Laser chip and preparation method thereof

Abstract

The invention relates to the technical field of optical communication, and provides a laser chip which comprises an electro-absorption modulator and a semiconductor optical amplifier and further comprises a reflection grating used for reflecting spontaneous radiation light of the reflection semiconductor optical amplifier, the semiconductor optical amplifier is arranged on the light outlet side of the electro-absorption modulator, and the reflection grating is used for reflecting the spontaneous radiation light of the reflection semiconductor optical amplifier. The reflection grating is arranged in the area where the semiconductor optical amplifier is located, and the reflection grating is arranged close to the area where the electro-absorption modulator is located. The invention also provides a preparation method of the laser chip. By arranging the reflection grating, spontaneous radiation light of the semiconductor optical amplifier can be reflected, light crosstalk is reduced, and signal quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, in particular to a laser chip and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of Internet technology, the growing bandwidth demand of users has promoted the gradual upgrade of the fiber-optic access PON market to the 50G-PON solution, and also put forward high-power and high-bandwidth requirements for the performance of semiconductor lasers as light source devices. By integrating the semiconductor optical amplifier SOA into the electro-absorption modulated laser EML, a higher output optical power can be achieved at the same power consumption level compared with the existing EML, while also being able to bring into play the advantages of EML such as large modulation bandwidth and low chirp, and even being able to generate negative chirp in the input optical signal. EML-SOA integrated devices have become an ideal choice for 50G PON high-speed optical network light source chips. However, after SOA is integrated at the back end of EML, optical crosstalk between different working areas will be caused, especially the spontaneous radiation light generated by SOA when working under high current conditions (as shown in the figure below, taking 1342nm EML-SOA laser as an example) will cause crosstalk to EAM. The presence of these optical crosstalks will lead to the degradation of the laser's line width, side mode suppression ratio, and relative intensity noise. Especially at high-rate modulation, optical crosstalk can easily cause the laser to fall into a self-pulsation or chaotic working state, ultimately leading to distortion of the modulated signal. To solve this problem, researchers have tried to reduce the end-face light reflection, such as tilting the light-emitting end face, using a passive window on the light-emitting end face, and using a high anti-reflection film. However, these methods cannot solve the optical crosstalk problem from SOA to EAM in practical applications. Summary of the invention

[0003] The object of the present invention is to provide a laser chip and a method for preparing the same, which can at least solve some of the defects in the prior art.

[0004] To achieve the above-mentioned purpose, an embodiment of the present invention provides the following technical solution: a laser chip, comprising an electro-absorption modulator and a semiconductor optical amplifier, and also comprising a reflection grating for reflecting the spontaneous radiation light of the reflective semiconductor optical amplifier, wherein the semiconductor optical amplifier is arranged on the light-emitting side of the electro-absorption modulator, and the reflection grating is arranged in the area where the semiconductor optical amplifier is located, and the reflection grating is arranged close to the area where the electro-absorption modulator is located.

[0005] Furthermore, the reflection grating is located on the front side or the back side of the semiconductor optical amplifier.

[0006] Furthermore, the front side of the quantum well of the semiconductor optical amplifier is covered with a cladding, and the reflection grating is located in the cladding.

[0007] Furthermore, it also includes a laser light source, and the electro-absorption modulator is arranged on the light output side of the laser light source.

[0008] Furthermore, a mode selection grating is provided in the area where the laser light source is located.

[0009] Furthermore, the mode selection grating is located on the front side or the back side of the laser light source.

[0010] Furthermore, the mode-selective grating and the reflective grating have different grating periods.

[0011] Furthermore, the grating period of the reflection grating is greater than the grating period of the mode selection grating.

[0012] Furthermore, the structures of the quantum well of the laser light source and the quantum well of the semiconductor optical amplifier are the same or different.

[0013] The embodiment of the present invention provides another technical solution: a method for preparing a laser chip, comprising the following steps:

[0014] S1, epitaxially grow the electroabsorption modulator quantum well and the semiconductor optical amplifier quantum well on the substrate,

[0015] S2, a reflective grating is set in the semiconductor optical amplifier quantum well region at the junction of the electro-absorption modulator quantum well and the semiconductor optical amplifier quantum well,

[0016] S3, continue to complete the preparation of electroabsorption modulator and semiconductor optical amplifier,

[0017] S4, when the electro-absorption modulator and the semiconductor optical amplifier are working, the reflection grating reflects the spontaneous radiation light of the semiconductor optical amplifier to prevent the spontaneous radiation light from entering the electro-absorption modulator.

[0018] Compared with the prior art, the beneficial effects of the present invention are: by setting a reflection grating, the spontaneous radiation light of the semiconductor optical amplifier can be reflected, the optical crosstalk is reduced, and the signal quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of spontaneous emission optical noise of semiconductor optical amplifier;

[0020] Figure 2 A reflection spectrum of a reflection grating of a laser chip provided by an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of the structure of a laser chip provided by an embodiment of the present invention;

[0022] In the figure markings: 1-N-side electrode; 2-substrate; 3-first quantum well; 4-second quantum well; 5-mode selection grating; 6-reflection grating; 7-cladding; 8-P-side electrode; 9-electric isolation region; 10-high reflection film; 11-anti-reflection film. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1:

[0025] See also Figure 3 , an embodiment of the present invention provides a laser chip, including an electro-absorption modulator (EMA), a semiconductor optical amplifier (SOA), and a reflection grating 6 for reflecting the spontaneous radiation light of the reflective semiconductor optical amplifier, wherein the semiconductor optical amplifier is arranged on the light-emitting side of the electro-absorption modulator, and the reflection grating 6 is arranged in the area where the semiconductor optical amplifier is located, and the reflection grating 6 is arranged close to the area where the electro-absorption modulator is located. In this embodiment, by setting the reflection grating 6, the spontaneous radiation light of the semiconductor optical amplifier can be reflected, the optical crosstalk can be reduced, and the signal quality can be improved. Specifically, as Figure 1 As shown in the figure, after the electro-absorption modulated laser (EML) is integrated with the semiconductor optical amplifier (SOA), the problem of signal distortion caused by the spontaneous radiation light crosstalk of the SOA is solved. In order to solve this problem, the reflection grating 6 is directly made in the chip, which can be completed during the growth process. There is no need to change the existing chip manufacturing process, nor is there a need to use additional structures outside the chip to solve the light crosstalk problem. The final structure is the same as the existing laser chip structure, which does not affect the existing application of the chip, but can solve the light crosstalk problem and greatly improve the performance. Figure 2 shown.

[0026] See also Figure 3 , the reflection grating 6 is located on the front or back side of the semiconductor optical amplifier. In this embodiment, the reflection grating 6 can be set at the area where the semiconductor optical amplifier is located at the junction of the electro-absorption modulator and the semiconductor optical amplifier, and can be set at the front or back side of the semiconductor amplifier. Figure 3 The figure shows that it is located on the front side, that is, the top side, of the semiconductor amplifier.

[0027] See also Figure 3, the front side of the quantum well of the semiconductor optical amplifier is covered with a cladding 7, and the reflection grating 6 is located in the cladding 7. In this embodiment, the reflection grating 6 is specifically located in the cladding 7, which can be more clearly distinguished from the solution of taking measures outside the chip to solve the light crosstalk in the prior art. The design of the reflection grating 6 in the cladding 7 will not change the overall structure of the chip, nor will it change the overall growth steps. It is only necessary to add the step of growing the reflection grating 6 after the quantum well is grown, and it can also be performed together with the step of growing the mode selection grating 5, thereby improving the manufacturing efficiency.

[0028] See also Figure 3 , the chip also includes a laser light source (DFB), and the electro-absorption modulator is arranged on the light-emitting side of the laser light source. In this embodiment, the laser light source is on the left side of the electro-absorption modulator, and the semiconductor optical amplifier is on the right side of the electro-absorption modulator. Preferably, a mode selection grating 5 is provided in the area where the laser light source is located. The mode selection grating 5 is designed to be used for the working mode selection of the laser light source. The mode selection grating 5 can be located above the quantum well of the laser light source or below the quantum well of the laser light source, such as Figure 3 Shown is placed above the laser light source quantum well.

[0029] See also Figure 2 and Figure 3 , the grating period of the mode selection grating 5 is different from that of the reflection grating 6, and the grating period of the reflection grating 6 is greater than that of the mode selection grating 5. Specifically, the grating period of the mode selection grating 5 is different from that of the reflection grating 6, and the grating period of the reflection grating 6 is greater than that of the mode selection grating 5, and the reflection grating 6 has an extremely low reflectivity at the laser lasing wavelength, and the reflectivity may be less than 0.1%. Preferably, the overall length of the reflection grating 6 region is 10 to 30 um, and the reflection spectrum of the reflection grating 6 is as follows: Figure 2 As shown (taking 1342nm EML-SOA laser as an example).

[0030] See also Figure 3 , the quantum well of the laser light source and the quantum well of the semiconductor optical amplifier may have the same or different structures. Figure 3 The DFB quantum well has the same structure as the SOA quantum well, and is defined as the first quantum well 3 for the convenience of marking and distinguishing. The EAM quantum well may have another structure, and is defined as the second quantum well 4 for the convenience of marking and distinguishing.

[0031] See also Figure 3, the subsequent chip can be designed as a buried heterojunction structure or a ridge waveguide structure according to the conventional semiconductor laser manufacturing process. The cladding 7 is above the laser chip. After the waveguide structure is completed, the electrical isolation area 9 is made, the BCB is made, the P-side electrode 8 is made (including DFB electrode, EAM electrode and SOA electrode), thinning and polishing, and the N-side electrode 1 is made. After stripping, the end face of the chip close to the DFB area is coated with a high-reflection film 10, and the end face close to the SOA area is coated with an anti-reflection film 11 layer.

[0032] Embodiment 2:

[0033] See also Figure 3 , an embodiment of the present invention provides a method for preparing a laser chip, comprising the following steps: S1, epitaxially growing an electro-absorption modulator quantum well and a semiconductor optical amplifier quantum well on a substrate 2, S2, setting a reflection grating 6 in the semiconductor optical amplifier quantum well region at the junction of the electro-absorption modulator quantum well and the semiconductor optical amplifier quantum well, S3, continuing to complete the preparation of the electro-absorption modulator and the semiconductor optical amplifier, S4, when the electro-absorption modulator and the semiconductor optical amplifier are working, the reflection grating 6 reflects the spontaneous radiation light of the semiconductor optical amplifier to prevent the spontaneous radiation light from entering the electro-absorption modulator. In this embodiment, by setting the reflection grating 6, the spontaneous radiation light of the semiconductor optical amplifier can be reflected, the optical crosstalk can be reduced, and the signal quality can be improved. Specifically, as Figure 1 As shown in the figure, after the electro-absorption modulated laser (EML) is integrated with the semiconductor optical amplifier (SOA), the problem of signal distortion caused by the spontaneous radiation light crosstalk of the SOA is solved. In order to solve this problem, the reflection grating 6 is directly made in the chip, which can be completed during the growth process. There is no need to change the existing chip manufacturing process, nor is there a need to use additional structures outside the chip to solve the light crosstalk problem. The final structure is the same as the existing laser chip structure, which does not affect the existing application of the chip, but can solve the light crosstalk problem and greatly improve the performance. Figure 2 shown.

[0034] As an optimization solution of the embodiment of the present invention, please refer to Figure 3 , the subsequent chips can be designed as buried heterojunction structures or ridge waveguide structures according to the conventional semiconductor laser manufacturing process. The cladding 7 is above the laser chip. After the waveguide structure is completed, the electrical isolation area 9 is made, BCB (Benzocyclobutene is an active resin, the chemical name is benzocyclobutene resin) is made, the P-side electrode 8 is made (including DFB electrode, EAM electrode and SOA electrode), thinning and polishing, and the N-side electrode 1 is made. After stripping, the end face of the chip close to the DFB area is coated with a high reflection film 10, and the end face close to the SOA area is coated with an anti-reflection film 11 layer.

[0035] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser chip, comprising an electro-absorption modulator and a semiconductor optical amplifier, characterized in that: It also includes a reflection grating for reflecting the spontaneous radiation light of the reflective semiconductor optical amplifier. The semiconductor optical amplifier is arranged on the light output side of the electro-absorption modulator. The reflection grating is arranged in the area where the semiconductor optical amplifier is located, and the reflection grating is arranged close to the area where the electro-absorption modulator is located.

2. The laser chip according to claim 1, characterized in that: The reflection grating is located on the front side or the back side of the semiconductor optical amplifier.

3. The laser chip according to claim 1, characterized in that: The front side of the quantum well of the semiconductor optical amplifier is covered with a cladding, and the reflection grating is located in the cladding.

4. The laser chip according to claim 1, characterized in that: It also includes a laser light source, and the electro-absorption modulator is arranged on the light-emitting side of the laser light source.

5. The laser chip according to claim 4, characterized in that: A mode selection grating is provided in the area where the laser light source is located.

6. The laser chip according to claim 5, characterized in that: The mode selection grating is located on the front side or the back side of the laser light source.

7. The laser chip according to claim 5, characterized in that: The mode-selective grating and the reflection grating have different grating periods.

8. The laser chip according to claim 7, characterized in that: The grating period of the reflection grating is greater than the grating period of the mode selection grating.

9. The laser chip according to claim 4, characterized in that: The structures of the quantum well of the laser light source and the quantum well of the semiconductor optical amplifier are the same or different.

10. A method for preparing a laser chip, characterized in that: The steps include: S1, epitaxially grow the electroabsorption modulator quantum well and the semiconductor optical amplifier quantum well on the substrate, S2, a reflective grating is set in the semiconductor optical amplifier quantum well region at the junction of the electro-absorption modulator quantum well and the semiconductor optical amplifier quantum well, S3, continue to complete the preparation of electroabsorption modulator and semiconductor optical amplifier, S4, when the electro-absorption modulator and the semiconductor optical amplifier are working, the reflection grating reflects the spontaneous radiation light of the semiconductor optical amplifier to prevent the spontaneous radiation light from entering the electro-absorption modulator.

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