Electroabsorption modulated laser and method of manufacturing the same

Abstract

This disclosure provides an electroabsorption modulated laser and its fabrication method, relating to the field of semiconductor optoelectronic integrated devices. The electroabsorption modulated laser of this disclosure includes a substrate; an active layer formed on the surface of the substrate, the active layer being divided into adjacent first active segments and second active segments along a first direction; a grating disposed on the surface of the first active segment; a capping layer formed on the surface of the active layer; and a contact layer formed on the surface of the capping layer, the contact layer being divided by multiple electrically isolated trenches into sequentially adjacent first contact segments, second contact segments, third contact segments, and fourth contact segments along the first direction. The first active segment, grating, capping layer, and first contact segment constitute a first laser; the first active segment, grating, capping layer, and second contact segment constitute a second laser; the first active segment, grating, capping layer, and third contact segment constitute a third laser; and the second active segment, capping layer, and fourth contact segment constitute a modulator.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor optoelectronic integrated devices, and in particular to an electroabsorption modulated laser and its fabrication method. Background Technology

[0002] With the rapid development of data transmission networks, basic fiber optic networks have gradually shown insufficient carrying capacity, thus placing higher performance demands on optical transmitter chips. To meet this requirement, optical transmitter chips typically employ electro-absorption modulated laser schemes, integrating optical signal generation and modulation to reduce signal loss during the generation and modulation process. This results in higher output optical power and narrower spectral linewidth, significantly improving the transmission quality and stability of optical signals. However, existing electro-absorption modulated lasers only achieve simple integration of the modulator and laser, failing to simultaneously achieve high-bandwidth transmission and continuously tunable wavelength, hindering further performance improvements in optical transmitter chips. Summary of the Invention

[0003] In view of this, the present disclosure provides an electroabsorption modulated laser and a method for fabricating the same.

[0004] One aspect of this disclosure provides an electroabsorption modulated laser, comprising: a substrate; an active layer formed on the surface of the substrate, the active layer being divided into adjacent first active segments and second active segments along a first direction; a grating disposed on the surface of the first active segment; a capping layer formed on the surface of the active layer; and a contact layer formed on the surface of the capping layer, the contact layer being separated by a plurality of electrically isolated trenches into sequentially adjacent first contact segments, second contact segments, third contact segments, and fourth contact segments along the first direction; wherein, the first active segment, the grating, the capping layer, and the first contact segment constitute a first laser for generating an optical signal by electrical injection; the first active segment, the grating, the capping layer, and the second contact segment constitute a second laser for adjusting the wavelength of the optical signal by thermal tuning of the phase induced by electrical injection; the first active segment, the grating, the capping layer, and the third contact segment constitute a third laser for cooperating with the first laser to generate an optical signal by electrical injection; and the second active segment, the capping layer, and the fourth contact segment constitute a modulator for achieving high-bandwidth transmission of the optical signal.

[0005] According to embodiments of this disclosure, the injection current of the first laser is different from that of the second laser, and the injection current of the first laser is the same as that of the third laser.

[0006] According to embodiments of the present disclosure, the electroabsorption modulated laser further includes a P-type electrode, which is formed in multiple segments on the surface of each segment of the contact layer; and an N-type electrode, which is formed on the side of the substrate away from the active layer.

[0007] According to an embodiment of this disclosure, the P-type electrode on the surface of the first contact section is electrically connected to the P-type electrode on the surface of the third contact section.

[0008] According to embodiments of this disclosure, the first contact segment, the second contact segment, and the third contact segment together constitute the laser segment of the contact layer; wherein, the length of the first contact segment along the first direction in the laser segment accounts for 50% to 60%, the length of the second contact segment along the first direction in the laser segment accounts for 10% to 20%, and the length of the third contact segment along the first direction in the laser segment accounts for 20% to 30%.

[0009] According to embodiments of this disclosure, the active layer includes a lower waveguide layer, a multiple quantum well layer, and an upper waveguide layer. The lower waveguide layer is formed on the substrate surface, and the lower waveguide layer, the multiple quantum well layer, and the upper waveguide layer are stacked sequentially in a direction away from the substrate.

[0010] According to embodiments of this disclosure, the photofluorescence spectrum wavelength of the first active segment is 1280nm~1300nm, and the photofluorescence spectrum wavelength of the second active segment is 1230nm~1260nm.

[0011] Another aspect of this disclosure provides a method for fabricating an electroabsorption modulated laser, comprising providing a substrate, fabricating an active layer on the substrate surface, dividing the active layer into a first initial segment and a second initial segment along a first direction; fabricating a silicon dioxide mask on the surface of the first initial segment, etching away the area of ​​the active layer not covered by the silicon dioxide mask to obtain the first active segment; fabricating a second active segment on one side of the first active segment, the first active segment and the second active segment together forming a new active layer; removing the silicon dioxide mask, and in the first active segment... A grating is fabricated on the surface of the segment; a capping layer and a contact layer are fabricated layer by layer on the surface of the new active layer; multiple electrically isolated trenches are etched on the contact layer to form a first contact segment, a second contact segment, a third contact segment, and a fourth contact segment that are sequentially adjacent along a first direction; a multi-segment P-type electrode is fabricated on the etched contact layer surface, and the P-type electrode located on the surface of the first contact segment is electrically connected to the P-type electrode located on the surface of the third contact segment; an N-type electrode is fabricated on the side of the substrate away from the new active layer, thus completing the fabrication of the electroabsorption modulated laser.

[0012] According to embodiments of this disclosure, the method for fabricating an electroabsorption modulated laser further includes fabricating a capping layer and a contact layer layer by layer on the surface of a new active layer, and then etching the capping layer and the contact layer to form a ridge waveguide structure.

[0013] According to embodiments of this disclosure, the method for fabricating an electro-absorption modulated laser further includes etching multiple electrically isolated trenches on a contact layer and then injecting helium ions into each electrically isolated trench.

[0014] The electroabsorption modulated laser and its fabrication method according to the embodiments of this disclosure have at least the following beneficial effects:

[0015] (1) Design a three-segment structure laser capable of wavelength tuning of optical signals, and integrate the three-segment structure laser with a modulator to obtain an electroabsorption modulated laser, so that the electroabsorption modulated laser can achieve both high bandwidth transmission of optical signals and continuous tunability of optical signal wavelength.

[0016] (2) The three-segment laser is divided into a first laser, a second laser and a third laser. The first laser and the third laser are controlled by the same injection current to ensure the uniformity of optical signal generation. The second laser is controlled by a different injection current than the first laser to ensure that the wavelength tuning function and the optical signal generation function of the three-segment laser are independent of each other and to prevent the optical signal wavelength from drifting with the fluctuation of its generation power.

[0017] (3) The wavelength tuning mechanism of the entire electroabsorption modulated laser is simple. It can achieve continuous wavelength tuning without complex material integration. It has low manufacturing cost and is an ideal light source to meet the needs of high bandwidth multi-wavelength tuned data transmission. Attached Figure Description

[0018] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1 A schematic diagram of an electroabsorption modulated laser according to an embodiment of the present disclosure is shown.

[0020] Figure 2 This schematically illustrates the segmentation of the active layer and contact layer of an electroabsorption modulated laser according to an embodiment of the present disclosure;

[0021] Figure 3 A flowchart illustrating a method for fabricating an electroabsorption modulated laser according to an embodiment of the present disclosure is shown schematically.

[0022] Figures 4-12 A schematic diagram illustrating the fabrication process of an electroabsorption modulated laser according to an embodiment of the present disclosure is shown, wherein:

[0023] Figure 4 This is a schematic diagram of the fabrication of an active layer on a substrate surface;

[0024] Figure 5 This is a schematic diagram of the preparation of a silicon dioxide mask on the surface of the first initial section;

[0025] Figure 6 This is a schematic diagram of obtaining the first active section by etching the active layer;

[0026] Figure 7 This is a schematic diagram of preparing a second active segment on one side of the first active segment to form a new active layer;

[0027] Figure 8 This is a schematic diagram of removing the silicon dioxide mask and fabricating a grating on the surface of the first active section;

[0028] Figure 9 This is a schematic diagram of the preparation of the capping layer and the contact layer;

[0029] Figure 10 This is a schematic diagram of etching an electrical isolation trench on the contact layer;

[0030] Figure 11 This is a schematic diagram of the fabrication of a P-type electrode;

[0031] Figure 12 This is a schematic diagram of the fabrication of an N-type electrode. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0035] When using expressions such as "at least one of A, B, and C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C. Similarly, when using expressions such as "at least one of A, B, or C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C.

[0036] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure.

[0037] Figure 1 A schematic diagram of the structure of an electroabsorption modulated laser according to an embodiment of the present disclosure is shown.

[0038] Figure 2 The diagram illustrates a segmentation of the active layer and contact layer of an electroabsorption modulated laser according to an embodiment of the present disclosure.

[0039] like Figure 1 and Figure 2 As shown, in the embodiments of this disclosure, the electroabsorption modulated laser includes a substrate 11, an active layer 12, a grating 13, a capping layer 14, and a contact layer 15.

[0040] Specifically, an active layer 12 is formed on the surface of a substrate 11, and the active layer 12 is divided into adjacent first active segments 12a and second active segments 12b along a first direction. A grating 13 is disposed on the side of the first active segment 12a away from the substrate 11. A capping layer 14 is formed on the side of the active layer 12 away from the substrate 11. A contact layer 15 is formed on the side of the capping layer 14 away from the active layer 12, and the contact layer 15 is divided by a plurality of electrically isolated trenches 16 into sequentially adjacent first contact segments 15a, second contact segments 15b, third contact segments 15c, and fourth contact segments 15d along the first direction.

[0041] The first active section 12a, grating 13, capping layer 14, and first contact section 15a constitute a first laser 1a, used to generate an optical signal through electrical injection. The first active section 12a, grating 13, capping layer 14, and second contact section 15b constitute a second laser 1b, used to adjust the wavelength of the optical signal through thermal tuning of the phase induced by electrical injection. The first active section 12a, grating 13, capping layer 14, and third contact section 15c constitute a third laser 1c, used to generate an optical signal together with the first laser 1a through electrical injection. The second active section 12b, capping layer 14, and fourth contact section 15d constitute a modulator 2, used to achieve high-bandwidth transmission of the optical signal. This means that the three-segment combined laser 1 (comprising the first laser 1a, second laser 1b, and third laser 1c) and the modulator 2 are integrated into a single electrically absorbed modulated laser.

[0042] In addition, an electrical isolation trench 16 is provided between any two adjacent sections of the first contact section 15a, the second contact section 15b, the third contact section 15c, and the fourth contact section 15d, thereby ensuring electrical isolation between any two adjacent devices of the first laser 1a, the second laser 1b, the third laser 1c, and the modulator 2, and preventing electrical crosstalk.

[0043] It should be noted that the electrical isolation trench 16 only isolates the contact layer 15 and does not affect the active layer 12. The entire active layer 12 is physically continuous.

[0044] Furthermore, for the combined laser 1, on the one hand, the active layers 12 of the first laser 1a, the second laser 1b, and the third laser 1c are physically continuous, which allows the light field to propagate seamlessly in the first active section 12a, avoiding end-face reflection loss and optical coupling efficiency problems. On the other hand, the contact layers 15 of the three lasers are separated, which allows the three lasers to be injected with current independently, enabling each laser to perform different functions.

[0045] Specifically, current is injected into the first laser 1a and the third laser 1c. Electrons are injected into the conduction band of the first active segment 12a, and holes are injected into the valence band of the first active segment 12a. Electron-hole recombination generates stimulated emission, thereby providing optical gain and generating an optical signal. This optical signal illuminates the grating 13. The optical signal satisfying the Bragg condition achieves high reflectivity on the grating 13 and oscillates, thus obtaining an optical signal of a specific wavelength.

[0046] When current is injected into the second laser, a large number of charge carriers (electrons) are injected into the active layer. These additional free charge carriers change the dielectric constant of the material, causing a decrease in the effective refractive index of the portion of the first active segment 12a corresponding to the second laser 1b. Although the portion of the first active segment 12a corresponding to the second laser 1b is only a part of the first active segment 12a, since the grating 13 is continuously fabricated on the first active segment 12a, the change in the refractive index of the portion of the first active segment 12a directly changes the equivalent periodicity condition of the entire grating 13. This causes the feedback peak of the entire combined laser 1 to drift, forcing the combined laser 1 to generate lasing at a new Bragg wavelength. Thus, wavelength tuning of the optical signal is achieved by injecting current into the second laser 1b.

[0047] Therefore, when the first laser 1a, the second laser 1b, and the third laser 1c work together, the first laser 1a and the third laser 1c are responsible for generating laser light, while the second laser 1b is responsible for wavelength tuning of the optical signal, so that the entire combined laser 1 can generate a wavelength-tunable optical signal.

[0048] For modulator 2, its fourth contact segment 15d is separated from the third contact segment 15c of the third laser by an electrical isolation trench 16. Therefore, modulator 2 can be independently reverse biased. Utilizing the quantum confinement Stark effect of the second active segment 12b, the absorption edge of the material is red-shifted, thereby generating controllable absorption of the optical signal from the combined laser 1 and achieving modulation of the optical signal. Since the second active segment 12b of modulator 2 and the first active segment 12a of combined laser 1 are physically continuous, this integration method eliminates end-face coupling loss and encapsulation parasitic capacitance, enabling the entire electro-absorption modulated laser to maintain high-speed operation, thus achieving high-bandwidth transmission of the laser signal.

[0049] According to embodiments of this disclosure, the first laser 1a, the second laser 1b, and the first laser 1a constitute a three-segment combined laser 1 capable of optical signal wavelength tuning. The combined laser 1 and the modulator 2 are integrated into the same electro-absorption modulated laser, so that the electro-absorption modulated laser can achieve both high-bandwidth transmission of optical signals and continuous tuning of optical signal wavelength.

[0050] In the embodiments disclosed herein, the injection current of the first laser 1a is different from the injection current of the second laser 1b, and the injection current of the first laser 1a is the same as the injection current of the third laser 1c.

[0051] Specifically, the first laser 1a and the third laser 1c need to generate the same optical signal, therefore their injection currents must be identical. Furthermore, for the first laser 1a and the third laser 1c to generate the optical signal, the injection current density needs to reach the threshold condition for lasing and ensure the output power of the optical signal. Therefore, the injection currents of the first laser 1a and the third laser 1c are typically relatively large, for example, 80mA or 100mA.

[0052] The second laser 1b modulates the Bragg wavelength of the grating 13 by altering the effective refractive index of the first active section 12a through electrical injection. However, the Bragg wavelength of the grating 13 is highly sensitive to changes in the effective refractive index. Even a small change in the effective refractive index caused by a small current injection into the first active section 12a is sufficient for wavelength tuning; a large current, on the other hand, is more likely to produce side effects. Therefore, the injection current of the second laser 1b differs from that of the first laser 1a and is typically controlled at a smaller value, such as 10mA or 15mA.

[0053] In embodiments of this disclosure, the electroabsorption modulated laser further includes a P-type electrode 17, which is formed in multiple segments on the surface of each segment of the contact layer 15; and an N-type electrode 18, which is formed on the side of the substrate 11 away from the active layer 12.

[0054] Specifically, the P-type electrode 17 is divided into multiple P-type electrode segments, and a P-type electrode segment is provided on the surface of the first contact segment 15a, the second contact segment 15b, the third contact segment 15c and the fourth contact segment 15d respectively; while the N-type electrode 18 is formed as a continuous whole on the substrate.

[0055] Furthermore, the P-type electrode sections located in the first contact section 15a, the second contact section 15b, and the third contact section 15c, along with the N-type electrode 18, together constitute the electrode structure of the combined laser 1. Current can be injected into the combined laser 1 by electrically connecting an external power supply to this electrode structure. The P-type electrode section in the fourth contact section 15d, together with the N-type electrode 18, constitutes the electrode structure of the modulator 2. A reverse bias voltage can be applied to the modulator 2 by electrically connecting an external power supply to this electrode structure.

[0056] In embodiments of this disclosure, the P-type electrode 17 on the surface of the first contact section 15a is electrically connected to the P-type electrode 17 on the surface of the third contact section 15c.

[0057] Specifically, the aforementioned electrical connection method allows the first laser 1a and the third laser 1c to be powered by the same external power supply, ensuring that the current injected into them is the same. Only in this way can the optical signals generated by the first laser 1a and the third laser 1c be seamlessly fused in the same continuous cavity to form a stable and pure single-mode optical signal output.

[0058] In the embodiments of this disclosure, the first contact segment 15a, the second contact segment 15b, and the third contact segment 15c together constitute the laser segment of the contact layer 15; wherein, the first contact segment 15a accounts for 50% to 60% of the length of the laser segment along the first direction, the second contact segment 15b accounts for 10% to 20% of the length of the laser segment along the first direction, and the third contact segment 15c accounts for 20% to 30% of the length of the laser segment along the first direction.

[0059] Specifically, among the three segments comprising the laser section of contact layer 15, the first contact segment 15a is the longest, and its length is significantly greater than that of the third contact segment 15c. This means that the optical gain of the combined laser 1 is mainly achieved through the first laser 1a. Although the third laser 1c also provides some optical gain, it is adjacent to the modulator 2, and its main function is to efficiently couple the optical signal into the modulator 2. Therefore, the longer first contact segment 15a ensures that the first laser 1a provides sufficient optical gain; the shorter third contact segment 15c reduces the reflectivity of the optical signal within the cavity, allowing the optical signal to pass quickly through the third laser 1c and enter the modulator 2, thereby increasing the output optical power.

[0060] The length ratio of the second contact segment 15b in the laser segment affects the tuning range, tuning power consumption, and output optical power of the combined laser 1.

[0061] In one embodiment, the lengths of the first contact segment 15a, the second contact segment 15b, and the third contact segment 15c along the first direction in the laser segment account for 54%, 18%, and 28%, respectively. In this case, the length of the second contact segment 15b is a relatively large value within the selectable range, resulting in a larger phase region length for the second laser 1b. With the same injected current, a larger phase region length allows the second laser 1b to cause a larger effective refractive index change in the first active segment 12a, thereby resulting in a larger change in the Bragg wavelength of the grating 13. This gives the combined laser 1 a larger wavelength tuning range.

[0062] Meanwhile, a larger phase region length can enhance the optical leverage effect of the second laser 1b, and a considerable wavelength shift can be achieved with only a small injection current, thereby reducing the power consumption required for tuning.

[0063] However, since the second laser 1b is only used for wavelength tuning of the optical signal and does not provide optical gain, the output optical power of the combined laser 1 will decrease.

[0064] Therefore, this scheme, where the length ratio of the second contact segment 15b is larger within the available range, is suitable for fiber optic network systems with strict requirements on tuning range and where a slight reduction in output power is permissible.

[0065] In another embodiment, the lengths of the first contact segment 15a, the second contact segment 15b, and the third contact segment 15c along the first direction in the laser segment are 58%, 12%, and 30%, respectively. In this case, the length percentage of the second contact segment 15b is relatively small within the selectable range, resulting in a smaller phase region length for the second laser 1b. With the same injected current, the smaller phase region length limits the effective refractive index change in the first active segment 12a caused by the second laser 1b, thus limiting the change in the Bragg wavelength of the grating 13. This results in a smaller wavelength tuning range for the combined laser 1.

[0066] However, because the phase region length of the second laser 1b is smaller, the portion of the combined laser 1 that does not provide optical gain is reduced, which increases the overall optical output power of the combined laser 1.

[0067] Therefore, this scheme, which takes a smaller value within the available range for the length of the second contact segment 15b, is suitable for fiber optic network systems that require extremely high output power and do not need a wide tuning range.

[0068] In another embodiment, the length proportions of the first contact segment 15a, the second contact segment 15b, and the third contact segment 15c along the first direction in the laser segment are 57%, 15%, and 28%, respectively. In this case, the length proportion of the second contact segment 15b is a suitable value within the selectable range, resulting in a moderate phase region length for the second laser 1b. Under these conditions, the tuning range, tuning power consumption, and output optical power of the combined laser 1 are all relatively moderate.

[0069] This approach, which uses a moderate length ratio for the second contact segment 15b within a selectable range, is suitable for most fiber optic network systems without special requirements.

[0070] In the embodiments of this disclosure, the active layer 12 includes a lower waveguide layer 121, a multi-quantum well layer 122, and an upper waveguide layer 123. The lower waveguide layer 121 is formed on the surface of the substrate 11, and the lower waveguide layer 121, the multi-quantum well layer 122, and the upper waveguide layer 123 are stacked sequentially in a direction away from the substrate 11.

[0071] Specifically, the multi-quantum-well layer 122 is the region where stimulated emission occurs and optical signals are generated. When electrons and holes are injected into the multi-quantum-well layer 122, they are confined to move within a two-dimensional plane, generating a quantum size effect, thereby improving the carrier injection efficiency and gain, achieving lower threshold current, higher quantum efficiency, and better temperature stability. The lower waveguide layer 121 and the upper waveguide layer 123 optically confine and guide the optical signal generated by the multi-quantum-well layer 122, so that the optical signal is concentrated and confined to propagate within the active layer 12.

[0072] Furthermore, the lower waveguide layer 121, the multi-quantum well layer 122, and the upper waveguide layer 123 can all be made of InGaAlAs material, and the bandgap wavelength of the lower waveguide layer 121 and the upper waveguide layer 123 can be adjusted to be smaller than the bandgap wavelength of the multi-quantum well layer 122.

[0073] In the embodiments of this disclosure, the photofluorescence spectrum wavelength of the first active segment 12a is 1280nm~1300nm, and the photofluorescence spectrum wavelength of the second active segment 12b is 1230nm~1260nm.

[0074] Specifically, the photofluorescence wavelengths of the first active section 12a and the second active section 12b can be 1280 nm and 1240 nm, or 1290 nm and 1250 nm, respectively. The photofluorescence wavelength of the first active section 12a is greater than that of the second active section 12b, resulting in a narrower bandgap for the first active section 12a and thus a higher optical gain for the combined laser 1. The relatively smaller photofluorescence wavelength of the second active section 12b allows the wavelength of the optical signal to fall on the absorption edge of the modulator 2, thereby utilizing the quantum confinement Stark effect to control the on / off state of the optical signal through voltage.

[0075] Figure 3 A flowchart illustrating a method for fabricating an electroabsorption modulated laser according to an embodiment of the present disclosure is shown.

[0076] like Figure 3 The present disclosure also provides a method for fabricating an electroabsorption modulated laser, which may include operations S101 to S107.

[0077] For ease of understanding, the following is combined with Figures 4-12 Specific instructions for operations S101 to S107.

[0078] In operation S101, such as Figure 4 As shown, a substrate 11 is provided, and an active layer 12 is prepared on the surface of the substrate 11. The active layer 12 is divided into a first initial segment 12c and a second initial segment 12d along a first direction.

[0079] Specifically, substrate 11 can be a silicon-doped indium phosphide substrate, and then an active layer 12 is prepared on the surface of substrate 11 using MOCVD (metal-organic chemical vapor deposition) equipment.

[0080] In operation S102, such as Figure 5 and Figure 6 As shown, a silicon dioxide mask 19 is prepared on the surface of the first initial segment 12c, and the area of ​​the active layer 12 not covered by the silicon dioxide mask 19 is etched away to obtain the first active segment 12a.

[0081] Specifically, a silicon dioxide thin film is grown on the surface of the first active region 12a using PECVD (plasma-enhanced chemical vapor deposition) process, and a silicon dioxide mask 19 is etched using photolithography and hydrofluoric acid etching solution. The width of the silicon dioxide mask 19 along the second direction can be 10 μm to 30 μm. The second direction is perpendicular to the first direction and parallel to the surface of the substrate 11.

[0082] Then, the area of ​​the active layer 12 not covered by the silicon dioxide mask 19 is removed by inductively coupled plasma etching process. The silicon dioxide mask 19 protects the area it covers to prevent the covered area from being damaged by the etching and corrosion process, so that a part of the active layer 12 is retained. This retained part forms the first active segment 12a.

[0083] In operation S103, such as Figure 7 As shown, a second active section 12b is prepared on one side of the first active section 12a, and the first active section 12a and the second active section 12b together form a new active layer 12.

[0084] Specifically, material is grown on one side of the first active segment 12a using an MOCVD device. Since the semiconductor material only grows in the window region not covered by the silicon dioxide mask 19 and does not nucleate on the silicon dioxide mask 19, the fabricated second active segment 12b has the same width as the first active segment 12a in the second direction; and the second active segment 12b has the same thickness as the first active segment 12a in the direction perpendicular to the surface of the substrate 11. Therefore, the first active segment 12a and the second active segment 12b can form a physically continuous new active layer 12.

[0085] In operation S104, such as Figure 8 As shown, the silicon dioxide mask 19 is removed, and a grating 13 is fabricated on the surface of the first active section 12a.

[0086] Specifically, the silicon dioxide mask 19 is removed by wet etching to expose the surface of the first active section 12a, and then the grating 13 is etched on the surface of the first active section 12a.

[0087] In operation S105, such as Figure 9 As shown, a capping layer 14 and a contact layer 15 are fabricated layer by layer on the surface of the new active layer 12.

[0088] Specifically, a capping layer 14 is fabricated on the surface of the new active layer 12 using an MOCVD device, and then a contact layer 15 is fabricated on the surface of the capping layer 14 using an MOCVD device. The capping layer 14 is responsible for protecting the core structure of the electroabsorption modulated laser and maintaining its optical performance, while the contact layer 15, through its own band structure characteristics, is more conducive to the subsequent formation of metal-semiconductor ohmic contacts.

[0089] It should be noted that the capping layer 14 can be made of InP to confine the optical field, thereby helping to improve the far-field characteristics of the electroabsorption modulated laser and enhance its high-speed response performance. The contact layer 15 can be made of InGaAl to help achieve low-resistance contact, thus ensuring the efficient operation of the electroabsorption modulated laser.

[0090] Furthermore, in the embodiments of this disclosure, after the capping layer 14 and the contact layer 15 are fabricated layer by layer on the surface of the new active layer 12, the capping layer 14 and the contact layer 15 are etched to form a ridge waveguide structure.

[0091] Specifically, inductively coupled plasma etching is used to etch the capping layer 14 and the contact layer 15. The etched capping layer 14 and the contact layer 15 form a raised ridge, which is the ridge waveguide structure. The width of the ridge waveguide structure along the second direction can be 3 μm. This ridge waveguide structure confines the optical signal generated by the new active layer 12 to a narrow strip region below it, preventing lateral diffusion and thus reducing the transmission loss of the optical signal.

[0092] After etching is completed, the area where the capping layer 14 and contact layer 15 are removed will expose the new active layer 12 located in that area, and the sides of the ridge waveguide structure will also be exposed. Therefore, a silicon dioxide passivation layer needs to be deposited in the exposed area of ​​the new active layer 12 until the silicon dioxide passivation layer completely covers the exposed area of ​​the new active layer 12, the side exposed areas of the capping layer 14 and contact layer 15, and the top surface of the contact layer 15.

[0093] A silicon dioxide passivation layer provides physical isolation and protection for the new active layer 12, capping layer 14, and contact layer 15, preventing the semiconductor material from being contaminated or oxidized by contact with the external environment. Simultaneously, the silicon dioxide passivation layer forms an insulating isolation layer on both sides of the ridge waveguide structure. This ensures that the injected current flows strictly from the contact layer 15 at the top of the ridge through the new active layer 12 without leakage from the sides, thus guaranteeing current utilization efficiency.

[0094] In operation S106, such as Figure 10 As shown, multiple electrical isolation trenches 16 are etched on the contact layer 15 to form a first contact segment 15a, a second contact segment 15b, a third contact segment 15c, and a fourth contact segment 15d that are sequentially adjacent along the first direction.

[0095] Specifically, when etching multiple electrical isolation trenches 16 on the contact layer 15, the silicon dioxide passivation layer is also etched and separated together. After separating the contact layer 15, the electrical isolation trenches 16 do not extend downwards and do not separate the capping layer 14 and the new active layer 12. In this way, the contact layer 15 is divided into four segments without destroying the physical continuity of the new active layer 12.

[0096] Furthermore, in the embodiments of this disclosure, after etching a plurality of electrical isolation trenches 16 on the contact layer 15, helium ions are injected into each electrical isolation trench 16.

[0097] Specifically, after high-energy helium ions are injected into each electrical isolation trench 16, the helium ions in each electrical isolation trench 16 will enter the capping layer 14. During this process, the lattice atoms of the capping layer 14 located in the vicinity of each electrical isolation trench 16 will be damaged. These lattice damages caused by helium ion injection will transform the originally conductive semiconductor material into a high-resistivity state, thereby completely cutting off the current path between two adjacent devices in electrical terms and achieving electrical isolation.

[0098] In operation S107, such as Figure 11 As shown, a multi-segment P-type electrode 17 is fabricated on the surface of the etched contact layer 15, and the P-type electrode 17 located on the surface of the first contact segment 15a is electrically connected to the P-type electrode 17 located on the surface of the third contact segment 15c.

[0099] Specifically, a window is opened in the silicon dioxide passivation layer on the top surface of the contact layer 15 to expose the top surface of the contact layer 15. Then, a P-type electrode 17 is deposited in the exposed area of ​​the contact layer 15 using an electron beam evaporation process. A P-type electrode 17 is provided on each segment of the contact layer 15, and multiple P-type electrodes 17 together constitute a complete P-type electrode 17.

[0100] After the P-type electrode 17 is fabricated, a conductive bridge is deposited on the silicon dioxide passivation layer. The conductive bridge is used to electrically connect the P-type electrode 17 located on the surface of the first contact section 15a and the P-type electrode 17 located on the surface of the third contact section 15c, thereby realizing the electrical connection between the first laser 1a and the third laser 1c.

[0101] In operation S108, such as Figure 12 As shown, an N-type electrode 18 is fabricated on the side of the substrate 11 away from the new active layer 12, thus completing the fabrication of the electroabsorption modulated laser.

[0102] Specifically, before fabricating the N-type electrode 18, the substrate 11 can be thinned to achieve a balance between mechanical strength, heat dissipation performance, and electrical performance. Then, the N-type electrode 18 can be deposited on the side of the substrate 11 away from the new active layer 12 using an electron beam evaporation process, thus completing the fabrication of the electroabsorption modulated laser.

[0103] According to embodiments of this disclosure, the method for fabricating an electroabsorption modulated laser of this disclosure forms a first laser 1a responsible for generating an optical signal, a second laser 1b responsible for tuning the wavelength of the optical signal, a third laser 1c responsible for assisting in generating the optical signal and guiding the high-power transmission of the optical signal to the modulator 2, and a modulator 2 responsible for realizing high-bandwidth transmission of the optical signal by dividing the active layer 12 and the contact layer 15 respectively. Thus, high-bandwidth transmission of the optical signal and continuous tunability of the optical signal wavelength are achieved through simple processes and conventional semiconductor materials.

[0104] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. An electroabsorption modulated laser, characterized in that, include: Substrate (11); An active layer (12) is formed on the surface of the substrate (11), and the active layer (12) is divided into an adjacent first active segment (12a) and a second active segment (12b) along a first direction. A grating (13) is disposed on the surface of the first active section (12a); A capping layer (14) is formed on the surface of the active layer (12); A contact layer (15) is formed on the surface of the cover layer (14), the contact layer (15) being divided by a plurality of electrical isolation trenches (16) into a first contact segment (15a), a second contact segment (15b), a third contact segment (15c) and a fourth contact segment (15d) that are sequentially adjacent along the first direction. The first active section (12a), the grating (13), the capping layer (14) and the first contact section (15a) constitute a first laser (1a) for generating optical signals by electrical injection. The first active section (12a), the grating (13), the capping layer (14) and the second contact section (15b) constitute a second laser (1b) for adjusting the wavelength of the optical signal by thermal tuning of the phase caused by electrical injection; The first active section (12a), the grating (13), the capping layer (14) and the third contact section (15c) constitute a third laser (1c), which is used to generate an optical signal together with the first laser (1a) through electrical injection; The second active section (12b), the capping layer (14), and the fourth contact section (15d) constitute a modulator (2) for realizing high-bandwidth transmission of optical signals.

2. The electroabsorption modulated laser according to claim 1, characterized in that, The injection current of the first laser (1a) is different from that of the second laser (1b), and the injection current of the first laser (1a) is the same as that of the third laser (1c).

3. The electroabsorption modulated laser according to claim 1, characterized in that, Also includes: The P-type electrode (17) is formed in multiple segments on the surface of each segment of the contact layer (15); An N-type electrode (18) is formed on the side of the substrate (11) away from the active layer (12).

4. The electroabsorption modulated laser according to claim 3, characterized in that, The P-type electrode (17) on the surface of the first contact section (15a) is electrically connected to the P-type electrode (17) on the surface of the third contact section (15c).

5. The electroabsorption modulated laser according to claim 1, characterized in that, The first contact segment (15a), the second contact segment (15b), and the third contact segment (15c) together constitute the laser segment of the contact layer (15); Wherein, the first contact segment (15a) accounts for 50% to 60% of the length of the laser segment along the first direction, the second contact segment (15b) accounts for 10% to 20% of the length of the laser segment along the first direction, and the third contact segment (15c) accounts for 20% to 30% of the length of the laser segment along the first direction.

6. The electroabsorption modulated laser according to claim 1, characterized in that, The active layer (12) includes a lower waveguide layer (121), a multi-quantum well layer (122), and an upper waveguide layer (123). The lower waveguide layer (121) is formed on the surface of the substrate (11), and the lower waveguide layer (121), the multi-quantum well layer (122), and the upper waveguide layer (123) are stacked sequentially in a direction away from the substrate (11).

7. The electroabsorption modulated laser according to claim 1, characterized in that, The photofluorescence spectrum wavelength of the first active segment (12a) is 1280nm~1300nm, and the photofluorescence spectrum wavelength of the second active segment (12b) is 1230nm~1260nm.

8. A method for fabricating an electroabsorption modulated laser, characterized in that, include: A substrate (11) is provided, and an active layer (12) is formed on the surface of the substrate (11). The active layer (12) is divided into a first initial segment (12c) and a second initial segment (12d) along a first direction. A silicon dioxide mask (19) is prepared on the surface of the first initial segment (12c), and the area of ​​the active layer (12) not covered by the silicon dioxide mask (19) is etched away to obtain the first active segment (12a). A second active segment (12b) is prepared on one side of the first active segment (12a), and the first active segment (12a) and the second active segment (12b) together form a new active layer (12). Remove the silicon dioxide mask (19) and fabricate a grating (13) on the surface of the first active section (12a). A capping layer (14) and a contact layer (15) are prepared layer by layer on the surface of the new active layer (12). Multiple electrical isolation trenches (16) are etched on the contact layer (15) to form a first contact segment (15a), a second contact segment (15b), a third contact segment (15c) and a fourth contact segment (15d) that are sequentially adjacent along the first direction. A multi-segment P-type electrode (17) is fabricated on the surface of the etched contact layer (15), and the P-type electrode (17) located on the surface of the first contact segment (15a) is electrically connected to the P-type electrode (17) located on the surface of the third contact segment (15c). An N-type electrode (18) is fabricated on the side of the substrate (11) away from the new active layer (12), thus completing the fabrication of the electroabsorption modulated laser.

9. The method for fabricating an electroabsorption modulated laser according to claim 8, characterized in that, Also includes: After the capping layer (14) and the contact layer (15) are fabricated layer by layer on the surface of the new active layer (12), the capping layer (14) and the contact layer (15) are etched to form a ridge waveguide structure.

10. The method for fabricating an electroabsorption modulated laser according to claim 8, characterized in that, Also includes: After etching multiple electrical isolation trenches (16) on the contact layer (15), helium ions are injected into each of the electrical isolation trenches (16).

Images