Browsing by Author "Chen, Chi-Feng"

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A good performance 3-dB splitter based on coupling-weighted and velocity-tapered waveguides
(2015-09-01)
Wang, Hseng-Tsong
;
Chen, Chi-Feng
;
Chi, Sien
;
光電工程學系
;
Department of Photonics
A coupling-weighted and velocity-tapered 3-dB splitter with a symmetric triple-mode evolution structure weighted by the Blackman function is analytically and numerically investigated for C+L-band passive optical network applications. The splitter is analyzed by the coupled-mode theory and simulated by the use of three-dimensional finite-difference beam propagation method. It is found that the power uniformity, wavelength dependent loss, excess loss and polarization dependent loss of the proposed 3-dB splitter in the whole C+L-band are better than 2.49 x 10(-3) dB, 0.018 dB, 0.14 dB, and 0.004 dB, respectively. It is evident that the 3-dB splitter can achieve the good performances for C+L-band passive optical network applications. (C) 2015 Elsevier B.V. All rights reserved.
A Numerical Solution for Broadband PLC Splitter with Variable Splitting Ratio Based on Asymmetric Three Waveguide Structures
(2019-05-01)
Wang, Hseng-Tsong
;
Chen, Chi-Feng
;
Chi, Sien
;
光電工程學系
;
光電工程研究所
A numerical solution for the broadband planar-lightwave-circuit (PLC) splitter with a variable splitting ratio based on asymmetric three waveguides weighted by the Blackman weighting function is designed for passive optical network applications with wavelengths between 1.53 and 1.57 mu m. The performance of the proposed splitter is verified using the beam propagation method (BPM). It was found that a polynomial function of the splitting ratios accompanying a geometrical shift can be derived from the proposed splitter. The splitting ratio can be changed from 50:50 to 90:10 with this geometrical shift. The excess loss, crosstalk, polarization dependent loss, and splitting ratio variations against wavelength of the proposed splitter with wavelengths between 1.53 and 1.57 mu m are better than 0.139 dB, -22.75 dB, 0.006 dB, and 0.335%, respectively. Obviously, the proposed splitter with variable splitting ratio retains the advantages of the symmetric design, such as low excess loss, low crosstalk, polarization insensitivity, broadband, and wavelength insensitivity.
Antireflection subwavelength structures analyzed by using the finite difference time domain method
(2009)
Ting, Chia-Jen
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Chen, Chi-Feng
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Chou, C. P.
;
機械工程學系
;
Department of Mechanical Engineering
Antireflection subwavelength structures (ASSs) are analyzed by using the finite difference time domain (FDTD) method in the visible light spectrum. Low reflectance can be obtained by both the conical and pyramidal shapes over a broadband range. Comparing the reflectance of different structure shapes and aspect ratios by the FDTD method, it shows that the antireflection efficiencies of the pyramidal structures are better than that of the conical structures when the aspect ratio is up to 0.8. It is found that, for the conical structure surface, the average transmittance increases gradually with the aspect ratio and the average transmittance is about 99.6% with the aspect ratio of 2.0. However, for the pyramidal structure with the aspect ratio ranging from 1.0 to 2.0, the average transmittance is up to 99.7%. (C) 2008 Elsevier GmbH. All rights reserved.
Experimental study of a silver layer on an antireflection subwavelength-structured surface
(2008-07-01)
Ting, Chia-Jen
;
Chen, Chi-Feng
;
Chou, C. P.
;
機械工程學系
;
Department of Mechanical Engineering
The optical characteristics of a silver layer deposited on an antireflection subwavelength-structured surface are investigated. The experimental results of the reflectance and the transmittance of several different thicknesses of silver layer on the subwavelength-structured surface are carried out. A subwavelength structure with the spatial period and diameter of about 230 nm and height of about 150 nm on polyethylene terphthalate film is fabricated by microreplication process. It is shown that such an element with the suitable silver layer deposited on an antireflection subwavelength-structured surface has high transmittance and low glare in the visible spectral range and high reflectance in the infrared range. Obviously, the optical film with silver layer can not only obtain the high performance of heat insulation but also give an application in automobile and house windows.
Fabrication of an antireflective polymer optical film with subwavelength structures using a roll-to-roll micro-replication process
(2008-07-01)
Ting, Chia-Jen
;
Chang, Fuh-Yu
;
Chen, Chi-Feng
;
Chou, C. P.
;
機械工程學系
An antireflective optical film with subwavelength structures replicated by use of a roll-to-roll micro-replication process (RMRP) is investigated. Firstly, a single layer of a nanostructure on a polymer film is designed for an antireflection purpose by the finite difference time domain method in the visible light spectrum. Structures of a conical cylinder array, with spatial period of 400 nm, diameter of 200 nm and height of 350 nm, are numerically obtained. Then, such structures are fabricated by RMRP combining originated structure fabrication realized by deep ultra-violet lithography and dry etching, Ni mold electroplating and replication by using the roll-to-roll process imprinting into the flexible polyethylene terephthalate substrate. A nanostructure roller mold bonded with Ni molds has been successfully fabricated and coated with the self-assembly monolayer process for the purpose of fabricating an anti-adhesion film and improving the lifetime of the Ni molds. The duplicated nanostructure films show a good optical quality of antireflection (AR <= 2.45% in a 400-700 nm spectral range) and are in good agreement with the theoretical predictions. The experimental results show that the developed process is a promising and cost-effective method for the continuous duplication of flexible devices with nano-scaled feature sizes used in nanophotonics by RMRP.
Subwavelength structures for broadband antireflection application
(2009-02-01)
Ting, Chia-Jen
;
Chen, Chi-Feng
;
Chou, C. P.
;
機械工程學系
;
Department of Mechanical Engineering
The subwavelength structures are designed and fabricated for broadband antireflection application. Under target of zero reflectivity, the parameters of periodic 2-D continuous conical structures are analyzed by the finite-difference time-domain (FDTD) method. The corresponding conical structures are obtained with spatial period of 350 nm and structure height of 300 nm, respectively. The 2-D continuous conical structured surface is fabricated by micro-replication process combining with the originated structure fabrication realized by interference lithography, Ni mold electroplation and replication by using UV imprinting into plastics. The average reflectances of the simulation and replicated polymer prototype are about 0.50% and 0.54% within the spectral ranges of 400-650 nm, respectively. In a word, the subwavelength structured surface with low reflection is developed and proved to be highly consistent with the simulation results. (C) 2008 Elsevier B.V. All rights reserved.
The freeze of intrapulse Raman scattering effect of ultrashort solitons in optical fiber
(2007)
Chen, Chi-Feng
;
Luo, Boren
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光電工程學系
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Department of Photonics
The effect of intrapulse Raman scattering (IRS) for the propagation of the femtosecond solitons in an optical fiber is investigated. To factually simulate its influence, a combination of 27 Lorentian lines to fit experimental Raman gain profile is adopted. By using nonlinear Schrodinger equation and finite-difference time domain method, the propagations of femtosecond fundamental solitons in an optical fiber are numerically calculated. When the initial power is suitably enhanced, it is found that the pulse shape is almost the same as initial pulse and the delay Raman response only makes small pulse shift. In other words, when ultrashort soliton is considered, the IRS effect is similarly frozen under the enhanced initial power. (c) 2006 Elsevier GmbH. All rights reserved.
The modified propagation equation for TM polarized subwavelength spatial solitons in a nonlinear planar waveguide
(2006)
Chen, Chi-Feng
;
Chi, Sien
;
光電工程學系
;
Department of Photonics
The wave equation of TM polarized subwavelength beam propagations in a nonlinear planar waveguide is derived beyond the paraxial approximation. This modified equation contains more higher-order linear and nonlinear terms than the nonlinear Schrodinger equation. The propagation of fundamental subwavelength spatial solitons is numerically studied. It is shown that the effect of the higher nonlinear terms is significant. That is, for the propagation of narrower beam the modified nonlinear Schrodinger equation is more suitable than the nonlinear Schrodinger equation. (c) 2006 Elsevier GmbH. All rights reserved.