Recently it has been shown that it is possible to achieve directional emission out of a subwavelength aperture in a periodically corrugated metallic thin film. We report on theoretical and experimental studies of a related phenomenon concerning light emitted from photonic crystal waveguides that are less than a wavelength wide. We find that the termination of the photonic crystal end facets and an appropriate choice of the wavelength are instrumental in achieving very low numerical apertures. Our results hold promise for the combination of photonic crystal waveguides with conventional optical systems such as fibers, waveguides, and freely propagating light beams.

Highly Directional Emission from Photonic Crystal Waveguides of Subwavelength Width

The add drop filter (ADF) is one of the most significant devices for coarse wavelength division multiplexing (CWDM) systems to add and/or drop a required channel individually from multiplexed output channels without disturbing other channels. The important parameters of the ADF are coupling efficiency, dropping efficiency, passband width and Q factor. Photonic crystal (PC)-based optical devices have attracted great interest due to their compactness, speed of operation, long life period, suitability for photonic integrated circuits, and future optical networks. Here, an extensive overview of a photonic crystal ring resonator (PCRR)-based ADF using a different shape of ring resonator is presented, and its corresponding functional parameters are discussed. Finally, the designed circular PCRR-based ADF for an ITU-T G 694.2 CWDM system is presented. Approximately 100% of coupling efficiency and dropping efficiency, 114.69 of Q factor, and 13 nm of passband width is obtained through simulation, which outperforms the reported one.

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-52/issue-6/060901/Photonic-crystal-ring-resonator-based-add-drop-filters--a/10.1117/1.OE.52.6.060901.pdf

Photonic crystal ring resonator-based add drop filters: a review

Novel design of optical channel drop filters based on two-dimensional photonic crystal ring resonators

Abstract We have proposed simple ring resonator 5-channel demultiplexer based on optical channel drop filter analysis that is applicable at third communication window (1550 nm) range. Our proposed base filter is the important part in designing the demultiplexer, inclusive one ring resonator contains one square dielectric rod at core. Demultiplexer structure introduced by arranging five filter with different ring core refractive index. Insomuch every ring core have individual refractive index, thus each ring have diverse resonant wavelength. Numerical results by the finite difference time domain (FDTD) method show quality factor (Q) and transmission efficiency of fundamental channel drop filter are 1038 and 93 %, respectively. It is found that transmission efficiency in designed demultiplexer is more than 90 % for each channel; channel spacing is less than 4.2 nm. The average crosstalk value, total footprint of demutiplexer is −17.85 dB, 689.61 μm2, respectively. Small size with a very simple ring design can be benefit in photonic integrated circuit.

An Optical Five Channel Demultiplexer-Based Simple Photonic Crystal Ring Resonator for WDM Applications

Symmetric multilayer slab waveguide structure with a negative index material: TM case

The position independence of heterostructure coupled waveguides in photonic-crystal switch

A type of metamaterial composed of a metal waveguide with discrete rod resonators, is investigated in this work for the first time. The simulation results show that the maximum of FOM=-Re(n)/Im(n) reaches 1.12 at the 543.5 nm. For another set of dimensions of the unit cell, the maximum of FOM reaches 1.41 at the wavelength of 721 nm. Our additional large numbers of simulation results show that different negative-index bands in visible wavelengths can be obtained by tuning the geometric dimensions of the unit cell.

High-transmission negative refraction of discrete rod resonators confined in a metal waveguide at visible wavelengths.

A left-handed material, a discrete fishnet array confined in a metal waveguide, is reported in our work. Our simulation results show the negative refraction occurring at visible wavelengths. The maximum of aFOM=−Re(n)/Im(n) reaches 0.9 near the wavelength of 640 nm. For another set of dimensions of the unit cell, the maximum of a FOM equals 1.07 near the 655 nm wavelength. It is indicated that this approach is greatly effective for the realization of negative refraction at visible wavelengths. Moreover, the mechanism of resonance as well as the effective inductor-capacitor (LC) circuit model is investigated.

Qiong Wang

Papers

The position independence of heterostructure coupled waveguides in photonic-crystal switch

High-transmission negative refraction of discrete rod resonators confined in a metal waveguide at visible wavelengths.

Negative refractive indices of a confined discrete fishnet metamaterial at visible wavelengths

Beaming effect in multimode photonic crystal by using coupled waveguides

Generating mechanism of the energy-stream loops for the evanescent waves in a left-handed material slab