Multimode Photonic Crystal Research Articles

Multiple Fano resonator based on photonic crystal waveguide coupled with two micro-cavities for biomedical sensing application

In order to acquire a miniature refractive index (RI) biosensor with high sensitivity, fast and selective for ultra-low concentrations of molecules, a new Photonic Crystal (PhC) biosensor based on a waveguide coupled to a Fano resonator is proposed for cancer cells detection. An optimized structure of the biosensor can detect cells cancers (Besal, Hela, Jurkat and PC12) in a biological solution deposited on the surface of the resonator. The detection mechanism uses the refractive index as a detection element. The performance of the proposed biosensor is studied by analyzing the variations in the transmission spectrum of different normal and cancer cells. The proposed structure is multimode PhC, with silica as a dielectric material. The finite element method (FEM) have been implemented for studying and investigating the numerical values. The simulation results display that the proposed biosensor attains spectral sensitivities of ‘513.12 nm RIU−1’, ‘587.28 nm RIU−1 ’, ‘702.35 nm RIU−1 ’ and ‘690.57 nm RIU−1 ’ corresponding to Hela cells, PC12 cells, Basal cells and Jurkat cells, respectively. And he qualilty factor Q of the Fano resonance mode can reach 3040.26. Our optimized design ensures easy fabrication with ongoing techniques. This study may open a new way for the development of integrated optical circuits and biosensing.

Ultrasharp ministop-band edge for subnanometer tuning resolution

We propose and demonstrate a method that enables spectral tuning with subnanometer accuracy, and is based on the transmission ministop-band (MSB) in line-defect multimode photonic crystal (PhC) waveguides. The fabricated MSB filter has ultrasharp edges which show a 30 dB drop in transmission in a 4 nm wavelength span. The use of the ultrasharp MSB edge to (optically) determine PhC fabrication accuracy is demonstrated. The wavelength position of the MSB could be tuned by temperature, with a coefficient of 0.1 nm/°C. The spectral characteristics of the MSB realized in this work are promising for sensing, tuning, and modulation applications.

Beaming effect in multimode photonic crystal by using coupled waveguides

Beaming effect of a multimode photonic crystal (PC) covered by a waveguide array on the exit plane is investigated theoretically. The simulation results show that the multimode PC can make the incident light split into two beams, which can be regarded as secondary sources radiating light into the waveguide array. As a result, many light beams can be generated in the array by the coupling among the waveguides, and the interference of these light beams after passing the system leads to directional emission. Additionally, the directional emission is greatly affected by the beam distribution on the exit plane of the system. Once the main light beams are formed on the exit plane of the system by modulating the system size, steady beaming effect can be obtained in the horizontal direction.

2D Analysis of multimode photonic crystal resonant cavities with the finite volume time domain method

In this paper an accurate analysis of two-dimensional (2D) Photonic Crystal (PhC) based multimode resonant cavities is carried out. The analysis is performed with a robust and accurate Finite Volume Time Domain (FVTD) technique. The analysis proves the ability of the FVTD method to extract different resonant modes from a multimode PhC resonant cavity with the use of appropriate source profiles. A detailed explanation on how the source is engineered and used to excite different modes is given. Furthermore, parameters such as resonant frequency and quality factor for each resonant mode are accurately calculated.

Imaging Properties of Multimode Photonic Crystal Waveguides and Waveguide Arrays

Light propagation in multimode photonic crystal (PC) waveguides and in arrays of single-mode PC waveguides is analyzed. The dispersion relations of the modes traveling along these devices explain the numerically observed formation of single and multiple copies of the input beam. As the analogous devices constructed in a standard planar geometry, the proposed PC devices can be employed as filters and demultiplexers. The use of PC structures, where the light is truly confined by the stopband, adds the valuable benefit of a dramatic reduction of the overall geometrical dimensions

Mapping of complex optical field patterns in multimode photonic crystal waveguides by near-field scanning optical microscopy

We use near-field scanning optical microscopy (NSOM) operating in collection mode to map the optical field distribution of continuous wave infrared light propagating along an air-bridged W3 silicon photonic crystal (PC) slab multimode waveguide in a subwavelength resolution. The detected near-field optical intensity distribution patterns show very different longitudinal propagation features and transverse field profiles at different wavelength ranges. We have analyzed the dispersion of the guided modes in the PC waveguide and the corresponding eigenfield profile for each guided mode by means of the three-dimensional plane-wave expansion simulations. It is found that the experimentally observed complex while interesting near-field pattern features can be well explained by the field profiles of the multiple waveguide modes and their superposition at different excitation wavelengths. The detection and analysis of this multimode PC slab waveguide via NSOM could help us to understand complex wave propagation behavior and to further design novel PC devices.

Dynamics of nonlinear photonic crystal atoms characterized by numerical simulations in a pump-probe scheme

We investigate the dynamics of nonlinear photonic crystal (PC) atoms by use of numerical simulations in a pump-probe scheme based on a finite-difference time-domain technique. A two-dimensional nonlinear PC atom with multimode is intentionally employed for the numerical simulations. The use of the multimode PC atom makes it possible that the pump and probe waves are set at different frequencies, ensuring the clear identification of the dynamics of the nonlinear PC atom. The physical model for the dynamics of nonlinear PC atoms has been established and very good agreement between the analytical and simulation results has been achieved.

Self-imaging phenomena in multi-mode photonic crystal line-defect waveguides: application to wavelength de-multiplexing

We show that the self-imaging principle still holds true in multimode photonic crystal (PhC) line-defect waveguides just as it does in conventional multi-mode waveguides. To observe the images reproduced by this self-imaging phenomenon, the finite-difference time-domain computation is performed on a multi-mode PhC line-defect waveguide that supports five guided modes. From the computed result, the reproduced images are identified and their positions along the propagation axis are theoretically described by self-imaging conditions which are derived from guided mode propagation analysis. We report a good agreement between the computational simulation and the theoretical description. As a possible application of our work, a photonic crystal 1-to-2 wavelength demultiplexer is designed and its performance is numerically verified. This approach can be extended to novel designs of PhC devices.