A Pr:YLF laser (or Pr3+:LiYF4 laser) is a solid state laser that uses a praseodymium doped yttrium-lithium-fluoride crystal as its gain medium. The first Pr:YLF laser was built in 1977 and emitted pulses at 479 nm. [1] Pr:YLF lasers can emit in many different wavelengths in the visible spectrum of light, making them potentially interesting for RGB applications and materials processing. Notable emission wavelengths are 479 nm, 523 nm, 607 nm and 640 nm.
Pr:YLF lasers are optically pumped using flashlamps, pulsed dye lasers or diode lasers. The strongest emission line of Pr:YLF is 640 nm, which stems from the transition of the Pr3+- ion. However, by suppressing this line (and other lines stronger than the desired one), other transitions can be used for obtaining different wavelengths. This can be done using dichroic mirrors. Pr:YLF lasers are pumped by using the transitions from to , or (corresponding wavelengths: 444 nm, 469 nm, 479 nm). The Pr3+- ion then undergoes a quick, radiationless transition (fast relaxation), followed by the light-emitting transition. Finally, the ground level () is reached via another radiationless transfer, making the Pr:YLF laser a 4-level system. [2] Pr:YLF supports lasing at the following wavelengths: 479 nm, 523 nm, 546 nm, 607 nm, 640 nm, 698 nm, 721 nm, 907 nm and 915 nm. [3]
The transition is of special interest, since its wavelength (444 nm) can be covered by InGaN laser diodes, which are commercially available at high output powers. Because the absorption peak at 444 nm only has a bandwidth of a few nanometers, pumpdiodes have to be selected and stabilized for efficient laser action. Diode pumped solid state (DPSS) lasers using these diodes have reached multiple watts of output powers in continuous wave operation. Typical DPSS setups using Pr:YLF crystals consist of a hemispheric resonator in which the crystal is pumped longitudinally by the pump diode. Depending on the resonator length, this resonator type can tolerate slight misalignments of the mirrors and retains stability even if the crystal shows thermal lensing effects. The plane mirror of the resonator can be replaced by coating one face of the crystal, making the setup very compact. [2]
Although several other rare-earth dopants such as Sm3+, Tb3+, Dy3+, Ho3+ and Er3+ offer transitions in the visible spectrum, the most efficient emission in this region is achieved by Pr:YLF lasers [4]
Pr:YLF lasers can be operated in continuous wave (cw) or pulsed mode. Q-Switched and frequency-doubled Pr:YLF lasers have also been reported. [5]
Pr:YLF lasers, especially in combination with high power InGaN laser diodes, are of high scientific interestic because of their emission lines in the visible spectrum of light and potentially very compact laser setups. Besides biomedical applications such as fluorescence microscopy or cytometry, [6] Pr:YLF lasers also are very attractive for the use in powerful RGB light sources. [7]
Furthermore, compact and efficient continuous wave (deep) UV lasers can be made by frequency doubling the output of Pr:YLF lasers. [8] Nanosecond UV pulses can be obtained by Q-switching frequency doubled Pr:YLF lasers. [5] Pulsed and/or continuous wave UV lasers can be used for very precise materials processing, photoluminescence analysis, lithography for semiconductor manufacturing and inspection, UV Raman spectroscopy, eye surgery, etc. [9]
Applications also include precise and efficient materials processing of some non-ferrous metals like copper or gold. [10]
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.
A laser is constructed from three principal parts:
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Many practical applications, including chemical and biological effects, derive from the way that UV radiation can interact with organic molecules. These interactions can involve absorption or adjusting energy states in molecules, but do not necessarily involve heating.
A laser diode is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction.
A helium–neon laser or He-Ne laser, is a type of gas laser whose high energetic medium gain medium consists of a mixture of 10:1 ratio of helium and neon at a total pressure of about 1 torr inside of a small electrical discharge. The best-known and most widely used He-Ne laser operates at a wavelength of 632.8 nm, in the red part of the visible spectrum.
A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 nanometers or more. The wide bandwidth makes them particularly suitable for tunable lasers and pulsed lasers. The dye rhodamine 6G, for example, can be tuned from 635 nm (orangish-red) to 560 nm (greenish-yellow), and produce pulses as short as 16 femtoseconds. Moreover, the dye can be replaced by another type in order to generate an even broader range of wavelengths with the same laser, from the near-infrared to the near-ultraviolet, although this usually requires replacing other optical components in the laser as well, such as dielectric mirrors or pump lasers.
Nd:YAG (neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12) is a crystal that is used as a lasing medium for solid-state lasers. The dopant, triply ionized neodymium, Nd(III), typically replaces a small fraction (1%) of the yttrium ions in the host crystal structure of the yttrium aluminum garnet (YAG), since the two ions are of similar size. It is the neodymium ion which provides the lasing activity in the crystal, in the same fashion as red chromium ion in ruby lasers.
Ti:sapphire lasers (also known as Ti:Al2O3 lasers, titanium-sapphire lasers, or Ti:sapphs) are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers. These lasers are mainly used in scientific research because of their tunability and their ability to generate ultrashort pulses. Lasers based on Ti:sapphire were first constructed and invented in June 1982 by Peter Moulton at the MIT Lincoln Laboratory.
A diode-pumped solid-state laser (DPSSL) is a solid-state laser made by pumping a solid gain medium, for example, a ruby or a neodymium-doped YAG crystal, with a laser diode.
Yttrium aluminium garnet (YAG, Y3Al5O12) is a synthetic crystalline material of the garnet group. It is a cubic yttrium aluminium oxide phase, with other examples being YAlO3 (YAP) in a hexagonal or an orthorhombic, perovskite-like form, and the monoclinic Y4Al2O9 (YAM).
Neodymium-doped yttrium orthovanadate (Nd:YVO4) is a crystalline material formed by adding neodymium ions to yttrium orthovanadate. It is commonly used as an active laser medium for diode-pumped solid-state lasers. It comes as a transparent blue-tinted material. It is birefringent, therefore rods made of it are usually rectangular.
An ion laser is a gas laser that uses an ionized gas as its lasing medium. Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry–Pérot resonator. Unlike helium–neon lasers, the energy level transitions that contribute to laser action come from ions. Because of the large amount of energy required to excite the ionic transitions used in ion lasers, the required current is much greater, and as a result all but the smallest ion lasers are water-cooled. A small air-cooled ion laser might produce, for example, 130 milliwatts of output light with a tube current of about 10 amperes and a voltage of 105 volts. Since one ampere times one volt is one watt, this is an electrical power input of about one kilowatt. Subtracting the (desirable) light output of 130 mW from power input, this leaves the large amount of waste heat of nearly one kW. This has to be dissipated by the cooling system. In other words, the power efficiency is very low.
A blue laser is a laser that emits electromagnetic radiation with a wavelength between 360 and 480 nanometers, which the human eye sees as blue or violet.
Quantum-cascade lasers (QCLs) are semiconductor lasers that emit in the mid- to far-infrared portion of the electromagnetic spectrum and were first demonstrated by Jérôme Faist, Federico Capasso, Deborah Sivco, Carlo Sirtori, Albert Hutchinson, and Alfred Cho at Bell Laboratories in 1994.
A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960.
In optics, a supercontinuum is formed when a collection of nonlinear processes act together upon a pump beam in order to cause severe spectral broadening of the original pump beam, for example using a microstructured optical fiber. The result is a smooth spectral continuum. There is no consensus on how much broadening constitutes a supercontinuum; however researchers have published work claiming as little as 60 nm of broadening as a supercontinuum. There is also no agreement on the spectral flatness required to define the bandwidth of the source, with authors using anything from 5 dB to 40 dB or more. In addition the term supercontinuum itself did not gain widespread acceptance until this century, with many authors using alternative phrases to describe their continua during the 1970s, 1980s and 1990s.
Neodymium-doped yttrium lithium fluoride (Nd:YLF) is a lasing medium for arc lamp-pumped and diode-pumped solid-state lasers. The YLF crystal (LiYF4) is naturally birefringent, and commonly used laser transitions occur at 1047 nm and 1053 nm.
The McCumber relation is a relationship between the effective cross-sections of absorption and emission of light in the physics of solid-state lasers. It is named after Dean McCumber, who proposed the relationship in 1964.
A nanophotonic resonator or nanocavity is an optical cavity which is on the order of tens to hundreds of nanometers in size. Optical cavities are a major component of all lasers, they are responsible for providing amplification of a light source via positive feedback, a process known as amplified spontaneous emission or ASE. Nanophotonic resonators offer inherently higher light energy confinement than ordinary cavities, which means stronger light-material interactions, and therefore lower lasing threshold provided the quality factor of the resonator is high. Nanophotonic resonators can be made with photonic crystals, silicon, diamond, or metals such as gold.
Lightwave Electronics Corporation was a developer and manufacturer of diode-pumped solid-state lasers, and was a significant contributor to the creation and maturation of this technology. Lightwave Electronics was a technology-focused company, with diverse markets, including science and micromachining. Inventors employed by Lightwave Electronics received 51 US patents, and Lightwave Electronics products were referenced by non-affiliated inventors in 91 US patents.
