Jung-Sheng Chiang

NUMERICAL ANALYSIS OF APODIZED FIBER BRAGG GRATINGS USING COUPLED MODE THEORY

In this paper, the coupled mode theory is used to analyze apodized fiber Bragg gratings (FBGs). Since the profile of gratings varies with the propagation distance, the coupled mode equations (CMEs) of apodized FBGs are solved by the fourth-order Runge-Kutta method (RKM) and piecewise-uniform approach (PUA). We present two discretization techniques of PUA to analyze the apodization profile of gratings. A uniform profile FBG can be expressed as a system Corresponding author: H.-W. Chang (hchang@faculty.nsysu.edu.tw).

A New Look at Numerical Analysis of Uniform Fiber Bragg Gratings Using Coupled Mode Theory

The coupled mode theory (CMT) is used to analyze uniform Fiber Bragg gratings. The multi-mode CMT is expressed as the flrst-order vector ordinary difierential equations (ODEs) with coe-cients depending on the propagation distance. We show in this paper that by changing variables, the original couple mode equations (CMEs) can be re-casted as constant coe-cient ODEs. The eigenvalue and eigenvector technique (EVVT), the analytic method for solving constant coe-cient ODEs, is then applied to solve the coupled mode equations. Furthermore, we also investigate the application of Runge- Kutta method (RKM) to the calculation of the global transfer-function matrix for CMEs. We compare the transmission and the re∞ection

Analysis of an Ultrashort PCF-Based Polarization Splitter

We propose a new structure of polarization splitter based on a dual-elliptical-core photonic crystal fiber. The polarization splitter has a simple and symmetric directional coupler configuration. The vector boundary element method is used to investigate the propagation characteristics of the device under various conditions. Results of the numerical calculation relevant to the design conditions are presented. A 0.3-mm-long splitter with an extinction ratio of 23 dB is obtained.

Second-order fiber Bragg gratings

In this paper second-order fiber Bragg gratings are firstly experimentally demonstrated to have the characteristic of surface-normal radiation confirmed by measuring the radiation power of 0.012mW from the 2D far-field pattern.

Enhanced Cascaded SHG+DFG Process of Femtosecond Pulses Using Chirp Quasi-Phase Matching Waveguide

This study presents a chirp quasi-phase matching (QPM) waveguide to increase the conversion efficiency of the cascaded SHG+DFG effect for femtosecond pulses. The coupled mode theory is used to analyze the cascaded SHG+DFG process. In this paper, a constructive interference zone (or cascaded SHG+DFG region) is defined as when the conversion wave and its coupling component constructively interfere with each other and have a phase difference ranging from 0 to 0.5pi or from 1.5 to 2pi. On the other hand, the region is called a destructive interference zone (or back conversion region) when the phase difference ranges from 0.5 to 1.5pi . The proposed chirp QPM waveguide is designed to extend constructive interference length and shorten destructive interference length over the waveguide. The simulation results demonstrate that for a pulsewidth of 0.6 ps, the maximum conversion efficiency of a 50-mm chirp QPM waveguide can be increased to 25 times that of a uniform QPM waveguide.

A new compact polarization beam splitter based on dual-elliptical-core photonic crystal fiber

Based on a vectorial boundary element method and the normal mode coupled theory, there is an optimum design for achieving a compact polarization splitter with broad extinction ratio bandwidth by adjusting only one parameter.

Multi-grating sections of dielectric waveguides

The reflectivity of forty-grating sections consisting of two grating periods is simulated. Close difference of two gratings periods causes similarity of the reflectivity of forty-gratings and single gratings except for the phase shift phenomenon.

High Sensitive Two-Dimension Tilted-Meter Based on Chirped Fiber Bragg Gratings

A high sensitive two-dimension tilted-meter using the two etched chirped fiber Bragg gratings (CFBGs) is experimentally demonstrated. The sensitivity of tilted angle is 0.303 nm/°, corresponding to the resolution of 0.033°. The proposed 2D tilted meter can be used for measuring the tilted angle and directional angle with the tilted angle ranging from 0° to 35° and the direction angle ranging from 0° to 360°. The operation mechanism is based on the two CFBGs with the superposition wavelength peak shift created by the overlap between the spectra from a CFBG in the liquid and the air region.

Broadband Light-Emitting Diodes with One-Dimensional Photonic Crystal Layer

Abstract In this article, a broadband gallium-nitride-based light-emitting diode with a one-dimensional photonic crystal layer is investigated. The broadband light-emitting diode using the proposed backside reflector has high reflectance (>95%) over a 270-nm bandwidth in visible light at an arbitrary incidence angle. A broadband light-emitting diode of high output power due to the high reflectivity is achieved. Also reported are the results for light-emitting diodes by the transistor outline can (TO-can) package. The proposed light-emitting diodes possess broadband high reflected spectra, high output power for light extraction, and a good view angle.

Radiation in 45-degree tilted fiber Bragg gratings

Surface-normal radiation of 45° tilted fiber gratings are fabricated and measured. A 3-minute exposure time of tilted FBGs can cause -15dB radiation efficiency, while a 1.5-minute exposure time can create the radiated efficiency of -16.2dB.