Browsing by Author "Wang, SC"

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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.
10 Gb/s single-mode vertical-cavity surface-emitting laser with large aperture and oxygen implantation
(2004-08-01)
Lai, FI
;
Hsueh, TH
;
Chang, YH
;
Kuo, HC
;
Wang, SC
High-speed single transverse mode 850 nm vertical cavity surface emitting lasers (VCSELs) with large emission aperture with a diameter of 8 Am were fabricated. These VCSELs exhibit good performance with threshold currents of 1.5 mA, a single transverse mode emission within the full operational range and a maximum output power of 3.8 mW. The large aperture is advantageous to these VCSELs with a smaller dynamic resistance (60 Omega) than that of conventional single-mode VCSEL. These single-mode VCSELs also demonstrate superior high-speed performance up to 10 Gb s(-1).
10 Gbps InGaAs : Sb-G-aAs-GaAsP quantum well vertical cavity surface emitting lasers with 1.27 mu m emission wavelengths
(2005-04-01)
Chang, YH
;
Kuo, HC
;
Chang, YA
;
Chu, JT
;
Tsai, MY
InGaAs:Sb-GaAs-GaAsP vertical cavity surface emitting lasers (VCSELs) with 1.27 mu m emission wavelength were grown by metal-organic chemical vapor deposition (MOCVD) and exhibited excellent performance and temperature stability. The threshold current changes from 1.8 to 1.1 mA and the slope efficiency falls less than similar to 35% as the temperature is increased from room temperature to 70 degrees C. With a bias current of only 5 mA, the 3 dB modulation frequency response was measured to be 8.36GHz, which is appropriate for 10Gb/s operation. The maximal bandwidth is measured to be 10.7GHz With a modulation current efficiency factor (MCEF) of similar to 5.25 GHz/(mA) 1/2. Bit error rates of less than 10(-12) are demonstrated for 10 Gb/s data transmission from 25 degrees C to 70'C. We also accumulated life test data up to 1000 h at 70 degrees C/10 mA.
A diode-pumped high power Q-switched and self-mode-locked Nd : YVO4 laser with a LiF : F-2(-) saturable absorber
(2001-08-01)
Chen, YF
;
Tsai, SW
;
Wang, SC
;
Chen, J
;
電子物理學系
Simultaneous mode-locking and Q-switching has been accomplished in a diode-pumped Nd:YVO4/LiF:F-2(-) laser. At an absorbed pump power of 23.6 W, the average output power was 6.0W and the repetition rate of the Q-switched pulse was 260 kHz. A depth of mode-locking of 100% was obtained and there was no satellite pulse between mode-locked pulse trains. The mode-locked pulse inside the Q-switched pulse had a repetition rate of approximately 148 MHz and its average duration was estimated to be around 75 ps.
A novel method to improve VCSELs oxide-confined aperture uniformity using selective As+-implanted underlying layer
(2006-05-10)
Huang, HW
;
Kao, CC
;
Chang, YA
;
Kuo, HC
;
Laih, LH
We report the utilization of an selective As+-implanted underlying layer and regrowth method to enhance and control the wet thermal oxidation rate for 850 nm oxide-confined VCSEL. The oxidation rate of the As'-implanted device showed a four-fold increase over the non-implanted one at the As' dosage of 1 x 10(16) cm(-1) and the oxidation temperature of 400 degrees C. The 50 side-by-side As'-implanted oxide-confined VCSELs fabricated using the method achieved very uniform performance with a deviation in threshold current Of Delta I-th similar to 0.2 mA and slope-efficiency of Delta S.E. similar to 3%. Finally, we accumulated life test data for oxide-confined VCSELs with As'-implanted underlying layer up to 1000 h at 80 degrees C/15 mA. (c) 2005 Elsevier B.V. All rights reserved.
A simple passive-alignment packaging technique for laser diode modules
(1998-10-01)
Wang, SC
;
Chi, S
;
Cheng, WH
;
光電工程學系
;
Department of Photonics
A simple passive-alignment packaging technique has been developed for the fabrication of a laser diode connection to a singlemode fiber pigtail. The fabrication begins with a multimode fiber soldered in a U-groove with 5 mu m tolerance. Then the laser chip with a junction-up die-bond is passively aligned to a multimode fiber and converted into a singlemode fiber. The tolerance as measured for the multimode fiber at 10% loss of maximum coupling from the laser diode is 11 mu m. Because the tolerance of the multimode fiber from the laser chip is larger (11 mu m) than that of the fiber in the U-groove (5 mu m), this passive alignment is easily obtained. In contrast to other passive-alignment techniques, the advantages of this technique are that it is less sensitive to transverse misalignment and requires no complicated alignment marks. From laser to multimode fiber a coupling efficiency of greater than 80% and a bandwidth of greater than 1 GHz have been achieved. In this package, the overall coupling efficiency from laser to singlemode fiber is 16%, The resulting laser module with compact size and fewer components should make it highly suitable for use in low-cost telecommunication applications, (C) 1998 Elsevier Science S.A. All rights reserved.
A simple passive-alignment packaging technique for laser diode modules
(1998-10-01)
Wang, SC
;
Chi, S
;
Cheng, WH
;
光電工程研究所
;
Institute of EO Enginerring
A simple passive-alignment packaging technique has been developed for the fabrication of a laser diode connection to a singlemode fiber pigtail. The fabrication begins with a multimode fiber soldered in a U-groove with 5 mu m tolerance. Then the laser chip with a junction-up die-bond is passively aligned to a multimode fiber and converted into a singlemode fiber. The tolerance as measured for the multimode fiber at 10% loss of maximum coupling from the laser diode is 11 mu m. Because the tolerance of the multimode fiber from the laser chip is larger (11 mu m) than that of the fiber in the U-groove (5 mu m), this passive alignment is easily obtained. In contrast to other passive-alignment techniques, the advantages of this technique are that it is less sensitive to transverse misalignment and requires no complicated alignment marks. From laser to multimode fiber a coupling efficiency of greater than 80% and a bandwidth of greater than 1 GHz have been achieved. In this package, the overall coupling efficiency from laser to singlemode fiber is 16%, The resulting laser module with compact size and fewer components should make it highly suitable for use in low-cost telecommunication applications, (C) 1998 Elsevier Science S.A. All rights reserved.
AlGaInP light-emitting diodes with stripe patterned omni-directional reflector
(2006-02-01)
Lee, YJ
;
Lu, TC
;
Kuo, HC
;
Wang, SC
;
Liou, MJ
An n-side-up AlGaInP-based light-emitting diode (LED) with a stripe-patterned omni-directional reflector (ODR) was fabricated by adopting the adhesive-layer bonding scheme. Comparing to the conventional ODR LED, the stripe-patterned ODR LED significantly enhanced the output power with an only slight higher forward voltage. This improvement was analyzed by the scanning near-field optical microscope (SNOM) and could be attributable to the geometrical shape of stripe patterns that redirects the guided light towards to the escaping cone of the LED surface. The optimized dimension of stripe patterns was also calculated by simply modeling a LED dice with a stripe-patterned ODR structure, according to optical ray-tracing method.
Aluminum incorporation into AlGaN grown by low-pressure metal organic vapor phase epitaxy
(2006-05-15)
Huang, GS
;
Yao, HH
;
Lu, TC
;
Kuo, HC
;
Wang, SC
Aluminum (Al) incorporation in AlxGa1-xN films grown by low-pressure metal organic vapor phase epitaxy using trimethylaluminum (TMAl) and trimethylgallium as group III precursors has been systematically studied. The solid phase Al composition of the AlxGa1-xN films varied nonlinearly with the Al gas phase composition. The incorporation kinetics of AlxGa1-xN alloy has been analyzed by using an adsorption-trapping model. Two parameters were used to characterize the properties of Al incorporation, i.e., the capture radius and the adsorption time of Al atoms. An exponential function of the Al composition of the AlxGa1-xN films versus the TMAl gas flow rate was obtained. It was demonstrated that the adsorption time of the Al atom was larger than the growth time of one atomic layer. The effects of ammonia flow rate, crystal growth rate, and growth temperature on the adsorption parameters were also discussed. (c) 2006 American Institute of Physics.
An optically pumped blue GaN-based vertical-cavity surface emitting laser employing AIN/GaN and Ta2O5/NO2 distributed bragg reflectors
(2005)
Kao, CC
;
Yao, HH
;
Peng, YC
;
Lu, TC
;
Kuo, HC
The laser action of GaN-based VCSEL with 3-lambda cavity and hybrid DBR mirrors, consisting of AlN/GaN and Ta2O5/SiO2 DBR was achieved under the optical pumping at room temperature. The laser emits 448nm blue wavelength with a linewidth of 0.25nm above threshold.
As+-implanted AlGaAs oxide-confined VCSEL with enhanced oxidation rate and high performance uniformity
(2004-06-01)
Laih, LH
;
Kuo, HC
;
Lin, GR
;
Laih, LW
;
Wang, SC
We report the utilization of an As+-implanted Al-GaAs region and regrowth method to enhance and control the wet thermal oxidation rate for 850-nm oxide-confined vertical-cavity surface-emitting laser (VCSEL). The oxidation rate of the As+-implanted device showed a four-fold increase over the nonimplanted one at the As+ dosage of 1 x 10(16) cm(-3) and the oxidation temperature of 400 degreesC. 50 side-by-side As+-implanted oxide-confined VCSELs fabricated using the method achieved very uniform performance with a deviation in threshold current of DeltaI(th) similar to 0.2 mA and slope-efficiency of DeltaS.E. similar to 3%.
Atomic force microscope study of GaN films grown by hydride vapor phase epitaxy
(1999)
Fang, HM
;
Wang, YK
;
Tsai, RY
;
Chu, CF
;
Wang, SC
We report the results of the investigation of the structural, surface morphological, and optical properties of GaN films grown by hydride vapor phase epitaxy. These films were grown on sapphire substrate with no intentional dopings. These as-grown GaN film samples with thickness ranging from 5.58 mu m to 14.9 mu m were investigated under room temperature conditions. The surface morphology of these films was investigated using an atomic force microscopy (AFM). The root mean square (RMS) values of surface roughness range from 0.281 nm to 0.133 nm. The thicker films show lower defect counts with a defect density of about 2 x 10(8) cm(-2). The structural property of these films was measured by double crystal X-ray diffraction (DC-XRD). The full width at half maximum (FWHM) of X-ray diffraction angle decreases as the film thickness increases with a lowest FWHM of about 265.5 arcsec. The optical properties of these films were investigated by photoluminescence (PL) measurement at room temperature. The results show a dominant near band-edge UV emission peak that increases with the film thickness with very weak yellow emission band.
Beryllium-implanted P-type GaN with high carrier concentration
(2001-05-01)
Yu, CC
;
Chu, CF
;
Tsai, JY
;
Lin, CF
;
Lan, WH
We report the results of beryllium implantation in Mg-doped GaN to obtain a high hole concentration and lower activation energy for Mg. The metal organic chemical vapor deposition (MOCVD)-grown Mg-doped GaN samples were implanted with Be ions at two different energies of 50 keV and 150 keV and a dose of 10(14) cm(-2). The implemented samples were subsequently annealed at 1100 degreesC for 60 s. The annealed samples showed an increase of hole concentration by three orders of magnitude from the non-implanted value of 5.5 x 10(16) to 8.1 x 10(19) cm(-3) as determined by Hall measurement. The activation energy of Mg dopants for the implanted annealed samples estimated from the temperature dependence of the photoluminescence data is about 170 meV, which is nearly 30% lower than that for the as-grown samples.
Broad-band (>= 20 GHz) laser-diode-based optoelectronic microwave phase shifter
(1998-10-01)
Lin, GR
;
Hwang, TS
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Chuang, YH
;
Wang, SC
;
Pan, CL
We demonstrate a new type of broad-band microwave phase shifter with superior performance at frequencies up to 20 GHz. This is implemented by simply adding an offset voltage prior to the loop filter (LF) in a laser-diode-based digital optoelectronic phase-locked loop (OEPLL), Accurate control of the phase of microwave signals with a continuously tunable range exceeding 640 degrees (similar to 3.6 pi) is achieved. The phase fluctuation and long-term drift of ally desired phase shift are as small as +/-0.4 degrees and 0.08 degrees, respectively, at 20 GHz, The relative phase instability can be maintained within 0.09 degrees while operating in a phase-shift-keying (PSK) scheme, We also demonstrate accurate control of relative phase difference between dual phase-locked microwave sources using the phase shifter. Our results indicate potential application of this broad-band optoelectronic phase shifter in a phased-array antenna system.
Catalyst-free GaN nanorods grown by metalorganic molecular beam epitaxy
(2006-05-01)
Kuo, SY
;
Kei, CC
;
Hsiao, CN
;
Chao, CK
;
Lai, FI
High-density GaN nanorods with outstanding crystal quality were grown on c-sapphire substrates by radio-frequency plasma-assisted metalorganic molecular beam epitaxy under catalyst- and template-free growth condition. Morphological and structural characterization of the GaN nanorods was employed by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HRTEM). These results indicate that the rod number density can reach 1 x 10(10) cm(-2) and the nanorods are well-aligned with preferentially oriented in the c-axis direction. Meanwhile, no metallic (Ga) droplet was observed at the end of the rods, which is the intrinsic feature of vapor-liquid-solid method. Nanorods with no traces of any extended defects, as confirmed by TEM, were obtained as well. In addition, optical investigation was carried out by temperature- and power-dependent micro-photoluminescence (mu-PL). The PL peak energies are red-shifted with increasing excitation power, which is attributed to many-body effects of free carriers under high excitation intensity. The growth mechanism is discussed on the basis of the experimental results. Catalyst-free GaN nanorods presented here might have a high potential for applications in nanoscale photonic devices.
Characteristics of monolithically integrated two-wavelength laser diodes with aluminum-free active layers
(2001-02-12)
Lu, TC
;
Fu, R
;
Shieh, HM
;
Huang, KJ
;
Wang, SC
A two-wavelength integrated laser diode (TWINLD) with aluminum-free active areas (AAA) has been realized by monolithically combining two different laser material structures in a single chip utilizing the metalorganic chemical vapor deposition growth and regrowth techniques. The single TWINLD chip comprises two ridge wave-guide lasers, one is an InGaP/InGaAlP material structure for a 650 nm red laser, and another is an InGaAsP/AlGaAs material structure with AAA for a 780 nm infrared laser. The chip geometry is 300 mum long and 300 mum wide with a separation of 150 mum between two laser emission spots. The ridge widths are 3.5 and 2 mum for the red and IR laser, respectively, and both lasers emit a single transverse mode with a threshold current of 12 mA for a 650 nm laser and 14 mA for a 780 nm laser under continuous wave operation condition. (C) 2001 American Institute of Physics.
Characteristics of optical properties of the interrupt growth method on InGaN/GaN MQW structures
(2000)
Lin, CF
;
Shu, CK
;
Lee, WH
;
Wen, TC
;
Chu, CF
The growth method and material properties of InGaN/GaN multiple quantum well (MQW) structures were studied in this experiment. The InGaN/GaN-MQW structure were deposited above the 2 mum-thick high quality GaN layers (with background carrier concentration was about 3.2 x 10(16) cm(-3)) on Al2O3 substrates. The interrupt growth time was 10 sec between GaN barrier layer and InGaN well growth at 690 degreesC. The stronger intensity and sharper photoluminescence (PL) spectra was observed from the interrupt growth MQW structures. The mean deviation of the PL peak position was lower than 1% by using the interrupt growth MQW structures at difference growth temperature. The PL spectra was become broaden and weaker by reducing the interrupt time during InGaN/GaN growth. The thickness of one pair InGaN/GaN was also identified by DCX-ray measurement and the growth rate InGaN layer was also calculated in this experiment.
Characteristics of stable emission GaN-based resonant-cavity light-emitting diodes
(2004-01-19)
Lin, CF
;
Yao, HH
;
Lu, JW
;
Hsieh, YL
;
Kuo, HC
The resonant-cavity light-emitting diode (RC-LED) structure was grown by MOCVD. The structure of RC-LED consisted of a 3lambda InGaN/GaN MQW LED cavity between the top TiO2/SiO2 DBR (81.7%, reflectance) and the bottom AlN/GaN DBR (90.4%) stack. A stable 410 nm emission peak and a low thermally induced red-shift effect (0.12 nm/kA/cm(2)) were measured by varying the injection current density. The light output power of the full RC-LED device was three times higher than the RC-LED without top TiO2/SiO2 DBR layers under 600 A/cm(2) inject current density. The narrow line width of 7.4 nm, emission peak localization at 410 nm, and three times higher output power were caused by the resonance effect in this vertical cavity structure. (C) 2003 Published by Elsevier B.V.
Characterization of InGaN/GaN multiple quantum well nanorods fabricated by plasma etching with self-assembled nickel metal nanomasks
(2005-04-01)
Hsueh, TH
;
Huang, HW
;
Kao, CC
;
Chang, YH
;
Ou-Yang, MC
High-density (3.0 x 1010 cm (-2)) InGaN/GaN Multiple quantum well (MQW) nanorods were fabricated from an as-grown bulk light-emitting diode structure by inductively coupled plasma dry etching with self-assembled nickel metal nanomasks. The self-assembled nickel metal nanomasks were formed by rapid thermal annealing of a nickel metal film at 850 degrees C for 1 min. The influence of the thicknesses of the Ni metal film on the dimensions and density of the nanorods was also investigated. The structural and optical properties of the InGaN/GaN MQW nanorods were established using field emission scanning electron microscopy, transmission electron microscopy and photoluminescence measurements. The diameters and heights of nanorods were estimated to be 60 to 100nm and more than 0.28 mu m, respectively. The peak emission wavelength of the nanorods showed a blue shift of 5.1 nm from that of the as-grown bulk. An enhancement by a factor of 5 in photoluminescence intensity of the nanorods compared with that of the as-grown bulk was observed. The blue shift is attributed to strain relaxation in the wells after dry etching, the quantum confinement effect, or a combination of the two, which results in the enhancement of emission intensity.
Comparison of high-resistivity ZnO films sputtered on different substrates
(2002-04-01)
Lin, GR
;
Wang, SC
;
光電工程學系
;
Department of Photonics
The structural and electrical properties of (002)-oriented high-resistivity ZnO films with luminescent peaks ranging from 3 80 nm to 415 nm grown on SiO2/Si, Si and Coming 7059 glass substrates by radio-frequency magnetron-assisted sputtering are determined. The X-ray diffraction results reveal that the ZnO/glass sample has a narrow normalized intensity of full-width at half maximum (FWHM) compared to other samples. The photoluminescence spectra show that the band-gap energy of the ZnO/glass sample is similar to that of the ZnO bulk standard; however, a smaller band-gap energy of 2.987 eV of the ZnO/SiO2/Si sample due to the defect-induced lattice expansion effect is observed. The ZnO/glass sample has better crystallinity, but exhibits lower contact resistance and sheet resistance. In particular, the metal-semiconductor-metal diode fabricated on the ZnO/Si sample is found to exhibit a relatively larger contact resistance, sheet resistance, and specific contact resistivity of 1.02 x 10(9) Omega, 3.8 x 10(10) Omega/square, and 1.54 x 10(3) Omega-cm(2), respectively.