An optical integrated chip comprising a semiconductor laser and a photodetector

Abstract

The application discloses an optical integrated chip containing a semiconductor laser and a light detector, which comprises a semiconductor substrate, a semiconductor laser and a semiconductor light detector made on the semiconductor substrate, and a transition structure which is opened on the semiconductor substrate and located between the semiconductor laser and the semiconductor light detector. In the application, most of the semiconductor laser spots coincide with the etching groove end face and return to the laser cavity through the reflection structure thereon, and a small part of the spot edge is fed into the light detector from the unetched channel. The structure is defined by a mask mask pattern, and controllable and efficient light coupling of the light detector can be realized, so as to accurately characterize the working state of the laser. In addition, the light from the laser cavity to the light detector is constrained in the waveguide structure and cannot become stray light, thereby affecting the normal working of the laser.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor laser and photodetector integration, and particularly relates to an optical integrated chip containing a semiconductor laser and a photodetector. BACKGROUND

[0002] Semiconductor lasers are widely used in optical communication and optical sensing systems as a high efficient and compact light source. However, as a failure-prone device in the system, a photodetector is usually configured to monitor the actual operation state of the semiconductor laser. Conventional semiconductor lasers are usually coated with a high-reflectivity multilayer dielectric film on the back facet formed by cleaving. Such a dielectric film can partially reflect and partially transmit light. The reflectivity is generally controlled at about 90%, so that a small amount of light will transmit through the film and be emitted from the back facet of the laser. Configuring a photodetector at the back of the laser to collect the part of light can characterize the working state of the laser.

[0003] In the above scheme, the light coupling efficiency of the photodetector is a key parameter, which is related to the laser mode spot distribution, the end facet film transmittance, the photodetector position and its light receiving area, and other factors. The scheme needs an additional detector assembly process, and needs to reserve a larger space for the discrete photodetector in the effective module space, thereby affecting the miniaturization design of the corresponding module, and the assembly of discrete devices also introduces potential reliability problems, and the existence of assembly tolerance also affects the consistency of light coupling efficiency.

[0004] Integrating the semiconductor laser and the photodetector on the same substrate can effectively solve the above problems, and can facilitate wafer-level laser testing. US7,598,527B2 patent adopts a laser and photodetector integration scheme based on an etched groove. In the scheme, the etched groove defines the back facet of the laser and simultaneously isolates the laser and the photodetector. The light emitted from the laser facet passes through the gap of the etched groove and then enters the side facet of the photodetector, and then generates a photocurrent after being absorbed by the photodetector. The scheme is simple in structure, but has many technical problems. First, it needs light to be transmitted through the laser facet, which requires the film layer on the laser facet to have a certain transmittance, which limits the use of non-transmissive structures such as metal reflective layers. Second, the light transmitted through the laser facet freely propagates in the etched groove and then needs to be transmitted through the semiconductor facet on the photodetector side before being absorbed by the photodetector, which requires the semiconductor facet on the photodetector side and the attached film layer to be as transmissive as possible, which conflicts with the design goal of the high-reflectivity film layer on the laser facet side, and thus requires an additional process step to achieve. Third, when the transmitted light re-enters the facet on the photodetector side, it is easy to generate reflected light returning to the laser cavity and thus interfering with the normal operation of the laser, which requires introducing a certain reflection suppression structure (for example, the chamfer structure or the inclined surface structure disclosed in US5,032,879 patent) on the photodetector side, which increases the design complexity. SUMMARY

[0005] The purpose of the present application is to provide an optical integrated chip containing a semiconductor laser and a photodetector, most of the laser spot of the semiconductor laser in the chip coincides with the etched groove end face and returns to the laser cavity through the reflection structure thereon, a small part of the laser spot edge is fed into the photodetector from the unetched channel, the structure body is defined by a mask pattern, and controllable and efficient optical coupling of the photodetector can be achieved, thereby accurately characterizing the working state of the laser, in addition, the light from the laser cavity to the photodetector is constrained in the waveguide structure and cannot become stray light, thereby affecting the normal operation of the laser.

[0006] To achieve the above purpose, the following technical solutions are adopted:

[0007] An optical integrated chip containing a semiconductor laser and a photodetector, comprising a semiconductor substrate, and a semiconductor laser and a semiconductor photodetector fabricated on the semiconductor substrate, further comprising

[0008] A transition structure, the transition structure is opened on the semiconductor substrate and located between the semiconductor laser and the semiconductor photodetector; the transition structure comprises a first etched groove, a second etched groove, and an unetched channel between the first etched groove and the second etched groove;

[0009] One of the side walls of the first etched groove constitutes a reflection end face of the laser cavity of the semiconductor laser, the reflection end face is covered with a light reflection layer, and the laser cavity end face area covered by the light reflection layer coincides with the main part of the transverse mode laser spot of the laser cavity;

[0010] The unetched channel coincides with the edge area of the transverse mode laser spot of the laser cavity of the semiconductor laser and allows the part of the laser spot to pass through the unetched channel to the semiconductor photodetector side end face and be absorbed by the semiconductor photodetector to form a photocurrent that can be used to characterize the working characteristics of the semiconductor laser.

[0011] Further, the semiconductor laser is an edge-emitting semiconductor laser of a ridge waveguide structure.

[0012] Further, the semiconductor laser is an edge-emitting semiconductor laser of a buried heterojunction structure.

[0013] Further, the semiconductor laser is a distributed feedback laser.

[0014] Further, the semiconductor photodetector is a waveguide type photodetector.

[0015] Further, the semiconductor laser and the semiconductor light detector adopt the same epitaxial material structure.

[0016] Further, the semiconductor light detector can extend to the un-etched channel to improve the light coupling efficiency.

[0017] Further, the light reflection layer includes a transparent dielectric layer, or a metal layer, or a combined layer of the dielectric layer and the metal layer.

[0018] Further, the light reflection layer is a set of high-reflection film layers, and the reflectivity of the light reflection layer for the light emitted from the reflection end face of the semiconductor laser is ≥60%.

[0019] With the above scheme, the beneficial effects of the present application are:

[0020] 1) Most of the semiconductor laser light spots in the chip coincide with the etched groove end face, and the small part of the light spot edge is fed into the light detector from the un-etched channel, and the structure is defined by a mask pattern, which can realize controllable and efficient light detector light coupling, and accurately characterize the working state of the laser, in addition, the light from the laser cavity to the light detector is constrained in the waveguide structure, and will not become stray light, thereby affecting the normal operation of the laser.

[0021] 2) It can be used for wafer-level testing of laser chips based on etched end faces, such as DFB lasers, compared with conventional bar-level or chip-level testing, wafer-level testing has great advantages in testing efficiency, which can reduce testing firmware overhead, compress testing time and manual time in early screening of failed elements of chip products, also can effectively reduce the waste of accessories, is an effective path to reduce the cost of chip products;

[0022] 3) It can be used for state monitoring of laser chips, compared with the scheme of externally placing a light detector on the laser chip, the integrated scheme can provide more stable and consistent performance, can simplify the packaging process, reduce the size of the component, and also can effectively improve the yield and reliability of the component. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the present application;

[0024] Among them, the figure mark explanation is:

[0025] 1 - semiconductor substrate; 2 - semiconductor laser;

[0026] 3 - semiconductor light detector; 4 - first etched groove;

[0027] 5 - second etched groove; 6 - un-etched channel;

[0028] 7 - light reflection layer. DETAILED DESCRIPTION

[0029] The application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Referring to Figure 1 As shown in the figure, the application provides an optical integrated chip containing a semiconductor laser and a light detector, which includes a semiconductor substrate 1, a semiconductor laser 2 and a semiconductor light detector 3 made on the semiconductor substrate 1, and a transition structure, which is opened on the semiconductor substrate 1 and located between the semiconductor laser 2 and the semiconductor light detector 3; the transition structure includes a first etching groove 4, a second etching groove 5, and an unetched channel 6 between the first etching groove 4 and the second etching groove 5; one side wall of the first etching groove 4 constitutes one reflection end face of the laser cavity of the semiconductor laser 2, and a light reflection layer 7 is coated on the reflection end face, and the laser cavity end face area coated by the light reflection layer 7 coincides with the main part of the transverse mode light spot of the laser cavity; the unetched channel 6 coincides with the edge area of the transverse mode light spot of the laser cavity of the semiconductor laser 2 and allows the part of the light spot to pass through the unetched channel 6 to the side end face of the semiconductor light detector 3, and to be absorbed by the semiconductor light detector 3 and form a photocurrent which can be used to characterize the working characteristics of the semiconductor laser 2.

[0031] Continuing to refer to Figure 1 As shown in the figure, in one embodiment, the first etching groove 4 is opened in the vertical direction, and one side thereof and the light reflection layer 7 coated thereon constitute the back end high reflection end face of the semiconductor laser 2 (the reflection end face structure is not necessarily limited to the conventional dielectric film system, and a non-transmissive metal reflection structure can also be used), and by controlling the positions of the first etching groove 4 and the second etching groove 5 through a mask, the high reflection area can be made to coincide with the main area of the transverse mode light spot of the laser, and a large enough reflectivity can be provided, while allowing part of the light waves (evanescent waves) of the edge area of the transverse mode light spot to pass through the waveguide formed by the unetched channel 6 to reach the on-chip light detector behind, and generate a monitoring current; in this embodiment, most of the light spot of the semiconductor laser 2 in the chip coincides with the etching groove end face, and returns to the laser cavity through the reflection structure thereon, and a small part of the light spot edge is fed into the light detector from the unetched channel 6, and the main body of the structure is defined by the mask pattern, so that controllable and efficient light detector optical coupling can be achieved, and the working state of the laser can be accurately characterized, in addition, the light guided from the laser cavity to the light detector is constrained in the waveguide structure, and will not become stray light, thereby affecting the normal operation of the laser.

[0032] In an embodiment, the semiconductor laser 2 can be any one of the following lasers: a ridge waveguide structure edge-emitting semiconductor laser, a buried heterostructure edge-emitting semiconductor laser, a distributed feedback laser.

[0033] In an embodiment, the semiconductor light detector 3 can be a waveguide type light detector.

[0034] In combination of the above embodiments, the semiconductor laser 2 and the semiconductor light detector 3 can adopt the same epitaxial material structure, and the semiconductor light detector 3 can extend to the un-etched channel 6 to improve the light coupling efficiency; in addition, the light reflection layer 7 can include a transparent dielectric layer, or a metal layer, or a combined layer of the dielectric layer and the metal layer, meanwhile, the light reflection layer 7 can also be a set of high reflection film layers, and the reflectivity of the light reflection layer 7 to the light emitted by the reflection end surface of the semiconductor laser 2 is ≥60%.

[0035] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An optical integrated chip comprising a semiconductor laser and a photodetector, comprising a semiconductor substrate, and a semiconductor laser and a semiconductor photodetector fabricated on the semiconductor substrate, characterized in that, Also included a transition structure, which is opened on the semiconductor substrate and is located between the semiconductor laser and the semiconductor photodetector; the transition structure includes a first etched groove, a second etched groove, and an unetched channel between the first etched groove and the second etched groove; one of the side walls of the first etched groove constitutes a reflective end face of the laser cavity of the semiconductor laser, which is covered with a light reflection layer, and the area of the laser cavity end face covered by the light reflection layer coincides with the main part of the transverse mode spot of the laser cavity; the unetched channel coincides with the edge area of the transverse mode spot of the laser cavity of the semiconductor laser, and allows the spot in the coincident part to pass through the unetched channel to the side end face of the semiconductor photodetector, and to be absorbed by the semiconductor photodetector and form a photocurrent that can be used to characterize the operating characteristics of the semiconductor laser; the semiconductor laser is a ridge waveguide structure edge-emitting semiconductor laser; the semiconductor laser and the semiconductor photodetector use the same epitaxial material structure; the semiconductor photodetector extends to the unetched channel to improve the light coupling efficiency; the light reflection layer is a transparent dielectric layer, or a metal layer, or a combination of a dielectric layer and a metal layer.

2. The optical integrated chip comprising a semiconductor laser and a photodetector according to claim 1, wherein The semiconductor laser is a buried heterostructure edge-emitting semiconductor laser.

3. The optical integrated chip comprising a semiconductor laser and a photodetector according to claim 1, wherein The semiconductor laser is a distributed feedback laser.

4. The optical integrated chip comprising a semiconductor laser and a photodetector according to claim 1, wherein The semiconductor photodetector is a waveguide type photodetector.

5. The optical integrated chip comprising a semiconductor laser and a photodetector according to claim 1, wherein The light reflection layer is a set of high reflection film layers, and its reflectivity for the light emitted by the reflective end face of the semiconductor laser is ≥60%.

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