Pulses In Photonic Crystals Research Articles

3D few cycle optical pulses in carbon nanotube-based photonic crystal with allowance for mechanical stress

This paper constructs and numerically analyzes a theoretical model of three-dimensional few cycle optical pulse dynamics in semiconductor carbon nanotube-based spatially-modulated refractive index medium. It takes into account external deformation in terms of the gauge theory. It identifies the stable propagation of that kind of pulses in photonic crystal. The paper also reveals the dependence of pulse dynamics on photonic crystal characteristics (refractive index depth and modulation period in particular).

Propagation of two-dimensional extremely short optical pulses in photonic crystal with silicene

We consider the wave equation for an electromagnetic field propagating in silicene placed in photonic crystal (PC). We study the effects observed when the depth of the nonlinearity modulation are varied, as well as the initial amplitude of the electromagnetic pulse.

Integrated optical auto-correlator based on third-harmonic generation in a silicon photonic crystal waveguide

The ability to use coherent light for material science and applications is linked to our ability to measure short optical pulses. While free-space optical methods are well established, achieving this on a chip would offer the greatest benefit in footprint, performance and cost, and allow the integration with complementary signal-processing devices. A key goal is to achieve operation at sub-watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer or long tunable delay lines. Here we report a device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS-compatible device, which could operate without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as an in situ diagnostic tool to map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals.

Dynamical Bragg diffraction of optical pulses in photonic crystals in the Laue geometry: Diffraction-induced splitting, selective compression, and focusing of pulses

A theory for the dynamical Bragg diffraction of a spatially confined laser pulse in a linear photonic crystal with a significant modulation of the refractive index in the Laue geometry has been developed. The diffraction-induced splitting of a spatially confined pulse into the Borrmann and anti-Borrmann pulses localized in different regions of the photonic crystal and characterized by different dispersion laws is predicted. The selective compression or focusing of one of these pulses with the simultaneous broadening or defocusing of the other pulse is shown to be possible.

Atomic wave packet dynamics in finite time-dependent optical lattices

Atomic wave packets in optical lattices which are both spatially finite and time dependent exhibit many striking similarities with light pulses in photonic crystals. We analytically characterize the transmission properties of such a potential geometry for an ideal gas in terms of a position-dependent band structure. In particular, we find that at specific energies, wave packets at the centre of the finite lattice may be enclosed by pairs of band gaps. These act as mirrors between which the atomic wave packet is reflected, thereby effectively yielding a matter wave cavity. We show that long trapping times may be obtained in such a resonator and investigate the collapse and revival dynamics of the atomic wave packet by numerical evaluation of the Schrödinger equation.

用于高能啁啾脉冲压缩的光子晶体光栅的设计

用于高能啁啾脉冲压缩的光子晶体光栅的设计

Nonlinear optics of extremely short pulses in photonic crystals with controlled dispersion

The propagation of optical pulses with few oscillations in quadratically nonlinear media with modulated dispersion has been studied. It is shown that a periodic change in the velocity mismatch and the third-order dispersion coefficient makes it possible to suppress the walk-off and decompression of pulses, as a result of which the efficiency of interaction of extremely short pulses significantly increases.

Ultrashort light pulses in photonic crystals in subdiffractive regimes

We investigate analytically (by harmonic mode expansion) and numerically (by finite-difference-time-domain technique) the propagation of light pulses in photonic crystals in subdiffractive regimes. It is shown that in general the short pulses of narrow beams diffract more strongly than the corresponding monochromatic beams and disperse more strongly than the corresponding pulses of the plane waves. We also demonstrate coupling between the temporal dispersion and the spatial dispersion (diffraction) resulting in a complicated spatiotemporal evolution of the propagating pulses.

Subdiffractive light pulses in photonic crystals

We investigate propagation of light pulses in photonic crystals in the vicinity of the zero diffraction point. We show that Gaussian pulses due to nonzero width of their temporal spectrum spread weakly in space and time during the propagation. We also find the family of nonspreading pulses, propagating invariantly in the vicinity of the zero diffraction point of photonic crystals.

Broadening compensation for ultrashort pulses in photonic crystals

Extremely large group velocity dispersion of both signs can be achieved at the band edges of guided modes in photonic crystal waveguides. The selection of a proper value and sign of this parameter allows the design of short-length waveguides to compensate for pulse broadening. This pulse broadening can be caused, for instance, when a photonic crystal delay line is introduced. We present a theoretical study of the possibilities of using photonic crystal waveguides as intra-circuital dispersion compensation elements for ultrashort pulses, so the width of a transmitted pulse can be reduced. However, we also demonstrate that recovering the original pulse shape is not possible for these large-bandwidth pulses due to higher-order dispersion terms.

Dynamics of counterpropagating pulses in photonic crystals: enhancement and suppression of stimulated emission processes.

Using numerical methods, we study the propagation of counterpropagating pulses in finite photonic crystals. We show that linear interference and localization effects combine to either enhance or suppress stimulated emission processes, depending on the initial phase difference between the input pulses. We consider the example of second harmonic generation, where we find a maximum contrast of three orders of magnitude in nonlinear conversion efficiency as a function of the input phase difference between incident pulses. We interpret these results by viewing the photonic crystal as an open cavity, with a field-dependent, electromagnetic density of modes sensitive to initial and boundary conditions.

Matched second-harmonic generation of ultrashort laser pulses in photonic crystals

It is shown that one-dimensional photonic bandgap structures are capable of simultaneously satisfying the phase and group-velocity matching conditions for second-harmonic generation involving extremely short light pulses. When these conditions are satisfied, an optical frequency doubler utilizing photonic bandgap structures provides a means for increasing the rate of growth of the second-harmonic signal as a function of the nonlinear-optical interaction length relative to structures designed for quasi-matched interactions and affords possibilities for enhancing the frequency doubling efficiencies independently of the matching length in the bulk nonlinear material.

Compression of ultrashort light pulses in photonic crystals: when envelopes cease to be slow

A modification of the transfer-matrix method and the nonlinear finite-difference time-domain technique are applied to simulate the propagation of ultrashort laser pulses in linear and nonlinear one-dimensional photonic band gap (PBG) structures. Dispersion properties of photonic crystals allow the chirp of a short light pulse to be compensated in a controlled fashion. It is demonstrated that photonic crystals with embedded optical nonlinearity provide an opportunity to efficiently compress laser pulses to a duration of several optical cycles on a submillimeter spatial scale, providing new opportunities for the miniaturization of femtosecond solid-state laser systems. Physical factors limiting the minimum duration of compressed pulses are studied for such structures and the ways to optimize pulse compression are discussed. Examples of PBG pulse compressors that can be fabricated by means of currently existing technologies are considered.

Compression of light pulses in photonic crystals

A study is made of the feasibility of controlling the phase and duration of short laser pulses with the aid of dispersive properties of photonic crystals. Pulse compression and phase modulation in one-dimensional structures with photonic band gaps are investigated analytically and numerically. It is shown that photonic crystals with a cubic optical nonlinearity can be used to reduce the duration of laser pulses, right down to several periods of an optical field, in structures with spatial dimensions typically less than a millimetre. The physical factors which limit the minimum duration of light pulses compressed in such photonic crystal structures are identified.