Modulation Of Linear Refractive Index Research Articles

Quasi-soliton control in optical lattices with longitudinal exponentially modulation

The dynamical evolution of one-dimensional quasi-soliton in Kerr-type linear-nonlinear optical lattices with the exponential asymptotically longitudinal modulation is investigated. The optical lattice features both the transverse linear refractive index modulation and the nonlinear coefficient periodically modulation. The analytical solutions of the integral beam center, the mean square of the beam width, and the critical incident angle are obtained by adopting the effective particle approach. The dynamical trapping and switching phenomena have been observed. Moreover, the introduction of the longitudinal modulation improves greatly the mobility of the soliton. The propagation states of the quasi-soliton can be controlled by varying a variety of parameters, such as the depths of the linear nonlinear lattices, the form factor and the incident angle of soliton, as well as the asymptotic rate of longitudinal modulation. Thus our results offer a new opportunity for the all optical manipulation of light beam.

Preface

The 22nd Russian Youth Conference on Physics of Semiconductors and Nanostructures, Opto- and Nanoelectronics (RYCPS) was held in Saint Petersburg on November 23 – 27, 2020. It was organized by Peter the Great St. Petersburg Polytechnic University.The program of the Conference included semiconductor technology, heterostructures with quantum wells and quantum dots, opto- and nanoelectronic devices and new materials. Given the restrictions on meetings of a large number of people associated with COVID-19, the conference organizing committee decided to hold it in a virtual format. The oral sessions were held on the Zoom platform, and the poster session was organized using the Miro online whiteboard and the Skype platform. This provided an opportunity for valuable discussions between the conference participants and experienced scientists.The conference included two invited talks given by leading scientists, devoted to actual problems and major advances in physics and technology. The keynote speakers were Mikhail Nestoklon from Ioffe Institute (presentation “Fine structure of excitons in quantum dots based on Pb chalcogenides”) and Sergey Kukushkin from Institute of Problems of Mechanical Engineering (presentation “A new method of controlled synthesis of nanomaterials for micro- and optoelectronics. Thermodynamics and kinetics of nanoscale synthesis of single-crystal silicon carbide on silicon and its unique properties”). Students, graduate and postgraduate students presented their results on plenary and poster sessions. The total number of accepted papers published in Russian (the official conference language) was 105. Here we publish 24 of them in English.Like previous years, the participants were involved in the competition for the best report. Certificates and cash prizes were awarded to a number of participants for the presentations selected by the Program Committee. Aidar Galimov, a postgraduate student at Ioffe Institute (Saint Petersburg), received the E.F. Gross Prize for the best presentation in the field of semiconductor optics for the report “Investigation of the single photons indistinguishability in InAs/GaAs quantum dots”. Mikhail Rakitskii (Alferov University, Saint Petersburg) was awarded for the best presentation among students with a report “Anomalous Hall effect in semiconductors with zero spin polarization”. Ivan Makhov (Peter the Great St. Petersburg Polytechnic University) was awarded for the best presentation among postgraduate students with a report “Linear refractive index modulation induced by electric current in GaAs/AlGaAs quantum wells”. Works with potential applications were recommended for participation in the following competition for support from the Russian Foundation for Assistance to Small Innovative Enterprises in Science and Technology.The conference was supported by the Russian Foundation for Basic Research, the Ministry of Science and Higher Education of the Russian Federation (Program “5–100”) and Tydex LLC, St. Petersburg.The official conference website is http://www.semicond.ru/conf2020 Editors R.A. Suris L.E. Vorobjev D.A. Firsov V.A. Shalygin

Modulational instability in asymmetric nonlocal media with optical lattices

A theoretical investigation of the modulational instability (MI) and propagation properties of light in asymmetric nonlocal media with the effect of lattice depth. By using the linear stability analysis, the generic properties of the MI gain spectrum are demonstrated for the asymmetric response and periodic linear refractive index modulation (optical lattices). The impact of the nonlocal parameter and the lattice depth are investigated. We have seen that the magnitude of the MI gain decreases when the nonlocal parameter increases, and increases slightly when the lattice depth increases. Through numerical simulations, we obtain that controllable soliton propagation in asymmetrical nonlocal media can be achieved.

Unbreakable PT symmetry of exact solitons in inhomogeneous nonlinear optical media

We demonstrate analytically and numerically the existence of exact solitons in the form of double kink and fractional transform, supported by a symmetric transversally modulated defocusing nonlinearity acting as a pseudopotential combined with an antisymmetric gain–loss profile. We explain here that the PT symmetry is never broken in the dynamical system under study, even in the absence of any symmetric modulation of linear refractive index, and the transversally modulated defocusing nonlinearity comes in the way as a requirement to establish the ensuing PT symmetry.

Formula omitted]symmetric nonlinear optical lattice: Analytical solutions

Localized and periodic solutions for the nonlinear Schrödinger equation with spatially modulated nonlinearity are found. A linear stability analysis corroborated by direct numerical simulation reveals that the regions of stability of these solutions can be controlled by tuning the values of real and imaginary parts of the linear refractive index modulation profile as well as by tuning the real part of nonlinearly modulated spatial distribution. In particular, the role played by the competing gain and loss parameter as well as by the parameter of periodic spatial distribution towards the magnitude of the stability domains is reported.

Soliton controlling and steering in asymmetric nonlocal media with optical lattices

Existence and stability of the fundamental and higher-order solitons, which exist in nonlinear media with asymmetric response and periodic linear refractive index modulation, are presented. It is found that the existence of solitons results in the balance between linear refractive index modulation (optical lattices) and nonlinear refractive index induced by incident optical field. In addition, Dynamical properties of fundamental mode solitons are also investigated in detail, and may be applied in the fields of soliton controlling and steering.

Solitons in Gaussian potential with spatially modulated nonlinearity

We investigated theoretically the existence, stability and propagation dynamics of fundamental and dipole solitons in the potential featuring locally Gaussian modulation of linear refractive index and out-of-phase nonlinearity. Fundamental solitons are stable in the moderate power region and the stability window shrinks with the depth of nonlinearity modulation, while there exist several discrete narrow stable windows for the dipole solitons. Also, a power-dependent shape transformation is found in the high power region for deep enough nonlinear modulation. The transverse mobility of solitons launched with a tilt angle was also discussed, and the results show the critical tilt angles for soliton deflecting from the channel increase with a decrease of the propagation constant. For the low energy soliton, only part of the soliton would keep oscillating in the channel and the other part would deflect away even if the tilt angle is smaller than the critical value.

Lattice solitons inPT-symmetric mixed linear-nonlinear optical lattices

We report the existence and stability of lattice solitons in parity-time ($\mathcal{PT}$)-symmetric mixed linear-nonlinear optical lattices in Kerr media. We focus on studying the characteristic effects on soliton propagation in the semi-infinite gap if we consider different amplitudes of real and imaginary parts of both the linear refractive index modulation profile and of periodic nonlinearity-modulation spatial distribution. It was found that the combination of $\mathcal{PT}$-symmetric linear and nonlinear lattices can stabilize lattice solitons and can provide unique soliton properties. It is revealed that the parameters of the linear lattice periodic potential play a significant role in controlling the extent of the stability domains and that the lattice solitons can stably propagate only in the low-power regime.

Solitons in thermal media with periodic modulation of linear refractive index

We address the existence and properties of solitons in thermal media with periodic modulation of linear refractive index. Many kinds of solitons in such optical lattices, including symmetric and antisymmetric lattices, are found under different conditions. We study the influence of the refractive index difference between two different layers on solitons. It is also found that there do not exist cutoff value of propagation constant and soliton power for shifted lattice solitons. In addition, the solitons launched away from their stationary position may propagate without oscillation when the confinement from lattices is strong.

Stability conditions for moving dissipative solitons in one- and multidimensional systems with a linear potential

We analyze stability of moving dissipative solitons in the one-, two, and three-dimensional cubic-quintic complex Ginzburg-Landau equations in the presence of a linear potential (linear refractive index modulation). The expressions of stability conditions and propagation trajectory of solitons are derived by means of a generalized variational approximation. Predictions of the variational analysis are fully confirmed by direct numerical simulations. The results have potential applications to using spatial dissipative solitons in optics as individually addressable and shift registers of the all-optical data processing systems.

The pulsating propagation of spatial soliton in strongly nonlocal optical lattice

Based on the nonlocal nonlinear Schrdinger equation, which is the evolution equation of propagation of spatial soliton in the nonlocal media, the pulsating propagation of spatial solitons in one-dimensional strongly nonlocal optical lattice are researched numerically by the split-step Fourier method. The pulsating propagation period of spatial soliton is analyzed for different parameters of propagation, such as the initial energy of the beam, the nonlocality degree, the modulation degree of lattice, the period of the transverse modulation and the asymptotic rate of the longitudinal modulation of linear refractive index. And the inherent physical mechanisms of pulsating propagation of spatial soliton are discussed for the different parameters of lattice structure. Furthermore, the controllable switching behavior of spatial optical soliton has been achieved in the strongly nonlocal optical lattice with longitudinal modulation of linear refractive index.

Exact spatial soliton solution for nonlinear Schrödinger equation with a type of transverse nonperiodic modulation

In this paper, we analyze (2 + 1)D nonlinear Schrödinger (NLS) equation based on a type of nonperiodic modulation of linear refractive index in the transverse direction. We obtain an exact solution in explicit form for the (2 + 1)D nonlinear Schrödinger (NLS) equation with the nonperiodic modulation. Finally, the stability of the solution is discussed numerically, and the results reveal that the solution is stable to the finite initial perturbations.

Nonlinear refractive index of photo-thermo-refractive glass

Nonlinear properties of a photo-thermo-refractive (PTR) glass are studied and compared with those in fused silica and a conventional optical glass. PTR glass is a new photosensitive medium for high-efficiency phase volume hologram recording which manifests a linear refractive index modulation after exposure to UV radiation followed by thermal treatment. Nonlinear optical properties of PTR glass exposed to femtosecond laser pulses are studied. Diffraction patterns in a propagated laser beam focused in the sample were detected by a CCD, while a nonlinear refractive index was measured by a collinear-orthogonal-polarization-pump-probe (COP3) method. It was found that nonlinear refractive index of PTRG is n 2 = 3.3 × 10 −20 m 2 /W (0.33 ppm cm 2 /GW) which is about the same as for the fused silica. It is important that n 2 in PTR glass does not vary after UV exposure and thermal development.

Tunable Soliton Self-Bending in Optical Lattices with Nonlocal Nonlinearity

We address the phenomenon of soliton self-bending in Kerr-type nonlocal nonlinear media with an imprinted transverse periodic modulation of the linear refractive index. We show that the imprinted optical lattice makes possible to control the mobility of soliton by varying the depth and the frequency of the linear refractive index modulation.