Hybrid meta/refractive lens design with an inverse design using physical optics.

Hybrid lenses are created by combining metasurface optics with refractive optics, where refractive elements contribute optical power, while metasurfaces correct optical aberrations. We present an algorithm for optimizing metasurface nanostructures within a hybrid lens, allowing flexible interleaving of metasurface and refractive optics in the optical train. To efficiently optimize metasurface nanostructures, we develop a scalar field, ray-wave hybrid propagation method. This method facilitates the propagation of incident and derived adjoint fields through optical elements, enabling effective metasurface optimization within the framework of adjoint gradient optimization. Numerical examples of various lens configurations are presented to illustrate the versatility of the algorithm and showcase the benefits offered by the proposed approach, allowing metasurfaces to be positioned beyond the image space of a lens. Taking a F/2, 40° field-of-view, midwave infrared lens as an example, the lens exhibits an average focusing efficiency of 38% before the integration of metasurfaces. Utilizing the new algorithm to design two metasurfaces-one in the object space and one in the image space-results in significant enhancement of the average focusing efficiency to over 90%. In contrast, a counterpart design with both metasurfaces limited to the image space yields a lower average focusing efficiency of 73%.

Broadband metasurface aberration correctors for hybrid meta/refractive MWIR lenses: publisher's note.

This publisher's note contains corrections to [Opt. Express30, 28438 (2022)10.1364/OE.460941].

Broadband metasurface aberration correctors for hybrid meta/refractive MWIR lenses.

A method for designing multi-metasurface layouts for optical aberration correction is presented. All-dielectric metasurfaces are combined with conventional refractive optics to form a hybrid lens. The optical power of a hybrid lens is primarily provided by refractive optics, and metasurfaces are optimized to control optical aberrations. This approach greatly reduces the magnitude of phase gradient required for a largescale metasurface and hence its diffraction loss. An inverse design technique is incorporated to optimize all physical parameters on a metasurface to minimize image spots across all sampling field angles and wavelengths. This approach is put to test by designing a hybrid lens composed of a midwave infrared refractive lens followed by a pair of metasurfaces. Moreover, we demonstrate the working bandwidth of the hybrid lens can be further extended by reducing phase dispersion introduced by a metasurface using holey meta-atoms instead of pillar meta-atoms.

Volumetric imaging efficiency: the fundamental limit to compactness of imaging systems.

A new metric for imaging systems, the volumetric imaging efficiency (VIE), is introduced. It compares the compactness and capacity of an imager against fundamental limits imposed by diffraction. Two models are proposed for this fundamental limit based on an idealized thin-lens and the optical volume required to form diffraction-limited images. The VIE is computed for 2,871 lens designs and plotted as a function of FOV; this quantifies the challenge of creating compact, wide FOV lenses. We identify an empirical limit to the VIE given by VIE < 0.920 × 10-0.582×FOV when using conventional bulk optics imaging onto a flat sensor. We evaluate VIE for lenses employing curved image surfaces and planar, monochromatic metasurfaces to show that these new optical technologies can surpass the limit of conventional lenses and yield >100x increase in VIE.

Aluminum-based concurrent photonic and plasmonic energy conversion driven by quasi-localized plasmon resonance.

Plasmon-enhanced sensitive photodetection using plasmonic noble metals has been widely investigated; however, aluminum (Al)-based photoelectric conversion concurrently utilizing photonic and plasmonic approaches is less explored. Here, photodetection driven by quasi-localized plasmon resonance (QLPR) is investigated. Concurrent photonic and plasmonic contributions to strong absorption in the active region require delocalized, slow-propagating resonant electric field to occur around the peripheries of Al nano-structures and depend on the spatial distribution of diffraction efficiencies of all space harmonics. Efficiency limits are shown to be largely determined by the spatial degrees of freedom and the associated traveling distances of hot electrons during carrier transport. With strong absorption and relatively high reaching-emission probabilities structured in the same region, the measured responsivity and the external quantum efficiency of the fabricated device at 638.9 nm are 4.1889 µA/mW and 0.8129% at -0.485 V, respectively. Our results provide physical insights into related problems and may offer a route to more efficient, hot-carrier based photoelectric conversion devices.