The document discusses key concepts related to laser emission and operation, including:
1. Stimulated emission cross section is a constant that determines the relationship between gain and stored energy in a laser medium. It depends on emission wavelength.
2. Homogeneous and inhomogeneous broadening contribute to the linewidth of laser emission.
3. Threshold requirements refer to the gain needed for a laser beam to reach saturation intensity after passing through an amplifier multiple times with mirrors.
4. Resonator stability depends on mirror curvature, with stable resonators keeping light near the axis and unstable resonators producing doughnut-shaped output beams.
5. Pumping techniques include direct, optical, and particle pumping to excite the
Basic operating principle and instrumentation of photo-luminescence technique. Brief description about interpretation of a photo-luminescence spectrum. Applications, advantages and disadvantages of photo-luminescence.
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
Interference is the superposition of two or more waves producing a resultant disturbance that is the sum of the overlapping wave contribution.
For comments please contact me at solo.hermelin@gmail.com.
A few Figures were not downloaded. I recommend to see the presentation on my website in Optics folder.
For more presentations on different subjects visit my website at http://www.solohermelin.com.
This article discusses the principle of interferometry. The definition of the term along with its applications are stated in this article. Five most common type of interferometers viz. Michelson Interferometer, Mach-Zahnder Interferometer, Fabry Perot Interferometer, Sagnac Interferometer and Fiber Interferometer are discussed in detial in this article.
Light waves superimpose each other and the redistribution of energy due to this can be observed in terms of well defined patterns of maxima and minima. Wherein, maxima refers to more energy and minima refers to less energy. Diffraction can also be called as interference in secondary wavelets.
Basic operating principle and instrumentation of photo-luminescence technique. Brief description about interpretation of a photo-luminescence spectrum. Applications, advantages and disadvantages of photo-luminescence.
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
Interference is the superposition of two or more waves producing a resultant disturbance that is the sum of the overlapping wave contribution.
For comments please contact me at solo.hermelin@gmail.com.
A few Figures were not downloaded. I recommend to see the presentation on my website in Optics folder.
For more presentations on different subjects visit my website at http://www.solohermelin.com.
This article discusses the principle of interferometry. The definition of the term along with its applications are stated in this article. Five most common type of interferometers viz. Michelson Interferometer, Mach-Zahnder Interferometer, Fabry Perot Interferometer, Sagnac Interferometer and Fiber Interferometer are discussed in detial in this article.
Light waves superimpose each other and the redistribution of energy due to this can be observed in terms of well defined patterns of maxima and minima. Wherein, maxima refers to more energy and minima refers to less energy. Diffraction can also be called as interference in secondary wavelets.
Overview of safe use of Class 3B and Class 4 lasers. Topics include: Introduction, Hazards (Biological and Non-Beam), Engineering Controls, Administrative Controls, Work Practices, and Personal Protective Equipment (PPE).
Presentation on laser for Physics B.Sc. students by Dr. P D Shirbhate assistant Professor, Department of Physics G S Gawande college, Umarkhed Dist Yavatmal.
Infrared spectroscopy is technique to identify the functional group of the molecule.
In Infrared spectroscopy there are two main region finger print region and functional group region. Most of the molecules identifies In the finger print region due to that it is complex region.
Now we will see the
principle of IR spectroscopy:
IR spectroscopy is vibrational energy level changes when IR radiation passes through the material.
This paper deals with the Internal quantum efficiency of ITO, CdTe, ZnO/a-Si, SnS/Si, CdS /CIGS, FTO/CZTS based of material photodiode with a ITO/CdTe, ZnO/a-Si, SnS/Si, CdS /CIGS, FTO/CZTS heterojunction structure. Along with information on device characteristics, applications and properties, we provide a comparative device analysis between this type of photodiode and the slightly more efficient ITO/CdTe, ZnO/a-Si, SnS/Si, CdS /CIGS, FTO/CZTS heterojunction structure. We will get the clear concept of the relation between of generated current & load voltage. We hope, we will get a clear explanation about the effect of photodiode light intensity & wavelength on the solar efficiency. In this project we will analyze the Quantum efficiency of a photodiode.
Electromagnetic radiation consists of waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, light, ultraviolet, X-rays, and gamma rays. All of these waves form part of the electromagnetic spectrum.EMR is released when excited atoms or molecules return to ground state and this process is called emisssion.
EMR has both electric (E) and magnetic (H) components that propagate at right angles to each other.
Circuits for Optical Based Line of Sight Voice CommunicationjournalBEEI
We present here line of sight communication between a person and his neighbour with the help of optical signal produced by a laser torch which act as a carrier. It is therefore a wireless communication and the transmission can go up to 500 meters. We used photodiode to receive the signal at the receiver. The transmitter circuit comprises condenser microphone transistor amplifier BC547 followed by an op-amp stage built around µA741. When we give a voice signal from the mike, it converts the voice signal into the electrical signal. This electrical signal is fed to IC741 (op-amp) for amplification. The gain of the op-amp can be controlled with the help of 1-mega-ohm potentiometer. The AF output from IC is coupled to the base of a class B amplifier which, in turn, modulates the signal. The transmitter uses 5V power supply. However, the 3-volt laser torch (after removal of its battery) can be directly connected to the circuit-with the body of the torch connected to the class B. The photodiode converts the optical signal into electrical signal and again this signal is amplified using IC741 and a combination of class B push pull amplifiers. The receiver circuit uses an NPN photodiode as the light sensor that is followed by a two-stage transistor preamplifier and IC741 based audio Power amplifier. The receiver does not need any complicated alignment. Just keep the photodiode oriented towards the remote transmitter’s laser point and adjust the volume control for a clear sound. The sensor must not directly face the sun.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
In this book, we use conservation of energy techniques on a fluid element to derive the Modified Bernoulli equation of flow with viscous or friction effects. We derive the general equation of flow/ velocity and then from this we derive the Pouiselle flow equation, the transition flow equation and the turbulent flow equation. In the situations where there are no viscous effects , the equation reduces to the Bernoulli equation. From experimental results, we are able to include other terms in the Bernoulli equation. We also look at cases where pressure gradients exist. We use the Modified Bernoulli equation to derive equations of flow rate for pipes of different cross sectional areas connected together. We also extend our techniques of energy conservation to a sphere falling in a viscous medium under the effect of gravity. We demonstrate Stokes equation of terminal velocity and turbulent flow equation. We look at a way of calculating the time taken for a body to fall in a viscous medium. We also look at the general equation of terminal velocity.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
2. Emission Cross Section
Definition: material parameters for quantifying the likelihood or rate
of optical transition event
Stimulated Emission Cross Section
It is a constant for a specific laser transition in a specific gain
medium
It is strongly dependent on the emission wavelength
Is essential for calculations of the expected performance because
it determines the relationship between the gain and the energy
stored
Homogeneous Broadening
æ
1
( ) ÷ ÷ø
H
ul n
s n 2
Inhomogeneous Broadening
ö
ç çè
= ul ul
H
D
o
A
n
l
p
2
4 2
ö
1/ 2 2 ln 2
æ
1
= æ D
ö çè
( ) ÷ ÷ø
ç çè
D
D
ul n
s n 2
÷ø
ul ul
o
A
n
l
p p
4
Linewidth of emission
3. Threshold Requirement
Definition
The necessary requirements for the beam to grow to
the point at which it reaches the saturation intensity Isat
The saturation intensity, Isat is arbitrarily defined as the
intensity at which the stimulated rate downward equals
the normal radiative decay rate,
I c
ul ( ) u
sat B n
n t
=
5. Threshold Requirement
Laser With No Mirror
The beam would meet the threshold gain requirement if,
= ( )D @ 12 ± 5 th sat ul ul sat g L s n N L
This is to ensure that the beam can develop a well defined
direction before Isat is reached
It is shown that,
2
ö
æ
e th sat L
16 ÷ ÷ø
ç çè
g L sat
=
a
d
Diameter of amplifier
Threshold gain
Laser beam divergence
6. Threshold Requirement
Laser With One Mirror
Adding a mirror can be thought of as adding a second
amplifier
Assuming that the beam just reaches Isat after two passes
through the amplifier, the gain medium would meet the
threshold gain requirement if,
g L = g (2L) = g L = ( )DN (2L) @ 12 ± 5 th sat th th eff ul ul s n
oThe beam is narrower, as it emerges from the end of the
amplifier
7. Threshold Requirement
Laser With Two Mirrors
Placing a mirror at each end of the amplifier effectively
adds an infinite series of amplifiers behind the original
amplifier
A slight amount of light is allowed to leak out the end
by using a mirror with 99.9% reflectivity
Two factors determine if a two-mirror laser can reach Isat
1. Net gain per trip
2. Sufficient gain duration
The beam emerges with a very narrow angular
divergence
8. Threshold Requirement
Net Gain per Round Trip
The minimum round-trip steady-state
requirement for the threshold of lasing is
that the gain exactly equal the loss,
The solution for the threshold gain is then,
10. Resonator Stability
Stable Resonators
The curvatures of the mirrors keep the light
concentrated near the axis of the resonator
The only way light can escape from the resonator
is to go through one of the mirrors
11. Resonator Stability
Unstable Resonators
The light rays continue to move away resonator axis
until eventually they miss convex mirror altogether
The output beam from this resonator doughnut-like
shape with a hole in the middle
The advantage is that they usually produce larger
beam volume inside the gain medium
13. Pumping Techniques
Direct Pumping
The excitation flux is sent directly to the upper laser
level u from a source or target state j, in which the
source state is the highly populated ground state 0
of the laser species
14. Pumping Techniques
Optical Pumping
Often used for solid-state and
organic dye lasers
Particle Pumping
Generally used for gas lasers and
also semiconductor lasers
15. Pumping Techniques
Direct Pumping
Disadvantages
Several effects can prevent direct pumping from being an effective
excitation process for many potential lasers. These effects are listed
as follows.
1. There may be no efficient direct route from the ground state 0 to
the laser state u. For optical pumping, that would mean that the B0u
associated with pump absorption is too small to produce enough gain;
for particle pumping, it would mean that the electron collisional
excitation cross section σ0u is too small.
2. There may be a good direct route from 0 to u, but there may also
be a better route from 0 to l (the lower laser level) by the same
process. In this case Γ0l/Γ0u may be too large to allow an inversion.
3. Even though there may be a good probability for excitation - via
absorption either of the pump light associated with B0u for optical
excitation or of σ0u
e for electron excitation - there may not be a good
source of pumping flux available. That is, there may be insufficient
intensity, I for optical pumping, or insufficient density Np (or electron
density ne) for particle pumping, at the specific energies necessary for
pumping population from level 0 to level u.
16. Pumping Techniques
Indirect Pumping
Indirect pumping processes all involve an intermediate level
q and can be considered in three general categories as
diagrammed in the figure below: transfer from below,
transfer across, and transfer from above.
17. Cavity Modes
Longitudinal Laser Cavity Modes
We have seen that one or more longitudinal laser mode
frequencies can occur when a two-mirror cavity is placed
around the laser gain medium and sufficient time
(typically 10 ns to 1 μs) is allowed for such modes to
develop. The total number of modes present is determined
by the separation d between the mirrors, as well as by the
laser bandwidth and type of broadening (homogeneous or
inhomogeneous) that is present. The actual laser mode
frequencies can be obtained by,
m c
2
ö çè
÷ø
= æ
nd
n
for lasers in which the index of refraction n is the same
throughout the pathway of the laser beam within the optical
cavity, as shown in the figure on the next slide.
Remember that m is a positive integer so as to satisfy the
standing-wave conditions of the Fabry-Perot resonator.
18. Cavity Modes
Longitudinal Laser Cavity Modes
This expression is valid for almost all gas lasers, as well as
for solid-state and dye lasers in which the mirrors are
placed immediately at the ends of the gain medium. If a
laser has a space of length d - L between the gain medium
and the mirrors, and if that cavity space has a different
value for the index of refraction nc than the index nL of the
laser gain medium, then a specific laser mode frequency
associated with a mode number m can be expressed as,
ö
ù
1
[ ] ÷ ÷ø
æ
ç çè
úû
é
êë
- +
=
n d L n L
m c
c L
2
n