The essential components of a laser are an external energy source, a gain or amplifier medium, and a resonator. When a medium, for example an Nd:YAG crystal is arranged so between two mirrors that photons always trigger an “induced emission”, this is called an optical resonator. The supply of external energy also is called pumping. In this case, the energy is supplied by the intensive radiation of a thermal high-capacity light source, for example a flash lamp.
The gain medium is excited by the pump source to produce a population inversion, and it is in the gain medium where spontaneous and stimulated emission of photons takes place, leading to the phenomenon of optical gain, or amplification.
The laser medium is located in an optical resonator, in its simplest form is two parallel mirrors placed around the gain medium which provide feedback of the light. The mirrors are given optical coatings which determine their reflective properties. Typically one will be a high reflector, and the other will be a partial reflector. The latter is called the output coupler, because it allows some of the light to leave the cavity to produce the laser’s output beam.
The photons travel back and forth between the mirrors, causing continuous light emissions in the medium, thus amplifying the generated beam. This realizes the formation of a standing wave, which is created when a wave is reflected and overlaps itself. This creates the impression that the wave has stopped.
Laser Gain Materials
The gain medium is the major determining factor of the wavelength of operation, and other properties, of the laser. Gain media in different materials have linear spectra or wide spectra. Gain media with wide spectra allow tuning of the laser frequency.
There are hundreds if not thousands of different gain media in which laser operation has been achieved. Not only solid materials (Nd:YAG, ruby crystals, or semiconductors), but also gases (carbon dioxide, nitrogen, helium-neon mixed metal vapors) or liquids (solutions of organic pigment molecules) are used as laser media. The wavelength of the laser radiation is determined by their special energy level.
Various gain media used in laser technologies differ greatly in essential properties such as wavelength ranges and tunability, pumping options, efficiency, and capability for energy storage and high powers.
Selecting from but a handful of commercially available laser crystals, laser designers have produced an impressive array of solid state lasers able to perform a wide range of scientific, industrial and military applications.
Despite this, it sometimes proves difficult, if not impossible, to design lasers meeting some applications requirements, when drawing only on presently commercially-available laser crystals, especially when particularly demanding size, weight, and efficiency requirements are imposed.
Neodymium and alumina are two of the most widely used components in today’s state-of-the-art solid-state laser materials. Neodymium ions, a type of light-emitting atoms, are used to make high-power lasers. Alumina crystals, a type of host material for light-emitting ions, can yield lasers with ultra-short pulses. Alumina crystals also have the advantage of high thermal shock resistance, meaning they can withstand rapid changes in temperature and high loads of heat.
However, combining neodymium and alumina to make a lasing medium is challenging. The problem is that they are incompatible in size. Alumina crystals typically host small ions like titanium or chromium. Neodymium ions are too big — they are normally hosted inside a crystal called yttrium aluminum garnet (YAG).
By doping alumina crystals with neodymium ions, engineers at the University of California San Diego have developed a new laser material that is capable of emitting ultra-short, high-power pulses — a combination that could potentially yield smaller, more powerful lasers with superior thermal shock resistance, broad tunability and high-duty cycles.
“Until now, it has been impossible to dope sufficient amounts of neodymium into an alumina matrix. We figured out a way to create a neodymium-alumina laser material that combines the best of both worlds: high power density, ultra-short pulses and superior thermal shock resistance,” said Javier Garay, a mechanical engineering professor at the UC San Diego Jacobs School of Engineering.
To achieve this advance, engineers devised new materials processing strategies to dissolve high concentrations of neodymium ions into alumina crystals. The result, a neodymium-alumina laser gain medium, is the first in the field of laser materials research. It has 24 times higher thermal shock resistance than one of the leading solid-state laser gain materials.
Cramming more neodymium into alumina
The key to making the neodymium-alumina hybrid was by rapidly heating and cooling the two solids together. Traditionally, researchers dope alumina by melting it with another material and then cooling the mixture slowly so that it crystallizes. “However, this process is too slow to work with neodymium ions as the dopant — they would essentially get kicked out of the alumina host as it crystallizes,” explained first author Elias Penilla, a postdoctoral researcher in Garay’s research group. So his solution was to speed up the heating and cooling steps fast enough to prevent neodymium ions from escaping.
The new process involves rapidly heating a pressurized mixture of alumina and neodymium powders at a rate of 300 C per minute until it reaches 1,260 C. This is hot enough to “dissolve” a high concentration of neodymium into the alumina lattice. The solid solution is held at that temperature for five minutes and then rapidly cooled, also at a rate of 300 C per minute.
Researchers characterized the atomic structure of the neodymium-alumina crystals using X-ray diffraction and electron microscopy. To demonstrate lasing capability, researchers optically pumped the crystals with infrared light (806 nm). The material emitted amplified light (gain) at a lower frequency infrared light at 1064 nm.
In tests, researchers also showed that neodymium-alumina has 24 times higher thermal shock resistance than one of the leading solid-state laser gain materials, neodymium-YAG. “This means we can pump this material with more energy before it cracks, which is why we can use it to make a more powerful laser,” said Garay.
The team is working on building a laser with their new material. “That will take more engineering work. Our experiments show that the material will work as a laser and the fundamental physics is all there,” said Garay. This work was supported by the High Energy Laser — Joint Technology Office administered by the Army Research Office.
Diamond Lasers 20 Times More Powerful Than Ever Before
Researchers have succeeded in using a diamond to concentrate a flash of light into a laser beam. While this may have been done before, no one has ever done so with such brilliance. The laser is 20 times more powerful than previous diamond lasers and even has enough power to cut through steel. Talk about outshining one’s competition.
The laser’s strength could have far-reaching applications: It has the necessary properties for optical communication in space, for measuring coordinates by reflecting light off a satellite, and even for sweeping up space debris from Earth. For this space-sweeping job, a laser must be powerful enough to penetrate the Earth’s atmosphere and still have enough energy to nudge small debris so that it burns up in the atmosphere. Fortunately, the diamond laser shines at a wavelength with a high transmission rate through the atmosphere, so it might be up for the job. All with a bit of sparkly flair.
Diamonds are an emerging material for laser beam usage, but it looks like their days of “being in the rough” are drawing to a close. As synthetic diamond technology advances, the quality of the diamonds is increasing. Synthetic diamonds are now better than what we can obtain from the ground, and it’s this high-quality mineral that is essential for powerful lasers such as this one.
These brilliant gems are also proving to be rather versatile. A past restriction with lasers was that it was difficult to manufacture a beam of light at every single wavelength. For example, a ruby produces a wavelength at 694.3 nanometers, which is deep red in color. Titanium-sapphire laser crystals can be chemically tuned to produce wavelengths between 650-1,100 nanometers – also red light. The diamond laser has filled in some gaps and can produce light at a wavelength of 1,240 nanometers, which was previously unattainable.”Just as X-rays pass through flesh to enable us to see bones within a body, different colours of laser radiation can interact or be transmitted by different target materials,” said lead researcher Dr. Robert Williams.
Laser Materials Market
Laser Materials Market size was close to USD 1.31 billion in 2019 and will grow at a CAGR of 4.5% from 2020 to 2026. Global Market Insights, Inc. has estimated Market size will exceed USD 1.7 billion by 2024.
With a broader spectrum of application across the healthcare, military, and communication, laser materials market penetration has generated a remarkable momentum. Rising popularity of laser technology in advanced metal processing techniques, medical surgery, and 3D printing along with persistent need for enhanced communication and directed-energy weapons in military & scientific applications will boost the product business during the assessment period.
Due to the light weight laser weapons and low-cost operation, the product has gained momentum military R&D. Another driving force behind the interest in laser materials include the technological need for tunable laser source. Reduced material prices coupled with their reliability and enhanced lifespan are further pushing the laser materials market demand. Vigorous growth is projected in R&D areas that will competently take advantage of the properties of laser radiation.
Replacement of non-laser technologies in medical industry has significantly boosted the laser materials market. The increased medical applications such as cosmetic procedures, diagnosis of diseases and tattoo removal have accelerated the use of laser treatments. The electronics and communication industry has noticeably profited from the laser technology in terms of speed and amount of data transfer, which will augment the product market in future.
In micro and macro machining applications such as fiber laser based cutting and direct diode, laser technology has shown a remarkable contribution which will escalate the growth of the laser materials market. The product has shown a high demand in welding industry which will continue to grow in the projected period. The implementation of ceramics as laser materials is projected to grow at a considerable CAGR of 9.1% in terms of revenue.
Growing demand for enhanced mobility solutions along with surging sales of electric vehicles across the globe will significantly impact the industry growth. It is evident that Japanese vehicle manufacturers use Nd:YAG and Co2 lasers for fabricating power train & body, roof rail welding, and tailoring blanks to gain a competitive edge.
The ceramics materials product segment was close to USD 18 million in 2019 and is likely to grow at a decent growth rate of 6.9% in the overall laser materials market share. Ceramics materials are used in high-powered and solid-state lasers as a replacement to single crystals and glass to generate laser beams owing to its efficient properties such as low thermal expansion coefficient, low optical scattering, low dependence of index of refraction, toughness, and optical path length of temperature.
In the defense sector, the novel development of High-Energy Lasers (HEL) has shown immense potential in drones and weapons. Manufacturers are developing innovative solutions to further integrate laser technology into military equipment. Emerging applications in security with airborne laser mine detection, anti-missile systems, and target designation will surge the laser materials market demand by 2026.
However, oscillating raw material prices and feedstocks might hinder the laser materials market growth. Laser technology poses several challenges, such as high upfront cost, high-power consumption, limitation in metal thickness, and dangerous fumes, to end users, which need to be considered.
Prominent industry participants include Asahi Glass Co., Ltd, Morgan Advanced Materials, BASF SE, Dow Chemical Company, GrafTech International, Taishan Fiberglass inc., CeramTec GmbH, Sinopec Shanghai Petrochemical Co., Ltd, Murata Manufacturing Co., Ltd., Anglo American plc., Mitsubishi Chemical Holdings Corp., Norilsk Nickel, Evonik Industries, Universal Laser Systems, Inc., and Corning Inc.
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