An ultraviolet supercontinuum vortex light generating device and a generating method

Abstract

An ultraviolet supercontinuum vortex light generating device and method. The device comprises a light source module and an ultraviolet supercontinuum vortex light generating module. The method combines laser synergy continuous radiation mechanism and spatial phase control technology for the first time to generate ultraviolet supercontinuum vortex light. The supercontinuum radiation is generated by five-photon resonance excitation of molecular ions by mid-infrared vortex light, so each frequency component in the continuous spectrum carries the same orbital angular momentum, and the topological charge is five times that of the pump light. By adjusting the orbital angular momentum of the mid-infrared pump light and the order of the multi-photon resonance excitation, the topological charge of the supercontinuum vortex light can be adjusted within a certain range. The device and method not only expand the application potential of supercontinuum radiation in the fields of biomedical imaging, optical communication, precise light field manipulation, etc., but also are suitable for shorter wave bands such as deep ultraviolet and extreme ultraviolet, providing a way to generate isolated attosecond pulses with single orbital angular momentum.

Description

Technical Field

[0001] This invention relates to the field of ultrafast optics and light field manipulation, specifically to a device and method for generating ultraviolet supercontinuous vortex light. Background Technology

[0002] Vortex light, with its helical phase wavefront and orbital angular momentum characteristics, holds significant promise for applications in high-capacity optical communication, optical manipulation, and high-resolution imaging. Currently, the generation of most vortex lights relies on spatial phase modulation devices for specific wavelengths, such as helical phase plates or spatial light modulators. These components are generally designed with phase distributions for a single wavelength. When used to generate supercontinuous vortex light covering a wide spectral range, spatial dispersion is inevitably introduced, making it difficult to maintain a stable phase structure with a single topological charge during generation. Spatial dispersion directly affects the application performance of supercontinuous vortex light. For example, in optical communication, it may lead to increased crosstalk in orbital angular momentum modes, thereby increasing decoding errors; in optical manipulation, it can cause force field inhomogeneity, reducing manipulation accuracy; and in fiber optic transmission, it can increase transmission loss. These negative effects highlight the importance of maintaining topological charge stability during the generation, transmission, and application of supercontinuous vortex light (see V. Nikolay et al., Light Adv. Manuf. 3, 54 (2022)).

[0003] Supercontinuous coherent light sources not only provide important tools for scientific research such as optical coherence tomography, molecular structure analysis, and photochemical reaction detection, but also have significant application prospects in the sensitive detection of toxic and harmful gases and the remote detection of explosives and biochemical agents. Supercontinuous coherent light sources are generally generated through the nonlinear interaction between lasers and transparent media. A common method is to inject laser pulses into gas-filled optical fibers or wide-bandgap solid materials, utilizing third-order nonlinear optical effects such as self-phase modulation, four-wave mixing, and self-steepening during propagation. Based on these methods, supercontinuous light sources in the visible and near-infrared bands can be easily obtained, and vortex continuous radiation can be achieved (see L. Xu et al., Photon. Res.10, 802-809 (2022)). However, due to limitations in the generation mechanism and the intrinsic absorption and dispersion characteristics of materials, the extension of supercontinuous vortex light into the ultraviolet band faces technical challenges. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention aims to provide a device and method for generating ultraviolet supercontinuum vortex light with stable wavefront and a single topological charge. It utilizes a dynamic Stark effect-assisted strong laser field and the five-photon resonance of a molecular ion system to generate coordinated laser continuous radiation. The supercontinuum radiation generated through this mechanism not only covers the 300–400 nm ultraviolet band, but also ensures that each frequency component in the supercontinuum spectrum carries the same orbital angular momentum, with a topological charge five times that of the pump light.

[0005] The ultraviolet supercontinuum vortex light generated by this invention has advantages such as a wide spectral range, no spatial dispersion, simple device, and broad application prospects. It is suitable for different molecular gases and different wavelengths, and has a certain ability to control topological charge. The generation of ultraviolet supercontinuum vortex light not only provides a new perspective for studying the extreme nonlinear interaction between vortex light and matter, but also stimulates the application potential of supercontinuum light sources in fields such as biomedical imaging, optical communication, and precision optical manipulation.

[0006] The technical solution of the present invention is as follows:

[0007] A device for generating ultraviolet supercontinuous vortex light, comprising:

[0008] A light source module is used to generate mid-infrared femtosecond vortex light; the light source module includes a near-infrared femtosecond laser (1), an optical parametric amplifier (2), a first dichroic mirror (3), an aperture (4), and a spiral phase plate (5) connected or arranged in sequence; the near-infrared femtosecond laser (1) outputs a femtosecond laser with an energy of 6 mJ and a center wavelength of 800 nm, which generates a mid-infrared femtosecond laser with a center wavelength of 1580 nm and a single pulse energy of 1 mJ through the optical parametric amplifier (2).

[0009] Furthermore, the spiral phase plate (5) is a first-order vortex phase plate with a working wavelength of 1580 nm, and is installed on a three-dimensional displacement platform for three-dimensional fine adjustment. The mid-infrared femtosecond laser is phase-modulated through the vortex phase plate to generate a first-order femtosecond vortex light in the mid-infrared band.

[0010] The ultraviolet supercontinuous vortex light generation module generates mid-infrared femtosecond vortex light from the light source module, which is focused by a lens and generates nitrogen molecular ions through strong field tunneling ionization of nitrogen gas. It utilizes a laser-coordinated continuous radiation mechanism to generate supercontinuous coherent radiation in the ultraviolet band. Since this process is homologous to the five-photon resonance, the generated supercontinuous radiation carries the same single higher-order orbital angular momentum as the fifth harmonic, i.e., ultraviolet supercontinuous vortex light. The ultraviolet supercontinuous vortex light generation module includes a focusing lens (6) and a nitrogen-filled gas cavity (7). The gas cavity (7) is also connected to a mechanical pump (8), a vacuum gauge (9), and a flow control valve (10), and is filled with low-pressure nitrogen gas during operation.

[0011] The device also includes a spectral measurement module and a spot and orbital angular momentum measurement module; the spectral measurement module is placed after the ultraviolet supercontinuous vortex light generation module and is coaxial with the optical path; the spot and orbital angular momentum measurement module is arranged intersecting with the spectral measurement module;

[0012] The spectral measurement module is used to measure the spectrum of ultraviolet supercontinuum vortex light. It includes a collimating lens (11), a second dichroic mirror (12), a filter (13), a collecting lens (14), and a grating spectrometer (15) arranged in sequence. The module is set after the gas cavity and is coaxially arranged with the optical path that generates ultraviolet supercontinuum vortex light. Based on the spectral signal collected in real time by the grating spectrometer (15), the nitrogen gas pressure is optimized to obtain stronger ultraviolet continuous radiation.

[0013] The beam spot and orbital angular momentum measurement module is used to characterize the spatial intensity distribution and topological charge of ultraviolet supercontinuum vortex light. It includes an aluminum mirror (16) and a beam quality analyzer (17) arranged in sequence, and an attenuator (18) and a cylindrical lens (19) selectively arranged behind the aluminum mirror. The aluminum mirror (16) is arranged on the optical path between the filter (13) and the collecting lens (14) and intersects the optical path. The module performs fine adjustment and optimizes the nitrogen pressure on the three-dimensional displacement stage where the spiral phase plate (5) is located based on the beam spot signal collected in real time by the beam quality analyzer (17), so that the ultraviolet supercontinuum light presents a symmetrical annular spatial distribution. When the attenuator (18) and the cylindrical lens (19) are inserted into the optical path behind the aluminum mirror (16), the beam quality analyzer (17) is moved to the focal point of the cylindrical lens (19) to detect the topological charge of the ultraviolet supercontinuum vortex light.

[0014] Furthermore, the second dichroic mirror (12) is a dichroic mirror with high transmittance in the 300-400 nm band and high reflectance near the 1580 nm wavelength, used for the separation of mid-infrared light and ultraviolet supercontinuum light, thereby obtaining ultraviolet supercontinuum vortex light.

[0015] Furthermore, the ultraviolet supercontinuous vortex light is focused onto the grating spectrometer (15) by the collecting lens (14), or reflected onto the beam quality analyzer (17) by the aluminum mirror (16), and the cylindrical lens (19) is used to measure the topological charge of the vortex light.

[0016] This invention also provides a method for generating ultraviolet supercontinuum vortex light, which is implemented using the ultraviolet supercontinuum vortex light generating device described above, and includes the following steps:

[0017] 1) Turn on the mechanical pump (8) connected to the gas chamber (7) and pump the gas until the chamber is close to a vacuum state. Then turn on the flow control valve (10) of the gas chamber and fill the gas chamber with high-purity nitrogen.

[0018] 2) Start the near-infrared femtosecond laser (1) to output femtosecond laser, start the optical parametric amplifier (2) to output mid-infrared femtosecond laser with a center wavelength of 1580 nm;

[0019] 3) Adjust the three-dimensional displacement platform and optimize the position of the spiral phase plate (5) to convert the mid-infrared Gaussian light into vortex light;

[0020] 4) The mid-infrared femtosecond vortex light is focused by lens (6) onto a gas cavity (7) filled with high-purity nitrogen. The emitted light signal is collimated by lens (11) and then subjected to spectral filtering by a second dichroic mirror (12) and a filter (13) to obtain ultraviolet supercontinuum vortex light.

[0021] The basic design concept of the technical solution of this invention is:

[0022] Under the influence of mid-infrared femtosecond vortex light, nitrogen molecules are ionized, and the resulting molecular ions are instantaneously placed in a strong laser field. Due to the dynamic Stark effect, the energy difference between the ground state and excited state of the molecular ions increases instantaneously and changes continuously with the temporal envelope of the laser field. When the transient transition energy satisfies the five-photon resonance condition, the nitrogen molecular ions in the ground state transition to the excited state and establish ionic coherent polarization. Subsequently, the coherent polarization induces the excited-state ions to transition back to the ground state and generate strong coherent radiation. The wavelength of this radiation changes continuously with the transient transition energy caused by the Stark effect, thus forming ultraviolet supercontinuum coherent radiation. Since the supercontinuum radiation originates from five-photon resonance excitation, according to the law of conservation of angular momentum, different frequency components of the supercontinuum carry the same orbital angular momentum as the fifth harmonic, and its topological charge is five times that of the mid-infrared vortex pump light.

[0023] Compared to traditional optical field manipulation techniques such as vortex phase plates and spatial light modulators, the method employed in this invention utilizes the five-photon resonance effect to convert and transfer the orbital angular momentum of the fundamental frequency light. Its advantages lie in the absence of spatial dispersion interference and the fact that it is not limited by the intrinsic absorption of phase modulation devices, allowing it to be extended to the deep ultraviolet and even vacuum ultraviolet bands. This invention utilizes the high-order nonlinear effect of a nitrogen molecular ion system prepared in a strong field to generate ultraviolet supercontinuum vortex light, whose orbital angular momentum can maintain a single mode over a nearly 100-nanometer wide spectral range. Notably, in the specific embodiment shown in this invention, the topological charge of the ultraviolet supercontinuum radiation is five times that of the pump light. Moreover, by controlling the orbital angular momentum of the pump light and the order of multiphoton resonance excitation, the topological charge of the supercontinuum vortex light can be controlled within a certain range.

[0024] The universality of this invention lies in the fact that the principle can be extended to other molecular ion systems and different spectral bands. By adjusting the pump light wavelength and selecting a suitable molecular ion system, the spectral range of supercontinuum radiation can be expanded, generating supercontinuum vortex light in the deep ultraviolet and even vacuum ultraviolet bands, providing a new approach for synthesizing isolated attosecond pulses with a single orbital angular momentum.

[0025] Compared with the prior art, the technical effects of the present invention are as follows:

[0026] 1) The laser-coordinated continuous radiation mechanism used in this invention can generate ultraviolet supercontinuous vortex light with a single topological charge, thus solving the problem of spatial dispersion of broadband vortex light.

[0027] 2) By adjusting the orbital angular momentum of the pump light and the order of multiphoton resonance excitation, this invention can achieve the control of the topological charge of supercontinuous vortex light within a certain range, enriching the control methods of high-order vortex light in the ultraviolet band.

[0028] 3) This invention provides an scalable fabrication approach for ultraviolet supercontinuous coherent light sources and their spatial manipulation. This principle can not only be extended to other molecular ion systems, but also used for spatial manipulation of supercontinuous radiation in the deep ultraviolet and even extreme ultraviolet bands to generate attosecond vortex light pulses. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a device for generating and detecting ultraviolet supercontinuous vortex light.

[0030] Wherein: 1 is a near-infrared femtosecond laser, 2 is an optical parametric amplifier, 3 is a first dichroic mirror, 4 is an aperture, 5 is a spiral phase plate, 6 is a focusing lens, 7 is a gas cavity, 8 is a mechanical pump, 9 is a vacuum gauge, 10 is a flow control valve, 11 is a collimating lens, 12 is a second dichroic mirror, 13 is a filter, 14 is a collecting lens, 15 is a grating spectrometer, 16 is an aluminum mirror, 17 is a beam quality analyzer, 18 is an attenuator, and 19 is a cylindrical lens.

[0031] Figure 2 This is the spectral detection result of the ultraviolet supercontinuous vortex light generated by the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of this invention.

[0033] Please see Figure 1 , Figure 1This is a schematic diagram of the device for generating and detecting ultraviolet supercontinuum vortex light according to the present invention. As shown in the figure, it includes a light source module, which consists of a near-infrared femtosecond laser 1, an optical parametric amplifier 2, a first dichroic mirror 3, an aperture 4, and a spiral phase plate 5 connected or arranged in sequence; an ultraviolet supercontinuum vortex light generation module, which consists of a focusing lens 6 and a gas cavity 7, the gas cavity being connected to a mechanical pump 8, a vacuum gauge 9, and a flow control valve 10 respectively; a spectral measurement module, which consists of a collimating lens 11, a second dichroic mirror 12, a filter 13, a collecting lens 14, and a grating spectrometer 15; and a spot and orbital angular momentum measurement module, which consists of an aluminum mirror 16, a beam quality analyzer 17, an attenuator 18, and a cylindrical lens 19, the aluminum mirror 16 being arranged in the optical path between the filter 13 and the collecting lens 14 and intersecting the optical path (at a 45-degree angle in this embodiment).

[0034] The first dichroic mirror 3 is a long-pass dichroic mirror with a starting wavelength of 950 nm. The spiral phase plate 5 operates at a wavelength of 1580 nm and has a vortex order of 1. This spiral phase plate is mounted on a three-dimensional adjustable displacement stage (not shown in the figure) and is used to finely adjust the spatial distribution of mid-infrared femtosecond vortex light, thereby generating uniformly distributed mid-infrared femtosecond vortex light. The second dichroic mirror 12 and the filter 13 both have high transmittance in the 300–400 nm range to obtain a clean ultraviolet continuous radiation spectrum. When measuring the spatial distribution of the signal, an aluminum mirror 16 is placed to change the beam direction and reflect it to the beam quality analyzer 17 to obtain the spatial distribution of the ultraviolet supercontinuum light. When characterizing the topological charge of the ultraviolet supercontinuum vortex light, an attenuator 18 and a cylindrical lens 19 are inserted, and the beam quality analyzer is moved to the focal point of the cylindrical lens to characterize the topological charge of the vortex light. Under the action of a cylindrical lens, the Laguerre-Gaussian light spot will be transformed into a Hermitian-Gaussian spatial distribution, and a striped distribution of light and dark will appear near its focal plane. For example, the m-th order vortex light has m dark stripes and m+1 bright stripes.

[0035] Please see Figure 2 , Figure 2 This is the spectral detection result of the ultraviolet supercontinuum vortex light generated by this invention. At an atmospheric pressure of 30 mbar, a relatively uniformly distributed ultraviolet supercontinuum vortex light was generated through fine adjustment of the spiral phase plate. According to the spectral signal acquired in real time by the grating spectrometer 15, the continuous spectrum in the 300-400 nm range is significantly higher than the background noise, indicating that a strong ultraviolet supercontinuum vortex light was obtained.

[0036] The steps for generating ultraviolet supercontinuum vortex light in this invention are as follows:

[0037] 1) Turn on the mechanical pump 8 and evacuate to a vacuum state. Then turn off the mechanical pump, open the flow control valve 10 of the gas chamber 7, and fill it with high-purity nitrogen at a suitable pressure.

[0038] 2) Start the near-infrared femtosecond laser 1 to output femtosecond laser, start the optical parametric amplifier 2 to output mid-infrared femtosecond laser with a center wavelength of 1580 nm; and obtain a near-Gaussian distribution mid-infrared femtosecond laser through the first dichroic mirror 3 and the aperture 4.

[0039] 3) Adjust the position of the spiral phase plate 5 using a three-dimensional displacement platform to convert mid-infrared Gaussian light into vortex light;

[0040] 4) The mid-infrared femtosecond vortex light is focused by lens 6 into the gas cavity 7 filled with high-purity nitrogen. The emitted light signal is collimated by lens 11 and then filtered by the second dichroic mirror 12 and filter 13 to obtain ultraviolet supercontinuum vortex light.

[0041] 5) The ultraviolet supercontinuous vortex light is focused by the collecting lens 14 onto the center of the slit of the grating spectrometer 15 to collect and analyze the spectral signal.

[0042] 6) Based on the real-time acquired spectral signals, the nitrogen pressure is adjusted and optimized by vacuum gauge 9 and flow control valve 10 to obtain strong continuous ultraviolet radiation;

[0043] 7) Insert an aluminum mirror 16 after the filter 13 to guide the ultraviolet supercontinuum light to the beam quality analyzer 17 for spot acquisition. Based on the real-time acquired spot signal, finely adjust the three-dimensional displacement stage where the spiral phase plate 5 is located and optimize the nitrogen gas pressure so that the acquired spot presents a symmetrical annular spatial distribution.

[0044] 8) Insert attenuator 18 and cylindrical lens 19 behind aluminum mirror, move beam quality analyzer 17 to the focal point of cylindrical lens, and collect and analyze the topological charge of ultraviolet supercontinuum vortex light.

[0045] 9) Remove the aluminum mirror and repeat the spectral acquisition steps in step 5) to acquire and analyze the signal.

[0046] The principle of obtaining ultraviolet supercontinuum vortex light in this invention is as follows:

[0047] A mid-infrared vortex-pumped laser is focused into gas cavity 7, causing nitrogen molecules within the cavity to tunnel and ionize. The resulting nitrogen ions are instantaneously placed in a strong laser field. Due to the dynamic Stark effect, the nitrogen ions undergo energy level shifts, increasing the energy difference between the ground and excited states. When the instantaneous transition energy satisfies the multiphoton resonance condition, the ground-state ions are coherently excited, inducing coherent ion radiation. The wavelength of this radiation depends on the instantaneous transition energy of the nitrogen ions under the strong field. Under the strong field Stark effect, the instantaneous transition energy of the nitrogen ions continuously changes with the laser field envelope, resulting in a continuous change in the wavelength of the coherent radiation from the nitrogen ions. The ion radiation generated at different times constitutes ultraviolet supercontinuum light. Since this supercontinuum radiation originates from five-photon resonance excitation, according to the law of conservation of angular momentum, different frequency components of the supercontinuum carry the same orbital angular momentum as the fifth harmonic, and its topological charge is five times that of the mid-infrared vortex-pumped light. In this way, ultraviolet supercontinuum vortex light with a single orbital angular momentum can be generated.

Claims

1. A device for generating ultraviolet supercontinuous vortex light, characterized in that, include: The light source module is used to generate mid-infrared femtosecond vortex light, including a near-infrared femtosecond laser (1), an optical parametric amplifier (2), a first dichroic mirror (3), an aperture (4), and a spiral phase plate (5) connected or arranged in sequence; the spiral phase plate (5) is a first-order vortex phase plate with a working wavelength of 1580 nm, and is installed on a three-dimensional displacement platform for three-dimensional fine adjustment. The mid-infrared femtosecond laser is phase-modulated through the vortex phase plate to generate first-order femtosecond vortex light in the mid-infrared band. The ultraviolet supercontinuous vortex light generation module includes a focusing lens (6) and a nitrogen-filled gas cavity (7). The device also includes a spectral measurement module and a spot and orbital angular momentum measurement module; the spectral measurement module is placed after the ultraviolet supercontinuous vortex light generation module and is coaxial with the optical path; the spot and orbital angular momentum measurement module is arranged intersecting with the spectral measurement module; The spectral measurement module is used to measure the spectrum of ultraviolet supercontinuum vortex light. It includes a collimating lens (11), a second dichroic mirror (12), a filter (13), a collecting lens (14), and a grating spectrometer (15) arranged in sequence. The module is set after the gas cavity (7) and is coaxially arranged with the optical path that generates ultraviolet supercontinuum vortex light. Based on the spectral signal collected in real time by the grating spectrometer (15), the nitrogen gas pressure is optimized to obtain stronger ultraviolet continuous radiation. The beam spot and orbital angular momentum measurement module is used to characterize the spatial intensity distribution and topological charge of ultraviolet supercontinuum vortex light. It includes an aluminum mirror (16) and a beam quality analyzer (17) arranged in sequence, and an attenuator (18) and a cylindrical lens (19) selectively arranged behind the aluminum mirror. The aluminum mirror (16) is arranged on the optical path between the filter (13) and the collecting lens (14) and intersects the optical path. The module performs fine adjustment and optimizes the nitrogen pressure on the three-dimensional displacement stage where the spiral phase plate (5) is located based on the beam spot signal collected in real time by the beam quality analyzer (17), so that the ultraviolet supercontinuum light presents a symmetrical annular spatial distribution. When the attenuator (18) and the cylindrical lens (19) are inserted on the optical path behind the aluminum mirror (16), the beam quality analyzer (17) is moved to the focal point of the cylindrical lens (19) to detect the topological charge of the ultraviolet supercontinuum vortex light. The mid-infrared femtosecond vortex light generated by the light source module is focused by a focusing lens and generates nitrogen molecular ions by tunneling through strong field to ionize nitrogen gas. Supercontinuous coherent radiation in the ultraviolet band is generated by using a laser-coordinated continuous radiation mechanism. The device converts and transfers the orbital angular momentum of the fundamental frequency light by means of the five-photon resonance effect. Therefore, the generated ultraviolet supercontinuous radiation carries the same single high-order orbital angular momentum as the fifth harmonic. By controlling the orbital angular momentum of the pump light and the order of multiphoton resonance excitation, the topological charge of the supercontinuous vortex light can be controlled within a certain range, avoiding spatial dispersion effects.

2. The ultraviolet supercontinuum vortex light generating device according to claim 1, characterized in that, The near-infrared femtosecond laser (1) outputs a femtosecond laser with an energy of 6 mJ and a center wavelength of 800 nm, which is then used by an optical parametric amplifier (2) to generate a mid-infrared femtosecond laser with a center wavelength of 1580 nm and a single pulse energy of 1 mJ.

3. The ultraviolet supercontinuum vortex light generating device according to claim 1, characterized in that, The gas chamber (7) is connected to the mechanical pump (8), vacuum gauge (9) and flow control valve (10) respectively, and is filled with low-pressure nitrogen gas during operation.

4. The ultraviolet supercontinuum vortex light generating device according to claim 1, characterized in that, The second dichroic mirror (12) is a dichroic mirror with high transmittance in the 300-400 nm band and high reflectance near the 1580 nm wavelength, used for the separation of mid-infrared light and ultraviolet supercontinuum light, thereby obtaining ultraviolet supercontinuum vortex light.

5. The ultraviolet supercontinuum vortex light generating device according to claim 1, characterized in that, The ultraviolet supercontinuous vortex light is focused onto the grating spectrometer (15) by the collecting lens (14), or reflected onto the beam quality analyzer (17) by the aluminum mirror (16). The cylindrical lens (19) is used to measure the topological charge of the vortex light.

6. A method for generating ultraviolet supercontinuous vortex light, characterized in that, This is achieved by the ultraviolet supercontinuum vortex light generating device according to any one of claims 1 to 5, comprising the following steps: 1) Turn on the mechanical pump (8) connected to the gas chamber (7) and pump the gas until the chamber is close to a vacuum state. Then turn on the flow control valve (10) of the gas chamber and fill the gas chamber with high-purity nitrogen. 2) Start the near-infrared femtosecond laser (1) to output femtosecond laser, start the optical parametric amplifier (2) to output mid-infrared femtosecond laser with a center wavelength of 1580 nm; 3) Adjust the three-dimensional displacement platform and optimize the position of the spiral phase plate (5) to convert the mid-infrared Gaussian light into vortex light; 4) The mid-infrared femtosecond vortex light is focused by the focusing lens (6) into the gas cavity (7) filled with high-purity nitrogen. The outgoing light signal is collimated by the collimating lens (11) and then filtered by the second dichroic mirror (12) and the filter (13) to obtain ultraviolet supercontinuum vortex light.

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