Laser | Definition, Acronym, Principle, Applications, & Types

Laser Full Form is "Light Amplification by Stimulated Emission of Radiation." This term was coined in 1957 by Gordon Gould, a pioneer in laser technology. Originally, the term described a principle of operation involving the stimulated emission from excited atoms or ions. 

Today, laser generally refers to devices that generate light using this principle. These devices are typically laser oscillators, but the term can also include devices with laser amplifiers, known as master oscillator power amplifiers (MOPA). 

Additionally, some nonlinear devices like optical parametric oscillators and Raman lasers, which are often powered by lasers and produce laser-like light beams, are sometimes considered under the broader interpretation of lasers, though they are not technically lasers themselves.

What is Laser?

A laser is a tool that produces a focused beam of light through a process called optical amplification. There are various types of lasers, such as gas lasers, fiber lasers, solid-state lasers, dye lasers, diode lasers, and excimer lasers. Despite their differences, all lasers have some common basic parts. Laser technology is central to the broader field of photonics because laser light has unique properties:

1. Directional Beam: Laser light is typically emitted as a well-directed beam that can travel long distances without spreading out much, thanks to its high spatial coherence. This beam can be focused into very small spots, achieving high intensity.
2. Narrow Bandwidth: Unlike most lamps that emit light with a wide range of wavelengths, lasers often have a very narrow optical bandwidth (high temporal coherence). There are also broadband lasers, especially among ultrafast lasers.
3. Continuous or Pulsed Emission: Laser light can be emitted continuously or in short pulses, with durations ranging from microseconds to femtoseconds. These pulses can create very high intensities due to their temporal energy concentration and spatial confinement.

These special properties of laser light, resulting from its high degree of spatial and temporal coherence, make it valuable for many applications. The first laser, a pulsed lamp-pumped ruby laser (a type of solid-state laser), was demonstrated by Theodore Maiman in 1960. That same year saw the creation of the first gas laser (a helium-neon laser) and the first laser diode. 

Prior to these developments, significant theoretical work on laser principles was published by Arthur Schawlow, Charles Hard Townes, Nikolay Basov, and Alexander Prokhorov. Townes' group had also developed a microwave amplifier and oscillator (maser) in 1953. Initially, lasers were referred to as "optical masers." In laser technology, various optical components are used, including laser crystals, laser mirrors, polarizers, Faraday isolators, and tunable optical filters. 

Lasers are integral to various technologies, including laser cutters, laser printers, and laser cutting machines. These devices leverage the unique properties of lasers to perform precise and efficient cutting, printing, and other tasks. The high intensity and focus of laser beams make laser cutters and laser cutting machines particularly effective in industrial applications, while laser printers use the precision of lasers to produce high-quality prints.

History of Laser

The laser originated from a suggestion made by Albert Einstein in 1916. He proposed that under the right conditions, atoms could release excess energy as light, either spontaneously or when stimulated by light. In 1928, German physicist Rudolf Walther Ladenburg observed stimulated emission, but it had no practical use at that time. In 1951, Charles H. Townes at Columbia University came up with a way to generate stimulated emission at microwave frequencies. 

By the end of 1953, he created a device that used "excited" ammonia molecules in a microwave cavity to emit a pure microwave frequency. He named this device a maser, which stands for "microwave amplification by the stimulated emission of radiation.

" Around the same time, Aleksandr Prokhorov and Nikolay Basov in Moscow independently developed the theory of maser operation. In 1964, Townes, Prokhorov, and Basov shared the Nobel Prize in Physics for their work. In the mid-1950s, maser research flourished, but its applications were limited to low-noise microwave amplifiers and atomic clocks. In 1957, Townes suggested to his brother-in-law Arthur L. Schawlow that they extend maser action to infrared or visible light. 

They published their ideas in 1958, coining the term "optical maser." Gordon Gould, a graduate student at Columbia, also developed his own ideas and coined the term laser, which stands for "light amplification by the stimulated emission of radiation." This led to a long legal battle over who should be credited as the laser's inventor, but Gould eventually received patents starting in 1977. 

The first successful laser was built by Theodore H. Maiman at Hughes Research Laboratories in 1960. He used a synthetic ruby crystal and bright pulses from a flash lamp to excite chromium atoms, producing red pulses from the ruby rod. Later that year, Ali Javan and his team at Bell Labs created the first gas laser, using a helium-neon mixture to generate a continuous infrared beam. 

In 1962, Robert N. Hall and his team at General Electric developed the first semiconductor laser. Initially, lasers captured the public's imagination but practical applications took time to develop. Irnee D’Haenens, working with Maiman, joked that the laser was "a solution looking for a problem.

Early applications included using lasers for basic research, signaling through air or space, and creating powerful beams for cutting and drilling materials. In 1963, Emmett Leith and Juris Upatnieks at the University of Michigan made the first three-dimensional holograms using lasers. 

The first commercial laser applications came with helium-neon lasers, which produced visible red beams for alignment, surveying, construction, and eye surgery. Ruby lasers were used in eye surgery to reattach retinas without cutting into the eye. 

The first large-scale use of lasers was in supermarket checkout scanners developed in the mid-1970s. Soon after, lasers were used in compact disc players and laser printers for personal computers. Today, lasers are used in many fields. Laser cutters and laser cutting machines are standard in manufacturing. 

Laser printers are common in homes and offices. Lasers are used for pointing in presentations, guiding smart bombs, welding razor blades, marking objects on production lines, removing hair, and bleaching tattoos. Laser rangefinders have mapped the surfaces of Mars and the asteroid Eros in great detail. In laboratories, lasers help physicists cool atoms to near absolute zero.

Types of Lasers

Laser technology is a diverse field that uses various types of laser gain media, optical elements, and techniques. Here are some common types of lasers:

Semiconductor Lasers

These include laser diodes that are either electrically or optically pumped. They can produce very high output powers, though often with poor beam quality, or low powers with good spatial properties. For example, they are used in CD and DVD players. 

They can also generate pulses for telecom applications with very high pulse repetition rates. Special types of semiconductor lasers include quantum cascade lasers (for mid-infrared light) and surface-emitting semiconductor lasers (VCSELs, VECSELs, and PCSELs). Some of these lasers are suitable for generating pulses with high power.

Solid-State Lasers

These lasers are based on ion-doped crystals or glasses and are pumped with discharge lamps or laser diodes. They can produce high output powers or lower powers with excellent beam quality, spectral purity, and stability. They are also used for generating ultrashort pulses with picosecond or femtosecond durations.

Fiber Lasers

These lasers use optical glass fibers doped with laser-active ions in the fiber core. Fiber lasers can achieve very high output powers (up to kilowatts) with high beam quality. They also offer wide wavelength tunability and narrow linewidth operation.

Gas Lasers

Gas lasers use gases excited by electrical discharges. Common examples include helium-neon lasers, CO2 lasers, argon ion lasers, and excimer lasers. Frequently used gases in these lasers are CO2, argon, krypton, and gas mixtures like helium-neon. 

Excimers such as ArF, KrF, XeF, and F2 are also common. When gas molecules are involved in the laser process, these lasers are also called molecular lasers. Less common types of lasers include chemical and nuclear pumped lasers, free electron lasers, and X-ray lasers. 

By using these various types of lasers, different applications can be met with specific needs for power, beam quality, and pulse durations. Laser technology continues to evolve, offering new possibilities for scientific, medical, industrial, and everyday uses.

Application of Laser

• Wide Range of Uses: Laser devices have many applications due to their unique properties that other light sources can't achieve. Major uses include laser material processing, optical data transmission and storage, and optical metrology. For more details, see the article on laser applications.
• Current Limitations: Many potential laser applications are not yet practical because lasers are expensive to produce. Most lasers are made using costly methods, produced in small quantities, and with limited automation. Additionally, lasers are sensitive to precise alignment, mechanical vibrations, and dust particles. Research is ongoing to find more cost-effective and robust solutions.
• Business Success Factors: Developing high-performance, low-cost lasers is crucial for business success. It’s also essential to identify the best-suited applications for these lasers. Understanding the application details is very important. For instance, in laser material processing, knowing the exact requirements for laser wavelength, beam quality, pulse energy, and pulse duration is vital for optimal results.