-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy path22_Laser.html
116 lines (90 loc) · 13.8 KB
/
22_Laser.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
<html>
<head>
<p class="head">Laser</p>
<link rel="stylesheet" type="text/css" href="exampleStyle.css"/>
<style>
ul.b {
list-style-type: square;
}
ol.c {
list-style-type: upper-roman;
}
</style>
<hr>
</head>
<body>
<p><a class="def">Laser</a> is an optical device that produces the high-intensity narrow beam of <a class="black" href="https://cvertan.github.io/physics4dh.github.io/1_Light.html" target="frameterms">light</a>. The word <a class="def">LASER</a> is an acronym for ‘<a class="def">L</a>ight <a class="def">A</a>mplification by the <a class="def">S</a>timulated <a class="def">E</a>mission of <a class="def">R</a>adiation’. </p>
<p>Many different types of lasers have been developed, with highly varied characteristics. For now, lasers generate <a class="black" href="https://cvertan.github.io/physics4dh.github.io/10_infrared%20light.html" target="frameterms">infrared</a>, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/18_visible_light.html" target="frameterms">visible</a>, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/11_ultraviolet.html" target="frameterms">ultraviolet light</a>, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/21_X-ray.html" target="frameterms">X-rays</a> and <a class="black" href="https://cvertan.github.io/physics4dh.github.io/24_gamma.html" target="frameterms">gamma-rays</a>. All devices operating at <a class="black" href="https://cvertan.github.io/physics4dh.github.io/16_Radio_waves.html" target="frameterms">microwave</a> or lower <a class="black" href="https://cvertan.github.io/physics4dh.github.io/16_Radio_waves.html" target="frameterms">radio</a> <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">frequencies</a> are called <a class="def">masers</a>. The word <a class="def">MASER</a> is an acronym for ‘<a class="def">M</a>icrowave <a class="def">A</a>mplification by <a class="def">S</a>timulated <a class="def">E</a>mission of <a class="def">R</a>adiation’. </p>
<iframe width="400" height="400"
src="https://www.youtube.com/embed/sqBnG2zXBWE?autoplay=1&mute=1">
</iframe>
<div id="Prlight">
<p class="thema">Properties of Laser Light</p>
<p>Laser <a class="black" href="https://cvertan.github.io/physics4dh.github.io/1_Light.html" target="frameterms">light</a> has extra-ordinary properties which are not present in the conventional light from other sources: </p>
<ol class="c">
<li><b>Coherence</b> means all <a class="black" href="https://cvertan.github.io/physics4dh.github.io/2_Photon.html" target="frameterms">waves</a> in the beam are of the same <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">frequency</a> and waveform. This allows to produce, for example, ultrashort pulses of light with durations as short as a <a class="black" href="https://cvertan.github.io/physics4dh.github.io/30_Units.html" target="frameterms">femtosecond</a> (fs).</li>
<li><b>High directionality</b> means beam can stay narrow travel extremely long distances having a very low divergence to concentrate their power at a great distance in a specific direction. The laser beam is <a class="def">collimated</a>, that means all <a class="black" href="https://cvertan.github.io/physics4dh.github.io/2_Photon.html" target="frameterms">photons</a> are travelling parallel to each other in the same direction. In an ordinary <a class="black" href="https://cvertan.github.io/physics4dh.github.io/1_Light.html" target="frameterms">light source</a>, the light spreads out uniformly in all directions.</li>
<li><b>Monochromaticity</b> means the <a class="black" href="https://cvertan.github.io/physics4dh.github.io/19_Radiation.html" target="frameterms">radiation</a> is single <a class="black" href="https://cvertan.github.io/physics4dh.github.io/4_Colors%20of%20light.html" target="frameterms">color</a> (or single <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">wavelength</a>).</li>
<li><b>High intensity</b> means laser light is focused to a tiny spot, achieving a very high power received by a surface per unit area. </li>
</ol>
<p>So, lasers produce highly directional, monochromatic, coherent and collimated light beam. That is why laser differ from ordinary light sources like sun and lamp. </p>
</div>
<div id="AppL">
<p class="thema">Application of Lasers</p>
<p>Lasers are everywhere around us. Surgeons use them for eye surgery and cancer treatments. Manufacturers use them for material processing to cut, mark, weld, clean, and texture various types of materials. Some people need them for tattoo or hair removal, and everyone has seen laser light shows during music concerts. [<a class="ref" href=bibliography.html#laserax>laserax</a>] </p>
<p>Lasers are used in barcode scanners, laser pointers, printers, military, security, various branches of science, air pollution measurements, holography, material processing, cutting in industry and surgery. </p>
<p>Laser scanning, in combination with other digital documentation techniques and traditional survey, provides an extremely useful way to document the spatial characteristics of monuments, buildings, or landscapes of outstanding universal value [<a class="ref" href=bibliography.html#3D_2006>3D_2006</a>] for Cultural Heritage. </p>
<p><a class="def">LiDAR</a> is a popular remote sensing method to examine the surface of the Earth. LiDAR is an acronym of ‘<a class="def">L</a>aser <a class="def">I</a>maging, <a class="def">D</a>etection and <a class="def">R</a>anging’. LiDAR uses a pulsed laser to calculate an object’s variable distances from the earth surface. These light pulses — put together with the information collected by the airborne system — generate accurate 3D information about the earth surface and the target object [<a class="ref" href=bibliography.html#geospatialworld>geospatialworld</a>]. </p>
<p>Masers are widely used in radio telescopes and deep-space spacecraft communication ground stations. </p>
<div class="gallery">
<img src="Figures/Laser_app.jpg" width="400" height="100">
<div class="desc">Applications of lasers © <a href="https://www.electronicsforu.com/technology-trends/learn-electronics/lasers-multidisciplinary-applications" target="_blank">https://www.electronicsforu.com/</a> </div>
</div>
</div>
<div id="TypeL">
<p class="thema">Types of Lasers</p>
<p>Based on their <a class="black" href=https://cvertan.github.io/physics4dh.github.io/22_Laser.html#PrL target="frameterms">gain medium</a>, lasers are classified into five main types: </p>
<ol class="c">
<li><a class="def">Gas Lasers</a>: In gas lasers, the laser medium is in the gaseous state. Examples of gas lasers include carbon dioxide (CO<a class="sub">2</a>) lasers, helium–neon lasers, argon lasers, krypton lasers, and excimer lasers. An electric current is discharged through a gas inside the laser medium to produce laser light.</li>
<li><a class="def">Solid-State Lasers</a>. Solid-state lasers use a solid mixed with a rare earth element as their source of optical gain. The mixed element is typically neodymium, chromium, erbium, thulium, or ytterbium. The most known solid-state laser is the ruby laser (Nd:YAG, neodymium-doped yttrium aluminum garnet), since it is the first laser ever constructed. In solid-state lasers, light energy is used as pumping source. Light sources such as flash lamps, arc lamps, or laser diodes are used to achieve pumping.</li>
<li><a class="def">Fiber Lasers</a>. It is a special type of solid-state laser that is a category of its own. In fiber lasers, the gain medium is an optical fiber (silica glass) mixed with a rare-earth element. Examples of fiber lasers used for these applications include ytterbium and erbium-doped fiber lasers.</li>
<li><a class="def">Liquid Lasers (Dye Lasers)</a>. A Liquid lasers use an organic dye in liquid form as their gain medium. They are also known as dye lasers and are used in laser medicine, spectroscopy, birthmark removal, and isotope separation.
One of the advantages of dye lasers is that they can generate a much wider range of wavelengths, making them good candidates to be tunable lasers, meaning that the wavelength can be controlled while in operation.
</li>
<li><a class="def">Semiconductor Lasers (Laser Diodes)</a> can be classified as solid-state lasers since their gain medium is solid. However, they are in a category of their own because of their positively-negatively (PN) charged junction similar to regular diodes. Laser diodes have an intrinsic layer at the PN junction made of materials that create spontaneous emission. The intrinsic layer is polished so that the generated photons are amplified, ultimately converting the electric current into laser light. So, electrical energy is used as the pump source.</li>
</ol>
<p>Additionally, these five types of lasers can be divided into subcategories based on their mode of operation: <a class="def">continuous-wave lasers</a> and <a class="def">pulsed lasers</a>. Continuous wave (CW) simply means that the laser remains on continuously until stopped. A pulsed laser produces a series of pulses at a certain pulse duration and frequency. </p>
<div class="gallery">
<img src="Figures/Pulse.jpg" width="400" height="100">
<div class="desc">Pulsed lasers emit bursts of light, spaced in time. There is no emission between pulses. CW lasers emit light whose optical power is approximately constant with time © [<a class="ref" href=bibliography.html#geospatialworld>Thorlabs</a>] </div>
</div>
<p>There are also multiple <b>types of pulsed lasers</b>, depending on the pulse duration. For example, millisecond lasers are lasers emitting optical pulses with millisecond durations. There are also microsecond, nanosecond, picosecond and femtosecond lasers. </p>
<p>Types of lasers are constantly evolving. </p>
</div>
<div id="PrL">
<p class="thema">Principles of Lasers</p>
<p>The main processes involved in the working of laser are the <a class="black" href="https://cvertan.github.io/physics4dh.github.io/7_Absorption.html" target="frameterms">absorption</a> of radiation, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/8_Emission.html" target="frameterms">spontaneous emission</a> and <a class="black" href="https://cvertan.github.io/physics4dh.github.io/8_Emission.html" target="frameterms">stimulated emission</a>. In laser operation, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/5_Atom.html" target="frameterms">atoms</a> are stimulated to emit <a class="black" href="https://cvertan.github.io/physics4dh.github.io/1_Light.html" target="frameterms">light</a> at particular <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">wavelengths</a> and that light is amplified. </p>
<p>Lasers are comprised of three main components [<a class="ref" href=bibliography.html#laserax>laserax</a>, <a class="ref" href=bibliography.html#plasticsurgery>plasticsurgery</a>]: </p>
<ol class="c">
<li>The <a class="def">energy source</a> (also referred to as a pump source) pumps light into a gain medium. It varies according to the type of laser and could be a laser diode, an electrical discharge, a chemical reaction, a flash lamp, or even another laser.</li>
<li>The <a class="def">gain medium</a> (also referred to as an active medium) emits light of a specific wavelength when excited by light from energy source. This component determines the wavelength (and therefore the color) and frequency of the light emitted and is said to be the source of optical gain. Lasers are typically named and classified after their gain medium.</li>
<li>The <a class="def">resonator</a> (also referred to as an optical cavity) amplifies the optical gain through mirrors that surround the gain medium. One of the mirrors is fully reflective and the other is partially reflective. The mirrors reflect the light and ensure many passes of the laser light beam through the medium, allowing repeated amplification. The amplified light then escapes the partially reflective mirror as a output beam of light.</li>
</ol>
<div class="gallery">
<img src="Figures/Laser_basic.jpg" width="400" height="100">
<div class="desc">The basic components of a laser © <a href="https://plasticsurgerykey.com/the-science-behind-lasers-how-the-physical-properties-of-lasers-affect-the-skin/#_Ref407804948">https://www.plasticsurgerykey.com/</a> </div>
<p class="important">How does a laser work? <a href="https://www.youtube.com/watch?v=_JOchLyNO_w">www.youtube.com</a>, <a href="https://www.youtube.com/watch?v=DA7a_v96Jsw">www.youtube.com</a>, <a href="https://www.youtube.com/watch?v=WgzynezPiyc">www.youtube.com</a>,
<a href="https://physics-and-radio-electronics.com/physics/laser/laser-populationinversion.html" target="_blank">https://physics-and-radio-electronics.com/</a></p>
</div>
</div>
<p class="acknow">Acknowledgements:
[<a class="ref" href=bibliography.html#Svelto_2010>Svelto_2010</a>],
[<a class="ref" href=bibliography.html#ph-r-el>ph-r-el</a>],
[<a class="ref" href=bibliography.html#wiki>wiki</a>],
[<a class="ref" href=bibliography.html#3D_2006>3D_2006</a>],
[<a class="ref" href=bibliography.html#plasticsurgery>plasticsurgery</a>],
[<a class="ref" href=bibliography.html#amadaweld>amadaweld</a>],
[<a class="ref" href=bibliography.html#laserax>laserax</a>],
[<a class="ref" href=bibliography.html#messe-stuttgart>messe-stuttgart</a>].</p>
</body>
</html>