Active multiband varifocal metalenses based on orbital angular momentum division multiplexing

Abstract

Metalenses as miniature flat lenses exhibit a substantial potential in replacing traditional optical component. Although the metalenses have been intensively explored, their functions are limited by poor active ability, narrow operating band and small depth of field (DOF). Here, we show a dielectric metalens consisting of TiO2 nanofins array with ultrahigh aspect ratio to realize active multiband varifocal function. Regulating the orbital angular momentum (OAM) by the phase assignment covering the 2π range, its focal lengths can be switched from 5 mm to 35 mm. This active optical multiplexing uses the physical properties of OAM channels to selectively address and decode the vortex beams. The multiband capability and large DOFs with conversion efficiency of 49% for this metalens are validated for both 532 nm and 633 nm, and the incidence wavelength can further change the focal lengths. This non-mechanical tunable metalens demonstrates the possibility of active varifocal metalenses.

Direct‐Printing Hydrogel‐Based Platform for Humidity‐Driven Dynamic Full‐Color Printing and Holography

“…Flat optics and metasurfaces, as representatives of planar nanophotonics, exhibit brilliant capability of arbitrarily manipulating light field in subwavelength scale, [1][2][3][4] thus promoting various applications for structural color, [5][6][7][8] beam steering, [9][10][11][12] meta-holography, [13][14][15][16][17][18] lensing, [19][20][21] etc. To endow the post-fabrication tuning ability of the optical devices, several tunable materials such as liquid crystals, [22][23][24][25][26][27][28] phase-change materials, [29][30][31] transparent conductive materials, [32,33] elastomeric polymer, [34][35][36] doped semiconductors, [37,38] and chemically-responsive materials [39] have been employed to construct the nanodevices.…”

Broadband Achromatic Metalens in the Visible Light Spectrum Based on Fresnel Zone Spatial Multiplexing

“…As shown in Figure 1 c,d, expect for the falling peaks, the transmittance is high. The falling peaks are produced by guided mode resonances when the incident light is coupled with the surface mode of the periodic lattice [ 49 , 50 ]. In the simulation and fabrication of metalenses, the nanopillars corresponding to the falling peaks were removed so that each unit cell in the phase library maintained a high transmittance.…”

“…Compared with a traditional lens, a metalens is smaller and the control of the light field is more flexible, which provides the possibility for the miniaturization and integration of the optical system. There are numerous applications based on metalenses, such as light field imaging [ 46 , 47 ], color routing [ 48 ], orbital angular momentum multiplexing [ 49 ], and fiber focusing [ 50 ].…”

Recent Advances and Prospects of Optical Metasurfaces

“…Owing to their large information capacity and diverse optical recording ability, metasurfaces can greatly enrich the design freedom of structured light combined with other techniques, such as introducing Dammann gratings, 24,79,91 polarization multiplexing, 17,18,91 frequency multiplexing, 16,87 and spatial multiplexing. 92 For instance, by combining GVB with a Dammann vortex metasurface, a special differential calculator was proposed. 91 The diffraction multiplexed array was controlled by the linear combination of different basic GVB functions.…”