Tsin-Dong Lee

Characteristics of MOCVD- and MBE-grown InGa(N)As VCSELs

We report our results on InGaNAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) in the 1.3 ?m range. The epitaxial structures were grown on (1?0?0) GaAs substrates by metalorganic chemical vapour deposition (MOCVD) or molecular beam epitaxy (MBE). The nitrogen composition of the InGa(N)As/GaAs quantum-well (QW) active region is 0?0.02. The long-wavelength (up to 1.3 ?m) room-temperature continuous-wave (RT CW) lasing operation was achieved for MBE- and MOCVD-grown VCSELs. For MOCVD-grown devices with n- and p-doped distributed Bragg reflectors (DBRs), a maximum optical output power of 0.74 mW was measured for In0.36Ga0.64N0.006As0.994/GaAs VCSELs. A very low Jth of 2.55 kA cm?2 was obtained for the InGaNAs/GaAs VCSELs. The MBE-grown devices were made with an intracavity structure. Top-emitting multi-mode 1.3 ?m In0.35Ga0.65N0.02As0.98/GaAs VCSELs with 1 mW output power have been achieved under RT CW operation. A Jth of 1.52 kA cm?2 has been obtained for the MBE-grown In0.35Ga0.65N0.02As0.98/GaAs VCSELs, which is the lowest threshold current density reported. The emission characteristics of the InGaNAs/GaAs VCSELs were measured and analysed.

Crescent Waves in Optical Cavities

We theoretically and experimentally generate stationary crescent surface solitons pinged to the boundary of a microstructured vertical cavity surface emission laser by triggering the intrinsic cavity mode as a background potential. Instead of a direct transition from linear to nonlinear cavity modes, we demonstrate the existence of symmetry-breaking crescent waves without any analogs in the linear limit. Our results provide an alternative and general method to control lasing characteristics as well as to study optical surface waves.

Nonlinear localized modes in bandgap microcavities

We study experimentally an electrically pumped GaAs-based bandgap structure based on a vertical cavity surface emitting laser (VCSEL). We demonstrate that a microcavity embedded into this bandgap VCSEL structure supports localized optical modes without any holding beam. We propose a model of surface-structured VCSELs based on a reduced dissipative wave equation for describing electromagnetic modes in such semiconductor cavities and analyze a crossover between linear and nonlinear solitonlike cavity modes.

High-power broad-area InGaNAs/GaAs quantum-well lasers in the 1200 nm range

Broad-area InGaNAs/GaAs quantum-well (QW) edge-emitting lasers on GaAs substrates in the 1200 nm range are reported. The epitaxial layers of the InGaNAs/GaAs QW laser wafers were grown on n⁺-GaAs substrates by using metal-organic chemical vapor deposition (MOCVD). The thickness of the InGaNAs/GaAs QW layers is 70 Å/1200 Å. The indium content (x) of the In<inf>x</inf>Ga<inf>1−x</inf>N<inf>y</inf>As<inf>1−y</inf> QW layers is estimated to be 0.35 to 0.36, while the nitrogen content (y) is estimated to be 0.006 to 0.008. More indium content (In) and nitrogen content (N) in the InGaNAs QW layer enables the laser emission up to 1300 nm range. The epitaxial layer quality, however, is limited by the strain in the grown layer. The devices were made with different ridge widths from 5 to 50 µm. A very low threshold current density (J<inf>th</inf>) of 80 A/cm² has been obtained for the 50µm×500µm LD. A number of InGaNAs/GaAs epi-wafers were made into broad-area LDs. A maximum output power of 95 mW was measured for the broad-area InGaNAs/GaAs QW LDs. The variations in the output powers of the broad-area LDs are mainly due to strain the InGaNAs QW layers.

Enhanced directional lasing by the interference between stable and unstable periodic orbits

We demonstrate the idea of surface-assisted microstructures to tailor the modes and resulting emission from a dynamical localized vertical cavity surface emitting laser at room temperature. With a slightly mismatch between the surface structure and the native oxide cavity layer, near field intensity images corresponding to the spontaneous emission patterns, whispering-gallery modes (WGMs), dynamical localized modes (DLMs), and unidirectional light emissions are measured and identified in experiments and simulations. Moreover, the coherent superposition of WGM and DLM, i.e., stable and unstable periodic orbits, respectively, is reported to provide an alternative and general method to control lasing characteristics as well as to study quantum chaos in mesoscopic system.

Single-mode InGaAs photonic crystal vertical-cavity surface-emitting lasers emitting at 1170 nm

We have made MOCVD-grown InGaAs photonic crystal vertical-cavity surface-emitting lasers (PhC-VCSELs) for fiber-optic applications. Multi-mode InGaAs VCSELs have achieved a maximum power of over 1 mW. Single-mode characteristics of 0.18 mW of the PhC-VCSELs have been made by using the combined AlOx oxide layer with proton-implantion for better current confinement.

Low-Threshold-Current-Density, Long-Wavelength, Highly Strained InGaAs Laser Grown by Metalorganic Chemical Vapor Deposition

A long-emission-wavelength laser with multiple InGaAs/GaAs quantum wells without a strain-compensated barrier was grown by metalorganic chemical vapor deposition (MOCVD). InGaAs quantum well (QW) broad-area laser diodes with an emission wavelength of up to 1214 nm were realized. A measured room-temperature threshold current density of only 173 A/cm2 for a 2-mm-cavity device and a transparency current density of 66 A/cm2 were obtained. The internal quantum efficiency and laser cavity loss were 67% and 6 cm-1, respectively.

Production costing and reliability evaluation for composite systems with outages and uncertainties

Abstract A new method based on Monte Carlo simulation for composite power system production costing and reliability evaluation, considering apparatus outage probabilities and load forecast uncertainties, is presented. Random numbers are generated, according to appropriate laws, to simulate the state of the apparatus and the demand of the bus loads. Through successive application of the minimum cost flow algorithm, it is capable of handling the economic dispatch problem existing in the procedures. In this paper, the reliability of the system is measured in terms of expected demand not served (EDNS) and loss of load probability (LOLP). The EDNS and therefore the expected unserved energy (EUE) associated with an expansion plan can be evaluated further as an equivalent penalty cost due to service interruption. This benefits the application of the proposed method for selection between alternatives in power system planning. Another advantage of this method is that an expected power flow pattern is generated as the byproduct. Application of the method is demonstrated using the IEEE five-bus test system.

Highly Strained InGaAs/GaAs Quantum Well Vertical-Cavity Surface-Emitting Lasers

We report our results on the highly strained InGaAs/GaAs quantum well (QW) vertical-cavity surface-emitting lasers (VCSELs) in the 1140 to 1250 nm range. The epitaxial structures were grown on (100)GaAs substrates by metal-organic chemical vapor deposition (MOCVD). A maximum output power of more than 6.3 mW has been demonstrated. The spectral characteristics were also measured and analyzed.

Characteristics of InGa(N)As VCSELs for fiber optic applications

We report our results on InGaNAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) for fiber-optic applications in the 1.3 μm range. The epitaxial structures were grown on (100) GaAs substrates by MBE or MOCVD. The nitrogen composition of the InGaNAs/GaAs quantum-well (QW) active region is 0 to 0.02. Long-wavelength (up to 1.3 μm) room-temperature continuous-wave (RT CW) lasing operation was achieved for MBE and MOCVD-grown VCELs. For MOCVD-grown devices with n- and p-doped distributed Bragg reflectors (DBRs), a maximum optical output power of 0.74 mW was measured for In0.36Ga0.64N0.006As0.994/GaAs VCSELs. The MBE-grown devices were made with intracavity structure. Top-emitting multi-mode 1.3 μm In0.35Ga0.65N0.02As0.98/GaAs VCSELs with 1mW output power have been achieved under RT CW operation. Emission characteristics of InGaNAs/GaAs VCSELs were measured and analyzed.