Controlling the sign of chromatic dispersion in diffractive optics with dielectric metasurfaces (1701.07178v2)

Abstract: Diffraction gratings disperse light in a rainbow of colors with the opposite order than refractive prisms, a phenomenon known as negative dispersion. While refractive dispersion can be controlled via material refractive index, diffractive dispersion is fundamentally an interference effect dictated by geometry. Here we show that this fundamental property can be altered using dielectric metasurfaces, and we experimentally demonstrate diffractive gratings and focusing mirrors with positive, zero, and hyper negative dispersion. These optical elements are implemented using a reflective metasurface composed of dielectric nano-posts that provide simultaneous control over phase and its wavelength derivative. In addition, as a first practical application, we demonstrate a focusing mirror that exhibits a five fold reduction in chromatic dispersion, and thus an almost three times increase in operation bandwidth compared to a regular diffractive element. This concept challenges the generally accepted dispersive properties of diffractive optical devices and extends their applications and functionalities.

Controlling Chromatic Dispersion in Diffractive Optics with Dielectric Metasurfaces

The paper "Controlling the sign of chromatic dispersion in diffractive optics with dielectric metasurfaces" by Arbabi et al. explores the manipulation of chromatic dispersion characteristics in diffractive optical devices through the application of dielectric metasurfaces. These metasurfaces are composed of amorphous silicon nano-posts on reflective layers, which allow unprecedented control over phase and dispersion characteristics of diffractive optical elements.

Summary of Findings

Central to the authors' findings is the dielectric metasurfaces' ability to enable positive, zero, and hyper-negative dispersion in diffractive gratings and focusing mirrors. Conventional diffractive optics typically exhibit negative dispersion due to their interference geometry; however, this research demonstrates the possibility to alter this fundamental property through structured dielectric metasurface layers.

The paper details the design and experimental demonstration of optical elements utilizing these metasurfaces to achieve targeted dispersion regimes. By leveraging metasurfaces that allow for independent control of phase and dispersion, the typical dispersion limitations inherent in conventional diffractive optics are effectively challenged. The metasurfaces also have applications in creating reflective focusing mirrors with significantly reduced chromatic dispersion, thereby increasing their operational bandwidth by nearly a factor of three compared to a standard diffractive element.

Implications and Future Research

The implications of the control over chromatic dispersion through dielectric metasurfaces are profound both practically and theoretically. The reduced chromatic aberration in focusing mirrors suggests the potential for more versatile optical system designs in imaging and communications, where bandwidth and precise control over light paths are critical.

Theoretically, this work opens avenues for further exploration of complex optical systems that could leverage metasurfaces' phase and dispersion-modulating capabilities for enhanced functionality. These systems could blur the line between refractive and diffractive elements, combining the advantages of both systems to create entirely new categories of optical devices.

Future research may focus on further refining the precision of metasurface phase control and exploring additional meta-atom designs that allow for broader coverage of the desired region in the phase-dispersion plane. This could facilitate the development of even more complex diffractive elements with tailored dispersion for specific applications.

In summary, the research by Arbabi et al. marks a significant step forward in the manipulation of light behavior through advanced material design, placing metasurfaces at the forefront of optical technology innovations.