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Polarization manipulation is essential in photonic integrated circuits and has numerous applications in various fields, such as optical communication, nonlinear optics, and quantum optics. Advances in nanofabrication have enabled the integration of subwavelength‐structured metamaterials on optical waveguides, providing unprecedented optical manipulation capabilities beyond classical waveguide‐based architectures. In this paper, the polarization space is demonstrated to be fully manipulated by a dielectric metamaterial composed of nanoholes and nanoslots. This approach offers competitive performances for key polarization components, including the polarizer, polarization beam splitter, and polarization‐splitter‐rotator, while maintaining ultra‐compact coupling regions of 18×1 µm2, 16×1.1 µm2, and 13×1 µm2 respectively. The devices are designed by manipulating the phase and amplitude of all possible eigenmodes supported in the waveguide, which is inherently scalable and versatile for on‐chip mode and wavefront manipulation. The unique properties of metamaterials provide powerful tools for on‐chip polarization manipulation and offer new possibilities for the development of compact and high‐performance photonic integrated circuits. [ABSTRACT FROM AUTHOR]

The polarization beam splitter (PBS) is a pivotal element in the polarization management of free-space optical instruments and systems. Photonic integrated circuits for sensing, imaging, communications, and quantum-information processing also have needs for monolithically integrated PBSs with an ultra-broad optical bandwidth. In this paper, a novel silicon nanophotonic PBS inspired by the crystalline Glan-Thompson prism but implemented with silicon subwavelength-grating (SWG) metamaterials is presented. Due to the tailored artificial anisotropy of SWGs, the meta-prism functions like a thin-film reflector or a waveguide crossing for different polarizations. Thus, the incident light can be steered with strong polarization selectivity and negligible wavelength dependence. Unlike conventional PBS designs, the routing of polarized light is enabled by the wavelengthindependent total internal reflection in anisotropy-engineered effective media, thereby breaking the bandwidth limit. The device footprint is as small as ≈15 x 7 υm². Low insertion losses of 0.6-1.7 dB and high extinction ratios of 20-30 dB are experimentally achieved spanning a record broad bandwidth of over 415 nm, ranging from 1.26 to 1.675 μm wavelength. These results represent, to the best of their knowledge, the most broadband integrated PBS ever demonstrated to date. [ABSTRACT FROM AUTHOR]

One of the most fundamental quantum random number generators is implemented with light impinging onto a beam splitter, and two single photon detectors at its output. Often, this generator is described as 'a photon which takes one or other path towards a detector'. The input state of light in conjunction with the detector response is relevant for the amount, the pattern, and the correlation of the generated clicks. Only a fraction of all generator outcomes, the min-entropy, can be used as a further resource for true randomness. This paper addresses the difference in the common description with incoming single photons and the often implemented scheme with a weak coherent light source, such as an attenuated laser. For this very fundamental and widely used configuration the amount of usable entropy is compared. If single photons from an anti-bunched light source are supplied, the amount of entropy is higher than for the case of a supplied coherent state - although the latter can be arbitrarily bright unlike the single photon source. [ABSTRACT FROM AUTHOR]

For the miniaturization of optical devices, surface plasmon polaritons (SPPs) have been widely utilized due to their outstanding confinement and field-enhancement characteristics. Analyzing a spectrum of optical signals and splitting certain regions of the spectrum range within a submicrometer-scale structure are demanded for optical integrated systems. In this paper, a novel type of dichroic surface plasmon launcher that can switch the launching direction according to incident polarization states is demonstrated. Compared to the previously reported plasmonic dichroic splitters, the proposed schemes do not use any asymmetric geometry for directional launching. Hence, the direction of guided SPPs can be interchanged according to the polarization state. Such characteristics will be helpful to design switchable plasmonic devices that can be applied to active plasmonic integrated circuits. [ABSTRACT FROM AUTHOR]

The polarization beam splitter (PBS) is an essential component in the polarization diversity circuit to overcome the strong polarization dependence of silicon nanophotonic devices. Among various PBS structures, the asymmetrical directional couplers (ADCs) are most commonly used due to the best overall performances. However, it is still challenging to realize an on‐chip silicon PBS with a small footprint, low loss, high extinction ratio, and, especially, broad bandwidth, simultaneously. The working bandwidth is limited for ADCs, since the wavelength difference will introduce deviations to both the effective indices and the coupling strength, which would distort the phase‐matching property and the optimal coupling length. In this paper, an on‐chip silicon PBS is proposed and demonstrated using "effective medium anisotropy" instead of "configuration asymmetry" to break the bandwidth bottleneck. The metamaterials with engineered anisotropy and dispersion are utilized to form a hetero‐anisotropic slab. For TM polarization, the slab performs as a multi‐mode interference coupler, while for TE polarization, the slab performs as two isolated waveguides. The fabricated PBS shows low loss <1 dB, high extinction ratio >20 dB, and a record working bandwidth >200 nm, with a footprint as small as 12.25 × 1.9 µm2. An ultra‐broadband on‐chip silicon polarization beam splitter based on hetero‐anisotropic metamaterials is proposed and demonstrated. Subwavelength grating metamaterials are utilized to engineer anisotropy and dispersion. The fabricated device shows low losses <1 dB, high extinction ratios >20 dB, and a record working bandwidth >200 nm. [ABSTRACT FROM AUTHOR]