48
J. Eur. Opt. Society-Rapid Publ. 21, 35( 2025)
Figure 1. Simulation graph of the nondiffracting radial carpet-lattice beams generated by the diffraction of radial gratings with multiple odd and even spoke numbers m.
He-Ne Laser |
Beam Expander |
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P 1
SLM P 2
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Fourier transform lens |
CCD |
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SPF |
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SPF: Space pinhole filter SLM: Spatial light modulator P 1�P 2: polarizer CCD: Charge – Coupled Device Camera f = 40 cm
Figure
2. The experimental system for generating nondiffracting radial carpet-lattice beams based on extended Durnin’ s experimental setup.
3 Experiment
To generate the nondiffracting radial carpet-lattice beams, wehadtoextendtheoriginalDurnin’ s setup into a new experimental system, as shown in Figure 2. An amplitude-type SLM is an important element to be used as amplitude modulation. Hence, in our experimental system, the annular pupil aperture with arbitrary azimuthal amplitude components is loaded into the SLM. He-Ne laser source( 632.8 nm) is initially expanded. The collimating parallel laser is incident on the amplitude-type SLM( GC-SLM-T-XGA, 22 lm pixel size, 1080 768 pixels). The SLM resides in the front focal plane of Fourier transform lens with focal length f = 40 cm. The nondiffracting radial carpet-lattice beams can be generated after the Fourier transform lens. In our work, we load the spectrum information of nondiffracting radial carpet-lattice beams on an annular slit with a diameter of 10 mm and a width of 350 lm, as shown in Figure 3. The polarizers are introduced to adjust the incident light to the working polarization state of the SLM, ensuring the optimal amplitude modulation effect. Additionally, it can filter out non-target polarized light to improve the purity of the light beam. The nondiffracting radial carpet-lattice beams are generated and recorded by using a scientific charge-coupled device camera( Microvision 130FC, pixel unit size of 5.4 lm), as shown in Figure 4. Figure 4 shows that the recorded experimental diffraction patterns of the annular slit of radial grating are consistent with the theoretical predictions. Compared Figure 4 with Figure 1, the radial carpet-lattice beams generated by the diffraction of radial gratings with different spoke numbers exhibit shapes that are largely consistent with those simulated by equation( 20). Nondiffracting radial carpet-lattice beams of odd and even orders show distinct shape characteristics. Nondiffracting carpet-lattice beams possess peculiar central radiating optical lattice structures, serving as potential tools for advanced applications such as manufacturing photonic crystal fibers, optical trap for cold atoms or molecules, Bose-Einstein condensation of particle, sub-Doppler cooling, quantum computation, delocalized entanglement of atoms, and so on.