The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
We analyze self-collimation in two-dimensional periodic complex lattices. We consider P-symmetric and PT-symmetric complex lattices with different geometries, where the periodic modulations of both refractive index and gain-loss are either in-phase, or dephased a quarter of wavelength of the modulation. The non-diffractive propagation of light beams is analytically predicted using coupled mode approach...
Flat focusing mirrors without any optical axis have been investigated by two-dimensional chirped photonic crystals. The principle of flat focusing mirror is similar to Veselago flat lens, which allows the beam focusing in the near field. The key idea of 2D chirped PhCs is to provide anomalous diffraction that can restrain a beam spreading and even focus a divergent beam upon reflection. Different...
The microchip lasers, being sources of coherent light, suffer from one serious drawback: low spatial quality of the beam, strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here we propose that specially designed...
Ceramics play an important role in today's science and industry as it can withstand immense heat, mechanical and other hazards. For this reason, there is a constant drive to find new ways to acquire more free-form and sophisticated ceramic structures. Recently, stereolithographic 3D printing of hybrid organic-inorganic photopolymer and subsequent heat treatment was demonstrated to be capable of providing...
Degenerate four-wave mixing (DFWM) oscillators are phase-bistable devices. In such systems, two equivalent states, of equal intensities but opposite phases can be generated. When the cavity Fresnel number is large, different regions of the beam transverse section can have different phases, leading to phase patterns like phase fronts (or domain walls), i.e. ID structures separating regions with opposite...
Microchip lasers (and generally most micro-size lasers, like diode lasers or VCELS) being extremely compact and efficient sources of the coherent radiation, suffer from one drawback: the low spatial quality of the emitted beam. Only at low power emission regimes (close from the generation threshold) the microchip lasers can emit the beams and pulses of a reasonable spatial quality. Every attempt to...
We present the novel dissipative parametric instability which leads to pattern formation and pulse train generation in nonlinear optical systems, under zig-zag modulation of the dissipation applied on symmetrically located spectral regions.
Semiconductor amplifiers typically display self-focusing nonlinearity due to the refraction index dependence on the population inversion. This dependence, characterized by the linewidth enhancement factor, αH ∼ 1.5 – 8 in semiconductor materials, induces multi-transverse mode operation and filamentation that severely deteriorates the beam quality. For semiconductors showing small αH factors, the instability...
Photonic crystals due to their angular bandgaps and quasi-bandgaps can provide spatial (angular) filtering of light. Two-dimensional photonic crystals (photonic structures modulated along the longitudinal and along one transverse dimension) can provide spatial filtering in one one-dimensional, decreasing the beam divergence in one quadrature. Three-dimensional crystals can provide two-dimensional...
Photonic crystal waveguides supporting band gap guided modes hold great potential to tailor the group velocity of propagating light. We propose and explore different wavelength demultiplexer design approaches that utilize slow light concept. By altering the dielectric filling factors of each waveguide segment, one can show that different frequencies can be separated and extracted at different locations...
The recently discovered dissipative parametric instability is presented in the framework of the universal complex Ginzburg-Landau equation. The pattern formation associated with the instability is discussed in connection to the relevant applications in nonlinear photonics especially as a new tool for pulsed lasers design.
There is a new type of parametric instability that was recently theoretically predicted — dissipative Faraday instability. In this work we experimentally demonstrate this new type of instability by successfully achieving mode-locking in a simple configuration. Applying a combination of passive spatial modulation of spectrally dependent loss and group velocity dispersion, we achieve high harmonic mode-locking...
We demonstrate a new mechanism for the suppression of modulation instability in a wide class of spatially distributed nonlinear systems. This is done by a periodic spatio-temporal modulation of the background potential. The phenomenon is general in nature as it is shown on a universal model of Complex Ginzburg-Landau equation, and can be extended to various different systems. The results are demonstrated...
We study propagation light beams in 2D photonic periodic nanostructures with both index and gain/loss modulations. We determine the conditions for complex periodic media with in-phase gain and index modulations to support self-collimation, non-diffractive propagation, with simultaneous non-diffusive broadening of the beam. We also analyze self-collimation in media where index and gain modulations...
Semiconductor lasers are efficient light sources with an important drawback, the lack of an intrinsic mode selection mechanism which leads to spatio-temporal instabilities. The modulation instability that unstabilizes the homogeneous solution can be suppressed by the introduction of spatial modulations in the transverse and longitudinal directions. The present work applies this stabilization technique...
We propose a new type of add-drop Micro ring resonator that is made up of gain and loss materials. In all-dielectric linear systems, light transmission is reciprocal: A symmetric transmission spectrum is observed when an incident source is pumped from one side and output power detected in the other side or vice versa. On the other hand, Parity-time (PT) symmetric optical systems that consist of balanced...
We present the flat focusing mirror - the dielectric mirrors capable to focus and image the narrow beams in reflections. The mirrors are flat, and transversally invariant, i.e. have no optical axis. We consider two different configurations of such mirrors: 1) Bragg-like mirrors, consisting of structure of specially designed dielectric layers; 2) periodically modulated surface on a subwavelength scale...
Graded Index Photonic Crystals (GRIN PhCs) are artificial periodic materials that possess gradually varying effective refractive indices. GRIN profiles can be formed by adjusting the radii or the locations of PhC unit cells. GRIN PhCs exhibit several intriguing characteristics which can be listed as demultiplexing [1], mode-order conversion [2], asymmetric light propagation [3], compact lensing [4],...
We propose for the first time a simple realization of a two-dimensional Parity-Time symmetric hexagonal shaped photonic structure composed of honeycomb lattice. The structure has a symmetric periodic modulation of the refractive index on the wavelength scale, which is combined with an anti-symmetric gain/loss distribution on the same scale. That leads to non-reciprocal light coupling at resonant frequencies...
Recently the beam focusing in reflection from chirped dielectric mirror has been proposed and demonstrated, where the negative (anomalous) diffraction is responsible for this flat mirror focusing. For a strong focusing performance (large focal distance), a wide angular range of strong (negative) angular dispersion is required. We show that a defect layer in the dielectric mirror (one layer is of a...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.