Heterostructure wavelength division demultiplexers using photonic crystal ring resonators

In this study, an all optical 4-to-2 encoder have been proposed which has four input and three output ports. The proposed structure can generate a 2-bit binary code considering which input port is active. For realising the proposed structure first the authors proposed and designed a BUFFER and an OR gate. Then combined these basic gates to realise the proposed encoder. The maximum switching delay and footprint for the proposed structure are about 200 fs and 880 μm2, respectively.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-opt.2016.0022

Proposal for 4-to-2 optical encoder based on photonic crystals

In this paper, we propose what we believe is a novel all-optical analog-to-digital converter (ADC) based on photonic crystals. The proposed structure is composed of a nonlinear triplexer and an optical coder. The nonlinear triplexer is for creating discrete levels in the continuous optical input signal, and the optical coder is for generating a 2-bit standard binary code out of the discrete levels coming from the nonlinear triplexer. Controlling the resonant mode of the resonant rings through optical intensity is the main objective and working mechanism of the proposed structure. The maximum delay time obtained for the proposed structure was about 5 ps and the total footprint is about 1520  μm2.

Ultra-fast analog-to-digital converter based on a nonlinear triplexer and an optical coder with a photonic crystal structure.

Two bit all-optical analog-to-digital converter based on nonlinear Kerr effect in 2D photonic crystals

Orthogonal frequency division multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems because it is an effective solution to intersymbol interference caused by a dispersive channel. Very recently a number of researchers have shown that OFDM is also a promising technology for optical communications. This paper gives a tutorial overview of OFDM highlighting the aspects that are likely to be important in optical applications. To achieve good performance in optical systems OFDM must be adapted in various ways. The constraints imposed by single mode optical fiber, multimode optical fiber and optical wireless are discussed and the new forms of optical OFDM which have been developed are outlined. The main drawbacks of OFDM are its high peak to average power ratio and its sensitivity to phase noise and frequency offset. The impairments that these cause are described and their implications for optical systems discussed.

OFDM for Optical Communications

In the paper, a novel three-port channel drop filter in two dimensional photonic crystals (2D PCs) with a wavelength-selective reflection micro-cavity is proposed. In the structure, two micro-cavities are used. One is used for a resonant tunneling-based channel drop filter. The other is used to realize wavelength-selective reflection feedback in the bus wave-guide, which consists of a point defect micro-cavity side-coupled to a line defect waveguide based on photonic crystals. Using coupled mode theory in time, the conditions to achieve 100% drop efficiency are derived thoroughly. The simulation results by using the finite-difference time-domain (FDTD) method imply that the design is feasible.

Photonic crystal channel drop filter with a wavelength-selective reflection micro-cavity

In this paper, we investigate the dispersion and polarization properties of photonic crystal fiber with one ring or more rings of elliptical air-holes using plane-wave expansion (PWE) method. By introducing three rings of elliptical air-holes, PCF with ultra-low and ultra-flattened dispersion is designed and a total dispersion curve between ±0.5 ps/nm/km from 1315 to 1855 nm wavelength range is demonstrated. Furthermore, the polarization property of these elliptical air-hole-containing PCFs is analyzed and the variation of the birefringence with the area and ellipticity of the elliptical air-holes are discussed.

Dispersion and polarization properties of elliptical air-hole-containing photonic crystal fibers

Based on two-dimensional photonic crystals with a triangular lattice, a channel drop filter with a wavelength-selective reflection microcavity is designed. In the structure, two microcavities are used. One is used for a resonant tunneling-based channel drop operation. The other is used to realize wavelength-selective reflection feedback in the bus waveguide. The phase term, which is derived by means of coupled-mode theory to achieve close to 100% drop efficiency, is satisfied by modifying the sizes of the border air holes next to the bus waveguide section between the two cavities. Using the finite-difference time-domain method, the simulation results show complete power transfer between the bus and drop waveguides via the system.

Channel drop filter in two-dimensional triangular lattice photonic crystals.

As an important component of scanning near-field optical microscope (SNOM), optical fibre nanoprobe has been applied to many fields extensively. A melt-stretched etching method is proposed to produce optical fibre nanoprobe with low cost. Firstly, optical fibre tip with micrometer-sized diameter is created by the melt-stretched measure. Next, it is dipped into hydrofluoric acid (HF), and a fine optical fibre nanoprobe will be made after a short-time etching. Owing to the taper structure of tip, it can be etched again in acid if a nanoprobe is not constructed when the first etching is completed. In addition, optical fibre nanoprobe is applied to spectral investigation, and the fluorescence spectroscopy of rhodamine B (Rh B) solution is collected by an optical investigation system with a bifurcated fibre.

Hongliang Ren

Papers

Photonic crystal channel drop filter with a wavelength-selective reflection micro-cavity

Dispersion and polarization properties of elliptical air-hole-containing photonic crystal fibers

Channel drop filter in two-dimensional triangular lattice photonic crystals.

The preparation of optical fibre nanoprobe and its application in spectral detection

Design and analysis of two-dimensional photonic crystals channel filter