Investigations into optical phenomena associated with nonlinear magnetoelectric effects are attracting growing attention within the scientific community. Technologies constantly demand new materials capable of exhibiting precise and controllable responses to external electromagnetic fields. In this context, the optics of such materials is of remarkable importance. Here, working in a lossless and non-dispersive regime, electromagnetic wave propagation in materials presenting linear and nonlinear optical coefficients is investigated. We expand the discussion of the roles of nonlinear coefficients by examining special cases in which the contribution of the magnetoelectric optical coefficients $α_{ij}$, $β_{ijk}$, and $γ_{ijk}$ to birefringence and nonreciprocal phenomena is elucidated. Notably, expressions that directly connect the magnetoelectric coefficients to the refractive indices of the medium are fully derived. These expressions enable the direct measurement of all components of each nonlinear magnetoelectric coefficient, providing an advancement over previous works. This development bridges theoretical models with experimental applications, offering possibilities for the optical characterization of magnetoelectric effects.
We show that the refractive index modification photoinduced in a biased nonlinear photorefractive crystal can be accurately measured and controlled by means of a background incoherent illumination and an external electric field. The proposed easy-to-implement method is based on the far-field measurement of the diffraction patterns of a laser beam propagating through a self-defocusing medium undergoing spatial self-phase modulation. For various experimental conditions, both saturation intensity and maximum refractive index modification have been measured. We also clearly evidence and characteri…
We study the negative refractive index in cubic noncentrosymmetric superconductors. We consider the Maxwell equations under the Meissner effect, and magnetoelectric effect arising due to broken inversion symmetry. We derive dispersion relations of electromagnetic waves, and show that the refractive index becomes negative at frequencies just below the Higgs gap. We find that the chiral mechanism of the negative refractive index, which is usually discussed in chiral materials with negative permittivity can be applied to superconductors with positive permittivity by replacing the plasma gap with …
It has been demonstrated that dynamic refractive index modulation, which breaks time-reversal symmetry, can be used to create on-chip non-reciprocal photonic devices. In order to achieve amplitude non-reciprocity, all such devices moreover require modulations that break spatial symmetries, which adds complexity in implementations. Here we introduce a modal circulator, which achieves amplitude non-reciprocity through a circulation motion among three modes. We show that such a circulator can be achieved in a dynamically-modulated structure that preserves mirror symmetry, and as a result can be i…
Metallic nanostructures exhibit strong nonlinear-optical response at surface plasmon resonances, where the light-matter coupling efficiency is enhanced. An active modulation of this response can be realized by means of an external magnetic field. Here we utilize a nonlinear magneto-refractive effect in spintronic multilayer antennas to achieve a resonant 20\% modulation in second harmonic generation (SHG) in the mid-infrared. We discuss mechanisms of this modulation and show that it cannot be explained by an unequal enhancement of the electromagnetic field in the two spin states of the multila…
In this work, we propose a novel method for continuous real-time measurement of the dynamics of the nonlinear refractive index n2. This is particularly important for characterizing phenomena or materials (such as biological tissues, gases and other compounds) whose nonlinear behavior or structure varies rapidly with time. The proposed method ingeniously employs two powerful tools: the spectral broadening induced by self-phase modulation and the real-time spectral analysis using the dispersive Fourier transformation. The feasibility of the technique is experimentally demonstrated, achieving hig…
The development of optically active area consisting of organic molecules are essential for the devices like optical switches and waveguides, as it can be easily maneuvered by the application of suitable electromagnetic (EM) waves. In this article, we report the development of a photoactive surface by the deposition of a single layer of Langmuir-Blodgett (LB) film of a novel H-shaped liquid crystal (HLC) molecule. The synthesized HLC molecules possess azo-groups and nitro-groups. The azo-group can be isomerized (trans-cis transformation) by irradiating them with ultraviolet (UV) light. The nitr…
Electrically-tunable optical properties in materials are desirable for many applications ranging from displays to lasing and optical communication. In most two-dimensional thin-films and other quantum confined materials, these constants have been measured accurately. However, the optical constants of single wall nanotubes (SWCNT) as a function of electrostatic tuning are yet to be measured due to lack of electronic purity and spatial homogeneity over large areas. Here, we measure the basic optical constants of ultrathin high-purity (>99%) semiconducting single wall carbon nanotube (s-SWCNT) fi…
We show that the emission of broad area semiconductor amplifiers and lasers can be efficiently stabilized by introducing, two-dimensional periodic modulations simultaneously on both the refractive index and the pump (gain-loss) profiles, in the transverse and longitudinal directions. The interplay between such index and gain-loss modulations efficiently suppresses the pattern forming instabilities, leading to highly stable and bright narrow output beams from such sources. We also determine the stabilization performance of the device as a function of pump current and linewidth enhancement facto…
We present detailed experimental study on noise-seeded intermodal modulation instability (IM-MI) in normal dispersion region of a conventional step-index fiber. The sharp refractive index contrast between core and cladding leads to large group velocity mismatch between the spatial modes, coaxing to efficient IM-MI and generation of multiple spectral peaks along with Raman peaks. Evolution of the spectrum with pump powers and fiber lengths are observed. Experimental findings are well supported with the theoretical framework based on bimodal-MI model considering the distinct dispersion parameter…
High-index dielectric materials are in great demand for nanophotonic devices and applications, from ultrathin optical elements to metal-free sub-diffraction light confinement and waveguiding. Here we show that chalcogenide topological insulators are particularly apt candidates for dielectric nanophotonic architectures in the infrared spectral range by reporting metamaterial resonances in chalcogenide crystals sustained well inside the mid-infrared, choosing Bi$_2$Te$_3$ as case study within this family of materials. Strong resonant modulation of the incident electromagnetic field is achieved t…
Typically, strong gain saturation and gain dynamics play a crucial role in semiconductor laser mode-locking. While there have been several investigations of the ultrafast gain dynamics in vertical-external-cavity surface-emitting lasers (VECSELs), little is known about the associated refractive index changes. Yet, such refractive index changes do not only have a profound impact on the pulse formation process leading to self-phase modulation, which needs to be compensated by dispersion, but they are also of particular relevance for assessing the feasibility of Kerr-lens mode-locking of VECSELs.…
We demonstrate ultrasound detection with 500-$μ\mathrm{m}$-diameter photonic-crystal slab (PCS) sensors fabricated from CMOS-compatible technology. An ultrasound signal impinging a PCS sensor causes a local modulation of the refractive index (RI) of the medium (water) in which the PCS is immersed, resulting in a periodic spectral shift of the optical resonance of the PCS. The acoustic sensitivity is found to scale with the index sensitivity $S$ and quality factor $Q$. A noise equivalent pressure (NEP) of 650 Pa with averaging (7.4 Pa$/\sqrt{\mathrm{Hz}}$) and relative wavelength shifts of up t…
Vanadium Dioxide (VO2) is a strongly correlated material, which exhibits insulator to metal transition at ~68 C along with large resistivity and infrared optical reflectance modulation. In this work, we use atmospheric pressure thermal oxidation of Vanadium to synthesize VO2 films on glass and ITO coated glass substrates. With the optimized short oxidation durations of 2 min and 4 min, the synthesized VO2 film shows high optical reflectance switching in long-wavelength infrared on glass substrates and mid-wavelength infrared on ITO coated glass substrates, respectively. Peak reflectance switch…
Real photon pairs can be created in a dynamic cavity with periodically modulated refractive index of the constituent media or oscillating boundaries. This effect is called Dynamic Casimir effect (DCE), which represents one of the most amazing predictions of quantum field theory. Here, we investigate DCE in a dynamic one-dimensional photonic crystal system with both temporal and spatial modulation of the refractive index profile. Such a system can resonantly generate photons at driving frequencies equal to even or odd integer times of that of the fundamental cavity mode governed by the symmetry…
We propose a novel physical mechanism based on periodic non-Hermitian potentials to efficiently control the complex spatial dynamics of broad-area lasers, particularly in Vertical-Cavity Surface-Emitting Lasers (VCSELs), achieving a stable emission of maximum brightness. Radially dephased periodic refractive index and gain-loss modulations accumulate the generated light from the entire active layer and concentrate it around the structure axis to emit narrow, bright beams. The effect is due to asymmetric-inward radial coupling between transverse modes, for particular phase differences of the re…
We provide a numerical proof of concept of a stabilization mechanism for BAS laser sources. The scheme is based on the simultaneous introduction of in-phase two-dimensional modulations on the refractive index and pump (gain). We numerically proof total stabilization in BAS laser sources, both in space and time. We also examine the interplay between the index and gain modulations and the effect of the slow relaxation of carriers on the stabilization performance.
Atomically thin transition metal dichalcogenides (TMDCs) present a promising platform for numerous photonic applications due to excitonic spectral features, possibility to tune their constants by external gating, doping, or light, and mechanical stability. Utilization of such materials for sensing or optical modulation purposes would require a clever optical design, as by itself the 2D materials can offer only a small optical phase delay - consequence of the atomic thickness. To address this issue, we combine films of 2D semiconductors which exhibit excitonic lines with the Fabry-Perot resonat…
We theoretically investigate the use of Rayleigh surface acoustic waves (SAWs) for refractive index modulation in optical waveguides consisting of amorphous dielectrics. Considering low-loss Si$_3$N$_4$ waveguides with a standard core cross section of 4.4$\times$0.03 $μ$m$^2$ size, buried 8 $μ$m deep in a SiO$_2$ cladding we compare surface acoustic wave generation in various different geometries via a piezo-active, lead zirconate titanate film placed on top of the surface and driven via an interdigitized transducer (IDT). Using numerical solutions of the acoustic and optical wave equations, w…
Dynamic analysis of refractive index evolution and diffraction properties during single-photon polymerization of photopolymers for micro-optical applications
