Browsing by Author "Chern, JL"

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Chaos synchronization in a mutually coupled laser array subjected to self-mixing modulation
(2004-07-01)
Kawai, R
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Lih, JS
;
Ko, JY
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Chern, JL
;
Otsuka, K
This tutorial presents a detailed description of experiments, simulations, and characterizations of chaos synchronization phenomena in the model of a mutually coupled microchip solid-state laser array subjected to self-mixing feedback modulation. We demonstrate a transition to synchronized chaos by the method of 'phase squeezing' with increasing field overlap between the two lasers. This phenomenon is well reproduced by numerical simulation of model equations. It is also shown that low energy variation as well as high disorder are concurrently established in synchronized chaos in the present system. The deterministic random switching (i.e., chaotic itinerancy) among phase-squeezed states and synchronized chaos states is numerically demonstrated in a transition region from a phase-squeezed state to a synchronized state. We characterize observed behaviours; using such methods as singular value deposition (SVD), joint time-frequency analysis (JTFA) introducing a similarity function, and coarse-grained information transfer rate (CITR) analysis of long-term experimental or numerical time series, and discuss the physical significance of observed nonlinear dynamics in conjunction with chaos synchronization in mutually coupled lasers.
Characterization of the signature of subwavelength variation from far-field irradiance
(2004-05-15)
Chu, SC
;
Chern, JL
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光電工程學系
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Department of Photonics
The dynamic signature of the subwavelength variation of a slit is shown to be determinable from far-field irradiance with a precision of better than 1 nm. One can increase the efficiency of measurement of the subwavelength's signature by adjusting the detection width over which the subwavelength variation is detected. The subwavelength variation of a rectangular aperture was also examined to show the general feasibility. (C) 2004 Optical Society of America
Detection of subwavelength slit-width variation with measurements in the far field by use of an embedded-aperture interferometer configuration
(2005-02-01)
Chu, SC
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Chern, JL
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友訊交大聯合研發中心
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D Link NCTU Joint Res Ctr
The dynamic signature of the subwavelength variation of a rectangular aperture has recently been Shown to be determinable from far-field irradiance with a precision better than 1 nm [Opt. Lett. 29, 1045 (2004)]. We have proposed, and have theoretically shown, that detection sensitivity can be greatly enhanced with an embedded-aperture Mach-Zehnder interferometer configuration, after parameter optimization. The sensitivity, in terms of derivative intensity of observed subwavelength variations, could be enhanced approximately 2.7 times, compared with the directly detected method. Another method of detection of subwavelength variation from pattern measurement of far-field diffraction has also been proposed. The associated shifting of the dark line of the diffraction pattern had a good linear correlation to subwavelength variation, which was magnified approximately 150 times, and gave good contrast for measurement. (C) 2005 Optical Society of America.
Electromagnetic resonance in deformed split ring resonators of left-handed meta-materials
(2004-08-15)
Hsu, YJ
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Huang, YC
;
Lih, JS
;
Chern, JL
;
光電工程學系
Recently, structures called deformed split ring resonators have been proposed to achieve the smallest volume of a unit cell, while retaining negative permeability. With a combination of wire structures, the characteristics of a negative index of refraction, or left-handed meta-materials, can be seen from the transmission spectrum. This electromagnetic resonance, including its orientation tolerance and angular dependence on the incident beam, is explored in detail in the microwave range. (C) 2004 American Institute of Physics.
Evidence of birefringence and anomalous electromagnetic-pulse propagation in an organic light-emitting diode
(2005-06-05)
Tai, SC
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Chern, JL
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Huang, YC
;
Tseng, MR
;
Lin, HK
dHigh-speed electromagnetic characteristics of an organic light-emitting diode (OLED) are explored in this paper. When a high-frequency (similar to 14 GHz) microwave pulse is injected into an OLED, the pulse is split into two peaks: one peak is delayed by 1.725 ns and another one is advanced by 0.183 ns, which also suggests the existence of an extremely low-speed group velocity. The effective thickness of the OLED sample is similar to 355.8 nm and, as a result, the effective index of refraction is similar to 107 when the splitting phenomenon occurs. (c) 2005 Wiley Periodicals, Inc.
Experimental realization of breaking diffraction limit by planar negative-index metamaterials in free space
(2005-02-01)
Lih, JS
;
Wang, YS
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Lu, MC
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Huang, YC
;
Chen, KH
The sharpness of the image formed by a conventional lens is always limited by the wavelength of light. Recently, Pendry proposed a superlens, with a negative refractive index. such that the resolution is not limited by wavelength. Herein, we report direct experimental evidence of Pendry's superlens breaking the diffraction limit, in the microwave range of the X band (8-12 GHz), with a periodic array of split ring resonators and continuous wires; i.e. a meta-material with negative index of refraction.
Far-infrared resonance in split ping resonators
(2004-02-01)
Hsu, AC
;
Cheng, YK
;
Chen, KH
;
Chern, JL
;
Wu, SC
We experimentally investigated the resonance effect of planar metallic split ring resonators (SRRs) in the far-infrared region (FIR) (similar to10.6 mum). Experimental results indicated that they exhibit resonance around 10.6 mum, implying negative permeability in the FIR region. Furthermore, the ratio of effective dimensions of the SRR cell and the wavelength of the incident beam was around I which suggested a wide scale independence. This size tolerance is useful in realizing the meta-materials with negative indices of refraction in the optical wavelength domain.
Field propagation of a metallic grid slab that acts as a metamaterial
(2006-04-24)
Tsao, CH
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Chern, JL
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光電工程學系
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Department of Photonics
A metallic grid slab has been shown to work as a novel metamaterial which can shape the divergent field emitted from an embedded monopole microwave antenna into a directive transmission at a specific frequency. The transmission of such subwavelength slab remains an issue of challenge. In this work, we experimentally investigate the transmitted behavior of such subwavelength grid slab to explore the underlying mechanism of wave propagation. It is found that there is a large tolerance of directive emission even with a tilted slab. The deviation along the directive emission direction is analyzed based on the interference theory. (c) 2005 Elsevier B.V. All rights reserved.
Identifying the subwavelength-aperture-width variation in the far field with tunable asymmetrically-embedded-aperture interferometer configuration
(2005-08-01)
Chu, SC
;
Chern, JL
;
光電工程學系
;
Department of Photonics
A tunable asymmetrically-embedded-aperture interferometer configuration is proposed to enhance the measurement sensitivity of subwavelength variation. With this configuration, an aperture of reference was posited asymmetrically, relative to the test aperture, that exhibited subwavelength variation. By a shift in the relative position of the reference aperture, the detection sensitivity of measuring the subwavelength variation in the far field can be enhanced to a desired value at any specific detection width. We discuss the underlying mechanism of optimization and address the difference between the embedded-aperture interferometry and tunable asymmetrically-embedded-aperture interferometry with respect to tolerance. (C) 2005 Optical Society of America.
Irradiance formations in hollow straight light pipes with square and circular shapes
(2006-02-01)
Cheng, YK
;
Chern, JL
;
光電工程學系
;
Department of Photonics
We investigated, both analytically and numerically, the irradiance formation of an asymmetrically located Lambertian light source in hollow straight light pipes with square and circular shapes. The uniform irradiance distribution in a square light pipe and hot-spot localization in a circular light pipe were examined and determined semianalytically. Typical factors of influence, such as light-pipe length, width, and source size, were identified with extensive simulation. Mien the ratio of light-pipe length and width was less than 0.5, the deviation from uniformity could be more than 20%. But once the source size was large enough (approximately half of the incident port), such that the Lambertian characteristics of the source dominated the irradiance distribution, the uniformity deviation was reduced. Furthermore, a quantity of root-mean-square circular differences was defined in order to identify the shape deformation of the light pipe; it was found that the peak value of the hot spot decreased exponentially with the deformation scale. The influence of nonperfect reflectivity of the pipe wall on irradiance formation was also examined for a square light pipe; when the reflectivity is larger than 90%, the difference in uniformity is less than 10% and uniform irradiance remains, provided that the ratio of light-pipe length and width is larger than 1; even the source is located asymmetrically. (c) 2006 Optical Society of America.
New fabrication for DSRRs nanostructure in optics
(2006-01-01)
Chu, CS
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Tsai, RY
;
Lai, P
;
Chern, JL
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光電工程學系
The Deformed-Split-Ring Resonators (DSRRs) require metal nanostructure on high transmission material substrate for optical application. In this article, a simple method of fabricating three-dimensional polymer nanostructure that use an UV-curable polymer as the resist is discussed. Because UV cure imprinting has high resolution which is about 100nm and high transparency, it is ideally suited for photonic and meta-material optical device applications. The fabrication combines several mass production technologies. The first one is photolithography, such as a stepper UV exposure system can make the nano scale pattern in photoresist, the second is to change the photoresist sample to become the nanoimprint mould by precise electroforming, the third is to use UV cure imprinting to transfer the DSRRs pattern on the UV-curable polymer. Finally, it is also the most important process is that to coat metals and metal lift-off that coating Ag to become buffer layer by sputter, then coating Au into the nanostructure and lift off Ag by HNO3. The DSRR structure is implemented in high transmission UV-curable polymer with Au.
No-loss bent light pipe with an equiangular spiral
(2005-11-15)
Chu, SC
;
Chern, JL
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光電工程學系
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Department of Photonics
Bending a light pipe and maintaining the required volume and size, while at the same time preserving source energy and minimizing bend losses, is the basic criterion for designing a light pipe. An important requirement is the design of a light pipe that is capable of being bent without loss of light and with no limitations on acceptance angle. It is shown that in theory such a light pipe does exist, in a form corresponding to the so-called golden rectangle. Numerical simulations with six different no-loss light pipes with multiple bends are provided as a demonstration. (c) 2005 Optical Society of America
Phase-noise-driven instability in a single-mode microchip Nd : YVO4 laser with feedback
(2001-09-01)
Lim, TS
;
Yang, TH
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Chern, JL
;
Otsuka, K
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光電工程學系
We report the instability behaviors of a single-mode microchip solid-state laser subjected to external feedback. Two kinds of instabilities, random chaotic burst generations and random sinusoidal burst generations, were observed experimentally in an LD-pumped microchip Nd:YVO4 single-mode solid-state laser with fiber feedback. These results are totally different form those observed in laser diodes with delay feedback systems, which have been widely studied in last decades. Main features were reproduced numerically by utilizing the Lang-Kobayashi equations with phase noise, indicating phase-noise-driven dynamic instabilities.
Stokes-like emissions from laser-diode-pumped microchip neodymium-doped solid-state lasers
(2002-07-01)
Chern, JL
;
Kubota, T
;
Lim, TS
;
Otsuka, K
;
光電工程學系
Stokes-like IR (1560-1600-nm) emissions, which have been observed in laser-diode- (LD-) pumped microchip Nd-doped lasers, are re-examined experimentally. Dependences of IR emissions on pump wavelengths, pump densities, and operating temperatures are studied. The response of IR emissions to coherent probe-beam injection is investigated by use of a tunable LD light source. Optical phonons emitted through Auger recombination processes that result from LD high-density pumping are proposed to induce resonant intracavity stimulated phonon-sideband emissions. (C) 2002 Optical Society of America.
Transmission characteristics of deformed split-ring resonators
(2004-02-01)
Huang, YC
;
Hsu, Y
;
Lih, JS
;
Chern, JL
;
光電工程學系
A metallic-microstructure composite, which is comprised of deformed-split-ring resonators (DSRRs) and wires, is shown to preserve the transmission characteristics of a left-handed metamaterial, implying the simultaneously negative values of effective permeability and permittivity, as well as a wider bandwidth of resonance. Furthermore, the DSRR is so designed that it minimizes the size of the unit cell for fabrication, which is favorable for the implementation of left-handed metamaterial in near infrared region.
Transmission characteristics of smiling pattern resonators
(2004-05-15)
Hsu, YJ
;
Chern, JL
;
光電工程學系
;
Department of Photonics
We propose and experimentally verify a novel metallic-microstructure composite that consists of smiling-pattern resonators to broaden the bandwidth of resonance, in contrast to the well known narrow-band split ring resonators in the field of meta-materials and left-handed negative-index media. The underlying idea is to introduce multiple interaction scales to the resonator. Our microwave analog experiment shows that the range of resonant frequencies could also be extended apparently with double resonance bands. Furthermore, this smiling-Pattern resonator is superior in manufacturing for its simplicity in structure.