Tunable laser, photoelectric conversion module and communication system

Abstract

A tunable laser (211), a photoelectric conversion module (112) and a communication system (101), which are used for suppressing the concentration of photon-generated carriers in the tunable laser (211), so as to effectively suppress phase noise. The tunable laser (211) comprises a gain module (301), a first waveguide module (302), a gain electrode (314), a first waveguide electrode (324) and a first heating element (325). The gain electrode (314) applies a current to the gain module (301), the gain module (301) emits an optical signal on the basis of the current, the first heating element (325) applies first heat to the first waveguide module (302), and the first waveguide module (302) tunes the wavelength of the optical signal under the action of the first heat, such that the tunable laser (211) emits an optical signal which is tuned by means of the first waveguide module (302). The first waveguide electrode (324) applies a first reverse bias voltage to a first PN junction, wherein the first reverse bias voltage is used for making the first PN junction be in a reverse cut-off state.

Description

Tunable laser, photoelectric conversion module and communication system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on September 26, 2023, with application number 202311271559.3 and invention name “A tunable laser, photoelectric conversion module and communication system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of optical communications, and in particular to a tunable laser, a photoelectric conversion module, and a communication system. Background Art

[0003] In the field of optical communications, a tunable laser (TL) refers to a laser whose output wavelength can be tuned within a certain range. Tunable lasers are primarily used in high-capacity wavelength division multiplexing transmission systems.

[0004] A distributed Bragg reflector (DBR) laser includes an optical resonant cavity. The DBR laser heats the optical resonant cavity through thermal tuning to change the refractive index of the optical resonant cavity, thereby tuning the wavelength of the optical signal emitted by the DBR laser.

[0005] However, thermal tuning of the DBR laser will generate unstable photogenerated carriers, which will increase the phase noise of the DBR laser.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a tunable laser, a photoelectric conversion module, and a communication system for suppressing the concentration of photogenerated carriers in the tunable laser to effectively suppress phase noise.

[0008] In a first aspect, an embodiment of the present application provides a tunable laser, comprising a gain module, a first waveguide module, a gain electrode, a first waveguide electrode, and a first heating element, wherein the gain module is connected to the gain electrode, and the first waveguide electrode and the first heating element are respectively connected to the first waveguide module, and the first waveguide module comprises a first PN junction; the gain electrode is used to apply a current to the gain module, and the gain module is used to emit a light signal according to the current; the first heating element is used to apply a first heat to the first waveguide module, and the first waveguide module is used to tune the wavelength of the light signal under the action of the first heat, so that the tunable laser emits the light signal tuned by the first waveguide module; the first waveguide electrode is used to apply a first reverse bias voltage to the first PN junction, and the first reverse bias voltage is used to put the first PN junction in a reverse cutoff state, and the first PN junction in the reverse cutoff state can allow the first photogenerated carriers generated by the first PN junction to flow out of the first waveguide module.

[0009] As shown in this aspect, the first PN junction in the reverse cutoff state can make the first photogenerated carriers generated by the first PN junction flow out of the first waveguide module, so as to reduce the concentration of the first photogenerated carriers in the first waveguide module, thereby effectively reducing the probability of random recombination of the first photogenerated carriers in the first waveguide module, achieving the purpose of suppressing the random recombination of the first photogenerated carriers in the first waveguide module, and further effectively suppressing the phase noise of the first waveguide module.

[0010] Based on the first aspect, in an optional implementation, the tunable laser further includes a second waveguide module, the first waveguide module and the second waveguide module form an optical resonant cavity for tuning the wavelength of the optical signal, and the gain module is located in the optical resonant cavity.

[0011] By adopting this implementation, the optical resonant cavity of the tunable laser can tune the wavelength while effectively suppressing the concentration of photogenerated carriers generated by the optical resonant cavity, thereby effectively suppressing the phase noise of the optical resonant cavity.

[0012] Based on the first aspect, in an optional implementation, the tunable laser further includes a second heating element, which is connected to the second waveguide module; the second heating element is used to apply a second heat to the second waveguide module, and the second waveguide module is used to tune the wavelength of the optical signal under the action of the second heat.

[0013] With this implementation, the second heating element can change the refractive index of the second waveguide module, thereby achieving the purpose of wavelength tuning of the second waveguide module.

[0014] Based on the first aspect, in an optional implementation, the tunable laser further includes a second waveguide electrode, the second waveguide electrode is connected to the second waveguide module, and the second waveguide module includes a second PN junction; the second waveguide electrode is used to apply a second reverse bias voltage to the second PN junction, and the second reverse bias voltage is used to put the second PN junction into a reverse cutoff state, and the second PN junction in the reverse cutoff state is used to allow second photogenerated carriers generated by the second PN junction to flow out of the second waveguide module.

[0015] By adopting this implementation method, the second PN junction in the reverse cutoff state can cause the second photogenerated carriers generated by the second PN junction to flow out of the second waveguide module, thereby reducing the concentration of the second photogenerated carriers in the second waveguide module, thereby effectively reducing the probability of random recombination of the second photogenerated carriers in the second waveguide module, achieving the purpose of suppressing the random recombination of the second photogenerated carriers in the second waveguide module, and further effectively suppressing the phase noise of the second waveguide module.

[0016] Based on the first aspect, in an optional implementation, the tunable laser further includes a third waveguide module and a third heating element, the third heating element being connected to the third waveguide module, and the third waveguide module being located within the optical resonant cavity; the third heating element being configured to apply a third heat to the third waveguide module, and the third waveguide module being configured to tune the wavelength of the optical signal under the action of the third heat.

[0017] By adopting this implementation, the wavelength is precisely tuned through the third waveguide module located in the optical resonant cavity.

[0018] Based on the first aspect, in an optional implementation, the tunable laser further includes a third waveguide electrode, the third waveguide electrode is connected to the third waveguide module, and the third waveguide module includes a third PN junction; the third waveguide electrode is used to apply a third reverse bias voltage to the third PN junction, and the third reverse bias voltage is used to put the third PN junction into a reverse cutoff state, and the third PN junction in the reverse cutoff state is used to allow third photogenerated carriers generated by the third PN junction to flow out of the third waveguide module.

[0019] By adopting this implementation method, the third PN junction in the reverse cutoff state can cause the third photogenerated carriers generated by the third PN junction to flow out of the third waveguide module, effectively reducing the concentration of the third photogenerated carriers in the third waveguide module, thereby effectively reducing the probability of random recombination of the third photogenerated carriers in the third waveguide module, achieving the purpose of suppressing the random recombination of the third photogenerated carriers in the third waveguide module, and effectively suppressing the phase noise of the third waveguide module.

[0020] Based on the first aspect, in an optional implementation, the tunable laser includes a fourth waveguide module and a fifth waveguide module, the fourth waveguide module and the fifth waveguide module form an optical resonant cavity for tuning the wavelength of the optical signal, and the gain module and the first waveguide module are located in the optical resonant cavity.

[0021] By adopting this implementation, the wavelength can be precisely tuned by the first waveguide module located in the optical resonant cavity, and phase noise can also be effectively suppressed.

[0022] Based on the first aspect, in an optional implementation, the first PN junction is located inside the first waveguide module, or the first PN junction is located on a surface of the first waveguide module.

[0023] With this implementation, regardless of whether the first PN junction is located inside the first waveguide module or on the surface of the first waveguide module, the concentration of the first photogenerated carriers in the first PN junction can be effectively suppressed, thereby effectively suppressing the phase noise of the tunable laser.

[0024] Based on the first aspect, in an optional implementation, a rate of the first photogenerated carriers flowing out of the first waveguide module is positively correlated with a magnitude of the first reverse bias voltage.

[0025] By adopting this implementation, the rate at which the first photogenerated carriers flow out of the first waveguide module can be adjusted by adjusting the magnitude of the first reverse bias voltage, thereby ensuring that the first photogenerated carriers can flow out of the tunable laser in a timely manner and effectively suppressing phase noise.

[0026] Based on the first aspect, in an optional implementation, the first waveguide electrode is located between the first waveguide module and the first heating element, or the first heating element is located between the first waveguide electrode and the first waveguide module, and the first heating element has a through-hole, and the first waveguide electrode is connected to the first waveguide module through the through-hole.

[0027] This implementation ensures that the first heating element can apply the first heat to the first waveguide module to tune the wavelength of the optical signal, and ensures that the first waveguide electrode can apply the first reverse bias voltage to the first waveguide module to effectively suppress phase noise.

[0028] In a second aspect, an embodiment of the present application provides an optoelectronic conversion module, comprising a modulator, an output optical fiber, and a tunable laser as described in any one of the first aspects above, wherein the modulator is connected to the tunable laser and the output optical fiber, respectively; the modulator is configured to receive a first service electrical signal and the tuned optical signal from the tunable laser; the modulator is further configured to modulate the first service electrical signal onto the tuned optical signal to obtain a first service optical signal, and emit the first service optical signal through the output optical fiber. For a description of the tunable laser and its beneficial effects in this aspect, please refer to the first aspect and will not be elaborated on in detail.

[0029] In a third aspect, an embodiment of the present application provides an optoelectronic conversion module, comprising a demodulator, an input optical fiber, and a tunable laser as described in any one of the first aspects above, wherein the demodulator is connected to the tunable laser and the input optical fiber, respectively; the demodulator is configured to receive a second service optical signal from the input optical fiber and receive the tuned optical signal from the tunable laser; the demodulator is further configured to coherently demodulate the second service optical signal based on the tuned optical signal to obtain a second service electrical signal. For a description of the tunable laser and its beneficial effects in this aspect, please refer to the first aspect and will not be elaborated on in detail.

[0030] In a fourth aspect, an embodiment of the present application provides a communication system, comprising a device and an optoelectronic conversion module as described in the second aspect above, wherein the device comprises a processing chip and a connector, wherein the processing chip is connected to the optoelectronic conversion module via the connector, and the processing chip is used to send the first service electrical signal to the optoelectronic conversion module.

[0031] In the fifth aspect, an embodiment of the present application provides a communication system, comprising a device and an optoelectronic conversion module as described in the third aspect above, the device comprising a processing chip and a connector, the processing chip being connected to the optoelectronic conversion module via the connector, and the processing chip being used to receive the second service electrical signal sent from the optoelectronic conversion module.

[0032] In the sixth aspect, an embodiment of the present application provides an optical network, including a first communication system and a second communication system. For the description of the first communication system and the second communication system, please refer to the fourth and fifth aspects, and the details will not be repeated. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a structural diagram of an optical network provided by the present application;

[0034] FIG2a is a structural example diagram of a first communication system provided by the present application;

[0035] FIG2b is a structural example diagram of a second communication system provided by the present application;

[0036] FIG3 is a structural diagram of a first embodiment of a tunable laser provided in the present application;

[0037] FIG4 is a side view of the structure of the first embodiment of the tunable laser shown in FIG3;

[0038] FIG5 is a comparative example diagram of phase noise curves of the tunable laser provided by the present application and the existing DBR laser;

[0039] FIG6 a is a structural diagram illustrating a second embodiment of a tunable laser provided in the present application;

[0040] FIG6 b is a side view of an exemplary structure of an embodiment of the tunable laser shown in FIG6 a ;

[0041] FIG7 is a side view of a second embodiment of the tunable laser shown in FIG3;

[0042] FIG8 is a structural diagram of a second embodiment of a tunable laser provided in this application;

[0043] FIG9 is a cross-sectional structural example diagram of the tunable laser shown in FIG8 ;

[0044] FIG10 is a structural diagram of a third embodiment of a tunable laser provided in this application;

[0045] FIG11 is a structural diagram of a fourth embodiment of a tunable laser provided by the present application;

[0046] FIG12 is a structural diagram of a fifth embodiment of a tunable laser provided in the present application;

[0047] FIG13 is a structural diagram illustrating a sixth embodiment of a tunable laser provided in this application. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0049] Figure 1 is a structural example diagram of an optical network provided in this application. The optical network 100 includes a first communication system 101 and a second communication system 102, and the first communication system 101 and the second communication system 102 are connected by optical fiber. This example does not limit the number of communication systems included in the optical network 100. For example, the first communication system 101 can be connected to multiple second communication systems 102 through an optical splitter. This example does not limit the networking type of the optical network. For example, the optical network can adopt a ring network or a star network. This example does not limit the network type applied by the optical network 100. For example, if the optical network 100 shown in this example is applied to a passive optical network (PON), then one of the communication systems in the first communication system 101 and the second communication system 102 can be an optical network unit (ONU) or an optical network terminal (ONT), and the other communication system in the first communication system 101 and the second communication system 102 can be an optical line terminal (OLT). If the optical network 100 is applied to an optical transport network (OTN), both the first communication system 101 and the second communication system 102 can be OTN devices. The optical network 100 shown in this example can also be applied to a data center network (DCN) or a metropolitan area network, etc., without specific limitations. Taking the first communication system 101 as an example, this example does not limit the device type of the first communication system 101. For example, the first communication system 101 can be an optical transmission device, an optical access device, a router, a switch, a wireless base station, a wireless remote access device, a wireless baseband signal processing device, etc. It can also be a computing server (often referred to as a server), a high-performance computer (HPC), a storage server, or a memory resource pool. This example does not limit the type of the first communication system 101, as long as the first communication system 101 has electrical-to-optical conversion capabilities and an optical interface capable of connecting to an optical fiber. For a description of the type of the second communication system 102, please refer to the description of the first communication system 101, and the details are not repeated here.

[0050] Figure 2a is a structural example diagram of the first communication system provided in this application. The first communication system 101 includes a device 111 and one or more optoelectronic conversion modules 112. The optoelectronic conversion module 112 may also be referred to as an optical transceiver module or an optical module, etc. This example does not limit the number of devices 111 included in the first communication system 101. The device 111 and the first communication system 101 are integrated devices, or the device 111 is an independent pluggable single board. This example does not limit the number of optoelectronic conversion modules 112 included in the first communication system 101. The optoelectronic conversion module 112 may be integrated with the device 111 or may be pluggable on a single board of the device 111, etc., and there is no specific limitation. Specifically, the device 111 has packaged a processing chip 201 and a connector 203. The processing chip 201 may be one or more chips, or one or more integrated circuits. For example, the processing chip 201 can be one or more optical digital signal processors (oDSPs), field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), system on chips (SoCs), central processor units (CPUs), network processors (NPs), microcontroller units (MCUs), programmable logic devices (PLDs), network card chips, storage interface chips, or other integrated chips, or any combination of the above chips, or processing modules, etc., and the details are not repeated here. The processing chip 201 has a transmit (TX) interface 202, which is connected to a connector 203. The connector 203 is used to provide an electrical interface that realizes a pluggable connection with the optoelectronic conversion module 112. The optoelectronic conversion module 112 includes a modulator 212 connected to the connector 203 and a tunable laser 211 connected to the modulator 212. Tunable laser 211 tunes the wavelength of the emitted optical signal and sends the tuned optical signal to modulator 212. Modulator 212 receives a first service electrical signal from device 111 and modulates the first service electrical signal onto the tuned optical signal to obtain a first service optical signal. Modulator 212 is connected to output optical fiber 213, and then modulator 212 emits the first service optical signal through output optical fiber 213.

[0051] Figure 2b is a structural example diagram of the second communication system provided in this application. The second communication system 102 includes a device 121 and one or more optoelectronic conversion modules 122. This example does not limit the number of devices 121 included in the second communication system 102. For the description of the device 121, please refer to the description of the device 111 shown in Figure 2a, and the details are not repeated here. This example does not limit the number of optoelectronic conversion modules 122 included in the second communication system 102. The optoelectronic conversion module 122 can be integrated with the device 121 or can be plugged into a single board of the device 121, etc., and there is no specific limitation. Specifically, the device 121 has encapsulated a processing chip 231 and a connector 232. The processing chip 201 has a receive (RX) interface 233, and the RX interface 233 is connected to the connector 232. The connector 232 is used to provide an electrical interface, which realizes a pluggable connection with the optoelectronic conversion module 122. The optoelectronic conversion module 122 includes a demodulator 234 connected to a connector 232 and a tunable laser 235 connected to the demodulator 234. The demodulator 234 is connected to an input optical fiber 236 and receives a second service optical signal via the input optical fiber 236. The demodulator 234 receives a tuned optical signal from the tunable laser 235. The demodulator 234 coherently demodulates the second service optical signal based on the tuned optical signal to obtain a second service electrical signal. The demodulator 234 transmits the second service electrical signal to the processing chip 231 via the connector 232 and the RX interface 233.

[0052] FIG3 is a diagram illustrating the structure of the first embodiment of the tunable laser provided in this application, and FIG4 is a diagram illustrating the side view structure of the first embodiment of the tunable laser shown in FIG3 . FIG4 is a diagram illustrating the side view structure of the tunable laser in the XY plane, wherein the XY plane includes direction X and direction Y, direction X being the emission direction of the optical signal after tuning, and direction Y being the direction perpendicular to the substrate surface of the tunable laser. This embodiment takes direction X being perpendicular to direction Y as an example, and in other examples, there may also be a certain angle between direction X and direction Y, which is not specifically limited. This embodiment takes the type of tunable laser being a DBR laser as an example. It should be noted that this embodiment does not limit the type of tunable laser. For example, the type of tunable laser may also be a vertical-cavity surface-emitting laser (VCSEL), a modulated grating y-branch (MG-Y laser), a multi-channel interference laser (MCI laser), a V-cavity laser, and a chirped sampled grating-distributed feedback laser (CSG-DR laser). The tunable laser shown in this embodiment is used to emit a tuned optical signal, the optical power of the tuned optical signal being amplified and the wavelength being tuned. Specifically, the tunable laser includes a substrate 300, on the surface of the substrate 300, a first waveguide module 302, a third waveguide module 304, a gain module 301, and a second waveguide module 303 are sequentially arranged along the direction X. In this embodiment, the third waveguide module 304 is located between the first waveguide module 302 and the gain module 301. In other examples, the third waveguide module 304 may also be located between the gain module 301 and the second waveguide module 303. In this embodiment, the first waveguide module 302, the third waveguide module 304, the gain module 301, and the second waveguide module 303 are monolithically integrated through photonic integration. The tunable laser obtained through monolithic integration can reduce the spectral linewidth corresponding to the output tuned optical signal, thereby improving bandwidth utilization.

[0053] The substrate 300 may be an indium phosphide (InP) substrate, an indium gallium arsenide (InGaAs) substrate, a GaAs substrate, an aluminum gallium indium arsenide (InGaAlAs) substrate, an aluminum gallium arsenide antimonide (InGaAlAsSb) substrate, an aluminum gallium arsenide (AlGaAs) substrate, or a gallium nitride (GaN) substrate, etc., and the specific embodiments are not limited thereto. The gain module 301 includes an N-type doped layer 311 located on the surface of the substrate 300. The N-type doped layer 311 may be N-doped InGaAsP, InP, or GaAs. In this embodiment, the N-doped layer 311 is an N-doped InP layer. For example, the N-doped layer 311 is obtained by implanting N-type semiconductor ions into the InP. The surface of the N-doped layer 311 includes a semiconductor gain medium layer 312. The semiconductor gain medium layer 312 is composed of a semiconductor gain medium material and is used to amplify the power of the optical signal. For example, this embodiment uses a semiconductor gain medium material as a multiple quantum well (MQW) as an example. The gain module 301 also includes a P-type doped layer 313 located on the surface of the semiconductor gain medium layer 312. The P-type doped layer 313 can be P-doped InGaAsP, InP, or GaAs. In this embodiment, the P-type doped layer 313 is P-doped InP as an example. Therefore, the P-type doped layer 313 is a P-InP layer. For example, P-type ions of the semiconductor material are implanted into InP to obtain the P-type doped layer 313. The N-type doped layer 311 and the P-type doped layer 313 form a first PN junction. Specifically, in this embodiment, the first PN junction is a PIN diode (positive intrinsic negative diode, PIN diode) structure as an example. The tunable laser includes two gain electrodes connected to the gain module 301. The two gain electrodes specifically include a gain electrode 314 and a gain electrode 315. It is understood that the gain electrode 314 and the gain electrode 315 can power the gain module 301 and form a circuit loop. The gain electrode 314 is located on the surface of the P-type doped layer 313. Along direction Y, the gain electrode 315 and the gain module 301 are located on both surfaces of the substrate 300. The gain electrodes 315 and 6 are connected to the N-type doped layer 311 through the substrate 300. The description of the position of the gain electrode 315 in this embodiment is an optional example and is not limiting. For example, the gain electrode 315 can be located between the surface of the substrate 300 and the N-type doped layer 311. The gain electrode 314 is used to apply current to the gain module 301, and the gain module 301 is used to emit an optical signal based on the current. That is, the gain module 301 generates an optical signal under the stimulation of the current.Specifically, when current passes through the P-type doped layer 313 and the N-type doped layer 311, electrons flow from the N-type doped layer 311 to the P-type doped layer 313, and holes flow from the P-type doped layer 313 to the N-type doped layer 311, forming a population inversion at the first PN junction. The recombination of electrons and holes generates a light signal and emits it. Referring to Figures 2a and 2b, the gain electrode 314 is connected to the electrical port of the processing chip, and the processing chip is used to send current or voltage to the gain electrode 314 so that the gain electrode 314 applies current to the gain module 301. Optionally, if the photoelectric conversion module includes a processor, the gain electrode 314 is connected to the electrical port of the processor. For a description of the processor type of the photoelectric conversion module, please refer to the description of the processing chip type, and the details are not repeated here.

[0054] The first waveguide module 302 includes an N-type doped layer 321 located on the surface of the substrate 300. For a description of the N-type doped layer 321, please refer to the description of the N-type doped layer 311 of the gain module 301, and the details are not repeated here. The first waveguide module 302 also includes a first reflective layer 322 located on the surface of the N-type doped layer 321. The structure of the first reflective layer 322 shown in this embodiment can be a grating, a microring, or a waveguide. The first reflective layer 322 can be an undoped indium gallium arsenide phosphide (InGaAsP) layer, such as an intrinsic InGaAsP layer, i.e., an i-InGaAsP layer. The first waveguide module 302 also includes a P-type doped layer 323 located on the surface of the first reflective layer 322. For a description of the P-type doped layer 323, please refer to the description of the P-type doped layer 313 of the gain module 301, and the details are not repeated here. The second waveguide module 303 includes an N-type doped layer 331, a second reflective layer 332, and a P-type doped layer 333. For the description of the N-type doped layer 331, the second reflective layer 332, and the P-type doped layer 333 included in the second waveguide module 303, please refer to the description of the N-type doped layer 321, the first reflective layer 322, and the P-type doped layer 323 of the first waveguide module 302, and the details are not repeated here. The first reflective layer 322 and the second reflective layer 332 shown in this embodiment form an optical resonant cavity. Optionally, the first reflective layer 322 and the second reflective layer 332 can form a periodic tuning structure similar to a Fabry-Perot (FP) etalon, which is equivalent to integrating an FP cavity within the tunable laser. It should be noted that this embodiment does not limit the wavelength range that the optical resonant cavity can tune. The optical resonant cavity formed by the first reflective layer 322 and the second reflective layer 332 is used to periodically tune the optical signal emitted by the gain module 301. Specifically, the optical signal emitted by the gain module 301 is reflected back and forth multiple times between the first reflective layer 322 and the second reflective layer 332, thereby interfering with the reflected light to achieve periodic tuning. For example, if the wavelength of the optical signal to be emitted by the tunable laser is a target wavelength, then the optical power of the target wavelength transmitted in the optical resonant cavity will obtain maximum gain, thereby generating peak optical power at the target wavelength. It can be understood that the optical resonant cavity formed by the first reflective layer 322 and the second reflective layer 332 enhances the optical power of the target wavelength by multiple reflections of the optical signal emitted by the gain module. The optical signal having the target wavelength is transmitted from the second waveguide module 303 and then emitted from the tunable laser, while the optical power of the remaining optical signals gradually decreases until it is substantially close to zero.

[0055] The tunable laser shown in this embodiment also includes a first heating element 325 and two first waveguide electrodes. Specifically, the two first waveguide electrodes include a first waveguide electrode 324 and a first waveguide electrode 326. The first waveguide electrode 324 is located on the surface of the P-type doped layer 323, and the first heating element 325 is located on the surface of the first waveguide electrode 324. It should be noted that the description of the positions of the first heating element 325 and the first waveguide electrode 324 in this embodiment is an optional example and is not limiting. For example, the first heating element 325 may be located on the surface of the P-type doped layer 323, and the first waveguide electrode 324 may be located on the surface of the first heating element 325. In this example, the first heating element 325 has a through-hole, and the first waveguide electrode 324 is connected to the P-type doped layer 323 through the through-hole. Along direction Y, the first waveguide electrode 326 and the N-type doped layer 321 are located on both surfaces of the substrate 300, and the first waveguide electrode 326 is connected to the N-type doped layer 321 through the substrate 300. The description of the location of the first waveguide electrode 326 in this embodiment is provided as an optional example and is not intended to be limiting. For example, the first waveguide electrode 326 is positioned between the surface of the substrate 300 and the N-type doped layer 321. The tunable laser described in this embodiment can adjust the target wavelength. Specifically, based on a heat-based tuning method, the first heating element 325 can apply a first heat to the first waveguide module 302. The first waveguide module 302 is configured to tune the target wavelength under the influence of the first heat. The first heating element 325 can be located in an electromagnetic heating layer or a heating resistor on the surface of the first waveguide electrode 324. This embodiment uses a heating resistor as an example, but the specific configuration is not limiting. As shown in Figures 2a and 2b, the first heating element 325 is connected to an electrical port of a processing chip. The processing chip sends a current or voltage to the first heating element 325, which then applies the first heat to the first waveguide module 302 based on the current or voltage. Optionally, if the photoelectric conversion module 112 includes a processor, the first heating element 325 is connected to an electrical port of the processor. Under the action of the first heat, the refractive index of the first reflective layer 322 of the first waveguide module 302 changes, thereby changing the target wavelength.

[0056] In this embodiment, the optical signal emitted by the gain module 301 enters the first waveguide module 302. When the first waveguide module 302 is excited by the optical signal, electrons are stimulated to transition to the conduction band, forming conduction band electrons and valence band holes, commonly known as photogenerated carriers. The photogenerated carriers generated by the first waveguide module 302 are referred to as first photogenerated carriers below. The concentration of first photogenerated carriers diffuses within the first waveguide module 302. Due to their short lifetime, the phase noise of the tunable laser increases at low frequencies (i.e., near megahertz). Furthermore, the first photogenerated carriers within the first waveguide module 302 undergo random recombination. Specifically, new first photogenerated carriers are continuously generated in the first waveguide module 302. The first photogenerated carriers generated in the first waveguide module 302 at different times will recombine. The recombination will cause the energy transition of the first photogenerated carriers. The state of the first photogenerated carriers with relatively high energy is unstable. The unstable first photogenerated carriers appear as unstable and random noise in the tunable laser.

[0057] The tunable laser shown in this embodiment can reduce the concentration of first photogenerated carriers in the first waveguide module 302, thereby effectively reducing the probability of random recombination of the first photogenerated carriers in the first waveguide module 302, achieving the purpose of suppressing random recombination of the first photogenerated carriers in the first waveguide module 302 and effectively suppressing the phase noise of the first waveguide module 302. To achieve this purpose, the first waveguide electrode of the tunable laser can apply a first reverse bias voltage to the first waveguide module 302. This first reverse bias voltage applies a reverse potential difference to the first PN junction, which can deplete the first photogenerated carriers in the first waveguide module 302, thereby reducing the concentration of the first photogenerated carriers in the first waveguide module 302. Specifically, the first photogenerated carriers flow between the first PN junctions in the first waveguide module 302. When the first waveguide electrode applies a reverse potential difference to the first PN junction, the first PN junction is placed in a reverse cutoff state. The first PN junction in the reverse cutoff state depletes the first photogenerated carriers. As shown in FIG3 , the first waveguide electrode 324 is connected to the P-type doped layer 323 , and thus is connected to the anode of the first PN junction (i.e., the P-type doped layer 323 ). The first waveguide electrode 326 is connected to the N-type doped layer 321 , and thus is connected to the cathode of the first PN junction (i.e., the N-type doped layer 321 ). The first waveguide electrode 324 and the first waveguide electrode 326 apply the first reverse bias voltage to the first PN junction. It will be understood that the first reverse bias voltage refers to the voltage applied between the first waveguide electrode 324 and the first waveguide electrode 326 having a polarity opposite to that of the first PN junction. The first PN junction in the reverse cutoff state causes the first photogenerated carriers in the first waveguide module 302 to flow out of the first waveguide module 302 . The first photogenerated carriers flowing out of the first waveguide module 302 flow to the ground via the ground terminal of the first waveguide electrode. Among them, the rate of the first photogenerated carriers flowing out of the first waveguide module 302 is positively correlated with the magnitude of the first reverse bias voltage applied to the first waveguide electrode, that is, the greater the first reverse bias voltage applied to the first PN junction, the faster the rate of the first photogenerated carriers flowing out of the first waveguide module 302, thereby making the concentration of the first photogenerated carriers in the first waveguide module 302 lower.

[0058] Optionally, the tunable laser shown in this embodiment further includes a second heating element 326 and two waveguide electrodes, specifically a second waveguide electrode 334 and a second waveguide electrode 336. The second waveguide electrode 334 is located on the surface of the P-type doped layer 333, and the second heating element 335 is located on the surface of the second waveguide electrode 334. It should be noted that the description of the positions of the second heating element 335 and the second waveguide electrode 334 in this embodiment is for optional examples and is not limiting. For example, the second heating element 335 may be located on the surface of the P-type doped layer 333, and the second waveguide electrode 334 may be located on the surface of the second heating element 335. In this example, the second heating element 335 has a through-hole, and the second waveguide electrode 334 is connected to the P-type doped layer 333 through the through-hole. Along direction Y, the second waveguide electrode 336 and the N-type doped layer 331 are located on both surfaces of the substrate 300, and the second waveguide electrode 336 is connected to the N-type doped layer 331 through the substrate 300. The description of the position of the second waveguide electrode 336 in this embodiment is an optional example and is not limiting. For example, the second waveguide electrode 336 is located between the surface of the substrate 300 and the N-type doped layer 331. The tunable laser shown in this embodiment can adjust the target wavelength. Specifically, based on a thermal tuning method, the second heating element 335 can apply a second heat to the second waveguide module 303. The second waveguide module 303 is configured to tune the target wavelength under the influence of the second heat. For details, please refer to the description of the thermal tuning method of the first waveguide module 302, and the details are not repeated here. The second waveguide electrode 334 and the second waveguide electrode 336 apply a second reverse bias voltage to the second waveguide module 303. The second reverse bias voltage applies a reverse potential difference to the second PN junction of the second waveguide module 303. The reverse potential difference can deplete the second photogenerated carriers in the second waveguide module 303, thereby reducing the concentration of the second photogenerated carriers in the second waveguide module 303. For a description of the specific process, please refer to the description of the process of depleting the first photogenerated carriers in the first waveguide module 302, and the details will not be repeated here.

[0059] The tunable laser shown in this embodiment also includes a third waveguide module 304. This embodiment does not limit the location of the third waveguide module 304, as long as the third waveguide module 304 is located within the optical resonant cavity of the tunable laser. The third waveguide module 304 is used to adjust the phase of the optical signal transmitted within the optical resonant cavity, thereby precisely locking the wavelength of the optical signal emitted from the optical resonant cavity to the target wavelength. The third waveguide module 304 shown in this embodiment includes an N-type doped region 341 located on the surface of the substrate 300, a waveguide dielectric layer 342 located on the surface of the N-doped layer 341, and a P-type doped layer 343 located on the surface of the waveguide dielectric layer 342. Optionally, the tunable laser further includes a third heating element 345 and two third waveguide electrodes. Specifically, the two third waveguide electrodes include a third waveguide electrode 344 and a third waveguide electrode 346. For a description of the third heating element 345 and the two third waveguide electrodes, refer to the description of the first heating element 325 and the two first waveguide electrodes, and are not further described here. The third heating element 345 applies a third heat to the third waveguide module 304, which is used to change the refractive index of the third waveguide module 304, thereby achieving precise tuning to the target wavelength. The third waveguide electrode 344 and the third waveguide electrode 346 are used to apply a third reverse bias voltage to the third waveguide module 304, which is used to place the third waveguide module 304 in a reverse cutoff state. For a description of suppressing phase noise by placing the third waveguide module 304 in a reverse cutoff state, refer to the description of suppressing phase noise by placing the first waveguide module 302 in a reverse cutoff state, and are not further described here.

[0060] In this embodiment, one or more of the first waveguide module, the second waveguide module, and the third waveguide module are in a reverse cutoff state. The waveguide module in the reverse cutoff state can effectively reduce the concentration of photogenerated carriers in the waveguide module and effectively suppress phase noise. The following describes the beneficial effects of the tunable laser provided by this embodiment:

[0061] The tunable laser shown in this embodiment uses a DBR laser as an example. DBR lasers offer advantages such as high integration, low cost, and high wave cutting speed. The phase noise of a DBR laser is primarily composed of three components: spontaneous emission noise, external disturbance noise, and random disturbance noise. The external disturbance noise is introduced by the tunable laser circuit and the ambient noise in the environment in which the tunable laser is located. The random disturbance noise is introduced by injection noise and random carrier recombination.

[0062] Existing solutions achieve the goal of tuning the target wavelength by injecting current into the waveguide module. This current changes the refractive index of the waveguide module, thereby tuning the target wavelength. However, this injected current increases the carrier concentration in the waveguide module, increasing the probability of random carrier recombination. This causes a sharp increase in the random perturbation noise term in the laser's phase noise, increasing the linewidth and phase noise of the DBR laser.

[0063] The tunable laser shown in this embodiment changes the target wavelength of the tunable laser's output by changing the refractive index of the waveguide module through thermal tuning. Adjusting the refractive index through thermal tuning replaces the existing approach of changing the refractive index by injecting current into the waveguide module. Because there is no need to inject current to change the refractive index, the effect of random perturbation noise on the linewidth of the tunable laser is effectively reduced. Furthermore, the carrier concentration in the waveguide module is reduced, suppressing noise caused by random carrier recombination. This effectively reduces the linewidth and improves the bandwidth utilization of the tunable laser.

[0064] Figure 5 is a comparative example of the phase noise curves of the tunable laser provided by this application and the existing DBR laser. In the coordinate system shown in Figure 5, the horizontal axis is the frequency of the noise, in Hertz (Hz), and the vertical axis is the intensity of the phase noise. The phase noise curve shown in Figure 5 represents the magnitude of the phase noise within a unit frequency range, and the unit can be radians / root Hertz (rad / Hz) or degrees / root Hertz (deg / Hz). Phase noise curve 501 shown in Figure 5 is the phase noise curve of the existing DBR laser, while phase noise curve 502 is the phase noise curve of the tunable laser provided in this embodiment. Combining the phase noise curve 501 and the phase noise curve 502, it can be seen that the phase noise curve 502 of the tunable laser of this embodiment is significantly reduced in the range of 1 MHz to 100 MHz compared to the phase noise curve 501 of the existing DBR laser. Therefore, it can be seen that the tunable laser shown in this embodiment can effectively suppress the random disturbance noise term by placing the PN junction of the waveguide module in a reverse cutoff state. It can be understood that the tunable laser provided by this embodiment effectively suppresses the phase noise in the low frequency band (i.e., the MHz band).

[0065] The above embodiment uses the example of a first waveguide module 302 including a first reflective layer 322 and a second waveguide module 302 including a second reflective layer 332, so that an optical resonant cavity is formed between the first reflective layer 322 and the second reflective layer 332. In the embodiments shown in Figures 6a and 6b, the methods for forming the optical resonant cavity are different. Figure 6a is a diagram illustrating a second embodiment of the tunable laser provided in this application. Figure 6b is a diagram illustrating a side view of the embodiment of the tunable laser shown in Figure 6a. Figures 6a and 6b illustrate side views of the tunable laser in the XY plane. For a description of the XY plane, please refer to the description of Figure 3 and will not be further elaborated.

[0066] The tunable laser includes a substrate 600. A first waveguide module 602, a gain module 601, and a second waveguide module 603 are sequentially arranged on the surface of the substrate 600 along direction X. For a description of the substrate 600 and gain module 601 shown in this embodiment, please refer to Figures 3 and 4 ; details are omitted here. The first waveguide module 602 includes an N-type doped layer 621, a waveguide dielectric layer 622, and a P-type doped layer 623. For a description of the N-type doped layer 621 and the P-type doped layer 623, please refer to the description of the N-type doped layer and the P-type doped layer of the first waveguide module shown in Figures 3 and 4 ; details are omitted here. The waveguide dielectric layer 622 is located between the N-type doped layer 621 and the P-type doped layer 623. The waveguide dielectric layer 622 is composed of a waveguide material and is used to transmit optical signals. Along direction X, the surface of the first waveguide module 602 facing away from the gain module 601 is coated with a first reflective layer 641. It is understood that the optical signal emitted by the gain module 601 is transmitted to the first reflective layer 641 via the waveguide dielectric layer 622. In the first waveguide module 602, the waveguide dielectric layer 622 at least covers the waveguide dielectric layer 622. The second waveguide module 603 includes an N-type doped layer 631, a waveguide dielectric layer 632, and a P-type doped layer 633. For a description of the N-type doped layer 631 and the P-type doped layer 633, please refer to the description of the N-type doped layer and the P-type doped layer included in the second waveguide module shown in Figures 3 and 4, and the details are not repeated here. The waveguide dielectric layer 632 is located between the N-type doped layer 631 and the P-type doped layer 633. The waveguide dielectric layer 632 is composed of a waveguide material and is used to transmit optical signals. Along the direction X, the surface of the second waveguide module 603 facing away from the gain module 601 is coated to form a second reflective layer 642. It is understood that the optical signal emitted by the gain module 601 is transmitted to the second reflective layer 642 via the waveguide dielectric layer 632. An optical resonant cavity is formed between the first reflective layer 641 and the second reflective layer 642 in this embodiment. For an explanation of how the optical resonant cavity tunes the wavelength of an optical signal, please refer to FIG. 3 and FIG. 4 , and details are omitted for brevity.

[0067] The tunable laser shown in this embodiment includes a first heating element 625 for thermally tuning the first waveguide module 602 and a second heating element 635 for thermally tuning the second waveguide module 603. For details, please refer to the description of the first and second heating elements shown in Figures 3 and 4 , and detailed description is omitted. The tunable laser shown in this embodiment also includes a first waveguide electrode 624 and a first waveguide electrode 626 for suppressing phase noise of the first waveguide module 602, and a second waveguide electrode 634 and a second waveguide electrode 636 for suppressing phase noise of the second waveguide module 603. Please refer to Figures 3 and 4 for description of the first and second waveguide electrodes, and detailed description is omitted.

[0068] In other embodiments, the first reflective layer may be located within the first waveguide module as shown in Figures 3 and 4 , and the second reflective layer may be deposited on the surface of the waveguide dielectric layer as shown in Figure 6b . For another example, the first reflective layer may be deposited on the surface of the waveguide dielectric layer as shown in Figure 6b , and the second reflective layer may be located within the second waveguide module as shown in Figures 3 and 4 . The specific embodiments are not limited in this embodiment.

[0069] FIG7 is a side view of the structure of the second embodiment of the tunable laser shown in FIG3 . FIG7 shows a side view of the structure of the tunable laser in the XY plane. For the description of the XY plane, please refer to the corresponding description of FIG4 and will not be repeated here. The tunable laser includes a substrate 700. On the surface of the substrate 700, along the direction X, a first waveguide module 702, a third waveguide module 704, a gain module 701, and a second waveguide module 703 are arranged in sequence. In this embodiment, the third waveguide module 704 is located between the first waveguide module 702 and the gain module 701. In other examples, the third waveguide module 704 can also be located between the gain module 701 and the second waveguide module 703. For the description of the substrate 700 and the gain module 701 shown in this embodiment, please refer to the corresponding description of FIG3 and will not be repeated here.

[0070] The first waveguide module 702 includes a P-type doped layer 721, a first reflective layer 722, and an N-type doped layer 723, which are sequentially located on the surface of the substrate 700. The tunable laser also includes a first waveguide electrode 724, a first waveguide electrode 326, and a first heating element 725. For a description of the P-type doped layer 721, the first reflective layer 722, the N-type doped layer 723, the first waveguide electrode 724, the first waveguide electrode 326, and the first heating element 725, please refer to the corresponding descriptions of Figures 3 and 4, and the details are not repeated here. The first waveguide module 702 shown in this embodiment differs from the first waveguide module 302 shown in Figure 3 in that the P-type doped layer 721 and the N-type doped layer 723 are positioned differently in the first waveguide module, so that the first PN junction formed by the P-type doped layer 721 and the N-type doped layer 723 shown in this embodiment has a NIP structure (inverted PIN structure). The second waveguide module 703 includes a P-type doped layer 731, a second reflective layer 732, and an N-type doped layer 733, sequentially located on the surface of the substrate 700. The tunable laser shown in this embodiment also includes a second waveguide electrode 734, a second waveguide electrode 736, and a second heating element 735. For a description of the P-type doped layer 731, the second reflective layer 732, the N-type doped layer 733, the second waveguide electrode 734, the second waveguide electrode 736, and the second heating element 735, please refer to the corresponding descriptions of FIG. 3 and FIG. 4 , and detailed descriptions are omitted here. The second waveguide module 703 shown in this embodiment differs from the second waveguide module 303 shown in FIG. 3 in that the P-type doped layer 731 and the N-type doped layer 733 are positioned differently within the second waveguide module, so that the PN junction formed by the P-type doped layer 731 and the N-type doped layer 733 shown in this embodiment forms a NIP structure.

[0071] In this embodiment, gain module 701 is used to output an optical signal. For a description of gain module 701, please refer to the corresponding descriptions in Figures 3 and 4 , and the details are omitted here. The optical signal output by gain module 701 enters first waveguide module 702. When first waveguide module 702 is excited by the optical signal, the concentration of the first photogenerated carriers in first waveguide 702 is increased. The tunable laser shown in this embodiment can reduce the concentration of the first photogenerated carriers in the first waveguide module 702, thereby effectively reducing the probability of random recombination of the first photogenerated carriers in the first waveguide module 702, achieving the purpose of suppressing the random recombination of the first photogenerated carriers in the first waveguide module 702, and effectively suppressing the phase noise of the first waveguide module 702. To achieve this purpose, the first waveguide electrode 724 and the first waveguide electrode 726 of the tunable laser can apply a first reverse bias voltage to the first waveguide module 702. The first reverse bias voltage will apply a reverse potential difference to the first PN junction. The reverse potential difference can deplete the first photogenerated carriers in the first waveguide module 702, thereby reducing the concentration of the first photogenerated carriers in the first waveguide module 702. Specifically, the first photogenerated carriers flow between the first PN junctions in the first waveguide module 702. When the first waveguide electrode applies a reverse potential difference to the first PN junction, the first PN junction enters a reverse cutoff state. In this reverse cutoff state, the first PN junction depletes the first photogenerated carriers. As shown in FIG7 , the first waveguide electrode 724 is connected to the N-type doped layer 723, indicating that the first waveguide electrode 724 is connected to the cathode of the first NIP structure (i.e., the N-type doped layer 723). The first waveguide electrode 726 is connected to the P-type doped layer 721, indicating that the first waveguide electrode 726 is connected to the anode of the first NIP structure (i.e., the P-type doped layer 721). This first reverse bias voltage causes the NIP structure of the first waveguide module 702 to enter a reverse cutoff state. Consequently, the NIP structure causes the first photogenerated carriers in the first waveguide module 702 to flow out of the first waveguide module 702. The first photogenerated carriers flowing out of the first waveguide module 702 flow to ground via the ground terminal of the first waveguide electrode. For the description of how the second waveguide electrode 734 suppresses the second photogenerated carrier concentration in the second waveguide module 703 , please refer to the description of how the first waveguide electrode 724 suppresses the first photogenerated carrier concentration in the first waveguide module 702 , and details are not repeated here.

[0072] The tunable laser shown in this embodiment may also include a third waveguide module 704. The location of the third waveguide module 704 is not limited in this embodiment, as long as the third waveguide module 704 is located within the optical resonant cavity of the tunable laser. The third waveguide module 704 is used to adjust the phase of the optical signal transmitted within the optical resonant cavity, thereby accurately locking the wavelength of the optical signal emitted from the optical resonant cavity to the target wavelength. The third waveguide module 704 shown in this embodiment includes a P-type doped region 741, a waveguide dielectric layer 742, and an N-type doped layer 743, sequentially located on the surface of the substrate 700. For a detailed description, please refer to the description of the third waveguide module shown in Figures 3 and 4, and the details are not repeated here. The tunable laser may also include a third waveguide electrode 744, a third waveguide electrode 746, and a third heating element 745. For a description of the third waveguide electrode 744, the third waveguide electrode 746, and the third heating element 745, please refer to the corresponding description of Figures 3 and 4, and the details are not repeated here. The third heating element 745 applies a third heat to the third waveguide module 704. This third heat is used to change the refractive index of the third waveguide module 704, thereby achieving precise tuning of the target wavelength. The third waveguide electrode is used to apply a third reverse bias voltage to the third waveguide module 304. This third reverse bias voltage is used to put the third waveguide module 304 into a reverse cutoff state.

[0073] The positions of the first reflective layer 722 and the second reflective layer 732 shown in this embodiment can also be seen in FIG6 b , and detailed description thereof will not be repeated.

[0074] In the above embodiment, the first PN junction is located inside the first waveguide module, while in the embodiment shown in FIG8 , the first PN junction is located on the surface of the first waveguide module. FIG8 is a structural diagram illustrating a second embodiment of a tunable laser provided in this application. The tunable laser includes a substrate 805 , on the surface of which, along direction X, a first waveguide module 801 , a third waveguide module 802 , a gain module 803 , and a second waveguide module 804 are sequentially arranged. For a description of direction X, please refer to the corresponding descriptions in FIG3 and FIG4 , and the details are not repeated here. In this embodiment, the third waveguide module 802 is located between the first waveguide module 801 and the gain module 803 . In other examples, the third waveguide module 802 can also be located between the gain module 803 and the second waveguide module 804 . In this embodiment, the substrate 805 is an InP substrate. The tunable laser is cut along section 800 to obtain the cross-sectional diagram shown in FIG9 , wherein FIG9 is a cross-sectional diagram illustrating a cross-sectional structure of the tunable laser shown in FIG8 . The cross section shown in this embodiment is parallel to the YZ plane, and the direction Z is perpendicular to the XY plane. For a description of the XY plane, please refer to the corresponding description of Figures 3 and 4, and no further details are given here. It will be understood that Figure 9 shows an example cross-sectional view of the first waveguide module 801 in the YZ plane. The first waveguide module 801 shown in this embodiment includes a first reflective layer 912. For a description of the first reflective layer 912, please refer to the corresponding description of Figures 3 and 4, and no further details are given here. The first waveguide module 801 specifically includes a P-type doped region 811 and an N-type doped region 812. Specifically, the P-type doped region 811 specifically includes a P-type doped layer 912 deposited on the surface of the first waveguide module 801 and a first waveguide electrode 911 located on the surface of the P-type doped layer 912. For a description of the position of another first waveguide electrode for forming a circuit loop included in the tunable laser shown in this embodiment, please refer to the corresponding description of Figures 3 and 4, and no further details are given here. The N-type doped region 812 specifically includes an N-type doped layer 902 deposited on the surface of the first waveguide module 801 and a first waveguide electrode 901 located on the surface of the N-type doped layer. The P-type doped layer 912 and the N-type doped layer 902 shown in this embodiment constitute a first PN junction. For a description of the first PN junction, please refer to the corresponding descriptions in FIG. 3 and FIG. 4 , and further details are omitted. The InP substrate surface of the first waveguide module shown in this embodiment is also connected to a first heating element 900, which is used to provide a first heat source to the first PN junction. For a description of providing the first heat source to the first PN junction, please refer to the corresponding descriptions in FIG. 3 and FIG. 4 , and further details are omitted.

[0075] In this embodiment, the optical signal emitted by the gain module 803 enters the first waveguide module 801. When the first waveguide module 801 is excited by the optical signal, first photogenerated carriers are generated. The tunable laser shown in this embodiment can reduce the concentration of the first photogenerated carriers in the first waveguide module 801, thereby effectively reducing the probability of random recombination of the first photogenerated carriers in the first waveguide module 801, achieving the purpose of suppressing random recombination of the first photogenerated carriers in the first waveguide module 801 and effectively suppressing the phase noise of the first waveguide module 801. To achieve this purpose, the two first waveguide electrodes included in the first waveguide module can apply a first reverse bias voltage to the first waveguide module 801. This first reverse bias voltage applies a reverse potential difference to the first PN junction, which can deplete the first photogenerated carriers in the first waveguide module 801, thereby reducing the concentration of the first photogenerated carriers in the first waveguide module 801. For a description of the first reverse bias voltage, please refer to the corresponding description of FIG. 3 and FIG. 4 , and the details are not repeated here. The second waveguide module 804 shown in this embodiment may also include a P-type doping region and an N-type doping region, and the third waveguide module 802 may also include a P-type doping region and an N-type doping region. For the description of the P-type doping region and the N-type doping region, please refer to the description of the P-type doping region and the N-type doping region included in the first waveguide module 801, and the details are not repeated here.

[0076] In the above embodiments, the first waveguide module is used to form an optical resonant cavity. In other examples, the first waveguide module may also be located within the optical resonant cavity. For example, a tunable laser includes a first waveguide module, a fourth waveguide module, and a fifth waveguide module. The fourth and fifth waveguide modules are used to form an optical resonant cavity. For a description of the structures of the fourth and fifth waveguide modules, please refer to the corresponding descriptions of Figures 3, 4, 6a, and 6b, and will not be further described. The first waveguide module is located within the optical resonant cavity formed by the fourth and fifth waveguide modules. For a description of the structure of the first waveguide module, please refer to the description of the third waveguide module shown in Figures 3 and 4, and will not be further described.

[0077] FIG10 is a diagram illustrating the structure of the third embodiment of the tunable laser provided in this application. Specifically, FIG10 shows an example diagram of the structure of the tunable laser in the XY plane. For the description of the XY plane, please refer to the corresponding description of FIG3 , which will not be described in detail. The tunable laser shown in this embodiment includes a substrate 1000. Along the X direction, the surface of the substrate 1000 includes a first waveguide module 1002, a third waveguide module 1003, a gain module 1004, a second waveguide module 1005, and a semiconductor optical amplifier (SOA) 1006. For the description of the first waveguide module 1002, the third waveguide module 1003, the gain module 1004, and the second waveguide module 1005 shown in this embodiment, please refer to FIG3 , FIG4 , FIG6a , FIG6b , FIG7 , FIG8 , and FIG9 , which will not be described in detail. In this embodiment, the tuned optical signal emitted from the second waveguide module 1005 is transmitted to the SOA 1006. The SOA 1006 is configured to amplify the power of the tuned optical signal to output an amplified optical signal. In this embodiment, the first waveguide module 1002, the third waveguide module 1003, the gain module 1004, the second waveguide module 1005, and the SOA 1006 are located on the same substrate 1000.

[0078] Figure 11 is a structural example diagram of the fourth embodiment of the tunable laser provided in this application. Specifically, Figure 11 shows an example diagram of the structure of the tunable laser in the XY plane. For the description of the XY plane, please refer to the corresponding description of Figure 3, which will not be described in detail. The tunable laser shown in this embodiment includes a substrate 1100. Along the direction X, the surface of the substrate 1100 includes a detector 1106, a first waveguide module 1102, a third waveguide module 1103, a gain module 1104, and a second waveguide module 1105 in sequence. For the description of the first waveguide module 1102, the third waveguide module 1103, the gain module 1104, and the second waveguide module 1105 shown in this embodiment, please refer to Figures 3, 4, 6a, 6b, 7, 8, and 9, which will not be described in detail. In this embodiment, the tuned optical signal emitted by the second waveguide module 1105. The detector 1106 can be a photodiode (positive intrinsic-negative, PIN) or an avalanche photo diode (APD). The detector 1106 is used to receive the optical signal transmitted from the first waveguide module 1102 and perform photoelectric conversion on the optical signal to obtain a detection electrical signal. The detector 1106 can detect the performance of the tunable laser based on the detection electrical signal, for example, detecting the wavelength, optical power, linewidth and fault detection of the tuned optical signal, etc. The specific detection type is not limited. In this embodiment, the first waveguide module 1102, the third waveguide module 1103, the gain module 1104, the second waveguide module 1105 and the detector 1106 are located on the same substrate 1100 as an example.

[0079] FIG12 is a diagram illustrating the structure of the fifth embodiment of the tunable laser provided in this application. FIG12 shows an example diagram of the structure of the tunable laser in the XY plane. For the description of the XY plane, please refer to the corresponding description of FIG3 and will not be described in detail. The tunable laser shown in this embodiment includes a substrate 1200. Along the X direction, the surface of the substrate 1200 includes a first SOA 1201, a first waveguide module 1202, a third waveguide module 1203, a gain module 1204, a second waveguide module 1205, and a second SOA 1206. For the description of the first waveguide module 1202, the third waveguide module 1203, the gain module 1204, the second waveguide module 1205, and the second SOA 1206 shown in this embodiment, please refer to the corresponding description of FIG10 and will not be described in detail. The first SOA 1201 is configured to receive an optical signal transmitted from the first waveguide module 1202 and amplify the power of the optical signal to facilitate detection of the performance of the tunable laser using the amplified optical signal. For a description of the first SOA 1201, refer to the description of the second SOA and are not further elaborated here. This embodiment assumes that the first SOA 1201, first waveguide module 1202, third waveguide module 1203, gain module 1204, second waveguide module 1205, and second SOA 1206 are located on the same substrate 1200.

[0080] FIG13 is a diagram illustrating the structure of the sixth embodiment of the tunable laser provided in this application. FIG13 shows an example diagram of the structure of the tunable laser in the XY plane. For the description of the XY plane, please refer to the corresponding description of FIG3 , which will not be described in detail. The tunable laser shown in this embodiment includes a substrate 1300. Along the X direction, the surface of the substrate 1300 includes a detector 1307, a first SOA 1301, a first waveguide module 1302, a third waveguide module 1303, a gain module 1304, a second waveguide module 1305, and a second SOA 1306. For the description of the detector 1307 shown in this embodiment, please refer to the corresponding description of FIG11 . For the description of the first SOA 1301, the first waveguide module 1302, the third waveguide module 1303, the gain module 1304, the second waveguide module 1305, and the second SOA 1306, please refer to the corresponding description of FIG12 , which will not be described in detail. In this embodiment, the detector 1307 , the first SOA 1301 , the first waveguide module 1302 , the third waveguide module 1303 , the gain module 1304 , the second waveguide module 1305 and the second SOA 1306 are located on the same substrate 1300 as an example.

[0081] The embodiment of the present application provides a photoelectric conversion module, which includes the tunable laser shown in the above embodiment. For the description of the structure of the photoelectric conversion module, please refer to Figures 2a and 2b, and the specific details are not repeated here. This embodiment does not limit the packaging form of the photoelectric conversion module. For example, the packaging form of the photoelectric conversion module can be an optical transceiver board (OTB), a near package optical module (NPO), or an on-board optical module (OBO) based on optical input and output interface (OIO) technology, etc. The specific type is not limited.

[0082] The embodiment of the present application also provides a communication system. For the description of the structure of the communication system, please refer to Figures 1, 2a and 2b, and the details are not repeated here.

[0083] An embodiment of the present application further provides an optical network, which includes a first communication system and a second communication system. For a description of the optical network structure, please refer to FIG1 , and details are omitted here.

[0084] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A tunable laser, characterized in that: It includes a gain module, a first waveguide module, a gain electrode, a first waveguide electrode and a first heating element, wherein the gain module is connected to the gain electrode, the first waveguide electrode and the first heating element are respectively connected to the first waveguide module, and the first waveguide module includes a first PN junction; The gain electrode is used to apply a current to the gain module, and the gain module is used to emit an optical signal according to the current; the first heating element is used to apply a first heat to the first waveguide module, and the first waveguide module is used to tune the wavelength of the optical signal under the action of the first heat, so that the tunable laser emits the optical signal tuned by the first waveguide module; The first waveguide electrode is used to apply a first reverse bias voltage to the first PN junction, and the first reverse bias voltage is used to put the first PN junction in a reverse cutoff state.

2. The tunable laser according to claim 1, characterized in that: The tunable laser further includes a second waveguide module. The first waveguide module and the second waveguide module form an optical resonant cavity for tuning the wavelength of the optical signal. The gain module is located in the optical resonant cavity.

3. The tunable laser according to claim 2, characterized in that: The tunable laser further comprises a second heating element, wherein the second heating element is connected to the second waveguide module; The second heating element is used to apply a second heat to the second waveguide module, and the second waveguide module is used to tune the wavelength of the optical signal under the action of the second heat.

4. The tunable laser according to claim 2 or 3, characterized in that: The tunable laser further comprises a second waveguide electrode, the second waveguide electrode is connected to the second waveguide module, and the second waveguide module comprises a second PN junction; The second waveguide electrode is used to apply a second reverse bias voltage to the second PN junction, and the second reverse bias voltage is used to put the second PN junction in a reverse cutoff state.

5. The tunable laser according to any one of claims 2 to 4, characterized in that: The tunable laser further comprises a third waveguide module and a third heating element, wherein the third heating element is connected to the third waveguide module, and the third waveguide module is located in the optical resonant cavity; The third heating element is used to apply a third heat to the third waveguide module, and the third waveguide module is used to tune the wavelength of the optical signal under the action of the third heat.

6. The tunable laser according to claim 5, characterized in that: The tunable laser further comprises a third waveguide electrode, the third waveguide electrode is connected to the third waveguide module, and the third waveguide module comprises a third PN junction; The third waveguide electrode is used to apply a third reverse bias voltage to the third PN junction, and the third reverse bias voltage is used to put the third PN junction in a reverse cutoff state.

7. The tunable laser according to claim 1, characterized in that: The tunable laser comprises a fourth waveguide module and a fifth waveguide module, the fourth waveguide module and the fifth waveguide module form an optical resonant cavity for tuning the wavelength of the optical signal, and the gain module and the first waveguide module are located in the optical resonant cavity.

8. The tunable laser according to any one of claims 1 to 7, characterized in that: The first PN junction is located inside the first waveguide module, or the first PN junction is located on a surface of the first waveguide module.

9. The tunable laser according to any one of claims 1 to 8, characterized in that: The first waveguide electrode is located between the first waveguide module and the first heating element, or the first heating element is located between the first waveguide electrode and the first waveguide module, and the first heating element has a through hole, and the first waveguide electrode is connected to the first waveguide module through the through hole.

10. A photoelectric conversion module, characterized in that: It comprises a modulator, an output optical fiber and the tunable laser according to any one of claims 1 to 9, wherein the modulator is connected to the tunable laser and the output optical fiber respectively; The modulator is used to receive the first service electrical signal and the tuned optical signal from the tunable laser; The modulator is further configured to modulate the first service electrical signal onto the tuned optical signal to obtain a first service optical signal, and emit the first service optical signal through the output optical fiber.

11. A photoelectric conversion module, characterized in that: It comprises a demodulator, an input optical fiber and the tunable laser according to any one of claims 1 to 9, wherein the demodulator is connected to the tunable laser and the input optical fiber respectively; The demodulator is used to receive the second service optical signal from the input optical fiber and receive the tuned optical signal from the tunable laser; The demodulator is further configured to coherently demodulate the second service optical signal according to the tuned optical signal to obtain a second service electrical signal.

12. A communication system, characterized in that: The device comprises a device and the photoelectric conversion module as claimed in claim 10, wherein the device comprises a processing chip and a connector, wherein the processing chip is connected to the photoelectric conversion module via the connector, and wherein the processing chip is used to send the first service electrical signal to the photoelectric conversion module.

13. A communication system, characterized in that: The device comprises a device and the photoelectric conversion module as claimed in claim 11, wherein the device comprises a processing chip and a connector, wherein the processing chip is connected to the photoelectric conversion module via the connector, and wherein the processing chip is used to receive the second service electrical signal from the photoelectric conversion module.

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