Broadband tunable light emission chip based on asymmetric multi-quantum well technology and preparation method

Abstract

The invention provides a broadband tunable light emitting chip based on an asymmetric multi-quantum well technology and a preparation method, the tunable light emitting chip comprises a plurality of laser units distributed in columns, and each column of laser units comprises a plurality of lasers connected in series; the laser units achieve single-waveguide laser output through cascade Y waveguide combination, each laser comprises an asymmetric multi-quantum well layer and a grating layer, the thickness of each quantum well is gradually decreased from top to bottom, and a grating is located on the surface of the upper limiting layer. The tunable lasers connected in series and in parallel are adopted, and single-waveguide laser output is achieved through cascade Y waveguide combination; the asymmetric multiple quantum wells are arranged, so that the overall tunable range of the laser can be widened; a sampling grating is manufactured through a reconstruction equivalent chirp technology to select a lasing wavelength, and pi phase shift is introduced to carry out phase matching so as to ensure single wavelength output; according to the invention, gains can be provided for a plurality of laser units, the density of monolithic integration is improved, the transmission capacity is increased, and the single-mode yield is improved.

Description

Technical field:

[0001] The present invention belongs to the technical field of optoelectronic chips, and in particular relates to a broadband tunable light emitting chip based on asymmetric multiple quantum well technology and a preparation method thereof. Background technology:

[0002] With the rapid development of advanced technologies such as artificial intelligence (AI) and the Internet of Things (IoT), tunable lasers with wide wavelength tuning ranges are becoming crucial in future data centers, metropolitan area transmission, and access networks using dense wavelength division multiplexing (DWDM) systems. With the rapid growth in data transmission demand, traditional fixed-wavelength lasers are no longer able to meet the flexibility and scalability requirements. Tunable lasers, with their variable wavelength characteristics, can replace fixed-wavelength lasers, significantly reducing system size and cost while helping to achieve high network capacity. This characteristic makes tunable lasers play a central role in modern communication systems. Furthermore, tunable lasers with wide wavelength tuning ranges are widely used in optical sensing systems such as fiber optic sensing, light detection and ranging (LiDAR), and gas detection. Fiber optic sensors rely on the high sensitivity and wide tuning range of lasers to accurately measure various physical quantities. In LiDAR technology, fast, broadband, and continuously tunable lasers can improve the measurement range and accuracy, making this technology widely used in fields such as autonomous driving, terrain mapping, and environmental monitoring. At the same time, the field of gas detection also relies on the precise wavelength tuning capability of tunable lasers to perform effective gas analysis under different environmental conditions.

[0003] In current research, various types of tunable lasers have been proposed, including sampled grating distributed Bragg reflector (SG-DBR) lasers, tunable microelectromechanical vertical cavity surface emitting lasers (MEMS-VCSELs), external cavity tunable lasers (ECTLs), and tunable multi-wavelength distributed feedback (DFB) laser arrays (TMLAs). Although these lasers have their own advantages in performance, their tuning capabilities are generally limited and cannot meet the needs of high-bandwidth applications. For example, the wavelength tuning range of SG-DBR lasers is narrow and mode hopping is prone to occur; the tuning range of MEMS-VCSELs is limited by the mechanical motion amplitude and the tuning speed is slow; although ECTLs have a large wavelength coverage range, their tuning mechanism is complex, the integration is low, and the spectral purity is insufficient. In response to the above problems, the present invention designs a new laser to improve the wavelength tuning range while maintaining its excellent single longitudinal mode (SLM) characteristics and high stability to meet the needs of broadband, high-precision, and high-reliability application scenarios. Summary of the invention:

[0004] The present invention addresses the shortcomings of existing technologies by providing a broadband tunable optical transmitter chip based on asymmetric multi-quantum well technology and its fabrication method. By applying asymmetric quantum well technology, the gain range of the laser is effectively expanded, enabling a wider range of wavelength tuning and significantly improving the transmission capacity in dense wavelength division multiplexing (DWDM) systems. Furthermore, a reconstructed equivalent chirp technique is employed to fabricate the sampled grating, enabling precise mode selection. A π phase shift is introduced to optimize the yield of single-mode laser output, ensuring greater stability and efficiency.

[0005] The present invention adopts the following technical solutions:

[0006] The present invention provides a broadband tunable light emitting chip based on asymmetric multi-quantum well technology, comprising a plurality of laser units distributed in columns, each column of laser units comprising a plurality of lasers connected in series; the plurality of laser units are combined by cascading Y-waveguides to achieve single-waveguide laser output; the laser comprises an asymmetric multi-quantum well layer.

[0007] Furthermore, the asymmetric multi-quantum well layer includes a plurality of compressively strained InGaAlAs quantum wells and a plurality of tensilely strained InGaAlAs quantum barriers, and the compressively strained InGaAlAs quantum wells and the tensilely strained InGaAlAs quantum barriers are spaced and distributed.

[0008] Furthermore, in the plurality of compressively strained InGaAlAs quantum wells, the photoluminescence wavelength of each compressively strained InGaAlAs quantum well gradually decreases from top to bottom, thereby increasing the gain range of the light emitting chip and thereby increasing the tunable range of the light emitting chip.

[0009] Furthermore, among the plurality of compressively strained InGaAlAs quantum wells, the thickness and gallium / indium content of the material components of each compressively strained InGaAlAs quantum well decreases from top to bottom.

[0010] Furthermore, the laser also includes a grating layer, fabricated using a reconstruction equivalent chirp technique. A uniformly periodic sampled grating is produced through a single holographic exposure and a single holographic lithography process. The sampled grating uses the +1 order of the grating as the primary mode to select the lasing wavelength. The lasing wavelength of each laser can be selected by varying the sampling period of the holographic lithography process.

[0011] Furthermore, the sampled grating is provided with a π phase shift for phase matching to ensure single wavelength output, and the π phase shift is distributed at the center of the sampled grating.

[0012] Furthermore, the number of the compressively strained InGaAlAs quantum wells is 5, and the number of the tensilely strained InGaAlAs quantum barriers is 6.

[0013] Furthermore, the broadband tunable light emitting chip also includes a substrate, a buffer layer, a lower confinement layer, an upper confinement layer, a corrosion barrier layer, a waveguide layer and a contact layer; the broadband tunable light emitting chip is composed of a substrate, a buffer layer, a lower confinement layer, an asymmetric multi-quantum well layer, an upper confinement layer, a grating layer, a corrosion barrier layer, a waveguide layer and a contact layer stacked from bottom to top.

[0014] (2) The present invention also provides a method for preparing the broadband tunable light emitting chip based on the asymmetric multi-quantum well technology described above, comprising the following steps:

[0015] Step S1: growing a buffer layer, a lower confinement layer, an asymmetric multi-quantum well layer with a gradient gallium / indium content and thickness, and an upper confinement layer in sequence on the upper surface of the substrate by metal organic compound vapor deposition;

[0016] Step S2: a grating layer is fabricated on the upper confinement layer by reconstructing an equivalent chirp technique, and InP is deposited on the grating layer to bury the grating layer;

[0017] Step S3: sequentially growing a corrosion barrier layer, a waveguide layer, and a contact layer on the deposited InP grating layer;

[0018] Step S4: etching the waveguide layer and the contact layer to form a ridge shape, thereby forming electrical isolation between each laser to prevent crosstalk;

[0019] Step S5: growing a p-side metal electrode in the ridge region above the contact layer, growing an n-side electrode at the bottom of the substrate, thinning and polishing the n-side electrode, and annealing the laser high-temperature alloy;

[0020] Step S6: cleaving the chip to obtain the tunable light emitting chip device.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention uses tunable lasers connected in series and in parallel to achieve single-waveguide laser output through cascaded Y-waveguide combining. Compared with traditional tunable lasers, the present invention has the advantage of reducing the volume of the required laser chip, which is conducive to its higher-density integration. Secondly, the light source of the series-parallel laser of the present invention uses Y-combining to combine multiple waveguide light sources into a single waveguide light source output. In practical applications, single-waveguide light sources have very mature packaging technology and low packaging difficulty, which is conducive to their product application. In comparison, the packaging of multi-waveguide light sources is difficult, and there is currently no mature packaging solution.

[0023] (2) The present invention sets an asymmetric multi-quantum well, which can broaden and increase the overall tunable range of the laser;

[0024] (3) The present invention selects the lasing wavelength by reconstructing the equivalent chirp technique to produce a sampled grating, and introduces a π phase shift for phase matching to ensure single wavelength output;

[0025] (4) The present invention can provide gain for multiple laser units, improve the density of monolithic integration, increase the transmission capacity, and improve the single-mode yield, making it advantageous for application in DWDM systems. Description of the drawings:

[0026] Figure 1 Schematic diagram of the structure of a tunable optical transmitter chip according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of an asymmetric quantum well according to an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of the gain spectrum of the asymmetric quantum well structure according to an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the transmission spectrum of the tunable light emitting chip of the present invention at typical wavelengths;

[0030] Figure 5 Schematic diagram of the spectrum of the tunable light emitting chip according to an embodiment of the present invention. Specific implementation method:

[0031] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0032] Example 1

[0033] The present invention provides a broadband tunable light emitting chip based on asymmetric multi-quantum well technology, which is a distributed feedback laser array based on series and parallel connections. The tunable laser is combined by cascading Y-waveguides to achieve single-waveguide laser output.

[0034] The tunable light emitting chip structure includes a substrate, a buffer layer, a lower confinement layer, an asymmetric multi-quantum well layer, an upper confinement layer, a grating layer, a corrosion barrier layer, a waveguide layer and a contact layer, which are stacked from bottom to top in sequence: substrate, buffer layer, lower confinement layer, asymmetric multi-quantum well layer, upper confinement layer, grating layer, corrosion barrier layer, waveguide layer and contact layer.

[0035] Reference Figures 1-2The tunable optical emission chip includes several laser units (8 columns) distributed in columns. Each column of laser units includes 4 lasers connected in series. The electrode layers and waveguide layers of the 4 lasers connected in series are discontinuous to form electrical isolation between each laser to prevent crosstalk. The 8 columns of laser units achieve single waveguide laser output through cascaded Y-waveguide combining. Specifically, Figure 1 As shown, in the 8 columns of laser units, two adjacent columns of lasers are combined to form 4 first combined beams, the 4 first combined beams are combined in pairs to form 2 second combined beams, and the 2 second combined beams are combined again to realize single waveguide laser output.

[0036] Reference Figure 2 The asymmetric multi-quantum well layer includes 5 compressively strained InGaAlAs quantum wells and 6 tensile strained InGaAlAs quantum barriers. The compressively strained InGaAlAs quantum wells and the tensile strained InGaAlAs quantum barriers are distributed at intervals and are wrapped by confining heterostructures outside the top and bottom InGaAlAs quantum barriers respectively.

[0037] Among them, in the five compressively strained InGaAlAs quantum wells, the thickness and gallium / indium content of each compressively strained InGaAlAs quantum well decrease from top to bottom, which in turn causes the photoluminescence wavelength of each compressively strained InGaAlAs quantum well to gradually decrease from top to bottom, thus forming a multi-quantum well structure with asymmetric composition and thickness characteristics, increasing the gain range of the light emitting chip and thus increasing the tunable range of the light emitting chip. Specifically, Figure 2 As shown in the figure, the emission wavelengths of the five compressively strained InGaAlAs quantum wells are 1.58μm, 1.56μm, 1.54μm, 1.52μm, and 1.50μm, respectively, from top to bottom. This gradual change in composition and thickness effectively regulates the distribution of photoluminescence wavelengths, broadens the modal gain range of the laser array, and provides a larger tuning range for each laser.

[0038] The asymmetric quantum well technology provided by the present invention can be applied to lasers of any wavelength band, including the O-band, C-band, and L-band commonly used in communications.

[0039] In the embodiment of the present invention, the gratings are located on the surface of the upper confinement layer and are arranged periodically and uniformly. By adjusting the grating period, the emission wavelength of each laser can be precisely controlled.

[0040] The grating layer is fabricated using a reconstructed equivalent chirp technique: a single holographic exposure and a single holographic lithography process are used to create sampled gratings with different sampling periods. Different sampling periods achieve different lasing wavelengths, and the number of sampled gratings matches the number of lasers. The sampled gratings use the +1 level of the grating as the primary mode to select the lasing wavelength. The lasing wavelength of each laser can be selected by varying the sampling period of the holographic lithography.

[0041] In addition, each sampled grating is provided with a π phase shift structure, which is distributed at the center of the sampled grating to achieve phase matching, thereby ensuring the single wavelength stable output of the laser.

[0042] Therefore, the present invention proposes a tunable light emitting chip with simple design and processing technology and excellent performance. Through asymmetric quantum well and grating π phase shift technology, it not only expands the tuning range but also ensures stable single-mode output.

[0043] Example 2

[0044] This embodiment provides a method for preparing a broadband tunable light emitting chip based on asymmetric multi-quantum well technology as described in Example 1. The tunable light emitting chip uses asymmetric quantum well technology to broaden the gain range, thereby increasing the wavelength tunability range. The lasing wavelength is selected using the reconstructed equivalent chirp technique, which specifically includes the following steps:

[0045] Step S1: sequentially growing a buffer layer, a lower confinement layer, and an asymmetric multi-quantum well layer with a gradual variation in gallium / indium content and thickness on the upper surface of the substrate by metal organic compound vapor deposition; and depositing an upper confinement layer on the upper surface of the asymmetric multi-quantum well layer by metal organic compound vapor deposition.

[0046] Step S2: a grating layer is fabricated on the upper confinement layer by reconstructing an equivalent chirp technique to produce laser units with different grating sampling periods, and InP is deposited on the grating layer to bury the grating layer.

[0047] Step S3: sequentially growing a corrosion barrier layer, a waveguide layer and a contact layer on the deposited InP grating layer.

[0048] Step S4: Etching the waveguide layer and the contact layer to form a ridge shape, so that the waveguide layer and the contact layer of each serially connected laser are disconnected, and electrical isolation is formed between each laser to prevent crosstalk.

[0049] Step S5: growing a p-side metal electrode in the ridge region above the contact layer, growing an n-side electrode at the bottom of the substrate, thinning and polishing the n-side electrode, and annealing the laser high-temperature alloy.

[0050] Step S6: cleaving the chip to obtain the tunable light emitting chip device.

[0051] The grating layer of each laser unit in the laser array is designed and manufactured by reconstructing the equivalent chirp technology, as follows:

[0052] First, a single UV exposure is performed to create a uniform grating with a grating period of Λ0. Holographic lithography is then used to sample the uniform grating. The +1 order of the grating is used as the primary lasing mode, and an equivalent π phase shift is introduced in each laser unit to achieve stable single-mode characteristics. The +1 order grating period of the laser is determined by the uniform grating period and the sampling period, as shown in the following formula.

[0053]

[0054] Among them, Λ +1 represents the +1-order grating period after holographic lithography, Λ0 represents the uniform grating period defined by UV lithography, and p represents the sampling period of the grating.

[0055] Effect test:

[0056] 1. Simulation test:

[0057] The asymmetric quantum well structure described in Example 1 is simulated, and the schematic diagram of its structural gain spectrum is shown in FIG. Figure 3 .Depend on Figure 3 It can be seen that the gain range of the laser using this structure is 1460nm-1580nm. Within this range, the grating is used to select the wavelength of the laser, which provides guidance for the manufacture of actual lasers.

[0058] The transmission spectrum of the tunable light emitting chip at a typical wavelength described in Example 1 is shown in FIG. Figure 4 ,Depend on Figure 4 It can be seen that the transmission spectrum of a tunable laser determines the wavelength of the laser's lasing. The transmission spectrum is determined by the sampling period of the grating. Therefore, by simulating the transmission spectrum, the lasing wavelength of the laser unit in actual chip manufacturing can be determined.

[0059] 2. Wavelength tuning range test:

[0060] Test method: Inject current into each channel laser in the 8*4 tunable laser array chip. When lighting up the 8 channels in the first row, light up a single channel and Y-combiner each time. When lighting up the channels in the second row and behind it, in addition to lighting up a single channel and Y-combining, it is also necessary to give a certain transparent current to the channel in front of it. The laser is coupled into the spectrometer, and the center wavelength of each laser is read from the spectrometer to obtain the laser's band. The current of each laser is gradually increased, and the center wavelength under each current is read from the spectrometer. The maximum and minimum values ​​of the center wavelength of each laser are subtracted to obtain the wavelength tuning range of the laser. The sum of the wavelength tuning ranges of all lasers (32) is the total wavelength tuning range.

[0061] The test results are as follows Figure 5As shown, the tunable wavelength range of the laser's 32 channels exceeds 128nm, the tuning range of each channel exceeds 4nm, and the side mode suppression ratio is greater than 40dB.

[0062] The above are only preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the scope of protection of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications without departing from the principle of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A broadband tunable light emitting chip based on asymmetric multi-quantum well technology, characterized in that: It includes a plurality of laser units distributed in columns, and each column of laser units includes a plurality of lasers connected in series; Several columns of laser units are combined by cascading Y-waveguides to achieve single waveguide laser output; The laser includes an asymmetric multi-quantum well layer.

2. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 1, characterized in that: The asymmetric multi-quantum well layer includes a plurality of compressively strained InGaAlAs quantum wells and a plurality of tensilely strained InGaAlAs quantum barriers, and the compressively strained InGaAlAs quantum wells and the tensilely strained InGaAlAs quantum barriers are distributed at intervals.

3. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 2, characterized in that: In the plurality of compressively strained InGaAlAs quantum wells, the photoluminescence wavelength of each compressively strained InGaAlAs quantum well gradually decreases from top to bottom.

4. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 3, characterized in that: In the plurality of compressively strained InGaAlAs quantum wells, the thickness and gallium / indium content of the material components of each compressively strained InGaAlAs quantum well decreases from top to bottom.

5. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 1, characterized in that: The laser further includes a grating layer; The grating layer is manufactured by adopting the reconstruction equivalent chirp technology, and a sampling grating with uniform period is manufactured through one holographic exposure and one holographic lithography.

6. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 5, characterized in that: The sampled grating is provided with a π phase shift, and the π phase shift is distributed at the center of the sampled grating.

7. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 2, characterized in that: The number of the compressively strained InGaAlAs quantum wells is 5, and the number of the tensilely strained InGaAlAs quantum barriers is 6.

8. The broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 1, characterized in that: The broadband tunable light emitting chip further includes a substrate, a buffer layer, a lower confinement layer, an upper confinement layer, a corrosion barrier layer, a waveguide layer, and a contact layer; the broadband tunable light emitting chip is stacked from bottom to top by a substrate, a buffer layer, a lower confinement layer, an asymmetric multi-quantum well layer, an upper confinement layer, a grating layer, a corrosion barrier layer, a waveguide layer, and a contact layer.

9. The method for preparing a broadband tunable light emitting chip based on asymmetric multi-quantum well technology according to claim 8, characterized in that: The following steps are involved: Step S1: growing a buffer layer, a lower confinement layer, an asymmetric multi-quantum well layer with a gradient thickness and a gallium / indium content, and an upper confinement layer in sequence on the upper surface of the substrate by metal organic compound vapor deposition; Step S2: fabricating a grating layer above the upper confinement layer by reconstructing an equivalent chirp technique, and depositing InP on the grating layer; Step S3: sequentially growing a corrosion barrier layer, a waveguide layer, and a contact layer on the deposited InP grating layer; Step S4: etching the waveguide layer and the contact layer to form a ridge shape, thereby forming electrical isolation between each laser to prevent crosstalk; Step S5: growing a p-side metal electrode in the ridge region above the contact layer, growing an n-side electrode at the bottom of the substrate, thinning and polishing the n-side electrode, and annealing the laser high-temperature alloy; Step S6: cleaving the chip to obtain the tunable light emitting chip device.

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