Introduction to the special feature: amplify Black voices in optics and photonics.

This multi-journal special issue highlights the work of Black scientists and engineers in optics and photonics to accomplish the goal of engaging the entire optics and photonics community and bring awareness to the quality of their research and contributions to the field.

Adaptive methods of generating complex light arrays.

Structured light arrays of various shapes have been a cornerstone in optical science, driven by the complexities of precise and adaptable generation. This study introduces an approach using a spatial light modulator (SLM) as a generator for these arrays. By projecting a holographic mask onto the SLM, it functions simultaneously as an optical convolution device, focusing mechanism, and structured light beam mask. Our approach offers unmatched versatility, allowing for the experimental fabrication of traditional beam arrays like azimuthal Laguerre-Gaussian (LG), Bessel-Gaussian (BG), and Hermite-Gauss (HG) in the far-field. Notably, it has enabled a method of generating Ince-Gauss (IG) and LG radial mode beam arrays using a convolution solution. Our system provides exceptional control over array periodicity and intensity distribution, bypassing the Talbot self-imaging phenomenon seen in traditional setups. We provide an in-depth theoretical discussion, supported by empirical evidence, of our far-field results. This method has vast potential for applications in optical communication, data processing, and multi-particle manipulation. It paves the way for rapid generation of structured light with high spatial frequencies and complex shapes, promising transformative advances in these domains.

Scoring-Based Genetic Algorithm for Wavefront Shaping to Optimize Multiple Objectives.

We present a scoring-based genetic algorithm (SBGA) for wavefront shaping to optimize multiple objectives at a time. The algorithm is able to find one feasible solution despite having to optimize multiple objectives. We employ the algorithm to generate multiple focus points simultaneously and allocate their intensities as desired. We then introduce a third objective to confine light focusing only to desired targets and prevent irradiation in neighboring regions. Through simulations and experiments, we demonstrate the algorithm's ease of implementation and flexibility to control the search direction. This algorithm can potentially be applied to improve biomedical imaging, optogenetics, and optical trapping.

Mode control in a multimode fiber through acquiring its transmission matrix from a reference-less optical system.

A simple imaging system, together with complex semidefinite programming, is used to generate the transmission matrix (TM) of a multimode fiber. Once the TM is acquired, we can modulate the phase of the input signal to induce strong mode interference at the fiber output. The optical design does not contain a reference arm, no internal reference signal is used, and no interferometric measurements are required. We use a phase-only spatial light modulator to shape the profile of the propagating modes, and the output intensity patterns are collected. The semidefinite program uses a convex optimization algorithm to generate the TM of the optical system using intensity only measurements. This simple, yet powerful, method can be used to compensate for modal dispersion in multimode fiber communication systems. It also yields great promise for the next generation biomedical imaging, quantum communication, and cryptography.

Controlling Light Transmission Through Highly Scattering Media Using Semi-Definite Programming as a Phase Retrieval Computation Method.

Complex Semi-Definite Programming (SDP) is introduced as a novel approach to phase retrieval enabled control of monochromatic light transmission through highly scattering media. In a simple optical setup, a spatial light modulator is used to generate a random sequence of phase-modulated wavefronts, and the resulting intensity speckle patterns in the transmitted light are acquired on a camera. The SDP algorithm allows computation of the complex transmission matrix of the system from this sequence of intensity-only measurements, without need for a reference beam. Once the transmission matrix is determined, optimal wavefronts are computed that focus the incident beam to any position or sequence of positions on the far side of the scattering medium, without the need for any subsequent measurements or wavefront shaping iterations. The number of measurements required and the degree of enhancement of the intensity at focus is determined by the number of pixels controlled by the spatial light modulator.

Single particle plasmon spectroscopy of silver nanowires and gold nanorods.

The excitation of surface plasmons in individual silver nanowires and gold nanorods is investigated by means of high-resolution electron energy loss spectroscopy in a transmission electron microscope. The transverse and longitudinal modes of these nanostructures are resolved, and the size variation of the plasmon peaks is studied. The effect of electromagnetic coupling between closely spaced nanoparticles is also observed. Finally, the relation between energy-loss measurements and optical spectroscopy of nanoparticle plasmon modes is discussed.