Yttrium aluminium garnet

Source: Wikipedia, the free encyclopedia.
Yttrium aluminium garnet
Specific gravity
4.5–4.6
Polish lusterVitreous to subadamantine
Optical propertiesSingle refractive
Refractive index1.833±0.010
BirefringenceNone
PleochroismNone
Dispersion0.028
Ultraviolet fluorescenceColorless stones - inert to moderate orange in long wave, inert to weak orange in short wave; blue and pink stones - inert; yellow-green stones - very strong yellow in long and short wave also phosphoresces; green stones - strong red in long wave, weak red in short wave
References[1]

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[2]) in a hexagonal or an orthorhombic, perovskite-like form, and the monoclinic Y4Al2O9 (YAM[3]).[4]

Due to its broad optical transparency,[5] low internal stress, high hardness, chemical and heat resistance, YAG is used for a variety of optics.[6] Its lack of birefringence (unlike sapphire) makes it an interesting material for high-energy/high-power laser systems. Laser damage levels of YAG ranged from 1.1 to 2.2 kJ/cm2 (1064 nm, 10 ns).[7]

YAG, like garnet and

cathode ray tubes and white light-emitting diodes, and as a scintillator
.

Gemstone YAG

YAG for a period[

alumina or diamond (50,000 or 100,000 grit) on common polishing laps. YAG has low heat sensitivity.[9]

As a synthetic gemstone YAG has numerous varietal and trade names, as well as a number of misnomers. Synonymous names include: alexite, amamite, circolite, dia-bud, diamite, diamogem, diamonair, diamone, diamonique, diamonite, diamonte, di'yag, geminair, gemonair, kimberly, Linde simulated diamond, nier-gem, regalair, replique, somerset, triamond, YAIG, and yttrium garnet. Production for the gem trade decreased after the introduction of synthetic cubic zirconia; as of 1995 there was little production.[1] Some demand exists as synthetic garnet, and for designs where the very high refractive index of cubic zirconia is not desirable.[citation needed]

Technical-use varieties

Nd:YAG

Main article: Nd:YAG laser
Nd:YAG laser rod 0.5 cm in diameter.

Nd:YVO4 crystals, however it is not as efficient and is less stable, requiring more precisely controlled temperatures. The best absorption band of Nd:YAG for pumping the laser is centered at 807.5 nm, and is 1 nm wide.[11]

Most Nd:YAG lasers produce infrared light at a wavelength of 1064 nm. Light at this wavelength is rather dangerous to vision, since it can be focused by the eye's

frequency doubling or frequency tripling crystals
, to produce green light with a wavelength of 532 nm or ultraviolet light at 355 nm, respectively.

The dopant concentration in commonly used Nd:YAG crystals usually varies between 0.5 and 1.4 molar percent. Higher dopant concentration is used for pulsed lasers; lower concentration is suitable for continuous-wave lasers. Nd:YAG is pinkish-purple, with lighter-doped rods being less intensely colored than heavier-doped ones. Since its absorption spectrum is narrow, the hue depends on the light under which it is observed.

Nd:Cr:YAG

YAG doped with

solar power satellite system.[13]

Er:YAG

Main article: Er:YAG laser

blood sugar. The mechanical properties of Er:YAG are essentially the same as Nd:YAG. Er:YAG operates at wavelengths where the threshold for eye damage is relatively high (since the light is absorbed before striking the retina), works well at room temperature, and has high slope efficiency. Er:YAG is pink.[14]

Yb:YAG

InGaAs laser diodes
at 940 or 970 nm.

Yb:YAG is a good substitute for 1064 nm Nd:YAG in high-power applications, and its frequency-doubled 515 nm version can replace the 514 nm

argon lasers
.

Nd:Ce:YAG

Neodymium-cerium double-doped YAG (Nd:Ce:YAG, or Nd,Ce:YAG) is an active laser medium material very similar to Nd:YAG. The added cerium atoms strongly absorb in the ultraviolet region and transfer their energy to the neodymium atoms, increasing the pumping efficiency; the result is lower thermal distortion and higher power output than Nd:YAG at the same pumping level. The lasing wavelength, 1064 nm, is the same as for Nd:YAG. The material has a good resistance to damage caused by UV from the pump source, and low lasing threshold. Usually 1.1–1.4% of Y atoms are replaced with Nd, and 0.05–0.1% with Ce.

Ho:Cr:Tm:YAG

Holmium-chromium-thulium triple-doped YAG (Ho:Cr:Tm:YAG, or Ho,Cr,Tm:YAG) is an active laser medium material with high efficiency. It lases at 2080 nm and can be pumped by a flashlamp or a laser diode.[17] It is widely used in military, medicine, and meteorology. It works well at room temperature, has high slope efficiency, and operates at a wavelength where the threshold for eye damage is relatively high. When pumped by a diode, the 785 nm band for Tm3+ ion can be used.[17] Other major pump bands are located between 400 and 800 nm. The dopant levels used are 0.35 atom.% Ho, 5.8 atom.% Tm, and 1.5 at.% Cr. The rods have green color, imparted by chromium(III).

Tm:YAG

Thulium-doped YAG (Tm:YAG) is an active laser medium that operates between 1930 and 2040 nm. It is suitable for diode pumping. A dual-mode Tm:YAG laser emits two frequencies separated by 1 GHz.

Cr4+:YAG

Nd:YVO4
, and Yb:YAG.

Cr:YAG can be also used as a laser gain medium itself, producing tunable lasers with outputs adjustable between 1350 and 1550 nm. The Cr:YAG laser can generate ultrashort pulses (in the femtoseconds range) when it is pumped at 1064 nm by a Nd:YAG laser.[18]

Cr:YAG has been demonstrated in an application of

phase-conjugate mirror in a Nd:YAG "loop resonator".[citation needed
] Such a mirror provides compensation of both phase and polarization aberrations induced into the loop resonator.

Dy:YAG

Dysprosium-doped YAG (Dy:YAG) is a temperature-sensitive phosphor used in temperature measurements.[19] The phosphor is excited by a laser pulse and its temperature-dependent fluorescence is observed. Dy:YAG is sensitive in ranges of 300–1700 K.[20] The phosphor can be applied directly to the measured surface, or to an end of an optical fiber. It has also been studied as a single-phase white emitting phosphor in phosphor-converted white light-emitting diodes.[21]

Sm:YAG

Samarium-doped YAG (Sm:YAG) is a temperature-sensitive phosphor similar to Dy:YAG.

Tb:YAG

Terbium-doped YAG (Tb:YAG) is a phosphor used in cathode ray tubes. It emits at yellow-green color, at 544 nm.

Ce:YAG

single-crystal form, with a wide range of uses. It emits yellow light when subjected to blue or ultraviolet light or to x-rays.[22] It is used in white light-emitting diodes as a coating on a high-brightness blue InGaN diode, converting part of the blue light into yellow, which together then appear as white. Such an arrangement gives less than ideal color rendering. The output brightness decreases with increasing temperature, further altering device color output.[citation needed
]

Ce:YAG is also used in some

cathode ray tubes, where it emits green (530 nm) to yellow-green (550 nm) light. When excited by electrons, it has virtually no afterglow (70 ns decay time). It is suitable for use in photomultipliers
.

Ce:YAG is used in

ultraviolet radiation
.

Ce:YAG can be further doped with gadolinium.

See also

References

  1. ^
    ISBN 0-87311-019-6
  2. ^ "YAlO
    3    ; YAP (YAlO
    3     ht) Crystal Structure"    . Springer Materials. Retrieved 2019-12-23.    .
  3. ^ "Y
    4    Al
    2    O
    9    ; YAM (Y
    4    Al
    2    O
    9     rt) Crystal Structure"    . Springer Materials. Retrieved 2020-01-28.
  4. S2CID 92455146
    .
  5. S2CID 239534251
    .
  6. ^ "Custom YAG (Yttrium Aluminium Garnet, Yttrium Aluminium Oxide Y3Al5O12) optics". Knight Optical. Retrieved 2022-03-15.
  7. PMID 19543361
    .
  8. ISBN 9780792398370
    .
  9. ^ Rice, Addison. "How to Spot a Fake Diamond: What These 13 Tests Really Mean!". International Gem Society. Retrieved 2021-02-15.
  10. doi:10.1016/j.jlumin.2015.04.018
  11. ^ "ND:YAG crystal (neodymium doped yttrium aluminium garnet)". Red Optronics.
  12. doi:10.1109/PROC.1966.5112
    .
  13. doi:10.1016/j.optcom.2006.07.002
    .
  14. S2CID 182269171
    . Retrieved 11 April 2022. Yttrium aluminum garnet (YAG) is an important optical ceramic material, especially when doped with Nd and Er, when it exhibits a specific color. For instance, Er:YAG is pink and Nd:YAG is a light reddish purple
  15. ISSN 2159-3930
    .
  16. ISBN 978-1-943580-20-0
    .
  17. ^
    ISBN 978-0-387-29094-2
    .
  18. ^ Paschotta, Rüdiger. "Chromium-doped gain media". Encyclopedia of Laser Physics and Technology. RP Photonics. Retrieved April 2, 2011.
  19. S2CID 234033077
    . Retrieved 20 April 2023.
  20. doi:10.1063/1.1140478
    .
  21. doi:10.1016/j.jlumin.2016.11.017
    .
  22. doi:10.1063/1.1755025
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