Browsing by Author "Lu, YT"

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An efficient link polling policy by pattern matching for bluetooth piconets
(2004-03-01)
Lin, TY
;
Tseng, YC
;
Lu, YT
;
資訊工程學系
;
Department of Computer Science
Bluetooth has a master-slave configuration called a piconet. Unspecified in the Bluetooth standard, the link polling policy adopted by a master may significantly influence the bandwidth utilization of a piconet. Several works have been dedicated to this issue. However, none of them addresses the asymmetry of traffics between masters and slaves, and the different data packet types provided by Bluetooth are not fully exploited. In this paper, we propose an efficient pattern matching polling (PMP) policy for data link scheduling that properly resolves these deficiencies. A polling pattern is a sequence of Bluetooth packets of different type combinations (e.g. DH1/DH3/DH5/DM1/DM3/DM5) to be exchanged by a master-slave pair that can properly reflect the traffic ratio (i.e. asymmetry) of the pair. By judiciously selecting a proper polling pattern together with polling times for the link, the precious wireless bandwidth can be better utilized. The ultimate goal is to reduce the unfilled, or even null, payloads in each busy slot. In addition, an overflow mechanism is included to handle unpredictable traffic dynamics. Extensive simulations are presented to justify the capability of PMP in handling regular as well as bursty traffics.
Compact, reliable asymmetric optical configuration for cost-effective fabrication of multiplex dot matrix hologram in anti-counterfeiting applications
(2003)
Lu, YT
;
Chi, S
;
光電工程學系
;
Department of Photonics
This study presents a compact optical configuration that can generate a multiplex dot-matrix hologram with complex interlaced images for anti-counterfeiting applications on valuable paper. Varying the orientation of the interference plane can enable the multiplex hologram to be recorded without changing the interference angle of two laser beams. With its simple asymmetric optical setup, a multiplex hologram with many interlaced images can be efficiently fabricated, increasing the cost of imitation. Experimental details of the asymmetric optical setup are also described.
Cost-effective fabrication of a phase mask by direct etching of the laser-interference grating on fused silica substrate
(2003-09-05)
Lu, YT
;
Chen, YH
;
Chi, S
;
光電工程學系
;
Department of Photonics
A simple and cost-effective method to manufacture a phase mask with high diffraction efficiency for deep UV application is proposed. The deep rectangular grating fabricated by using laser interference is etched directly into a fused silica substrate, instead of the dielectric coating on a substrate (done in a previous method). Using the metal layer on a dielectric layer for masking in the deep, dry etching process is also unnecessary in our technique. A fabricated rectangular grating with high diffraction efficiency is presented in this paper. We also demonstrate the fabrication processes and show the optimum parameters for our proposed technology. (C) 2003 Wiley Periodicals, Inc.
Effects of polarization on electroreflectance spectroscopy of surface-intrinsic n(+)-type doped GaAs
(2002-01-01)
Sung, YG
;
Chiou, SJ
;
Wang, DP
;
Lu, YT
;
Huang, KF
The electroreflectance (ER) spectra of a surface-intrinsic n(+)-type doped (100) GaAs have been measured at various polarization angles of the probe beam. Several Franz-Keldysh oscillations were observed above the band-gap energy, thus enabling heavy- and light-hole transitions to be separated by the application of the fast Fourier transform to the ER spectra. From this, the ratios of the amplitudes of the light- to heavy-hole transitions versus angle of polarization were obtained. At a large incident angle (80 degrees), the strength of the field of the probe beam in the normal direction of the sample (F(z)) was varied from zero to a larger component. It was found that the ratios increased with increasing F(z) which is consistent with the theory that the light-hole transition becomes more enhanced with z-polarized light. (C) 2002 American Institute of Physics.
Fabrication of a deep polyimide waveguide grating for wavelength selection
(2003-02-01)
Lu, YT
;
Yang, ZL
;
Chi, S
;
光電工程學系
;
Department of Photonics
A deep polyimide waveguide grating with transmission of -21 dB is demonstrated. A simple lithography process is used to fabricate the raised waveguide, including a deeply corrugated holographic grating. To accurately control the grating period, a rotatable optical setup is used to adjust the interference angle for the holographic process. The corrugation fabricated holographically is 80 nm much deeper than that written directly by an electron beam. The waveguide is thus a promising low-cost wavelength selective device that can be applied to metro networks. The design principles of the optimum mode-matching condition and the efficient transmission for such a deep waveguide grating are also discussed in this paper. (C) 2002 Elsevier Science B.V. All rights reserved.
Fabrication of light-shaping diffusion screens
(2002-12-15)
Lu, YT
;
Chi, S
;
光電工程學系
;
Department of Photonics
This study presents the fabrication of alight-shaping diffuser, made by recording the far field laser speckles projected from a ground glass on photoresist plate. Elliptical speckles are created by illuminating the ground glass with a line shape He-Cd laser beam. The recorded elliptical speckles can diffuse incident light into different spread angles in vertical and horizontal directions. The speckles are inscribed with the appropriate density and depth on the surface, to diffuse incident light uniformly without a hot spot, by controlling the separation and duration of exposures. A nickel master is then electro-formed from the speckled plate for embossing the pattern on plastic plate for mass production. The diffuser is used in front and rear projection screens with high gain, the displays of ATMs, LED display illumination shapers, LCD backlight and laser beam shaping homogenizers as well as other applications. (C) 2002 Elsevier Science B.V. All rights reserved.