Browsing by Author "Lin, KF"

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1.3 mu m quantum dot vertical-cavity surface-emitting laser with external light injection
(2005-10-27)
Peng, PC
;
Chang, YH
;
Kuo, HC
;
Tsai, WK
;
Lin, G
A 1.3 mu m quantum dot vertical-cavity surface-emitting laser (QD VCSEL) with external light injection is presented, having been experimentally demonstrated. The QD VCSEL is fabricated on GaAs substrate. The 3 dB frequency response of the QD VCSEL based on the TO-Can package is enhanced from the free-running 1.75 to 7.44 GHz with the light injection technique.
1.3-mu m InAs-InGaAs quantum-dot vertical-cavity surface-emitting laser with fully doped DBRs grown by MBE
(2006-01-01)
Yu, HC
;
Wang, JS
;
Su, YK
;
Chang, SJ
;
Lai, FI
We report InAs-InGaAs quantum-dot vertical-cavity surface-emitting lasers (VCSELs) grown by molecular beam epitaxy with fully doped n- and p-doped AlGaAs distributed Bragg reflectors and including an AlAs layer to form a current and waveguiding aperture. The metal contacts are deposited on a topmost p(+) (GaAs)-Ga-. contact layer and on the bottom surface of the n(+)-GaAs substrate. This conventional selectively oxidized top-emitting device configuration avoids the added complexity of fabricating intracavity or coplanar ohmic contacts. The VCSELs operate continuous-wave at room temperature with peak output powers of 0.33 mW and differential slope efficiencies up to 0.23 W/A. The peak lasing wavelengths are near 1.275 mu m, with a sidemode suppression ratio of 28 dB.
Band gap engineering and spatial confinement of optical phonon in ZnO quantum dots
(2006-06-26)
Lin, KF
;
Cheng, HM
;
Hsu, HC
;
Hsieh, WF
;
光電工程學系
Both band gap engineering and spatial confinement of optical phonon were observed depending upon the size of ZnO quantum dots at room temperature. Size-dependent blueshifts of photoluminescence and absorption spectra reveal the quantum confinement effect. The measured Raman spectral shift and asymmetry for the E-2(high) mode caused by localization of optical phonons agree well with that calculated by using the modified spatial correlation model. (c) 2006 American Institute of Physics.
Band gap variation of size-controlled ZnO quantum dots synthesized by sol-gel method
(2005-06-30)
Lin, KF
;
Cheng, HM
;
Hsu, HC
;
Lin, LJ
;
Hsieh, WF
ZnO quantum dots were synthesized successfully via a simple sol-gel method. The average size of quantum dots can be tailored using well-controlled concentration of zinc precursor. Size-dependent blue shifts of photoluminescence and absorption spectra revealed the quantum confinement effect. The band gap enlargement is in agreement with the theoretical calculation based on the effective mass model. Furthermore, as the particle size decreases, we observed an increase in the size-dependent Stokes shift of the photoluminescence peak relative to the absorption onset. (c) 2005 Elsevier B.V. All rights reserved.
Enhanced resonant Raman scattering and electron-phonon coupling from self-assembled secondary ZnO nanoparticles
(2005-10-06)
Cheng, HM
;
Lin, KF
;
Hsu, HC
;
Lin, CJ
;
Lin, LJ
Self-assembled secondary ZnO nanoparticles, recognized with the agglomeration of crystalline subcrystals, are successfully synthesized by a simple sol-gel method. TEM images display that one artificial cluster behaves in a single-crystal-like wurtzite structure because subcrystals coagulate as the same crystal orientation. Moreover, from the resonant Raman scattering, the as-grown sample exhibits phonon red shift; meanwhile, the coupling strength between electron and longitudinal optical phonon, determined by the ratio of second to first-order Raman scattering cross sections, diminishes compared with the samples after postannealing at 350 and 500 degrees C. The size dependence of electron-phonon coupling is principally as a result of the Frohlich interaction.
Interfacial reactions between Ti-6Al-4V alloy and zirconia mold during casting
(1999-12-01)
Lin, KF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The interface of Ti-6Al-4V casting and ZrO2 mold with silica binder was investigated by using electron probe microanalyses (EPMA), X-ray diffraction (XRD), and analytical transmission electron microscope (TEM). The interfacial reactions were proceeded by the penetration of liquid titanium through open pores near the mold surface. The metal side consisted of an alpha-phase layer on the top of the typical alpha + beta two-phase substrate. In the ceramic side, zirconia was reduced by titanium to form oxygen-deficient zirconia ZrO2-x and evolved a gaseous phase (presumably oxygen). The SiO2 binder, dissolved in the ZrO2 mold, could react with titanium to form Ti5Si3 in the metal side. Meanwhile, titanium could transform to titanium suboxides TiyO (y greater than or equal to 2) and the lower phase boundary of cubic ZrO2-x was shifted to ZrO1.76. Some amount of the stabilizer CaO, dissolved in Ti along with ZrO2, could react with Ti(O) to form Ca3Ti2O7 and CaAl4O7 in the reaction zone. (C) 1999 Kluwer Academic Publishers.
Interfacial reactions between zirconia and titanium
(1998-10-13)
Lin, KF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Molecular-beam-epitaxy growth of high-quality InGaAsN/GaAs quantum well lasers emitting at 1.3 mu m
(2004-11-01)
Wang, JS
;
Hsiao, RS
;
Lin, G
;
Lin, KF
;
Liu, HY
Molecular-beam-epitaxy growth of high structural and optical-quality InGaAsN/GaAs quantum wells (QW) has been investigated. The material quality can be improved significantly by using low-temperature growth to suppress the phase separation. High-performance ridge-waveguide InGaAsN/GaAs single QW lasers emitting at 1.3 mum have been demonstrated. Infinite-cavity-length threshold-current density of 400 A /cm(2), internal quantum efficiency of 96%. and a slope efficiency of 0.67 W/A for a cavity length L=1 mm were obtained. A TO46 packaging laser shows sin-le lateral-mode kink-free output power of more than 200 mW with a maximum total wallplug efficiency of 29% at room temperature under continuous wave (cw) operation. Moreover. 1.3 Am InGaAsN/GaAs QW vertical-cavity surface-emitting lasers with a threshold current density lower than 2 KA/cm(2) at room temperature have been achieved. We obtained multimode cw output power and slope efficiency in excess of 1 mW and 0.15 W/A. respectively. (C) 2004 American Vacuum Society.
Single mode 1.3 mu m InGaAsN/GaAs quantum well vertical cavity surface emitting lasers grown by molecular beam epitaxy
(2004-12-01)
Hsiao, RS
;
Wang, JS
;
Lin, KF
;
Wei, L
;
Liu, HY
The growth by molecular-beam-epitaxy of high-quality 1.3 mum InGaAsN/GaAs quantum wells (QW) intra-cavity contacted vertical cavity surface emitting lasers (VCSELs) was demonstrated. Low-temperature growth, which suppresses the phase separation significantly improves material quality in the active region. Room-temperature continuous wave (RT-CW) single mode output power of 0.75 mW with an initial slope efficiency of 0.17 W/A and a side mode suppression ratio of 40 dB at a lasing wavelength of as long as 1304 nm were obtained.
Single-mode monolithic quantum-dot VCSEL in 1.3 mu m with sidemode suppression ratio over 30 dB
(2006-03-01)
Chang, YH
;
Peng, PC
;
Tsai, WK
;
Lin, G
;
Lai, F
We present monolithic quantum-dot vertical-cavity surface-emitting lasers (QD VCSELs) operating in the 1.3-mu m optical communication wavelength. The QD VCSELs have adapted fully doped structure on GaAs substrate. The output power is similar to 330 mu W with slope efficiency of 0.18 W/A at room temperature. Single-mode operation was obtained with a sidemode suppression ratio of > 30 dB. The modulation bandwidth and eye diagram in 2.5 Gb/s was also presented.
Size dependence of band gap variation and electron-phonon coupling in ZnO quantum dots
(2005)
Hsieh, WF
;
Cheng, HM
;
Lin, KF
;
Hsu, HC
;
光電工程學系
Photoluminescence and resonant Raman scattering (RRS) were investigated in various sizes of ZnO quantum dots. The size dependent shift of exciton emission reveals quantum confinement effect as changing the band gap. Besides, it was also found the enhancement of RRS intensity and electron-phonon coupling diminishes with decreasing particle's diameter.
Size dependence of photoluminescence and resonant Raman scattering from ZnO quantum dots
(2006-06-26)
Cheng, HM
;
Lin, KF
;
Hsu, HC
;
Hsieh, WF
;
光電工程學系
ZnO quantum dots (QDs) of controlled sizes have been fabricated by a simple sol-gel method. The blueshift of room-temperature photoluminescence measurement from free exciton transition are observed decreasing with the QD size that is ascribed to the quantum confinement effect. From the resonant Raman scattering, the coupling strength between electron and longitudinal optical phonon, deduced from the ratio of the second- to the first-order Raman scattering intensity, diminishes with reducing the ZnO QD diameter. The size dependence of electron-phonon coupling is principally a result of the Frohlich interaction.
Transmission electron microscope investigation of the interface between titanium and zirconia
(1999-11-01)
Lin, KF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The interfaces between 3-mol%-yttria-partially-stabilized zirconia and commercially pure titanium after reaction at 1750 degrees C were analyzed with a scanning electron microscope and an analytical transmission microscope. Zirconia was reduced to oxygen-deficient zirconia (ZrO2-x) with an O/Zr ratio as low as 1.53, causing the evolution of oxygen. Part of the oxygen could accumulate at grain boundaries, the remainder being dissolved in titanium as alpha-Ti(O). An ordered titanium suboxide (Ti3O) could be formed from a solid solution of alpha-Ti(O) during cooling. A fine crystalline ZrO2-x phase (O/Zr approximate to 2) was also found along with alpha-Zr near the interface on the zirconia side. The alpha-Zr was twinned with one of the twin planes being indexed as {10 (1) over bar 2}. The yttria stabilizer was excluded from zirconia as the reaction was progressing, existing as oxygen-deficient yttria, Extensive dissolution of zirconia in titanium gave rise to the formation of alpha-Ti(Zr,O) solid solution. On cooling, lamellae of Ti2ZrO precipitated from alpha-Ti(Zr,O) with an orientation relationship of {110}(Ti2Zro)//{100}(alpha-Ti) and [111](Ti2ZrO)//[011](alpha-Ti).