Distributed feedback laser thesis

Distributed feedback laser thesis

In this thesis, distributed reflector (DR) lasers, consisting of a DFB (distributed feedback) laser with high reflection DBR (distributed Bragg reflectors) on one end, is studied by considering wire-like active regions for the DFB section The results of an investigation of the distributed feedback laser (DFL) as a source for short optical pulses is reported in this thesis. The DFL provides a uniquely simple and inexpensive alternative to synchronously pumped dye blogger.com: Irl N. Duling Distributed feedback (DFB) semiconductor lasers have a periodic modulation of refractive index, or Bragg grating, in the active region of the device. The Bragg grating causes a wavelength dependent distributed feedback of light. This thesis develops a below-threshold model for the spectra of DFB lasers. The model is shown to treatCited by: 1

Print Send Add Share. Material Information Title: Modeling of Distributed Feedback Semiconductor Lasers Creator: Shih, Meng-Mu Place of Publication: [Gainesville, Fla.

Degree Grantor: University of Florida Degree Disciplines: Electrical and Computer Engineering Committee Chair: Zory, Peter S.

Committee Members: Xie, Huikai Nishida, Toshikazu Lindner, Angela S. Notes Abstract: This work demonstrates the multi-parameter modeling processes of calculating coupling coefficients of the optical waveguide structures for various distributed feedback DFB semiconductor lasers.

Substrate-emitting DFB quantum cascade laser analyzed and performance improvement are discussed. en General Note: In the series University of Florida Digital Collections. General Note: Includes vita. Bibliography: Includes bibliographical references. Source of Description: Description based on online resource; title from PDF title page.

Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has distributed feedback laser thesis all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.

Thesis: Thesis Ph. Local: Adviser: Zory, Peter S. Record Information Source Institution: University of Florida Holding Location: University of Florida Rights Management: Copyright Shih, Meng-Mu, distributed feedback laser thesis.

Permission granted to distributed feedback laser thesis University of Florida to digitize, archive and distribute this item for non-profit research and educational distributed feedback laser thesis. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder. Shi -Chen Shih and Mrs. Peter Zory for his guidance and encouragement. His two classes of photonics and laser electronics initiated my strong interest and fundamental background for my Ph.

He provides the physics background with intuitive but deeper ins ights for my mathematical modeling. Zory is also my life mentor. His experiences distributed feedback laser thesis engineering and management in enterprises and academia has shaped into a unique life of philosophy.

I have cultured from his unique advantages which have helped me to think and solve academic and life problems from multi -facet ed perspectives. I really enjoy extensive and intensive discussions with Dr. Zory from research topics to life of philosophy, not only solving my problems wisely but also help ing me explore views m ore. With his patient and enthusiastic efforts for improving both my written and oral communication skills, I can pass the oral exam and also optimistically face unexpected challenging life issues.

I would like to thank all the other members of my superv isory committee: Dr. Toshikazu Nishida, Dr. Huikai Xie, and Dr. Angela Lindner. Xie taught me the semiconductor physical electronics and provided many suggestions during my oral proposal based on his optic s specialty. Nishida and Dr. Angela also pr ovided substantial suggestions, distributed feedback laser thesis. Some U niversity of Florida staff have work ed behind the scene.

Linder, as Associate Dean of Students Affairs, helped me deal with life issues. Debra Anderson at International Center has provided extensive help far beyond tha t which I can express. Shannon Chillingworth, my departmental graduate advisor, has PAGE 5 5 directed me to follow requirement details.

Keith Rambo provides labs and equipments. I would like to thank Dr. Zorys previous students Dr. Horng-Jye Luo for his help in the C hapter 3 of my dissertation. His mathematical modeling and manipulation techniques inspired my desire for further modeling process, distributed feedback laser thesis. I also distributed feedback laser thesis colleagues from Interdisciplinary Microsystems Group: Dr. Lei Wu and Sean under Dr.

They helped me conduct experiments on semiconductor lasers and quantum cascade lasers. This work was partly funde d by the Defense Advanced Research Projects Agency DARPA contract no. Dan Botez in University of Wisconsin. Friends from different countries have enriched my life in this college town. I distributed feedback laser thesis priceless opportunities to interact with people from different cultures. Through them, I comprehend the world of diversity. Wang, my high school classmate, has encouraged me since my graduate study in the U.

S although he has been quite busy in performing long -hour surgeries D r. Along and Dr, distributed feedback laser thesis. Shiau provide me with good suggestions about doing research. Chu provides friendly support. Ray Mr.

Justin and Mr. Toby ofte n find interesting distributed feedback laser thesis to broaden my view toward American culture. Last but definitely not the least, distributed feedback laser thesis, I want to thank my parents for their endless support and deepest love throughout the life journey, sometimes quite challenging to me. No matter where I would be, they would be with me. current diagram x for the fundamental TM mode A Diffractive waves due to gratings B Real picture of diffraction A Ray optics picture B Wavevector diagram A Ray optics picture B Wave vector diagram for the second order diffractive wave C Wave vector diagram for the first order diffractive wave corrugation amplitude a active layer thickness t buffer thickness t corrugation amplitude a for different metals A Sketch showing laser beam emission from substrate B SEM picture showing corrugation prior to device fabrication.

corrugation amplitude a for simplified 4-layer waveguide TM mode has larger interacti on. Substrateemitting DFB quantum cascade laser analyzed and performance improvement are discussed.

In the 19 60s and 19 70s, most applications were defense related and only small volumes of diode lasers were required, distributed feedback laser thesis. They became high volume products in the 19 80s and 19 90s with the advent of a pplication areas such as fiber optic communications and information technology In many of these application areas the diode lasers used have built -in diffraction gratings that provide narrow band spectral output, distributed feedback laser thesis.

This type of diode laser is now called a distributed feedback DFB laser. Ina new type of semiconductor laser that did not have a built in pn junction was demonstrated [ 3 ]. These lasers, called Quantum Cascade Lasers QCLs operate on intersubband transitions and utilize electron tunn eling to achieve population distributed feedback laser thesis in the conduction band of the semiconductor material.

These QCLs are now starting to replace cryogenic diode lasers and gas lasers that have been used for many years in molecular spectroscopy applications in the mid t o far infra -red region of the spectrum [ 4 ] To date, the narrow -band spectral output required in such applications has been achieved using diffractiongrating techniques in resonator configurations external to the semiconductor laser chip.

In order to reduce the cost of such systems, there has been considerable research activity in the last few years to develop QCLs with integrated diffraction gratings DFB -QCLs.

Since narrow band operation can be achieved using first -order DFB, distributed feedback laser thesis, most of the research act ivity in this area has been concentrated on t his type of DFB -QCL. In order to eliminate the expensive optics required to capture and PAGE 14 14 collimate the high divergence beams emitted from these first order DFB -QCLs while retaining narrow band output, a more com plex design incorporating s econd order DFB is now being researched [5 ] 1.

Current I through the laser chip produces optical gain in the active region, distributed feedback laser thesis. Cleaved facets on the longitudinal edges provide optical feedback Fig ure 1 1 b shows a typical output power 0P vs, distributed feedback laser thesis. I diagram When I is greater than the threshold current thI laser action is initiated in the semiconductor chip, distributed feedback laser thesis.

Figure Semiconductor laser A Schematic structure of semiconductor laser B Power vs. current diagram Fi gure 12 shows the schematic structure and energy -band diagram. If we rotate the laser chip shown in Figure a clockwise distributed feedback laser thesis 90 degrees and expand the area in the vicinity of the active region, we see that current I is equivalent to e lectrons moving to the positive metal contact and the active region is a quantum well QW designed to trap electrons, distributed feedback laser thesis.

In the energy band diagram, conduction band CB electrons e are trapped in the QW and recombine with valence band VB holes Dur ing this process, PAGE 15 15 photons are produced with energy 11 CHhvEE where 1 CE and 1 HE represent certain energy states in the CB and VB respectively. This process whereby electrons move from the CB t o the VB is called an i nterband t ransition.

Figure 1 2. Structure and energy band diagram of diode lasers PAGE 16 16 Figure 1 3 shows the schematic structure and energy -band diagram of the basic unit in a quantum cascade laser QCL. In a typical QCL, there will be about 20 to 30 basic units in the active region. Electrons are attracted to the positive metal contact as in the diode case but the basic process used here to achieve gain is quite different.

Electrons in the CB states of the injector region tunnel in to 2 CE states in the QW These electrons then m ake transitions to 1 CE states in the QW and produce photons with energy 21 CChvEE Since these transitions occur within the CB of the QW rather t han between the CB and VB of the QW, they are called i ntersubband transitions. Figure 1 3. Structure and energy -band diagram of the basic unit in quantum cascade lasers PAGE 17 17 1, distributed feedback laser thesis.

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The results of an investigation of the distributed feedback laser (DFL) as a source for short optical pulses is reported in this thesis. The DFL provides a uniquely simple and inexpensive alternative to synchronously pumped dye blogger.com: Irl N. Duling In this thesis, distributed reflector (DR) lasers, consisting of a DFB (distributed feedback) laser with high reflection DBR (distributed Bragg reflectors) on one end, is studied by considering wire-like active regions for the DFB section This type of diode laser is now called a distributed feedback (DFB) laser. In , a new type of semiconductor laser that did not have a built in pn junction was demonstrated [ 3 ]. These lasers, called Quantum Cascade Lasers (QCLs) operate on intersubband transitions and utilize electron tunn eling to achieve population inversion in the conduction band of the semiconductor material