Ultralow dispersion and broadband gradient refractive index microlens arrays imprinted in chalcohalide glass by microthermal poling

Ultralow dispersion gradient refractive index (GRIN) microlens arrays (MLAs) covering the visible to mid-infrared wavelength range are imprinted in GeS2-Ga2S3-CsI chalcohalide glass by an efficient and economical microthermal poling process. The effect of poling voltage on GRIN microstructure, structural rearrangement, optical properties of the poled glasses, and imaging of the imprinted MLAs have been investigated. Optical focal length of the GRIN MLAs decreases from 353 to 63 μm with increasing the poling voltage from 200 to 1000 V, which is in accordance with imprinting-induced phase difference increase from 0.57λ to 1.19λ. Optimal chromatic aberration (between 520 and 850 nm) as low as 5% is achieved in the GRIN MLAs. Formation mechanism of GRIN MLAs is mainly associated with an enhanced transverse migration of Cs+ ions within mesh square area, which is provided by an improved anode of microthermal poling setup. Thus, an efficient and inexpensive process developed can produce broadband and ultralow dispersion GRIN MLAs for imaging, display, and photovoltaic applications.