Browsing by Author "Chen, Chih-Cheng"

Now showing 1 - 5 of 5

Effects of Lattice Types on GaN-Based Photonic Crystal Surface-Emitting Lasers
(2015-01-01)
Wu, Tzeng-Tsong
;
Chen, Chih-Cheng
;
Lu, Tien-Chang
;
光電工程學系
;
Department of Photonics
GaN-based photonic crystal (PC) surface emitting lasers with different lattice types including hexagonal, square, and honeycomb lattice were fabricated and characterized. Laser characteristics including threshold conditions, lasing spectra, polarization, and divergence angle of devices with different lattice have been studied and discussed. The threshold energy density of the device with honeycomb, hexagonal, and square lattice was measured to be approximately 1.6, 2.3, and 3.8 mJ/cm(2) at room temperature, showing superior characteristics of applying honeycomb as PC lattice patterns. Moreover, the experimental results were matched well to the theoretical prediction using the multiple scattering method. Finally, the laser characteristics of devices with three lattice types such as divergence angle and degree of polarization (DOP) were analyzed and discussed. The device with honeycomb lattice shows low threshold, high DOP of 86%, and low divergence angle of 1.3 degrees among three lattice types, demonstrating its potential in the future surface emitting laser sources.
Lasing Characteristics of GaN-Based Photonic Quasi-Crystal Surface Emitting Lasers Operated at Higher Order Gamma Mode
(2015-11-01)
Hong, Kuo-Bin
;
Chen, Chih-Cheng
;
Lu, Tien-Chang
;
Wang, Shing-Chung
;
光電工程學系
In this study, GaN-based photonic quasi-crystal surface emitting lasers (PQCSELs) operated at different Gamma band-edge modes were fabricated and investigated. The photonic quasi-crystal patterns were defined by utilizing electron-beam lithography and inductively coupled plasma etching. Distinctive higher order Gamma band-edge lasing modes were identified in the GaN PQCSELs. The threshold energy density and lasing wavelength for the S3 band-edge mode were 4.6 mJ/cm(2) and 394.2 nm, respectively. The decreasing tendency of the threshold energy of PQCSEL was observed while the designed lasing mode moved from the higher Gamma band to the lower Gamma band. Numerical results showed that the S3 mode had the lower threshold and the threshold gain would be largely varied by tuning the ratio of air hole radius/lattice constant (r/a). Based on calculations and experiments, PQCSELs show the opportunity to realize lower threshold lasers than typical PC laser for specific value of r/a and appropriate higher order band-edge modes.
Localized Lasing Mode in GaN Quasi-Periodic Nanopillars at Room Temperature
(2013-07-01)
Wu, Tzeng-Tsong
;
Chen, Chih-Cheng
;
Chen, Hao-Wen
;
Lu, Tien-Chang
;
Wang, Shing-Chung
In this paper, GaN quasi-periodic nanopillars were fabricated and investigated. The quasi-periodic nanopillars were realized by nanoimprint technique and selective area growth. Localized lasing mode was identified in the GaN quasi-periodic nanopillars. The threshold energy density and lasing wavelength were 40 mJ/cm(2) and 369 nm, respectively. The divergence angle and near-field lasing spot were measured to be 10.5 degrees and 3.6 mu m, respectively. The spontaneous emission coupling factor of localized lasing mode was estimated to be 9.4 x 10(-3). The mode patterns in the real and reciprocal spaces were calculated by the multiple scattering method to confirm the mode localization behavior.
Mode Localization in Defect-free GaN-based Bottom-up Photonic Quasicrystal Lasers
(2012)
Wu, Tzeng-Tsong
;
Chen, Chih-Cheng
;
Chen, Hao-Wen
;
Lu, Tien-Chang
;
Wang, Shing-Chung
GaN-based bottom-up photonic quasicrystal (PQC) lasers were realized and characterized. Photonic quasicrystal nanopillars were realized by nanoimprint technique and selective area growth. Highly localized mode was identified for the first time in GaN-based PQC lasers. (C) 2012 Optical Society of America
Professional Baseball Team Starting Pitcher Selection Using AHP and TOPSIS Methods
(2014-08-01)
Chen, Chih-Cheng
;
Lee, Yung-Tan
;
Tsai, Chung-Ming
;
管理科學系
;
Department of Management Science
Selecting starting pitchers is a strategic issue with a significant effect on the performance of a professional team. Choosing optimal starting pitchers from many alternatives is a multi-criteria decision-making (MCDM) problem. This study develops an evaluation model, based on the Analytic Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS), to help managers and coaches of a professional baseball team make the optimal selection for starting pitchers. The AHP was used to analyze the structure of starting-pitcher selection and determines weights of the criteria, whereas the TOPSIS method makes the final ranking. Empirical analysis illustrates model utilization for selecting starting pitchers. The results of this study demonstrate the effectiveness and feasibility of the proposed model.