1) The document discusses semiconductor lasers, including the difference between LEDs and lasers, types of semiconductors, requirements for laser generation, and classifications of semiconductor lasers.
2) It describes key characteristics of semiconductor lasers such as their active medium, pumping method, and power output.
3) Important applications of semiconductor lasers are also highlighted, including optical fiber communications, optical storage, printers, and sensors.
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
Introduction to semiconductor lasers, and its working. construction of semiconductor laser, Ga As laser, and construction, achievement of population inversion, pumping.
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
Introduction to semiconductor lasers, and its working. construction of semiconductor laser, Ga As laser, and construction, achievement of population inversion, pumping.
Laser, Pumping schemes, types of lasers and applicationsPraveen Vaidya
The document gives good insite into the different pumping schemes, different types of lasers and Applications like Holographys, laser cutting and Laser Beam Welding.
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
Laser, Pumping schemes, types of lasers and applicationsPraveen Vaidya
The document gives good insite into the different pumping schemes, different types of lasers and Applications like Holographys, laser cutting and Laser Beam Welding.
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) By active media
Solid state laser - crystal, or glass, doped with impurities, e.g. ruby laser, Ti:sapphire laser, semiconductor laser.
Gas laser - e.g. He-Ne laser, Ar+ laser, CO2 laser, N2 laser, HCN laser.
Dye laser - active medium: dye molecules in liquid solvent (sometimes in solids also).
(B) By mode of operation
CW
Pulsed
(C) By pumping and laser levels
3-level laser
4-level laser
LDR-experimentation.pdfpg. 1 COVENTRY UNIVERSITY .docxDIPESH30
LDR-experimentation.pdf
pg. 1
COVENTRY UNIVERSITY
Faculty Of Engineering & Computing
AAEE
Light Depended Resistors (LDRs)
Introduction
The light dependent resistor, LDR, is known by many other names such as photoresistor,
photoconductor, photoconductive cell, or simply the photocell. These devices were discovered by an
English electrical engineer Willoughby Smith back in 1873. Smith’s main line of work in 1848 was the
laying of underwater telegraph cables. He developed a method of testing an underwater cable as it
was being laid. One of the insulation materials used for the cable was selenium. Upon investigation
of the properties of the selenium insulator he discovered that the conductivity properties of the
material were affected by light. He published his findings in 1873.
Since then many variants of photoconductive devices have been made. Other LDRs have been made
using materials including cadmium sulphide, lead sulphide, and the more commonly used
semiconductor materials including germanium, silicon and gallium arsenide.
The most popular material used in making LDRs is cadmium sulphide (CdS).
The LDR finds many uses as a low cost photo sensitive element and was used for many years in
photographic light meters as well as in other applications such as lighting controls for street lamps
etc.
Basic structure of an LDR
There are many ways in which light dependent resistors can be manufactured. Essentially the LDR
consists of a resistive material sensitive to light. The photo resistive element comprises section of the
material with contacts at either end. Although many of the materials used for light dependent
resistors are semiconductors, when used as a photo resistor, they are used only as a resistive and
they are purely passive.
A typical structure for a light dependent or photo resistor uses an active semiconductor layer that is
deposited on an insulating substrate. The semiconductor is normally lightly doped to enable it to have
the required level of conductivity. Contacts are then placed either side of the exposed area.
Fig 1 (a,b,c) Close-Up of an LDR (a) Cadmium sulphate (b) and LDR symbol (c)
(a)
(b)
(c)
pg. 2
In many instances the area between the contacts is in the form of a zig zag, or interdigital pattern.
This maximises the exposed area and by keeping the distance between the contacts small it enhances
the gain (see Fig.1 (a).
Although other devices such as photodiodes or photo-transistors can also be used for light sensing
applications, LDRs are a particularly convenient electronic component to use. They provide large
change in resistance for changes in light level. They are of comparatively speaking of a lower cost as
compared to other light responding devices.
How an LDR works
It is relatively easy to understand the basics of how an LDR works without delving into complicated
explanations. It is first necessary to understand that an electrical ...
It's a Basic concept of Laser on the basis of bandgap. I tried to explain on the easiest way the semiconductor and then i gave the view on Islamic perspective about Laser concept.
This presentation is about Optical detector (APD) of a specific commercial model and what does it do with addition to Laser Diode and it’s commercial use also from a specific model
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
1. Submitted by –
ADITYA GHOSH
ARGHAYA GOSWAMI
DEBOJYOTI MUKHERJEE
PRITAM SARDAR
PROHLAD MONDAL
Department of Electronics & Communication
Engineering(6th semester)
Swami Vivekananda Institute of Science &
SEMICONDUCTORLASERPRINCIPLE
2. Content
Introduction
Difference between LED and Laser
Types of Semiconductors
Requirement of Laser
Generation of Laser
Classification of Semiconductor Laser
Characteristics
Non Semiconductor Laser
Main application
Advantage of Semiconductor
Disadvantage of Semiconductor
Conclusion
3. Introduction
In laser, light amplification is achieved via
stimulated emission.
Stimulated emission had been proposed by Albert
Einstein in 1915
Fig1:Laser
4. Difference between LED and Laser
Fig 2: Wavelength of LED and Laser
LED Laser
Principle Spontaneous Emission (Random)
Photon Emission
Stimulated Emission
Coherence Incoherent Coherent
SpectralWidth/LineWidth 50nm Less than 5nm
Directionality Not directional Highly directional
Output Power Low High
6. Intrinsic & Extrinsic Semiconductors
Intrinsic semiconductor : A perfect
material with no impurities.
Extrinsic semiconductor : donor or
acceptor type semiconductors.
Majority carriers: electrons in n-type or
holes in p-type.
Minority carriers: holes in n-type or
electrons in p-type.
The operation of semiconductor devices is
essentially based on the injection and
extraction of minority carriers.
2
inpn
9. Requirement of Laser
Conditions required:
1. Population inversion- the number of electrons in CB is greater
than the number of electrons in VB
2. Emission
3. Optical resonator or Fabry-Perot resonator
Spontaneous
emission
Stimulated emission
10. Population Inversion
Fig 6: thermal equilibrium condition for
degenerate semiconductor (without
biasing)
Fig 7: Population inversion occurs with
biasing
12. Optical Resonator
Mostly used the structure of Fabry-Perot resonator
Used:
i) to increase the density of photon in active region
ii) to amplify the medium radiation
Fig 10:optical resonator cavity
Fig 11:power with phase shift
15. Homojunction Semiconductor Laser
Homojunction diode lasers are those in which P end and N end of the diode are made of
the same semiconductor material.
Example : Ga As laser
They use Direct Band Gap
Semi- conductor material.
P-N Junction act as the active
medium.
The crystal is cut at a thickness of
0.5 mm
Applied voltage is given through
metal contacts on both surfaces of
the diode.
Pulse beam of laser of 8400 Å is
produced
Fig13: Diagram of Homojunction
Semiconductor Laser
16. Energy Level Diagram : Homojunction
Fig14: Energy level Diagram of Homojunction
Semiconductor Laser
17. Heterojunction Semiconductor Laser
Heterojunction Semiconductor lasers are those in which P end is made of one type
of semiconductor material and the N end is made of another type of semiconductor
material
Example : GaAlAs diode laser
Use Direct Band gap
Semiconductor
Consist of five layers namely
GaAs – p type
GaAlAs – p type
GaAs – p type (Active Medium)
GaAIAs – n type
GaAs – n type
Fig15: Diagram of Heterojunction
Semiconductor Laser
18. Energy Level Diagram : Heterojunction
Fig 16: Energy level Diagram of
Heterojunction Semiconductor Laser
19. Characteristics
1) Type: It is a solid state semiconductor laser.
2) Active medium: A PN junction diode made from
single crystal of gallium arsenide is used as an
active medium.
3) Pumping method: The direct conversion
method is used for pumping action
4) Power output: The power output from this laser
is 1mW.
5) Nature of output: The nature of output is
continuous wave or pulsed output.
22. Main applications
Optical fiber communications
Optical storage
No diode laser
= No internet!
Diode lasers are also widely used in printers,
scanners, sensors, pumping of solid-state
lasers, etc.
The diode laser in a computer mouse costs
about 10 US cents .
23. Laser Range Finder
The laser range finder works on the principle of a radar
& use to knock down an enemy tank.
23
Fig 19: working diagram of Laser Range Finder
24. Underwater Laser
Lasers can also be used as a source of underwater
transmission. At present, the submarines have to
rely on a sonar to find the enemy crafts and to
avoid the underwater objects.
24
Fig 19: working diagram of Underwater Laser
25. Advantages of semiconductor laser
Smaller size
Semiconductor laser are economical in
cost.
Its construction is simple.
It has high efficiency.
low power consumption.
26. Disadvantages of semiconductor laser
Due to relatively low power production, these
lasers not suited to typical laser applications
The temperature affects greatly the output of
the laser
Beam divergence is much greater as compared
to all other lasers
Cooling system required in some cases
27. Conclusion
Semiconductor laser have been around for
about forty years now, but their possible uses
continue to grow each day. We are at the new
dawn of the millennium, and Semiconductor
Laser will help bring about a new revolution
in many fields of science; the new optical
solution revolution!