Chirp compensation direct modulation semiconductor laser

Abstract

This invention discloses a chirp-compensated direct-modulation semiconductor laser, which, from bottom to top along its growth direction, comprises a lower cladding region, a chirp compensation region, a spacer region, an active region, and an upper cladding region. The chirp-compensated direct-modulation semiconductor laser also includes an AC current source and an AC voltage source. The AC current source is used to inject a modulation current into the active region, and the AC voltage source is used to apply a modulation voltage to the chirp compensation region. The modulation current and modulation voltage are out of phase. This invention provides a chirp compensation region below the active region. When an out-of-phase voltage is provided externally, the material in the chirp compensation region generates negative chirp, thereby partially or completely canceling the positive chirp of the active region.

Description

Technical Field

[0001] This invention relates to the field of semiconductor lasers, and more specifically to a chirped compensated direct modulation semiconductor laser. Background Technology

[0002] Directly modulated semiconductor lasers can modulate light intensity by changing the injection current. This method is simple, low-cost, and efficient, but it has a major drawback: parasitic frequency chirp. Chirp occurs because changes in current alter not only the carrier concentration in the active region but also the refractive index of the material. That is, while changing the output power to achieve the desired intensity modulation, the change in the refractive index causes phase modulation, resulting in parasitic frequency chirp. This chirp severely limits the transmission distance of signals in standard single-mode optical fibers. When the laser operates away from the fiber's zero-dispersion point, the fiber's dispersion effect causes different frequency components within the modulated waveform to propagate at different speeds within the fiber. After a certain transmission distance, this leads to severe signal distortion and causes the received bit error rate to exceed the limit. Therefore, suppressing chirp is crucial for improving the performance of directly modulated semiconductor lasers and increasing their transmission distance.

[0003] The commonly used existing chirp reduction method is external modulation, where the laser operates in continuous wave mode with a constant output power. The optical signal is then intensity-modulated by a separate external device (such as an electroabsorption modulator or a Mach-Zehnder modulator). This fundamentally decouples power modulation and phase modulation, resulting in extremely low chirp, even producing zero-chirp or negative-chirp signals. However, its disadvantages are also significant: it is typically costly, has high losses, high power consumption, and is complex to manufacture or package. Another highly effective chirp reduction method is to use optical feedback or injection locking. This involves using external optical elements to feed a portion of the output light back to the laser cavity, or using a master laser to lock the slave laser, thereby stabilizing the frequency of the lasing wavelength externally. However, such systems are extremely sensitive to optical path collimation, polarization, and phase, have poor anti-interference capabilities, are complex and difficult to control stably, and are usually impossible to integrate. There are generally two types of solutions for mitigating chirp in the electrical domain: one uses waveform shaping of the driving electrical signal at the transmitter, but this involves complex circuit design and requires precise models and debugging. Furthermore, these methods may work well for some coding patterns but poorly for others. Another type is a post-compensation scheme that performs electronic equalization at the receiver and corrects distortion caused by chirp and dispersion through digital signal processing. This scheme, besides increasing receiver complexity and power consumption, can only correct, not reduce, the chirp at the transmitter. When the chirp is too large and causes severe signal degradation, the equalization will fail. The last type of method is direct optimization of the laser structure and design. This type of method suppresses the chirp effect directly within the laser through the design of specific active regions, gratings, and cavity structures. This method requires no complex circuits or external equipment and is highly suitable for monolithic integration. However, as the modulation rate increases and the operating wavelength moves away from the zero-dispersion region, the difficulty of chirp suppression increases significantly. Summary of the Invention

[0004] The purpose of this invention is to propose a direct modulation semiconductor laser based on a chirp compensation functional region, and to use corresponding current injection and voltage driving schemes to achieve chirp control.

[0005] To achieve the above objectives, the present invention provides a chirped-compensated direct-modulation semiconductor laser, characterized in that the chirped-compensated direct-modulation semiconductor laser comprises, from bottom to top along the growth direction, a lower cladding region, a chirped-compensation region, a spacer region, an active region, and an upper cladding region; the chirped-compensated direct-modulation semiconductor laser further includes an AC current source and an AC voltage source, the AC current source being used to inject a modulation operating current into the active region, and the AC voltage source being used to apply a modulation operating voltage to the chirped-compensation region, wherein the modulation operating current and the modulation operating voltage are out of phase.

[0006] Optionally, the modulation rate of the modulation operating current and the modulation operating voltage are the same.

[0007] Optionally, the active region generates positive chirp, the chirp compensation region generates negative chirp, and the magnitude of the modulation operating voltage is configured such that the negative chirp partially or completely cancels out the positive chirp.

[0008] Optionally, the active region generates positive chirp, the chirp compensation region generates negative chirp, and the thickness of at least one of the spacer layer and the chirp compensation region is configured such that the negative chirp partially or completely cancels out the positive chirp.

[0009] Optionally, the AC current source is connected between the interval region and the upper cladding region, and the AC voltage source is connected between the interval region and the lower cladding region.

[0010] Optionally, the chirped compensated direct modulated semiconductor laser includes a first electrode located at the top of the upper cladding region, a second electrode located on both sides of the ridge waveguide between the active region and the spacer region, and a third electrode located at the bottom of the lower cladding region; the first and second electrodes are connected to the AC current source, and the second and third electrodes are connected to the AC voltage source.

[0011] Optionally, both the lower cladding region and the upper cladding region are N-type doped; the active region and the chirp compensation region are not doped; and the spacer region is P-type doped.

[0012] Optionally, a distributed feedback grating is provided in the interval region along the laser propagation direction.

[0013] The present invention also provides a method for operating a chirp-compensated direct-modulation semiconductor laser, the method comprising adjusting the negative chirp generated in the chirp compensation region by adjusting the magnitude of the modulation operating voltage.

[0014] The present invention also provides a method for fabricating a chirped-compensated direct-modulation semiconductor laser, the method comprising: S1: An N-type buffer layer, an N-type confinement layer, a chirp compensation region, a P-type confinement layer, a P-type spacer layer, and a P-type grating layer are grown sequentially from the substrate layer upwards. S2: Etch the P-type grating layer to form the required feedback grating; S3: Secondary epitaxial buried grating, sequentially growing P-type spacer layer, P-type ohmic contact layer, P-type spacer layer, P-type confinement layer, active layer, N-type confinement layer, N-type spacer layer, N-type upper cladding layer and N-type ohmic contact layer; S4: Etch a strip-shaped ridge waveguide to the interface between the N-type spacer layer and the N-type upper cladding layer; S5: Continue etching the grooves on both sides of the ridge formed in step S4 to the interface between the P-type ohmic contact layer and the P-type spacer layer. S6: Deposit an electrical isolation layer and create electrode openings on the P-type ohmic contact layer at the bottom of the channel and on the N-type ohmic contact layer at the top of the ridge; S7: Deposit a central P-side metal electrode and a top N-side metal electrode on the P-type ohmic contact layer and the N-type ohmic contact layer, respectively; S8: Backside thinning, polishing, and deposition of bottom N-side metal electrode; The chirped compensated direct modulated semiconductor laser further includes an AC current source and an AC voltage source. The AC current source is connected to the top N-side metal electrode and the middle P-side metal electrode and is used to inject a modulation current into the active region. The AC voltage source is connected to the middle P-side metal electrode and the bottom N-side metal electrode and is used to apply a modulation voltage to the chirped compensated region. The modulation current and the modulation voltage are out of phase.

[0015] The beneficial effects of this invention are as follows: (1) This invention proposes a direct modulation semiconductor laser based on the chirp compensation functional region, and uses corresponding current injection and voltage driving schemes to achieve chirp control. The chirp amplitude can be greatly reduced, and the polarity can be effectively controlled from positive chirp to negative chirp.

[0016] (2) The direct modulation semiconductor laser proposed in this invention introduces a chirp compensation layer structure based on epitaxial growth, which is stacked and grown sequentially with the active region. Without the need for complex processes such as docking growth, chirp can be effectively controlled under direct modulation. It has a compact structure, low manufacturing cost, and can be integrated on a single chip. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the functional area arrangement of the chirp-compensated direct-modulation semiconductor laser proposed in this invention; Figure 2 This is an epitaxial structure diagram of Example 1; Figure 3(a) shows the two-dimensional distribution of the mode field of the directly modulated semiconductor laser in Comparative Example 1, and Figure 3(b) shows the distribution of the mode refractive index variation of the 'bit0' signal current and the 'bit1' signal current along the longitudinal cavity length under the 10 Gbit / s modulation working condition. Figure 4 The time-domain chirp diagrams are shown for the outputs of the directly modulated semiconductor lasers in Examples 1 to 3 and Comparative Example 1. Figure 5 This is a schematic diagram of the modulation operating current injected into the active region and the modulation operating voltage applied to the chirp compensation region in Examples 1 to 3. Figure 6(a) shows the two-dimensional distribution of the light field in the cross-sectional xy plane of the direct modulation semiconductor laser containing the chirp compensation functional region proposed in this invention in Example 1. The area marked by the dashed line in the figure is the active region, and the area marked by the dotted line is the chirp compensation region. Figure 6(b) shows the two-dimensional distribution of the light field in the cross-sectional xy plane of the direct modulation semiconductor laser containing the chirp compensation functional region proposed in this invention in Example 2. The area marked by the dashed line in the figure is the active region, and the area marked by the dotted line is the chirp compensation region. Figure 6(c) shows the two-dimensional distribution of the light field in the cross-sectional xy plane of the direct modulation semiconductor laser containing the chirp compensation functional region proposed in this invention in Example 3. The area marked by the dashed line in the figure is the active region, and the area marked by the dotted line is the chirp compensation region. Figure 7 Examples 1 to 3 show the changes in mode refractive index in the chirped compensation region at a working wavelength of 1577 nm when different inverting voltages V23 are applied. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] Traditional direct-modulation semiconductor lasers, while changing the output power to achieve the desired intensity modulation, also generate parasitic frequency chirps due to phase modulation caused by changes in the refractive index of the material. The parasitic chirp generated in the active region is positive. This invention incorporates a chirp compensation region below the active region. When an external anti-phase voltage is applied, the material in the chirp compensation region generates negative chirp, thereby partially or completely canceling the positive chirp of the active region. It should be noted that the complete cancellation of the positive chirp of the active region by the negative chirp generated by the chirp compensation region material in this invention should be understood to include both cases where the overall chirp is zero and cases where the overall chirp is negative. The overall chirp is the net chirp that takes into account the chirp effects of both the active region and the chirp compensation region.

[0020] The functional region arrangement diagram of the chirp-compensated direct-modulation semiconductor laser proposed in this invention is shown below. Figure 1 As shown, the epitaxial structure, from bottom to top along the growth direction x, includes a lower cladding region 101, a chirp compensation region 102, a spacer region 103, an active region 104, and an upper cladding region 105. The active region 104 provides the signal amplification gain necessary for laser lasing. When a modulation current is injected into the active region material, due to the Cramé-Kleinich (KK) relationship of the material, the increase in current causes a decrease in the refractive index of the active region, an increase in the laser oscillation frequency, thus forming a positive chirp characteristic where the oscillation frequency at the pulse rise edge position also increases. In standard single-mode optical fiber, the dispersion coefficient... When the laser operates at wavelength Above the zero-dispersion wavelength, the dispersion coefficient of optical fiber is positive and gradually increases with wavelength, meaning that the transmission speed of signals at shorter wavelengths (higher frequencies) is limited. It is faster than long-wavelength signals. Therefore, as the transmission distance within the optical fiber increases, the rising edge of the signal becomes further and further away from the falling edge, and the signal is severely broadened and distorted.

[0021] In the x-direction, the spacer region 103 located between the chirped compensation region 102 and the active region 104 functions to control the mode field distribution within the laser cross-section (the xy-plane perpendicular to the propagation direction z), thereby controlling the degree of overlap between the mode fields and the active region 104 and the chirped compensation region 102, respectively, as determined by the optical field confinement factor. and Indicates the active region optical field confinement factor. The light field intensity distributed within the active region (104) is the proportion of the total light field intensity distributed across all regions; the light field confinement factor in the chirped compensation region. This refers to the proportion of the light field intensity distributed within the chirped compensation region 102 to the total light field intensity distributed across all regions. The refractive index change in the active region mode is... The refractive index change in the chirped compensation region mode is as follows: ,in The difference in average material refractive index caused by current injection in the active region of the laser. The difference in average material refractive index caused by the inverting voltage in the laser chirp compensation region.

[0022] Due to the reverse bias of its driving voltage, the chirp compensation region 102 absorbs the signal. Also, due to the KK transform relationship of the material, the absorption increases the refractive index of the chirp compensation region, reduces the laser oscillation frequency, and forms a negative chirp, thus partially or completely canceling the positive chirp in the active region. The overall frequency chirp change is considered. It can be represented as ,in For the grating period, The speed at which light travels in free space. This is the operating wavelength. As you can see, and The signs are opposite, meaning the directions of change are reversed. This is achieved through the design of the chirp compensation region. As close as possible to the active region Therefore, the frequency change It was greatly reduced. When The absolute value of the compensation is greater than When the absolute value of is reached, the material exhibits reverse chirping relative to the active region, i.e., negative chirping.

[0023] In one embodiment, a distributed feedback grating is disposed in the spacer region 103 along the z direction to provide the optical feedback effect necessary for the semiconductor laser to form optical oscillation in the z direction. The grating can be any one of a uniform grating, a phase-shifted grating, or a partial grating with a mode selection mechanism, and can be fabricated by any one or more of holographic lithography, EBL lithography, nanoimprinting, deep ultraviolet lithography and other grating formation processes.

[0024] In one embodiment, both the lower cladding region 101 and the upper cladding region 105 are N-type doped; the active region 104 and the chirp compensation region 102 are not doped and maintain the intrinsic concentration; the spacer region 103 is P-type doped.

[0025] The chirp compensation direct modulation semiconductor laser provided by the present invention further includes electrodes. The first electrode 108 is disposed on the top of the top cladding region 105; the second electrode 107 is disposed on both sides of the ridge waveguide between the active region 104 and the spacer region 103; the third electrode 106 is disposed on the bottom of the bottom cladding region 101. An AC current source 109 is applied between the first electrode 108 and the second electrode 107. The negative charges, that is, electrons, injected by the first electrode 108 are assisted by the N-type impurities provided by the N-type doped top cladding region 105 thereunder to inject electrons into the active region 104. The positive charges, that is, holes, injected by the second electrode 107 are assisted by the P-type impurities provided by the P-type doped spacer region 103 thereunder to equivalently inject holes into the active region 104 as well. Form as Figure 1 The modulation working current (I21) path indicated by the arrow flowing from the second electrode 107 to the first electrode 108 is formed, so that electrons and holes recombine in the active region to generate photons. An inverted AC voltage source 110 is applied between the second electrode 107 and the third electrode 1, and the voltage (V2) at the second electrode 107 is less than the voltage (V3) at the third electrode 106, that is, V2<V3, and the inverted voltage V23 of the inverted AC voltage source 110 is V2 - V3.

[0026] During direct modulation operation, the AC current I flowing from the second electrode 107 to the first electrode 108 21 is inverted with the AC voltage V between the second electrode 107 and the third electrode 108 23 That is, I 21 When the current increases, V 23 increases inversely.

[0027] There is no particular limitation on the growth material system used in the chirp compensation direct modulation semiconductor laser provided by the present invention, and it can be but not limited to InP-AlGaInAs-InGaAsP material system, GaAs-InGaAs-AlGaAs material system, GaAs-(In)GaAsP-(Al)GaInP material system, sapphire-InGaN-AlGaN material system, etc.

[0028] Example 1

[0029] C / L band lasers suffer from relatively severe parasitic chirp problems due to their wavelengths being much larger than the zero-dispersion wavelength of standard single-mode fiber. The protocol requirements for 10G Passive Optical Network (PON) systems necessitate a downlink wavelength of 1577nm for the OLT (office level unit). The significant fiber dispersion cost caused by the chirp problem of directly modulated semiconductor lasers has been a long-standing issue that the industry needs to address. Therefore, the 10G 1577nm directly modulated semiconductor laser is a typical embodiment of this invention. Specifically, the device in this embodiment operates at a wavelength of 1577nm, and the material system is InP-AlGaInAs-InGaAsP. The substrate material is InP, and the active region, spacer region, and chirp compensation region are made of AlGaInAs. The thicknesses of the active region, spacer region, and chirp compensation region are 135nm, 450nm, and 116nm, respectively. The optical field confinement factors of the active region and the chirp compensation region are 0.073 and 0.024, respectively. The P-type grating uses InGaAsP material and is a refractive index-coupled uniform grating.

[0030] The epitaxial structure of the chirp-compensated direct-modulation semiconductor laser in this embodiment is as follows: Figure 2 As shown, the device, along the growth direction x, sequentially includes an N-type substrate 201, an N-type buffer layer 202, an N-type confinement layer 203, a chirp compensation region 204, a P-type confinement layer 205, a P-type spacer layer 206, a P-type grating layer 207, a P-type spacer layer 208, a P-type ohmic contact layer 209, a P-type spacer layer 210, a P-type confinement layer 211, an active layer 212, an N-type confinement layer 213, an N-type spacer layer 214, an N-type upper cladding layer 215, and an N-type ohmic contact layer 216. The three working electrodes of the device, from bottom to top, are a bottom N-side metal electrode 217, a middle P-side metal electrode 218, and a top N-side metal electrode 219.

[0031] The fabrication method of the chirp-compensated directly modulated semiconductor laser in this embodiment is as follows: S1: An N-type buffer layer 202, an N-type confinement layer 203, a chirp compensation region 204, a P-type confinement layer 205, a P-type spacer layer 206, and a P-type grating layer 207 are grown sequentially from the substrate 201 layer upwards. S2: Etch the P-type grating layer 207 to form the required feedback grating; S3: Secondary epitaxial buried grating, with P-type spacer layer 208, P-type ohmic contact layer 209, P-type spacer layer 210, P-type confinement layer 211, active layer 212, N-type confinement layer 213, N-type spacer layer 214, N-type upper cladding layer 215 and N-type ohmic contact layer 216 grown sequentially. S4: Etch the strip-shaped ridge waveguide to the interface between the N-type spacer layer 214 and the N-type upper cladding layer 215; S5: Continue etching the channels on both sides of the ridge formed in step S4 to the interface between the P-type ohmic contact layer 209 and the P-type spacer layer 210. S6: Deposit an electrical isolation layer and make electrode openings on the bottom P-type ohmic contact layer 209 of the channel and the top N-type ohmic contact layer 216 of the ridge. S7: Deposit a central P-side metal electrode 218 and a top N-side metal electrode 219 on the P-type ohmic contact layer 209 and the N-type ohmic contact layer 216, respectively; S8: Backside thinning, polishing, and deposition of bottom N-side metal electrode 217.

[0032] The prepared chirped compensated direct modulated semiconductor laser also includes an AC current source and an AC voltage source. The AC current source is connected to the top N-side metal electrode and the middle P-side metal electrode to inject a modulation current into the active region. The AC voltage source is connected to the middle P-side metal electrode and the bottom N-side metal electrode to apply a modulation voltage to the chirped compensated region. The modulation current and the modulation voltage are out of phase.

[0033] Comparative Example 1: The directly modulated semiconductor laser in this comparative example does not include the chirp compensation functional region proposed in this invention. Its material system is the same as that in Example 1, with an active layer thickness of 135 nm and an optical field confinement factor of 0.08. Figure 3(a) shows the two-dimensional distribution of the mode field of the directly modulated semiconductor laser in this comparative example, where the dashed line marks the boundary of the active region; Figure 3(b) shows the distribution of the mode refractive index changes of the 'bit0' signal current and 'bit1' signal current along the longitudinal 200 μm cavity length (z direction) under 10 Gbit / s modulation conditions. In Figure 3(b), the 'bit0' signal current is 35 mA and the 'bit1' signal current is 75 mA. It can be seen that the current modulation causes a change in the mode refractive index distribution, and its average mode refractive index change changes from -0.12% (thin dashed line) for the 'bit0' signal to -0.13% (thick dashed line) for the 'bit1' signal. That is... Approximately -0.01%, of which The optical field confinement factor for the active region. The difference in average material refractive index caused by injecting 'bit0' and 'bit1' signal currents into the active region of the laser is shown. It can be seen that as the current increases, the refractive index of the active region mode decreases, the laser oscillation frequency increases, and positive chirp is generated. The time-domain modulation parasitic chirp of the directly modulated semiconductor laser output in Comparative Example 1 is as follows: Figure 4 As shown by the solid line.

[0034] In Embodiment 1, while the device operates with the forward modulation current I21, an inverting voltage V23 with the same modulation rate of 10 Gbit / s is applied between electrodes 218 and 217. A schematic diagram of the operation of the modulation current I21 and the inverting voltage V23 is shown below. Figure 5 As shown, the injection of the modulation current I21 is the same as in Comparative Example 1, and the inverting voltage V23 is inversely phase to the modulation current I21, modulating between 0V and -1V. The simulation results of the two-dimensional optical field distribution of the laser in the xy plane of the cross section in Example 1 are shown in Figure 6(a).

[0035] Figure 7 To optimize the mode refractive index of the chirped compensation functional region at the operating wavelength of 1577 nm. As the inverting voltage V23 changes, where The difference in material refractive index is caused by the 'bit0' and 'bit1' signal voltages of the inverting voltage V23 in the laser chirp compensation region. It can be seen that the change in mode refractive index caused by the inverting voltage V23 from 0V to -1V is approximately 0.006%. Compared to the -0.01% change in the active region mode refractive index during modulation in Comparative Example 1, it can be expected that the chirp will be significantly reduced, as shown in the chirp time-domain data obtained from numerical simulation. Figure 4 As shown by the dashed line. In this embodiment, when the inverting voltage V23 is -1V, the combined chirp of the active region and the chirp compensation region is significantly reduced compared to Comparative Example 1.

[0036] Example 2 The difference between this embodiment and Embodiment 1 is that the thickness of the spacer region is 250 nm, and the optical field confinement factors of the active region and the chirped compensation region are 0.077 and 0.038, respectively. The other structures are the same as in Embodiment 1, and the operating conditions are the same as in Embodiment 1.

[0037] In this embodiment, the simulation results of the two-dimensional light field distribution of the device within the cross-sectional xy plane are shown in Figure 6(b). From Figure 7 As can be seen, the change in mode refractive index caused by the inverting voltage V23 from 0V to -1V is approximately 0.009%. Compared to the change in active mode refractive index during modulation of -0.01% in Comparative Example 1, it can be expected that the chirp will be significantly reduced. The chirp time-domain plot obtained from numerical simulation is shown below. Figure 4As shown by the midpoint line, the overall chirp is near the critical point between positive and negative chirp. Furthermore, from... Figure 7 It can be seen that when the inverting voltage V23 is approximately -1.1V, the resulting change in the mode refractive index is about 0.01%, and the overall chirp will be almost zero. However, as the voltage V23 continues to increase, the resulting change in the mode refractive index will be greater than 0.01%, resulting in a negative chirp. Therefore, by adjusting the magnitude of the inverting voltage, the negative chirp generated in the chirp compensation region can partially or completely cancel the positive chirp in the active region.

[0038] Example 3 The difference between this embodiment and embodiment 2 is that the thickness of the chirp compensation region is increased from 116nm to 171nm. In this case, the optical field confinement factors of the active region and the chirp compensation region are 0.065 and 0.062, respectively. The other structures are the same as those in embodiment 2, and the operating conditions are the same as those in embodiment 2.

[0039] In this embodiment, the simulation results of the two-dimensional light field distribution of the device within the xy-plane of the cross-section are shown in Figure 6(c). The chirp time-domain plot obtained from the numerical simulation is shown below. Figure 4 As shown by the dashed line in the middle. Compared to Example 2, it can be seen that increasing the thickness of the chirp compensation region can further increase the negative chirp size of the chirp compensation region, so that the overall chirp exhibits negative chirp characteristics.

[0040] Figure 7 Examples 1 to 3 illustrate the changes in mode refractive index at the operating wavelength of 1577 nm in the chirp compensation region when different inversion voltages V23 are applied. It can be seen that the higher the inversion voltage, the greater the change in mode refractive index, and the more chirp can be compensated. The degree of compensation varies in different examples due to differences in factors such as the thickness of the spacer layer, the thickness of the chirp compensation region, and the magnitude of the inversion voltage V23. Therefore, in the chirp-compensated direct-modulation semiconductor laser proposed in this invention, the negative chirp generated by the chirp compensation region material can be adjusted by regulating the magnitude of the inversion voltage, or by configuring the thickness of at least one of the spacer layer and the chirp compensation region, thereby partially or completely canceling the positive chirp of the active region.

[0041] The present invention has been described above with reference to specific embodiments. These descriptions are merely illustrative and should not be construed as limiting the scope of protection of the present invention in any way. Based on the explanation herein, those skilled in the art can readily conceive of other specific embodiments of the present invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A chirp-compensated directly modulated semiconductor laser, characterized in that The chirped compensated direct modulated semiconductor laser comprises, from bottom to top along the growth direction, a lower cladding region, a chirped compensation region, a spacer region, an active region, and an upper cladding region. The chirped compensated direct modulated semiconductor laser further includes an AC current source and an AC voltage source. The AC current source is used to inject a modulation operating current into the active region, and the AC voltage source is used to apply a modulation operating voltage to the chirped compensated region. The modulation operating current and the modulation operating voltage are out of phase.

2. The chirp-compensated directly modulated semiconductor laser of claim 1, wherein, The modulation rates of the modulation operating current and the modulation operating voltage are the same.

3. The chirp-compensated directly modulated semiconductor laser of claim 1, wherein, The active region generates positive chirp, the chirp compensation region generates negative chirp, and the magnitude of the modulation operating voltage is configured such that the negative chirp partially or completely cancels out the positive chirp.

4. The chirp-compensated directly modulated semiconductor laser of claim 1, wherein, The active region generates positive chirp, the chirp compensation region generates negative chirp, and the thickness of at least one of the spacer layer and the chirp compensation region is configured such that the negative chirp partially or completely cancels out the positive chirp.

5. The chirp-compensated directly modulated semiconductor laser of claim 1, wherein, The AC current source is connected between the interval region and the upper cladding region, and the AC voltage source is connected between the interval region and the lower cladding region.

6. The chirp-compensated directly modulated semiconductor laser of claim 5, wherein, The chirped compensated direct modulated semiconductor laser includes a first electrode located at the top of the upper cladding region, a second electrode located on both sides of the ridge waveguide between the active region and the spacer region, and a third electrode located at the bottom of the lower cladding region; the first and second electrodes are connected to the AC current source, and the second and third electrodes are connected to the AC voltage source.

7. The chirp-compensated directly modulated semiconductor laser of claim 1, wherein, Both the lower and upper cladding regions are N-type doped; the active region and the chirp compensation region are not doped; and the spacer region is P-type doped.

8. The chirp-compensated directly modulated semiconductor laser of claim 1, wherein, A distributed feedback grating is provided in the interval region along the laser propagation direction.

9. A method of operating a chirp-compensated directly modulated semiconductor laser as claimed in any one of claims 1 to 8, characterized in that, The working method includes adjusting the negative chirp generated by the chirp compensation region by adjusting the magnitude of the modulation operating voltage.

10. A method of manufacturing a chirp-compensated directly modulated semiconductor laser, characterized in that The preparation method includes: S1: An N-type buffer layer, an N-type confinement layer, a chirp compensation region, a P-type confinement layer, a P-type spacer layer, and a P-type grating layer are grown sequentially from the substrate layer upwards. S2: Etch the P-type grating layer to form the required feedback grating; S3: Secondary epitaxial buried grating, sequentially growing P-type spacer layer, P-type ohmic contact layer, P-type spacer layer, P-type confinement layer, active layer, N-type confinement layer, N-type spacer layer, N-type upper cladding layer and N-type ohmic contact layer; S4: Etch a strip-shaped ridge waveguide to the interface between the N-type spacer layer and the N-type upper cladding layer; S5: Continue etching the grooves on both sides of the ridge formed in step S4 to the interface between the P-type ohmic contact layer and the P-type spacer layer. S6: Deposit an electrical isolation layer and create electrode openings on the P-type ohmic contact layer at the bottom of the channel and on the N-type ohmic contact layer at the top of the ridge; S7: Deposit a central P-side metal electrode and a top N-side metal electrode on the P-type ohmic contact layer and the N-type ohmic contact layer, respectively; S8: Backside thinning, polishing, and deposition of bottom N-side metal electrode; The chirped compensated direct modulated semiconductor laser further includes an AC current source and an AC voltage source. The AC current source is connected to the top N-side metal electrode and the middle P-side metal electrode and is used to inject a modulation current into the active region. The AC voltage source is connected to the middle P-side metal electrode and the bottom N-side metal electrode and is used to apply a modulation voltage to the chirped compensated region. The modulation current and the modulation voltage are out of phase.

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