Two-dimensional Photonic Crystal Waveguide Research Articles

Study on transmission of photonic crystal waveguide with slow light phenomena

In this paper, we propose the transmission properties of three two-dimensional photonic crystal waveguides (PCWs) obtained by shifting the shape of air holes localized at each side of the waveguide using the finite difference time domain (FDTD) method. One modifies the radius of air holes and the permittivity of dielectric rods which replace air holes. The other substitute air rings for air holes. The last one is combination of air rings and air holes or dielectric rods. We show that we can achieve unusual “Г-type” or “n-type” transmission spectrum depending on the different parameters such as thickness of air holes, inner radius of air rings and permittivity of square dielectric rod. The notable difference is presented to different structures. Furthermore, we show the slow light phenomena using a unique geometrical parameter. This work will be of significance in fabricating PC devices.

Sensibility of influential factors to transmittance in two-dimensional photonic crystal waveguide composed of Kerr nonlinear medium

In order to obtain the higher propagating efficiency in the photonic crystal waveguide, in this paper, a two-dimensional photonic crystal waveguide composed of Kerr nonlinear dielectric rods is considered to study the parameters influence on transmittance. The most sensitive factor on transmittance is obtained by the method of (NFDTD) according to the orthogonal numerical analysis, which may be helpful to the nonlinear Kerr medium selection in the photonic crystal waveguide design.

Novel all-optical logic gates based photonic crystal waveguide using self imaging phenomena

All-optical logic gate with multifunctional performance have been designed theoretically in a two-dimensional photonic crystal waveguide (PCW) structure using multimode interference principle. A two dimensional finite-difference time domain (2D-FDTD) was employed in our numerical simulations. It is shown that by switching the optical signal to different input waveguide ports, the proposed device can function as XOR, OR, NOR and NOT gates simultaneously or individually. It is also shown that by a combination of photonic band gap and total internal reflection effects in PCWs, the device can operate for both, transverse electric (TE) and transverse magnetic (TM) polarizations. Our simulation results show that the optimized devices have very good transmission efficiencies, a broad frequency range and the contrast ratio are extending to high than 21 dB for TE and 17 dB for TM polarization. The total width and length of the devise are 2.16 and 8.20 \(\upmu \hbox {m}\) respectively achieving miniaturization. It is a kind of promising device for next generation logic optical circuits, ultrahigh speed signal processing, and future photonic crystal based all-optical integrated circuits.

Highly directed emission from self-assembled quantum dots into guided modes in disordered photonic-crystal waveguides

We explore the dynamics and directionality of spontaneous emission from self-assembled In(Ga)As quantum dots into TE-polarised guided modes in GaAs two-dimensional photonic crystal waveguides. The local group velocity of the guided waveguide mode is probed, with values as low as $\sim 1.5\%\times c$ measured close to the slow-light band edge. By performing complementary continuous wave and time-resolved measurements with detection along, and perpendicular to the waveguide axis we probe the fraction of emission into the waveguide mode ($\beta$-factor). For dots randomly positioned within the unit cell of the photonic crystal waveguide our results show that the emission rate varies from $\geq 1.55$ $ns^{-1}$ close to the slow-light band edge to $\leq 0.25$ $ns^{-1}$ within the two-dimensional photonic bandgap. We measure an average Purcell-factor of $\sim 2\times$ for dots randomly distributed within the waveguide and maximum values of $\beta\sim 90 \%$ close to the slow light band edge. Spatially resolved measurements performed by exciting dots at a well controlled distance $0-45$ {\mu}m from the waveguide facet highlight the impact of disorder on the slow-light dispersion. Although disorder broadens the spectral width of the slow light region of the waveguide dispersion from $\delta E_{d}\leq 0.5$ meV to $>6$ meV, we find that emission is nevertheless primarily directed into propagating waveguide modes. The ability to control the rate and directionality of emission from isolated quantum emitters by placing them in a tailored photonic environment provides much promise for the use of slow-light phenomena to realise efficient single photon sources for quantum optics in a highly integrated setting.

Three-visible-light wave combiner based on photonic crystal waveguides.

We present a three-visible-light wave combiner based on two-dimensional photonic crystal waveguides whose widths are not integral multiples of the lattice period. The proposed device consists of two cascaded directional couplers. It combines three visible light waves with different wavelengths from three input ports into a single output port. As an example, a combiner for combining light waves of 635, 532, and 488 nm, which are commonly used as the three primary colors in laser display systems, is designed and demonstrated through the finite-difference time-domain method. The results show that the proposed device can perform efficient synthesis for three visible light waves with transmittance exceeding 89% for each wavelength and high ability in preventing the backward coupling of waves from different waveguides. The method for designing the combiner is useful for designing other waveguide couplers based on photonic crystals made of dispersion materials.

Terahertz polarization splitter based on an asymmetric dual-core photonic crystal fiber

By employing the liquid crystal refractive index changes induced by applied electric field, a novel terahertz polarization splitter with tunable the operating frequency and bandwidths has been proposed and theoretically analyzed. It possesses an extinction ratio as high as the polarization splitters based on the two-dimensional photonic crystal waveguides. These distinguished features ensure its important applications in the integrated optical systems.

Analysis of Effective Numerical Aperture in 2-D Photonic Crystal Waveguide

The effective numerical aperture calculation in two-dimensional Photonic crystal waveguide has been proposed. In this paper we present the analysis of ray optics refracted inside nanorods and at the boundaries between rods, which separates rod gap is much smaller than the incident wavelength assumed to reflect on the region. In operation, the resolving numerical aperture was compared with the finite difference time domain method via OptiFDTD software. Although numerical aperture mentioned above was found to be extremely close to fiber optics, a transmission passes though compartments of the rods are observed due to significant estimation of transmission and reflection of electric field. The compared simulation results will be discussed. By the aforementioned is that in the near future we will modify wave equation in periodic media of waveguide structures reached to the transverse electric equation of beam propagation in the two-dimensional Photonic crystal waveguide analysed.

Band Structure Engineering in 2D Photonic Crystal Waveguide with Rhombic Cross-Section Elements

Two-dimensional photonic crystal (2D PhC) waveguides with square lattice composed of dielectric rhombic cross-section elements in air background, by using plane wave expansion (PWE) method, are investigated. In order to study the change of photonic band gap (PBG) by changing of elongation of elements, the band structure of the used structure is plotted. We observe that the size of the PBG changes by variation of elongation of elements, but there is no any change in the magnitude of defect modes. However, the used structure does not have any TE defect modes but it has TM defect mode for any angle of elongation. So, the used structure can be used as optical polarizer.

RETRACTED: Design of integrated optical circulator based on photonic crystals

Abstract Photonic crystals containing defects produce enhanced Faraday rotation. They have opened up the possibility of fabricating very compact magneto-optics structures. In this work, we have designed a two-dimensional photonic crystal waveguide for use in optical packaging and integrated optical circuits. For design purposes, a temporal coupled mode theory was utilized at the first step. It examined the coupling between cavity and optical ports. After acquiring a general solution, it would be applied to specific problem in hand. Then, optical characteristics of photonic crystal were investigated to design the practical parts such as cavity and waveguides which eventually a triangular crystal lattice of air holes in Bi:YIG (BIG) was considered to be the best candidate. Finally, the results of analytical investigations were evaluated using OptiFDTD software and then were confirmed.

点缺陷二维光子晶体波导的出射光集束

点缺陷二维光子晶体波导的出射光集束

Transverse-electric and transverse-magnetic mode slow light propagation in a two-dimensional photonic crystal waveguide

A two-dimensional photonic crystal waveguide structure is designed for both TE- and TM-mode slow light propagation. The minimum group index of the waveguide for TE and TM modes can reach to 137.8 and 126.4, and the two polarizations have the same slow light frequency region. The designed structure can provide a large bandwidth range with very low group velocity dispersion for both TE and TM modes. The transmission property investigation for a suspended two-dimensional slab photonic crystal waveguide (PCW) indicates that such slow light character may be retained when perfect reflectors can be fixed on the horizontal surfaces of the slab. Such high group index for both TE and TM modes in two-dimensional PCWs is, to the best of our knowledge, first reported here, and may provide some useful guides for slow light research in theory.

Guided Modes of Positive and Negative Group Index in the Honeycomb Photonic Crystal Waveguides

A guided mode of positive and negative group index structure is essential to quantum optics for design and development of high efficiency optical devices which are useful to security optical communication system and to diverse applications such as Optical Time-Division-Multiplexing, Optical Switch, Laser, LED, Entangled Photon Source and Single Photon Source. Thus, we proposed to develop an efficient photon emission along line defect of two-dimensional honeycomb photonic crystal waveguide in the silicon slab. The honeycomb lattice of circular air holes on a silicon plate is simulated to obtain two nearest guided modes between positive and negative group index regimes. This significant property shows the potential applied guided modes of photonic crystal waveguide enhancing spontaneous emission for controlling photon emission between two resonance frequencies. Significantly, this work is oriented to produce the novel optical devices for control photon emission in the optical communication system. In addition to the honeycomb lattice, it can easily be made on a Si on insulator (SOI) wafer.

Time-domain mapping of nonlinear pulse propagation in photonic-crystal slow-light waveguides

We perform an experimental time-domain mapping of nonlinear pulse propagation through a two-dimensional photonic-crystal waveguide. Our optical gating method allows for the complete reconstruction of the peculiar propagation behavior in this highly dispersive structure. Temporal soliton formation is accompanied by fast time-scale dynamics within the picosecond pulse regime. For high signal powers, the photonic waveguide band is modified, leading to an acceleration of the propagated pulse.

Influence of disorder and deformation on the optical properties of a two-dimensional photonic crystal waveguide

We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrication and practical applications based on photonic crystal waveguides.

Tunable flat band slow light in reconfigurable photonic crystal waveguides based on magnetic fluids

A kind of two-dimensional photonic crystal line-defect waveguide with 45°-rotated square lattice is proposed to present slow light phenomena. Infiltrating the photonic crystal waveguide with appropriate magnetic fluids can generate very wide flat bands of guided modes, which give rise to the excellent slow light properties. The bandwidth centered at λ0=1550nm of the designed W1 waveguide is considerably large (around 54nm). The obtained group velocity dispersion β2 within the bandwidth is ultralow (varying from −2118a/2πc2 to 1845a/2πc2, where a and c are the period of the lattice and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large compared with other works. Reconfiguring the photonic crystal waveguide with magnetic fluids of different concentrations can remarkably tune the slow light parameters and the trade-off between them, while the type of magnetic nanoparticles constituting the magnetic fluids negligibly affect the slow light properties. The explicit linear variation of the slow light parameters with the magnetic fluid concentration is convenient for the practical tuning.

Coupled-mode formulation of two-parallel photonic-crystal waveguides

A self-contained coupled-mode formulation for coupled two-dimensional photonic-crystal waveguides (PCWs) is discussed. Using a perturbation theory, the first-order coupled-mode equations are systematically derived, which govern the evolution of the modal amplitude of individual PCWs in isolation. The coupled-mode equations are used to analyze the coupled symmetric PCWs consisting of a square lattice of circular dielectric rods or air holes. It is shown that the results are in good agreement with those obtained by the rigorous direct analysis of the coupled waveguide system.

Optimization of a two-dimensional photonic crystal waveguide for ultraslow light propagation

A two-dimensional photonic crystal waveguide is optimized for ultraslow light propagation. By employing geometry projection method optimization, a flat band photonic crystal waveguide is achieved with the minimum group index around 2335, which is much larger than those reported before. The investigation of the transient propagation of the Gaussian pulse in the waveguide indicated that low group velocity dispersion can cause a small expansion of the pulse. The stability analysis indicates that slightly numerical and angular deviation in fabrication can influence the minimum group index of the waveguide, but the ultraslow light property can still be maintained. The theory simulation in our work can provide some useful guidance for further ultraslow light research.

Electro-optical modulation in two-dimensional photonic crystal linear waveguides

The electro-optical modulation in a two-dimensional photonic crystal linear waveguide is presented. In order to create a linear waveguide, the radius of a line of rods is reduced. The linear waveguide composed of a dielectric cylinder in air is studied by solving Maxwell's equations using the plane wave expansion method and the finite-difference time–domain method. The switching mechanism is a change in the conductance in the waveguide region and hence modulating the guided modes and eventually switching is achieved. Such a mechanism of modulation should open up a new application for designing tunable components in photonic integrated circuits.

Magnetically controlled photonic crystal binary digits generator

In this work, we explore in detail the physical mechanism of the one-way propagating characteristic of a two-dimensional magneto-optical photonic crystal (MOPhC) waveguide, and then design the high-efficiency and wide bandwidth straight waveguide, 90° bent waveguide and splitter. Furthermore, we integrate the above basic component devices together, and design a 4 × 4 magnetically controlled MOPhC binary digits generator. To the best of our knowledge, it is the first time that such kind of device is proposed. This kind of binary digits generator can find wide applications in the future communication.

Tunable slow-light multi-mode photonic crystal waveguides based on the coupling of square cavities

The light transmission properties through two-dimensional photonic crystal waveguides based on coupling of square cavities are studied by the finite-difference time-domain technique. Through interlacing the adjacent cavities along the direction vertical to the waveguide, the coupling distance between the adjacent cavities is extended, and the group velocity of the guiding modes can be slowed by five-fold compared with that in vacuum. Because of the different spatial field distributions of various resonant modes, the corresponding group velocities are also different for the same CROW structure.