Complex wavefront engineering with disorder-engineered metasurfaces (1706.08640v1)

Abstract: Recently, complex wavefront engineering with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics. These capabilities include extended volume, aberration-free focusing and subwavelength focusing via evanescent mode coupling. However, translating these capabilities to useful applications has remained challenging as the input-output characteristics of the disordered media ($P$ variables) need to be exhaustively determined via $O(P)$ measurements. Here, we propose a paradigm shift where the disorder is specifically designed so that its exact characteristics are known, resulting in an a priori determined transmission matrix that can be utilized with only a few alignment steps. We implement this concept with a disorder-engineered metasurface, which exhibits additional unique features for complex wavefront engineering such as an unprecedented optical memory effect range, excellent stability, and a tailorable angular scattering profile.

• The paper introduces disorder-engineered metasurfaces with known transmission matrices for precise optical wavefront manipulation.
• Experimental demonstrations reveal high-NA focusing up to 0.95 and wide field-of-view imaging, surpassing conventional adaptive optics limits.
• These findings pave the way for advanced optical systems in microscopy, lithography, and free-space communication through simplified system design.

Complex Wavefront Engineering with Disorder-Engineered Metasurfaces

The paper "Complex wavefront engineering with disorder-engineered metasurfaces" presents a novel approach to optical wavefront manipulation by leveraging disorder-engineered metasurfaces. This research contributes to the field of optics and nanophotonics by proposing a paradigm shift from conventional disordered media to purposefully designed metasurfaces with pre-determined transmission matrices. This allows for efficient and precise control over complex optical wavefronts.

Key Contributions and Methodology

The central advancement offered by this paper is the introduction of disorder-engineered metasurfaces, which are fabricated with known characteristics to achieve specific optical objectives. Unlike traditional disordered media, which require exhaustive measurements to characterize their input-output relationships, these metasurfaces possess a known a priori transmission matrix. This drastically simplifies the system setup, reducing it to a simple alignment problem.

The authors equipped the metasurfaces with a 2D array of nano-scatterers designed to provide broad control over optical phase delays. The metasurfaces demonstrate highly isotropic scattering profiles over a maximum spatial bandwidth, confirmed by experimental scattering profile measurements and full exploitation of the optical memory effect. These features enable enhanced stability and performance in optical wavefront engineering tasks, such as focusing and imaging.

Experimental Demonstrations and Results

The paper showcases several experimental validations, demonstrating the effectiveness of disorder-engineered metasurfaces:

1. High-NA Optical Focusing: The research exhibited high numerical aperture (NA) focusing capabilities across an extended volume, surpassing the conventional limitations of adaptive optics in terms of spatial resolution and control fidelity. The metasurfaces achieved NA values up to 0.95, a notable achievement given the limited control offered by typical SLMs.
2. Wide Field-of-View Imaging: The metasurface-assisted microscope demonstrated high-resolution, wide field-of-view (FOV) fluorescence imaging. By effectively controlling a large transmission matrix, the system achieved imaging performance comparable to high NA objective lenses over a vastly extended FOV.

The metasurface demonstrated a significant number of resolvable spots, exceeding $10^8$ with substantial contrast improvements, indicating the potential for highly precise and flexible optical manipulation applications.

Implications and Future Research

The implications of this research span both theoretical and practical domains. Theoretically, it challenges the traditional view of optical 'randomness', presenting engineered disorder as a viable tool for precision wavefront control. Practically, it opens avenues for improved design of optical systems in various applications, such as advanced microscopy techniques, optical lithography, and free-space communication systems.

Future developments may focus on expanding the metasurface designs to operate over broader wavelength ranges and integrating them into more compact, scalable optical platforms. Additionally, the application of such metasurfaces in emerging fields like augmented reality and biological imaging will likely be explored further.

Overall, this research marks a significant step forward in the use of structured disorder in optical engineering, providing new capabilities for controlled, high-resolution wavefront manipulation across diverse application areas.