Near-infrared thermally modulated varifocal metalens based on the phase change material Sb₂S₃

Abstract

Focus-tunable metalenses play an indispensable role in the development of integrated optical systems. In this paper, the phase change material Sb2S3 is used in a thermally modulated varifocal metalens based on PB-phase for the first time. Sb2S3 not only has a real part of refractive index shift between the amorphous and crystalline state but also has low losses in both amorphous and crystalline states in the near-infrared region. By switching Sb2S3 between the two states, a metalens doublet with a variable focal length is proposed. Moreover, the full width at half maximum of each focal point is close to the diffraction limit. And the focusing efficiency can be over 50% for the two focal points. Together with the advantage of precise thermal control, the proposed metalens has great potential in the application of multi-functional devices, biomedical science, communication and imaging.

Tunable metasurfaces towards versatile metalenses and metaholograms: a review

“…Furthermore, PCMs have been widely used to make tunable metalenses, by varying the phase of the PCM through the application of external stimuli such as optical pulses, 115 thermal heating, 100 and electrical heating. 101,[116][117][118][119] A rewritable device that uses Ge 2 Sb 2 Te 5 (GST) exploits modulation of the state of GST by an optical pulse. 115 When a GST thin-film is stimulated 96 (c) Schematic illustration of metalenses that are tuned mechanically by rotating the substrate (left) and phase distribution of one of two lenses (right).…”

“…The phase of Sb 2 S 3 is changed by controlling the temperature, and the change affects the focal length. 101 by a femtosecond laser pulse, it causes partial state transition of GST and causes phase patterning. Active metasurfaces using a related optical PCM, Ge 2 Sb 2 Se 4 Te 1 (GSST) have been demonstrated to realize a highly varifocal metalens that operates at λ ¼ 5.2 μm and has NAs of 0.45 (amorphous) and 0.35 (crystalline).…”

“…3(g)]. 101 By controlling the temperature of Sb 2 S 3 , its phase can be converted. The refractive index of Sb 2 S 3 varies depending on its phase; this change causes the phase shift of incident light, and thereby achieves tunable focal length.…”

Next-Generation Imaging Techniques: Functional and Miniaturized Optical Lenses Based on Metamaterials and Metasurfaces

“…In addition, they are also showing the possibility of use in functional optical devices that are complicated to implement with traditional optical lenses; examples include a full-Stokes polarization camera [98], a depth-sensing camera that uses multi-focal length metalenses [99,100] and varifocal metalenses [83,[101][102][103][104]. Other technologies of organic light-emitting diodes [105], wearable optical devices [106] are also being combined with original industries.…”

High Q Resonant Sb2S3-Lithium Niobate Metasurface for Active Nanophotonics

“… (GST) and are probably the commonest PCMs in nanophotonics [ 4 , 5 , 6 ]. They are widely used in applications such as dynamic thermal emission [ 7 , 8 , 9 , 10 ], light modulation [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], beam steering [ 18 , 19 ], polarization conversion [ 20 ], colour display [ 21 , 22 , 23 ] and various tunable metasurfaces and metadevices [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Customized laser has already been used to write, erase, and rewrite GST films into two-dimensional binary or gray-scale functional patterns, which would induce local refractive index changes and construct nanophotonic devices [ 36 ].…”