Off-axis pumping 1.5-1.6 [mu] m solid vortex laser and application thereof

Abstract

The invention discloses an off-axis pumping 1.5-1.6 [mu] m solid vortex laser and application thereof, and belongs to the technical field of laser devices. Comprising a pumping source, a coupling lens group, an input mirror, a gain medium, an output mirror and an astigmatism mode converter which are arranged in sequence, according to the solid vortex laser, an Er < 3 + > / Yb < 3 + > double-doped crystal is used as a gain medium, a high-order Laguerre-Gaussian beam with the wave band of 1.5-1.6 [mu] m is generated by adopting a technology of combining off-axis pumping and an astigmatism mode converter, and then the high-order Laguerre-Gaussian beam with the adjustable broadband wavelength of the wave band is realized through a wavelength tuning technology. And specific scene requirements in the fields of laser communication, optical detection and the like are benchmarked.

Description

TECHNICAL FIELD

[0001] The application relates to an off-axis pumped 1.5-1.6 mu m solid vortex laser and application thereof, and belongs to the technical field of laser devices. BACKGROUND

[0002] The 1.5-1.6 mu m band solid vortex laser not only has a unique light field and phase distribution, but also has the advantages of low fiber transmission loss, eye safety and low cost, and has important application value in the fields of optical tweezers, rotating body detection, micro-nano processing and optical communication. In addition, the 1.5-1.6 mu m band wideband wavelength adjustable solid vortex laser can improve the channel capacity and spectral efficiency of the optical communication system, and is conducive to realizing large-capacity optical communication. At present, the related researches at home and abroad all use Er 3+ / Yb 3+ doped phosphate glass or Er 3+ doped laser crystal as the gain medium to realize the solid vortex laser of the band, and there is no report on the realization of the solid vortex laser of the band by using Er 3+ / Yb 3+ doped laser crystal. Er 3+ / Yb 3+ doped phosphate glass is limited by low thermal conductivity, and has low continuous laser output power. At present, the vortex laser mode order realized is low, and the highest is only first-order Laguerre-Gaussian beam. The existing Er 3+ doped laser crystal is limited by narrow gain bandwidth, and has small wavelength tuning range. At present, only the wavelength tunable vortex laser output of LG 0,1 mode with a tuning bandwidth of 6.8 nm and LG 0,2 mode with a tuning bandwidth of 4.9 nm has been realized. Meanwhile, the wavelength tuning range of the vortex laser of the existing Er 3+ doped laser crystal is mostly around 1.64 mu m, which is not the most ideal optical communication band. SUMMARY

[0003] In order to solve the problems that the existing technology of the 1.5-1.6 mu m band solid vortex laser cannot realize high-order vortex light output and wideband wavelength tuning, the application provides a technical scheme of an off-axis pumped 1.5-1.6 mu m solid vortex laser. Er 3+ / Yb 3+ doped crystal is used as the gain medium, and the off-axis pumping and astigmatism mode converter are combined, so that the new gain medium is used to realize the wideband wavelength tuning and high-order vortex light output, and the development of large-capacity optical communication is promoted.

[0004] The application adopts the following technical scheme: According to a first aspect of this application, an off-axis pumped 1.5-1.6 μm solid-state vortex laser is provided, comprising: Pump source, coupling lens group, input mirror, gain medium, output mirror and astigmatic mode converter; The pump source is a semiconductor laser capable of generating laser light in the 910-990nm wavelength range; The coupling lens group is used to focus the pump laser onto the gain medium; The gain medium is Er 3+ / Yb 3+ Double-doped laser crystal; The output mirror is used to adjust the offset between the laser beam and the pump beam in the gain medium, so as to realize off-axis pumping to generate Hermitian-Gaussian beams. The astigmatic mode converter is used to convert the Hermite-Gaussian beam into a Laguerre-Gaussian beam.

[0005] Optionally, the gain medium is Er 3+ / Yb 3+ Double-borate laser crystal, Er 3+ / Yb 3+ Double-doped silicate laser crystal or Er 3+ / Yb 3+ One type of double-doped phosphate laser crystal.

[0006] Optionally, the crystal is RAl3(BO3)4 or RMgB5O. 10 , Lu2Si2O7, Sc2Si2O7, Ca3NbGa3Si2O 14 One of RPO4, RM3(PO4)3; Where R is one or more of the elements Y, Gd, and Lu, and M is one or more of the elements Ca, Sr, and Ba.

[0007] Optionally, the input mirror has a transmittance greater than 90% in the 910-990nm band and a reflectance greater than 99.5% in the 1.5-1.6μm band.

[0008] Optionally, the transmittance of the output mirror in the 1.5-1.6μm band is 0.5-15%.

[0009] Optionally, the output mirror is mounted on a displacement stage; The displacement stage drives the output mirror to move laterally or longitudinally along a direction perpendicular to the optical path to adjust the offset between the laser beam and the pump beam in the gain medium, so as to realize the generation of Hermite-Gaussian beam.

[0010] Optionally, the astigmatic mode converter can convert the generated Hermite-Gaussian beam into a Laguerre-Gaussian beam of the corresponding order.

[0011] Optionally, the astigmatic mode converter includes a convex lens and a cylindrical lens arranged sequentially; The convex lens is used to shape the Hermitian-Gaussian beam generated by off-axis pumping, so that the Rayleigh length of the beam is equal to the focal length of the cylindrical lens. The focal point of the cylindrical lens coincides with the waist of the shaped Hermetic-Gaussian beam.

[0012] Optionally, the astigmatic mode converter includes a convex lens, a first cylindrical lens, and a second cylindrical lens arranged sequentially. The convex lens is used to shape the Hermitian-Gaussian beam generated by off-axis pumping, so that the Rayleigh length of the beam is (1+2) times the focal length of the cylindrical lens. 1 / 2 / 2) times; The first cylindrical lens and the second cylindrical lens have the same focal length and the distance between them is 2 times the focal length. 1 / 2 times.

[0013] Optionally, the astigmatic mode converter is mounted on a rotating stage; The astigmatic mode converter has a rotatable range of -45° to 45° along the direction perpendicular to the beam propagation, which is used to change the chirality of the orbital angular momentum of the Laguerre-Gaussian beam.

[0014] Optionally, a wavelength tuning element may also be included between the gain medium and the output mirror.

[0015] Optionally, the wavelength tuning element is one of a SiO2 birefringent filter, a Bragg grating, or a Fabry-Perot etalon.

[0016] According to a second aspect of this application, an off-axis pumped 1.5-1.6μm solid-state vortex laser as described above is provided for laser communication and optical detection applications.

[0017] The beneficial effects of this application include: (1) Relative to Er 3+ / Yb 3+ Double-doped phosphate glass, Er of this application 3+ / Yb 3+ Double-doped crystals possess both high thermal conductivity and large absorption and emission cross sections, as well as Yb 3+ →Er 3+ It has advantages such as high energy transfer efficiency and low upconversion loss. This application utilizes Er 3+ / Yb 3+ Using dual-doped crystals as gain media can enable solid-state vortex lasers in the 1.5-1.6μm band with higher output power and higher mode order.

[0018] (2) Compared to the existing Er 3+ Single-doped crystals, such as Er:YAG and Er:YVO4, are used in this application. 3+ / Yb 3+ Double-doped crystals have a wider gain band in the 1.5-1.6μm band, enabling the realization of solid-state vortex lasers in the 1.5-1.6μm band with a wider tunable wavelength range, and the tunable wavelength range is within the low-loss window of fiber transmission.

[0019] (3) Compared with other methods such as spatial light modulators, vortex phase plates and metasurfaces, the combination of off-axis pumping and astigmatic mode converter can directly change the overlap between the laser beam and the pump beam, thereby generating higher-order vortex lasers of different orders more efficiently and flexibly. At the same time, by rotating the astigmatic mode converter perpendicular to the direction of light propagation, the orbital angular momentum state of the vortex laser can also be extended. Attached Figure Description

[0020] Figure 1 A schematic diagram of an off-axis pumped 1.5-1.6μm solid-state vortex laser structure provided for an embodiment of this application, wherein 1-pump source, 2-coupled lens group, 3-input mirror, 4-gain medium, 5-output mirror, and 6-astigmatic mode converter; Figure 2 The relationship between the offset of different pump beams and laser beams and the laser threshold of Hermitian-Gaussian beams of different mode orders (m); Figure 3 The image shows the spot patterns of Hermitian-Gaussian beams of different modes generated by off-axis pumping and the Laguerre-Gaussian beams realized by astigmatic mode converters. Figure 4 Interference patterns (a) of Laguerre-Gaussian beams of different modes interfering with spherical waves through a Mach-Zehnder interferometer and a schematic diagram (b) of controlling the chirality of vortex beams through an astigmatic mode converter; Figure 5 When the output mirror transmittance is 2.6% and the incident pump power is 6.38W, TEM 0,0 Model, LG 0,±1 Model and LG 0,±2 The adjustable wavelength range of the Laguerre-Gaussian beam pattern; Figure 6 When the output mirror transmittance is 1.2% and the incident pump power is 6.38W, TEM 0,0 Model, LG 0,±1 Model and LG 0,±2 The adjustable wavelength range of the Laguerre-Gaussian beam pattern; Figure 7 When the output mirror transmittance is 4.7% and the incident pump power is 6.38W, TEM0,0 Model, LG 0,±1 Model and LG 0,±2 The adjustable wavelength range of the Laguerre-Gaussian beam. Detailed Implementation

[0021] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0022] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0023] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0024] The laser output power was measured using a laser power meter (model: LP-3B) from Physcience Optic-electronics; the laser spectrum was measured using a waveScan spectrometer from APE; and the spot shape was recorded using a pyroelectric array camera (model: Pyrocam III camera) from Ophir.

[0025] A schematic diagram of the off-axis pumped 1.5-1.6μm solid-state vortex laser used in this embodiment is shown below. Figure 1 As shown, it includes the following settings in sequence: The system includes a pump source, a coupling lens group, an input mirror, a gain medium, an output mirror, and an astigmatic mode converter, wherein the astigmatic mode converter comprises a convex lens and a cylindrical lens arranged sequentially.

[0026] Example 1 Er 3+ / Yb 3+ A 3×3mm light-transmitting cross section was cut from a double-doped YAl3(BO3)4 crystal. 2 The thickness in the light transmission direction is 1.5mm. c - A block-shaped sample was cut, and the light-transmitting end face of the block crystal sample was laser-polished. A 976nm continuous fiber-coupled semiconductor laser with a core diameter of 105μm was used as the pump source. The pump beam was focused into the gain medium through a coupling lens group, and the pump spot radius in the gain medium was set to 40μm. The input mirror was a plane mirror with a transmittance of 90% at 976nm and a reflectance of 99.7% in the 1.5-1.6μm band. The output mirror was a plano-concave mirror with a radius of curvature of 100mm and a transmittance of 2.6% in the 1.5-1.6μm band. The resonant cavity length was set to 103mm. The output mirror was fixed on a manual displacement stage, and the offset between the laser beam and the pump beam in the gain medium was adjusted by moving the output mirror laterally through the stage.

[0027] AppendixFigure 2 The relationship between the offsets of different pump beams and laser beams and the laser thresholds of Hermitian-Gaussian beams of different mode orders (m) under the experimental conditions is shown. TEM can be achieved at offsets of 0 μm, 50 μm, 70 μm, 85 μm, and 100 μm, respectively. 0,0 HG 1,0 HG 2,0 HG 3,0 and HG 4,0 Hermitian-Gaussian beam laser output in this mode. (Attached) Figure 3 This paper demonstrates the spot patterns of Hermite-Gaussian beams of different modes generated by off-axis pumping and their conversion to Laguerre-Gaussian beams via astigmatic mode converters. Under the aforementioned conditions, off-axis pumping can achieve Hermite-Gaussian beams of up to the fourth mode, which can be correspondingly converted to Laguerre-Gaussian beams of up to the fourth mode via astigmatic mode converters, exceeding the current level achieved by Er... 3+ / Yb 3+ Double-doped phosphate glass and Er 3+ Laguerre-Gaussian beams of the highest second-order mode realized by a single-doped crystal.

[0028] As attached Figure 4 As shown in (a), the Laguerre-Gaussian beam interferes with a spherical wave through a Mach-Zehnder interferometer. The interference pattern exhibits a petal-like structure and is chiral; different rotational directions represent different orbital angular momentum states. This state can be switched by rotating an astigmatic mode converter perpendicular to the beam propagation direction, as shown in the attached diagram. Figure 4 As shown in (b), the chirality of the Laguerre-Gaussian beam changes after the astigmatic mode converter is rotated by 90°. Therefore, a total of nine orbital angular momentum states, including the fundamental mode, are obtained by using off-axis pumping combined with the astigmatic mode converter, and these states can be quickly switched by changing the offset between the laser beam and the pump beam or by rotating the astigmatic mode converter.

[0029] Example 2 In Example 1, a SiO2 birefringent filter was inserted between the gain medium and the output mirror as a tuning element, positioned at a Brewster angle. The output mirror was fixed to a manual displacement stage. The offset between the laser beam and the pump beam within the gain medium was adjusted by laterally moving the output mirror via the stage to generate Hermitian-Gaussian beams of different mode orders. An astigmatic mode converter was added after the output mirror to convert it into a Laguerre-Gaussian beam of the corresponding mode order. Simultaneously, the birefringent filter was rotated to control the loss at different wavelengths within the cavity, achieving broadband wavelength-tunable 1.5-1.6 μm vortex laser output. When the laser incident pump power was 6.38 W, TEM... 0,0 Model, LG 0,±1 Model and LG 0,±2The tunable wavelength range of the mode Laguerre-Gaussian beam is shown in the appendix. Figure 5 As shown. TEM 0,0 The mode's tuning wavelength range is 90nm (1518-1608nm), LG 0,±1 The mode is 46nm (1516-1562nm), LG 0,±2 The mode is 15nm (1542-1557nm). Under these conditions, the continuously tunable wavelength range achieved is significantly larger than the previously reported Er... 3+ TEM achieved by single-doped crystal vortex laser 0,0 Mode 8.4nm, LG 0,1 Mode 6.8nm and LG 0,2 Mode 4.9nm.

[0030] Example 3 With other experimental conditions remaining unchanged, the transmittance of the output mirror in the 1.5-1.6 μm band in Example 2 was changed to 1.2%. When the laser incident pump power was 6.38 W, the TEM... 0,0 Model, LG 0,±1 Model and LG 0,±2 The tunable wavelength range of the mode Laguerre-Gaussian beam is shown in the appendix. Figure 6 As shown. At this time, TEM 0,0 The maximum continuously tunable wavelength range of the mode is 91nm (1519-1610nm), LG 0,±1 The mode is 18nm (1542-1560nm), LG 0,±2 The mode is 6nm (1553-1559nm). Under these conditions, the continuously tunable wavelength range achieved is also greater than the previously reported Er... 3+ Values ​​of single-doped crystal vortex lasers.

[0031] Example 4 With other experimental conditions remaining unchanged, the transmittance of the output mirror in Example 2 in the 1.5-1.6 μm band was changed to 4.7%. When the laser incident pump power was 6.38 W, the TEM... 0,0 Model, LG 0,±1 Model and LG 0,±2 The tunable wavelength range of the mode Laguerre-Gaussian beam is shown in the appendix. Figure 7 As shown. TEM 0,0 The maximum continuously tunable wavelength range of the mode is 20nm (1540-1560nm), LG 0,±1 The mode is 19nm (1543-1562nm), LG 0,±2 The mode is 5nm (1543-1548nm). Under these conditions, the continuously tunable wavelength range achieved is also greater than the previously reported Er... 3+ Values ​​of single-doped crystal vortex lasers.

[0032] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An off-axis pumped 1.5-1.6μm solid-state vortex laser, characterized in that, Including the following settings in sequence: Pump source, coupling lens group, input mirror, gain medium, output mirror and astigmatic mode converter; The pump source is a semiconductor laser capable of generating laser light in the 910-990nm wavelength range; The coupling lens group is used to focus the pump laser onto the gain medium; The gain medium is Er 3+ / Yb 3+ Double-doped laser crystal; The output mirror is used to adjust the offset between the laser beam and the pump beam in the gain medium, so as to realize off-axis pumping to generate Hermitian-Gaussian beams. The astigmatic mode converter is used to convert the Hermite-Gaussian beam into a Laguerre-Gaussian beam.

2. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The gain medium is Er 3+ / Yb 3+ Double-borate laser crystal, Er 3+ / Yb 3+ Double-doped silicate laser crystal or Er 3+ / Yb 3+ One type of double-doped phosphate laser crystal; Preferably, the crystal is RAl3(BO3)4 or RMgB5O. 10 , Lu2Si2O7, Sc2Si2O7, Ca3NbGa3Si2O 14 One of RPO4, RM3(PO4)3; Where R is one or more of the elements Y, Gd, and Lu, and M is one or more of the elements Ca, Sr, and Ba.

3. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The input mirror has a transmittance of greater than 90% in the 910-990nm wavelength band and a reflectance of greater than 99.5% in the 1.5-1.6μm wavelength band. Preferably, the transmittance of the output mirror in the 1.5-1.6μm band is 0.5-15%.

4. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The output mirror is mounted on the displacement stage; The displacement stage drives the output mirror to move laterally or longitudinally along a direction perpendicular to the optical path to adjust the offset between the laser beam and the pump beam in the gain medium, so as to realize the generation of Hermite-Gaussian beam.

5. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The astigmatic mode converter includes a convex lens and a cylindrical lens arranged in sequence; The convex lens is used to shape the Hermitian-Gaussian beam generated by off-axis pumping, so that the Rayleigh length of the beam is equal to the focal length of the cylindrical lens. The focal point of the cylindrical lens coincides with the waist of the shaped Hermetic-Gaussian beam.

6. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The astigmatic mode converter includes a convex lens, a first cylindrical lens, and a second cylindrical lens arranged sequentially. The convex lens is used to shape the Hermitian-Gaussian beam generated by off-axis pumping, so that the Rayleigh length of the beam is (1+2) times the focal length of the cylindrical lens. 1 / 2 / 2) times; The first cylindrical lens and the second cylindrical lens have the same focal length and the distance between them is 2 times the focal length. 1 / 2 times.

7. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The astigmatism mode converter is mounted on a rotating stage; The astigmatic mode converter has a rotatable range of -45° to 45° along the direction perpendicular to the beam propagation, which is used to change the chirality of the orbital angular momentum of the Laguerre-Gaussian beam.

8. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to claim 1, characterized in that, The gain medium and the output mirror also include a wavelength tuning element.

9. The off-axis pumped 1.5-1.6 μm solid-state vortex laser according to claim 8, characterized in that, The wavelength tuning element is one of the following: SiO2 birefringent filter, Bragg grating, or Fabry-Perot etalon.

10. The off-axis pumped 1.5-1.6μm solid-state vortex laser according to any one of claims 1 to 9 is used in laser communication and optical detection applications.

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