Ultrahigh-aperture dual-band gradient index-diffractive infrared objective

Subject of study. An optical system, designed using thin homogeneous lenses and an infinitely thin model of a thick, coaxial laminated radial-gradient-index lens (made from a composite gradient index material), was investigated. In addition, an ultrahigh-aperture dual-band gradient index-diffractive infrared triplet design was developed. Aim of study. The objective was to model and design an optical system incorporating a coaxial laminated radial-gradient-index lens and to demonstrate the potential of an ultrahigh-aperture dual-band infrared objective, consisting of two homogeneous lenses and one radial-gradient-index lens. Method. Theoretical analyses, computer modeling, and optimization were performed using the Zemax optical design program. Main results. The results demonstrate the feasibility of using the proposed infinitely thin model of a coaxial laminated radial-gradient-index lens (whose optical power and longitudinal chromatism are the same as those of its thick prototype), combined with thin homogeneous lenses separated by air gaps, as the initial design for the developed optical system. When the refractive index distribution of the gradient lens is known, the optimal combination of optical materials for the homogeneous lenses and the ratio of optical powers of all system elements may be determined by iteratively solving the corresponding equations for achromatization, apochromatization, and superchromatization. The resulting optical design, structural parameters, and optical characteristics of a calculated dual-band (3.5–5 µm and 8–11.9 µm) triplet, comprising two homogeneous lenses and one gradient lens, confirm the effectiveness of the proposed approach and high optical performance in objectives of this type. Practical significance. The results of this study are expected to promote the development of coaxial laminated radial-gradient-index lenses based on existing composite gradient index materials, facilitating the creation of high-performance, ultrahigh-aperture dual-band gradient index-diffractive infrared objectives for advanced optical applications.