Multi-wavelength Laser Based on PTX Symmetric Dielectric

Abstract

The present invention relates to a multi-wavelength laser based on a PTX symmetric dielectric, comprising a dielectric structure formed by butting dielectric sheets A and B, and the dielectric structure satisfies #imgabs0#n ar =n br ; #imgabs1#G is the scale transformation coefficient, and the thickness of A is d a , the thickness of B is d b , n ar and n br are the real parts of the refractive indices of A and B, respectively, n ai and n bi are the imaginary parts of the refractive indices of A and B, respectively; the dielectric structure supports multi-wavelength laser points, which correspond to the maximum points of transmittance and reflectivity. The wavelength of the multi-wavelength laser can be controlled by varying the angle of incidence. The PTX symmetrical dielectric structure of the present invention is simple, shortens the scale of the gain medium, and is easy to implement in practice, thereby obtaining a more ideal multi-wavelength laser. The multi-wavelength laser can flexibly control the wavelength by varying the angle of incidence.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-wavelength lasers, and in particular relates to a multi-wavelength laser based on a PTX symmetric dielectric. Background Art

[0002] Since the invention of the laser in the 1960s, the development and application of lasers have made significant progress. Lasers are widely used in communications, medicine, military, and scientific experiments, and have led the way in the advancement of an entire era. Initially, Fabry-Perler cavity resonance was used to achieve optical excitation, and later semiconductors and optical fibers were used to realize multi-wavelength and wavelength-tunable lasers. Multi-wavelength tunable lasers are required in communication systems, especially wavelength division multiplexing (WDM). Traditional multi-wavelength lasers are complex in structure and difficult to operate at room temperature.

[0003] With the development of non-Hermitian optics, PT-symmetric aperiodic photonic crystals can be used to realize multi-wavelength lasers. For example, the PT-symmetric Cantor photonic crystal structure for achieving coherent perfect absorption laser points disclosed in invention patent application number 202111234193.3 requires that the scales of the gain medium and the loss medium are exactly the same. However, due to the difficulty of achieving optical gain over a large scale, the PT-symmetric Cantor photonic crystal structure is difficult to realize in practice. Summary of the Invention

[0004] In order to improve the defect that PT-symmetric non-periodic photonic crystals excited by multi-wavelength lasers are difficult to implement in practice due to the difficulty of optical gain control over a large scale, the present invention provides a multi-wavelength laser based on PTX-symmetric dielectrics, which has a simple structure, shortens the scale of the gain medium, and is easy to implement in practice.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] The multi-wavelength laser based on PTX symmetric dielectric includes a dielectric structure formed by connecting two dielectric sheets A and B with different refractive indices, and the dielectric structure satisfies n ar =n br ; Where G is the scale transformation coefficient, the thickness of the dielectric sheet A is d a , the thickness of dielectric sheet B is d b , n ar and n br are the real parts of the refractive index of dielectric sheet A and dielectric sheet B, respectively, n ai and n bi are the imaginary parts of the refractive index of dielectric sheet A and the imaginary parts of the refractive index of dielectric sheet B respectively;

[0007] The dielectric structure supports multi-wavelength laser points, the multi-wavelength laser points correspond to maximum points of transmittance and reflectance, and the wavelengths corresponding to the multi-wavelength laser points are adjustable.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the wavelength of the multi-wavelength laser can be controlled by changing the size of the incident angle.

[0010] Furthermore, the matrix materials of the dielectric sheet A and the dielectric sheet B are both lithium niobate.

[0011] Furthermore, the optical loss of the dielectric sheet A is reduced by chemically doping aluminum ions Al 3+ The optical gain of the dielectric sheet B is achieved by chemically doping erbium ions Er 3+ And it is achieved by using external optical pumping.

[0012] Furthermore, the real part of the refractive index n of the dielectric sheet A and the dielectric sheet B is ar =n br =2.22, the imaginary part of the refractive index of the dielectric sheet A is n ai = 0.01*q, imaginary part of the refractive index n of the dielectric sheet B bi =-0.1*q, where q is the gain-loss factor.

[0013] Furthermore, the thickness d of the dielectric sheet A is a =5 μm (micrometer), the thickness d of the dielectric sheet B b =0.5μm, and the scale conversion coefficient G=10.

[0014] The beneficial effects of the present invention are: compared with the PT-symmetric non-periodic photonic crystal that can realize multi-wavelength laser excitation, the dielectric structure of the present invention is simple, the scale of the gain medium is shortened, and it is easy to implement in practice, thereby obtaining a more ideal multi-wavelength laser. The multi-wavelength laser can flexibly control the wavelength by changing the size of the incident angle. Specifically, a dielectric structure is formed by docking two dielectric sheets A and dielectric sheets B with different refractive indices, and by adjusting the thickness, optical loss and gain of dielectric sheets A and dielectric sheets B, the entire dielectric structure satisfies PTX symmetry, that is, satisfies n ar =n br ; The dielectric structure supports multi-wavelength laser points, which correspond to the maximum values of transmittance and reflectivity. The wavelengths corresponding to the multi-wavelength laser points can then be flexibly controlled by the angle of incidence, thereby adjusting the wavelength of the multi-wavelength laser by changing the angle of incidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of the PTX symmetric dielectric in the multi-wavelength laser of Example 1 of the present invention.

[0016] Figure 2 (a) is the transmittance of light waves in the parameter space consisting of the gain-loss factor and the wavelength of the incident light according to Example 2 of the present invention; Figure 2 (b) is the transmission spectrum corresponding to the gain-loss factor q=6.8168 of Example 2 of the present invention, and the incident angle is θ=0°.

[0017] Figure 3 (a) is the reflectivity of the light wave in the parameter space consisting of the gain-loss factor and the wavelength of the incident light according to Example 2 of the present invention; Figure 3 (b) is the reflection spectrum corresponding to the gain-loss factor q=6.8168 of Example 2 of the present invention, and the incident angle is θ=0°.

[0018] Figure 4 (a) is the transmittance near the laser point LP4 corresponding to the incident angle θ=10° in Example 3 of the present invention; Figure 4 (b) is the transmittance near the laser point LP4 corresponding to the incident angle θ=30° in Example 3 of the present invention; Figure 4 (c) is the transmittance near the laser point LP4 corresponding to the incident angle θ=50° in Example 3 of the present invention; Figure 4 (d) shows the relationship between the position of the laser point LP4 in the parameter space and the incident angle according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0019] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0020] Unless otherwise noted, the raw materials used in this invention are conventional in the art and are commercially available. The experimental methods and detection methods in the following examples are conventional methods unless otherwise noted, and the instruments and equipment used in the experiments are commercially available. Any portions not described in detail in this specification belong to the prior art.

[0021] When there is gain and loss in the system, the system is non-Hermitian. Non-Hermitian systems can induce many exotic optical effects, such as one-way invisibility, singular points, electric field localization, and coherent perfect absorption lasers. When the refractive index of the material of a non-Hermitian optical system satisfies n(r) = n(-r), where r is the spatial position coordinate, the system follows parity-time symmetry (PT symmetry). In practice, it is necessary to simultaneously control the real and imaginary parts of the refractive index of the material so that it satisfies the even symmetry of the real part of the refractive index and the odd symmetry of the imaginary part of the refractive index.

[0022] When the imaginary part of the refractive index is positive, it indicates optical loss; when it is negative, it indicates optical gain. Optical loss can be achieved by doping with metal ions, while gain can be achieved through two-wave mixing or by doping with erbium ions and then pumping with pump light to achieve optical gain.

[0023] However, in the PT symmetric system, the size range of optical gain and the size range of optical loss are equal. Optical loss can be easily doped and regulated in a large size range, but optical gain can generally only be controlled within a smaller range. The PTX (parity-time-reciprocal scaling) symmetric system adds the reciprocal symmetry of the spatial scale on the basis of PT symmetry, which can reduce the size of the optical gain to 1 / G (G>1) of the optical loss size, but at the same time, the optical gain coefficient is G times the optical loss coefficient. Its essence is to use energy intensity in exchange for spatial scale. Based on this, the inventors considered docking two different dielectrics, reducing the spatial size of the gain medium at the cost of increasing its gain coefficient, regulating its refractive index and making it satisfy PTX symmetry, thereby realizing multi-wavelength laser resonance. And by changing the size of the incident angle, the wavelength of the corresponding laser can be controlled.

[0024] The following are examples of the present invention.

[0025] Example 1

[0026] Figure 1 This figure shows the structure of the PTX-symmetric dielectric used in the multi-wavelength laser of this embodiment. The dielectric structure is formed by butting together two dielectric sheets A and B with different refractive indices. The thickness, optical loss, and gain of dielectric sheets A and B are then adjusted to ensure that the entire dielectric structure exhibits PTX symmetry.

[0027] That is, in one-dimensional direction (here taking the horizontal direction as an example), the PTX symmetric dielectric structure satisfies n ar =n br ; Where G is the scale transformation coefficient, the thickness of the sheet A is d a , the thickness of sheet B is d b , n ar and n br are the real parts of the refractive index of dielectric sheet A and dielectric sheet B, respectively, n ai and n bi are the imaginary parts of the refractive index of dielectric sheet A and the imaginary parts of the refractive index of dielectric sheet B, respectively.

[0028] The refractive index of dielectric sheet A is n a =n ar +i*n ai , the refractive index of dielectric sheet B is n b =n br +i*n bi , where i represents the imaginary unit. Symbol I i Represents the incident light, I r Represents reflected light, I t Represents transmitted light.

[0029] In this embodiment, the matrix materials of the thin sheets A and B of the PTX symmetric dielectric structure are both lithium niobate (LiNbO3); aluminum ions (Al2O3) are doped into the thin sheet A by chemical vapor deposition. 3+ ), achieving weak loss, and controlling the optical loss coefficient of sheet A by controlling the doped aluminum ions; Erbium ions (Er 3+ ), and gain is achieved through external pump light, and the optical gain coefficient of the thin film B is controlled by the intensity of the pump light. For the lithium niobate matrix material, the real part of the refractive index is n ar =n br =2.22, the imaginary parts are n ai =0.01*q and n bi =-0.1*q, where q is the gain-loss factor. The thickness of sheet A is d a =5μm, the thickness of the sheet B is d b = 0.5 μm, so the scale transformation factor is G = 10. In this way, in the horizontal direction, the entire structure satisfies the one-dimensional PTX symmetry.

[0030] Example 2

[0031] The PTX symmetrical dielectric structure obtained in Example 1 was used for the experiment. The incident light was a transverse magnetic wave or a transverse electric wave, and the incident angle was θ=0°. Figure 2 (a) shows the transmittance of light waves in the parameter space composed of the gain-loss factor and the wavelength of the incident light. In order to increase the contrast, the transmittance T is logarithmized. 10(T) operation. It can be seen that within the range of incident wavelength λ [0.5μm, 2μm] and the range of gain-loss factor q [0, 10], there are four transmission maximum points, namely laser points, which are denoted as LP1, LP2, LP3 and LP4 respectively. Their transmittances are log 10 (T1) = 3.8222, log 10 (T2) = 4.433, log 10 (T3) = 4.6194 and log 10 The parameters corresponding to these four laser points are LP1 (λ1 = 0.5198, q1 = 2.8529), LP2 (λ2 = 0.6785, q2 = 3.4835), LP3 (λ3 = 0.9765, q3 = 4.5646), and LP4 (λ4 = 1.7393, q4 = 6.8168).

[0032] Figure 2 (b) shows the transmission spectrum corresponding to the gain-loss factor q = 6.8168. The value q = 6.8168 is exactly the gain-loss factor corresponding to the laser point LP4. It can be seen that the transmittance changes with the change of the incident wavelength; there is a transmission peak at λ = 1.7393 = λ4, marked with a ☆, and the transmittance at this point is log 10 (T) = 5.9903 = log 10 (T4) is the transmittance corresponding to the laser point LP4.

[0033] Figure 3 (a) shows the reflectivity of light waves in the parameter space composed of the gain-loss factor and the wavelength of the incident light. In order to increase the contrast, the reflectivity R is logarithmized. 10 (R) operation. It can be seen that within the range of the parameter space, the reflectivity is extremely high at the four laser points LP1, LP2, LP3 and LP4. Their reflectivity is log 10 (R1)=3.0023、log 10 (R2)=3.618, log 10 (R3) = 3.8349 and log 10 (R4)=5.2617.

[0034] Figure 3 (b) shows the reflection spectrum corresponding to the gain-loss factor q = 6.8168. As mentioned above, the value q = 6.8168 is exactly the gain-loss factor corresponding to the laser point LP4. It can be seen that the reflectivity changes with the change of the incident wavelength; there is a reflection peak at λ = 1.7393 = λ4, marked with a ☆, and the reflectivity at this point is log10 (R) = 5.2617 = log 10 (R4) is the reflectivity corresponding to the laser point LP4.

[0035] Example 3

[0036] Based on Example 2, experiments were continued using the PTX symmetric dielectric structure obtained in Example 1. Other parameters remained unchanged. Changing the incident angle of the lightwave altered the position of the corresponding laser point in parameter space, which in turn changed the corresponding laser wavelength. When the lightwave is incident at an angle, the polarization direction of the lightwave needs to be considered, so a transverse magnetic wave is used as an example.

[0037] Figure 4 (a) shows the transmittance near the laser point LP4 when the incident angle θ = 10°. The position of LP4 is (λ4 = 1.7337, q4 = 6.8368). Figure 4 (b) shows the transmittance near the laser point LP4 when the incident angle θ = 30°. The position of LP4 is (λ4 = 1.691, q4 = 6.997). Figure 4 (c) shows the transmittance near the laser point LP4 when the incident angle θ = 50°. The position of LP4 is (λ4 = 1.6003, q4 = 7.5576).

[0038] Figure 4 Figure (d) shows how the position of laser point LP4 in parameter space changes with the incident angle. As can be seen, as the incident angle increases, LP4's position in parameter space shifts to the upper left, meaning the corresponding laser wavelength decreases and the gain-loss factor increases. Similarly, the wavelengths corresponding to the other laser points LP1, LP2, and LP3 also change with the incident angle. Changing the incident angle of the light wave changes the position of the corresponding laser point in parameter space, meaning the corresponding laser wavelength changes. Therefore, the laser wavelength can be flexibly controlled by varying the incident angle.

[0039] In summary, the present invention connects two dielectric sheets A and B with different refractive indices, and makes the entire dielectric structure meet PTX symmetry by adjusting the thickness, optical loss and gain of dielectric sheets A and B. The matrix materials of the PTX symmetric dielectric structure are both lithium niobate, and the optical loss of dielectric sheet A is controlled by chemically doping aluminum ions Al 3+ The optical gain of dielectric sheet B is achieved by chemically doping erbium ions Er 3+This is achieved by external light pumping. In the parameter space composed of the gain-loss factor and the wavelength of the incident light, the PTX symmetric dielectric structure supports multi-wavelength laser points, and the multi-wavelength laser points correspond to the maximum points of transmittance and reflectivity, thereby obtaining a more ideal multi-wavelength laser. The wavelengths corresponding to the multi-wavelength laser points of the multi-wavelength laser can be flexibly controlled by the size of the incident angle. Compared with the PT-symmetric non-periodic photonic crystal that can achieve multi-wavelength laser excitation, the PTX symmetric dielectric structure described in the present invention is simple, shortens the scale of the gain medium, and is easy to implement in practice.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Multi-wavelength laser based on PTX symmetric dielectric, characterized by: A dielectric structure is formed by connecting two dielectric sheets A and B with different refractive indices, and the dielectric structure satisfies n ar =n br ; Where G is the scale transformation coefficient, the thickness of the dielectric sheet A is d a , the thickness of dielectric sheet B is d b , n ar and n br are the real parts of the refractive index of dielectric sheet A and dielectric sheet B, respectively, n ai and n bi are the imaginary parts of the refractive index of dielectric sheet A and the imaginary parts of the refractive index of dielectric sheet B respectively; The dielectric structure supports multi-wavelength laser points, the multi-wavelength laser points correspond to maximum points of transmittance and reflectance, and the wavelengths corresponding to the multi-wavelength laser points are adjustable.

2. The multi-wavelength laser according to claim 1, wherein The wavelength of the multi-wavelength laser can be controlled by changing the incident angle.

3. The multi-wavelength laser according to claim 1, wherein The matrix materials of the dielectric sheet A and the dielectric sheet B are both lithium niobate.

4. The multi-wavelength laser according to claim 3, characterized in that The optical loss of the dielectric sheet A is reduced by chemically doping with aluminum ions Al 3+ The optical gain of the dielectric sheet B is achieved by chemically doping erbium ions Er 3+ And it is achieved by using external optical pumping.

5. The multi-wavelength laser according to claim 3, wherein: The real part of the refractive index n of the dielectric sheet A and the dielectric sheet B is ar =n br =2.22, the imaginary part of the refractive index of the dielectric sheet A is n ai = 0.01*q, imaginary part of the refractive index n of the dielectric sheet B bi =-0.1*q, where q is the gain-loss factor.

6. The multi-wavelength laser according to claim 3, wherein: The thickness d of the dielectric sheet A a =5μm, the thickness d of the dielectric sheet B b =0.5μm, and the scale conversion coefficient G=10.

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