Monolithic integrated laser chip and preparation method and application thereof

Abstract

The invention relates to the technical field of laser chips, in particular to a monolithic integrated laser chip and a preparation method and application thereof. The method comprises the following steps of: growing a buffer layer material on a substrate, respectively growing corresponding active materials on a laser region, an amplifier region and a modulator region, covering a second dielectric mask, covering a silicon dioxide material on the surfaces of the second rectangular dielectric mask and the buffer material, photoetching to form a photoresist mask pattern, and forming a second dielectric mask pattern on the surface of the second dielectric mask. A silicon dioxide mask pattern is formed by hydrofluoric acid corrosion, a passive waveguide material is grown, an active material of a laser region is covered with a grating structure, a cladding material and a contact layer material are grown, and photoresist mask patterns are symmetrically arranged on the two sides of the central axis of the laser region, the amplifier region and the modulator region. The width of the silicon dioxide mask pattern in the laser area and the amplifier area is Wa, the width of the silicon dioxide mask pattern in the modulator area is Wm, and Wm is larger than Wa. The transmission loss of light among different areas is reduced, and the far-field divergence angle of the device is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of laser chips, and in particular to a monolithic integrated laser chip and a preparation method and application thereof. Background Art

[0002] Electroabsorption modulated distributed feedback semiconductor lasers (EMLs) are the most promising optical signal sources in wavelength division multiplexing networks. The main reason is that this integrated device has many unique advantages, such as: small size, easy to mass produce, and therefore relatively low cost; low operating voltage, low power consumption; high optical coupling efficiency, low insertion loss; no need to consider polarization issues; stable and reliable structure; most importantly, easy to integrate with other semiconductor optoelectronic devices on a single chip, and strong functional scalability. Therefore, EMLs have been one of the research hotspots of major optoelectronic device companies and scientific research institutions at home and abroad for many years.

[0003] The thickness of quantum well materials in the modulator region of EMLs chips is generally greater than that in the laser region. This, on the one hand, increases the optical transmission loss from the laser to the modulator, and on the other hand, also leads to a large far-field divergence angle at the modulator end, reducing its coupling efficiency with the optical fiber. Summary of the invention

[0004] The purpose of the present invention is to propose a monolithic integrated laser chip and its preparation method and application, which realizes the gradual thickness change of the passive waveguide core material in the isolation area of ​​the EMLs chip between the modulator and the laser and amplifier, which is beneficial to reduce the transmission loss of light between different areas.

[0005] To this end, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a monolithically integrated laser chip in an optional embodiment, comprising the following steps:

[0007] S1: growing a buffer layer material on a substrate, growing an active material for forming a laser and an amplifier on the buffer layer material, setting a laser region and an amplifier region on the active material, covering the active material in the laser region and the amplifier region with a first rectangular dielectric mask, then selectively removing the active material outside the laser region and the amplifier region, then butt-growing a modulator active material in the region outside the laser region and the amplifier region, and finally removing the first rectangular dielectric mask;

[0008] S2: a modulator region is provided on the modulator active material, and then a second rectangular dielectric mask is covered on the laser region, the amplifier region and the modulator region, and the modulator active material outside the laser region, the amplifier region and the modulator region is selectively removed, and then a silicon dioxide material is covered on the surface of the second rectangular dielectric mask and the buffer material, and a photoresist mask pattern is formed by photolithography, and the silicon dioxide material in the area outside the photoresist mask pattern is corroded by hydrofluoric acid to form a silicon dioxide mask pattern;

[0009] S3: After the passive waveguide material is butt-grown in the areas outside the laser area, the amplifier area and the modulator area, the second dielectric mask is removed, the grating structure is covered on the active material in the laser area, and finally the cladding material and the contact layer material are grown in sequence;

[0010] Wherein, in step S2, the photoresist mask pattern is symmetrically arranged on both sides of the central axis of the laser area, the amplifier area and the modulator area, the width of the silicon dioxide mask pattern in the laser area and the amplifier area is Wa, and the width in the modulator area is Wm, Wm>Wa.

[0011] In the present invention, the thickness of the passive waveguide core material in the isolation area of ​​the EML chip is gradually changed between the modulator and the laser and amplifier by using the selective area epitaxy technology, which is beneficial to reducing the transmission loss of light between different areas. At the same time, the output waveguide area with gradually decreasing thickness of the passive waveguide material is obtained by using the selective area epitaxy technology, which is beneficial to reducing the far-field divergence angle of the device.

[0012] Preferably, there is an isolation region between the modulator region and the laser region. In step S2, the width of the isolation region of the silicon dioxide mask pattern in the direction from the modulator region to the laser region gradually changes from Wm to Wa, and the gradual change is linear or nonlinear.

[0013] Preferably, there is a second isolation region between the modulator region and the amplifier region. In step S2, the width of the silicon dioxide mask pattern in the second isolation region from the modulator region to the amplifier region gradually changes from Wm to Wa, and the gradual change is linear or nonlinear.

[0014] Preferably, there is an output waveguide region on the side of the amplifier region away from the modulator region. In step S2, the width of the silicon dioxide mask pattern in the output waveguide region gradually changes from Wa to 0, and the gradual change is linear or nonlinear.

[0015] Preferably, the height of the active material in the laser region and the amplifier region is Ta, the height of the active material in the modulator region is Tm, and Tm>Ta.

[0016] Preferably, in the isolation zone 1, the thickness of the passive waveguide material increases from the edge of the laser zone to the edge of the modulator zone. In the isolation zone 2, the thickness of the passive waveguide material decreases from the edge of the modulator zone to the edge of the amplifier zone. In the output waveguide zone, the thickness of the passive waveguide material decreases from the edge of the amplifier zone to the light-emitting end face.

[0017] In a second aspect, the present invention provides a monolithic integrated laser chip in an optional embodiment, characterized in that it is prepared by the above-mentioned preparation method.

[0018] In a third aspect, the present invention provides, in an optional embodiment, an electro-absorption modulated distributed feedback semiconductor laser, characterized in that it comprises the above-mentioned monolithic integrated laser chip.

[0019] Compared with the prior art, the present invention has one of the following beneficial effects:

[0020] The present invention uses the selective area epitaxy technology to achieve a gradual change in thickness of the passive waveguide core material in the isolation area of ​​the EMLs chip between the modulator and the laser and amplifier, which is beneficial to reducing the transmission loss of light between different areas. At the same time, the selective area epitaxy technology is used to obtain an output waveguide area with a gradually decreasing thickness of the passive waveguide material, which is beneficial to reducing the far-field divergence angle of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The advantages of the above and / or additional aspects of the present application will become apparent and easily understood in the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 It is a top view of a mask pattern during the manufacturing process of a monolithically integrated laser chip in Example 1 of the present invention;

[0023] Figure 2 It is a structural cross-sectional view of the chip at each stage in the manufacturing process of the monolithic integrated laser chip in Example 1 of the present invention;

[0024] Among them, 10-substrate, 20-buffer layer material, 30-laser and amplifier active material, 31-first rectangular dielectric mask, 32-second rectangular dielectric mask, 33-silicon dioxide material layer, 34-silicon dioxide mask pattern, 35-grating structure, 40-modulator active material, 50-passive waveguide material, 60-cladding material, 70-contact layer material. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0026] In the following description, many specific details are elaborated to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited to the specific embodiments disclosed below.

[0027] The technical solution of the present invention will be described in detail below in conjunction with embodiments and drawings.

[0028] Example 1

[0029] Please refer to the attached Figure 1-2 Taking the InP-based material system as an example, this embodiment provides a method for preparing a monolithic integrated laser chip, comprising the following steps:

[0030] Step 1: Grow an n-type InP buffer layer material 20 on an n-type InP substrate 10, and grow an active material 30 for forming a laser (LD) and an amplifier (SOA) on top of the n-type InP buffer layer material 20, which is an InGaAsP or InGaAlAs multiple quantum well material with a thickness of Ta.

[0031] Step 2: Set the laser region and amplifier region on the active material 30 of the laser and amplifier, and cover the active material of the laser region and the amplifier region with a first rectangular dielectric mask 31 of silicon nitride (SiN) (see Figure 1 a), after selectively removing 30% of the laser and amplifier active materials outside the LD and SOA regions (see Figure 2 a), and then grow the modulator active material 40 in the area outside the laser area and the amplifier area, which is InGaAsP or InGaAlAs multi-quantum well material with a thickness of Tm, Tm>Ta( Figure 2 b), finally removing the first rectangular dielectric mask 31.

[0032] Step 3: A modulator region (EAM) is provided on the modulator active material 40, and then a SiN second rectangular dielectric mask 32 (see FIG. Figure 1 b), then selectively removing the modulator active material 40 outside the laser region, amplifier region and modulator region (see Figure 2 c).

[0033] Step 4: Then deposit silicon dioxide (SiO2) material 33 to cover the surface of the second rectangular dielectric mask and the buffer material (see Figure 1 c), photolithography forms a photoresist mask pattern, and HF is used to etch the silicon dioxide material in the area outside the photoresist mask pattern to form a silicon dioxide mask pattern 34 (see Figure 1d). When fabricating the silica mask pattern 34, first form a photoresist pattern by photolithography, and then etch the silica material outside the photoresist using HF. During this process, the silica material on top of the second rectangular dielectric mask 32 is also etched away. The second rectangular dielectric mask 32 is made of silicon nitride material, and its etching rate is relatively slow. After obtaining the silica mask pattern 34 by etching, the second rectangular dielectric mask 32 remains. As Figure 1 shown in d, the silica mask pattern 34 includes two parts, symmetrically distributed on both sides of the central axis of the quantum wells in the laser region, amplifier region, and modulator region. Its width in the LD region and SOA region is Wa, and its width in the EAM region is Wm, where Wa < Wm. Moreover, the mask width of the silica mask pattern 34 increases from Wa to Wm in the isolation region 1 (S1), decreases from Wm to Wa in the isolation region 2 (S2), and decreases from Wm to 0 in the output waveguide region (WG). The gradual change in the mask width can be a linear gradient or a non-linear gradient.

[0034] Step 5: Use the new metalorganic chemical vapor deposition (MOCVD) technology to epitaxially grow the InGaAsP passive waveguide material 50 in the regions outside the laser region, amplifier region, and modulator region (see Figure 2 d), and then remove the second dielectric mask 32. During the epitaxial growth process, the material only grows in the regions outside the second rectangular dielectric mask 32 and the silica mask pattern 34, which is the so-called selective area epitaxial growth. The presence of the silica mask pattern 34 makes the growth rate of the material in its middle region greater than that in the region without the pattern, and the greater the mask width and the smaller the spacing, the greater the growth rate. Therefore, after the epitaxial growth is completed, the thickness of the passive waveguide material in the S1 region increases from the laser end to the modulator end, the passive waveguide material in the S2 region decreases from the modulator end to the amplifier end, and the thickness of the passive waveguide material in the WG region decreases from the amplifier end to the light-emitting end face. In the S1 and S2 regions, the gradual change in the waveguide material thickness reduces the optical transmission loss from the laser to the modulator and from the modulator to the amplifier. In the WG region, the reduction in the waveguide thickness is beneficial to increasing the far-field divergence angle of the light-emitting end face of the device, thereby improving the coupling efficiency between the device and the optical fiber.

[0035] Step 6: After fabricating the grating structure 35 on the active material in the LD region, sequentially grow the InP cladding material 60 and the InGaAs contact layer material 70 (see Figure 2 e).

[0036] In addition, the inventor noticed that the edge slope of the transition part between the S1 region and the S2 region will affect the performance of the laser. The optimal slope is between 4 - 25 degrees. Too large or too small a slope will affect the coupling efficiency.

[0037] Although the present application is disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and are not intended to limit the application of the present application. The scope of protection of the present application is defined by the appended claims and may include various modifications, alterations and equivalents made to the invention without departing from the scope and spirit of the present application.

Claims

1. A method for preparing a monolithic integrated laser chip, characterized in that: The following steps are involved: S1: growing a buffer layer material on a substrate, growing an active material for forming a laser and an amplifier on the buffer layer material, setting a laser region and an amplifier region on the active material, covering the active material in the laser region and the amplifier region with a first rectangular dielectric mask, then selectively removing the active material outside the laser region and the amplifier region, then butt-growing a modulator active material in the region outside the laser region and the amplifier region, and finally removing the first rectangular dielectric mask; S2: a modulator region is provided on the modulator active material, and then a second rectangular dielectric mask is covered on the laser region, the amplifier region and the modulator region, and the modulator active material outside the laser region, the amplifier region and the modulator region is selectively removed, and then a silicon dioxide material is covered on the surface of the second rectangular dielectric mask and the buffer material, and a photoresist mask pattern is formed by photolithography, and the silicon dioxide material in the area outside the photoresist mask pattern is corroded by hydrofluoric acid to form a silicon dioxide mask pattern; S3: After the passive waveguide material is butt-grown in the areas outside the laser area, the amplifier area and the modulator area, the second dielectric mask is removed, the grating structure is covered on the active material in the laser area, and finally the cladding material and the contact layer material are grown in sequence; Wherein, in step S2, the photoresist mask pattern is symmetrically arranged on both sides of the central axis of the laser area, the amplifier area and the modulator area, the width of the silicon dioxide mask pattern in the laser area and the amplifier area is Wa, and the width in the modulator area is Wm, Wm>Wa.

2. The method for preparing a monolithically integrated laser chip according to claim 1, characterized in that: There is an isolation region between the modulator region and the laser region. In step S2, the width of the isolation region of the silicon dioxide mask pattern in the direction from the modulator region to the laser region gradually changes from Wm to Wa, and the gradual change is linear gradual change or nonlinear gradual change.

3. The method for preparing a monolithically integrated laser chip according to claim 1, characterized in that: There is an isolation zone II between the modulator zone and the amplifier zone. In step S2, the width of the isolation zone II of the silicon dioxide mask pattern in the direction from the modulator zone to the amplifier zone gradually changes from Wm to Wa, and the gradual change is linear gradual change or nonlinear gradual change.

4. The method for preparing a monolithically integrated laser chip according to claim 1, characterized in that: There is also an output waveguide region on the side of the amplifier region away from the modulator region. In step S2, the width of the silicon dioxide mask pattern in the output waveguide region gradually changes from Wa to 0, and the gradual change is linear or nonlinear.

5. The method for preparing a monolithically integrated laser chip according to claim 1, characterized in that: The height of the active material in the laser region and the amplifier region is Ta, and the height of the active material in the modulator region is Tm, where Tm>Ta.

6. The method for preparing a monolithically integrated laser chip according to claim 2, characterized in that: In the isolation region, the thickness of the passive waveguide material increases from the edge of the laser region to the edge of the modulator region.

7. The method for preparing a monolithically integrated laser chip according to claim 3, characterized in that: In the second isolation region, the thickness of the passive waveguide material decreases from the edge of the modulator region to the edge of the amplifier region.

8. The method for preparing a monolithically integrated laser chip according to claim 3, characterized in that: In the output waveguide region, the thickness of the passive waveguide material decreases from the edge of the amplifier region to the light-emitting end face.

9. A monolithic integrated laser chip, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. An electro-absorption modulated distributed feedback semiconductor laser, characterized in that: Comprising the monolithically integrated laser chip as claimed in claim 9.

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