Browsing by Author "Lee, JY"

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A method for measuring Brewster's angle by circularly polarized heterodyne interferometry
(1998-12-01)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
A new method for determining Brewster's angle is proposed based on the effect that the phase difference produced by a simple reflection from the test medium, for a two-frequency circularly polarized light source, is exactly equal to zero when the incident angle equals Brewster's angle. Its best resolution is 10(-3) deg and the validity of the method was demonstrated.
A method for measuring Brewster's angle by circularly polarized heterodyne interferometry
(1998-12-01)
Lee, JY
;
Su, DC
;
光電工程研究所
;
Institute of EO Enginerring
A new method for determining Brewster's angle is proposed based on the effect that the phase difference produced by a simple reflection from the test medium, for a two-frequency circularly polarized light source, is exactly equal to zero when the incident angle equals Brewster's angle. Its best resolution is 10(-3) deg and the validity of the method was demonstrated.
A method for measuring the rotatory power of a chiral medium
(2001)
Su, DC
;
Hsu, CC
;
Lin, JY
;
Lee, JY
;
光電工程學系
A light beam coming from a circularly polarized heterodyne light source passes through a chiral medium, its rotation angle is just half of the phase difference between p- and s- polarization components. And this phase difference can be measured accurately with heterodyne interferometric technique. The rotatory power is obtained by dividing the estimated rotation angle with its path length. This method has many advantages, such as, high stability, high resolution, easy operation, and real-time measurement.
A similarity method for miniature mobile robots
(1998-03-01)
Liu, TS
;
Lee, JY
;
機械工程學系
;
Department of Mechanical Engineering
Taking advantage of a piezoelectric material to fabricate miniature mobile robots, this study presents a similarity method, fabrication process, and walking experiment method. A curved piezoelectric material is first analyzed for vibration behavior in order to provide a basis for deriving model laws. Since the behavior of miniature mobile robots is nor amenable to modeling, the similarity method is carried out to obtain model laws. A prototype for the miniature robot is further scaled down in different geometric sizes to conduct walking experiments. Experimental results that are primarily concerned with walking speeds comparison among robots of different sizes serve to verify model laws.
Activated kinetics of room-temperature-deposited SrTiO(3) thin films investigated by reflection-high-energy-electron-diffraction-monitored annealing at different heating rates
(2005-02-01)
Wang, TC
;
Lee, JY
;
Hsieh, CC
;
Juang, JY
;
Wu, KH
A series of reflection-high-energy-electron-diffraction-monitored annealings with different heating rates have been conducted on Strontium Titanate films deposited by laser ablation at room temperature. All the films exhibited a steep RHEED intensity rise above 660 degrees C during annealing with increasing temperature. The peak temperatures of the intensity derivatives were found to shift at different heating rates, suggesting an activated surface state transition. A Kissinger type plot of the peak temperatures showed an effective activation energy of 4 eV.
Activated kinetics of room-temperature-deposited SrTiO3 thin films investigated by reflection-high-energy-electron-diffraction-monitored annealing at different heating rates
(2005-02-01)
Wang, TC
;
Lee, JY
;
Hsieh, CC
;
Juang, JY
;
Wu, KH
A series of reflection-high-energy-electron-diffraction-monitored annealings with different heating rates have been conducted on Strontium Titanate films deposited by laser ablation at room temperature. All the films exhibited a steep RHEED intensity rise above 660 degrees C during annealing with increasing temperature. The peak temperatures of the intensity derivatives were found to shift at different heating rates, suggesting an activated surface state transition. A Kissinger type plot of the peak temperatures showed an effective activation energy of 4 eV.
An improved method for measuring refractive-index of a medium
(1998)
Su, DC
;
Lee, JY
;
光電工程學系
;
Department of Photonics
An improved method for measuring the refractive index of a medium is presented. First, the light coming from a circular heterodyne source is incident on the test medium. And, the reflected light passes through an analyzer with the transmission axis at a moderate azimuth angle. Then, the phase variation of the reflected light is measured by the heterodyne interferometric technique. Finally, substituting this phase variation into the equations derived from Fresnel's equations and Jones calculus, we can obtain the refractive index of the test medium.
Annealing characteristics of pulsed laser deposited homoepitaxial SrTiO3 thin films
(2001-08-10)
Lee, JY
;
Juang, JY
;
Wu, KH
;
Uen, TM
;
Gou, YS
The homoepitaxial growth of SrTiO3 (STO) films on as-polished STO(1 0 0) substrates by pulsed laser deposition has been exploited in detail. The intimate correlation between the surface step edge density and reflection high-energy electron diffraction (RHEED) intensity is clearly demonstrated by measuring the relation between the initial RHEED intensity drop and laser repetition rates. Systematic in situ annealing schemes were performed to investigate the film growth mechanisms. The results indicate that the two or three level growth May have occurred during some annealing schemes and can be interpreted by Stoyanov's step edge density model. Complementary atomic force microscopy investigations of the film surfaces further tend direct support to the RHEED intensity observations. (C) 2001 Elsevier Science B.V. All rights reserved.
Central fringe identification by phase quadrature interferometric technique and tunable laser-diode
(2001-11-01)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
When the optical path difference is not zero, the phase of the interferogram is strongly influenced by the wavelength variation of the light source. Under this condition, the phase variation can be estimated with a phase quadrature interferometric technique. And the central fringe of the interferogram can be identified as the, phase variation remains unchanged. Based on this fact, an improved method to identify the central fringe is presented. It has some merits, such as simple optical setup, easier operation in real time, inexpensive, ability to judge which arm of interferometer is longer, etc. The feasibility is demonstrated with 10 nm resolution. (C) 2001 Elsevier Science B.V. All rights reserved.
Central fringe identification using a heterodyne interferometric technique and a tunable laser-diode
(1996-07-15)
Lee, JY
;
Chiu, MH
;
Su, DC
;
光電工程研究所
;
Institute of EO Enginerring
A novel method combining a heterodyne technique and a tunable laser diode for identifying the central fringe of an interferogram is presented. It has some merits, such as simple optical structure, easier operation, etc. Its feasibility is demonstrated.
Central fringe identification using a heterodyne interferometric technique and a tunable laser-diode
(1996-07-15)
Lee, JY
;
Chiu, MH
;
Su, DC
;
交大名義發表
;
光電工程學系
A novel method combining a heterodyne technique and a tunable laser diode for identifying the central fringe of an interferogram is presented. It has some merits, such as simple optical structure, easier operation, etc. Its feasibility is demonstrated.
Common-path heterodyne interferometric detection scheme for measuring wavelength shift
(1999-04-01)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
When a linearly polarized light passes through a uniaxial crystal, small wavelength shifts will introduce phase difference variations between s- and p-polarizations, These phase difference variations can be measured accurately by heterodyne interferometry. Based on these facts, a common-path heterodyne interferometric detection scheme for measuring wavelength shift is proposed. This scheme has the advantages of both common-path interferometry and heterodyne interferometry. (C) 1999 Elsevier Science B.V. All rights reserved.
Complex refractive index measurements based on Fresnel's equations and the uses of a lock-in amplifier
(1999)
Su, DC
;
Chiu, MH
;
Lee, JY
;
光電工程學系
;
Department of Photonics
A new method for measuring complex refractive index is presented based on Fresnel's equations and the uses of a lock-in amplifier. A lock-in amplifier is introduced into a common path interferometer to measure the product of the amplitude reflection coefficients of s and p polarizations and their corresponding phase difference of a light beam reflected from a medium with complex refractive index. Then, these data are substituted into the special equations derived from Fresnel's equations, the complex refractive index can be obtained by numerical calculations. The resolution of this method is better than 0.01. It has both merits of a conventional common-path interferometer and a heterodyne interferometer. And its validity is demonstrated.
Complex refractive-index measurement based on Fresnel's equations and the uses of heterodyne interferometry
(1999-07-01)
Chiu, MH
;
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
The phase difference between s and p polarization of the light reflected from a material is used for measuring the material's complex refractive index. First, two phase differences that correspond to two different incidence angles are measured by heterodyne interferometry. Then these two phase differences are substituted into Fresnel's equations, and a set of simultaneous equations is obtained. Finally, the equations are solved by use of a personal computer by a numerical analysis technique, and the complex refractive index of the material can be estimated. (C) 1999 Optical Society of America.
Degradation of weak sandstone and continuum damage model
(1998)
Pan, YW
;
Lee, JY
;
土木工程學系
;
Department of Civil Engineering
The study experimentally simulates in-situ degradation mechanisms to investigate the degradation of weak sandstone. Following different artificial degradation processes, the specimens are subjected to uniaxial compression. From the experimental results, it is noted that degradation of the tested weak sandstone results in a marked reduction in strength and elastic modulus and an increase in the failure strain. On the basis of the experimental results, a constitutive model is proposed to describe the mechanical behavior of weak sandstone. The presented constitutive model-contains a hyperbolic pore/crack closure model and a continuum damage mechanics model. By comparing the simulated and experimental results, it is demonstrated that the proposed model can closely simulate the stress-strain relation of weak sandstone with very limited material parameters.
Effect of rapid thermal annealing on beryllium implanted p-type GaN
(2004-03-25)
Huang, HW
;
Kao, CC
;
Tsai, JY
;
Yu, CC
;
Chu, CF
We report the results of rapid thermal annealing (RTA) effect on beryllium implanted in situ activated p-type GaN samples and investigate the ramping and isothermal annealing effect of RTA process for these samples. It is found that the optimum RTA condition is at the temperature of 1100 degreesC for 15 s. Furthermore, with equal total isothermal time of 60 s, we compared the multiple step annealing (MSA) at 1100 degreesC for four periods with single step annealing (SSA) for one period at the same annealing temperature of 1100 degreesC, and observed that the ramping effect with MSA could repair Be-related complex defect, and one time, long period isothermal annealing effect with SSA seems to induce much more defect. It seems that the multiple step annealing is more effective and induce less defect than single step annealing for Be-implanted in situ activated p-type GaN samples. (C) 2004 Elsevier B.V. All rights reserved.
Growth kinetics of homoepitaxial strontium titanate films by interrupted pulsed laser deposition
(2001-08-01)
Lee, JY
;
Wang, TC
;
Chen, SF
;
Juang, JY
;
Lin, JY
The effects of the initial surface state on the evolution kinetics of the surface morphology of strontium titanate (STO) films was investigated by in-situ monitoring the intensity variations of reflection high-energy electron diffraction (RHEED). In order to create various surface states prior to subsequent depositions, we intentionally interrupted the pulsed laser deposition (PLD) at various points during the whole deposition course to perform in-situ annealing over various periods of time. The depth of the initial drop of RHEED intensity, which is a direct indication of changes in surface step densities, shows two distinct time scales. The results suggest that the evolution of a growing surface, and hence the ultimate film surface morphology, may be manipulated by controlling the number density of the as-deposited growing islands through interrupted annealing.
High resolution central fringe identification
(1998-11-01)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
A high resolution central fringe identification by using the heterodyne interferometry with a tunable laser-diode and a fixed wavelength laser is presented. It can be operated easily and can be used to judge which arm of the Michelson interferometer is longer. The feasibility is demonstrated and it has 0.2 nm resolution. (C) 1998 Elsevier Science B.V. All rights reserved.
Improved common-path optical heterodyne interferometer for measuring small optical rotation angle of chiral medium
(2005-12-15)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
An improved common-path optical heterodyne interferometry for measuring small optical rotation angle of chiral liquid is presented. The optical rotation angle can be determined by the phase difference between the test and reference signals. By means of inserting, a phase retarder behind the test sample, the measuring resolution of optical rotation angle is greatly enhanced. The theoretical prediction indicates the resolution is better than 3.5 x 10(-5) degree. (c) 2005 Elsevier B.V. All rights reserved.
Measurements of material refractive indices using heterodyne interferometry
(2000)
Su, DC
;
Lee, JY
;
Hsu, CC
;
Chiu, MH
;
光電工程學系
The phase difference between s- and p- polarizations of the reflected light from a test material is measured using heterodyne interferometry. The measured data is substituted into the specially derived equations and the refractive index can be calculated. When an absorbing material is tested, a general heterodyne light source is used and two measurement processes should be performed because of its two unknown parameters to be solved. And only one measurement process is performed with a circularly polarized heterodyne light source for testing a non-absorbing material. Because the phase difference can be measured accurately with heterodyne interferometry, its performance is not affected by surrounding light noise. So, it is very stable and has a high resolution.