Types of Laser Outputs 1) Continuous-Wave (CW) Continuous with respect to time Higher level must be long-lived relative to lower level, else the laser is self-terminating. 2) Pulsed (not continuous) Higher peak powers (kW to > MW) Nanosecond pulse widths are typcial
Types of Laser Outputs 3) Q-Switched “ Giant pulse laser” Spoil the cavity resonance so that the lasing threshold is greatly exceeded. Then let it out all at once. Hundreds of MW/pulse achieved
Types of Laser Outputs 4) Mode-Locked Picosecond or less laser pulses Force all longitudinal modes to be coherent Generates short (ps or less) and intense (MW) pulses
Varieties of Lasers Laser type Wavelengths (nm) Power Output Helium–neon 633,1152 0.1–50 mW CW Argon–ion 351–529 several 5 mW–25 W CW Helium–cadmium 325, 442 1–50 mW CW Dye (Ar pump) 400–1000 to 5 W CW, tunable Yd:YAG 1064 0.1–500 W (ave) Pulsed Nd:YAG 1064 0.5–1000 W CW CO 2 10 600 1–100 W 3–7 CW GaAlAs 750–900 1–100 mW CW InGaAsP 1100–1600 1–100 mW CW Ti:sapphire 700–1100 0.1–1 W CW, tunable (Ar pumped)
What You Should Know About Lasers? What does “LASER” stand for? What does population inversion mean? Why is it required for lasing? Be able to draw the energy diagram for a 3 and 4 level laser. What are the characteristics of laser light? What are the differences between “CW” and “pulsed” lasers (operational modes)? What are the general types of lasers (e.g., gas, excimer, etc)? What is a transverse mode?
06/05/09 LASER TECHNOLOGY Become Enlightened ( 14 )
06/05/09 Guiding Light Your guide to navigating through the wonders of laser technology….
II. History of the Laser III. How the Laser Works IV. Laser Activity V. Implications of the Technology
VI. Conclusions VII. Resources
Introduction In the Beginning There Was Light Lasers Industrial Cutting Tools CD Players DVD Players Dental Drills Lasik eye surgery Tattoo Removal Surgical Cutting Tool Printers And More…
06/05/09 Introduction In the Beginning There Was Light The laser is an example of a technology that was developed long before its applications were ever imagined. Forty-four years ago Arthur Schawlow and Charles Townes could have had no possible way of knowing the profound effects this technology would have on society or the widespread applications it would have in a variety of industries. The impact of this invention is usually not realized because many consider laser technology a futuristic idea depicted in Hollywood movies or science fiction books. Most people don’t recognize that laser technology is already present as an integral part of our daily lives, allowing us to listen to CD’s, watch DVD’s, and play computer games. Additionally, lasers are becoming increasingly visible in medicine in ophthalmologic, cosmetic, and general surgery. This presentation focuses on giving the viewer better insight to the impacts this technology has had on society as a whole as well as an understanding of the functions lasers play in our daily lives.
06/05/09 Flashes of Brilliance The History of the Laser “ A splendid light has dawned on me” – Albert Einstein In 1917 Einstein published ideas on stimulated emission of radiation. These ideas laid the basic foundation for the invention of the laser years later. While investigating what is now known as the photo-electric effect, Einstein noted a statistical tendency which caused photons (particles of light), to want to move together. In addition, emitted photons displayed a sort of snowball effect, once emitted, photons stimulated other atoms to emit more photons. Einstein was also able to prove that these emitted photons all traveled in the same direction and with the same frequency as the original photon. ( 11 )
Flashes of Brilliance The Birth of the Maser The immediate predecessor to the laser was the maser, a device designed using the same principles that were eventually applied in creating the laser. The word “MASER” is actually an acronym which stands for: M icrowave A mplification by S timulated E mission of R adiation Critics of this lengthy and costly project adopted the following acronym M eans of A cquiring S upport for E xpensive R esearch! ! At the point in time when the laser was being invented, other researchers had no idea how widespread the applications of the laser would become. On the left the patent application for the maser is pictured. (17)
06/05/09 Flashes of Brilliance From Maser to Laser Arthur L. Schawlow Charles H. Townes The laser is credited as being invented in 1958 by Charles H. Townes and Arthur L. Schawlow. Townes coined the term “laser” with help from his students. The main differentiating factor between the two devices is that the laser uses light waves as opposed to the microwaves utilized by the maser. Einstein’s Theories Right type of atoms Reflecting Mirrors Laser = + + Click on this picture to see how a laser works Back to Guiding Light (12)
Shedding Some Light How the Laser Works Flash Tube Partially Reflective Mirror Mirrored Surface Atoms The laser in it’s non-lasing state become excited The flash tube fires light at the ruby rod. The light excites the atoms. Emitted Light Some of these atoms emit photons.
06/05/09 Shedding Some Light How the Laser Works Cont. Some of these photons run in a direction parallel to the ruby's axis, so they bounce back and forth off the mirrors. As they pass through the crystal, they stimulate emission in other atoms. Monochromatic, single-phase, columnated light leaves the ruby through the half-silvered mirror -- laser light! Back to Guiding Light
06/05/09 Can You See the Light? In the picture on the next slide try to identify as many occurrences of laser technology as possible. When you are ready to see how many applications of laser technology are actually in the picture, click your mouse on the image and they will be revealed to you…
Can You See the Light? Dentists use laser drills Bad eyesight can be corrected by optical surgery using lasers CD-Audio is read by a laser Tattoo removal is done using lasers Cd-Rom discs are read by lasers Laser pointers can enhance presentations Bar codes in grocery stores are scanned by lasers Video game systems such as PlayStation 2 utilize lasers DVD players read DVD’s using lasers Airplanes are equipped with laser radar Military and Space aircraft are equipped with laser guns Laser tech. is used in printers, copiers, and scanners
06/05/09 Not to be Taken Lightly The Weighty Implications of Laser Technology C lick on the picture above to view the picture slide again The previous example was meant to exemplify how the technological explosion of the last few decades has made your average day a fact of what was once thought of as wild science-fiction. As evidenced by the previous example, there are a wide array of applications of laser technology which we encounter in our daily lives. From interactive computer games to eye-sight improving surgery, laser technology has much improved the lot of mankind. Advancing technology is an integral part of mankind’s quest for improving the quality of our existence. However, as we work to refine and develop our technologies it is equally important to be aware of both the positive and negative ways in which our lives are affected. Back to Guiding Light
06/05/09 Not to be Taken Lightly The Weighty Implications of Laser Technology Applications of Laser Technology Medical Entertainment Telecommunications Military
Video Game Systems
Click on the highlighted links to learn more about the implications of laser technology Back to Guiding Light Industry
06/05/09 Lasers & Military Ominous lights The military applications of laser technology hold perhaps the most grave implications for humanity. … The U.S.’s drive for more powerful, more accurate, and frighteningly more destructive weapons has only caused more instability within the Cold War arms control framework. Coupled with the push towards developing weapons in space, these weapons have the potential to destroy everything, and everyone in our world. None of which would be possible without Laser Technology….
Lasers & Military Ominous lights The Reagan Star-Wars era program did much to initially support laser weapons research, resulting in many of today’s military advancements. Lasers are used to drive fusion machines fueling thermonuclear explosions and used in most nuclear devices. The most potent and deadly application of laser technology is the Space Based Laser. As tensions over the growing arsenals of nations grow, arms agreements have done little to slow down the development of these technologies.
Lasers & Military Ominous lights “ The growing technological surge of some leading powers and their growing possibilities to create new-generation weapons and military hardware are creating prerequisites for a qualitatively new stage in the arms race and a dramatic change in the forms and methods of waging hostilities.” (19) These expensive weapons have only increased the disparity of wealth and power between underdeveloped nations and nations such as our own. “… Although unlikely to be challenged by a global peer competitor, the United States will continue to be challenged regionally. The globalization of the world economy will also continue, with a widening between “haves” and “have-nots.” (20)
Lasers & Military Ominous lights If development of these devastating applications of technology continue, the beginning of the 21 st century will be remembered as the beginning of a new arms race -- If there is anyone left to remember it…
Lasers & Military Ominous lights However, laser technology has also helped advance the U.S. military by offering new possibilities in warfare, such as: Non-Lethal Weapons
Lasers & Military Ominous lights Low energy lasers can be directed or aimed at specific targets to blind personnel or sensors either temporarily or permanently. The most advanced blinding lasers oscillate between numerous colors to make goggles and other countermeasure ineffective. Lasers can also be used to make a gun or other weapon too hot to hold. High-intensity lasers can be used in omni-directional bombs or flares which can flash-blind personnel as well as degrade sensors and night vision devices.
Lasers & Military Ominous lights Factors to consider: Is the weapon able to discriminate between the target and the civilian population? Does the weapon cause unnecessary suffering? Some “non-lethal” weapons can cause temporary or even permanent blindness.
Lasers & Military Ominous lights Some “non-lethal” weapons can cause temporary or even permanent blindness. The controversy surrounding the use of non-lethal lasers centers around whether deliberately blinding a human being causes unnecessary suffering. Scholars in countries such as Sweden rally around the declaration of St. Peterburg which authorized the incapacitation of an opponent only for the duration of the conflict. “ Although it is permitted to kill combatants under the law of war, and thus to put them permanently out of action, it is Not permitted to use methods or means of warfare exclusively designed to injure soldiers with injuries lasting not only the duration of the conflict but for the rest of their lives.” (21)
Lasers & Military Ominous lights The United States disagrees with that position, reasoning that the use of a number of conventional weapons could result in blindness. “ It is the United States’ position that lasers do not cause unnecessary suffering but are more humane because the victim is likely to suffer less injury than that caused by conventional weapons.” (21)
Lasers & Military Ominous lights Non-lethal weapons offer new possibilities in warfare, however the quality of life which is preserved during hostilities must be taken into careful consideration. Like the “perfect” weapons of mass destruction which laser technology has helped to create, non-lethal weapons are not the “perfect” war-time solution. “ Let us not hear of Generals who conquer without bloodshed. If a bloody slaughter is a horrible sight, then that is a ground for paying more respect to War, but not for making the sword we wear blunter and blunter by degrees from feelings of humanity, until some one steps in with one that is sharp and lops off the arm from our body.” -Carl von Clausewitz General Robert E. Lee emphasized another downfall to Non-lethal warfare during the Battle of Fredericksburg: “ It is well war is so terrible, or we should grow too fond of it.” If war wasn’t as awful and grotesque as it is, it’s possible that it might be taken as seriously…
06/05/09 Lasers & Military Ominou s lights Although military applications of Laser Technology have such potentially devastating implicati ons for humanity, it is easy to see that using this powerful tech nology to advance weaponry is a necessary evil. Without the na tional security that these weapons provide, our country w ould be vulnerable to outside attack. However, it is up to us t o decide whether our vision for the future is the endless quest fo r military superiority, or whether our ultimate goal is pea ce on earth. Back to Implications Menu Back to Guiding Light
Lasers & Medicine Going where no man has gone before ADVANTAGES FOR THE LASER AS A MEDICAL CUTTING TOOL Laser Surgery Reduces pain and trauma for the patient Speeds healing — thereby shortening costly hospital stays Improves the accuracy of certain surgical procedures
Lasers & Medicine Going where no man has gone before ADVANTAGES FOR THE LASER AS A MEDICAL CUTTING TOOL
Greater accuracy of incisions
Lasers can be inserted inside the body with little
risk or discomfort
Incisions can be guided by computers
The laser is extremely precise, and can be
tuned to work on a micro-level, barely visible to
the human eye
06/05/09 Lasers & Medicine Going where no man has gone before ADVANTAGES FOR THE LASER AS A MEDICAL CUTTING TOOL The precision and accuracy with which lasers can cut is so exact that it would be impossible for a human to recreate . Pictured on the right is a human hair treated by an excimer laser- the cuts are so tiny that they would not be visible to the human eye! The excimer laser is typically used to perform LASIK eye surgery . The laser as a cutting tool also has considerable industrial implications. Click here to learn more.
06/05/09 Lasers & Medicine Going where no man has gone before ADVANTAGES FOR THE LASER AS A MEDICAL CUTTING TOOL
Certain conditions which were once inoperable due to the
accuracy of incisions necessary are now possible.
Today, compact lasers can be inserted inside the body with little risk or discomfort, going places and
performing surgeries that were not humanly
Lasers guided by computers can eliminate human error
Back to Implications Menu
Lasers & Medicine Once i was Blind, Now i can See… Laser Technology’s Contributions to Ophthalmology Advances in laser technology have made substantial improvements in the field of ophthalmology. Prior to these advances the solutions for those genetically pre-disposed to bad eyesight were limited:
Glasses - which are bulky and often carry social stigma
Contacts – which often leave eyes susceptible to infection , require
daily cleaning , and cannot be worn comfortably overnight or for
extended periods of time
Lasers & Medicine Once i was Blind, Now i can See… Failing Vision Has implications of it’s own… costly rehabilitation /treatment loss of productivity migraine headaches dizziness driving restrictions dependence on eyewear impaired ability to read
Lasers & Medicine Once i was Blind, Now i can See… “ Healthy eyesight is one of the "gold standards" of good health. As seen in Figure 1 [to the left], 86% of adults are concerned about maintaining healthy eyesight, ranking above major fears like cancer and heart disease. As the population ages, more and more Americans will become concerned about their eye health. ” (8)
Lasers & Medicine Once i was Blind, Now i can See… (8) Currently, it is estimated that more than 63 million people in the U.S. are nearsighted . (8) As the “Baby Boomer” generation ages, laser technology has and will continue to increase it’s dominance as an economic force to be reckoned with. “ The increasing number of Boomers has fueled 12% annual sales growth in reading glasses over the past 10 years, with 33.3 million adults over age 40 indicating they have purchased reading glasses. Another growing area in the vision market is laser surgery. In 1996, surgeons performed 100,000 corrective eye surgeries. In 1997, that figure doubled.”
Lasers & Medicine Once i was Blind, Now i can See… costly rehabilitation /treatment loss of productivity migraine headaches dizziness driving restrictions dependence on eyewear impaired ability to read LASIK Eye Surgery Can Help! Side vision isn't blocked, as it is with glasses. No longer the problem of dirty, wet or scratched glasses. Inconvenience and discomfort of contact lenses is eliminated. More self-confidence!
Lasers & Medicine Once i was Blind, Now i can See… What is Laser Surgery? The goal in laser eye surgery is to reshape the cornea, changing the focal point of the eye. Ideally the focal point is changed so it focuses perfectly on the retina. If you are nearsighted, the image comes into focus before it hits your retina If you are farsighted, the image doesn’t come into focus before it hits your retina In a good eye the image is focused on the retina ( (5) )
06/05/09 Lasers & Medicine Once i was Blind, Now i can See… How Does Laser Surgery Work? (Picture slides & Text From (7) ) After applying anesthetizing drops, the surgeon marks the eye to indicate where the flap will be cut and then replaced. A suction ring holds the eye still and pressurizes it so it is firm enough to cut. The microkeratome slices a tiny flap in the cornea. The flap is moved out of the way, but it is still attached. The laser removes tissue to reshape the cornea. The flap is replaced on the eye. Back to Guiding Light Back to Implications Menu
06/05/09 Lasers & Industry The Cutting Edge Laser technology has taken the jewellery industry by storm… The superior cutting accuracy and precision which have contributed to it’s success as a medical tool are also highly desirable for this industry. “ Laser technology, whose strengths lie in its finesse and flexibility, allows designers to create complex geometric figures and experiment with tonal effects- indeed, different alloys can be included in the same object, which was previously impossible at the granulation level.” (4) The advantages of this system over mechanical processes are substantial:
The cuts are more precise and reduce raw material losses
Laser welding can be automated for high-precision tasks
The process is cleaner
The very high cutting speed makes it possible to produce
"haute couture" jewelry at industrial prices
Back to Guiding Light Back to Implications Menu
06/05/09 Lasers & Entertainment The Light and the dark side One of the most popular applications of laser technology, the Compact Disc Player, marked a revolution in digital video and sound technology. (Pictures from (9))
06/05/09 Lasers & Entertainment The Light and the dark side Whether you’re in your car, at your computer, or running down the street, music can enhance any atmosphere and take you away from the trials of daily life. Escaping to the movies with your home entertainment system now includes features to adapt to individual wants and needs with special features such as subtitles, commentary tracks, and sound options. Software is now more compactly portable due to increases in data storage capacity available on compact discs. Laser technology has made leaps and bounds in improving the quality of recorded video and sound. In addition the increase in accessibility and portability of information and media has helped people to learn faster and be more productive. Compact Discs appear in a variety of forms, they can hold music, videos, or even computer software. The low cost of production coupled with the durability of CD’s has contributed to their becoming the standard medium for distributing large quantities of information in a reliable package at an affordable price.
06/05/09 Lasers & Entertainment The Light and the dark side Click here to learn about How a CD Works CD’s and DVD’s
A CD holds 783 MB on a disc that is
12 cm in diameter (10)
This caters to our information-hungry generation for which knowledge equals power… Good things come in small packages!
A DVD has 7 times the capacity of
a CD (15)
If an average DVD movie were to be uncompressed it
would take at least a year to download over a normal
phone line. (15)
Special DVD features such as subtitles help bridge cultural
gaps and allow people from diverse backgrounds to enjoy
the same media.
With a DVD you can skip to your favorite parts
(saving time not rewinding or fast forwarding)
Interactive CD-Rom’s are helping kids to learn faster
in school because they can go at their own pace as
well as get extra help at home using their PC’s
The increase in memory available on CD’s has resulted in
better quality computer and video games
06/05/09 Lasers & Entertainment How a CD Works The CD Player works by using a laser beam to determine the lengths of a series of tiny ridges inside a compact disk. Inside a CD Player The music is digitally encoded in the ridge lengths which are measured by the reflected laser light. (Pictures from (10) )
Lasers & Entertainment The Light and The Dark Side On a local level, one of the most widespread applications of laser technology on college campuses today is the reading and writing of compact discs. This seemingly benign application has had weighty implications on the music industry and has raised controversy between artists and consumers about the right of the people to access media. While the ease with which digital data can be put into a disk format and then read using laser technology has made media available to a larger economic group, producers of media have been unable to control the theft and widespread distribution of electronic forms of their works. The proliferation of recordable compact discs and CD- burners has led to this application of laser technology becoming a nemesis of the Music industry. Not only can CD’s be burned directly from one CD to another, but downloaded software from the web such as Napster and Kazaa facilitate easy downloading from a vast community of users sharing media in a base of sorts.
Lasers & Entertainment The Light and The Dark Side Consequences of “Burning” Desires
Lasers & Entertainment The Light and The Dark Side
The number of units shipped from record companies
to retail outlets and special markets dipped 10.3
percent in 2001.
The dollar value of the shipments dropped from
US$14.3 billion in 2000 to $13.7 billion in 2001 .
(Recording Industry Association of America Inc.)
06/05/09 Lasers & Entertainment The Light and The Dark Side "Piracy is sometimes and mistakenly called a 'victimless crime.' It is not. The economic losses due to piracy are enormous, and they are felt throughout the music value chain. Piracy also nurtures organized crime across the world, and it stunts investment, growth and jobs." -International Federation of the Phonographic Industry Chief Executive Jay Berman “ While debate intensifies within the music industry over the degree of impact that peer-to-peer file sharing and CD burning has had on the global downturn in music sale new findings from international research firm Ipsos-Reid show that an estimated one-fifth (19%) of the American population aged 12 and over have downloaded music or MP3 files from an online file- sharing service (such as Morpheus, Napster, or Audio Galaxy). This translates into over 40 million users within the current U.S. population (according to 2000 U.S. Census figures).” (2) Back to Guiding Light Back to Implications Menu
Concluding Thoughts As we advance towards the next century, it is inevitable that laser technology will play an increasingly important role in society . . . Innovation Laser technology has already contributed to furthering the goals of humanistic scholarship Revolution New ideas and applications are changing our every-day Life as we know it… The key to managing today’s rapidly evolving technology is to constantly analyze how each advance affects us as individuals and as a society as a whole.
“ Our advancing technology, if separated from the human factor, I take to be part of the advance in the evolving quality of existence, something that gives added meaning and higher dimension to the human venture…” - Roger Sperry Neuroscientist and Nobel Laureate