Optical Modulation Amplification Device, Optical Module, Optical Network Unit, and Optical Communication System

Abstract

An optical modulation and amplification device (1201), an optical module (1301), an optical network unit (2) and an optical communication system are provided to realize that the optical modulation and amplification device (1201) is insensitive to polarization. The optical modulation and amplification device (1201) includes an electroabsorption modulator (10) and a semiconductor optical amplifier (20). The electroabsorption modulator (10) and the semiconductor optical amplifier (20) share the same substrate (40) and the same multilayer material structure (50). The multilayer material structure (50) includes, from bottom to top, at least a first quantum well (504), an electron blocking layer (505), a second quantum well (506) and an upper separate confinement layer (507). The electroabsorption modulator (10) is configured to modulate the injected light using the first quantum well (504), and the semiconductor optical amplifier (20) is configured to amplify the injected light using the second quantum well (506). If the thickness of the upper separate confinement layer (507) and the stress of the first quantum well (504) meet the design requirements, the electroabsorption modulator (10) can be insensitive to polarization. If the thickness of the upper separate confinement layer (507) and the stress of the second quantum well (506) meet the design requirements, the semiconductor optical amplifier (20) can be insensitive to polarization.

Description

Technical Field

[0001] [Technical Field] The present application relates to the field of optical communication, and more particularly to an optical modulation amplification device, an optical module, an optical network unit, and an optical communication system.

Background Art

[0002] In a current time-division multiple access passive optical network (TDMA-PON), an optical network unit (ONU) transmits an upstream optical signal in an assigned slot, and an optical line terminal (OLT) simultaneously transmits a downstream optical signal to a plurality of ONUs in a broadcast manner, and each ONU selectively receives the downstream optical signal. In this time-division multiplexing method, it is difficult to increase the effective bandwidth of a single ONU.

[0003] To meet the requirements of rate improvement, optical signals transmitted by a plurality of ONUs need to share the same wavelength. Specifically, in each ONU, an electro-absorption modulator and an optical amplifier may be arranged to modulate and amplify remotely injected light in order to achieve wavelength locking. However, the remotely injected light transmitted by the OLT may be affected by environmental changes (such as stress and temperature of the optical fiber) during the transmission process. As a result, the polarization direction of the injected light reaching the ONU becomes random, affecting the performance of the ONU.

Summary of the Invention

[0004] Embodiments of the present application provide an optical modulation amplification device, an optical module, an optical network unit, and an optical communication system, and the optical modulation amplification device is insensitive to polarization.

[0005] According to the first aspect, an embodiment of the present application provides an optical modulation and amplification device including an electro-absorption modulator and a semiconductor optical amplifier. The electro-absorption modulator is electrically separated from the semiconductor optical amplifier. The first waveguide of the electro-absorption modulator and the second waveguide of the semiconductor optical amplifier are coupled in series in the transmission direction of the injected light. The first waveguide and the second waveguide each use a ridge waveguide structure. The electro-absorption modulator and the semiconductor optical amplifier share the same substrate, and the electro-absorption modulator and the semiconductor optical amplifier use the same multilayer material structure. The multilayer material structure is disposed on the substrate, and the multilayer material structure includes a first quantum well, an electron blocking layer, a second quantum well, and an upper confinement layer from bottom to top. The first quantum well is used to modulate the injected light. The second quantum well is used to amplify the injected light. The electron blocking layer is used to block the current loaded in the second quantum well from flowing into the first quantum well. There is a first difference between the extinction ratio corresponding to the transverse electric (TE) mode and the extinction ratio corresponding to the transverse magnetic (TM) mode in the electro-absorption modulator. The first difference depends on the thickness of the upper confinement layer and the stress of the first quantum well, and the first difference is not more than a first preset value. There is a second difference between the modal gain corresponding to the TE mode and the modal gain corresponding to the TM mode in the semiconductor optical amplifier. The second difference depends on the thickness of the upper confinement layer and the stress of the second quantum well, and the second difference is not more than a second preset value.

[0006] In this implementation, when the thickness of the upper confinement layer and the stress of the first quantum well meet the design requirements, the extinction ratio corresponding to the TE mode and the extinction ratio corresponding to the TM mode in the electro-absorption modulator are close to or equal to each other, that is, the electro-absorption modulator is insensitive to polarization. When the thickness of the upper confinement layer and the stress of the second quantum well meet the design requirements, the modal gain of the TE mode and the modal gain of the TM mode in the semiconductor optical amplifier are close to or equal to each other, that is, the semiconductor optical amplifier is insensitive to polarization. Therefore, even if the polarization direction of the injected light is random, it does not affect the performance of the optical modulation and amplification device, that is, the optical modulation and amplification device provided in the present application is insensitive to polarization. Also, according to the design method provided in the present application, the electro-absorption modulator and the semiconductor optical amplifier are grown on the same substrate. Thereby, the number of material epitaxy times is reduced and the process is simplified.

[0007] In some possible implementations, there is a third difference between the optical confinement coefficient of the TE mode and the optical confinement coefficient of the TM mode in the first quantum well. There is a fourth difference between the material absorption coefficient of the TE mode and the material absorption coefficient of the TM mode in the first quantum well. The first difference depends on the third difference and the fourth difference, the third difference depends on the thickness of the upper confinement layer, and the fourth difference depends on the stress of the first quantum well. The third difference is less than or equal to a third preset value, and the fourth difference is less than or equal to a fourth preset value. In this implementation, in order to enhance the feasibility of this solution, the parameters affected by the thickness of the upper confinement layer and the first quantum well are described in detail.

[0008] In some possible implementations, there is a fifth difference between the optical confinement factor of the TE mode and the optical confinement factor of the TM mode in the second quantum well. There is a sixth difference between the material gain of the TE mode and the material gain of the TM mode in the second quantum well. The first difference depends on the fifth difference and the sixth difference, the fifth difference depends on the thickness of the upper separation confinement layer, and the sixth difference depends on the stress of the second quantum well. The fifth difference is less than or equal to a fifth preset value, and the sixth difference is less than or equal to a sixth preset value. In this implementation, in order to enhance the feasibility of this solution, the parameters affected by the thicknesses of the upper separation confinement layer and the second quantum well are described in detail respectively.

[0009] In some possible implementations, on the premise that the material absorption coefficient of the first quantum well is fixed, in order to obtain a high absorption coefficient, the electro-absorption modulator needs to have a higher High optical confinement factor in the first quantum well. In order to obtain a high output power, the semiconductor optical amplifier needs to have a low optical confinement factor in the second quantum well. In this design method, different requirements for the electro-absorption modulator and the semiconductor optical amplifier with respect to the optical confinement factor can be realized in the same structure.

[0010] In some possible implementations, the multilayer material structures on both sides of the semiconductor optical amplifier using the second waveguide as the axis are symmetric. In other words, the thickness distribution of each layer of the material structure is uniform. In this way, by restricting the thickness of the upper separation confinement layer so that the upper separation confinement layer is not too thick, the optical confinement factors of the first quantum well and the second quantum well can be defined separately.

[0011] In some possible implementations, the multilayer material structures on both sides of the electro-absorption modulator using the first waveguide as the axis are etched to form a deep ridge waveguide structure. This reduces the influence of the parasitic capacitance and the junction capacitance on the electro-absorption modulator.

[0012] In some possible implementations, the etching region on the electro-absorption modulator is filled with a low dielectric constant material such as polyimide or benzocyclobutene to further reduce the influence of the parasitic capacitance and the junction capacitance on the electro-absorption modulator.

[0013] In some possible implementations, the thickness H of the upper isolation confinement layer satisfies 75 nm ≤ H ≤ 95 nm, and the optical confinement coefficients of the TE mode and the TM mode in the first quantum well and the second quantum well are close to or equal to each other.

[0014] In some possible implementations, the length L of the first waveguide satisfies L ≤ 400 μm. Specifically, since the total length of the electro-absorption modulator is 400 μm or less, the light absorbed by the first quantum well of the electro-absorption modulator can be reduced, and there is an optical confinement coefficient in the first quantum well. Is high exists.

[0015] In some possible embodiments, the width W of the ridge waveguide structures of both the first waveguide and the second waveguide satisfies 1.5 μm ≤ W ≤ 3 μm. It should be understood that the manufacturing method using the ridge waveguide structure is simpler compared to the manufacturing method using the buried heterostructure waveguide.

[0016] In some possible implementations, the optical modulation and amplification device further includes a controller, a voltage source, and a current source. The controller is configured to load the voltage output by the voltage source onto the electro-absorption modulator and control the voltage source to modulate the injected light. The controller is configured to load the current output by the current source onto the semiconductor optical amplifier and control the current source to amplify the injected light. In this implementation, in order to improve the practicality of this solution, the operating mode of the optical modulation and amplification device in the present application is described.

[0017] In some possible implementations, a groove is arranged between the electrodes of the electro-absorption modulator and the electrodes of the semiconductor optical amplifier, and the groove increases the insulation resistance between the electro-absorption modulator and the semiconductor optical amplifier, realizing electrical insulation between the electro-absorption modulator and the semiconductor optical amplifier.

[0018] In some possible implementations, protons or inert ions are further injected into the groove, and the electrical insulation effect can be improved.

[0019] In some possible implementations, protons or inert ions are injected between the electrodes of the electro-absorption modulator and the electrodes of the semiconductor optical amplifier to achieve electrical insulation between the electro-absorption modulator and the semiconductor optical amplifier. Compared with the design method of arranging grooves, the flexibility of this solution is improved.

[0020] According to a second aspect, an embodiment of the present application provides an optical module including an optical modulation amplification device according to any embodiment of the first aspect and a driver. The driver is configured to drive the optical modulation amplification device to modulate and amplify the injected light.

[0021] According to a third aspect, an embodiment of the present application provides an optical network unit ( O NU), and the ONU includes an optical module according to the second aspect and a media access control ( M AC) chip. The optical module is configured to convert an electrical signal output by the MAC chip into an optical signal.

[0022] According to a fourth aspect, an embodiment of the present application provides an optical communication system including an optical line terminal device ( O LT) and an ONU according to the third aspect. Specifically, the OLT is configured to transmit the injected light to the ONU.

[0023] In an embodiment of the present application, the optical modulation amplifier includes an electro-absorption modulator and a semiconductor optical amplifier, and the electro-absorption modulator and the semiconductor optical amplifier share the same substrate and the same multilayer material structure. When the thickness of the upper confinement layer and the stress of the first quantum well meet the design requirements, the extinction ratio corresponding to the TE mode and the extinction ratio corresponding to the TM mode in the electro-absorption modulator are close to or equal to each other, that is, the electro-absorption modulator is insensitive to polarization. When the thickness of the upper confinement layer and the stress of the second quantum well meet the design requirements, the modal gain of the TE mode and the modal gain of the TM mode in the semiconductor optical amplifier are close to or equal to each other, that is, the semiconductor optical amplifier is insensitive to polarization. Therefore, even if the polarization direction of the injected light is random, it does not affect the performance of the optical modulation amplifier, that is, the optical modulation amplifier provided in the present application is insensitive to polarization. Further, according to the design method provided in the present application, the electro-absorption modulator and the semiconductor optical amplifier are grown on the same substrate. Thereby, the number of material epitaxy times is reduced and the process is simplified.

Brief Description of Drawings

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Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5A

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Figure 5B

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Figure 6

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Figure 7A

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Figure 7B

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Figure 8

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Figure 9

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Figure 10

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Figure 11

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Figure 12

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Figure 13

Embodiments for Carrying Out the Invention

[0039] Embodiments of the present application provide an optical modulation amplification device, an optical module, an optical network unit, and an optical communication system, and the optical modulation amplification device is insensitive to polarization.

[0040] The present application is mainly applied to an optical communication system of a passive optical network (PON). First, the PON system will be described.

[0041] FIG. 1 is a schematic structural diagram of a PON system. The network devices of the PON system include an optical line terminal device ( O OLT) 1 and an optical network unit ( O ONU) 2. An optical distribution network ( O ODN) 3 is arranged between the optical line terminal device 1 and the optical network unit 2. An optical module is arranged in each of the optical line terminal device 1 and the optical network unit 2.

[0042] Note that in order to meet the requirements of rate improvement, the optical signals transmitted by multiple ONUs need to share the same wavelength. This can be specifically implemented by the ONU via remote optical injection locking. However, the remote injection light transmitted by the OLT may be affected by environmental changes (e.g., stress and temperature of the optical fiber) during the transmission process. As a result, the polarization direction of the injection light reaching the ONU becomes random, affecting the performance of the ONU. Therefore, the present application provides an optical modulation amplification device applied to the optical module in the ONU. Even if the polarization direction of the injection light is random, the performance of the optical modulation amplification device is not affected. That is, the optical modulation amplification device provided in the present application is insensitive to polarization. Next, the optical modulation amplification device provided in the present application will be described in detail.

[0043] FIG. 2 is a first schematic structural diagram of an optical modulation amplifier according to an embodiment of the present application. As shown in FIG. 2, the optical modulation amplifier includes an electro-absorption modulator 10 and a semiconductor optical amplifier 20. The electro-absorption modulator 10 is configured to modulate the injection light from the remote end. The semiconductor optical amplifier 20 is configured to amplify the injection light. In a first possible implementation, the injection light can be injected from the end face of the electro-absorption modulator 10, transmitted through the waveguide 30, and then output from the end face of the semiconductor optical amplifier 20. That is, first, the injection light is modulated using the electro-absorption modulator 10, and then the modulated injection light is amplified using the semiconductor optical amplifier 20. In a second possible implementation, it is also conceivable that the injection light is injected from the end face of the semiconductor optical amplifier 20, transmitted through the waveguide 30, and then output from the end face of the electro-absorption modulator 10. That is, first, the injection light can be amplified using the semiconductor optical amplifier 20, and then the amplified injection light can be modulated using the electro-absorption modulator 10. In the two foregoing embodiments, an anti-reflective (AR) film may be plated on both the end face of the electro-absorption modulator 10 and the end face of the semiconductor optical amplifier 20 to increase the incident light power and the output light power. In a third possible implementation, the injection light is injected from one end face of the electro-absorption modulator 10 or the semiconductor optical amplifier 20. After being transmitted to the other end face through the waveguide 30, the injection light is reflected, and after being transmitted through the waveguide 30, the injection light is output from the end face where the injection light is injected. That is, the injection light is modulated and amplified twice in the reciprocating process. The end faces used for optical injection and optical output are plated with an AR film, and the end faces used for optical reflection can be plated with a highly reflective (HR) film.

[0044] The electro-absorption modulator 10 is electrically separated from the semiconductor optical amplifier 20. The first waveguide of the electro-absorption modulator 10 and the second waveguide of the semiconductor optical amplifier 20 are coupled in series in the transmission direction of the injected light. The serially coupled first waveguide and second waveguide are located at the position shown by the waveguide 30 in FIG. 2. Also, the first waveguide of the electro-absorption modulator 10 and the second waveguide of the semiconductor optical amplifier 20 each use the ridge waveguide structure shown in FIG. 2. Preferably, the width W of the ridge waveguide structure satisfies 1.5 μm ≤ W ≤ 3 μm. It should be understood that the manufacturing method using the ridge waveguide structure is simpler compared to the manufacturing method using the buried hetero-structure waveguide.

[0045] The electro-absorption modulator 10 and the semiconductor optical amplifier 20 share the same substrate 40. Furthermore, the electro-absorption modulator 10 and the semiconductor optical amplifier 20 use the same multi-layer material structure 50. The multi-layer material structure 50 is disposed on the substrate 40. It should be understood that both the electro-absorption modulator 10 and the semiconductor optical amplifier 20 are manufactured based on the substrate 40. The electro-absorption modulator 10 is not limited to the portion grown on the substrate 40, and the substrate 40 is also part of the electro-absorption modulator 10. Similarly, the semiconductor optical amplifier 20 is not limited to the portion grown on the substrate 40, and the substrate 40 is also part of the semiconductor optical amplifier 20. That is, the electro-absorption modulator 10, the semiconductor optical amplifier 20, and the substrate 40 constitute a monolithic integrated structure. Hereinafter, the detailed configuration of the multi-layer material structure 50 will be described.

[0046] FIG. 3 is a first side view of an optical modulation amplification device according to an embodiment of the present application. The multilayer material structure 50 includes at least a first quantum well 504, an electron blocking layer 505, a second quantum well 506, and an upper confinement layer 507 from bottom to top. The absorption coefficient of the first quantum well 504 changes with the applied voltage. Therefore, the intensity of the injected light can be adjusted by adjusting the voltage applied to the first quantum well 504. By applying a current to the second quantum well 506, gain can be provided to the injected light. The electron blocking layer 505 is configured to block the current applied to the second quantum well 506 from flowing into the first quantum well 504. The second quantum well 506 has a high carrier concentration and provides high gain to the injected light. The first quantum well 504 has no current injection and thus does not provide gain. The upper confinement layer 507 is configured to confine the light within the quantum well.

[0047] In actual applications, it should be understood that the multilayer material structure is not limited to the above-described structure. In a possible implementation, as shown in FIG. 3, the multilayer material structure includes, in order from bottom to top, a buffer layer 501, an inner N-cladding 502, a lower confinement layer 503, a first quantum well 504, an electron blocking layer 505, a second quantum well 506, an upper confinement layer 507, and an inner P-cladding 508.

[0048] Note that the electro-absorption modulator 10 and the semiconductor optical amplifier 20 use the same multilayer material structure 50. However, when the electro-absorption modulator 10 operates, the electro-absorption modulator 10 modulates the injected light using only the first quantum well 504 and does not use the second quantum well 506, which is different. When the semiconductor optical amplifier 20 operates, the semiconductor optical amplifier 20 amplifies the injected light using only the second quantum well 506 without using the first quantum well 504. Next, the operation methods of the electro-absorption modulator 10 and the semiconductor optical amplifier 20 will be described using specific implementation examples.

[0049] FIG. 4 is a second schematic configuration diagram of an optical modulation amplifier according to an embodiment of the present application. In some possible implementations, the optical modulation amplifier further includes a voltage source 60, a current source 70, and a controller 80. The P-type electrode 101 is disposed on the upper surface of the electro-absorption modulator 10. The P-type electrode 201 is disposed on the upper surface of the semiconductor optical amplifier 20. The N-type electrode 401 is disposed on the lower surface of the substrate 40. The controller 80 is configured to control the voltage source 60 to load an output voltage onto the P-type electrode 101 and the N-type electrode 401 of the electro-absorption modulator 10. Specifically, a voltage can be injected into the first quantum well 504 to modulate the injected light. The controller 80 is further configured to control the current source 70 to load an output current onto the P-type electrode 201 and the N-type electrode 401 of the semiconductor optical amplifier 20. Specifically, a current can be injected into the second quantum well 506 to amplify the injected light.

[0050] It should be understood that the injected light in the electro-absorption modulator and the semiconductor optical amplifier may be in a transverse electric ( T E) mode and a transverse magnetic ( T M) mode. In order to realize that the semiconductor optical amplifier has polarization insensitivity, the modal gains of the TE mode and the TM mode in the semiconductor optical amplifier need to be close to or equal to each other. This can be specifically realized by adjusting the thickness of the upper confinement layer and the stress of the second quantum well. In order to realize that the electro-absorption modulator has polarization insensitivity, the extinction ratio corresponding to the TE mode and the extinction ratio corresponding to the TM mode in the electro-absorption modulator need to be close to or equal to each other. This can be specifically realized by adjusting the thickness of the upper confinement layer and the stress of the first quantum well. Specific details will be described below.

[0051] 1. The semiconductor optical amplifier has polarization insensitivity.

[0052] The thickness of the upper confinement layer can affect the optical confinement factor of the TE mode and the TM mode in the second quantum well. The optical confinement factor is a parameter used to measure the confinement effect of the second quantum well on light. When the thickness of the upper confinement layer meets certain conditions, the optical confinement factor of the TE mode and the TM mode in the second quantum well are close to or equal to each other. Therefore, the confinement effect of the second quantum well on TE mode light is similar to or equivalent to that on TM mode light. The following provides an explanation using examples.

[0053] Figure 5A is a diagram showing the changing trend of the optical confinement factor in the second quantum well having the thickness of the upper confinement layer. Figure 5B is a diagram showing the changing trend of the ratio of the difference between the optical confinement factors of the TE mode and the TM mode in the second quantum well having the thickness of the upper confinement layer. As shown in Figure 5A, the horizontal axis represents the thickness of the upper confinement layer, and the vertical axis represents the optical confinement factor in the second quantum well. When the thickness of the upper confinement layer is 85 nm, it can be seen that the optical confinement factor of the TE mode and the TM mode are equal to each other, both being 2.91%. As shown in Figure 5B, the horizontal axis represents the thickness of the upper confinement layer, and the vertical axis represents the ratio of the difference between the optical confinement factors of the TE mode and the TM mode in the second quantum well. Also, when the thickness of the upper confinement layer is 85 nm, the ratio of the difference between the optical confinement factors of the TE mode and the TM mode in the second quantum well is 0, that is, it can be seen that the optical confinement factor of the TE mode is equal to the optical confinement factor of the TM mode. It should be understood that in actual applications, the thickness H of the upper confinement layer shall satisfy 75 nm ≤ H ≤ 95 nm.

[0054] It should be understood that on the premise that the optical confinement factor of the TE mode and the optical confinement factor of the TM mode in the second quantum well are close to or equal to each other, the material gains of the TE mode and the TM mode in the second quantum well need to be close to or equal to each other. Thus, in a semiconductor optical amplifier, the modal gains of the TE mode and the TM mode are close to or equal to each other. In particular, the stress in the second quantum well may affect the material gains of the TE mode and the TM mode. Therefore, when the stress in the second quantum well satisfies certain conditions, since the material gains of the TE mode and the TM mode are close to or equal to each other, the modal gains of the TE mode and the TM mode are close to or equal to each other. FIG. 6 is a schematic diagram of the modal gains of the TE mode and the TM mode in a semiconductor optical amplifier under different injection current conditions. As shown in FIG. 6, the horizontal axis represents the wavelength and the vertical axis represents the modal gain. In the wavelength band of 1510 nm to 1535 nm, since the modal gains of the TE mode and the TM mode are close to or equal to each other, it can be seen that the semiconductor optical amplifier is insensitive to polarization.

[0055] 2. The electro-absorption modulator is insensitive to polarization.

[0056] Similar to the second quantum well, the thickness of the upper separate confinement layer can also affect the optical confinement factor of the TE mode and the optical confinement factor of the TM mode in the first quantum well. When the thickness of the upper separate confinement layer satisfies certain conditions, the optical confinement factor of the TE mode and the optical confinement factor of the TM mode in the first quantum well are close to or equal to each other. Therefore, the confinement effect of the first quantum well on the TE-mode light is similar to or equivalent to that on the TM-mode light. The following provides an explanation using examples.

[0057] FIG. 7A is a diagram showing the tendency of change in the optical confinement factor in the first quantum well having the thickness of the upper separate confinement layer. FIG. 7B is a diagram showing the tendency of change in the ratio of the difference in the optical confinement factors between the TE mode and the TM mode in the first quantum well having the thickness of the upper separate confinement layer. As shown in FIG. 7A, the horizontal axis represents the thickness of the upper separate confinement layer, and the vertical axis represents the optical confinement factor in the first quantum well. It can be seen that the optical confinement factor of the TE mode and the optical confinement factor of the TM mode in the first quantum well increase as the thickness of the upper separate confinement layer increases. When the thickness of the upper separate confinement layer is 85 nm, the optical confinement factor of the TE mode in the first quantum well is 10.3%, and the optical confinement factor of the TM mode in the first quantum well is 10.5%. As shown in FIG. 7B, the horizontal axis represents the thickness of the upper separate confinement layer, and the vertical axis represents the ratio of the difference in the optical confinement factors between the TE mode and the TM mode in the first quantum well. It can be seen that the ratio of the difference in the optical confinement factors between the TE mode and the TM mode in the first quantum well decreases as the thickness of the upper separate confinement layer decreases. When the thickness of the upper separate confinement layer is 85 nm, the ratio of the difference in the optical confinement factors between the TE mode and the TM mode in the first quantum well is close to 2.2%.

[0058] It should be understood that on the premise that the optical confinement factor of the TE mode and the optical confinement factor of the TM mode in the first quantum well are close to or equal to each other, the material absorption coefficients of the TE mode and the TM mode in the first quantum well need to be close to or equal to each other. Therefore, the extinction ratio corresponding to the TE mode and the extinction ratio corresponding to the TM mode in the electro-absorption modulator are close to or equal to each other. In particular, the stress of the first quantum well may affect the material absorption coefficients of the TE mode and the TM mode. Therefore, when the stress of the first quantum well meets certain conditions, the material absorption coefficients of the TE mode and the TM mode are close to or equal to each other, so the extinction ratio corresponding to the TE mode and the extinction ratio corresponding to the TM mode are close to or equal to each other. FIG. 8 is a schematic diagram of the extinction ratios corresponding to the TE mode and the TM mode in the electro-absorption modulator under different applied voltage conditions. As shown in FIG. 8, the abscissa represents the wavelength and the ordinate represents the extinction ratio. In the wavelength band of 1480 nm to 1550 nm, since the extinction ratio corresponding to the TE mode and the extinction ratio corresponding to the TM mode are close to or equal to each other, it can be seen that the electro-absorption modulator is insensitive to polarization.

[0059] In an embodiment of the present application, the optical modulation amplification device includes an electro-absorption modulator and a semiconductor optical amplifier that share the same substrate and the same multilayer material structure. When the thickness of the upper separation confinement layer 507 and the stress of the first quantum well 504 meet the design requirements, the electro-absorption modulator is insensitive to polarization. When the thickness of the upper separation confinement layer 507 and the stress of the second quantum well 506 meet the design requirements, the semiconductor optical amplifier is insensitive to polarization. Therefore, even if the polarization direction of the injected light is random, it does not affect the performance of the optical modulation amplification device, that is, the optical modulation amplification device provided in the present application is insensitive to polarization. Also, according to the design method provided in the present application, the electro-absorption modulator and the semiconductor optical amplifier are grown on the same substrate. Thereby, the number of material epitaxy times is reduced and the process is simplified.

[0060] Optionally, in some implementations, on the premise that the material absorption coefficient of the first quantum well is fixed, in order to obtain a high absorption coefficient, the electro-absorption modulator is in the first quantum well HighIt is necessary to have an optical confinement factor. To obtain high output power, the semiconductor optical amplifier needs to have a small optical confinement factor in the second quantum well. Therefore, the material refractive index of the first quantum well must be larger than that of the second quantum well. For example, the first quantum well is made of AlGaInAs Of material, and the second quantum well is made of InGaAsP Of material. Figure 9 is a schematic diagram of the refractive index distribution along the thickness direction of the multilayer structure material. As shown in Figure 9, the abscissa is the thickness of the multilayer structure material, and the ordinate is the refractive index. From the reference numerals corresponding to the multilayer material structure shown in Figure 3, it can be seen that the refractive index of the first quantum well 504 is larger than that of the second quantum well 506. In this design method, different requirements for the electro-absorption modulator and the semiconductor optical amplifier with respect to the optical confinement factor can be realized with the same structure.

[0061] Based on this, in order to further realize that there is an optical confinement factor in the first quantum well High the overall length of the electro-absorption modulator can be reduced to reduce the light absorbed by the first quantum well of the electro-absorption modulator. For example, the overall length of the electro-absorption modulator or the length L of the first waveguide is 400 μm or less.

[0062] Optionally, in some implementations, with the ridge waveguide structure of the second waveguide as the axis, the multilayer material structures on both sides of the semiconductor optical amplifier are symmetric. In other words, the thickness distribution of each layer of the material structure is uniform. In this way, by restricting the thickness of the upper separation confinement layer so that the upper separation confinement layer is not too thick, the optical confinement factors of the first quantum well and the second quantum well can be defined separately. As can be seen from Figure 5A, when the thickness of the upper separation confinement layer is large, the difference between the optical confinement factor of the TE mode and the optical confinement factor of the TM mode becomes large, and it may become difficult to realize polarization insensitivity. Also, when the thickness of the upper separation confinement layer is large, the optical confinement factor of the second quantum well can Highly become. This does not contribute to obtaining high output power by the semiconductor optical amplifier.

[0063] As an option, in some implementations, the multilayer material structures on both sides of an electro-absorption modulator using the ridge waveguide structure of the first waveguide as an axis are etched to form a deep ridge waveguide structure. This reduces the influence of parasitic capacitance and junction capacitance on the electro-absorption modulator. For example, FIG. 10 is a second side view of an optical modulation and amplification device according to an embodiment of the present application. As shown in FIG. 10, the width W of the ridge waveguide structure is 2 μm, and the first quantum well 504, electron blocking layer 505, second quantum well 506, upper confinement layer 507, and internal P-clad 508 on both sides of the ridge waveguide structure are etched. It should be understood that in actual applications, the etching depth can be selected based on actual requirements. For example, the multilayer material structure on the buffer layer 501 on both sides of the ridge waveguide structure can also be etched.

[0064] Based on this, in order to further reduce the influence of parasitic capacitance and junction capacitance on the electro-absorption modulator, a low dielectric constant material such as polyimide or benzocyclobutene can be further filled in the etching region. FIG. 11 is a third schematic configuration diagram of an optical modulation and amplification device according to an embodiment of the present application. As shown in FIG. 11, the low dielectric constant material 90 is filled in the etching region of the electro-absorption modulator 10.

[0065] In this embodiment, the electrical insulation between the electro-absorption modulator and the semiconductor optical amplifier can be implemented by a plurality of methods described separately below.

[0066] In the first method, protons or inert ions are injected between the electro-absorption modulator and the P-type electrode of the semiconductor optical amplifier to achieve electrical insulation between the electro-absorption modulator and the semiconductor optical amplifier. The inert ions may be helium, neon, argon, or other ions. It should be understood that in order to make the overall structure of the optical modulation and amplification device in the present application more compact and reduce interference, it is necessary to control the distance between the electro-absorption modulator and the P-type electrode of the semiconductor optical amplifier within a predetermined distance range.

[0067] As a second method, a groove may be provided between the electro-absorption modulator and the semiconductor optical amplifier. For example, a part of the ridge waveguide structure is etched between the electro-absorption modulator and the semiconductor optical amplifier to form a groove. The groove increases the insulation resistance between the electro-absorption modulator and the semiconductor optical amplifier, and realizes electrical insulation between the electro-absorption modulator and the semiconductor optical amplifier. Note that when electrical insulation between the electro-absorption modulator and the semiconductor optical amplifier can be realized and the normal operation of the electro-absorption modulator and the semiconductor optical amplifier is not affected, the depth of the groove is not limited in the present application. As an option, in order to improve the electrical insulation effect, protons or inert ions can be further implanted into the groove.

[0068] The optical modulation and amplification device provided in the present application is as described above. Based on this, an embodiment of the present application further provides an optical module. FIG. 12 is a schematic structural diagram of an optical module according to an embodiment of the present application. The optical module includes the optical modulation and amplification device 1201 and the driver 1202 described in the above embodiment. The driver is configured to drive the optical modulation and amplification device to modulate and amplify the injected light.

[0069] Furthermore, an embodiment of the present application provides an ONU. FIG. 13 is a schematic structural diagram of an ONU according to an embodiment of the present application. The ONU includes the optical module 1301 and the MAC chip 1302 described in the embodiment shown in FIG. 12. The optical module 1301 is configured to convert an electrical signal output by the MAC chip 1302 into an optical signal. It should be understood that the ONU is applied to a PON system. The light source in the OLT transmits the injected light to the ONU, and the injected light is continuous light. The ONU uses the optical modulation and amplification device in the optical module of the ONU to modulate and amplify the injected light to generate an upstream optical signal. Then, the ONU sends the upstream optical signal to the OLT.

[0070] It should be noted that the foregoing embodiments are merely used to explain the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions described in the foregoing embodiments without departing from the scope of the technical solutions of the embodiments of the present application, or make equivalent substitutions for some of its technical features.

Claims

Claim 1 An optical modulation amplification device, wherein the optical modulation amplification device includes an electro-absorption modulator and a semiconductor optical amplifier, the electro-absorption modulator is electrically insulated from the semiconductor optical amplifier, a first waveguide of the electro-absorption modulator and a second waveguide of the semiconductor optical amplifier are coupled in series in the transmission direction of the injected light, and the first waveguide and the second waveguide each use a ridge waveguide structure. The electro-absorption modulator and the semiconductor optical amplifier share the same substrate and the same first electrode disposed under the substrate, the electro-absorption modulator and the semiconductor optical amplifier use the same multilayer material structure, the multilayer material structure is disposed on the substrate, the multilayer material structure includes a first quantum well, an electron blocking layer, a second quantum well, and an upper confinement layer from bottom to top, the electro-absorption modulator further includes a second electrode on the multilayer material structure, and by adjusting the voltage between the first electrode and the second electrode to control the voltage applied to the first quantum well, the injected light is modulated. The semiconductor optical amplifier further includes a third electrode on the multilayer material structure, and by adjusting the voltage between the first electrode and the third electrode to control the current loaded into the second quantum well, the injected light is amplified, and the electron blocking layer is used to block the current loaded into the second quantum well from flowing into the first quantum well. In the electro-absorption modulator, there is a first difference between the extinction ratio corresponding to the transverse electric TE mode and the extinction ratio corresponding to the transverse magnetic TM mode, the first difference depends on the thickness of the upper confinement layer and the voltage applied to the first quantum well, and the first difference is equal to or less than a first preset value. In the semiconductor optical amplifier, there is a second difference between the modal gain corresponding to the TE mode and the modal gain corresponding to the TM mode, the second difference depends on the thickness of the upper confinement layer and the current loaded into the second quantum well, and the second difference is equal to or less than a second preset value. The thickness of the upper confinement layer is set such that, in the first quantum well, the ratio of the difference between the optical confinement factor of the TE mode and the optical confinement factor of the TM mode is about 2.2%, and / or in the second quantum well, the optical confinement factor of the TE mode is equal to the optical confinement factor of the TM mode. An optical modulation amplification device. Claim 2 In the first quantum well, there is a third difference between the optical confinement coefficient of the TE mode and the optical confinement coefficient of the TM mode, and in the first quantum well, there is a fourth difference between the material absorption coefficient of the TE mode and the material absorption coefficient of the TM mode. The first difference depends on the third difference and the fourth difference. The third difference depends on the thickness of the upper separation confinement layer. The fourth difference depends on the voltage applied to the first quantum well. The third difference is equal to or less than a third preset value, and the fourth difference is equal to or less than a fourth preset value. The optical modulation amplification device according to claim 1.

3. In the second quantum well, there is a fifth difference between the optical confinement coefficient of the TE mode and the optical confinement coefficient of the TM mode, and in the second quantum well, there is a sixth difference between the material gain of the TE mode and the material gain of the TM mode. The second difference depends on the fifth difference and the sixth difference. The fifth difference depends on the thickness of the upper separation confinement layer. The sixth difference depends on the current loaded into the second quantum well. The fifth difference is equal to or less than a fifth preset value, and the sixth difference is equal to or less than a sixth preset value. The optical modulation amplification device according to claim 1 or 2.

4. The material refractive index of the first quantum well is greater than the material refractive index of the second quantum well. The optical modulation amplification device according to any one of claims 1 to 3.

5. The multilayer material structures on both sides of the semiconductor optical amplifier using the second waveguide as an axis are symmetric. The optical modulation amplification device according to any one of claims 1 to 4.

6. The multilayer material structures on both sides of the electro-absorption modulator using the first waveguide as an axis are etched. The optical modulation amplification device according to any one of claims 1 to 5.

7. The etched region is filled with polyimide or benzocyclobutene. The optical modulation amplification device according to claim 6.

8. The thickness H of the upper separation confinement layer satisfies 75 nm ≤ H ≤ 95 nm. The optical modulation amplification device according to any one of claims 1 to 7.

9. The length L of the first waveguide satisfies L ≤ 400 μm. The optical modulation amplification device according to any one of claims 1 to 8.

10. The width W of the ridge waveguide structures of both the first waveguide and the second waveguide satisfies 1.5 μm ≤ W ≤ 3 μm. The optical modulation amplification device according to any one of claims 1 to 9.

11. The optical modulation amplification device further includes a controller, a voltage source, and a current source. The controller is configured to control the voltage source to load the voltage output by the voltage source onto the electro-absorption modulator to modulate the injection light. The controller is configured to control the current source to load the current output by the current source onto the semiconductor optical amplifier to amplify the injection light. The optical modulation and amplification device according to any one of claims 1 to 10.

12. The optical modulation and amplification device according to any one of claims 1 to 11, wherein a groove is provided between the second electrode of the electro-absorption modulator and the third electrode of the semiconductor optical amplifier to achieve electrical insulation.

13. The optical modulation and amplification device according to claim 12, wherein protons or inert ions are injected into the groove.

14. The optical modulation and amplification device according to any one of claims 1 to 11, wherein protons or inert ions are injected between the second electrode of the electro-absorption modulator and the third electrode of the semiconductor optical amplifier to achieve electrical insulation.

15. An optical module, comprising the optical modulation and amplification device according to any one of claims 1 to 14 and a driver, wherein the driver is configured to drive the optical modulation and amplification device to modulate and amplify injection light.

16. An optical network unit ONU, comprising the optical module according to claim 15 and a media access control MAC chip, wherein the optical module is configured to convert an electrical signal output by the MAC chip into an optical signal.

17. An optical communication system, comprising an optical line terminal device OLT and the ONU according to claim 16, wherein the OLT is configured to transmit injection light to the ONU.

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