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Stable and Tunable Single-Longitudinal-Mode Erbium-Doped Fiber Triple-Ring Laser With Power-Equalized Output
(2016-04-01)
Yeh, Chien-Hung
;
Chen, Jhih-Yu
;
Chen, Hone-Zhang
;
Chen, Jing-Heng
;
Chow, Chi-Wai
In this demonstration, we propose and investigate a stable and tunable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser structure. Here, in order to achieve the SLM output, the "eye-type" triple-ring scheme is designed in this EDF laser to suppress the densely spaced longitudinal modes. In the measurement, the output power and optical-signal-to-noise ratio (OSNR) are between 8.35 and 8.92 dBm and 33.2 and 35.7 dB, respectively, in the wavelength range of 1530 to 1560 nm. The proposed EDF laser architecture not only has free tuning step but provides stabilized and flattened output power spectrum as well.
Stable Single-Longitudinal-Mode Erbium Fiber Ring Laser Utilizing Self-Injection and Saturable Absorber
(2017-12-01)
Yeh, Chien-Hung
;
Huang, Tzu-Jung
;
Yang, Zi-Qing
;
Chow, Chi-Wai
;
Chen, Jing-Heng
In this work, we demonstrate a wavelength-tunable erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) output. Here using the self-injection method and unpumped EDF-based saturable absorber can suppress other densely side-mode to achieve SLM. Hence, the output power and optical signal-to-noise ratio of proposed EDF ring laser are between -7.1 and 2.1 dBm and 30.1 and 36.5 dB in the tuning range of 1525.0 to 1574.0 nm, respectively. According to the proposed EDF laser structure, the wavelength operation range can extend to shorter L-band from C-band. Moreover, the output stability of the proposed EDF ring laser is also executed experimentally.
Stress measurement of thin film on flexible substrate by using projection moire method and heterodyne interferometry
(2016-06-01)
Chen, Kun-Huang
;
Chen, Jing-Heng
;
Tseng, Hua-Ken
;
Chang, Wei-Yao
;
光電工程學系
We propose a stress measurement system based on a projection moire method and heterodyne interferometry for thin films on a flexible substrate. In the measurement setup, a CMOS camera in which every pixel can receive a series of heterodyne moire signals by using a continuously relative displacement with a constant velocity is used. Furthermore, the phase of the optimized sinusoidal curve and the surface profile of the flexible substrate are determined using a least-squares sine fitting algorithm. The thin-film stress is obtained by representing the cross-sectional curve of the surface profile by using a polynomial fitting method, estimating the resultant curvature radii of the uncoated and coated substrates, and using these two radii in the corrected Stoney formula. The proposed measurement system has the advantages of high accuracy, high resolution, and high capacity for substrates with high flexibility and a large measurement depth. (C) The Authors.
Generating Radially and Azimuthally Polarized Beams by Using a Pair of Lateral Displacement Beamsplitters
(2016-09-01)
Han, Chien-Yuan
;
Wei, Zhi-Hao
;
Hsu, Yung
;
Chen, Kun-Huang
;
Yeh, Chien-Hung
This paper proposes a modified polarization converter for generating radially and azimuthally polarized beams. Based on a Mach-Zehnder-like interferometric structure, the device consists of a pair of lateral displacement beamsplitters (LDBs) and two half-wave plates that manipulate the states of polarization of incident linearly polarized light. Through the coherent superposition of two orthogonal Hermite-Gaussian modes in the far field, radially and azimuthally polarized beams can be obtained simultaneously. A prototype was assembled to demonstrate the feasibility of the design. The proposed design has the advantage of having a simple, symmetric, compact, and robust structure. In addition, the introduction of LDBs substantially reduces the cost of this device. Moreover, the design can be applied to a broadband pulsed laser with considerable potential in high-power applications.
Stable and Wavelength-Tunable Self-Injected Reflective Semiconductor Optical Amplifier-Based Fiber Laser
(2015-08-01)
Wu, Yu-Fu
;
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Sung, Jiun-Yu
;
Chen, Jing-Heng
In this investigation, we propose and demonstrate a stable and wavelength-tunable self-injected reflective semiconductor optical amplifier (RSOA)-based laser by using the Faraday rotator mirror (FRM) and the fiber mirror (FM) serving as a reflected element, respectively. Here, a 1.2-GHz RSOA can be enhanced to similar to 3 GHz by utilizing a self-injected mechanism. In the measurement, applying the optical orthogonal frequency-division multiplexing quadrature amplitude modulation (OFDM-QAM) with a bit-loading algorithm on the self-injected RSOA directly, the proposed laser can achieve a 3.5-Gb/s data rate in a 20-km single-mode-fiber transmission below a forward error correction (FEC) threshold. Moreover, the related output performance of the proposed RSOA-based laser is also discussed, whereas the FRM and the FM are utilized for comparisons.
Collimation testing and calibration using a heterodyne Moire method
(2014-11-01)
Chang, Wei-Yao
;
Hsu, Ken Y.
;
Chen, Kun-Huang
;
Chen, Jing-Heng
;
光電工程學系
This study proposes a simple, rapid, and highly accurate method to achieve the collimation testing and calibration of laser light beams. By applying a relative constant velocity to two gratings, every pixel of a CMOS camera can receive a series of heterodyne moire signals. Based on the least squares sine fitting algorithm, the phase of the optimized sinusoidal wave can be obtained. Consequently, the phase slope along the direction perpendicular to the grating lines can be estimated and then used to judge the degree of collimation. Furthermore, by measuring only two phase slopes at two positions of the collimating lens, the calibration of the light beam collimation can also be achieved. The experiment validated the proposed method, and the positioning error of the light beam collimation was approximately 7 mu m. (C) 2014 Elsevier Ltd. All rights reserved.
Full-field refractive index measurement with simultaneous phase-shift interferometry
(2014)
Chu, Yen-Chang
;
Chang, Wei-Yao
;
Chen, Kun-Huang
;
Chen, Jing-Heng
;
Tsai, Bo-Chung
Using the phenomenon of total internal reflection and a beam splitting device, a technique of simultaneous phase-shift interferometry is proposed for measuring the full-field refractive index. Because this method applies a beam splitting device that mimics the characteristics of beam splitting and phase modulation, four interferemetric images of various phase distributions can be simultaneously captured. Therefore, this setup can avoid errors caused by non-simultaneous capturing of images and offers the benefits of high stability, ease of operation, and real-time measurement. Furthermore, using the phenomenon of total internal reflection, the phase difference between p- and s-polarized light varies considerably with the refractive index of a tested specimen. This can substantially increase the measurement resolution. The feasibility of this method is verified using an experiment, and the measurement resolution can be higher than 3.65 x 10(-4) RIU. (C) 2014 Elsevier GmbH. All rights reserved.
Optimized design of multiport optical circulator
(2014)
Hsu, Fan-Hsi
;
Chen, Jing-Heng
;
Chen, Kun-Huang
;
Yeh, Chien-Hung
;
Hsu, Ken Y.
This research proposes a practical multiport optical circulator design by using polarizing beam splitter cubes as spatial walk-off polarizers. The use of Porro prisms for directing light requires fewer components and improves space-efficiency. Therefore, a high performance device can be produced at a reduced cost. A six-port optical circulator prototype was fabricated to show the feasibility of the proposed design. The insertion losses range between 0.52 and 1.05 dB, the isolations range between 26.20 and 45.13 dB, and the return losses are 27.72 dB. The benefits of this design\'s simple and symmetrical structure include costefficiency, simple fabrication processes, polarization-independence, the resolve of polarization-mode dispersion issues, and high performance. Additionally, the number of ports can be increased easily. (c) 2014 Elsevier GmbH. All rights reserved.
Stable and wavelength-tunable RSOA- and SOA-based fiber ring laser
(2014-06-01)
Yeh, Chien-Hung
;
Sung, Jiun-Yu
;
Yang, Ling-Gang
;
Chow, Chi-Wai
;
Chen, Jing-Heng
In this work, we propose and experimentally investigate a wavelength-tunable fiber ring laser architecture by using the reflective semiconductor optical amplifier (RSOA) and semiconductor optical amplifier (SOA). Here, the wavelength tuning range from 1538.03 to 1561.91 nm can be obtained. The measured output power and optical signal to noise ratio (OSNRs) of the proposed fiber laser are between -0.8 and -2.5 dBm and 59.1 and 61.0 dB/0.06 nm, respectively. The power and wavelength stabilities of the proposed laser are also studied. In addition, the proposed laser can be directly modulated at 2.5 Gbit/s quadrature phase shift keying-orthogonal frequency-division multiplexing (QPSK-OFDM) signal and 20-50 km single-mode fiber (SMF) transmissions are achieved within the forward error correction (FEC) limit without dispersion compensation. It could be a cost-effective and promising candidate for the standard-reach and extended-reach wavelength division multiplexed passive optical network (WDM-PON). (C) 2014 Elsevier Inc. All rights reserved.
Corneal surface reconstruction by using heterodyne moire method
(2013)
Chang, Wei-Yao
;
Chen, Kun-Huang
;
Chen, Der-Chin
;
Tseng, Jung-Kai
;
Chen, Shyan-Tarng
In this paper, we propose a simple method for reconstructing the corneal surface profile by using the Talbot effect, projection moire method, and heterodyne interferometry. A linear grating is obliquely illuminated by an expanding collimated light, and a self-image of this grating can be generated and projected on the corneal surface. The deformed grating fringes are imaged on the second grating to form the moire fringes. If the first grating is moved with a constant velocity along the grating plane, a series of sampling points of the sinusoidal wave which behave like the heterodyne interferometric signal can be recorded by a CMOS camera. The phase distribution of the corneal surface then can be obtained with the IEEE 1241 least-square sine fitting algorithm and 2D phase unwrapping. Finally, the corneal surface profile can be reconstructed by substituting the phase distribution into special derived equation. This method provides the advantages of a simple optical setup, ease of operation, high stability, and high resolution.

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