Self-phasing due to spatial mode selection in a two-element passively coupled fiber laser is studied. We find that the addition of a second supermode in a coupled resonator results in a 90% increase in the average output power and nearly π/2 radians of passive phase adjustment versus applied phase errors between the gain elements. These results require a phase of zero (modulo 2π) between the beams in the external cavity. These findings are supported by an eigenmode analysis of the resonator and show that beam recycling is a useful resonator design feature but must be appropriately implemented to obtain beneficial results.We develop and implement a new inverse computational framework for designing photonic elements with one or more high-Q scattering resonances. The approach relies on solving for the poles of the scattering matrix, which mathematically amounts to minimizing the determinant of the matrix representing the Fredholm integral operator of the electric field with respect to the permittivity profile of the scattering element. We apply the method to design subwavelength gradient-permittivity structures with multiple scattering resonances and quality factors as high as 800. We also find the spectral scattering cross sections are consistent with Fano lineshapes. The compact form and computational efficiency of our formalism suggest it can be an effective tool for designing Fano-resonant structures with multiple high-Q resonances for applications such as frequency mixing and conversion.Independent component analysis (ICA) is a general-purpose technique for analyzing multi-dimensional data to reveal the underlying hidden factors that are maximally independent from each other. We report the first photonic ICA on mixtures of unknown signals by employing an on-chip microring (MRR) weight bank. The MRR weight bank performs so-called weighted addition (i.e., multiply-accumulate) operations on the received mixtures, and outputs a single reduced-dimensional representation of the signal of interest. We propose a novel ICA algorithm to recover independent components solely based on the statistical information of the weighted addition output, while remaining blind to not only the original sources but also the waveform information of the mixtures. We investigate both channel separability and near-far problems, and our two-channel photonic ICA experiment demonstrates our scheme holds comparable performance with the conventional software-based ICA method. Our numerical simulation validates the fidelity of the proposed approach, and studies noise effects to identify the operating regime of our method. The proposed technique could open new domains for future research in blind source separation, microwave photonics, and on-chip information processing.Some imaging techniques reduce the effect of optical aberrations either by detecting and actively compensating for them or by utilizing interferometry. A microscope based on a Mach-Zehnder interferometer has been recently introduced to allow obtaining sharp images of light-transmitting objects in the presence of strong aberrations. However, the method is not capable of imaging microstructures on opaque substrates. In this work, we use a Michelson interferometer to demonstrate imaging of reflecting and back-scattering objects on any substrate with micrometer-scale resolution. The system is remarkably insensitive to both deterministic and random aberrations that can completely destroy the object's intensity image.Chiral photodetectors, optoelectronic devices that can detect circularly polarized light (CPL), have attracted much attention as building blocks of next-generation information technology. However, their performance has been severely limited by the tradeoff between the external quantum efficiency (ηE) and the dissymmetry factor of photocurrent, the latter typically being limited by the small dissymmetry factor of absorption (gA). This work numerically demonstrates that a circular polarization-sensitive organic photodetector (CP-OPD) based on a chiral plasmonic nanocavity can achieve both high ηE and gA. The design of the chiral nanocavity, featuring a circular dichroic plasmonic mode with a high photonic density of states in the subwavelength thick photoactive layer, is decoupled with that of the photoactive layer, which enables the independent control of the circular dichroic and photon-to-charge conversion properties. By investigating the interaction between CPL and the molecules constituting the photoactive layer, a design principle of the plasmonic CP-OPD is established, resulting in superior performance with ηE = 23.8 % and gA = 1.6.We theoretically investigate temporal dynamics of the second order cross correlation function at zero delay time (G12(2)(t)) and spectral entanglement of two photons emitted from an atomic three-level cascade. In Heisenberg's picture, a closed set of quantum kinetic equations of motion for G12(2)(t) is derived within density matrix formalism with cluster expansion rule. G12(2)(t) shows qualitatively distinctive features depending on the spectral entanglement of two photons. Although incoherent photon pairs generated from spontaneous radiation of the excited electron are not entangled, their correlation and anti-correlation properties can be found in G12(2)(t) depending on the radiative decay rates. In the coherent excitation regime where the light emitter is located in a high Q-cavity, and its atomic polarizations are predominantly initialized, spectral entanglement between two coherent photons is established. We show that G12(2)(t) is well fitted by the entanglement criterion by Duan-Giedke-Cirac-Zoller and explain the close relationship between them by means of the optically forbidden transition in the three-level cascade.(Al,In)GaN laser diodes have various relevant applications, especially in projection systems for virtual and augmented reality devices and in optical communication, all requiring fast modulation. This corresponds to pulses in the nanosecond to microsecond range, where a rich longitudinal mode dynamics occurs.  https://www.selleckchem.com/products/sw033291.html  We investigate this spectral-temporal dynamics experimentally with a streak camera system and simulate it using a longitudinal multi-mode rate equation model. We observe an interplay of effects, which have been observed selectively, such as relaxation oscillations, mode competition and inhomogeneous pumping of multiple quantum wells. A mechanism is included in the simulations to model the red-shift of the gain spectrum due to the carrier density in the quantum wells exceeding threshold density, which is amplified by inhomogeneous pumping. Mode competition leads to spectral cycles of the active mode with a noticeable jitter, which is observed in single pulse measurements in comparison to multi pulse averaged measurements where blurring occurs.