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In the current solution for multiwavelength achromatic flat lenses, a one-to-one correspondence exists between the number of writing phase distributions and the number of achromatic wavelengths. Breaking this correspondence requires a complex phase design and parameter optimization. Here, we show that a dual-layer cascade liquid crystal Pancharatnam-Berry lens (CLCPBL) with two writing phase distributions and a specific coupled phase distribution between the layers can achieve three wavelength achromaticity without any parameter optimization process. Similarly, in a three-layer cascade, the number of achromatic wavelengths increases to seven through the permutations of the layers, with adjustable amplitude factors. We fabricate a three-layer CLCPBL with the design wavelengths of 396.8 nm, 1064 nm, and 1550 nm, which theoretically allows the light at 632.8, 532.8, 3383 and 450 nm to form a common focus, and test such structure. Our CLCPBL enables a wider range of applications than conventional achromatic flat lenses. Metalenses are lightweight and compact alternative to achromatic lens assemblies, but they usually fulfill the focusing requirements for a single wavelength. The authors design and fabricate a cascade liquid crystal Pancharatnam-Berry lens that enables a seven-wavelength achromatic focusing in a broad range of frequencies. [ABSTRACT FROM AUTHOR]

• The performance degradation and compensation method of the beam-steering device based on liquid crystal polarization grating (LCPG) and liquid crystal adjustable half-wave plate (LCAHWP) is studied. • This beam-steering device can still work at a laser power density of 16 W/cm2 irradiation. • The laser tolerance of the device is higher than that of liquid crystal optical phased array (LCOPA) and liquid crystal micro-lens array (LCMLA). The effects of laser irradiation thermal deposition on the performance degradation of liquid crystal (LC) devices in high-power laser systems are extremely vital. In this study, the first-order beam-steering system (FBS) was developed using a passive liquid crystal polarization grating (LCPG) and liquid crystal adjustable wave-plate (LCAW). The LCPG was prepared by holographic exposure technology, and the LCAW was prepared using the standard LC cell preparation process. We investigated the influences of diffraction efficiency of FBS under a 1070-nm continuous-wave (CW) laser irradiation. The energy is concentrated in the −1st order at first. When the half-wave retardation was reached, all the energy is concentrated in the +1st order (∼97 %), and the beam is deflected. Once the phase retardation decreases below the half-wave retardation, the energy gradually reconcentrates in the −1st order. When the LCAW fails, the diffraction the energy is refocused to the −1st order by the LCPG. The results indicated that both thermal deposition and driving voltage reduce the phase retardation of the LCAW, generating a variation of energy between in ± 1 st orders. By reducing the driving voltage, this half-wave retardation can be recovered under a certain half-wave voltage and laser power density, and the diffraction efficiency of the +1st order can be compensated to ∼97 %. If the reduced phase retardation is not less than half-wave, the FBS can still be modulated in high-power continuous lasers. Our research provides a reference for the development of beam-steering technology based on LC materials in high-power laser systems. [ABSTRACT FROM AUTHOR]