Lasers holmium

Silver-colored, ductile metal that is attacked slowly by air and water. The element exhibits interesting magnetic properties. Found in television tubes. Laser material such as YAG (yttrium-aluminum garnet) doped with holmium (as well as chromium and thulium) can be applied in medicine, especially in sensitive eye operations. 

The technical applications of holmium are limited. In ophthalmology, holmium-doped YAG lasers render a valuable service. 

Johnson et al. (55) have reported a phonon-assisted energy exchange from trivalent erbium to trivalent thulium or to trivalent holmium. In this case, these authors were able to rule out resonance exchange completely Of some importance is that these systems are useful for laser oscillators, and the energy exchange results in a substantial decrease in threshold. 

Ballman and co-workers (162) obtained laser Action for holmium, neodymium, praseodymium, and thulium, in rods of calcium niobate. Lifetime measurements of the 1.06-/x neodymium emissions and the... 

Johnson et al. (55) observed energy transfer from erbium to thulium and from erbium to holmium ions in crystals. They were able to obtain substantial decreases in laser thresholds because of this energy migration. The fluorescent lifetime of the 3//4 state of thulium in CaMo04 containing 0.75 atomic per cent erbium and 0.5 atomic per cent thulium as inferred from the time delay before the onset of laser oscillation is 900 /xsec at both IT and 20°K. 

Lasing action has been observed with other rare earths. The lower laser level in holmium is close to the ground state and can operate as a four level laser at liquid nitrogen temperatures. Erbium is similar to holmium. With other rare earths, alternate wavelengths can be obtained. Both Ho and Er operate in a region greater than 1.5 pm. Erbium can also... 

Possible sensitizers for lanthanide and actinide ions include other lanthanide and actinide ions, other transition group ions, and molecular complexes. These may be present either as added impurities or as a component of the host. Of the many sensitization schemes reported, some offer only marginal improvement. The most efficient crystal laser is "alphabet" holmium Ho3+ sensitized by Er +, Tm3+, and Yb +... 

The commercially important samarium-containing minerals are treated with concentrated sulfuric acid or, in the case of monazite, with a solution of sodium hydroxide (73%) at approximately 40°C (104°E) and under pressure. The element is separated from the solutions via solvent extraction or ion exchange. Sm salts are weakly yellow and may exhibit ion emission. Sm ions show luminescence and are sometimes used to generate lasers. Samarium is used in the manufacture of headphones and tape drivers, see ALSO Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Neodymium Praseodymium Promethium Terbium Ytterbium. 

Alsolaiman M, Reitz C, Nawras A, Rodgers J and Maliakkal J (2002) Bouveret s syndrome complicated by distal gallstone ileus after laser lithotropy using Holmium YAG laser. BMC Gastroenterol 2(1) 15. 

The wavelength of holmium lasers is 2.08 microns (safe to the human eye), which makes it safe to use them in a variety of medical and dental apphcations. For the latter, holmium-doped yttrium-aluminum garnet (YAG) and yttrium-lanthanum-fluoride (YLF) lasers are used (Gupta and Krishnamurthy 2005). 

Thulium is one of the most expensive of the rare earths, and therefore has little applications (Emsley 2001). Thulium is used as a dopant in YAG and YLF. Efficient flash lamp and laser diode-pumped laser operation has been achieved in Tm " YAG and Tm " YLF co-doped either with Cr " or Ho ". Thulium is also used in thulium-doped holmium lasers, which have outputs in the 2 pm region, a wavelength range of interest for coherent radar systems, remote sensing and medical applications (Koechner 2006). 

Specific examples of semiconductor laser array pumps include devices made from the AlGaAs material system. The emission wavelength can be varied from 700 to 900 nm by varying the Ga/Al composition. These emission wavelengths can be made to coincide with absorption bands of several important solid state lasing ions, such as neodymium, chromium, holmium, erbium, and promithium. 

Other YAG lasers have been constructed where ytterbium, erbium, thulium, or holmium is used instead of neodymium. 

A hand-held multiarm concentric-tube robotic system for transurethral laser prostate surgery has been reported previously [49]. The system is expected to facilitate holmium laser enucleation of the prostate for treating benign prostatic hyperplasia. It consists of a camera, a 6-DOF arm for tissue manipulation, and a 3-DOF arm for laser guidance deployed through an 8.66-mm endoscope. 

In the NIR side, the best lanthanides are 5dterbium, erbium, and neodymium (it is used in the Nd YAG laser, see Section 3.1.5). Holmium is less investigated but shows a very interesting emission spectrum with a red peak and an NIR peak. 

Holmium has almost no commercial applications, although it has unusual magnetic properties, which are used in the pole pieces of superconducting research magnets (Tallahassee, Florida). One variant of the YAG laser material is also holmium doped. 

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