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Effects of doping in the active region of 630-nm band GaInP-AlGaInP tensile-strained quantum-well lasers
(1998-09-01)
Yen, ST
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We theoretically analyze 630-nm band GaInP-AIGaInP tensile-strained quantum-well (QW) lasers with doping in the active region. The radiative current can be significantly reduced by introducing n-type doping in the active region. However, this advantage is reduced by the increase of the leakage current, As a result, the threshold current is reduced and the emission wavelength is shortened for multiquantum-well (MQW) lasers by n-type doping. But for single-quantum-well (SQW) lasers, because of the large increase of the leakage current, the threshold current increases with n-type doping.
Novel chirped multilayer quantum-dot lasers - art. no. 69970R
(2008)
Lin, G.
;
Chang, C. Y.
;
Tseng, W. C.
;
Lee, C. P.
;
Lin, K. F.
Chirped multilayer (N=10) QD lasers with 2-, 3- and 5-layer of longer-, medium-, and shorter-wavelength QD stacks, respectively, were grown in this work. Low threshold current density and high saturated modal gain were achieved in this specially designed QD structure. Empirical gain-current analysis was performed on this chirped multilayer QD structure for the first time. It was consistent with our spectral observations and provided valuable information on carrier recombination in chirped multilayer QD structure. Two novel spectral characteristics were discovered also for the first time. First, simultaneous two-wavelength lasing around threshold was observed under particular gain-loss condition at this specific multilayer structure of QD stacking numbers. Second, at cryogenic temperature, simultaneous two-wavelength lasing emissions switched from longer-wavelength lasing first to shorter-wavelength lasing first with increasing current injection. Non-uniform carrier distribution among chirped multilayer QD structure is evident at low temperature below 200 K from our analysis.
Plasmonic gap mode nanocavities at telecommunication wavelengths
(2014)
Cheng, Pi-Ju
;
Weng, Chen-Ya
;
Chang, Shu-Wei
;
Lin, Tzy-Rong
;
Tien, Chung-Hao
We analyze a plasmonic gap-mode Fabry-Perot nanocavity containing a metallic nanowire. The proper choice of the cladding layer brings about a decent confinement inside the active region for the fundamental and first-order plasmonic gap modes. We numerically extract the reflectivity of the fundamental and first-order mode and obtain the optical field inside the cavity. We also study the dependence of the reflectivity on the thickness of Ag reflectors and show that a decent reflectivity above 90 % is achievable. For such cavities with a cavity length approaching 1.5 pm, a quality factor near 150 and threshold gain lower than 1500 cm-1 are achievable.
Tunable multi-wavelength quantum dot external-cavity lasers
(2013)
Pai, Chen-Hung
;
Lin, Gray
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The chirped multilayer quantum-dot (QD) gain media are arranged in Fourier-transform external-cavity laser (FT-ECL) configuration. Novel slit designs select 2, 3, and 4 different wavelengths that are diffracted from the grating for optical feedback. Therefore, the dual-, triple-and quadruple-wavelength ECLs are demonstrated in this study. The resulted multi-wavelength lasing emissions are achieved under injected current of 100 mA (or 1.33 kA/cm(2)) with signal to amplified spontaneous emission (ASE) ratio over 20 dB. Around peak-gain wavelength of 12xx-nm range, the adjacent wavelength separation is over 50 nm for dual-wavelength lasing, up to 13 nm for triple-wavelength lasing, and about 4-5 nm for quadruple-wavelength lasing emissions. To further extend the wavelength separation for dual-wavelength lasing emissions, another modified scheme with two separate external mirrors are adopted and the achieved maximum value is about 126 nm in wavelength separation or over 25 THz in frequency difference. The terahertz (THz) generation by photomixing of dual-wavelength ECLs is also discussed in this study.
Cladding Effect on Hybrid Plasmonic Nanowire Cavity at Telecommunication Wavelengths
(2013-05-01)
Cheng, Pi-Ju
;
Weng, Chen-Ya
;
Chang, Shu-Wei
;
Lin, Tzy-Rong
;
Tien, Chung-Hao
In this paper, we investigate the effect of cladding layers on a hybrid plasmonic nanowire cavity. A decent confinement factor and moderate modal loss can be achieved for lasing. Within a certain index range of the cladding layer, the fundamental hybrid plasmonic mode is well confined inside the narrow gain region and becomes the most promising lasing mode. Our results also indicate that the mirror loss can be reduced if the refractive index of the cladding layer is properly chosen. An estimated cold-cavity quality factor of 87, corresponding to a threshold gain of about 1072 cm(-1), is achievable at a cavity length of 10.13 mu m for the lasing mode.
Wavelength Tuning by Bending a Flexible Photonic Crystal Laser
(2013-06-15)
Hsu, Kung-Shu
;
Chiu, Tzu-Ting
;
Lee, Po-Tsung
;
Shih, Min-Hsiung
;
光電工程學系
This study demonstrated mechanical wavelength fine-tuning of a flexible photonic crystal (PhC) laser. A triangular PhC structure was fabricated in an InGaAsP layer on top of a polydimethylsiloxane substrate. Experiments showed two lasing modes at symmetry points K and M in the first PhC band. The laser structure was bent along the Gamma - M direction and the lasing wavelength was fine-tuned by varying the bending radius. The lasing wavelength shift is attributed to PhC lattice distortion and its tuning behavior corresponds with the simulation results. This ultra-small, wavelength-tunable laser could function as a unique light source for integrated optoelectronic circuits.
Impact of thermal effects on simulation accuracy of nonlinear dynamics in semiconductor lasers
(2005-09-01)
Lim, CG
;
Iezekiel, S
;
Snowden, CM
;
光電工程學系
;
Department of Photonics
Simulations based on a carrier heating model are performed to investigate the behavior of a directly modulated 1.55-mu m InGaAsP distributed feedback (DFB) laser diode (LD). Results show that bandgap shrinkage has a significant effect on the simulated nonlinear behavior of LDs. However, the varying nature of lattice temperature and excess carrier energy relaxation is important to produce simulated results that agree with measured results.
Simulation of InGaN quantum well laser performance using quaternary InAlGaN alloy as electronic blocking layer
(2005-11-01)
Chang, YA
;
Luo, CY
;
Ku, HC
;
Kuo, YK
;
Lin, CF
Laser performance of an InGaN edge-emitting laser using a quaternary InAlGaN electronic blocking layer is investigated. Varying the aluminum (Al) composition in InAlGaN with a fixed indium (In) value (Al : In = 5 : 1) indicates that a lower threshold current and higher characteristic temperature (T(0)) value can be obtained when the Al composition is higher than 20%. When Al = 25%, the threshold current is reduced at the expense of a decreased To value from 149 to 130 K when the In composition increases from 1 to 7% in a temperature range of 300-370 K. The decreased T(0) value is mainly attributed to the increase in electronic leakage current.
Theoretical and experimental analysis on InAlGaAs/AlGaAs active region of 850-nm vertical-cavity surface-emitting lasers
(2006-01-01)
Chang, YA
;
Chen, JR
;
Kuo, HC
;
Kuo, YK
;
Wang, SC
In this study, the gain-carrier characteristics of In0.02Ga0.98As and InAlGaAs quantum wells (QWs) of variant In and Al compositions with an emission wavelength of 838 nm are theoretically investigated. More compressive strain, caused by higher In and Al compositions in InAlGaAs QW, is found to provide higher material gain, lower transparency carrier concentration, and transparency radiative current density over the temperature range of 25-95 degrees C. To improve the output characteristics and high-temperature performance of 850-nm verticalcavity surface-emitting laser (VCSEL), In(0.15)AI(0.08)Ga(0.77)As/ Al0.3Ga0.7As is utilized as the active region, and a high-bandgap 10-nm-thick Al-0.75 Ga0.25As electronic blocking layer is employed for the first time. The threshold current and slope efficiency of the VCSEL with A(10.7)SGa(0.25)As at 25 degrees C are 1.33 mA and 0.53 W/A, respectively. When this VCSEL is operated at an elevated temperature of 95 C, the increase in threshold current is less than 21 % and the decrease in slope efficiency is approximately 24.5%. A modulation bandwidth of 9.2 GHz biased at 4 mA is demonstrated.
Octagonal quasi-photonic crystal single-defect microcavity with whispering gallery mode and condensed device size
(2007-05-01)
Lee, Po-Tsung
;
Lu, Tsan-Wen
;
Tsai, Feng-Mao
;
光電工程學系
;
Department of Photonics
We propose a new single-defect microcavity which supports well-confined whispering gallery mode in octagonal quasi-photonic crystals (OQPC) by shifting the eight nearest air holes around the cavity. Lasing action is observed and compared with the calculated results obtained using the finite-difference time-domain method. We also investigate the threshold dependence on the number of lattice periods of this OQPC microcavity and compare it with triangular lattice photonic crystal (PC) microcavity with similar cavity size. The OQPC microcavity exhibits only a 36% increase of threshold when the number of lattice periods decreases from eight to four, which is more advantageous than the triangular lattice PC microcavity for the shrinkage of device size.

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