阅读说明：本技术 一种拓扑电荷可调节的涡旋光束产生装置 (Vortex light beam generating device with adjustable topology charges ) 是由 张子龙 高原 赵长明 张海洋 李亚弼 于 2020-05-26 设计创作，主要内容包括：本发明提供了一种拓扑电荷可调节的涡旋光束产生装置,能够产生涡旋光束并同时对其拓扑电荷进行调节。本发明采用环形光端面泵浦晶体得到初始的涡旋光束,光束模式纯度高,装置结构紧凑、稳定性好；利用带有旋转对称分布螺旋针孔阵列的衍射屏来改变涡旋光束的拓扑荷数,衍射屏易于取出调换,通过调换不同螺旋结构的衍射屏能够自由且轻便的改变涡旋光束拓扑荷数,装置成本理想,便于操作。(The invention provides a vortex light beam generating device with adjustable topological charges, which can generate vortex light beams and adjust the topological charges of the vortex light beams. The invention adopts the annular optical end face pump crystal to obtain the initial vortex light beam, the purity of the light beam mode is high, the structure of the device is compact, and the stability is good; the diffraction screen with the spiral pinhole array in rotational symmetric distribution is utilized to change the topological charge number of the vortex light beam, the diffraction screen is easy to take out and exchange, the topological charge number of the vortex light beam can be freely and conveniently changed by exchanging the diffraction screens with different spiral structures, the device is ideal in cost, and the operation is convenient.)

1. A vortex light beam generating device with adjustable topological charge is characterized by comprising an optical pumping module, a gain crystal and a diffraction screen; the optical pumping module outputs annular pumping light to the gain crystal, and the gain crystal and the diffraction screen are fixed by a mechanical device;

the diffraction screen is provided with a spiral pinhole array which is rotationally symmetrically distributed, the diffraction screen can be disassembled and replaced, and the topological charge number of the vortex light beam is changed by replacing the diffraction screen.

2. The topologically charge-adjustable vortex beam generating device of claim 1, wherein the diffraction screen is removed and exchanged to achieve vortex beam topological charge number change according to the vortex beam topological charge number of the target.

3. The topologically charge-adjustable vortex beam generating device of claim 1, wherein the optical pumping module comprises a semiconductor laser and a focusing lens; the semiconductor laser is output by optical fiber coupling, and the light emitted by the semiconductor laser is coupled by the optical fiber and converged by the focusing lens to obtain annular pump light.

4. The topologically charge-adjustable vortex beam generating device of claim 1, wherein the ring pump light is pumped to a gain crystal end face.

5. The vortex beam generating device with adjustable topological charge according to claim 1 or 4, wherein, the gain crystal is plated with partial transparent films at two ends to form a Fabry-Perot cavity;

wherein, the front end face is plated with a high reflection film for outputting laser wavelength and a high transmission film for pumping light wavelength, and the rear end face is plated with a high reflection film for outputting laser wavelength.

6. The topologically charge-adjustable vortex beam generating device of claim 1 wherein the topological charge number l is related to the number m and the rotation direction of the spiral pinhole array on the diffraction screen by:

l＝M×m+l₀，M＝0,±1,±2,……

wherein l₀Is LG_0,1The topological charge number of the vortex light beam of the mode, M is a negative number when the rotation direction of the spiral pinhole array is clockwise, and the rotation direction is anticlockwiseM is a positive number.

Technical Field

The invention belongs to the technical field of lasers, and particularly relates to a vortex light beam generating device with adjustable topological charges.

Background

Vortex light beam is a special new oneShaped beams, characterised by a helical phase distribution, each photon in the beam carryingWhere l is called the topological charge number,is a reduced planck constant. The central or axial intensity of the beam in the direction of propagation of the beam remains zero. The vortex light beam has unique property and has important research significance and application prospect in the fields of optical micro-manipulation, space optical communication and the like. Changing the topological charge number of the vortex light beam, namely changing the order of the vortex light beam can change the orbital angular momentum carried by photons. The change of the orbital angular momentum of the vortex light beam can realize the control of the particle binding force on the premise of not changing the light intensity, thereby enhancing the flexibility of the optical tweezers; the structural distribution of the chiral metamaterial can be changed by adjusting the orbital angular momentum, and the method has a good application prospect in the field of metamaterial preparation, so that the adjustment of the topological charge number of the vortex beam has an important significance for the application of the vortex beam. However, the existing vortex beam generation device cannot simultaneously adjust the topological charge of the vortex beams.

Disclosure of Invention

In view of the above, the present invention provides a vortex beam generating device with adjustable topology charge, which can generate a vortex beam and adjust the topology charge of the vortex beam at the same time.

In order to achieve the purpose, the technical scheme of the vortex light beam generation device with the adjustable topological charge is as follows:

the device comprises an optical pumping module, a gain crystal and a diffraction screen; the optical pumping module outputs annular pumping light to the gain crystal, and the gain crystal and the diffraction screen are fixed by a mechanical device;

the diffraction screen is provided with a spiral pinhole array which is rotationally symmetrically distributed, the diffraction screen can be disassembled and replaced, and the topological charge number of the vortex light beam is changed by replacing the diffraction screen.

The diffraction screen is disassembled and exchanged according to the topological charge number of the vortex light beam of the target, so that the topological charge number of the vortex light beam is changed.

The optical pumping module comprises a semiconductor laser and a focusing lens; the semiconductor laser is output by optical fiber coupling, and the light emitted by the semiconductor laser is coupled by the optical fiber and converged by the focusing lens to obtain annular pump light.

Wherein the ring pump light is pumped to the gain crystal end face.

The Fabry-Perot cavity is characterized in that two ends of the gain crystal are plated with partial permeation films to form a Fabry-Perot cavity;

wherein, the front end face is plated with a high reflection film for outputting laser wavelength and a high transmission film for pumping light wavelength, and the rear end face is plated with a high reflection film for outputting laser wavelength.

The relation between the topological charge number l and the number m and the spin direction of the spiral pinhole arrays on the diffraction screen is as follows:

l＝M×m+l₀，M＝0,±1,±2,……

wherein l₀Is LG_0,1The topological charge number of the vortex light beam of the mode, M is a negative number when the rotation direction of the spiral pinhole array is clockwise, and M is a positive number when the rotation direction is anticlockwise.

Has the advantages that:

the invention adopts the annular optical end face pump crystal to obtain the initial vortex light beam, the purity of the light beam mode is high, the structure of the device is compact, and the stability is good; the diffraction screen with the spiral pinhole array in rotational symmetric distribution is utilized to change the topological charge number of the vortex light beam, the diffraction screen is easy to take out and exchange, the topological charge number of the vortex light beam can be freely and conveniently changed by exchanging the diffraction screens with different spiral structures, the device is ideal in cost, and the operation is convenient.

Drawings

FIG. 1(a) is a schematic view of the apparatus of the present invention; FIG. 1(b) is a schematic diagram of a gain crystal and a diffraction screen of the device of the present invention.

FIG. 2(a) is a diffraction screen with a number m of spiral pinhole arrays of 6 and a clockwise rotation direction, according to an embodiment of the present invention; FIG. 2(b) is a diffraction screen with a spiral pinhole array with a number m of 6 and a rotation direction of a quasi-hour hand according to an embodiment of the present invention; FIG. 2(c) is a diffraction screen with 8 spiral pinhole arrays and clockwise rotation direction according to the embodiment of the present invention; fig. 2(d) shows a diffraction screen with 8 spiral pinhole arrays and a counterclockwise rotation direction according to an embodiment of the present invention.

Detailed Description

The invention is described in detail below by way of example with reference to the accompanying drawings.

The device can generate vortex beams and change topological charges of the vortex beams simultaneously by utilizing diffraction and photon Orbital Angular Momentum (OAM) technology and based on organic combination of a microchip laser and a spiral pinhole array diffraction screen. The device comprises an optical pumping module, a gain crystal and a diffraction screen, wherein the optical pumping module outputs pumping light to the gain crystal, the gain crystal and the diffraction screen are fixed by a mechanical device, the diffraction screen is provided with a spiral pinhole array which is rotationally and symmetrically distributed, and the diffraction screen can be freely detached and replaced.

Specifically, the optical pumping module includes a semiconductor laser and a focusing lens. The semiconductor laser is output by optical fiber coupling, and the light emitted by the semiconductor laser is coupled by the optical fiber and converged by the focusing lens to obtain annular pump light.

The ring pump light pump gain crystal obtains an initial vortex light beam, and the topological charge number l of the initial vortex light beam₀Is smaller. The front end face is plated with a high reflection film for outputting laser wavelength and a high transmission film for outputting the pump light wavelength, and the rear end face is plated with a high reflection film for outputting the laser wavelength to form a Fabry-Perot cavity.

The initial vortex light beam outputs the diffraction screen, and because the diffraction screen is provided with the spiral pinhole array which is rotationally and symmetrically distributed, the topological charge number of the light beam after the vortex light beam passes through the diffraction screen is changed. And changing the topological charge number of the vortex light beam by replacing the diffraction screen. When the vortex light beam diffraction screen is actually used, the diffraction screen is freely disassembled and exchanged according to the topological charge number of the vortex light beam of a target, and the change of the topological charge number is realized.

As shown in fig. 1, the present embodiment provides a topology charge adjustable vortex beam generating device, which includes a semiconductor laser 1 coupled out by an optical fiber, a focusing lens 2, a gain crystal, and a diffraction screen 3 with a rotationally symmetric spiral pinhole array.

The semiconductor laser is a laser with the wavelength of 808nm coupled by optical fibers.

The front end face of the gain crystal is plated with a high-reflection film with the wavelength of 1064nm and a high-transmission film with the wavelength of 808nm, the rear end face of the gain crystal is plated with a high-reflection film with the wavelength of 1064nm, and the gain crystal and the diffraction screen are fixed together by a mechanical device.

The measurement method based on the device comprises the following steps:

first, the light beam generated by the semiconductor laser coupled by the optical fiber passes through the focusing lens, and the intensity of the light beam is distributed annularly to obtain annular pump light. Pumping light irradiates the end face of the gain crystal and oscillates in the resonant cavity to obtain LG_0,1Vortex beam of modes, LG_0,1Topological charge number l of mode vortex beam₀Is smaller.

Then, the vortex light beams irradiate on the diffraction screen with the rotationally symmetrical spiral pinhole array, the topological charge number of the light beams is changed, and the changed value is related to the number m and the rotation direction of the spiral pinhole array. As shown in fig. 2(a) -2(d), the number m of the spiral pinhole arrays is 6, 8 and 8 respectively, and the rotation directions are clockwise, counterclockwise, clockwise and counterclockwise respectively.

The relation between the topological charge number l and the number and the rotation direction of the spiral pinhole array is as follows:

l＝M×m+l₀，M＝0,±1,±2,……

and M is a negative number when the rotation direction of the spiral pinhole array is clockwise, and M is a positive number when the rotation direction is anticlockwise.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.