Woonho Seo - Academia.edu (original) (raw)

Papers by Woonho Seo

本发明提供了一种使用液晶微透镜阵列的打印头以及使用该打印头的图像形成设备。通过选择性地将光发射到感光体的各个图像点来形成潜像的打印头包括用于发射光的照射单元和介于照射单元和感光体之间的液晶微透... more 本发明提供了一种使用液晶微透镜阵列的打印头以及使用该打印头的图像形成设备。通过选择性地将光发射到感光体的各个图像点来形成潜像的打印头包括用于发射光的照射单元和介于照射单元和感光体之间的液晶微透镜阵列。微透镜阵列选择性地使从照射单元发出的光的一部分会聚，并且将其引导到感光体上的与潜像对应的图像点上。图像形成设备包括：感光体，用于在其上形成潜像；打印头，用于通过选择性地将光发射到感光体的各个图像点来形成潜像；显影单元，用于将显影剂供应到感光体上以形成与潜像对应的显影图像；转印单元，用于将在感光体上形成的显影图像转印到打印介质上；熔化单元，用于使显影图像熔化到打印介质上。

EQEC '05. European Quantum Electronics Conference, 2005.

By the development of crystal growth technology, various kinds of semiconductor materials are use... more By the development of crystal growth technology, various kinds of semiconductor materials are used to realize the photonic devices of wide wavelength ranges. This article discusses the optical properties of AlGaN/GaN and ZnMgO/ZnO quantum wells for an application of short-wavelength lasers theoretically.

Solid State Communications, 2001

A theoretical analysis of the many body effects on the linewidth enhancement factor of the InGaAs... more A theoretical analysis of the many body effects on the linewidth enhancement factor of the InGaAs/InP strained quantum wire lasers is presented here. The theoretical approach is based on the semiconductor Bloch equations, where the dephasing process is treated at the level of the quantum kinetic theory. Electron±hole Coulomb correlation leads to the reduction of gain spectrum and refractive index change, contrary to the well known results for quantum well and bulk systems. The linewidth enhancement factor is overestimated and increases with the increasing carrier density in free-carrier model. But it is lowered and nearly constant with the increasing carrier density in the microscopic model.

Semiconductor Lasers and Laser Dynamics, 2004

The linewidth enhancement factors of lattice-matched 1.5 µm wavelength InGaNAs/GaAs and InGaAs/In... more The linewidth enhancement factors of lattice-matched 1.5 µm wavelength InGaNAs/GaAs and InGaAs/InP singlequantum-well structures have been calculated using microscopic theory including many-body effects and a 10x10 effective-mass Hamiltonian. For applications which require high gain and carrier densities, InGaNAs/GaAs quantum wells have a much lower linewidth enhancement factor over a temperature range 300-400 K than InGaAs. The linewidth enhancement factor of InGaNAs is almost independent of both carrier density and temperature compared with InGaAs. The small-signal modulation characteristics of these 1.5µm lattice-matched structures and their temperature dependence have also been calculated. It is found that the maximum bandwidth of the InGaNAs/GaAs quantum well lasers is about 2.3 times larger than that of the InGaAs/InP quantum well lasers due to the high differential gain. The slope efficiency for the 3dB bandwidth as a function of optical density is twice as large for InGaNAs/GaAs as for InGaAs/InP quantum well lasers.

SPIE Proceedings, 2004

The use of a fully two-dimensional waveguide analysis of the optical modes in a self-pulsating la... more The use of a fully two-dimensional waveguide analysis of the optical modes in a self-pulsating laser is described. We show that there is a need for such an analysis as the effective index model often used for modeling semiconductor lasers is shown not to provide a correct optical mode when the lateral waveguide is only weakly guiding. An efficient technique for solving the large and sparse matrix calculation in the two-dimensional model, the implicitly restarted Arnoldi method, is used and shown to be useful for the repetitive calculation necessary to describe the laser dynamics. We find that the optical field and optical gain show a variation in the pulse cycle and that this variation that occurs due to the change in carrier density, is responsible for the development of self-pulsation in the diode device.

Opto-Ireland 2005: Optoelectronics, Photonic Devices, and Optical Networks, 2005

A complete design of 1.3 µm AlGaInAs/InP narrow stripe semiconductor lasers for self-pulsating op... more A complete design of 1.3 µm AlGaInAs/InP narrow stripe semiconductor lasers for self-pulsating operation is realised by using a 2×1D simulation model. This numerical model is based on the effective index method and self-sustained pulsation mechanism in the narrow stripe lasers. The self-pulsation effect is enhanced by the self focusing and defocusing of the optical field which is dependent on the modification of carrier densities in the active region. The resulting AlGaInAs-InP device with compressively strained multi-QWs showed self-pulsation frequency of 3.5 GHz.

Solid State Communications, 1999

ABSTRACT The effects of spin–orbit split-off band on InGaAs/InP strained quantum wire structures ... more ABSTRACT The effects of spin–orbit split-off band on InGaAs/InP strained quantum wire structures are theoretically investigated using 6×6 Luttinger–Kohn Hamiltonian. The strong coupling of spin–orbit split-off band with other states has considerable effects on optical properties. It shows that the peak gains are underestimated for the unstrained and the tensile strained quantum wires in 4×4 Luttinger–Kohn model. The change of the density of states and the dipole moments are the main factors for the inconsistent results between the 4×4 and the 6×6 models in the linear optical gain. In the tensile and the unstrained quantum wire structures, the threshold carrier densities are reduced by spin–orbit coupling. The compressive strained structure has the lowest threshold carrier density and the highest differential gain. As a whole, the differential gain is improved by the spin–orbit coupling effects.

Optical and Quantum Electronics, 2004

The small-signal modulation characteristics of 1.5 lm lattice-matched InGaNAs/GaAs and InGaAs/InP... more The small-signal modulation characteristics of 1.5 lm lattice-matched InGaNAs/GaAs and InGaAs/InP quantum well lasers and their temperature dependence have been calculated. It is found that the maximum bandwidth of the InGaNAs/GaAs quantum well lasers is about 2.3 times larger than that of the InGaAs/InP quantum well lasers due to the high differential gain which results from the large electron effective mass in the dilute nitride system. The slope efficiency for the 3 dB bandwidth as a function of optical density is twice as large for InGaNAs/GaAs as for InGaAs/InP quantum well lasers.

Applied Physics Letters, 2003

The linewidth enhancement factors of lattice-matched 1.5 μm wavelength InGaNAs/GaAs and InGaAs/In... more The linewidth enhancement factors of lattice-matched 1.5 μm wavelength InGaNAs/GaAs and InGaAs/InP single-quantum-well structures are calculated using microscopic theory and effective-mass Hamiltonian. InGaNAs/GaAs quantum wells have a lower threshold carrier ...

Physical Review B, 2003

The 6ϫ6 effective mass Hamiltonian for semiconductor heterostructures grown on (11N)-oriented sub... more The 6ϫ6 effective mass Hamiltonian for semiconductor heterostructures grown on (11N)-oriented substrates is derived and is compared with the 4ϫ4 model. The hole subbands of InGaAs/InP single quantum wells grown on (11N)-oriented substrates with Nϭϱ ͑that is, ͑001͔͒, 0, 1 are calculated using the effective mass Hamiltonian as an example. The spin-orbit coupling affects the light-hole subband at k ͉͉ ϭ0, but it affects all subbands at finite k ͉͉ for all substrate orientations. In the 4ϫ4 model ͑without spin-orbit coupling͒, the coupling between the heavy hole and the light hole is overestimated. At a critical uniaxial stress, the position of the first heavy hole and the first light hole as the highest energy level cross over. The separation between the first heavy hole and the first light hole is overestimated at the uniaxial stress below the critical value and is underestimated above the critical stress in the 4ϫ4 model. The spin-orbit coupling greatly affects the valence band structures of the semiconductor heterostructures resulting in the modifications of the optical transitions anisotropy for structures grown on (11N)-oriented substrates.