1. WOLAITA SODO UNIVERSITY
COLLEGE OF NATURAL AND COMPUTATIONAL
SCIENCEDEPARTMENT OF PHYSICS
PRINCIPLE OF DYE LASER
A SENIOR PROJECT PAPER SUBMITTED TO DEPARTMENT OF
PHYSICS IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR
THE BACHELOR DEGREE OF SCIENCE (BSc) IN PHYSICS
PREPARED BY:
Preparedby: - MAMO KUTI ID NO :- phy/sum/1468/08
ADVISOR: - TsegayeB. (MSc.)
Aug, 2021
WOLAITA SODO, ETHIOPIA
2. 2
ACKNOWLEDGEMENT
Above all, it is the grace, mercy, charity, forgiveness, help and kindness of the almighty God,
who has made me still alive and helped me to accomplish my work successfully. Next I would
like to extend my heartfelt gratitude and appreciation to my advisor Doctor Kusse for his
constructive comments, tireless effort, contribution and career guidance for me around academic
matters of my project work. Lastly I want to express my deepest gratitude to my family who
have helped me in financial and moral support.
3. 3
LIST OF ABBREVIATIONS
Abbreviation meaning
CW continuous wave
prfs pulsed repetition frequencies
KHz Kilo hertz
KW kilo watt
Nm Nano meter
UV ultra violet
IR infra-red
mJ milli Joule
FPDL Flash-lamp pulsed-dye laser
AVLIS Atomic vapor laser isotope separation
MOPA Master-oscillator/power-amplifier
MOLA Master-oscillator/light-amplifier
4. 4
Table of Contents
CONTENTS PAGE
ACKNOWLEDGEMENT................................................................................................................2
LIST OF ACRONYMS.....................................................................................................................3
ABSTRACT..........................................................................................Error! Bookmark not defined.
CHAPTER ONE...............................................................................................................................6
INTRODUCTION ............................................................................................................................6
1.1 HISTORICAL BACK GROUND OF DYE LASER....................................................................6
1.2 OBJECTIVES OF THE STUDY................................................................................................8
1.2.1 General objective ................................................................................................................8
1.2.2 SPECIFIC OBJECTIVE......................................................................................................8
CHAPTER TWO..............................................................................................................................9
PRINCIPLES OF DYE LASER........................................................................................................9
2.1 Basic Dye Laser Principles.........................................................................................................9
2.2 WORKING PRINCIPLE OF DYE LASER...............................................................................10
2.2.1 ADVANTAGE OF DYE LASER ......................................................................................11
2.2.2 DISADVANTAGE OF DYE LASER.................................................................................12
2.3 PROPERTIES OF DYE LASER..............................................................................................12
2.4 COMPONENETS OF DYE LASER.........................................................................................13
2.5 TYPES OF DYE LASER.........................................................................................................14
2.5.1 Laser-Pumped Pulsed Tuneable Dye Lasers........................................................................14
2.5.2 Flash-Lamp Pulsed-Dye Laser (FPDL)...............................................................................15
2.5.3 Mode-Locked Dye Laser...................................................................................................15
2.5.4 Continuous-Wave Dye Lasers............................................................................................16
2.5.4.1 Characteristics of Performance of High-Power CW Dye Lasers.........................................16
CHAPTER THREE........................................................................................................................17
3 APPLICATION OF DYE LASER ...............................................................................................17
3.1 Application of Dye Laser in Astronomy....................................................................................17
3.2 Application of Dye Laser in Atomic Vapor Laser Isotope Separation ..........................................18
3.3 Application of Dye Laser in Manufacturing...............................................................................19
3.4 Application of Dye Laser in medicine and surgery.....................................................................19
3.5 Application of Dye Laser in Spectroscopy.................................................................................19
CHAPTER FOUR ..........................................................................................................................20
CONCLUSION...............................................................................................................................21
REFERENCES...............................................................................................................................22
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ABSTRACT
This project reviews, presents, and elaborates deeply about principles of dye laser.
Historical back ground of dye laser is also described in detail. Dye Laser has been
developed in the mid-1960s and the tunable sources of coherent radiation span the
electromagnetic spectrum from the near-ultraviolet to the near-infrared. In a few of short
decades since its invention the dye laser has found numerous applications. The unique
properties of dye laser like monochromatic, directional, coherence, and intensity or
brightness made it to become a versatile beam of light having almost inexhaustible
applications in medicine and surgery, spectroscopy, atomic vapor laser isotope separation
and manufacturing and industrial uses. In addition to applications, the project also explains
properties of dye laser, types of dye laser, advantage and disadvantage of dye laser, and
working principles of dye laser. Dye laser is unique as compared to other lasers in that
Beam diameter is very less, Construction is very simple, higher efficiency of 25%, Its beam
divergence is very less (0.8milli radians to 2milli radians), it is available in visible form.
6. 6
CHAPTER ONE
1 INTRODUCTION
1.1 HISTORICAL BACK GROUND OF DYE LASER
Dye lasers are the original tunable lasers. They were independently discovered by P. P.
Sorokin and F. P. Schäfer (and colleagues) in 1966. The tunable sources of coherent radiation
span the electromagnetic spectrum from the near-ultraviolet to the near-infrared. Dye lasers
spearheaded and sustained the revolution in atomic and molecular spectroscopy and have found
use in many and diverse fields from medical to military applications. In addition to their
extraordinary spectral versatility, dye lasers have been shown to oscillate from the femtosecond
pulse domain to the continuous wave (CW) regime. For microsecond pulse emission, energies of
up to hundreds of joules per pulse have been demonstrated. Further, operation at high pulsed
repetition frequencies (prfs), in the multi-kHz regime, has provided average powers at kW levels.
[6]
A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution.
Compared to gases and most solid state lasing media, a dye can usually be used for a much wider
range of wavelengths, often spanning 50 to 100 nanometers or more. The wide bandwidth makes
them particularly suitable for tunable lasers and pulsed lasers. A dye laser uses a gain
medium consisting of an organic dye, which is a carbon-based, soluble stain that is often
fluorescent, such as the dye in a highlighter pen. The dye is mixed with a compatible solvent,
allowing the molecules to diffuse evenly throughout the liquid. The dye solution may be
circulated through a dye cell, or streamed through open air using a dye jet. A high energy source
of light is needed to 'pump' the liquid beyond its lasing threshold. A fast discharge flashtube or
an external laser is usually used for this purpose. Mirrors are also needed to oscillate the light
produced by the dye’s fluorescence, which is amplified with each pass through the liquid.
The output mirror is normally around 80% reflective, while all other mirrors are usually more
than 99.9% reflective.
7. 7
The dye solution is usually circulated at high speeds, to help avoid triplet absorption and to
decrease degradation of the dye. A prism or diffraction grating is usually mounted in the beam
path, to allow tuning of the beam. [7]
The dye rhodamine 6G, for example, can be tuned from 635 nm (orangish-red) to 560 nm
(greenish-yellow), and produce pulses as short as 16 femtoseconds. Moreover, the dye can be
replaced by another type in order to generate an even broader range of wavelengths with the
same laser, from the near-infrared to the near-ultraviolet, although this usually requires replacing
other optical components in the laser as well, such as dielectric mirrors or pump lasers.
Peter Sorokin became interested in dyes after observing fluorescence while testing them for Q-
switching ruby lasers. He and John Lankard placed a dye cell in a laser cavity, illuminated it with
a ruby laser, and produced a laser beam that burned their photographic film. Fritz P. Schaefer at
the Max Planck Institute independently made a similar ruby-pumped dye laser soon afterward
Flash-lamp pumping followed. [19]
The first dye lasers emitted at a fixed wavelength at the peak of the dye’s gain curve. In 1967,
Bernard Soffer and B. B. McFarland at Korad replaced the rear cavity mirror in a dye laser with
a diffraction grating, which they turned to select a wavelength within the gain curve to oscillate
in the laser cavity. Individual dyes had gain over a range of wavelengths, and many different
dyes were available, making dye lasers the first broadly tunable lasers, and leading to major
advances in laser spectroscopy. [19]
In optical applications, a laser if often needed that is highly tunable and can achieve high gain.
Dye lasers are one of the oldest and most widely recognized type of tunable laser. Their
wavelength versatility and power make them well suited for laser guide stars in astronomy,
atomic laser isotope separation, and medicine. Dyes with organic compounds are continuously
pumped through a cuvette between the light source and the lasing cavity, thus selecting the
wavelength. A dye laser will typically have a wavelength between 308 and 950 nm – though
some dye lasers require manual tuning to reach the 900 nm range, with bandwidths of up to 8 nm
and frequencies (pulse repetition rate) of up to 300 Hz.
Dye lasers can be tuned by manually changing the dye cells or by altering or pumping new dyes
into the flow cell automatically via computer control. [14]
8. 8
The dye cell is often a thin tube approximately equal in length to the flashtube, with both
windows and an inlet/outlet for the liquid on each end. The dye cell is usually side-pumped, with
one or more flashtubes running parallel to the dye cell in a reflector cavity. The reflector cavity is
often water cooled, to prevent thermal shock in the dye caused by the large amounts of near-
infrared radiation which the flashtube produces. Axial pumped lasers have a hollow, annular-
shaped flashtube that surrounds the dye cell, which has lower inductance for a shorter flash, and
improved transfer efficiency. Coaxial pumped lasers have an annular dye cell that surrounds the
flashtube, for even better transfer efficiency, but have a lower gain due to diffraction losses.
Flash pumped lasers can be used only for pulsed output applications. [7]
1.2 OBJECTIVES OF THE STUDY
1.2.1 General objective
The general objective of this project is to describe, explain, and elaborate Dye laser and its
principles.
1.2.2 SPECIFIC OBJECTIVE
The specific objective of this project is to:-
narrate the history and development of dye laser
define dye laser
identify the properties of dye laser
describe the basic components of dye laser
describe the types of dye laser
explain the application of dye laser
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CHAPTER TWO
PRINCIPLES OF DYE LASER
2.1 Basic Dye LaserPrinciples
Although dye lasers cover a range of wavelengths from the near-UV to the near-IR, using dyes
of widely different chemical compositions, the basic principles are essentially identical for all of
them. A description based on a rate equation approach and on stimulated emission and
absorption cross-sections is commonly used regardless of the particular material and wavelength.
For the dyes used in practical systems, the relevant parameters have rather similar values. The
radiative properties of laser dyes depend on the structure of the dye molecule and are also
influenced by interaction with the solvent. [18]
Dye molecules are large and complicated, with many internal degrees of freedom and many
possibilities for internal energy conversion. Additionally, there are very frequent collisions with
solvent molecules. There are two main manifolds of electronic energy states: singlets and
triplets. Corresponding to each electronic state there is a broadband of vibrational-rotational
states. Both the process of optical pumping and the laser action take place between the first
excited singlet (S1) and the ground state singlet (S0) bands. Only the S1 band is radiative, because
a molecule excited to any of the higher energy levels undergoes (mainly by internal conversion)
spontaneous nonradioactive decay to S1, which is so rapid as to completely quench any emission.
Nonradioactive decay from S1 to S0 also takes place, but for laser dyes the radiative process is
much stronger. Intersystem crossing from singlet to triplet, and vice versa, also occurs non
radiatively, mainly owing to interactions between the dye and the solvent. In the triplet energy
manifold, the lowest state is metastable, while the higher energy states are also nonradioactive.
An important consequence of the rapid nonradioactive quenching of all but the S0, S1,
and T1 states is that only these three levels (bands) have non negligible populations in the dye
laser, and only they participate in stimulated emission and absorption.
Another important process is the very rapid (for our purposes, essentially instantaneous)
intraband thermalization that takes place within the vibrational-rotational continuum band of any
of the electronic states. [18]
10. 10
This means that at any time the total population within the band of a given electronic state is in a
quasi-thermal equilibrium (Boltzmann distribution). Any population change within a band is
rapidly redistributed to the whole band. The strength of the various spontaneous radiative and
nonradioactive processes are described by lifetimes. The singlet manifold may be modeled as an
effective four-level homogeneously broadened system. Homogeneous means that, owing to the
very fast intraband thermalization, all the molecules in a given band (level) participate in the
stimulated transitions from that level. Emission and absorption are spectrally broad, with the
emission displaced to longer wavelengths (lower energies). The spectral details of the broad
emission and absorption line shapes depend on the photo physics of the vibrational-rotational
continuum. In practice, the line shapes are determined experimentally. The singlet absorption
and emission curves are approximately mirror images of each other. In some dyes this shift may
be so large that there is only a small overlap between the emission and absorption curves. [18]
Lasers are also broadly divided into four categories on the basis of the material used as an active
medium. They are Solid lasers, Liquid lasers, Gas lasers, and Semiconductor lasers. Dye lasers
belong to the family of liquid lasers. The active material is a dye dissolved in a liquid solvent.
Dye lasers are among the most versatile and successful laser sources currently available in use
offering both pulsed and continuous-wave operation and tunable from the near ultraviolet to the
near infrared, these lasers are used in such diverse areas as: industrial applications, medical
applications, military applications, large-scale laser isotope separation, fundamental physics,
spectroscopic techniques, laser radar. [1]
In principle, liquid dye lasers have output powers of the same magnitude as solid-state lasers,
since the density of active species can be the same in both and the size of an organic laser is
practically unlimited.[5]
2.2 Working principle of dye laser
To operate a dye laser, an elliptical resonant cavity or resonator is used. The dye cell is placed at
one of the foci and the flash lamp is placed at the other foci in the elliptical resonant cavity. The
light emitted by the flash lamp is focused on the cell.
11. 11
The lights falling on the dye cell causes stimulated emission inside the dye. The emission of
radiation due to stimulated emission exists in all directions but the radiation (i.e. photons) is only
amplified along the axis of the cavity formed between highly reflecting mirror and semi-
transparent mirror. Tuning of Dye laser can be done using various techniques: One of the
commonly used techniques is to send a selective wavelength through the Dye. In this case, the
totally reflecting mirror of the cavity is replaced by the diffraction grating. [2]
Fig 1. Diagram showing the Working principle of dye laser
The working principle of dye laser includes;
The dye solution is usually circulated at high speed to avoid triplet absorption.
A high energy source of light is used to pump the liquid.
A fast discharge flash lamp or an external laser is usually used for pumping purpose.
The incoming light excites the dye molecules into the state of being ready to emit
stimulated radiation; the singlet state. In this state, the molecules emit light via
fluorescence, and the dye is transparent to the lasing wavelength. Within a microsecond
or less, the molecules will change to their triplet state.[5]
2.2.1 Advantage of dye laser
Beam diameter is very less.
12. 12
Construction is very simple.
High output power.
Higher efficiency of 25%.
Its beam divergence is very less. (0.8milli radians to 2milli radians)
It is available in visible form.
2.2.2 DISADVANTAGE OF DYE LASER
Cost of dye laser is very high
Some cases need other laser beam
To tune at one frequency , the laser uses birefringent element or filter making it more
costly
In dye laser it is very difficult to determine the element that actually lases because dye
has complex chemical formula. [12]
2.3 PROPERTIES OF DYE LASER
Dye lasers are very versatile. In addition to their recognized wavelength agility these lasers can
offer very large pulsed energies or very high average powers. Like any other laser, a dye laser
differs from other sources of light in that it emits light which is coherent. [7]
The organic dye laser has the distinction of being the first broadly tunable laser. It is also
capable of providing a wide variety of output forms that range from ultrashort to high energy
pulses, and from highly stable continuous wave (CW) narrow linewidth oscillation to high
average power emission. [13]
Different dyes have different emission spectra or colors thus allowing dye lasers to cover a
broad wavelength range from the ultraviolet (320 nm) to the infrared at about 1500 nm.
A unique property of dye lasers is the broad emission spectrum (typically 30–60 nm) over
which gain occurs. Dye lasers are similar to solid-state lasers in that they consist of a host
material (in this case a solvent such as alcohol) in which the laser (dye) molecules are dissolved
at a concentration of the order of 1 part in 10,000. A dye can selectively absorb light with certain
wavelengths corresponding to certain electronic transitions. However, it may also
emit fluorescence and even exhibit laser gain.
13. 13
A wide range of emission wavelengths from the ultraviolet to the near-infrared region is
accessible with different laser dyes, most often used in a liquid solution.
They offer a broad gain bandwidth and thus broad wavelength tunability as well as the potential
for ultrashort pulse generation with passive mode locking .
Dye lasers are available in either pulsed (up to 50–100 mJ) or continuous output (up to a few
Watts) in table-top systems that are pumped by either flash lamps or by other lasers such as
frequency-doubled or tripled YAG lasers or argon ion lasers. Most dye lasers are arranged to
have the dye and its solvent circulated by a pump into the gain region from a much larger
reservoir, since the dye degrades slightly during the excitation process. Dyes typically last for 3
to 6 months in systems where they are circulated. Dye lasers are used mostly for applications
where tunability of the laser frequency is required, either for selecting a specific frequency that is
not available from one of the solid-state or gas lasers, or for studying the properties of a material
when the laser frequency is varied over a wide range. The following are the common
properties of dye laser.
Continuous- wave or mode-locked Rhodamine 6G lasers; flash lamp-pumped lasers with
various dyes
Have applications in spectroscopy; ultrashort pulse generation
Uses other lasers or flash lamps as pump sources
Its power efficiency is a few percent to an order of 50%
Its accessible wave length is mostly visible and near infrared
Tuning wave length is possible over tens of nanometers
Have an average output power typically between 10 mW and 1 W, but >1 kW is possible
Have beam quality that is normally diffraction-limited; worse for pulsed high-power
devices
Continuous-wave operation is possible
Has nanosecond pulse generation, with pulsed pumping. [11]
2.4 COMPONENETSOF DYE LASER
14. 14
Like any other laser, a dye laser consists of three basic components. These are:-
1. Lasing material or active medium.
2. External energy source (pumping system).
3. Optical resonator.
Active Medium: - is a gain medium of laser in which population inversion can takes
place. Laser medium may be solid, liquid, or gas.
Pumping System: - is an energy providing source which is applied to the ends of
laser medium to cause population inversion. Pumping system is may be optically,
electrically or chemically.
Optical Resonator: - is a pair of high reflecting mirrors that reflects a light either
totally or partially, and which they are placed at the ends of laser medium and are
important for amplification as well as reflection of light. [3]
2.5 TYPES OF DYE LASER
Dye lasers come in various types. These are;
1. laser-pumped pulsed tuneable dye lasers
2. flash lamp-pumped pulsed dye lasers
3. mode-locked dye lasers
4. Continuous-wave (CW) tuneable dye lasers [10]
2.5.1 Laser-Pumped Pulsed Tuneable Dye Lasers
Another method of achieving pulsed laser operation is to pump the laser material with a source
that is itself pulsed, either through electronic charging in the case of flash lamps, or another laser
which is already pulsed. Pulsed pumping was historically used with dye lasers where the inverted
population lifetime of a dye molecule was so short that a high energy, fast pump was needed.
The way to overcome this problem was to charge up large capacitors which are then switched to
discharge through flash lamps, producing an intense flash. Pulsed pumping is also required for
three-level lasers in which the lower energy level rapidly becomes highly populated preventing
15. 15
further lasing until those atoms relax to the ground state. These lasers, such as the excimer laser
and the copper vapor laser, can never be operated in CW mode. [7]
2.5.2 Flash-Lamp Pulsed-Dye Laser (FPDL)
Flash-lamp pulsed-dye laser (FPDL) is a no ablative technology, typically used in vascular
malformation therapy due to its specificity for hemoglobin. FPDL treatments were performed in
a large group of patients with persistent and/or recalcitrant different dermatological lesions with
cutaneous micro vessel involvement. [4]
Generally, high-energy dye lasers are pumped by coaxial or linear flash lamps. The main
advantage of coaxial systems over linear ones is the superior optical coupling between flash lamp
and dye solution. Nowadays, for low repetition rates coaxial systems deliver higher output
energy per pulse compared with linear systems. However, the former produce thermal effects
and shock waves which affect beam quality, reproducibility, and restrict the repetition rate. To
overcome these problems, tri axial and quad axial systems have been developed; but for these the
output energy is reduced.
For high repetition rates, the linear flash lamp system is generally superior. It gives more energy
per pulse with extended lifetime and better reliability compared to multiaxial devices. [16]
2.5.3 Mode-Locked Dye Laser
A mode-locked laser is capable of emitting extremely short pulses on the order of tens
of picoseconds down to less than 10 femtoseconds. These pulses will repeat at the round trip
time, that is, the time that it takes light to complete one round trip between the mirrors
comprising the resonator. Due to the Fourier limit (also known as energy-time uncertainty), a
pulse of such short temporal length has a spectrum spread over a considerable bandwidth. Thus
such a gain medium must have a gain bandwidth sufficiently broad to amplify those frequencies.
An example of a suitable material is titanium-doped, artificially grown sapphire (Ti:sapphire)
which has a very wide gain bandwidth and can thus produce pulses of only a few femtoseconds
duration.
Such mode-locked lasers are a most versatile tool for researching processes occurring on
extremely short time scales (known as femtosecond physics, femtosecond chemistry and ultrafast
16. 16
science), for maximizing the effect of nonlinearity in optical materials (e.g. in second-harmonic
generation, parametric down-conversion, optical parametric oscillators and the like). Unlike the
giant pulse of a Q-switched laser, consecutive pulses from a mode-locked laser are phase-
coherent, that is, the pulses (and not just their envelopes) are identical and perfectly periodic. For
this reason, and the extremely large peak powers attained by such short pulses, such lasers are
invaluable in certain areas of research. [[7]
2.5.4 Continuous-Wave Dye Lasers
Dye lasers have had a significant impact in high-resolution spectroscopy and other applications,
including laser cooling, given their tunability, excellent TEM00 beam quality, and intrinsic
narrow linewidths, which can readily reach a level of a few megahertz. Continuous-wave dye
lasers typically use Ar+ and Kr+ as excitation sources, although in principle they could use any
compatible laser yielding TEM00 emission. It should be noted that CW dye lasers have been
excited with a variety of lasers, including diode lasers (see, for example, Scheps, 1993). Table
9.9 summarizes the performance of relatively high-power dye lasers, some of which yield SLM
oscillation at linewidths in the megahertz regime. [17]
Table 1. Performance of High-Power CW Dye Lasers
Cavity Spectral range (nm) Linewidth Output power Efficiency (%)
Lineara - 33 Wb,c 30
Lineara 560–650 SLMd 33 We,f 17
Ringa 407–887g SLMd 5.6 Wh 23.3
2.5.4.1 Characteristics of Performance of High-Power CW Dye Lasers
The following are the basic characteristics of high-power CW lasers;
Under Ar+
laser excitation.
Maximum CW power quoted: 52 W for a pump power of 175 W.
Using Rhodamine 6G at 0.7 mM.
Linewidth values can be in the few MHz range.
Without intracavity tuning prism, quoted output power is 43 W for a pump power of 200 W.
Using Rhodamine 6G at 0.94 mM.
Using 11 dyes.
Using Rhodamine 6G.
17. 17
CHAPTER THREE
3 APPLICATION OF DYE LASER
Dye lasers are very versatile. In addition to their recognized wavelength agility these lasers can
offer very large pulsed energies or very high average powers. Flash lamp-pumped dye lasers
have been shown to yield hundreds of Joules per pulse and copper-laser-pumped dye lasers are
known to yield average powers in the kilowatt regime.
Dye lasers are used in many applications including:
astronomy (as laser guide stars),
atomic vapor laser isotope separation
manufacturing
medicine and surgery
spectroscopy
Tunable lasers are used in swept-frequency metrology to enable measurement of absolute
distances with very high accuracy. A two axis interferometer is set up and by sweeping the
frequency, the frequency of the light returning from the fixed arm is slightly different from the
frequency returning from the distance measuring arm. This produces a beat frequency which can
be detected and used to determine the absolute difference between the lengths of the two arms.
[7]
3.1 Application of Dye Laser in Astronomy
Laser tools help researchers identify an ancient Mars ocean, capture clearer images of distant
galaxies, and simulate an exploding supernova.
Examining the Martian surface
Today Mars is bone dry, with an atmosphere only a tiny fraction as dense as Earth's and too thin
to allow liquid water to exist on the surface. Astronomers have theorized for years, though, that
water must have existed on the planet's surface several billion years ago. Supporting this theory
are photographs taken by the Viking and other spacecraft that show vast channels that could only
18. 18
have been cut by running water. The MOLA maps have helped to reveal just how much water
Mars once had. [15]
Guided by a laser star
On Earth, lasers increasingly are helping astronomers fine-tune telescope feedback. Until
recently, atmospheric turbulence had restricted the angular resolution of large telescopes to not
much better than a backyard telescope. Helping to resolve this problem are adaptive optics that
can automatically compensate for atmospheric turbulence by distorting a mirror in the light path.
The basic premise is to look at the distortion of the wave front from a bright point source and
then compensate for the distortions to bring the wave front to a point focus. This corrects for
turbulence over the whole field of view. [15]
Supernova in the laboratory
Laser-based technology is also helping astronomers move toward active experiments in addition
to the passive observations they have traditionally been limited to because of the scale of the
phenomena observed. Laboratory astrophysics involves modeling astrophysical events at vastly
reduced scales. Recent experiments have shown lasers to be central to such modeling because of
their capability to concentrate large amounts of energy in small space and time. [15]
3.2 Application of Dye Laser in Atomic Vapor Laser Isotope Separation
Atomic vapor laser isotope separation (AVLIS) is a general process for converting a feed stream
into a product stream in which a selected set of isotopes has been enriched or depleted. The heart
of the process is the selective multistep photoionization of an atomic vapor stream. The process
hardware is divided into a separator system and a laser system that are, to a great degree,
mechanically independent. Atomic vapor is produced in the vaporizer and expands upwards in
vacuum. Tunable laser frequencies are generated in a dye laser system that is in turn driven by a
pump laser system. Copper-vapor lasers serve as the pump lasers in the major systems we have
constructed to date. Both the pump lasers and tunable lasers are configured in master-
oscillator/power-amplifier (MOPA) chains. The laser light illuminates the atomic vapor between
19. 19
the plates of an ion extractor. Photo ions are drawn to and neutralized at negatively biased
extractor plates. The remaining vapor streams through to the roof of the separator. [9]
3.3 Application of Dye Laser in Manufacturing
Manufacturing case study i.e. Dye lasers curing of pigmented coatings.
Diagnostic applications of dye lasers.
Remote sensing applications of dye lasers to monitor industrial pollution. [8]
3.4 Application of Dye Laser in medicine and surgery
The characteristics of dye lasers make them a valuable source of coherent light for medical
applications, for example
Ar+ laser-pumped dye laser for cancer diagnosis and treatment.
They are used to treat port-wine stains and other blood vessel disorders, scars and kidney
stones.
They can be matched to a variety of inks for tattoo removal, as well as a number of other
applications.
Flash lamp-pumped dye lasers for such divers bits as incurable blood vessel birth marks
of infant and children, the Insightly "sun burst" small veins in thighs and legs.
Breaking stones in the ureters and in the gall bladder.
Pulsed dye lasers are considered for corneal ablation.
Applied in several areas, including dermatology where they are used to make skin tone.
The wide range of wavelengths possible allows very close matching to the absorption
lines of certain tissues, such as melanin or hemoglobin, while the narrow bandwidth
obtainable helps reduce the possibility of damage to the surrounding tissue. [8]
3.5 Application of Dye Laser in Spectroscopy
In spectroscopy, dye lasers can be used to study the absorption and emission spectra of
various materials. Their tunability, (from the near-infrared to the near-ultraviolet), narrow
bandwidth, and high intensity allows a much greater diversity than other light sources. The
variety of pulse widths, from ultra-short, femtosecond pulses to continuous-wave operation,
20. 20
makes them suitable for a wide range of applications, from the study of fluorescent lifetimes
and semiconductor properties to experiments. [8]
The use of synchrotron radiation and lasers in the experiments of atomic and ion
spectroscopy, and the advanced techniques in the photoelectrons spectroscopy and
fluorescence measurements, make possible strong development in the theoretical
investigations of resonant or auto-ionizing states of atoms and ions. Theoretically auto-
ionizing states in resonant photoionization of atoms and ions is very important in the
collision and radiational processes which take place in hot astrophysical and laboratory
plasma ,in the processes of selective photoionization for the resolution of different problems
in laser physics and atomic isotope separation [8]
21. 21
CHAPTER FOUR
4 CONCLUSION
We have concluded and evaluated that, dye lasers are the original tunable lasers. A dye laser is
a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared
to gases and most solid state lasing media, a dye can usually be used for a much wider range
of wavelengths, often spanning 50 to 100 nanometers or more. Dye lasers belong to the family of
liquid lasers. The active material is a dye dissolved in a liquid solvent.
Dye lasers are among the most versatile and successful laser sources currently available in use
offering both pulsed and continuous-wave operation and tunable from the near ultraviolet to the
near infrared, these lasers are used in such diverse areas as: industrial applications, medical
applications, military applications, large-scale laser isotope separation, fundamental physics,
spectroscopic techniques, laser radar. Different dyes have different emission spectra or colors
thus allowing dye lasers to cover a broad wavelength range from the ultraviolet (320 nm) to the
infrared at about 1500 nm.
A unique property of dye lasers is the broad emission spectrum (typically 30–60 nm) over
which gain occurs. Although dye lasers cover a range of wavelengths from the near-UV to the
near-IR, using dyes of widely different chemical compositions, the basic principles are
essentially identical for all of them. Dye lasers come in various types. These are; laser-pumped
pulsed tuneable dye lasers, flash lamp-pumped pulsed dye lasers, mode-locked dye lasers and
Continuous-wave (CW) tuneable dye lasers.
Dye lasers are very versatile. In addition to their recognized wavelength agility these lasers can
offer very large pulsed energies or very high average powers. Because of its versatility and
tunability dye lasers were having almost inexhaustible applications in astronomy (as laser guide
stars),atomic vapor laser isotope separation, Manufacturing, medicine and surgery, and
spectroscopy.
