MILITARY TECHNICAL ACADEMY
ENG. ANDREEA RODICA STERIAN
CONTRIBUTIONS TO THE STUDY OF
COHERENT RADIATION AMPLIFICATION
IN OPTOELECTRONIC SYSTEMS
SUMMARY OF THE Ph D THESIS
SCIENTIFIC SUPERVISER:
Gl.Bg.(R) PROF.UNIV.DR.ENG. EMIL CREŢU
BUCUREŞTI, 2005
1
SUMMARY OF THE Ph D THESIS
TABLE OF CONTENTS
Chapter I
INTRODUCTION………………………………………………………….........
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Chapter II
FUNDAMENTAL INTERACTIONS IN THE DISSIPATIVE QUANTUM
SYSTEMS … ……………………………………………………………………
II.1 DISSIPATION IN THE QUANTUM SYSTEMS………………………………..
II.2 THE CORRELATION BETWEEN THE COUPLING COEFFICIENTS AND
THE ENVIRONMENT OBSERVABLES IN THE LINDBLAD EQUATION ……….
II.3 MICROSCOPIC EXPRESSIONS OF THE MASTER EQUATION
COEFFICIENTS ………………………………………………………………………..
II.4 FERMION SYSTEMS COUPLED WITH THE FREE ELECTROMAGNETIC
FIELD …………………………………………………………………………………..
II.5 COMMUTATION EFFECTS IN DENSE MEDIA……………………………..
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11
13
16
21
24
Chapter III
AMPLIFICATION OF THE RADIATION IN THE ERBIUM DOPED
SYSTEMS ……………………………………………………………………...
III.1. ERBIUM DOPED OPTICAL FIBERS ………………………………………….
37
37
III.1.1 General characterization …………………………………………………..
37
III.1.2 Mathematical models …………………………………………………….
40
III.1.3 Numerical modelling. Results and conclusions……………………………
51
III.2. LASER SYSTEMS IN ERBIUM DOPED ACTIVE MEDIA …………………...
53
III.2.1 The characterization of the interaction processes………………………...
53
III.2.2 The computational model …………………………………………………
59
III.2.3 Numerical modelling of the crystal laser ………………………………..
62
III.2.4 Numerical modelling of the fiber laser …………………………..
76
III.2.5 Nonlinear dynamics of the Erbium doped fiber laser …………………..
90
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Chapter IV
RADIATION GENERATION AND AMPLIFICATION IN
NANOSTRUCTURES …………………………………………………………
IV.1 MATHEMATICAL MODELS OF THE QUANTUM WELL LASERS… ………
97
97
IV.1.1 Introduction…………………………………………………………………
97
IV.1.2 General model of the laser diode……………………………………………
98
IV.1.3 Quantum well model with liniar saturation of the gain……………………..
100
IV.1.4 Quantum well model with nonliniar saturation of the gain ………………...
102
IV.1.5 Quantum well model with separate heterostructure confinement………….
105
IV.2 NUMERICAL SIMULATIONS…..………………………………………………
107
IV.2.1 The dynamics and the frequency characteristics……………………………
107
IV.2.2 The modulation of the laser diode ………………………………………...
113
IV.2.3 Nonlinear dynamics of the quantum well laser …………………………...
119
IV.3 THE MEASUMENT OF THE EMISSION SPECTRUM OF THE C3
QUANTUM WELL LASER
IV.3.1The experimental setup………………………………………………...
127
127
IV.3.2Experimental results……………………………………………………
133
Chapter V
OPTOELECTRONIC EQUIPMENTS AND SYSTEMS. TELEMETRIC
SYSTEM ON 1,55 μm …………………………………………………………..
139
V.1 FUNCTIONAL AND CONSTRUCTIVE PRINCIPLES………………………...
139
V.2 LASER TRANSMITTERS ON 1,55 μm ………………………………………..
141
V.3 PHOTODETECTORS FOR TELEMETRY ……………………………………
146
V.4 RESEARCH AND RESULTS ……………………………………………………
146
Chapter VI
INTERACTION OF THE COHERENT RADIATION WITH
BIOLOGICAL TISSUES………………………………………………………
147
VI.1 INTRODUCTION ……………………………………………………………….
147
VI.2 MONTE CARLO SIMULATION OF THE TISSUE LASER RADIATION
150
3
INTERACTION…………………………………………………………………………
VI.2.1 The interaction parameters in the Monte Carlo simulation………………..
VI.2.2 Numerical results ……………………………………………………….
150
154
VI.3 BEHAVIOUR IN THE LASER FIELDS OF THE BIOLOGICAL MEMBRANE
160
VI.3.1 The biological membrane: concept, structure, properties….……………...
160
VI.3.2 The experimental and computer studies.…………………………………...
161
Chapter VII
CONTRIBUTIONS AND CONCLUSIONS .………………………………...
165
BIBLIOGRAPHY……………………………………………………………….
171
SUMMARY OF THE Ph D THESIS …………………………………………
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KEY WORDS
The main key words of the Ph D thesis are:
- bifurcations
- laser transition;
- biological membrane
- Markoff approximation
- Boltzmann distribution
- master equation;
- boson;
- mesomorphic state;
- coherent radiation
- modulation index
- colasing process;
- Monte Carlo method
- crystal laser
- nonlinear dynamics
- density matrix;
- optical communication
- digital processing
- period doubling
- dissipative potential;
- photon lifetime;
- environment operator;
- Planck law;
- erbium ion
- quantum controllability;
- fermion;
- quantum well laser
- fiber optics
- random variable;
- fluctuation
- rate equations
- Gaussian noise;
- relaxation frequency
- high-bit rate
- resonant cavity
- host material
- route to chaos
- infrared radiometer
- Runge-Kutta method
- ion pair
- stability diagram
- laser modulation
- stimulated emission
- laser threshold
- strange attractor
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SUMMARY OF THE Ph D THESIS
The subject of the coherent radiation amplification is treated taking
into account the complexity of the phenomena which govern the field
substance interaction correlated with the coherent light generation by
stimulated emission, the laser being an „amplifier with feedback“ having as
principal characteristics the optical gain, in a medium with population
inversion.
The introduction shortly presents the importance and the actuality of
the theme and also, the results of the effected researches and the most
important contributions and conclusions.
The first part of the thesis shows the theoretical research of the author
concerning the modeling and characterization of the dissipative structures
generally, the dissipation being an essential property of the system with self
organization which include the laser type systems also.
Next we present the research work for developing two categories of
systems based on radiation amplification, namely: the erbium doped systems
and nanostructures.
From the first category of systems we have studied two representative
types of erbium lasers (crystal and fiber) and the optical fibers used as
amplifiers also.
Concerning the second category, the quantum well lasers were
studied, as the most important systems for the information science and
technologic development.
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In the last part of the thesis we have presented the research for the
development some experimental methods and techniques including the
studies of the interaction of coherent radiation with the organic tissues.
The most important contributions presented in the thesis are:
-
establishing of new formulae which relate the coupling
parameters aim from Lindblad equation with environment operators Γ i ;
-
the proposal of microscopic quantitative expressions for the
dissipative coefficients of the master equations;
-
based on Maxwell-Bloch equations with consideration of the
interactions between nearing atomic dipoles, for the dense optical media we
have shown that in the presence of the optical pulses, the population
inversion oscillates between two extreme values, depending on the strength
of the interaction and the optical pulse energy;
-
we developed a computational specific software, to verify the
experimental and numerical existing models and
in the same time, to
discover new important situations for operative systems design and
implementation;
-
we realized the numerical simulation of the erbium doped fiber
amplifier concerning the functional and constructive parameters; it was
demonstrated that for the Er3+ doped fiber laser, the optimum operation
condition are obtained for λ = 791nm, when the upper laser level is directly
pumped but in the presence of the „colaser“ process witch improves two
times the laser efficiency for λ = 3 µm;
-
the Er3+ laser system functionment and optimization was studied
for different host material, using 3D numerical simulation to take into
account the characteristic parameters variations in the range of values
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resulting from experience; the material selection recommends as efficient
materials LiY F8 and BaY F8;
-
we also put into evidence the existence of a strong
interdependence between active medium parameters τ1 , τ2 and σ13 with
important role in the designing of the erbium laser systems with given
functional parameters;
-
we demonstrated the stable, nonchaotic operation of the
analyzed laser systems and the modulation performance of them using the
communications theory methods;
-
for the erbium doped fiber laser we explained the complex
dynamics of this type of device by simulating the time dependence of the
output power correlated with the corresponding changes in the populations
of the implied levels;
-
a tandem system of two lasers devices (a crystal laser oscillator
and an fiber amplifier) was proposed to realize a more efficient system
having the performance of each of the component devices;
-
from the numerical simulation of the complex nonlinear
dynamics of the fiber laser we have determined the critical value of the ionpair concentration for which the laser stably operate, irrespective of the
pumping level;
-
a computational software was elaborated to study numericaly
the quantum well lasers (QWL), for the characterization of these devices as
circuit elements: the time response to different types of signals, frequency
response using the small signal model, stable operation and chaotic
behaviour depending on the modulation index as an input parameter;
-
for the QWL we also put into evidence, their complex nonlinear
dynamics, characterized by bifurcation points and chaos, the critical values
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of the parameters being determined. We have demonstrated that a laser
diode can be used as a source of ultrashort pulses, useful for the high-rate
optical communications system;
-
the obtained results concerning the erbium doped laser active
media were applied to a telemetric system on 1,55µm;
-
a systematic study on the photon propagation in the tissues was
realized using the Monte Carlo method, the quantitative evaluation of the
representative parameters of interaction: reflectivity, transmisivity and
absorption
probability of the radiation the tissue being graphically
represented to be used for example in the design of the laser therapy
techniques.
-
we have studied experimentally and numerically the behaviour
of the biological membranes in the laser field . The nonlinear effects as self
modulation and optical bistability were characterized as being essential for
understanding the effects of biostimulation and bioemission of the tissues
as well as the working mechanism of the biological membrane as living
tissues.
-
the possibility to control the output optical field by means of the
concentration of the cholesterol in the mixture with the fatty acids was
proposed as method to determine experimentally the concentration of
cholesterol in the liquid crystal devices by measuring this parameter.
A number of 21 bibliographic references belonging to eng. Andreea
Rodica Sterian as author and coauthor, published in prestigious journals or
communicated at international conferences in this field, demonstrate the
recognition of the thesis contributions for optoelectronics development.
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CURRICULUM VITAE
Assistant professor ing. Andreea Rodica Sterian
Date of birth, graduate degrees:
1 January 1980, Turnu Măgurele, România
2003, Faculty of Electrotechnics, University “Politehnica” of Bucharest; „Diploma
for exellence“ of the University, for professional activity at graduation.
Scientific postgraduate activity and teaching position:
- full time assistant professor at Physics Department , Bucharest
Polytechnic University (2003-2005)
- part time research worker at Prooptica S.A., Bucharest (2003-2005)
Present place of employment:
University “Politehnica” of Bucharest, Physics Department
Scientific publications:
Author or co-author of 2 books, 16 scientific papers, 10 scientific contributed
papers at the International Conferences.
International grants and diploma:
1. Institute of Physics, London, U.K., Grant for participation in EPS – 11
Conference: “Trends in Physics”, London, September 1999, UK
2. Grant for participation at the International School of Quantum Electronics,
18 – 22 September 2000, Varna, Bulgaria
3. Institute of Physics, London, U.K., EPS – 11: “Trends in Physics”,
Certificate of participation in the “Young Physicists”, Poster Competition,
Church House Conference, London, 6-10 September 1999
4. Eleventh International School on Electronics “Laser Physics and
Applications”, 18 – 22 September 2000, Varna, Bulgaria (Certificate of
Participation and selection in the “Young Scientist Contest” by SPIE
Bulgarian Chapter, Institute of Electronics and Bulgarian Academy of
Sciences).
Professional public activities. Membership:
1. Romanian Society for Optoelectronics, member from 1998;
2. Institute of Physics, London, U.K., Quantum Electronics Division,
associate member from 2000;
3. Academic Centre of Optical Engineering and Photonics, founding member
in 1998;
4. International Society for Optical Engineering (SPIE), member from 2003;
5. European Physical Society and Romanian Physical Society, member from
2004.
Scientific contracts: 6
(ANSTI – T, CNCSIS – A, RELANSIN, CERES)
Foreign languages: English, French and Russian.
05.05.2005
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