Wavelength-tunable narrow-linewidth external-cavity semiconductor laser and optical module

Abstract

The present invention provides a wavelength-tunable narrow-linewidth external-cavity semiconductor laser and an optical module. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser comprises a laser chip, a narrow-band filter, a semi-transparent reflector, and a collimating optical fiber that are sequentially arranged along an optical path; the narrow-band filter has a wide spectrum, and can select, from among original incident optical signals, optical signals having a wide wavelength range for transmission, thereby achieving a wide tuning range; additionally, by adjusting the angle of the narrow-band filter and the position thereof on the optical path, narrow-band light having a wavelength range comprising a central wavelength is obtained by screening; the semi-transparent reflector is provided with a transmission film and a reflection film, the reflection film reflects optical signals back to the laser chip to form a resonant cavity, and a narrow linewidth is achieved by means of a long resonant cavity; moreover, by adjusting the angle of the semi-transparent reflector, an optical signal of a specified wavelength is selected from the narrow-band light for lasing and emitted to the collimating optical fiber, thereby completing wavelength tuning on the basis of a narrow linewidth and a wide tuning range.

Description

A wavelength-tunable narrow-linewidth external cavity semiconductor laser and optical module

[0001] Cross-reference of related applications

[0002] This application claims priority to the following patent application:

[0003] (1) A Chinese patent application filed on June 19, 2024, with application number 202410790715.5 and title “A wavelength-tunable narrow linewidth external cavity semiconductor laser and optical module”. Technical Field

[0004] This invention relates to the field of optical communication technology, and in particular to a wavelength-tunable narrow-linewidth external cavity semiconductor laser and optical module. Background Technology

[0005] Narrow-linewidth lasers play a crucial role in scientific research such as fiber optic sensing, high-precision spectroscopy, and gravitational wave detection, driving the rapid development of aerospace technology and deep-sea applications, including hydrophones, distributed sensing, and inter-satellite optical communication systems. Laser linewidth compression technology has become a key issue in obtaining highly coherent light sources.

[0006] However, in the existing technology, although narrow linewidth external cavity semiconductor lasers can meet the requirement of a small linewidth, they result in a narrow wavelength tunable range for the laser itself; while lasers that can achieve wide wavelength tunability often have an excessively large linewidth.

[0007] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field.

[0008] Application content

[0009] The technical problem to be solved by this invention is how to enable an external cavity semiconductor laser to have a relatively narrower linewidth while achieving a wider range of wavelength tuning.

[0010] The present invention adopts the following technical solution:

[0011] In a first aspect, a wavelength-tunable narrow-linewidth external cavity semiconductor laser is provided, comprising: a laser chip 1, a narrowband filter 2, a semi-transparent mirror 3, and a collimating fiber 4 arranged sequentially along the optical path;

[0012] The laser chip 1 emits broadband light to the narrowband filter 2. By adjusting the position and angle of the narrowband filter 2 on the optical path, a light signal with a preset wavelength range is selected from the broadband light and transmitted as narrowband light to the semi-transparent mirror 3.

[0013] The semi-transparent mirror 3 is used to reflect a first preset proportion of narrowband light back to the laser chip 1 to form a resonant cavity; a second preset proportion of narrowband light is transmitted through the semi-transparent mirror 3 to the collimating fiber 4; by adjusting the angle of the semi-transparent mirror 3, a target wavelength is selected within the wavelength range of the narrowband light for lasing.

[0014] Preferably, the wavelength-tunable narrow-linewidth external cavity semiconductor laser further includes a substrate 5 and a cooler 6, wherein:

[0015] The laser chip 1, narrowband filter 2, semi-transparent mirror 3, and collimating fiber 4 are all disposed on one side of the substrate 5, and the cooler 6 is disposed on the other side of the substrate 5.

[0016] The cooler 6 is used to adjust the temperature of the laser chip 1. By adjusting the temperature of the laser chip 1, a specified wavelength is selected as the center wavelength within a preset positive and negative range of the target wavelength. The optical signal of the center wavelength is used for lasing.

[0017] Preferably, a transition heat sink 51 is further provided between the laser chip 1 and the substrate 5. The transition heat sink 51 is used to elevate the laser chip 1 to meet the vertical height requirements of the laser chip 1.

[0018] Preferably, a thermistor 7 is also provided on the transition heat sink 51, and the temperature of the laser chip 1 is obtained based on the thermistor 7.

[0019] Preferably, the end of the laser chip 1 facing away from the semi-transparent mirror 3 is coated with a reflective film. The reflective film is used to reflect the light signal from the semi-transparent mirror 3 toward the semi-transparent mirror 3, so that a resonant cavity is formed between the laser chip 1 and the semi-transparent mirror 3.

[0020] Preferably, the wavelength-tunable narrow-linewidth external cavity semiconductor laser further includes a collimating lens 8, wherein:

[0021] The collimating lens 8 is disposed along the optical path and is located between the laser chip 1 and the narrowband filter 2.

[0022] Preferably, the wavelength-tunable narrow-linewidth external cavity semiconductor laser further includes a beam splitter prism 9, wherein:

[0023] The beam splitter 9 is disposed on the optical path and located between the semi-transparent mirror 3 and the collimating fiber 4. The beam splitter 9 is used to split the narrowband light from the semi-transparent mirror 3 into a third preset ratio optical signal and a fourth preset ratio optical signal.

[0024] The optical signal of the third preset ratio is transmitted from the beam splitter 9 to the collimating optical fiber 4 along the optical path direction;

[0025] The optical signal of the fourth preset ratio is reflected by the beam splitter 9 in a direction outside the optical path.

[0026] Preferably, the wavelength-tunable narrow-linewidth external cavity semiconductor laser further includes a photodetector 10, wherein:

[0027] The photodetector 10 is disposed on the optical path of the optical signal of the fourth preset ratio. The photodetector 10 is used to receive the optical signal of the fourth preset ratio, thereby detecting the optical power of the narrowband light.

[0028] Preferably, the wavelength-tunable narrow-linewidth external cavity semiconductor laser further includes an optical isolator 11, wherein:

[0029] The optical isolator 11 is disposed on the optical path and located between the beam splitter prism 9 and the collimating fiber 4. The optical isolator 11 is used to isolate impurity light in the optical path.

[0030] In a second aspect, an optical module includes the aforementioned wavelength-tunable narrow-linewidth external cavity semiconductor laser.

[0031] This invention provides a wavelength-tunable narrow-linewidth external cavity semiconductor laser and optical module. The laser chip 1, narrowband filter 2, semi-transparent mirror 3, and collimating fiber 4 are sequentially arranged along the optical path. The narrowband filter 2 has a wide spectrum, enabling it to select a wider wavelength range of light signals for transmission from the originally incident light signal, thus achieving a wider tunable range. Simultaneously, by adjusting the angle and position of the narrowband filter 2 on the optical path, narrowband light containing a center wavelength range can be selected. The semi-transparent mirror 3 is equipped with a transmission film and a reflection film. The reflection film reflects the light signal back to the laser chip 1 to form a resonant cavity. A longer resonant cavity achieves a smaller linewidth. Furthermore, by adjusting the angle of the semi-transparent mirror 3, a specified wavelength of light signal is selected from the narrowband light and emitted to the collimating fiber 4, achieving wavelength tuning based on a relatively narrow linewidth and a relatively wide tunable range. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0033] Figure 1 is a schematic diagram of the structure of a wavelength-tunable narrow-linewidth external cavity semiconductor laser provided in an embodiment of the present invention;

[0034] Figure 2 shows the emission spectrum of a laser chip for another wavelength-tunable narrow-linewidth external cavity semiconductor laser provided in an embodiment of the present invention.

[0035] Figure 3 shows a single longitudinal mode output spectrum of the external cavity structure of a wavelength-tunable narrow linewidth external cavity semiconductor laser provided in an embodiment of the present invention.

[0036] Figure 4 is a schematic diagram of another wavelength-tunable narrow-linewidth external cavity semiconductor laser provided in an embodiment of the present invention.

[0037] Figure 5 is a schematic diagram of another wavelength-tunable narrow linewidth external cavity semiconductor laser provided in an embodiment of the present invention;

[0038] Figure 6 is a schematic diagram of another wavelength-tunable narrow-linewidth external cavity semiconductor laser provided in an embodiment of the present invention.

[0039] Figure 7 is a schematic diagram of another wavelength-tunable narrow linewidth external cavity semiconductor laser provided in an embodiment of the present invention;

[0040] Figure 8 is a schematic diagram of another wavelength-tunable narrow-linewidth external cavity semiconductor laser provided in an embodiment of the present invention.

[0041] Figure 9 is a schematic diagram of another wavelength-tunable narrow-linewidth external cavity semiconductor laser provided in an embodiment of the present invention;

[0042] The attached figures are numbered as follows: Laser chip 1; Narrowband filter 2; Semi-transparent mirror 3; Collimating fiber 4; Substrate 5; Transition heat sink 51; Cooler 6; Thermistor 7; Collimating lens 8; Beam splitter 9; Photodetector 10; Optical isolator 11. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0045] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0046] As used in this invention, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from a particular value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the particular quantity, i.e., the limitations of the measurement system.

[0047] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0048] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Example 1:

[0050] Embodiment 1 of the present invention provides a wavelength-tunable narrow-linewidth external cavity semiconductor laser, as shown in Figure 1, comprising: a laser chip 1, a narrowband filter 2, a semi-transparent mirror 3, and a collimating fiber 4 arranged sequentially along the optical path.

[0051] The laser chip 1 emits broadband light to the narrowband filter 2. By adjusting the position and angle of the narrowband filter 2 on the optical path, a light signal with a preset wavelength range is selected from the broadband light and transmitted as narrowband light to the semi-transparent mirror 3.

[0052] In this embodiment, the laser chip 1 can be a semiconductor gain chip used to emit broadband light. In this embodiment, the wavelength range of the broadband light can be 1530nm to 1565nm. The narrowband filter 2 is used to select the frequency of the broadband light, that is, to select the light signal of a preset wavelength range from all wavelength ranges of the broadband light for emission. The light signals of other wavelength ranges in the broadband light are filtered out by the narrowband filter 2 and cannot pass through the narrowband filter 2. The light signal that passes through the narrowband filter 2 is narrowband light.

[0053] In this embodiment, the preset wavelength range is set by those skilled in the art based on actual conditions. Specifically, the position of the narrowband filter 2 can be adjusted along the optical path direction to change the distance between the narrowband filter 2 and the laser chip 1. Simultaneously, the angle of the narrowband filter 2 relative to the optical path direction can be adjusted to adjust the preset wavelength range. In this embodiment, the bandwidth of the narrowband filter 2 can be 100G, which is larger than that of a 50G filter compared to commonly used filters, resulting in a wider tunable range. Compared to a 200G filter, although the tunable range of the narrowband filter 2 in this embodiment is smaller, a 200G filter would lead to an excessively large linewidth. Furthermore, the semi-transparent mirror 3 subsequently installed in this embodiment can form a resonant cavity with the laser chip 1, thereby reducing the bandwidth. Therefore, the 100G bandwidth narrowband filter 2 is relatively superior in this embodiment, achieving a larger tunable wavelength range while maintaining a relatively small linewidth. In this embodiment, using a 100G bandwidth narrowband filter 2 can achieve a linewidth within 3kHz.

[0054] The semi-transparent mirror 3 is used to reflect a first preset proportion of narrowband light back to the laser chip 1 to form a resonant cavity, and a second preset proportion of narrowband light is transmitted through the semi-transparent mirror 3 to the collimating fiber 4; by adjusting the angle of the semi-transparent mirror 3, a target wavelength is selected within the wavelength range of the narrowband light for lasing.

[0055] In this embodiment, the semi-transparent mirror 3 is coated with a certain proportion of reflective film, which allows the semi-transparent mirror 3 to transmit a second preset proportion of narrowband light while reflecting the first preset proportion of narrowband light back to the laser chip 1. The light signal reflected back to the laser chip 1 is reflected again by the laser chip 1 towards the semi-transparent mirror 3, thereby forming a resonant cavity between the laser chip 1 and the semi-transparent mirror 3. This cavity is used to amplify the light signal, and the resonant cavity makes the optical path of the amplified light signal longer, thereby achieving a smaller linewidth.

[0056] The optical signal transmitted from the semi-transparent mirror 3 to the collimating fiber 4 is an optical signal with a wavelength that meets the lasing conditions. The lasing conditions include: an optical signal with a wavelength closest to the peak wavelength of the combined spectrum of the narrowband filter 2 and the mirror, which can obtain the maximum gain to form a lasing. The semi-transparent mirror 3 and the collimating fiber 4 select the center wavelength for lasing and output within the corresponding wavelength range according to the above lasing conditions.

[0057] In this embodiment, the first preset ratio and the second preset ratio can be set by those skilled in the art, and both the first preset ratio and the second preset ratio can be 50%. The collimating fiber 4 may include a converging lens and a polarization-maintaining fiber. After the optical signal passes through the converging lens and the polarization-maintaining fiber, slow-axis light is output.

[0058] It is important to note that in this embodiment, to ensure the formation of a resonant cavity between the semi-transparent mirror 3 and the laser chip 1—that is, to allow the optical signal to undergo multiple back-and-forth reflections between the semi-transparent mirror 3 and the laser chip 1—a reflective film is coated on the end of the laser chip 1 facing away from the semi-transparent mirror 3. This reflective film reflects the optical signal from the semi-transparent mirror 3 back towards the semi-transparent mirror 3. A transmission film is coated on the end of the laser chip 1 facing the semi-transparent mirror 3, thereby ensuring that the optical signal reflected back from the laser chip 1 to the semi-transparent mirror 3 can pass through the front end of the laser chip 1 and exit, thus ensuring the formation of a resonant cavity between the laser chip 1 and the semi-transparent mirror 3. In this embodiment, the proportion of the reflective film on the end of the laser chip 1 facing away from the semi-transparent mirror 3 can be above 90%.

[0059] The process of lasing by adjusting the semi-transparent mirror 3 to select the corresponding wavelength of light signal is as follows: the broadband light emitted by the laser chip 1 is sent into the narrowband filter 2 to form a grid spectrum. The narrowband filter 2 selects the light signal with a preset wavelength range as the narrowband light to pass through the narrowband filter 2. The angle of the semi-transparent mirror 3 is adjusted to select light signals with different grid wavelengths from the preset wavelength range. The selected light signal is emitted back to the laser chip 1 to form a resonant cavity. The specific wavelength that meets the lasing conditions is transmitted from the semi-transparent mirror 3 as the center wavelength and is received by the collimating fiber 4.

[0060] Figure 2 shows the output spectrum of the laser chip, and Figure 3 shows the single longitudinal mode output spectrum of the external cavity structure. By comparing Figure 2 and Figure 3, it can be seen that one wavelength is selected from the wavelength range of the broadband light of the laser chip 1 as the center wavelength for lasing, thus achieving wavelength tuning.

[0061] In this embodiment, by replacing the grating filter in the existing tunable semiconductor laser with a narrowband filter 2 and the grating with a semi-transparent mirror 3, the narrowband filter 2, with its wider spectrum, can select a wider range of wavelengths for transmission from the original incident light signal, thereby achieving a wider tunable range. Simultaneously, by adjusting the angle and position of the narrowband filter 2 on the optical path, narrowband light containing the center wavelength is selected. The semi-transparent mirror 3 is provided with a certain proportion of reflective film, which reflects the light signal back to the laser chip 1 to form a resonant cavity. A smaller linewidth is achieved through the resonant cavity with a longer optical path. Furthermore, by adjusting the angle of the semi-transparent mirror 3, a specified wavelength of light signal is selected from the narrowband light for lasing, thus completing wavelength tuning based on a relatively narrow linewidth and a relatively wide tunable range.

[0062] In this embodiment, to further achieve wavelength tuning, the temperature of the laser chip 1 can also be adjusted, enabling external adjustment to achieve tuning of the center wavelength. Therefore, this embodiment also involves the following design:

[0063] As shown in Figure 4, the wavelength-tunable narrow-linewidth external cavity semiconductor laser also includes a substrate 5 and a cooler 6, wherein:

[0064] The laser chip 1, narrowband filter 2, semi-transparent mirror 3, and collimating fiber 4 are all disposed on one side of the substrate 5, and the cooler 6 is disposed on the other side of the substrate 5. The cooler 6 is used to adjust the temperature of the laser chip 1. By adjusting the temperature of the laser chip 1, a specified wavelength is selected as the center wavelength within a preset positive and negative range of the target wavelength. The optical signal of the center wavelength is used for lasing.

[0065] In this embodiment, the substrate 5 supports most of the components in the wavelength-tunable narrow-linewidth external cavity semiconductor laser. The substrate 5 can be a heat sink. The cooler 6 exchanges heat with the laser through the substrate 5, improving the heat exchange efficiency between the laser chip 1 and the cooler 6, thereby achieving temperature regulation of the laser chip 1. The temperature of the laser chip 1 affects the wavelength change of the emitted light signal. Therefore, the temperature of the laser chip 1 can be changed by adjusting the cooler 6, thereby achieving adjustment of the center wavelength. It is worth mentioning that in this embodiment, the target wavelength is selected within the narrow-band light wavelength range by adjusting the semi-transparent mirror 3. The cooler 6 then selects the corresponding wavelength as the center wavelength light signal for lasing within a range of ±60 pm of the target wavelength by adjusting the temperature of the laser chip 1, achieving complete wavelength tuning. Therefore, the preset positive and negative range in this embodiment can be ±60 pm.

[0066] It is worth mentioning that, in this embodiment, a housing is also provided around the substrate 5. The housing is used to encapsulate the device in the wavelength-tunable narrow linewidth external cavity semiconductor laser and isolate it from the outside world. Multiple leads are distributed on both sides of the housing for connecting to the positive and negative terminals of the laser chip 1 and the cooler 6, so as to realize the electrical connection between the laser chip 1 and the outside world and the electrical connection between the cooler 6 and the external temperature controller. The laser chip 1 is current-excited, and the temperature of the cooler 6 is adjusted to the specified wavelength operating point by the temperature controller to realize the tuning of the specified wavelength.

[0067] In this embodiment, the cooler 6 can be soldered to the bottom of the tube shell using reflow soldering, and the soldering position of the cooler 6 can be set at the center of the bottom of the tube shell. Then, the lower surface of the substrate 5 and the cooler 6 are soldered together to ensure uniformity and flatness of the soldering. The laser chip 1 can be soldered to one end of the upper surface of the substrate 5, with the light-emitting end of the laser chip 1 facing the light-emitting hole provided on the tube shell.

[0068] In this embodiment, considering that the laser chip 1 is relatively low, possibly only 0.1mm in vertical height, in order to ensure that the optical axis height of the laser chip 1 matches that of other devices, this embodiment also involves the following design:

[0069] As shown in Figure 5, a transition heat sink 51 is also provided between the laser chip 1 and the substrate 5. The transition heat sink 51 is used to raise the laser chip 1 to meet the vertical height of the laser chip 1.

[0070] In this embodiment, the transition heat sink 51 itself has excellent thermal conductivity, which avoids the increase in the gap between the laser chip 1 and the cooler 6 from affecting the heat transfer efficiency.

[0071] On the other hand, in order to more accurately control the temperature of the laser chip 1, it is also necessary to accurately detect the current temperature of the laser chip 1, and then adjust the cooler 6 according to the detection results. Therefore, this embodiment also involves the following design:

[0072] As shown in Figure 6, a thermistor 7 is also provided on the transition heat sink 51, and the temperature of the laser chip 1 is obtained based on the thermistor 7.

[0073] In this embodiment, given the close proximity between the thermistor 7 and the laser chip 1, the thermistor 7 can be disposed on the transition heat sink 51 or the substrate 5. The two poles of the thermistor 7 are connected to the lead wires of the casing, realizing electrical connection between the thermistor 7 and the outside. By measuring the temperature change of the thermistor 7, the current temperature of the laser chip 1 can be obtained in real time, thereby adjusting the cooler 6 in real time to maintain the laser chip 1 at the specified temperature and achieving accurate wavelength tuning.

[0074] In this embodiment, the bonding process of the laser chip 1 and the thermistor 7 is as follows: Under a microscope, the laser chip 1 and the thermistor 7 are placed in the solder area of ​​the transition heat sink 51 and gently pressed to ensure that the solder on the bottom of the laser chip 1 and the bottom of the thermistor 7 is uniform. Gold wire bonding can be used to connect the positive and negative electrodes of the laser chip 1 and the two electrodes of the thermistor 7 to the leads of the housing.

[0075] In this embodiment, since the optical signal emitted by laser chip 1 is divergent, in order to ensure the accuracy and feasibility of the optical path direction, this embodiment also involves the following design:

[0076] As shown in Figure 7, the wavelength-tunable narrow-linewidth external cavity semiconductor laser also includes a collimating lens 8, wherein:

[0077] The collimating lens 8 is disposed along the optical path and is located between the laser chip 1 and the narrowband filter 2.

[0078] In this embodiment, when the wavelength-tunable narrow-linewidth external cavity semiconductor laser is working normally, it is necessary to monitor the optical power of the optical signal in the optical path in real time. Existing detectors are usually set on one side of the laser chip 1 to directly detect the optical power of the optical signal of the laser chip 1. Although this method can achieve real-time monitoring of the laser chip 1, it cannot monitor the optical signal in the entire optical path. When other devices in the optical path fail, the detector on the laser chip 1 side cannot detect the corresponding fault information. Therefore, in order to monitor the optical signal of the laser chip 1 and the subsequent optical path simultaneously, this embodiment also involves the following design:

[0079] As shown in Figure 8, the wavelength-tunable narrow-linewidth external cavity semiconductor laser also includes a beam splitter prism 9, wherein:

[0080] The beam splitter 9 is disposed on the optical path and located between the semi-transparent mirror 3 and the collimating fiber 4. The beam splitter 9 is used to split the narrowband light from the semi-transparent mirror 3 into a third preset ratio optical signal and a fourth preset ratio optical signal. The third preset ratio optical signal is transmitted from the beam splitter 9 to the collimating fiber 4 along the optical path direction. The fourth preset ratio optical signal is reflected by the beam splitter 9 in a direction outside the optical path.

[0081] The wavelength-tunable narrow-linewidth external cavity semiconductor laser also includes a photodetector 10, wherein:

[0082] The photodetector 10 is disposed on the optical path of the optical signal of the fourth preset ratio. The photodetector 10 is used to receive the optical signal of the fourth preset ratio, thereby detecting the optical power of the narrowband light.

[0083] In this embodiment, the third preset ratio and the fourth preset ratio are set by those skilled in the art according to the actual situation. The transmittance of the beam splitter 9 can be set to 99%, and the remaining 1% of the light signal is reflected to the photodetector 10 for light power detection. Therefore, the third preset ratio can be 99%, and the fourth preset ratio can be 1%.

[0084] In this embodiment, a glass pad can be placed in the optical path of the fourth preset ratio optical signal on the substrate 5, and the photodetector 10 is placed on the side of the glass pad facing the beam splitter 9, so that the photosensitive surface of the photodetector 10 receives the reflected light from the beam splitter 9. In this embodiment, the positive and negative electrodes of the photodetector 10 can also be connected to the leads of the tube shell to realize electrical connection with the outside world.

[0085] In summary, in this embodiment, including the positive and negative terminals of the laser chip 1, the positive and negative terminals of the PD detector, the positive and negative terminals of the cooler 6, and the two stages of the thermistor 7, a total of at least 8 leads need to be defined on the casing for electrical connection with the corresponding devices.

[0086] In this embodiment, considering that discontinuities in the optical path will generate reflected light, which may adversely affect the laser chip 1 and the optical path system, this embodiment also involves the following design:

[0087] As shown in Figure 9, the wavelength-tunable narrow-linewidth external cavity semiconductor laser also includes an optical isolator 11, wherein:

[0088] The optical isolator 11 is disposed on the optical path and located between the beam splitter prism 9 and the collimating fiber 4. The optical isolator 11 is used to isolate impurity light in the optical path.

[0089] In summary, this embodiment achieves the following beneficial effects compared to the prior art:

[0090] 1. In this embodiment, a laser structure is formed by combining a narrowband filter 2 with a semi-transparent mirror 3 to ensure that the laser still has a stable single longitudinal mode output when using a long external cavity structure and a wide gain semiconductor chip. The center wavelength of the laser channel can be flexibly selected in the range of 1530nm to 1565nm. When the laser is working at the center wavelength, wavelength tuning of ±50pm can be achieved.

[0091] 2. The side-mode suppression ratio of the laser of the present invention can reach about 80dB, and the power can reach more than 20mW at a working current of 200mA. At the same time, the Lorentz linewidth of the laser channel is calculated to be below 3kHz through frequency noise spectrum.

[0092] Example 2:

[0093] Based on Example 1, and referring to Figures 4-9, this embodiment provides a packaging method for a wavelength-tunable narrow-linewidth external cavity semiconductor laser, as follows:

[0094] 1. The cooler 6 is welded to the bottom of the tube shell by reflow soldering. The welding position of the cooler 6 can be set at the center of the bottom of the tube shell.

[0095] 2. Weld the lower surface of the substrate 5 to the cooler 6 to ensure the uniformity and flatness of the weld.

[0096] 3. Solder the laser chip 1 to one end of the upper surface of the substrate 5, with the light-emitting end of the laser chip 1 facing the light-emitting hole provided on the tube shell; under a microscope, place the laser chip 1 and the thermistor 7 in the solder area of ​​the transition heat sink 51 and press gently to ensure that the bottom of the laser chip 1 and the bottom of the thermistor 7 are uniformly soldered.

[0097] 4. Using gold wire bonding, the positive and negative terminals of the laser chip 1 and the two terminals of the thermistor 7 are connected to the pins of the tube shell by gold wire bonding.

[0098] 5. Power on the laser chip 1 and simultaneously control the temperature of the cooler 6 to 25°C. At this time, the laser chip 1 emits broadband light, and the coupled collimating lens 8 collimates the beam. The output power at this time is about 10dBm.

[0099] 6. Place the narrowband filter 2 behind the collimating lens 8, and adjust the position and angle of the narrowband filter 2 to obtain the grating spectrum of the desired center wavelength. At this time, the optical loss does not exceed 0.5dBm.

[0100] 7. Attach the semi-transparent mirror 3 to the appropriate position behind the narrowband filter 2, and adjust the angle of the semi-transparent mirror 3 to emit the required center wavelength.

[0101] 8. Bond the beam splitter prism 9, the optical isolator 11 and the photodetector 10, and perform gold wire bonding on the photodetector 10 to ensure that the positive and negative terminals of the photodetector 10 are connected to the leads of the tube shell, so that the response current of the photodetector 10 changes linearly with the optical power.

[0102] 9. Weld the tail tube to collimate the optical fiber 4, while ensuring an extinction ratio greater than 20dB.

[0103] 10. The casing should be sealed to ensure airtightness.

[0104] Example 3:

[0105] This embodiment, based on Embodiment 1, provides an optical module including the wavelength-tunable narrow-linewidth external cavity semiconductor laser described in Embodiment 1. In practical use, other related components can be added according to the specific application scenario of the optical module. The specific structure of the wavelength-tunable narrow-linewidth external cavity semiconductor laser is detailed above and will not be repeated here.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wavelength tunable narrow linewidth external cavity semiconductor laser, characterized by, The wavelength tunable narrow line width external cavity semiconductor laser comprises: a laser chip (1), a narrow band filter (2), a half mirror (3) and a collimating optical fiber (4) arranged in sequence along an optical path; the laser chip (1) emits broadband light to the narrow band filter (2), by adjusting the position of the narrow band filter (2) on the optical path and the angle of the narrow band filter (2), the light signal of a preset wavelength range in the broadband light is selected as the narrow band light and transmitted to the half mirror (3); the half mirror (3) is used for reflecting a first preset proportion of the narrow band light back to the laser chip (1) to form a resonant cavity; a second preset proportion of the narrow band light transmits through the half mirror (3) to the collimating optical fiber (4); by adjusting the angle of the half mirror (3), a target wavelength is selected in the wavelength range of the narrow band light for lasing.

2. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The wavelength range of the broadband light is 1530nm to 1565nm.

3. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The light signal reflected back to the laser chip (1) is reflected by the laser chip (1) towards the half mirror (3), so that a resonant cavity is formed between the laser chip (1) and the half mirror (3) for amplifying the light signal, and the resonant cavity makes the optical path of the amplified light signal longer, thereby realizing a smaller line width.

4. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The collimating optical fiber (4) comprises a converging lens and a polarization maintaining optical fiber inside, and the light signal is outputted as slow axis light after passing through the converging lens and the polarization maintaining optical fiber.

5. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The end of the laser chip (1) facing away from the half mirror (3) is coated with a reflective film, which is used for reflecting the light signal from the half mirror (3) towards the half mirror (3), and the end of the laser chip (1) facing towards the half mirror (3) is coated with a transmission film, so that the light signal reflected from the laser chip (1) back to the half mirror (3) can be transmitted through the front end of the laser chip (1) and emitted, thereby ensuring that the laser chip (1) and the half mirror (3) form a resonant cavity; the proportion of the reflective film on the end of the laser chip (1) facing away from the half mirror (3) is more than 90%.

6. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The wavelength tunable narrow line width external cavity semiconductor laser further comprises a substrate (5) and a refrigerator (6), wherein: the laser chip (1), the narrow band filter (2), the half mirror (3) and the collimating optical fiber (4) are arranged on one side of the substrate (5), and the refrigerator (6) is arranged on the other side of the substrate (5); the refrigerator (6) is used for adjusting the temperature of the laser chip (1), by adjusting the temperature of the laser chip (1), a specified wavelength is selected as a center wavelength within a preset positive and negative interval range of the target wavelength, and the light signal of the center wavelength is used for lasing.

7. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 6, characterized in that, The preset positive and negative interval range is ±60pm.

8. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 6, characterized in that, The periphery of the substrate (5) is further provided with a tube shell for packaging the device in the wavelength tunable narrow linewidth external cavity semiconductor laser and isolating from the outside. A plurality of lead wires are arranged on both sides of the tube shell for connecting the positive and negative electrodes of the laser chip (1) and the positive and negative electrodes of the refrigerator (6) to realize the electrical connection between the laser chip (1) and the outside and the electrical connection between the refrigerator (6) and the temperature controller outside.

9. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 6, characterized in that, A transition heat sink (51) is further arranged between the laser chip (1) and the substrate (5), which is used to elevate the laser chip (1) to meet the vertical height of the laser chip (1).

10. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 9, wherein, A thermistor (7) is further arranged on the transition heat sink (51), and the temperature of the laser chip (1) is obtained according to the thermistor (7).

11. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The end of the laser chip (1) away from the semi-transparent mirror (3) is coated with a reflective film, which is used to reflect the light signal from the semi-transparent mirror (3) towards the semi-transparent mirror (3), so as to form a resonant cavity between the laser chip (1) and the semi-transparent mirror (3).

12. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The wavelength tunable narrow linewidth external cavity semiconductor laser further comprises a collimating lens (8), wherein: The collimating lens (8) is arranged along the optical path and located between the laser chip (1) and the narrow band filter (2).

13. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 1, characterized in that, The wavelength tunable narrow linewidth external cavity semiconductor laser further comprises a light splitting prism (9), wherein: The light splitting prism (9) is arranged on the optical path and located between the semi-transparent mirror (3) and the collimating optical fiber (4), and the light splitting prism (9) is used to split the narrow band light from the semi-transparent mirror (3) into a third preset proportion of light signal and a fourth preset proportion of light signal; The third preset proportion of light signal is transmitted from the light splitting prism (9) to the collimating optical fiber (4) along the direction of the optical path; The fourth preset proportion of light signal is reflected by the light splitting prism (9) towards the direction outside the optical path.

14. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 13, characterized in that, The transmittance of the light splitting prism (9) is 99%, and the remaining 1% of the light signal is reflected to the optical detector (10) for light power detection.

15. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 13, characterized in that, A glass gasket is arranged on the optical path of the fourth preset proportion of light signal on the substrate (5), and the optical detector (10) is arranged on the side of the glass gasket towards the light splitting prism (9) so that the light sensitive surface of the optical detector (10) receives the reflected light from the light splitting prism (9).

16. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 13, characterized in that, The wavelength tunable narrow linewidth external cavity semiconductor laser further comprises an optical detector (10), wherein: The optical detector (10) is arranged on the optical path of the fourth preset proportion of light signal, and the optical detector (10) is used to receive the fourth preset proportion of light signal to detect the light power of the narrow band light.

17. The wavelength-tunable narrow-linewidth external-cavity semiconductor laser according to claim 13, wherein, The wavelength tunable narrow linewidth external cavity semiconductor laser further comprises an optical isolator (11), wherein: The optical isolator (11) is arranged on the optical path and located between the light splitting prism (9) and the collimating optical fiber (4), and the optical isolator (11) is used to isolate the impurity light in the optical path.

18. An optical module characterized by comprising: The wavelength tunable narrow linewidth external cavity semiconductor laser comprising any one of claims 1-17.

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