layer is the light-emitting layer, and a non-injected region and a proton or ion implanted region arranged around the non-injected region are provided on the light-emitting layer, and the non-injected region is used to define a laser emission window.

[0009] Furthermore, the grating portion includes a first grating groove and two first grating bars adjacent to both sides of the first grating groove.

[0010] Preferably, the dark lines generated on the exit layer by the back-reflected light source outside the laser passing through the grating region partially overlap with the first grating grooves, and the position of the exit window corresponds to the area where the dark lines are located.

[0011] Preferably, the central bright stripes generated on the exit layer by the back-reflected light source outside the laser passing through the grating region partially overlap with the grating grooves, and the boundary of the exit window is located between two adjacent central bright stripes.

[0012] Furthermore, it includes a second reflector layer arranged on the side of the light-emitting layer away from the first reflector layer, the first reflector layer is provided with a first electrode on the side away from the light-emitting layer, and the second reflector layer is provided with a second electrode on the side away from the light-emitting layer.

[0013] In a second aspect, the present application provides a fiber coupling system comprising any of the above-described anti-backreflection high-contrast lasers.

[0014] Furthermore, a prism is included, which is configured to receive the laser beam emitted from the exit window, change the direction of the laser beam by refraction, and couple it into the subsequent optical fiber.

[0015] The technical solutions provided by the embodiments of the present application may have the following beneficial effects:

[0016] The anti-back-reflection high-contrast laser provided in the embodiment of the present application can control the intensity distribution of external interference light after diffraction by adjusting the structure of the grating layer and the position of the exit window, reducing its intensity in the light-emitting area of the chip, thereby reducing or even eliminating the interference of external light on the light field distribution lasing of the VCSEL itself, and thus reducing the influence of ambient light on the surface of the VCSEL.

[0017] The anti-backreflection high-contrast laser provided in the embodiment of the present application can improve the signal-to-noise ratio when optically coupled with an optical fiber, which helps to improve the transmission rate and distance; in addition, it reduces the divergence angle of the VCSEL, which is beneficial to the optical coupling efficiency and reduces the performance differences of the optical fiber between different coupling positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0019] Figure 1 A schematic structural diagram of an anti-back reflection high contrast laser provided in an embodiment of the present application;

[0020] Figure 2 A schematic structural diagram of another anti-back reflection high contrast laser provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of an exit window arrangement provided in an embodiment of the present application;

[0022] Figure 4 A schematic diagram of another configuration of an exit window provided in an embodiment of the present application;

[0023] Figure 5 A schematic diagram of another configuration of an exit window provided in an embodiment of the present application;

[0024] Figure 6 A schematic structural diagram of a fiber coupling system provided in an embodiment of the present application.

[0025] In the picture:

[0026] 1. First reflector layer; 2. Light-emitting layer; 3. Light-emitting region; 4. Grating region; 5. Oxide layer; 51. Unoxidized region; 52. Oxide region; 21. Unimplanted region; 22. Proton or ion implanted region; 6. Second reflector layer; 7. Oxide isolation layer; 8. Current spreading layer; 9. Exit window; 41. Gate groove; 42. Gate bar; 401. First gate groove; 402. First gate bar; 10. First electrode; 11. Second electrode; 12. Optical fiber; 13. Prism; 14. Exit layer. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0028] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] Please see Figure 1-2The present application provides an anti-backreflection high-contrast laser, comprising a first reflector layer 1 and a light-emitting layer 2 arranged in a stacked manner, wherein a plurality of light-emitting areas 3 are provided on the light-emitting layer 2, and the laser beams of the light-emitting areas 3 are emitted through an exit window 9 on an exit layer 14, the first reflector layer 1 comprises a grating area 4, the grating area 4 comprises a first diffraction area A and a second diffraction area arranged around the first diffraction area A, and the exit window 9 partially overlaps with the orthographic projection of the first diffraction area on the exit layer 14.

[0030] The light-emitting layer 2 in the present application includes at least a stacked multi-quantum well layer, which is composed of GaAs, AlGaAs, GaAsP, and InGaAs materials. The light-emitting layer 2 is used to convert electrical energy into light energy. Of course, in some examples, a single quantum well layer can be used instead of a multi-quantum well layer. In some examples, quantum dot materials can also be used. The materials of the light-emitting layer 2 are not limited in the embodiments of the present application.

[0031] In some embodiments, as Figure 1 As shown, the output layer 14 is an oxide layer 5 , on which an unoxidized region 51 and an oxide region 52 surrounding the unoxidized region 51 are provided. The unoxidized region 52 is used to define the output window 9 .

[0032] In a specific setting, a wet oxidation process can be used, for example, at a temperature of 430°C, 2L / min of nitrogen carrying water vapor of a certain temperature can be used for selective wet oxidation. The oxidation depth, that is, the extension depth of the oxide layer 5 in the left and right directions is controlled by time to form an oxidation zone in the oxide layer 5, and the central part, the part that has not been wet oxidized, forms an unoxidized zone.

[0033] When a high-contrast grating vertical cavity surface emitting laser is provided with multiple light-emitting areas 3, the current flowing through each light-emitting area 3 is made uniform by providing an oxide layer 5, so that the brightness consistency of the light-emitting area 3 is high, thereby improving the quality of the vertical cavity surface emitting laser.

[0034] In some embodiments, as Figure 2 As shown, the emission layer 14 is the light-emitting layer 22 , and the light-emitting layer 22 is provided with a non-implanted area 21 and a proton or ion implanted area 22 arranged around the non-implanted area 21 . The non-implanted area 22 is used to define the laser emission window 9 .

[0035] In a specific configuration, a protective structure for the proton or ion implantation process, such as a photoresist, is provided on the grating region 4. Through the proton or ion implantation process, a proton or ion implanted region and a non-implanted region are formed in the light-emitting layer 2. The proton or ion implanted region surrounds the non-implanted region, and the non-implanted region is used to define the laser exit window 9. The non-implanted region is the area covered by the protective structure for the proton or ion implantation process.

[0036] The area covered by the proton or ion implantation protection structure primarily protects the underlying layers during the proton or ion isolation implantation, preventing them from being insulated during the implantation. The proton or ion implantation protection structure is removed after the implantation process is complete.

[0037] This structure eliminates the need for an oxide layer 5 and eliminates the need for etching the oxide trench, thereby simplifying the manufacturing process and reducing the complexity of the fabrication.

[0038] It should be noted that in the embodiments of the present application, other layer structures may be provided between the light-emitting layer and the first reflector layer or between the oxide layer and the first reflector layer, such as an oxide isolation layer 7 or a current spreading layer 8, etc. The present application does not limit the specific structure between the various levels of the laser.

[0039] In the embodiment of the present application, the anti-backreflection high-contrast laser further includes a second reflector layer 6 arranged on the side of the light-emitting layer 2 away from the first reflector layer 1, the first reflector layer 1 is provided with a first electrode 10 on the side away from the light-emitting layer 2, and the second reflector layer 6 is provided with a second electrode 11 on the side away from the light-emitting layer 2.

[0040] The second reflector layer may be a DBR. The second reflector layer may be composed of two materials with different refractive indices, AlGaAs and GaAs, stacked together. The substrate and the second reflector layer may both be N-type or both be P-type.

[0041] The resonant cavity is a necessary and crucial component of a fiber laser. It typically consists of two fully reflective mirrors and a semi-reflective mirror, located at either end of the resonant cavity's optical path. These two mirrors reflect light to form the resonant cavity. Using a high-reflectivity grating as the fully reflective mirror in the laser resonant cavity, spontaneous radiation oscillates within the cavity, generating stimulated emission and producing laser output.

[0042] A laser beam within a resonant cavity enters a material with a high refractive index from a low refractive index. The light is reflected by the grating region, resulting in a high reflectivity when the light inside the resonator reaches the grating layer in the forward direction. The wavelength of a laser beam is typically between 1.0 μm and 2.0 μm, while the wavelength of visible light is typically between 390 nm and 780 nm.

[0043] For the back-reflected light beam outside the resonant cavity, it is refracted from the high-refractive-index material into the low-refractive-index material. When the external light reaches the grating layer, diffraction occurs.

[0044] For height ratio gratings, they have extremely high reflectivity and reflection bandwidth, which are adjusted by multiple factors such as substrate refractive index, grating period, duty cycle, etching depth, morphology, etc.

[0045] In the prior art, it is necessary to adjust various chip parameters, such as changing the doping concentration of rare-earth ion-doped quartz fiber or modifying the grating structure, to achieve a higher signal-to-noise ratio for the laser. However, in this application, a special grating area design is used to cause external interference light to diffract when passing through this layer structure. By changing the grating design, the diffracted light intensity distribution on the plane above the exit window can be controlled. Combined with adjusting the exit window position and area, this can reduce or even eliminate back-reflected light entering the resonant cavity, thereby improving the signal-to-noise ratio.

[0046] It should be noted that the signal-to-noise ratio (SNR) = Signal / Noise. In the prior art, the signal-to-noise ratio is improved by enhancing the signal, while in this application, the signal-to-noise ratio is mainly improved by reducing Nosie. Secondly, without the influence of interfering light on the luminous area, the laser light emission is not affected, which also improves the signal.

[0047] High-contrast grating (HCG) is a grating with a period smaller than the wavelength of light, resulting in high reflectivity and transmissive focusing capabilities. In existing HCG structures, the grating period is adjusted so that when light strikes the surface, the grating does not undergo higher-order diffraction. However, in the first reflector layer of the present embodiment, it is not necessary to adjust the grating period to be smaller than the wavelength of the backreflected light, as this would introduce significant manufacturing difficulties.

[0048] In an embodiment of the present application, the grating area is a plurality of grating bodies arranged in a periodic array, and the grating body includes a grating bar 42 and a grating groove 41 arranged along the array direction. The grating pitch of the grating body is equal to the width of the grating bar 42 in one grating body plus the width of the grating groove 41. In the grating bodies arranged in the periodic array, the grating pitches of the grating bodies are all equal.

[0049] It should be noted that this application is directed to a periodically arranged grating, which can allow the back-reflected light source outside the laser to pass through the grating area to produce alternating light and dark diffraction fringes on the output layer. This involves the diffraction principle of the grating.

[0050] The operating principle of a diffraction grating is that the phases of light reflected or transmitted by the grating lines, following different optical paths, interfere constructively in certain directions and destructively in other directions. The angular directions in which constructive interference occurs form so-called diffraction orders, which are known to depend on the wavelength of the light and the pitch of the grating. There is little light in the angular directions between these diffraction orders because the contributions in these directions interfere destructively.

[0051] Grating order of the diffraction grating (k), diffraction wavelength (λ), incident angle (α), diffraction angle And the relationship between the grating constant (d): In the formula, k can be 0, 1, 2..., and the corresponding spectra are called zero-order spectrum, first-order spectrum, second-order spectrum...

[0052] For a periodic grating, the grating constant d is the grating pitch (groove width a + rib width b). The incident angle is the angle between the incident beam and the grating normal, while the diffraction angle is the angle between the diffracted beam and the grating normal.

[0053] In the embodiment of the present application, the light source is back-reflected. Assuming that the incident angle is perpendicular to the grating, that is, the incident angle is 0°, the diffraction formula is obtained:

[0054] The optical path difference and vibration phase difference between the parallel light emitted from two adjacent slits:

[0055]

[0056] Since the grating in the grating region in the embodiment of the present application is configured with multiple slits, the diffraction fringes obtained after back reflection through the grating region are thin and bright, and the diffraction fringes generated by different numbers of slits are different.

[0057] For the main maximum (center of the central bright fringe):

[0058] when That is, δ=2β=±2kπ.

[0059] At this time, the inter-slit interference factor is the largest, so the position satisfying dsinθ=±kλ is the main maximum of multi-slit interference.

[0060] In grating diffraction, there are some dark stripes between the two main maximum stripes. This is caused by the interference between the slits. Assuming that the total number of grating slits is N, the minimum (the center of the dark stripe) is:

[0061] when That is, Nδ=±2kπ

[0062] At this time, the interslit interference factor is 0, so it satisfies The position is the main minimum of multi-slit diffraction, m≠0,±N,2N,…, and there are N-1 minima between two adjacent main maxima.

[0063] There are N-2 secondary maxima between the N-1 minima, but the light intensity is very small.

[0064] From the above, we can see that when the grating pitch is constant, as the number of slits increases, the bright fringes become thinner and brighter, while the dark areas between the bright fringes expand. When the number of grating slits N is large, a dark background is actually formed between the main maxima.

[0065] It should also be noted that grating diffraction will also have the phenomenon of missing levels. When the main maximum position of multi-slit interference coincides with the position of the dark stripes of single-slit diffraction, the bright stripes where the main maximum should appear will not appear, and dark stripes will form there. This phenomenon is called missing levels.

[0066] Level missing conditions: and Where a is the gate trench width.

[0067] The missing levels are:

[0068] For example: d / a = 2, then: k = ±2, ±4, ±6, ... missing levels.

[0069] For example: d / a = 3, then: k = ±3, ±6, ±9, ... are missing levels.

[0070] In addition, the size of the diffraction angle is related to the wavelength of the incident wave. After the white light passes through the grating area, various monochromatic lights will produce separate stripes, forming the diffraction spectrum of the grating. The central bright stripe is still white, and on both sides of the central bright stripe, the various levels of spectrum are arranged symmetrically.

[0071] In the embodiment of the present application, since the position of the emission layer can be adjusted, for example, it can be set on the oxide layer or on the light-emitting layer, for the same grating area, the position of the emission layer is different, and the center positions of the bright and dark lines are also different.

[0072] In order to reduce the amount of light entering the resonant cavity and reduce its impact on the VCSEL light field distribution, in the embodiment of the present application, the setting position of the exit window is adjusted so that it contains fewer bright stripes in the diffraction stripes, which can reduce the diffraction light.

[0073] In the embodiment of the present application, the grating portion includes a first grating groove 401 and two first grating strips 402 adjacent to both sides of the first grating groove 401. That is, the first diffraction region limiting the grating region includes only one grating groove.

[0074] It should be noted that in the embodiments of the present application, the grating portion defines the specific position of the grating in the grating region. In some embodiments, for example, if the number of grating grooves is an even number, one of the two grating grooves at the center position can be selected as the first grating groove. This application does not limit the specific position of the grating groove. For another example, in some embodiments, for example, if the number of grating grooves is an odd number, the grating groove at the center position can be selected as the first grating groove.

[0075] In one embodiment, the central bright stripes generated on the exit layer by the back-reflected light source outside the laser passing through the grating region partially overlap with the grating grooves, and the boundary of the exit window is located between two adjacent central bright stripes.

[0076] Since the position of the diffraction stripes is related to the grating parameters and the position of the exit layer, such as Figure 3 The figure shows the position of a diffraction spot when the grating number is 5. Figure 4 The figure shows the position of another diffraction spot when the grating number is 20. Due to the different grating numbers, the setting position of the exit window can be adjusted according to the spot.

[0077] In one embodiment, the dark lines generated on the output layer by the back-reflected light source outside the laser passing through the grating region partially overlap with the first grating grooves, and the position of the output window corresponds to the area where the dark lines are located.

[0078] Since the position of the diffraction stripes is related to the grating parameters and the position of the exit layer, such as Figure 4 Shown is the position of a diffraction spot when the exit layer is located at another position. Since there are dark stripes between the first grid groove position and the first grid strip position, the back-reflected light at this position of the present application all enters the resonant cavity.

[0079] In this embodiment, external back-reflected interference light is diffracted at the grating area. The exit window partially blocks the diffracted light, preventing the backlight from entering the resonant cavity. This reduces its impact on the VCSEL light field distribution, improves the signal-to-noise ratio, and increases transmission rate and distance. Furthermore, by controlling the area of the exit window, the laser's divergence angle is reduced, which helps improve optical coupling efficiency.

[0080] Second, as Figure 6 As shown, the present application provides a fiber coupling system, comprising any of the above-described anti-back reflection high-contrast lasers.

[0081] Furthermore, a prism 13 is included, which is configured to receive the laser beam emitted from the exit window 9 , change the direction of the laser beam by refraction, and couple it into the subsequent optical fiber 12 .

[0082] It should be noted that Figure 6 Only the case where the optical fiber is perpendicular to the laser is shown. In some embodiments, the light-emitting angle of the prism is adjusted so that the light-emitting angle of the laser beam corresponds to the position of the optical fiber.

[0083] The laser in the embodiment of the present application is applicable not only to the case of direct coupling between the optical fiber and the laser, but also to the case of indirect coupling between the optical fiber and the laser. The back-reflected light can come from any optical element (such as a prism) on the optical hole of the chip. There is a prism between the optical fiber and the VCSEL to redirect the light.

[0084] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0085] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0086] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art of the present invention. The terms used herein are only for describing specific implementation purposes and are not intended to limit the present invention. Terms such as "setting" appearing in this article can mean that one component is directly attached to another component, or that one component is attached to another component through an intermediate component. Features described in this article in one embodiment can be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or otherwise specified.

[0087] The present invention has been described through the above embodiments, but it should be understood that the above embodiments are for illustrative and illustrative purposes only and are not intended to limit the present invention to the described embodiments. Those skilled in the art will appreciate that various variations and modifications may be made based on the teachings of the present invention, and such variations and modifications fall within the scope of protection claimed in the present invention.

Claims

1. An anti-back reflection high contrast laser, characterized in that: The laser diode comprises a first reflector layer and a light-emitting layer, the light-emitting layer being provided with a plurality of light-emitting areas. The laser beams of the light-emitting areas are emitted through an exit window on an exit layer. The first reflector layer comprises a grating area, the grating area comprises a first diffraction area and a second diffraction area arranged around the first diffraction area. The exit window and the orthographic projection of the first diffraction area on the exit layer partially overlap. The grating region comprises a plurality of grating bodies arranged in a periodic array, wherein the grating bodies include a grating bar and a grating groove arranged along the array direction, and the grating pitch of the grating body is equal to the sum of the width of the grating bar in one grating body and the width of the grating groove. In the grating bodies arranged in the periodic array, the grating pitches of the grating bodies are all equal, and the first diffraction region includes a first grating groove and two first grating bars adjacent to both sides of the first grating groove; A back-reflected light source located outside the laser transmits through the grating region to generate alternating light and dark diffraction fringes on the exit layer, wherein the dark fringes generated on the exit layer by the back-reflected light source located outside the laser transmits through the grating region to partially overlap with the first grating grooves, and the position of the exit window corresponds to the region where the dark fringes are located; The central bright stripes generated on the exit layer by the back-reflected light source outside the laser through the grating area partially overlap with the grating grooves, and the boundary of the exit window is located between two adjacent central bright stripes.

2. The anti-back reflection high contrast laser according to claim 1, characterized in that: The emission layer is an oxide layer, and an unoxidized area and an oxide area surrounding the unoxidized area are provided on the oxide layer. The unoxidized area is used to define the emission window.

3. The anti-back reflection high contrast laser according to claim 1, characterized in that: The emission layer is the light-emitting layer. The light-emitting layer is provided with a non-injection area and a proton or ion injection area surrounding the non-injection area. The non-injection area is used to define a laser emission window.

4. The anti-back reflection high contrast laser according to claim 1, characterized in that: It also includes a second reflector layer arranged on the side of the light-emitting layer away from the first reflector layer, the first reflector layer is provided with a first electrode on the side away from the light-emitting layer, and the second reflector layer is provided with a second electrode on the side away from the light-emitting layer.

5. A fiber coupling system, characterized in that: The invention comprises the anti-back reflection high contrast laser according to any one of claims 1 to 4.

6. The optical fiber coupling system according to claim 5, wherein: The system also includes a prism configured to receive the laser beam emitted from the exit window, change the direction of the laser beam by refraction, and couple the laser beam into a subsequent optical fiber.

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