On-chip wavelength adaptive distributed feedback structure and laser thereof

Abstract

The invention provides an on-chip wavelength adaptive distribution feedback structure and a laser thereof, the structure comprises an asymmetric chaotic structure, a laser signal is totally reflected and propagated along a cavity of the asymmetric chaotic structure until the laser signal is completely absorbed in the cavity or does not meet a total reflection condition, and the laser signal is emitted from the outer wall of the cavity. A scattering signal generated by the laser signal in the total reflection propagation process is reversely transmitted back to a laser signal input port of the cavity along a total reflection propagation path; the sum of vectors of the laser signal in the total reflection propagation process is not zero. The cavity has the wavelength self-adaption characteristic and can break through the upper limit of the Q value of the cavity, the laser signal input port and the scattered signal output port are the same port, and input of laser signals and collection of the scattered signals are facilitated.

Description

Technical Field

[0001] The invention belongs to the field of lasers, and in particular relates to an on-chip wavelength adaptive distributed feedback structure and a laser thereof. Background Art

[0002] Integrated narrow linewidth lasers are the core light sources for important engineering applications such as dense wavelength division multiplexing systems, distributed fiber sensing systems, and fiber-optic hydrophones. Wavelength adaptive distributed weak feedback laser architecture is a new type of laser architecture with features such as linewidth depth compression, gapless wavelength tuning, pure optical feedback, and wavelength adaptation. It is particularly advantageous in the fields of wavelength precision tuning and dense wavelength division multiplexing. Distributed weak feedback laser architecture is now facing the technical challenge of integration. The current integration solutions include:

[0003] (1) High-Q whispering gallery mode (WGM) microcavity structure, that is, using an All-pass high-Q WGM microcavity to collect the backscattering of the whispering gallery mode to obtain a distributed weak feedback signal. The WGM structure has strict restrictions on the wavelength and phase of the laser. Only wavelengths that meet the phase matching can be injected into the WGM to accumulate backscattering. It does not have the characteristics of wavelength adaptation, and only when the Q of the WGM is very high can the cavity accumulate enough scattered signals. The high-Q WGM process is complex, and the higher the Q value, the lower the coupling efficiency. Theoretically, there will be a bottleneck in the backscattering intensity of the WGM. On the other hand, as lasers gradually develop towards on-chip integration, the method of preparing quartz high-Q WGM using liquid surface tension is difficult to integrate with laser chips. At present, silicon-based materials often have problems such as rough waveguide processing, and the Q value is difficult to break through 10 8 Silicon materials only have 10 5 .

[0004] (2) Scattering-enhanced fiber, that is, using scattering-enhanced fiber to reduce the requirement for the length of the scattering waveguide. Scattering fiber is prone to introducing environmental noise due to problems with the fiber structure itself, resulting in high low-frequency noise of the laser and poor wavelength stability. Summary of the invention

[0005] The present invention provides an on-chip wavelength adaptive distributed feedback structure and a laser thereof, so as to solve the problem that the current integrated distributed feedback structure with a high signal-to-noise ratio does not have a wavelength adaptive characteristic and is affected by the process, and its Q value improvement has an upper limit.

[0006] According to a first aspect of an embodiment of the present invention, there is provided an on-chip wavelength adaptive distributed feedback structure, comprising an asymmetric chaotic structure, wherein a laser signal propagates along the cavity of the asymmetric chaotic structure by total reflection until the laser signal is completely absorbed in the cavity or does not meet the total reflection condition and is emitted from the outer wall of the cavity, and a scattered signal generated by the laser signal during the total reflection propagation process is transmitted back along the total reflection propagation path to the laser signal input port of the cavity; and the vector sum of the laser signal during the total reflection propagation process is not zero.

[0007] In an optional implementation, the cavity of the asymmetric chaotic structure is a vortex line structure, and the vortex line structure is a vortex line that satisfies the vortex line function: r=a+b*θ, wherein r is the circular radius, a is the initial radius of the corresponding vortex line, b is the radius change rate, and θ is the circular angle; the circular radius r of the vortex line gradually decreases from the outside to the inside, and the circular angle θ ranges from 0 to 360 degrees; the area enclosed by the vortex line constitutes the cavity; the gap in the cavity enclosed by the vortex line serves as the input port of the laser signal and the output port of the scattered signal; the propagation path of the laser signal in the cavity is a zigzag propagation.

[0008] In another optional implementation, it also includes a mode field conversion structure or a mode spot converter, which gradually expands the laser signal from a single-mode small mode field to a single-mode large mode field or a multi-mode mode field, and then injects it into the laser signal input port of the cavity; the mode spot converter adjusts the spot size of the laser signal, and then injects the laser signal with the adjusted spot into the laser signal input port of the cavity.

[0009] In another optional implementation, a scattering enhancement member is provided in the cavity of the asymmetric chaotic structure to enhance the scattering in the cavity, improve the randomness of the laser signal propagation in the cavity, and destroy possible resonance.

[0010] In another optional implementation, when the laser signal is totally reflected and propagated, the reflection angle of each total reflection is different, and as the number of reflections increases, the reflection angle gradually decreases until the laser signal is completely absorbed or the reflection angle is less than or equal to the critical angle of total reflection, that is, the total reflection condition is not met;

[0011] The scattered signal is transmitted back to the laser signal input port of the cavity along the total reflection propagation path. As the number of reflections increases, the reflection angle gradually increases until the scattered signal is output from the laser signal input port of the cavity.

[0012] In another optional implementation, the laser signal propagates non-resonantly in the cavity so that the cavity has wavelength adaptive characteristics.

[0013] In another optional implementation, the Q value of the cavity is adjusted by designing the difference between the inner and outer diameters of the vortex line in the vortex line structure.

[0014] In another optional implementation, the smaller the difference between the inner and outer diameters, the higher the Q value of the cavity and the stronger the resonance effect; the larger the difference between the inner and outer diameters, the lower the Q value of the cavity and the weaker the resonance effect; the higher the Q value of the cavity, the more scattered signals are cumulatively output from the cavity, and the lower the Q value of the cavity, the fewer scattered signals are cumulatively output from the cavity; the stronger the resonance effect, the weaker the wavelength adaptive characteristic of the cavity, and the weaker the resonance effect, the more significant the wavelength adaptive characteristic of the cavity.

[0015] In another optional implementation, the mode field conversion structure is a tapered waveguide geometric structure, and the scattering enhancement member is a scattering point or a linear scattering plane, and is close to the periphery of the cavity.

[0016] According to a second aspect of an embodiment of the present invention, there is provided a laser, characterized in that it comprises the above-mentioned on-chip wavelength adaptive distributed feedback structure.

[0017] The beneficial effects of the present invention are:

[0018] 1. The asymmetric chaotic structure of the present invention is an asymmetric structure. The sum of the propagation vectors of the laser signal in the asymmetric chaotic structure cavity is not zero, and the propagation vectors will not form a closed loop. The laser signal propagates non-resonantly in the cavity. Therefore, the cavity is not a resonant cavity and does not have a wavelength selection characteristic. The propagation path of any wavelength optical signal in the cavity is the same, and the cavity has a wavelength adaptive characteristic. In addition, the laser signal of the present invention propagates in the cavity by total reflection, and there is no additional loss introduced due to the rough outer wall of the waveguide, which can break through the Q value upper limit of the traditional cavity and make the propagation path of the laser signal in the cavity longer. The present invention does not have the output end of the traditional resonant cavity. The laser signal input port and the scattered signal output port of the cavity of the present invention are the same port, which can facilitate the input of the laser signal and the collection of the scattered signal.

[0019] 2. The present invention designs the cavity of the asymmetric chaotic structure so that the incident angle of the laser signal is continuously reduced during the total reflection propagation process, so that the laser signal can be gradually converged to the center of the cavity. At the same time, the reflection angle of the scattered signal is gradually increased, so that the scattered signal can gradually approach the outer wall of the cavity, which is convenient for the collection of the scattered signal. It can be seen that for the scattered signal generated in any direction, as long as it is reversely transmitted and meets the total reflection condition at the beginning, it will gradually approach the outer wall of the cavity during the reverse propagation process, which is conducive to the collection of the scattered signal.

[0020] 3. The present invention converts the laser signal into light components propagating in different directions by setting a mode field conversion structure, so that each light component is incident on different positions of the asymmetric chaotic structure cavity, which can improve the scattering intensity, further ensure that the sum of the propagation vectors of the laser signal in the asymmetric chaotic structure cavity is not zero, and facilitate the collection of scattered signals;

[0021] 4. The present invention adds a scattering enhancement member to further improve the scattering intensity, and at the same time further improve the chaotic characteristics of the cavity, reducing the possible resonance wavelength or resonance loop;

[0022] 5. The present invention can adjust the Q value and resonance effect of the cavity by designing the difference between the inner and outer diameters of the vortex line in the vortex line structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of an embodiment of the on-chip wavelength adaptive distributed feedback structure of the present invention;

[0024] Figure 2 Schematic diagram of laser signal propagation vectors of a conventional circular cavity and the cavity of the present invention;

[0025] Figure 3 It is a schematic structural diagram of another embodiment of the on-chip wavelength adaptive distributed feedback structure of the present invention;

[0026] Figure 4 is a structural stereogram of another embodiment of the on-chip wavelength adaptive distributed feedback structure of the present invention;

[0027] Figure 5 This is a simulation diagram of laser signal propagation in the cavity of the on-chip wavelength adaptive distributed feedback structure of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0029] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0030] See also Figure 1 , is a schematic diagram of an embodiment of the on-chip wavelength adaptive distributed feedback structure of the present invention. Figure 2As shown, the distributed feedback structure may include an asymmetric chaotic structure 1, and the laser signal propagates along the cavity of the asymmetric chaotic structure 1 by total reflection until the laser signal is completely absorbed in the cavity or does not meet the total reflection condition and is emitted from the outer wall of the cavity. The scattered signal generated by the laser signal during the total reflection propagation process is transmitted back to the laser signal input port of the cavity along the total reflection propagation path; the vector sum of the laser signal during the total reflection propagation process is not zero.

[0031] In this embodiment, the cavity is an asymmetric chaotic structure, and the cavity is provided with an optical signal input and output port, wherein the laser signal input port and the scattered signal output port are the same port. In one example, the cavity of the asymmetric chaotic structure can be a vortex line structure, and the vortex line structure is a vortex line, and the vortex line satisfies the vortex line function: r = a + b * θ, wherein r is the circumferential radius, a is the initial radius of the corresponding vortex line, b is the radius change rate and is a negative number, and θ is the circumferential angle, and its value range is 0 to 360 degrees; the vortex lines are located on the same plane, so that the cavity is a two-dimensional vortex cavity, and the circumferential radius r of the vortex line from the outside to the inside can be gradually reduced, and the area surrounded by the vortex line constitutes the cavity; the gap of the cavity surrounded by the vortex line serves as the input port of the laser and the output port of the feedback signal. The propagation path of the laser signal in the cavity is a broken line propagation.

[0032] When the laser signal is totally reflected and propagated, the reflection angle of each total reflection is different, and as the number of reflections increases, the reflection angle gradually decreases until the laser signal is completely absorbed or the reflection angle is less than or equal to the critical angle of total reflection, that is, the total reflection condition is not met; the scattered signal is transmitted back to the laser signal input port of the cavity along the total reflection propagation path, and as the number of reflections increases, the reflection angle gradually increases until the scattered signal is output from the laser signal input port of the cavity. The present invention designs the cavity of the asymmetric chaotic structure so that the incident angle of the laser signal is continuously reduced during the total reflection propagation process, so that the laser signal can gradually converge to the center of the cavity, and at the same time, the reflection angle of the scattered signal gradually increases, so that the scattered signal can gradually approach the outer wall of the cavity, which is convenient for the collection of the scattered signal; it can be seen that for the scattered signal generated in any direction, as long as it is reversely transmitted and meets the total reflection condition at the beginning, it will gradually approach the outer wall of the cavity during the reverse propagation process, which is conducive to the collection of the scattered signal.

[0033] like Figure 2As shown, the laser signal forms a closed loop during propagation in a traditional circular cavity, and the sum of the propagation vectors is 0; however, the laser signal does not form a closed loop when propagating in the cavity of the present invention, and the sum of the propagation vectors is not 0. The laser signal will not resonate in the cavity, and the propagation path of the laser signal in the cavity is the same for laser signals of all wavelengths. Since the laser signal propagates non-resonantly in the cavity of the present invention, the cavity of the present invention has a wavelength adaptive characteristic.

[0034] It can be seen from the above embodiments that the asymmetric chaotic structure of the present invention is an asymmetric structure, the sum of the propagation vectors of the laser signal in the asymmetric chaotic structure cavity is not zero, the propagation vector will not form a closed loop, and the laser signal is propagated non-resonantly in the cavity. Therefore, the cavity is not a resonant cavity, and there is no wavelength selection characteristic. The propagation path of any wavelength light signal in the cavity is the same, and the cavity has a wavelength adaptive characteristic; in addition, the laser signal of the present invention is fully reflected and propagated in the cavity, and there is no additional loss introduced due to the rough outer wall of the waveguide, which can break through the Q value upper limit of the traditional cavity and make the propagation path of the laser signal in the cavity longer; the present invention does not have the output end of the traditional resonant cavity, and the laser signal input port and the scattered signal output port of the cavity of the present invention are the same port, which can facilitate the input of the laser signal and the collection of the scattered signal.

[0035] Combination Figures 3 to 5 As shown, Figure 3 and Figure 1 The difference of the on-chip wavelength adaptive distributed feedback structure shown is that Figure 3 The illustrated embodiment may also include a mode field conversion structure or a mode spot converter 2, wherein the mode field conversion structure gradually expands the laser signal from a single-mode small mode field to a single-mode large mode field or a multi-mode mode field, and then injects it into the laser signal input port of the cavity, at which time each light component in the laser signal is incident on different positions of the cavity; the mode spot converter adjusts the spot size of the laser signal, and then injects the laser signal with the adjusted spot into the laser signal input port of the cavity, at which time each light component in the laser signal is incident on different positions of the cavity. In addition, Figure 3 A scattering enhancement member 3 may also be provided in the cavity of the asymmetric chaotic structure to enhance the scattering in the cavity, improve the randomness of the laser signal propagation in the cavity, and destroy possible resonance. The mode field conversion structure may be a tapered waveguide geometric structure, and the scattering enhancement member may be a scattering point or a linear scattering plane, and is close to the periphery of the cavity.

[0036] The present invention converts the laser signal into light components propagating in different directions by setting a mode field conversion structure, so that each light component is incident on different positions of the asymmetric chaotic structure cavity, thereby improving the scattering intensity, further ensuring that the sum of the propagation vectors of the laser signal in the asymmetric chaotic structure cavity is not zero, and facilitating the collection of scattered signals. The present invention adds a scattering enhancement component, which can further improve the scattering intensity, further improve the chaotic characteristics of the cavity, and reduce possible resonant wavelengths or resonant circuits.

[0037] The present invention can adjust the Q value of the cavity by designing the difference between the inner and outer diameters of the vortex line in the vortex line structure, and adjusts the Q value of the cavity by adjusting the b value in the vortex function. The smaller the difference between the inner and outer diameters, the longer the propagation path of the laser signal when occupying the same space, the higher the Q value of the cavity, and the stronger the resonance effect; the larger the difference between the inner and outer diameters, the shorter the propagation path of the laser signal when occupying the same space, the lower the Q value of the cavity, and the weaker the resonance effect; the higher the Q value of the cavity, the more scattered signals are cumulatively output from the cavity, and the lower the Q value of the cavity, the fewer scattered signals are cumulatively output from the cavity; the stronger the resonance effect, the weaker the wavelength adaptive characteristics of the cavity, and the weaker the resonance effect, the more significant the wavelength adaptive characteristics of the cavity. The present invention can adjust the Q value and resonance effect of the cavity by designing the difference between the inner and outer diameters of the vortex line in the vortex line structure.

[0038] In addition, if Figure 5 As shown, the cavity can be etched on the silicon photonic chip by photolithography to form a vortex cavity structure. The substrate is generally made of silicon dioxide, and the cavity can be made of common semiconductor materials such as silicon, silicon nitride, and lithium niobate. After etching, the chip surface will be covered with an oxide layer to protect the cavity.

[0039] It can be seen from the above embodiments that the asymmetric chaotic structure of the present invention is an asymmetric structure, the sum of the propagation vectors of the laser signal in the asymmetric chaotic structure cavity is not zero, the propagation vector will not form a closed loop, and the laser signal is propagated non-resonantly in the cavity. Therefore, the cavity is not a resonant cavity, and there is no wavelength selection characteristic. The propagation path of any wavelength light signal in the cavity is the same, and the cavity has a wavelength adaptive characteristic; in addition, the laser signal of the present invention is fully reflected and propagated in the cavity, and there is no additional loss introduced due to the rough outer wall of the waveguide, which can break through the Q value upper limit of the traditional cavity and make the propagation path of the laser signal in the cavity longer; the present invention does not have the output end of the traditional resonant cavity, and the laser signal input port and the scattered signal output port of the cavity of the present invention are the same port, which can facilitate the input of the laser signal and the collection of the scattered signal.

[0040] In addition, the present invention also provides a laser, which may include the above-mentioned on-chip wavelength adaptive distributed feedback structure.

[0041] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0042] It will be appreciated that the invention is not limited to the precise construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from its scope. The scope of the invention is governed solely by the appended claims.

Claims

1. An on-chip wavelength adaptive distributed feedback structure, characterized in that: The invention comprises an asymmetric chaotic structure, wherein a laser signal is totally reflected and propagated along a cavity of the asymmetric chaotic structure until the laser signal is completely absorbed in the cavity or does not meet the total reflection condition and is emitted from the outer wall of the cavity, and a scattered signal generated by the laser signal during the total reflection propagation process is reversely transmitted along the total reflection propagation path back to the laser signal input port of the cavity; and the vector sum of the laser signal during the total reflection propagation process is not zero.

2. The on-chip wavelength adaptive distributed feedback structure according to claim 1, characterized in that: The cavity of the asymmetric chaotic structure is a vortex line structure, and the vortex line structure is a vortex line. The vortex line satisfies the vortex line function: r=a+b*θ, wherein r is the circumferential radius, a is the initial radius of the corresponding vortex line, b is the radius change rate, and θ is the circumferential angle; the circumferential radius r of the vortex line gradually decreases from the outside to the inside, and the range of the circumferential angle θ is 0 to 360 degrees; the area enclosed by the vortex line constitutes the cavity; the notch of the cavity enclosed by the vortex line serves as the input port of the laser signal and the output port of the scattered signal; the propagation path of the laser signal in the cavity is a zigzag propagation.

3. The on-chip wavelength adaptive distributed feedback structure according to claim 1 or 2, characterized in that: It also includes a mode field conversion structure or a mode spot converter, which gradually expands the laser signal from a single-mode small mode field to a single-mode large mode field or a multi-mode mode field, and then injects it into the laser signal input port of the cavity; the mode spot converter adjusts the spot size of the laser signal, and then injects the laser signal with the adjusted spot into the laser signal input port of the cavity.

4. The on-chip wavelength adaptive distributed feedback structure according to claim 3, characterized in that: A scattering enhancement member is provided in the cavity of the asymmetric chaotic structure to enhance the scattering in the cavity, improve the randomness of the laser signal propagation in the cavity, and destroy possible resonance.

5. The on-chip wavelength adaptive distributed feedback structure according to claim 1 or 2, characterized in that: When the laser signal is totally reflected and propagated, the reflection angle of each total reflection is different, and as the number of reflections increases, the reflection angle gradually decreases until the laser signal is completely absorbed or the reflection angle is less than or equal to the critical angle of total reflection, that is, the total reflection condition is not met; The scattered signal is transmitted back to the laser signal input port of the cavity along the total reflection propagation path. As the number of reflections increases, the reflection angle gradually increases until the scattered signal is output from the laser signal input port of the cavity.

6. The on-chip wavelength adaptive distributed feedback structure according to claim 1, characterized in that: The laser signal propagates non-resonantly in the cavity, so that the cavity has wavelength adaptive characteristics.

7. The on-chip wavelength adaptive distributed feedback structure according to claim 2, characterized in that: The Q value of the cavity is adjusted by designing the difference between the inner and outer diameters of the vortex line in the vortex line structure.

8. The on-chip wavelength adaptive distributed feedback structure according to claim 7, characterized in that: The smaller the difference between the inner and outer diameters, the higher the Q value of the cavity and the stronger the resonance effect; the larger the difference between the inner and outer diameters, the lower the Q value of the cavity and the weaker the resonance effect; the higher the Q value of the cavity, the more scattering signals are cumulatively output from the cavity, and the lower the Q value of the cavity, the fewer scattering signals are cumulatively output from the cavity; the stronger the resonance effect, the weaker the wavelength adaptive characteristics of the cavity, and the weaker the resonance effect, the more significant the wavelength adaptive characteristics of the cavity.

9. The on-chip wavelength adaptive distributed feedback structure according to claim 4, characterized in that: The mode field conversion structure is a tapered waveguide geometric structure, and the scattering enhancement component is a scattering point or a linear scattering plane, and is close to the periphery of the cavity.

10. A laser, characterized in that: The invention comprises an on-chip wavelength adaptive distributed feedback structure as claimed in any one of claims 1 to 9.

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