Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. It differs from other sources of light in that it emits light coherently, which allows for a high intensity beam with low divergence. The key components are an amplifying medium that can be pumped to invert a population of atoms or molecules to higher energy levels, and an optical resonator formed by two or more mirrors to provide feedback of the light emitted from the amplifying medium. When the population inversion condition is achieved, stimulated emission produces a cascade of photons with the same phase and wavelength.
This belongs to Physical Chemistry portion and it contains most of
things about laser working and principles.
By Aaryan Tyagi's Group
M.Sc. Applied Chemistry (1 Sem)
Amity University, Noida
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation
This belongs to Physical Chemistry portion and it contains most of
things about laser working and principles.
By Aaryan Tyagi's Group
M.Sc. Applied Chemistry (1 Sem)
Amity University, Noida
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond.
Among their many applications, lasers are used in optical disk drives, laser printers, and barcode scanners; DNA sequencing instruments, fiber-optic and free-space optical communication; laser surgery and skin treatments; cutting and welding materials; military and law enforcement devices for marking targets and measuring range and speed; and laser lighting displays in entertainment.
Modern telescopes use laser technologies to compensate for the blurring effect of the Earth’s atmosphere.
Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, which is diffraction-limited. Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance.
Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively great distance (the coherence length) along the beam. A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase that vary randomly with respect to time and position, thus having a short coherence length.
Lasers are characterized according to their wavelength in a vacuum. Most "single wavelength" lasers actually produce radiation in several modes having slightly differing frequencies (wavelengths), often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously. There are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all such devices are classified as "lasers" based on their method of producing light, i.e., stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not b
Usually, analysis is not considered an easy subject and it can't be understood on its own if you don't have some proper notes and clear concepts so I am here to help you in analysis for clearing few concepts on UV-Visible spectrophotometer, soon will come up with a new set of notes on new topic depending upon the response.
A laser is a device that generates light by a process called STIMULATED EMISSION.
The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation
Semiconducting lasers are multilayer semiconductor devices that generates a coherent beam of monochromatic light by laser action. A coherent beam resulted which all of the photons are in phase.
Contents
Definition of a laser
Emission and absorption of radiation
Population Inversion
Optical Feedback
Fundamentals of laser operation
Laser Hazards
PRESENTATION 4- Basics of Laser in Dermatolgy
It includes -
Laser spectrum
Definition Laser
Classification of Lasers
Laser Theories
Laser terminology
Laser Hazards
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
4. THE BOHR ATOM MODEL
Niels Bohr proposed, in 1913, what is now called the Bohr
model of the atom. He suggested that electrons could only
have certain classical motions:
1. Electrons in atoms orbit the nucleus.
2. The electrons can only orbit stably, without radiating, in certain
orbits (called by Bohr the "stationary orbits") at a certain discrete set
of distances from the nucleus. These orbits are associated with
definite energies and are also called energy shells or energy levels. In
these orbits, the electron's acceleration does not result in radiation
and energy loss as required by classical electromagnetics. The Bohr
model of an atom was based upon Planck's quantum theory of
radiation.
3. Electrons can only gain and lose energy by jumping from one
allowed orbit to another, absorbing or emitting electromagnetic
radiation with a frequency ν determined by the energy difference of
the levels according to the Planck relation:
5. THE EMISSION-ABSORPTION PRINCIPLE
• ABSORPTION:
• AN ATOM IN A LOWER LEVEL ABSORBS A PHOTON OF FREQUENCY HΝ AND MOVES TO AN UPPER LEVEL
• SPONTANEOUS EMISSION
• AN ATOM IN AN UPPER LEVEL CAN DECAY SPONTANEOUSLY TO THE LOWER LEVEL AND EMIT A PHOTON OF FREQUENCY HΝ IF THE TRANSITION
BETWEEN E2 AND E1 IS RADIATIVE
• THIS PHOTON HAS A RANDOM DIRECTION AND PHASE
• STIMULATED EMISSION
• AN INCIDENT PHOTON CAUSES AN UPPER LEVEL ATOM TO DECAY, EMITTING A “STIMULATED” PHOTON WHOSE PROPERTIES ARE IDENTICAL TO THOSE
OF THE INCIDENT PHOTON
• THE TERM “STIMULATED” UNDERLINES THE FACT THAT THIS KIND OF RADIATION ONLY OCCURS IF AN INCIDENT PHOTON IS PRESENT
• THE AMPLIFICATION ARISES DUE TO THE SIMILARITIES BETWEEN THE INCIDENT AND EMITTED PHOTONS
12. POPULATION INVERSION
When a sizable population of electrons resides in upper levels, this condition is called
a "population inversion", and it sets the stage for stimulated emission of multiple
photons. This is the precondition for the light amplification which occurs in a LASER
and since the emitted photons have a definite time and phase relation to each other,
the light has a high degree of coherence. The two photons that have been produced
can then generate more photons, and the 4 generated can generate 16 etc… etc…
which could result in a cascade of intense monochromatic radiation.
13. POPULATION INVERSION AND PUMPING
•
•
•
•
•
•If there are more atoms in the upper level (N2) than in
the lower level (N1), the system is not at equilibrium
•A situation not at equilibrium must be created by
adding energy via a process known as “pumping” light
in order to raise enough atoms to the upper level
•This is known as population inversion
•Light is amplified when the population inversion is
positive
•Pumping may be electrical, optical or chemical
14. TWO LEVEL LASER NOT POSSIBLE
Optical pumping will at most only achieve equal population of a two-level system. This is because the
probabilities for raising an electron to the upper level and inducing the decay of an electron to the lower level
(simulated emission) are exactly the same! In other words, when both levels are equally populated, the numbers
of electrons "going up" and "down" will be the same, so you cannot achieve population inversion which is
required for lasers.
The solution is to use a third metastable level. The pumping will be between the other two, but electrons in the
upper energy level will quickly decay into the metastable level, leaving the upper level practically unpopulated at
all times. The transition from the metastable level to the ground level has a different frequency: the laser
frequency. The pumping frequency is between upper level and the ground level, so the pumping is off-resonant
to the laser transition and will, thus, not trigger stimulated emission.
18. THRESHOLD CONDITION FOR LASER ACTION
Two conditions must be satisfied for oscillation to occur:
1. The amplifier gain must be greater than the loss in the feedback
system so that net gain is incurred in a round trip through the feedback
loop.
2. The total phase shift in a single round trip must be a multiple of 2𝝅 so
that the fedback input phase matches the phase of the original input.
19. OPTICAL RESONATOR
Only those perpendicular to the mirrors will be reflected
back to the active medium, They travel together with
incoming photons in the same direction, this is the
directionality of the laser.
20.
21. • LASER AMPLIFIER
•
AMPLIFYING OR GAIN MEDIUM
•
•
PUMPING SYSTEM
•
•
1.
2.
3.
OPTICAL RESONATOR (OR CAVITY)
•
•
• LASER OSCILLATOR
22. DIELECTRIC MIRROR
A dielectric mirror, is a type of mirror composed of multiple thin
layers of dielectric material, typically deposited on a substrate of glass or
some other optical material. By careful choice of the type and thickness of the
dielectric layers, one can design an optical coating with specified reflectivity at
different wavelengths of light. Dielectric mirrors are also used to produce
ultra-high reflectivity mirrors: values of 99.999% or better over a narrow range
of wavelengths can be produced using special techniques. Alternatively, they
can be made to reflect a broad spectrum of light, such as the entire visible
range or the spectrum. Dielectric mirrors function based on
the interference of light reflected from the different layers of dielectric stack.
23. CHARACTERISTICS OF LASER
• The second photon has the same energy, i.e.
the same wavelength and color as the first
– laser has a pure color
• It travels in the same direction and exactly in
the same step with the first photon
– laser has temporal coherence
Comparing to the conventional light, a laser is
differentiated by three characteristics. They are:
Directionality,
pure color,
temporal coherence.
25. RUBY LASERS
A ruby laser is a solid-state laser that uses a
synthetic ruby crystal as its gain medium. The first
working laser was a ruby laser made byTheodore H. "Ted"
Maiman at Hughes Research Laboratories on May 16, 1960.
A ruby laser most often consists of a ruby rod that must
be pumped with very high energy, usually from a flashtube, to
achieve a population inversion. The rod is often placed
between two mirrors, forming an optical cavity, which
oscillate the light produced by the ruby's fluorescence,
causing stimulated emission. Ruby is one of the few solid
state lasers that produce light in the visible range of the
spectrum, lasing at 694.3 nanometers, in a deep red color,
with a very narrow linewidth of 0.53 nm.
26. HELIUM-NEON LASER
The HeNe laser operates in a high-voltage (kV), low-current (mA)
glow discharge. Its most familiar output wavelength is 633 nm (red),
but HeNe lasers are also available with output at 543 nm (green), 594
nm (yellow), 612 nm (orange), and 1523 nm (near infrared). Helium is
the major constituent (85 percent) of the gas mixture, but it is the
neon component that is the actual lasing medium. The mechanism
producing population inversion and light amplification in a HeNe
laser plasmaoriginates with inelastic collision of energetic electrons
with ground state helium atoms in the gas mixture. As shown in the
accompanying energy level diagram, these collisions excite helium
atoms from the ground state to higher energy excited states, among
them the 23S1 and 21S0 long-lived metastable states. Because of a
fortuitous near coincidence between the energy levels of the two He
metastable states, and the 3s2 and 2s2 levels of neon, collisions
between these helium metastable atoms and ground state neon
atoms results in a selective and efficient transfer of excitation energy
from the helium to neon.
27. SEMICONDUCTOR DIODE LASERS
The means of generating optical gain in a diode laser, the
recombination of injected holes and electrons (and
consequent emission of photons) in a forward-biased
semiconductor pn junction, represents the direct conversion
of electricity to light. This is a very efficient process, and
practical diode laser devices reach a 50-percent electrical-
to-optical power conversion rate, at least an order of
magnitude larger than most other lasers. Semiconductor
lasers are lasers based on semiconductor gain media,
where optical gain is usually achieved by stimulated
emission at an inter band transition under conditions of a
high carrier density in the conduction band.
• While for other lasers, we need voltage of the order of
kV, in these lasers, a simple pencil battery can be used as
the voltage source. For example, in case of GaAs, the
band-gap energy is 1.434 eV which corresponds to
wavelength of 873 nm. Hence, pencil battery can serve
the purpose of a voltage source in this case.
28. APPLICATIONS OF LASER
In science, lasers are used in many ways, including:-
A wide variety of interferometric techniques
Raman spectroscopy
Laser induced breakdown spectroscopy
Atmospheric remote sensing
Investigating nonlinear optics phenomena
Holographic techniques employing lasers also contribute to a number of measurement techniques.
Laser based lidar (LIght raDAR) technology has application in geology, seismology, remote sensing
and atmospheric physics.
Lasers have been used aboard spacecraft such as in the Cassini-Huygens mission.
In astronomy, lasers have been used to create artificial laser guide stars, used as reference objects for adaptive
optics telescopes.
29. HOLOGRAPHY
Holography is the science and practice of
making holograms. Typically, a hologram is a
photographic recording of a light field, rather than of
an image formed by a lens, and it is used to display a
fully three-dimensional image of the holographed
subject, which is seen without the aid of special
glasses or other intermediate optics. The hologram
itself is not an image and it is usually unintelligible
when viewed under diffuse ambient light. It is an
encoding of the light field as an interference pattern
of seemingly random variations in the opacity,
density, or surface profile of the photographic
medium. When suitably lit, the interference
pattern diffracts the light into a reproduction of the
original light field and the objects that were in it
appear to still be there
30. HOW HOLOGRAPHY WORKS
A beam of coherent light from a laser split into by a
semi-transparent mirror such that one beam can be
scattered by the object to the photographed and
other beam falls directly on the film. The fine speckled
pattern on the film conrtains informations regarding
both the amplitude and the phase. Thus a hologram is
ptroduced.
The nect step is the reconstruction step. The hologram
is illuminated with coherent light called reconstruction
wave, usually of the same wavelrngth as the original
beam. The hologram acts as a diffraction grating
producing two sets of diffracted beam. One set forms
of real image while other forms a 3D virtual image.
31. APPLICATIONS IN MEDICINE
Medical areas that employ lasers include:
angioplasty
cancer diagnosis
cancer treatment
cosmetic dermatology such as scar revision, skin resurfacing, laser hair removal, tattoo
removal.
dermatology
medical imaging
microscopy
ophthalmology (includes Lasik and laser photocoagulation)
optical coherence tomography
plastic surgery, in laser liposuction