Semiconductor laser and output wavelength real-time feedback method thereof

Abstract

The invention provides a semiconductor laser, which comprises a gain chip, a first laser beam is emitted from a first side surface of the gain chip along a first direction, and a second laser beam is emitted from a second side surface of the gain chip along a second direction; the external cavity laser main body is arranged opposite to the first side surface of the gain chip and is used for resonating, focusing and emitting the first laser beam; and the photodiode group is arranged relative to the second side surface of the gain chip, the photodiode group comprises a plurality of photodiodes, and the plurality of photodiodes are arranged in a fan shape relative to the second side surface and have dispersion difference. The invention also provides an output wavelength real-time feedback method applied to the semiconductor laser.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor lasers, and in particular relates to a semiconductor laser and a real-time feedback method for its output wavelength. Background Art

[0002] Semiconductor lasers are widely used in various fields such as optical communication, optical sensing, and optical detection due to their small size, easy integration, and electrical pumping. With the popularization of coherent optical systems and the gradual expansion of applications such as optical frequency stabilization, the demand for real-time acquisition of semiconductor laser output wavelengths is also growing.

[0003] At present, a variety of technical means can be used to measure the wavelength of light, such as grating spectrometry, interferometer interference, standard light beat frequency, etc. In order to ensure the measurement accuracy, these methods often require precise fixing and moving of the device position, as well as precise temperature control. In addition, its supporting components are difficult to integrate and generally appear in the form of independent instruments. There are also some small-volume solutions, such as using absorbers and filters with dispersion characteristics to determine the wavelength by comparing the ratio of light intensity before and after absorption. This type of solution can be integrated to a certain extent, but because it is independent of the laser itself, the measured detection light needs to be split from the output light for output, which brings additional loss to the output of the laser, reduces the output power and photoelectric efficiency, and also increases the complexity of the optical system.

[0004] Therefore, a laser that does not introduce additional losses, does not significantly increase the complexity of the optical system, and integrates wavelength measurement function in the package will provide more possibilities for the application of semiconductor lasers. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a semiconductor laser and a real-time feedback method for its output wavelength, so as to solve the problems of lossless acquisition of optical signals, wavelength measurement and integration of measurement devices.

[0006] On one hand, the present invention provides a semiconductor laser, comprising: a gain chip, wherein the first side surface of the gain chip emits a first laser beam along a first direction, and the second side surface of the gain chip emits a second laser beam along a second direction; an external cavity laser body, arranged relative to the first side surface of the gain chip, and used for resonating, focusing and emitting the first laser beam; a photodiode group, arranged relative to the second side surface of the gain chip, the photodiode group comprising a plurality of photodiodes, the plurality of photodiodes being arranged in a fan shape relative to the second side surface, and having dispersion differences.

[0007] In some embodiments of the present invention, one side of the plurality of photodiodes opposite to the second side surface of the gain chip is a light-collecting surface for collecting the second laser beam; the light-collecting surfaces of the plurality of photodiodes are coated with anti-reflection films with different transmittances.

[0008] In some embodiments of the present invention, a photodiode having the highest transmittance of an antireflection film on its light-collecting surface is selected as a reference photodiode, and the transmittance of the antireflection film plated on the light-collecting surface of the reference photodiode is greater than 95%.

[0009] In some embodiments of the present invention, the second laser beam has the same wavelength as the first laser beam.

[0010] In some embodiments of the present invention, the angle between the first direction and the second direction is an obtuse angle or a straight angle.

[0011] In some embodiments of the present invention, the semiconductor laser further comprises: a thermoelectric cooler, which is coated outside the gain chip, the external cavity laser body and the photodiode group and is used to adjust the temperature of the semiconductor laser.

[0012] On the other hand, the present invention provides a real-time feedback method for the output wavelength of a semiconductor laser. The photodiode group is composed of n photodiodes, where n is an integer greater than or equal to 2. The real-time feedback method for the output wavelength includes the following steps: obtaining n induced currents from the n photodiodes; converting the n induced currents into n voltages to obtain log values ​​of the n voltages; selecting the log value of the reference photodiode as a reference value, and calculating the difference between the remaining n-1 log values ​​and the reference value respectively; and querying a difference-wavelength comparison table according to the n-1 differences to obtain the wavelength of the second laser beam.

[0013] In some embodiments of the present invention, an analog quantity acquisition module is integrated on the driving circuit of the semiconductor laser; obtaining the n induced currents in the n photodiodes specifically includes: obtaining the n induced currents in the n photodiodes through the analog quantity acquisition module.

[0014] In some embodiments of the present invention, querying a difference-wavelength comparison table based on n-1 differences specifically includes the following steps: obtaining the wavelength of the first laser beam; adjusting the wavelength of the first laser beam, and calculating the difference between n-1 log values ​​and the reference value at different wavelengths of the adjusted first laser beam; and establishing a difference-wavelength comparison table between the difference and the wavelength of the first laser beam.

[0015] The semiconductor laser and the real-time feedback method of the output wavelength provided by the present invention enable the semiconductor laser to have the function of real-time feedback of the output wavelength without increasing the volume and integration complexity, and have the following advantages:

[0016] (1) Taking advantage of the divergence of the laser backlight angle, a multi-backlight detector is used to achieve real-time detection of the cavity mode wavelength and intensity without affecting the forward output light;

[0017] (2) By subtracting the log values ​​of photodiodes with different coatings, the measurement wavelength deviation caused by light intensity changes is eliminated;

[0018] (3) Using the anti-reflection film on the light-collecting surface of the photodiode as the dispersion medium not only saves space but also facilitates integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The structure of a semiconductor laser according to an embodiment of the present invention is schematically shown;

[0020] Figure 2 A partial structural diagram of a semiconductor laser according to a first embodiment is schematically shown;

[0021] Figure 3 A partial structural diagram of a semiconductor laser according to a second embodiment is schematically shown;

[0022] Figure 4 Schematically showing a transmittance ratio dispersion curve diagram of a photodiode group according to two embodiments;

[0023] Figure 5 A flow chart of a method for real-time feedback of output wavelength according to an embodiment of the present invention is schematically shown;

[0024] Figure 6 The working principle diagram of the driving circuit according to the embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0026] Figure 1 The structure of a semiconductor laser according to an embodiment of the present invention is schematically shown.

[0027] like Figure 1 As shown, in this embodiment, a semiconductor laser includes a gain chip 1, an external cavity laser body 2, a plurality of photodiodes 3 and a thermoelectric cooler 4. The first side surface of the gain chip 1 emits a first laser beam along a first direction, and the second side surface of the gain chip 1 emits a second laser beam along a second direction.

[0028] In this embodiment, the first side surface of the gain chip 1 can be a forward light emitting surface, the first direction can be a forward light emitting direction, and the first laser beam can be a forward light. In this embodiment, the second side surface of the gain chip 1 can be a back light emitting surface, the second direction can be a back light emitting direction, and the second laser beam can be a back light. The angle between the first direction and the second direction is an obtuse angle or a straight angle, and the specific angle is determined by the angle between the first laser beam and the second laser beam of the gain chip 1, in order not to interfere with the first laser beam when measuring the second laser beam. Since the first laser beam and the second laser beam are emitted by the gain chip 1 at the same time, the first laser beam and the second laser beam have the same wavelength, so the wavelength of the first laser beam can be obtained by measuring the wavelength of the second laser beam, and at the same time, no interference is caused to the first laser beam.

[0029] The external cavity laser body 2, in this embodiment, is arranged relative to the first side surface of the gain chip 1, and is used to resonate, focus and emit the first laser beam. For example, the external cavity laser body 2 can be composed of an FP filter, a grating, an isolator, a focusing lens and an outcoupling optical fiber. There are various external cavity lasers available on the market, and the present invention does not limit the structure and model of the external cavity laser used.

[0030] The photodiode group 3, in this embodiment, is arranged relative to the second side surface of the gain chip 1, and the photodiode group 3 includes a plurality of photodiodes PD, and the plurality of photodiodes PD are arranged in a fan shape relative to the second side surface, and the plurality of different photodiodes PD have differentiated detection efficiencies for light of the same wavelength, and have dispersion differences. The side of the plurality of photodiodes PD relative to the second side surface of the gain chip is a light-collecting surface for collecting the second laser beam. To ensure that each photodiode PD can completely and accurately collect the second laser beam, when arranging the positions of the plurality of photodiodes PD, the light-collecting surface of each photodiode PD cannot be blocked.

[0031] In some embodiments, the light-collecting surfaces of multiple photodiodes PD are coated with anti-reflection films with different transmittances, so that the dispersion differences of the photodiodes PD can be achieved. By utilizing the characteristics of the laser backlight angle divergence, the backlight is collected through the anti-reflection film without blocking another photodiode PD. The induced current generated can be converted into a corresponding voltage in the driving circuit and detected by a high-precision analog-to-digital converter.

[0032] In order to calculate the difference in laser beams collected by different photodiodes PD, a specific photodiode needs to be selected as a reference photodiode. In this embodiment, a photodiode PD with the highest transmittance of the anti-reflection film on the light-collecting surface is selected as the reference photodiode PD_ref, and the second laser beams collected by the remaining photodiodes PD are compared with the reference photodiode PD_ref to make log differences. At the same time, the wavelength band that the reference photodiode PD_ref needs to detect is located at the high transmittance center of its transmittance dispersion curve, and the transmittance of the anti-reflection film coated on its light-collecting surface is greater than 95%.

[0033] Please continue reading Figure 1 In this embodiment, the semiconductor laser further includes a thermoelectric cooler 4. The thermoelectric cooler 4 is coated outside the gain chip 1, the external cavity laser body 2 and the photodiode group 3, and is used to adjust the temperature of the semiconductor laser. On the one hand, it ensures the constant temperature of the laser external cavity, and on the other hand, it can also perform wavelength tuning by adjusting the temperature.

[0034] A semiconductor laser provided by the present invention is described above. To make the device provided by the present invention more clearly understood, two different numbers of photodiodes PD are used for illustration below.

[0035] First embodiment

[0036] The photodiode group 3 is composed of n photodiodes PD, where n is an integer greater than or equal to 2. When n is set to 2, the photodiode group 3 is composed of 2 photodiodes PD. Figure 2 A partial structural diagram of a semiconductor laser according to a first embodiment is schematically shown.

[0037] like Figure 2 As shown, in this embodiment, the two photodiodes PD are PD1 and PD2, which are arranged in a fan shape, with no shielding between them, and their light-collecting surfaces can collect the second laser beam of the gain chip 1. PD1 is selected as the reference photodiode PD_ref.

[0038] Second embodiment

[0039] Assume that n is 3, that is, the photodiode group 3 consists of 3 photodiodes PD. Figure 3 A partial structural diagram of a semiconductor laser according to a second embodiment is schematically shown.

[0040] like Figure 3 As shown, in this embodiment, the three photodiodes PD are PD1, PD2 and PD3, arranged in a fan shape, with no shielding between them, and their light-collecting surfaces can collect the second laser beam of the gain chip 1. PD1 is selected as the reference photodiode PD_ref.

[0041] Figure 4 The transmittance ratio dispersion curve diagrams of the photodiode groups according to two embodiments are schematically shown.

[0042] like Figure 4 As shown in Figure 1, it is assumed that the proportional resolution of the PD detection value determined by the sampling accuracy is 0.01. When the ratio of the detection value of PD2 / PD1 detected by two PDs is 0.96, as shown in Figure 1 Figure 4 As shown in (a), the detection value ratio range is 0.955-0.965, the corresponding wavelength range is 1545.6-1549.4nm, and the wavelength measurement error is ~4nm. After adding the detection value of PD3, when the detection value ratio of PD3 / PD1 is 0.94, as shown in Figure 4 As shown in (b), the detection value ratio interval is 0.935~0.945, the corresponding wavelength range is 1546.1~1546.5nm, and the wavelength measurement error is ~0.4nm.

[0043] It can be seen that by reasonably selecting the number and dispersion strength of the photodiodes in the photodiode group 3, not only the output wavelength can be fed back in real time, but also the wavelength feedback accuracy can be improved.

[0044] In order to realize the real-time feedback of the output wavelength of the semiconductor laser device, the present invention provides a method for real-time feedback of the output wavelength. Figure 5 The flowchart of the real-time feedback method of output wavelength according to an embodiment of the present invention is schematically shown.

[0045] like Figure 5 As shown, in this embodiment, the photodiode group 3 is composed of n photodiodes PD, where n is an integer greater than or equal to 2. The output wavelength real-time feedback method comprises the following steps:

[0046] S1, obtaining n induced currents in n photodiodes PD.

[0047] In some embodiments of the present invention, an analog quantity acquisition module is integrated on the driving circuit of the semiconductor laser, and the n induced currents in the n photodiodes PD are acquired through the analog quantity acquisition module.

[0048] S2, converts the n induced currents into n voltages to obtain the log values ​​of the n voltages.

[0049] S3, selecting the log value of the reference photodiode PD_ref as the reference value log_ref, and calculating the differences between the remaining n-1 log values ​​and the reference value log_ref respectively.

[0050] In S3, the influence of optical power fluctuation on wavelength measurement can be eliminated by taking log value differences, and the results of log value differences correspond to different optical wavelengths.

[0051] S4, querying a difference-wavelength comparison table according to the n-1 differences to obtain the wavelength of the second laser beam.

[0052] In this embodiment, the difference-wavelength comparison table in S5 is obtained by pre-calibration based on the wavelength data of the first laser beam. The specific steps include:

[0053] First, the wavelength of the first laser beam is obtained; then, the wavelength of the first laser beam is adjusted, and the difference between n-1 log values ​​and a reference value (log_ref) at different wavelengths of the adjusted first laser beam is calculated; finally, a difference-wavelength comparison table between the difference and the wavelength of the first laser beam is established.

[0054] Through steps S1 to S4, real-time feedback of the output wavelength can be achieved. In addition, the process can be automated by programming to quickly and accurately feedback the output wavelength.

[0055] Figure 6 The working principle diagram of the driving circuit according to the embodiment of the present invention is schematically shown.

[0056] Alternatively, if Figure 6 As shown, in the driving circuit, a constant current source module, a PID temperature control module, an analog quantity acquisition module and a serial communication module are integrated, and these modules can be controlled by an embedded single-chip microcomputer. Among them, the constant current source module is used to power the gain chip 1, the PID temperature control module is used to control the temperature and power the thermoelectric cooler 4, the analog quantity acquisition module monitors the photoelectric signal of the photodiode group 3, and the serial communication module receives instructions and reports the status of information such as wavelength. It should be noted that the driving circuit provided in this embodiment is only a schematic, and different driving circuits can be used for different semiconductor lasers, and ordinary technicians in this field can simply change or replace it.

[0057] In summary, through the embodiments of the present invention, a semiconductor laser and a method for real-time feedback of its output wavelength are provided, in which the backlight of the gain chip is collected by multiple photodiode groups, and the wavelength and intensity of the resonant light in the cavity are obtained without affecting the forward output light signal, so that the light signal can be acquired losslessly. At the same time, different anti-reflection films are plated on the light-collecting surfaces of multiple photodiodes, and the output wavelength can be fed back in real time by comparing the intensity measured with the reference photodiode, and feedback automation can be realized through programming. In addition, by using a photodiode group in an integrated package, the photodiode group is integrated and packaged with other components of the laser, which is small in size and easy to integrate.

[0058] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the claims, any reference symbol between brackets shall not be construed as a limitation to the claims.

[0059] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0060] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present disclosure, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0061] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A semiconductor laser, It is characterized in that include: A gain chip (1), wherein a first side surface of the gain chip (1) emits a first laser beam along a first direction, and a second side surface of the gain chip (1) emits a second laser beam along a second direction; An external cavity laser body (2), arranged relative to the first side surface of the gain chip (1), and used for resonating, focusing and emitting the first laser beam; A photodiode group (3) is arranged relative to the second side surface of the gain chip (1), and the photodiode group (3) includes a plurality of photodiodes (PDs). The plurality of photodiodes (PDs) are arranged in a fan shape relative to the second side surface and have dispersion differences.

2. The semiconductor laser according to claim 1, It is characterized in that A side of the plurality of photodiodes (PD) opposite to the second side surface of the gain chip (1) is a light collecting surface for collecting the second laser beam; The light-collecting surfaces of the plurality of photodiodes (PD) are coated with anti-reflection films with different transmittances.

3. The semiconductor laser according to claim 2, It is characterized in that A photodiode (PD) with the highest transmittance of the anti-reflection film on the light-collecting surface is selected as a reference photodiode (PD ref), and the transmittance of the anti-reflection film plated on the light-collecting surface of the reference photodiode (PDref) is greater than 95%.

4. The semiconductor laser according to claim 1, It is characterized in that The second laser beam has the same wavelength as the first laser beam.

5. The semiconductor laser according to claim 1, It is characterized in that The angle between the first direction and the second direction is an obtuse angle or a straight angle.

6. The semiconductor laser according to claim 1, It is characterized in that The semiconductor laser further comprises: A thermoelectric cooler (4) is coated outside the gain chip (1), the external cavity laser body (2) and the photodiode group (3) and is used to adjust the temperature of the semiconductor laser.

7. A method for real-time feedback of output wavelength of a semiconductor laser according to any one of claims 1 to 6, It is characterized in that The photodiode group (3) is composed of n photodiodes (PD), where n is an integer greater than or equal to 2. The method comprises the following steps: Obtaining n induced currents in the n photodiodes (PDs); Converting the n induced currents into n voltages to obtain log values ​​of the n voltages; Selecting the log value of the reference photodiode (PD_ref) as the reference value (log_ref), and calculating the differences between the remaining n-1 log values ​​and the reference value (log_ref); The difference-wavelength comparison table is queried according to the n-1 differences to obtain the wavelength of the second laser beam.

8. The method for real-time feedback of output wavelength according to claim 7, It is characterized in that An analog quantity acquisition module is integrated on the driving circuit of the semiconductor laser; The obtaining of n induced currents in the n photodiodes (PDs) specifically includes: The n induced currents in the n photodiodes are acquired through the analog quantity acquisition module.

9. The method for real-time feedback of output wavelength according to claim 7, It is characterized in that The querying of the difference-wavelength comparison table according to the n-1 differences specifically includes the following steps: acquiring the wavelength of the first laser beam; Adjusting the wavelength of the first laser beam, and calculating the difference between the n-1 log values ​​and the reference value (log_ref) at different wavelengths of the first laser beam after adjustment; A difference-wavelength comparison table between the difference and the wavelength of the first laser beam is established.

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