The laser or, light amplification by stimulated emission of radiation to give it its full name, has come a long way since its development in the 1960's. Today laser technology is ubiquitous in our modern world with applications from medical uses, telecommunications, and even weapon systems.
In the following article, we'll take a very quick tour through the main events that led to the development of the laser and look at some future, in development, applications for lasers.
What follows is a list of selected milestones in the fascinating and exciting development of laser technology. This list is far from exhaustive and is in chronological order.
1. Max Planck Kicks it All off
The importance of the laser innovation or milestone: Max Planck, in 1900, deduced the relationship between energy and the frequency of radiation. He was the first to postulate that energy could be emitted or absorbed in discrete chunks or quanta.
This was a watershed in physics.
Year of Discovery/Development: 1900
Engineer or scientists behind the project: Max Planck
Description of Milestone: Although Planck's theory was groundbreaking in its own right it had one very important effect. Planck's insight would inspire one of the most influential scientists of our age - Albert Einstein.
Einstein would build on Planck's theory to release his paper on the photoelectric effect. He proposed that light also delivers energy in chunks, or discrete quantum particles, called photons.
The foundations had been laid for the development of lasers.
2. Einstein's Concept and Theory of Stimulated Light Emission
The importance of the laser innovation or milestone: Einstein's theory would pave the way for the eventual development of the first practical lasers.
Year of Discovery/Development: 1916-1917
Engineer or scientists behind the project: Albert Einstein
Description of Milestone: Albert first theorized about the stimulation of light emission way back in 1917. In his paper, Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation) he recorded his thoughts on this subject.
He used Planck's law of radiation to describe probability coefficients (Einstein coefficients) for absorption and spontaneous and stimulated emission of EM radiation, including light.
His theory proposed that electrons could be stimulated into emitting light of a particular wavelength. This would become the foundational principle of all lasers used today. It would take another 40 years or so before scientists were able to prove him right.
3. The Invention of Holography
The importance of the laser innovation or milestone: Research into holography was stalled until the development of lasers in the 1960's. This would stimulate, in part, the development of both technologies thereafter.
Holography is the means of producing a unique photographic image without the use of a lens. Holograms consist of a series of unrecognizable stripes and whorls that when illuminated by a coherent light source, like a laser, become a 3D representation of the original image/object.
Year of Discovery/Development: 1948
Engineer or scientists behind the project: Dennis Gabor
Description of Milestone: Dennis Gabor, a Hungarian-born scientist, received the Nobel Prize for Physics for his invention in 1971. He was attempting to improve the resolution of electron microscopes by making holograms using the electron beam and then examining that with coherent light.
At the time of discovery, it had little if any, practical use until the development of lasers in the 1960's. This would suddenly lead to an explosion in the use of holograms in the United States.
Today this explosion has led to an enormous industry that includes HUD's. museum displays, VR, medical applications and solar panel efficiency.
4. The Rise of MASER (Microwave Amplification of Stimulated Emission of Radiation)
The importance of the laser innovation or milestone: Microwave amplification by stimulated emission of radiation or MASER, was the first practical demonstration of Einstein's principles and used microwave radiation (instead of light in lasers).
Year of Discovery/Development: 1954
Engineer or scientists behind the project: Charles Hard Townes, Arthur Schawlow, James P. Gordon, Herbert J. Zeiger
Description of Milestone: MASERs are devices that produce and amplify EM radiation in the microwave part of the EM spectrum.
In 1954 Townes and his research colleagues were able to demonstrate the first MASER at Columbia University. Their Ammonia MASER would go down in history as the first device to demonstrate Einstein's prediction from 1917.
It would successfully obtain the first amplification and generation of EM radiation through stimulated emission. The MASER radiates at a wavelength of a little more than 1 cm and generates approximately 10 nW of power.
In March 1959Townes and Schawlow were awarded the patent for their invention.
MASER technology would go on to be used in to amplify radio signals and to be used as an ultra-sensitive detector.
5. The Development of the Pumping Method
The importance of the laser innovation or milestone: Modern lasers are heavily reliant on the pumping method to stimulate and amplify light sources.
It was first developed by Nikolai Basov in 1955 at the P. N. Lebedev Physical Institute in Moscow. Whilst trying to find ways of moving electrons around atoms into higher-energy states and researching oscillators he stumbled upon the concept of negative absorption that is commonly called the pumping method.
This involves transferring energy from an external source into a gain medium within the laser assembly.
Year of Discovery/Development: 1955
Engineer or scientists behind the project: Nikolai G. Basov
Description of Milestone: Basov's invention would provide the means for a continuous laser beam to be sustained. It provided a means of maintaining the required population inversion of the laser medium by 'pumping' electrons into a metastable state required to release photons.
Nikolai and Charles H. Townes were jointly awarded the 1964 Nobel Prizefor Physics for the joint work on the development of the MASER.
6. The Term Laser is Coined
The importance of the laser innovation or milestone: A Columbia University Graduate Student, Gordon Gould, writes down in his notebook the first recorded use of the term laser. He also jotted down down his ideas on the actual construction of one and has the foresight to get it notarized in a local store in the Bronx.
Not long after he leaves university to join the private research company TRG (Technical Research Group).
Year of Discovery/Development: 1957
Engineer or scientists behind the project: Gordon Gould
Description of Milestone: Gordon's notebook would be the first time the acronym Laser was used but also noted some basics concepts for building one. This notebook would become the focus of a 30-year court battle for the patent rights to the technology.
Gould discussed his ideas with ith physicist Charles Townes, who advised him to write his thoughts down and have it notarized, which he did. Gould was under the impression he should have a working model prior to applying for a patent and was beaten to it by Townes and physicist Arthur Schawlow who had filed a similar application, meaning his eventual application was rejected.
Townes and Schawlow were awarded US patent number 2,929,922 in March 1960 whilst they worked at Bell Labs for their "Optical MASER". Gould would finally win his case in 1977 to be awarded the first patent for a laser.
7. The First Practical Laser is Patented
The importance of the laser innovation or milestone: This was the first successful assembly of a complete laser device. It would be the first of many more to come.
Theodore, a physicist at Hughes Research Laboratories in Malibu, California, built the first laser using a cylinder of mand-made ruby 1 cm in diameter and 2 cm long. Each end was coated with silver to make them reflective and help them serve as a Fabry-Perot resonator.
His device used photographic flashlamps for the laser's pump source.
Year of Discovery/Development: 1960
Engineer or scientists behind the project: Theodore H. Maiman
Description of Milestone: After serving some time in the navy, Theodore earned his B.Sc. In Engineering Physics from the University of Colorado and then later earned his M.Sc. in Electrical Engineering and Ph.D. in Physics from Stanford University.
He would go on to work at the Hughes Atomic Physics Department, California as the head of its ruby MASER project. After successfully completed it in the summer of 1959 he turned his attention to the development of a laser.
After successfully building a working laser, he had his achievements published in Nature in 1960 and went on to found the Korad Corporation to develop and build high-powered laser equipment.
This company would become a market leader and in 1969 supplied their equipment was used as the lunar laser ranging equipment.
8. First Continuous-beam Laser is Developed
The importance of the laser innovation or milestone: The Helium-Neon (He-Ne) laser was the first laser to generate a continuous beam of light at 1.15 um.
This laser would find many applications in telecommunications, internet data transmission, holography, bar-code scanners, medical devices and many more.
Year of Discovery/Development: 1960
Engineer or scientists behind the project: Ali Javan, William Bennett Junior, and Donald Herriott
Description of Milestone: Whilst working at Bell Laboratories he and his colleagues William Bennet and Donald Herriott would spend two years developing the new form of laser - Ne-He.
“The first laser, the ruby laser by Ted Maiman, used optical pumping to create the population inversion necessary to achieve lasting,” Irving Herman, a Ph.D. student under Javan would later explain.
“At the time this was difficult and not applicable to all systems. Javan was able to see how a population inversion can be created in a gas discharge by selective, resonant energy transfer. This was key to his invention of the first gas laser, the He-Ne laser, which was also the first continuous wave laser.”
9. Lasers are Used For Medical Treatment for the First Time
The importance of the laser innovation or milestone: This was the first time laser technology was used to treat a human patient. It would pave the way for an explosion in future innovation in laser technology for use in surgery and medical treatment.
Year of Discovery/Development: 1961
Engineer or scientists behind the project: Dr. Charles J. Campbell and Charles J. Koester
Description of Milestone: Dr. Charles J. Campbell of the Institute of Ophthalmology at Columbia-Presbyterian Medical Center and Charles J. Koester of the American Optical Co. at Columbia-Presbyterian Hospital in Manhattan.
The procedure was incredibly fast and considerably more comfortable for the patient (when compared to conventional treatment using 1,000-watt Xenon arc lamps of the time).
In the years to come, the ruby laser was used in various medical treatments.
10. The Solid-State (Semiconductor Injection) Laser is Born
The importance of the laser innovation or milestone: The semiconductor injection laser was a revolution in laser technology at the time. It is still used in many electronic appliances and communication systems today.
Year of Discovery/Development: 1962
Engineer or scientists behind the project: Robert Noel Hall
Description of Milestone: Hall was inspired by the news in the early 1960's of the development of the first laser by Theodore H. Maiman et al to attempt to simplify the design and make them more stable.
He decided on attempting to dispense with existing 'pumping' models and focus on a solid-state alternative. Robert became aware of the optical properties of Gallium Arsenide diodes and how they can emit enormous amounts of IR radiation.
He immediately noticed the potential for this and began developing his now famous solid-state laser. Before too long, Robert and his team at GE had a working model that needed liquid nitrogen to cool it and it was only able to work in pulse mode.
Hall continued to work at GE until his retirement. He accumulated 43 patents and 81 publications throughout his esteemed career.
11. The Carbon Dioxide Laser Is Developed
The importance of the laser innovation or milestone: The Carbon Dioxide laser was one of the first gas lasers to ever be developed and is still in use today. It has proven to be one of the highest-power continuous wave lasers currently available.
Unlike other lasers, they are also fairly efficient with a ratio of output to pump power of as much as 20%. These lasers produce a beam of IR light between 9.4 and 10.6 micrometers.
Year of Discovery/Development: 1964
Engineer or scientists behind the project: Kumar Patel
Description of Milestone: Kumar developed the Carbon Dioxide laser whilst working at Bell Labs in 1964. These types of laser work by using Carbon dioxide as the primary gain medium which can also contain helium, nitrogen, hydrogen, water, and Xenon.
These types of laser are electrically pumped through gas discharge.
During operation, Nitrogen molecules are excited by the discharge into a metastable state whereby they transfer this extra energy into the Carbon Dioxide molecules during collisions. Helium tends to be included in the gas mix to depopulate the lower laser level and act as a thermal sink.
Other constituents such as hydrogen or water vapor can help (particularly in sealed-tube lasers) to reoxidize carbon monoxide (formed in the discharge) to carbon dioxide.
These kind's of laser tend to generate beams with a 10.6-micrometer wavelength but can operate between 9 and 11 micrometers. They also tend to have higher power conversions efficiencies when compared to other gas lasers and can be more efficient than lamp-pumped solid-state lasers.
They are however less efficient that diode-pumped lasers.
12. First Free Electron Laser at Stanford University
The importance of the laser innovation or milestone: The free electron laser uses very high-speed electrons moving through a magnetic structure as its lasing medium. This kind of laser is tunable and has the widest frequency of any laser technology.
Year of Discovery/Development: 1977
Engineer or scientists behind the project: John Madley/Stanford University
Description of Milestone: Free electron lasers are capable of generating wavelengths ranging from microwaves all the way through to X-Rays. John Madley first developed this type of laser in 1971 at Stanford University building on the work of Hans Motz et al who developed an undulator at Stanford in 1953.
These kinds of lasers have many types of applications from crystallography and cell biology to surgery, fat removal and, more recently have been used to develop anti-missile directed-energy weaponry.
13. The Future of Laser Tech: Solid State Heat Capacity Laser (SSHCL) Weapons
The importance of the laser innovation or milestone: Solid State Heat Capacity Lasers (SSHCL) are currently under development at the Lawrence Livermore National Laboratory. The plan is to improve this technology to produce average-power outputs of 100 kW or more.
This type of laser is a diode-pumped, solid-state setup designed for potential military weaponry.
"Potential military applications of such a system include the targeting and destruction of short-range rockets, guided missiles, artillery and mortar fire, unmanned aerial vehicles and improvised explosive devices, or IEDs." - Lawrence Livermore National Laboratory.
Year of Discovery/Development: 2001 onwards
Engineer or scientists behind the project: Lawrence Livermore National Laboratory/U.S. Army
Description of Milestone: In 2006, the Laboratory was able to accomplish 67 kilowatts of power marking a 50% increase the world-record-setting power level achieved the previous year. This was achieved using five ceramic neodymium-doped yttrium aluminum garnet laser-gain media slabs.
The ultimate vision is an electrically powered, solid-state laser that can be deployed on a hybrid-electric vehicle.
14. The Future of Laser Tech: Quantum Computing Applications
The importance of the laser innovation or milestone: Lasers might be the answer to making computers a million time faster than today by assisting in quantum computing.
By using laser-light pulses a bit could switch between on and off 1 quadrillion times per second.
Year of Discovery/Development: 2017
Engineer or scientists behind the project: University of Regensburg, Germany
Description of Milestone: Recent experiments have shown that using infrared laser pulses fired into a honeycomb-shaped lattice of tungsten and selenium can produce an astonishing speed of computing.
"In the long run, we see a realistic chance of introducing quantum information devices that perform operations faster than a single oscillation of a lightwave," study lead author Rupert Huber (Professor of physics at the University of Regensburg), said in a statement.
15. The Future of Laser Tech: Inertial Confinement Fusion
The importance of the laser innovation or milestone: The use of high-power lasers could make Inertial Confinement Fusion (ICF) possible in the future.
Year of Discovery/Development: 1962 onwards
Engineer or scientists behind the project: National Ignition Facility/Lawrence Livermore National Laboratory
Description of Milestone: ICF is a type of nuclear fusion research that is attempting to initiate a fusion reaction by heating and compressing the fuel source. This is usually a pellet of Deuterium and Tritium.
The idea is to compress and heat the pellet by directing energy to the outer layer of the target. Most research on this, to date, has involved the use of high powered lasers.
The heated outer layer then explodes outward thus producing a reaction force against the remainder of the target, accelerating it inwards, compressing the target. This process generates shock waves that travel inward through the target pellet.
If these waves can be made powerful enough it will further compress and heat the fuel at the center to such an extent that nuclear fusion should be achievable.