Yuzo Hirayama

Five-wavelength integrated DFB laser arrays with quarter-wave-shifted structures

Five-wavelength integrated DFB laser arrays with quarter-wave-shifted structures, using nonuniform stripe width, have been developed for high-density WDM systems around the 1.3 μm wavelength region for the first time. Each DFB laser of the five-wavelength integrated DFB laser array oscillated at the Bragg wavelength with a side mode suppression ratio of more than 30 dB. Good reproducibility of 50 ± 5 A lasing wavelength separations has been obtained.

30.3: Autostereoscopic Partial 2-D/3-D Switchable Display Using Liquid-Crystal Gradient Index Lens

We developed 12-inch 9-view autostereoscopic partial 2-D/3-D switchable display using liquid crystal gradient index (GRIN) lens. We simulated optically by the stacked refraction-index distribution model and optimized liquid crystal (LC) material and electrode structure. The prototype achieved wide viewing angle and good 3-D image quality with mosaic color filter and vertical lens.

53.3: Distortion Control in a One-Dimensional Integral Imaging Autostereoscopic Display System with Parallel Optical Beam Groups

We have developed a one-dimensional integral imaging auto-stereoscopic display system consisting of an FPD and a lenticular plate that creates parallel optical beam groups. The reproduced 3-D images are free of distortion and show smooth motion parallax. We describe the methods employed for projection, elemental image alignment, and distortion control.

Feasibility of 1.55 μm Intersubband Photonic Devices Using InGaAs/AlAs Pseudomorphic Quantum Well Structures

We propose to use 1.55 µm intersubband transitions as a key mechanism for novel photonic devices such as fast photonic switches which are applicable to current optical communication systems. The calculation of carrier relaxation times shows a few picosecond switching time for 1.55 µm intersubband transitions. The well-width dependence of intersubband transition energies in InGaAs/AlAs pseudomorphic quantum well structures has been studied to realize 1.55 µm intersubband transitions.

Novel viewing zone control method for computer-generated integral 3-D imaging

We propose a novel algorithm to maximize the viewing zone of integral 3-D imaging (II) display. In our algorithm, the elemental image array consists of two kinds of elemental images whose numbers of sub-pixels are N and (N+1). The pitch of exit pupils was set to be N times the width of the sub-pixel and an average width of elemental images was designed to exceed the pitch of the exit pupils to a small extent by distributing the elemental images consisting of (N+1) sub-pixels. Under this condition, all light rays generated from elemental images can be introduced to the viewing zone width (viewing width) on the viewing line at the distance L without converging points of light rays at around L. This algorithm was applied to one-dimensional II system with 32 parallax light rays using a 20.8”-QUXGA-LCD (192 ppi) equipped with a lenticular sheet. Then, the viewing width at 1.5 m was expanded to 500 mm, a value almost five times larger than the width of a conventional display system. Even if hardware configurations are fixed, our algorithm enables a viewing zone to be the maximum at a certain L.

Simultaneous CW Operation of 5-Wavelength Integrated GaInAsP/InP DFB Laser Array with 50 Å Lasing Wavelength Separation

The simultaneous CW operation of a 5-wavelength integrated GaInAsP/InP DFB laser array has been realized. The average lasing wavelength separation was 49 A, which was in very good agreement with the designed value. Threshold currents were 57 to 75 mA and differential quantum efficiencies were 11 to 21%. A simultaneous CW operation was obtained at up to 40°C with each stable single longitudinal mode. It was found that the threshold current was almost independent of wavelength within a range of 500 A on the long wavelength side of the spontaneous emission peak and could be reduced to as little as 20 mA by fabricating deep, uniform gratings and by increasing the crystal homogeneity of the wafer.

Autostereoscopic liquid crystal display using mosaic color pixel arrangement

We have developed some prototypes of a one-dimensional integral imaging (1-D II) autostereoscopic display. Generally, II is one of the most promising methods for realizing an autostereoscopic display. However, a lens or barrier pitch is wide and obtrusive because this method requires many parallaxes. In this case, slanting lens or barrier is undesirable because the pattern is asymmetrical. From the result of examination about the display resolution of the autostereoscopic display, we adopted an LCD with mosaic color filter arrangement and a vertical lenticular sheet. We changed the color filter to the mosaic arrangement for two types of LCD. One was an LCD of 20.8-inch diagonal size with QUXGA resolution (3200 x 2400 pixels) and another was an LCD of 15.4-inch diagonal size with WUXGA resolution (1920 x 1200 pixels). The typical specifications of the prototypes of the autostereoscopic display were 32 parallaxes with 300 horizontal resolution for the 20.8-inch size and 18 parallaxes with the same resolution for the 15.4-inch size. We confirmed these prototypes showed good appearance and stereoscopic display properties due to the symmetrical lens pattern.

Comparison of effective /spl alpha/ parameters for multiquantum-well electroabsorption modulators

A new effective /spl alpha/ parameter appropriate for evaluating the transmission performance of multiquantum-well electroabsorption (MQW-EA) modulators is proposed. It is defined by the ratio of the phase change to the loss change between the ON voltage and the voltage at which the exciton peak reaches the wavelength of the light source. Simulation reveals that along various effective /spl alpha/ parameters it has the best correlation with the equivalent /spl alpha/ parameter obtained from the transmission performance.<<ETX>>

High-speed 1.5- mu m compressively strained multi-quantum well self-aligned constricted mesa DFB lasers

A great improvement in the high-speed characteristics for compressively strained multi-quantum-well (MQW) distributed-feedback (DFB) lasers with self-aligned constricted mesa structures is described. Negative wavelength detuning is an important factor in making possible the extraction of potential advantages for the compressively strained MQW DFB lasers. A 17-GHz bandwidth, which is the highest among the 1.5- mu m MQW DFB lasers, is demonstrated. A wavelength chirp width of 0.42 nm at 10 Gb/s is obtained due to a reduced linewidth enhancement factor that has a magnitude of less than 2. Nonlinear damping K factor in a DFB laser with 45-nm negative detuning has drastically decreased to 0.13 ns, about half of that for unstrained MQW lasers. This is mainly due to an enhanced differential gain as large as 6.9*10/sup -12/ m/sup 3//s. The estimated intrinsic maximum bandwidth is 68 GHz. >

Effect of light ray overlap between neighboring parallax images in autostereoscopic 3D displays

A display system with lens arrays at the front of a high-resolution LCD has been known as a method to realize an autostereoscopic three-dimensional (3D) display. In these displays, a light ray overlap between neighboring parallax images affects the image quality. In this study, the overlap effects were investigated for the one-dimensional (horizontal parallax only) integral imaging (1D-II) method. We fabricated samples of 1D-II displays with different levels of light ray overlaps and evaluated the 3D image by subjective assessment. It is found that the 1D-II display utilizing the proper parallax overlaps can eliminate banding artifact and have good 3D image quality within the wide range of a viewing area.