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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Design and Fabrication of Asymmetric Mach-Zehnder Interferometer and Ring Cavity Filter

Li, Kuan-Jui 10 July 2006 (has links)
The goal of the thesis is to fabricate the integrated asymmetric Mach-Zehnder Interferometer and Optical waveguide Ring Resonator with simple fabrication process. A 1.49£gm symmetric quantum well InGaAlAs epitaxial wafer is used to fabricate the devices. In the asymmetric Mach-Zehnder Interferometer design, we design asymmetric straight waveguides with difference of optical path, and asymmetric bend waveguides with difference of curvature radius. By this design, we can observe the interference variation of output light by difference of optical path. Using these properties, it will get the index change caused by electric field and the loss of bend waveguide. In optical waveguide ring resonator design, we improve the problem of the length of original K=0.15 Multi-Mode Interference (MMI) by stepped-width waveguide. And we obtain different transmission spectrum by adjusting the splitting ratio of MMI couplers (K=0.85, 0.5, and 0.15) and cascading doudle rings. We apply K0=0.5, K1=0.15 and K2=0.5 MMIs to design and fabricate optical filters with square transmission spectrum. In fabrication process, we get smooth sidewall and highly perpendicularity waveguide by multi-step wet etch method. In order to reduce waveguide loss, we make deep etching for the outside of curve waveguide and MMI. Finally, we use polyimide to smooth out the sides of the ridge waveguides and evaporate metal pad over the polyimide.
2

Design and Fabrication of Straight and Curve Optical Waveguides and Ring Cavity Wavelength Filter

Lin, Cheng-Nan 30 July 2007 (has links)
The goal of the thesis is to fabricate the integrated asymmetric Mach-Zehnder Interferometer and optical waveguide ring resonator with simple fabrication process. 1.41£gm and 1.49£gm symmetric quantum well InGaAlAs epitaxial wafer is used to fabricate the devices. In the asymmetric Mach-Zehnder Interferometer , we design asymmetric straight waveguides with difference optical path differences £GL=480£gm, 970£gm, and 1900£gm. And asymmetric bend waveguides with curvature radius differences £GR=260£gm, 200£gm, 160£gm, and 100£gm. By this design, we can observe the interference variation of output light. In optical waveguide ring resonator design, we reduce the length of original K=0.15 Multi-Mode Interference (MMI) by stepped-width waveguide. By three-stepped width waveguide MMI design, it can be reduced 33.2% length. We obtain different transmission spectrum by adjusting the splitting ratio of MMI couplers (K=0.85, 0.5, and 0.15) and cascading doudle rings. We use a series of two ring resonators by MMI (K0=0.5,K1=0.15,K2=0.5) to get the FSR=50GHz. In fabrication process, we combined dry etching method with RIE-ICP and wet etching to get smooth sidewall and highly vertical waveguide. In measure , we get the FSR= 41.25 GHZ in throughput port in double ring filters . No signal in drop port was obserred due to material absorption, bending loss, and waveguide loss.
3

Study of Electro-Optic Coefficient of Poled Guest/Host Nonlinear Optical Polymer Thin Film

Chen, Cheng-Hsiang 28 July 2004 (has links)
In this study, we focus on the electric optical characteristic of guest/host polymer system. The charge transfer chromophore Wu182 which contain fluorine atom in it was mixed with polymer PMMA and solved in chloroform, while DR1/PMMA served as reference sample. The wu182/PMMA and DR1/PMMA thin films were produced by spin coating. The thin film was poled at the temperature above glass transition temperature until the second harmonic generation signal was present. The poled thin film was placed in one arm of Mach-Zehnder interferometer. Voltage modulation applied to the polymer films can cause phase changes in the interferometer from that we estimate the electro-optic coefficient. From our experiments, we found that modulating frequency had significant influence on the electro-optic effect. The result shows that Wu182 possess large nonlinear optical coefficient. The valid electro-optic coefficient r13 was obtained to be 2.620 pm/V when the frequency was above 6 kHz.
4

The Configuration Analysis of Interferometric Hydrophones

Wu, Tzu-wei 04 September 2004 (has links)
The interferometeric optical fiber sensor has high sensitivity for sound signal. This characteristic is used to design hydrophones. The sound pressure causes the optical fiber to change its shape. So as to induce phase difference between sensing and reference arms. Using the demodulation system, we can get the signal we want. In this thesis, we plan to analyze three different kinds of optic configurations, such as Michelson, compensating Mach-Zehnder, hybrid configuration of Mach-Zehnder and Sagnac interferometers. The mathematical methods are used to compare their characters. We also use software to simulate the relation among sensitivity, delay fiber and frequency character of the Sagnac interferometer. In our experiment, we use PGC modulation technology and compare the results with a standard hydrophone B&K 8103 for calibration. We also measure the dynamic range of proposed three interferometers. The measurement result of this paper is as following: Michelson and compensating type Mach-Zehnder interferometer dynamic range were about 24.90 dB and 13.98 dB, the acoustic signal sensitivity was -201.67 dB re V/1uPa and -205.97 dB re V/Pa, respectively. The dynamic range of the hybrid of Mach-Zehnder and Sagnac type interferometer was 33.67 dB and acoustic signal sensitivity was -212.47 dB re V/1uPa.
5

A study of Asymmetric Mach-Zehnder Interferometer and Optical waveguide Ring Resonator

Tsai, Cheng-ju 21 July 2005 (has links)
The goal of the thesis is to fabricate the integrated asymmetric Mach-Zehnder Interferometer and Optical waveguide Ring Resonator with simple fabrication process. A 1.49
6

The Designs of Logic Gates and Drop Filter Based on Photonic Crystals

Sun, Yu-Hsuan 03 July 2007 (has links)
Due to the property of the photonic crystal, like bandgap, many researches on them are discussed. Photons with wavelength within the bandgap cannot propagate through the crystal. Then placing some defects in the crystal, because the periodic arrangement is destroyed, it is possible to build a waveguide to guide light along certain path. One kind is coupled cavity waveguide. The photons can propagate in a coupled-cavity waveguide by coupling without radiation losses. So it is widely used to implement a variety of optical devices. In this thesis, we use coupled cavity waveguide to construct devices. And the characteristics of Mach-Zehnder interferometer and power splitter are discussed. Then we propose two logic gate structures with an input port and two control ports. The state of control port determines the electric field at the output port. Besides, the four-port channel drop filter is proposed. It will make the three wavelengths ¢w1310, 1490 and 1550 nm¢w propagate in different waveguides. So it could be used as a wavelength demultiplexer for FTTH. Finally, the property of the PC-based rat-race circuit is investigated. By adjusting the phase of the control signal, we could decide the input signal to exit from output 1 or output 2. In this way, we could use it to function as a switch.
7

The Design of Fiber Bragg Grating Vibration Sensors

Chen, Chien-Cheng 14 July 2003 (has links)
The reflection wavelength of Fiber Bragg Grating is sensitive to the strain and the temperature¡¦s variation. We use Fiber Bragg Grating to be the sensor head and measure the vibration frequency in constant temperature environment. The vibration of object can make the sinusoidal strain to Fiber Bragg Grating, and it will make a little phase difference to the light of the fiber. Using the interferometer and demodulation system, we can measure the phase difference and vibration frequency. Our sensor configuration is made up of imbalance Mach-Zehnder interferometer and Fiber Bragg Grating. The two light of different path need different time to pass through the vibration source, so they make phase difference. We use the demodulation circuit to measure the phase difference causing by vibration and get the vibration frequency. Our experiment structure is a novel configuration of Fiber Bragg Grating vibration sensor. Its intensity of signal is larger than the intensity of original sensor configuration, about 4dB.The novel sensor configuration is easier spread than traditional accelerometer and it is designed of all fiber. The accuracy for measuring low frequency vibration is 99.971%. The Dynamic range of the system is more than 45dB. It is larger than the dynamic range of original sensor configuration, about 9dB. The smallest signal that can be measured is about 0.0075rad.
8

The Design of the Interferometric Fiber¡VOptic Microphone with FBG

LU, CHIEN-LI 17 July 2003 (has links)
Abstract The electrical microphone has came to maturity, which has some restrictions on high electromagnetic and wet environments¡CFiber-Optic sensor can improve the problems, because it has better characters in electromagnetic interference and wet environment than the traditional microphone. The structure of Sagnac interferometer is circulator, so the design of head to a sensor has to wind fiber around. Because the minimum radius of winded fiber has a threshold, we can not miniaturize the sensor-head. A typical Mach-Zehnder interferometer has to use high-coherence light source and the length of two arms in equality without any interference, so it is difficult in fabrication. If we make a microphone by FBG and Mach-Zehnder interferometer, and the advantage is that we can use low-coherence light source, and shorten the length of two arms in interferometer. By using the structure, the minimum measured pressure of sound is 0.6 Pa, and the dynamic range is 30dB.
9

Characterization of Bio-sensing Waveguides in CYTOP Operating with Long Range Surface Plasmon Polaritons (LRSPP’s)

Khan, Asad 14 May 2013 (has links)
This thesis report works on optically characterizing waveguide based biosensors consisting of thin, narrow Au stripes embedded in CYTOP. The devices were examined using an ever evolving and improving interrogation setup, variations of which are described in detail in this document. A number of changes were made to the setup configuration in order to reduce noise levels and increase efficiency and accuracy of acquired measurements. Waveguides of varying configurations (straight waveguides and Mach-Zehnder Interferometers with etched and cladded channels) are described and optically characterized. The characterization results of these devices are presented in this thesis. Bulk index measurements are carried out in order to determine a suitable bio-sensing solution with a refractive index matched to that of CYTOP. Step index measurements clearly distinguishing the introduction of sensing solutions of refractive indices varying from one another, are made available. Preliminary bio-sensing experiments involving detection of change in refractive index of sensing fluid as well as adlayer thickness with the introduction of analytes binding to the waveguide surface that has been functionalized with antibodies, using both straight and cladded waveguides with single mode outputs are studied.
10

Multi-Parameter Sensing Based On In-Line Mach-Zehnder Interferometer

Xu, Yanping 04 September 2013 (has links)
Optical fiber sensors have been intensively studied and successfully employed in various human social activities and daily living, such as industrial production, civil engineering, medicine, transportation, national defense and so on. According to different structures, optical sensors could be divided into various categories. This thesis focuses on studying different kinds of in-line fiber Mach-Zehnder interferometers, which have played an important role among the optical interferometric fiber sensors. The structure composition, fabrication process, physical principle and practical applications of two novel in-line fiber Mach-Zehnder interferometers are proposed and discussed in detail in this work. The tapered bend-insensitive fiber Mach-Zehnder interferometer (BIF-MZI) is firstly fabricated and used as a fiber vibrometer. The unique double-cladding structure of bend-insensitive fiber not only provides higher mechanical strength to the sensor, but also guarantees a more uniform transmission spectrum, since only a few inner-cladding modes are left interfering with the core mode. A high sensitivity and fast response intensity demodulation scheme is employed by monitoring the power fluctuation of the BIF-MZI at the operation wavelength. Both damped and continuous vibrations are detected using the proposed sensor. It is demonstrated that this sensor responses to an extremely wide range of frequencies from 1 Hz up to 500 kHz with high signal-to-noise ratios (SNRs). The discrimination of temperature and axial strain is realized based on the dispersion effects of high-order-mode fiber (HOMF) by forming a single mode fiber-high-order-mode fiber-single mode fiber (SMF-HOMF-SMF) structure based in-line Mach-Zehnder interferometer. Unlike some kinds of in-line MZIs such as tapered and core–offset structures whose cladding modes are excited with different types under changing temperature and strain circumstances, the HOMF is capable of supporting three stable core modes, which guarantees a reliable and repeatable measurements within a large temperature or strain range. A new method based on the fast Fourier transform (FFT) is employed to analyze the mode couplings and their chromatic dispersion and intermodal dispersion properties in HOMF. The strong dispersion effects lead to a multi-peak feature in the spatial frequency spectrum. It is found that peaks that denote the waveform periods at positions that are beyond the critical wavelength possess highly sensitive and distinct phase responses to external disturbances, which provides the possibility to realize the discrimination measurements with high sensitivities and smaller errors by selecting appropriate peaks. The phase demodulation scheme is applied to quantify the temperature and strain changes in terms of phase shifts. Appropriate peak selections according to the practical needs would provide an easy access for applications where more than two parameters are required to be discriminated.

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