A high-speed modulated high-power fundamental mode semiconductor laser chip and its use method

Abstract

The present invention discloses a high-speed modulated high-power fundamental mode semiconductor laser chip, comprising an active tapered waveguide, a passive curved waveguide, and an active oscillation-level waveguide arranged on the insulating layer of the chip. The active tapered waveguide and the active oscillation-level waveguide are connected by a passive curved waveguide, and the passive curved waveguide is connected to the narrow end of the active tapered waveguide. At the same time, the active tapered waveguide and the active oscillation-level waveguide are both provided with electrodes, while the passive curved waveguide does not have an electrode, thereby insulating and isolating the active tapered waveguide and the active oscillation-level waveguide. The present invention redesigns a new current injection structure, namely: an active oscillation-level waveguide for generating high-quality fundamental transverse mode seed light, a passive curved waveguide for achieving high-order mode filtering and linewidth compression, and an active tapered waveguide for achieving one-way amplification of fundamental mode light. The electro-optical delay of each chip and the frequency chirp effect caused by changes in carrier concentration are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, and in particular to a high-speed modulated high-power fundamental mode semiconductor laser chip and a use method thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] High-power semiconductor lasers are finding increasingly widespread applications in fields such as pumping, optical communications, medical treatment, and laser detection, placing increasing demands on their performance. Laser modulation refers to the process of using laser light as a carrier to carry low-frequency telecommunications signals. Laser modulation can be categorized as internal modulation or external modulation. Internal modulation involves applying a modulation signal to the laser while it oscillates, converting the information to be transmitted into a current signal and injecting it into the semiconductor laser. This is also known as direct modulation.

[0004] Directly modulated semiconductor lasers have been widely used in the field of optical communications due to their simple structure and easy implementation. At the same time, with the improvement of semiconductor laser power and reliability, directly modulated semiconductor laser systems have also begun to be widely used in the field of laser detection, especially in the fields of laser guidance and lidar. However, since parameters such as the width, frequency and shape of the laser pulse will affect the accuracy of the laser detection system, when the semiconductor laser is injected with current, the laser will produce corresponding electro-optical delay and relaxation oscillation, causing the output light pulse to be inconsistent with the injected electrical pulse signal. In addition, while the laser is relaxing and oscillating, the carrier density inside the laser changes due to the change of the injected pulse, which in turn causes the refractive index to change, and ultimately a frequency chirp effect occurs, causing the frequency of the laser to dynamically slip.

[0005] Chinese patent CN 206059907 U discloses a “semiconductor laser chip with an inverted terraced ridge waveguide”. After the cross-sectional shape of the ridge waveguide is designed to be an inverted trapezoid, the metal contact layer area is much larger than the traditional contact layer area under the same luminous width, which effectively reduces the impedance of the chip under high-speed modulation and significantly reduces the time lag effect. However, the inventors found that in actual applications, the P-side metal of this inverted terraced structure is very prone to fracture, causing device failure. At the same time, due to the inverted terraced structure, the void below will cause changes in the local refractive index and low heat dissipation efficiency, which has an adverse effect on the reliability of the device. In addition, this patented technology still cannot solve the problems of electro-optical delay and improve frequency chirp. Summary of the Invention

[0006] The present invention provides a high-power fundamental-mode semiconductor laser chip with high-speed modulation. By designing a new current injection structure, the semiconductor laser chip effectively improves the electro-optical delay and frequency chirp effect. To achieve the above objectives, the present invention discloses the following technical solutions.

[0007] In a first aspect, the present invention discloses a high-speed modulated, high-power fundamental mode semiconductor laser chip comprising an active tapered waveguide, a passive curved waveguide, and an active oscillation-stage waveguide disposed on an insulating layer of the chip. The active tapered waveguide and the active oscillation-stage waveguide are connected by a passive curved waveguide, which is connected to the narrow end of the active tapered waveguide. Furthermore, the active tapered waveguide and the active oscillation-stage waveguide both have electrodes, while the passive curved waveguide does not, thereby providing insulation isolation between the active tapered waveguide and the active oscillation-stage waveguide.

[0008] Furthermore, one end of the insulating layer has a conical protrusion, and the other end of the insulating layer has a strip-shaped protrusion. The conical protrusion and the strip-shaped protrusion are both covered with an electrode layer, thereby forming the ridge-stripe type active conical waveguide and active oscillation-level waveguide, respectively. This ridge-stripe waveguide has the advantage of a weak refractive index guiding mechanism.

[0009] Furthermore, the conical protrusions and the strip-shaped protrusions are connected by a curved protrusion formed by an insulating layer, and a DBR grating structure is provided on the curved protrusion to form the ridge-strip passive curved waveguide. Similarly, this ridge-strip waveguide has the advantage of a weak refractive index guiding mechanism.

[0010] Furthermore, the DBR grating structure adopts a rectangular Bragg grating, which covers the entire surface of the curved waveguide.

[0011] Furthermore, the passive curved waveguide is located in a groove between the active tapered waveguide and the active oscillating waveguide.

[0012] Furthermore, the width of the narrow end of the active tapered waveguide is consistent with the width of the passive curved waveguide, and the widths of the active oscillation level waveguide and the passive curved waveguide are consistent.

[0013] Furthermore, the wider end of the active tapered waveguide is 10-15 μm wider than the narrow end.

[0014] Furthermore, a groove structure is provided on the bottom surface of the chip to reduce the impedance of the semiconductor substrate, thereby further reducing the electro-optical delay of the chip. Optionally, the depth of the groove structure is between 10 μm and 20 μm.

[0015] Furthermore, the laser chip further comprises the following stacked layers from bottom to top: an N-side electrode, an N-type confinement layer, an N-type waveguide layer, a quantum well active layer, a P-type waveguide layer, and a P-type confinement layer. The insulating layer is provided on the P-type confinement layer.

[0016] In a second aspect of the present invention, a method for using the high-speed modulated high-power fundamental mode semiconductor laser chip is disclosed, including: the electrode current on the active tapered waveguide is in a continuous injection mode, and the injection current value is always less than the threshold current, and the electrode injection current on the active oscillation level waveguide is injected according to signal requirements.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] As mentioned above, when a semiconductor laser is injected with current, the output optical pulses are inconsistent with the injected electrical pulse signals due to electro-optical delay and relaxation oscillation. Furthermore, as the laser relaxes and oscillates, the changes in the injected pulses cause changes in the carrier density inside the laser, which in turn causes changes in the refractive index. This ultimately results in a frequency chirp effect, causing the laser frequency to dynamically shift. To overcome these issues, the present invention redesigns a new current injection structure: an active oscillating waveguide that generates high-quality fundamental transverse mode seed light, a passive curved waveguide that achieves high-order mode filtering and linewidth compression, and an active tapered waveguide that achieves single-pass amplification of the fundamental mode light.

[0019] The fundamental mode light emitted by the active oscillator-level waveguide passes through the passive curved waveguide for high-order mode filtering and absorption, line width compression, and mode locking, and then directly enters the active tapered waveguide for single-pass amplification, thereby suppressing high-order mode lasing while effectively improving the mode locking capability. Since the width of the active tapered waveguide at the light output cavity surface is large, the power density at the cavity surface is reduced, the maximum output power of the semiconductor laser is increased, and the electro-optical delay of each chip and the frequency chirp effect caused by changes in carrier concentration are effectively improved.

[0020] In addition, when using the semiconductor laser chip of the present invention, the electrode current on the active tapered waveguide is in a continuous injection mode, and the injection current value is always less than the threshold current, and the electrode injection current on the active oscillation-level waveguide is injected according to the signal requirements. Its technical advantage is that: since the active tapered waveguide and the active oscillation-level waveguide are current-isolated by the passive curved waveguide and the insulating layer. Therefore, the electrodes on the active tapered waveguide and the active oscillation-level waveguide are in an independent state, and therefore, the electrodes on the active tapered waveguide only need to inject a very small current to make the total current greater than the threshold current, thereby generating a laser. Through this structural design, not only can the electro-optical delay and relaxation oscillation effect of the chip be effectively reduced, but also the time it takes for the device to go from non-luminous to luminous is reduced. In addition, by providing grooves on the back of the chip, the substrate impedance of the chip can be reduced, thereby further reducing the electro-optical delay effect caused by impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 Schematic diagram of the structure of the semiconductor laser chip in the following embodiments.

[0023] Figure 2 FIG. 1 is a top view of a semiconductor laser chip in the following embodiment.

[0024] Figure 3 This is a right side view of the semiconductor laser chip in the following embodiments.

[0025] The numbers in the figure represent the following components: 1-insulating layer, 2-active tapered waveguide, 3-passive curved waveguide, 4-active oscillation-level waveguide, 5-electrode layer, 6-groove, 7-N-side electrode, 8-N-type confinement layer, 9-N-type waveguide layer, 10-quantum well active layer, 11-P-type waveguide layer, 12-P-type confinement layer. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0027] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] For ease of description, the words "upper," "lower," "left," and "right" appearing in this disclosure merely indicate the same orientation as in the accompanying drawings and do not limit the structure. These are intended solely to facilitate and simplify the description of the present invention and do not indicate or imply that the device or component referred to requires a specific orientation, construction, or operation. Therefore, they should not be construed as limiting the present invention. The semiconductor laser coupler will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] refer to Figures 1 to 3 , an example of a high-speed modulated high-power fundamental mode semiconductor laser chip is provided, comprising an active tapered waveguide 2, a passive curved waveguide 3, and an active oscillation-level waveguide 4 arranged on a chip insulating layer 1. This embodiment redesigns a new current injection structure composed of the active tapered waveguide 2, the passive curved waveguide 3, and the active oscillation-level waveguide 4 on the semiconductor laser chip to overcome the electro-optical delay and frequency chirp problems existing in existing semiconductor laser chips. Specifically, the active tapered waveguide 2 and the active oscillation-level waveguide 4 are respectively distributed at both ends of the upper surface of the chip insulating layer 1, and the passive curved waveguide 3 is distributed in a curved shape between the active tapered waveguide 2 and the active oscillation-level waveguide 4 and connects the two.

[0030] The active tapered waveguide 2, passive curved waveguide 3, and active oscillation-stage waveguide 4 all have upwardly protruding ridged structures. The active tapered waveguide 2 is a tapered or body-shaped structure with one end wider and the other narrower. One end of the passive curved waveguide 3 is integrally connected to the narrower end of the active tapered waveguide 2, and the other end of the passive curved waveguide 3 is integrally connected to the active oscillation-stage waveguide 4. Furthermore, the active tapered waveguide 2 and active oscillation-stage waveguide 4 both have electrodes, while the passive curved waveguide 3 does not, thereby providing insulation isolation between the active tapered waveguide 2 and active oscillation-stage waveguide 4.

[0031] The technical advantage of the above-mentioned current injection structure is that when the fundamental mode light emitted by the active oscillating waveguide 4 passes through the passive curved waveguide 3, it can filter and absorb high-order modes, compress the linewidth, and lock the mode. It then directly enters the active tapered waveguide 2 for single-pass amplification, suppressing high-order mode lasing while effectively improving the mode-locking capability. At the same time, because the tapered structure of the active tapered waveguide 2 determines the width of the light output cavity surface, it can reduce the power density of the laser at the cavity surface, increase the maximum output power of the semiconductor laser, and effectively improve the electro-optical delay of each chip and the frequency chirp effect caused by changes in carrier concentration.

[0032] Because the electrode layers 5 on the source tapered waveguide 2 and the active oscillation-level waveguide 4 are in an insulated state, they are equivalent to two independent electrodes. During use, the electrode current on the active tapered waveguide 2 is in a continuous injection mode, and the injected current value is always less than the threshold current (when only this electrode is working, no laser is generated, only pre-oscillation is formed). The electrode injection current on the active oscillation-level waveguide 4 is injected according to signal requirements, that is, this electrode serves as the injection electrode for laser generation. At the same time, because the source tapered waveguide 2 and the active oscillation-level waveguide 4 are connected in series (but not conductive) via the passive curved waveguide 3, the electrode on the active tapered waveguide 2 only needs to inject a very small current to make the total current greater than the threshold current, thereby generating laser light. In this way, the electro-optical delay of the semiconductor laser chip is significantly reduced, while the frequency chirp effect of the device is reduced, and the time it takes for the device to go from non-luminescence to luminescence is shortened.

[0033] Further, refer to Figure 1 The following embodiments illustrate more specific structures of the active tapered waveguide 2, passive curved waveguide 3, and active oscillating waveguide 4. The insulating layer 1 is disposed on the functional layer of the chip, and one end of the insulating layer 1 is machined to form a conical protrusion on its upper surface. A first strip-shaped protrusion is machined on the opposite side of the conical protrusion. A second strip-shaped protrusion is also machined on the insulating layer 1 between the conical protrusion and the strip-shaped protrusion to connect them. In this state, the first strip-shaped protrusion, the second strip-shaped protrusion, and the tapered protrusion are integrally connected. After subsequent processing, the active oscillating waveguide 4, the passive curved waveguide 3, and the active tapered waveguide 2, each with a different functional role, are formed.

[0034] Specifically, the conical and strip-shaped protrusions are both coated with an electrode layer 5, which extends from the protrusions to the edges of the insulating layer (excluding the area where the second strip-shaped protrusion is located), thereby forming the ridge-strip active conical waveguide 2 and active oscillating waveguide 4, respectively. The second strip-shaped protrusions, however, are not provided with the electrode layer 5, but instead with a DBR grating structure, thereby forming the ridge-strip passive curved waveguide 3. In practical applications, the DBR grating structure can be a rectangular Bragg grating, which covers the entire surface of the curved waveguide 3; the metal electrode can be a P-plane electrode.

[0035] As mentioned in the above embodiment, the first strip-shaped protrusion, the second strip-shaped protrusion, and the tapered protrusion are integrally connected. Therefore, to maintain the continuity of the three connections, the width of the narrow end of the active tapered waveguide 2 is consistent with the width of the passive curved waveguide 3, and the widths of the active oscillation-level waveguide 4 and the passive curved waveguide 3 are consistent, thereby ensuring the continuity of the active tapered waveguide 2, the passive curved waveguide 3, and the active oscillation-level waveguide 4 during laser transmission. Specifically, the width of the waveguide can be selected as needed. For example, the width of the passive curved waveguide 3 and the active oscillation-level waveguide 4 can be selected between 2 and 5 μm, such as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, etc. The wider end of the active tapered waveguide 2 is 10-15 μm wider than the narrow end. For example, when the narrow end of the active tapered waveguide 2 is 4 μm, the width of the wider end of the active tapered waveguide 2 can be selected to be 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, etc.

[0036] refer to Figure 1 In another embodiment, the passive curved waveguide 3 is located in the groove 6 between the active tapered waveguide 2 and the active oscillator stage waveguide 4. The passive curved waveguide 3 filters the high-order transverse modes, filtering the seed light generated by the active oscillator stage to ensure that the light entering the active tapered waveguide 2 is in the fundamental transverse mode, thereby achieving the fundamental transverse mode under high-power operating conditions. Simultaneously, the DBR grating structure on the passive curved waveguide 3 locks the longitudinal mode, ultimately achieving a single longitudinal mode fundamental transverse mode operating mode.

[0037] In another preferred embodiment, a groove structure is further provided on the bottom surface of the N-side electrode 7. By providing a groove on the back side of the chip, the substrate impedance of the chip can be reduced, thereby further reducing the electro-optical delay effect caused by the impedance. The depth of the groove structure is between 10 μm and 20 μm, such as 10 μm, 11 μm, 14 μm, 16 μm, 18 μm, 19 μm, 20 μm, etc. The depth of the groove structure can also be adjusted according to actual needs, and this is only for exemplary purposes.

[0038] Continue to refer Figure 1 and Figure 3 The laser chip further includes, stacked from bottom to top, an N-side electrode 7, an N-type confinement layer 8, an N-type waveguide layer 9, a quantum well active layer 10, a P-type waveguide layer 11, and a P-type confinement layer 12. The insulating layer 1 is disposed on the P-side electrode layer 14. The groove 6 is located on the bottom surface of the P-type confinement layer 12.

[0039] Finally, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention. Although the above description of the specific embodiments of the present invention is combined with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations made by those skilled in the art on the basis of the technical solution of the present invention without expending creative effort are still within the scope of protection of the present invention.

Claims

1. A method for using a high-power fundamental mode semiconductor laser chip with high-speed modulation, characterized in that: The high-speed modulated high-power fundamental mode semiconductor laser chip comprises an active tapered waveguide, a passive curved waveguide, and an active oscillating waveguide arranged on the chip insulation layer; Wherein: the active tapered waveguide and the active oscillation-level waveguide are connected via a passive curved waveguide, and the passive curved waveguide is connected to the narrow end of the active tapered waveguide; The active tapered waveguide and the active oscillating waveguide both have electrodes, and the passive curved waveguide does not have electrodes; When in use, the electrode current on the active tapered waveguide is in a continuous injection mode, and the injection current value is always less than the threshold current. The electrode injection current on the active oscillation waveguide is injected according to signal requirements.

2. The method for using the high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 1, characterized in that: One end of the insulating layer has a conical protrusion, and the other end of the insulating layer has a strip-shaped protrusion. The conical protrusion and the strip-shaped protrusion are both covered with an electrode layer, thereby forming the ridge-strip type active conical waveguide and the active oscillation-level waveguide respectively.

3. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 2, characterized in that: The conical protrusions and the strip-shaped protrusions are connected via a curved protrusion formed by an insulating layer, and a DBR grating structure is provided on the curved protrusion, thereby forming the ridge-strip passive curved waveguide.

4. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 3, characterized in that: The DBR grating structure adopts a rectangular Bragg grating, which covers the entire surface of the curved waveguide.

5. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 1, characterized in that: The passive curved waveguide is located in a groove between the active tapered waveguide and the active oscillation level waveguide.

6. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 1, characterized in that: The width of the narrow end of the active tapered waveguide is consistent with the width of the passive curved waveguide, and the widths of the active oscillation waveguide and the passive curved waveguide are consistent.

7. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 1, characterized in that: The wider end of the active tapered waveguide is 10-15 μm wider than the narrow end.

8. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to any one of claims 1 to 7, characterized in that: A groove structure is also provided on the bottom surface of the chip.

9. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 8, characterized in that: The depth of the groove structure is between 10 μm and 20 μm.

10. The method for using a high-speed modulated high-power fundamental mode semiconductor laser chip according to claim 8, characterized in that: The laser chip further comprises: an N-side electrode, an N-type confinement layer, an N-type waveguide layer, a quantum well active layer, a P-type waveguide layer, and a P-type confinement layer stacked in sequence from bottom to top; the insulating layer is arranged on the P-type confinement layer.

Images