LASER ACTIVE CRYSTAL: YSGG
LASER ACTIVE CRYSTAL: YSGG
Description
 crystals.jpg "Er; Cr,Er or Cr,Nd doped Yttrium Scandium Gallium Garnet (YSGG) crystals")
YSGG, or yttrium scandium gallium garnet, is a laser active crystal that is used in solid-state lasers. YSGG has a cubic crystal structure and is doped with chromium ions, which allow it to amplify light through stimulated emission.
One of the main advantages of YSGG as a laser active crystal is its ability to generate laser emissions at a wavelength of 2.79 microns, which is in the mid-infrared region. This makes YSGG lasers suitable for a variety of medical and dental applications, such as hard tissue ablation, cavity preparation, and soft tissue surgery.
YSGG lasers are typically pumped by a flashlamp or a diode laser, which excites the chromium ions in the crystal and causes them to emit light at a longer wavelength. YSGG lasers can also be mode-locked, which allows them to generate ultra-short pulses in the nanosecond or picosecond range.
YSGG has a relatively low thermal conductivity, which can lead to thermal effects such as thermal lensing and reduced efficiency at high pump powers. However, YSGG lasers can be designed to minimize these effects and optimize their performance for specific applications.
| Crystal | Er3+:YSGG | Cr3+,Nd3+:YSGG | Cr3+,Er3+:YSGG |
| Crystal structure | cubic | cubic | cubic |
| Dopant concentration | 30 - 50 at.% | Cr: (1 ÷ 2) x 1020; Nd: (2 ÷ 3) x 1020 | Cr: (1 ÷ 2) x 1020; Er: 4 x 1021 |
| Spatial group | Oh10 | Oh10 | Oh10 |
| Lattice constant, Å | 12.42 | 12.42 | 12.42 |
| Density, g/cm3 | 5.2 | 5.2 | 5.2 |
| Orientation | <001>, <111> | <001>, <111> | <001>, <111> |
| Mohs hardness | >7 | > 7 | > 7 |
| Thermal expansion coefficient | 8.1 x 10-6x°K-1 | 8.1 x 10-6 x°K-1 | 8.1 x 10-6 x°K-1 |
| Thermal conductivity, W x cm-1 x °K-1 | 0.079 | 0.06 | 0.06 |
| Refractive index, at 1.064 µm | 1.926 | - | - |
| Lifetime, µs | - | 240 | 1400 |
| Emission cross-section, cm2 | - | 1.5 x 10-19 | 5.2 x 10-21 |
| Relative (to YAG) efficiency of transformation of energy of the flash lamp | - | 2.3 | 1.5 |
| Termooptical factor (dn/dT) | 7 x 10-6 x°K-1 | - | - |
| Generated wavelength, µm | 2.797; 2.823 | - | - |
Comparative generation characteristics:
| Crystal type | Er:YSGG | Er:YAG |
| Er concerntation, at. % | 38 | 33 |
| Pumping wavelength, nm | 966 | 964 |
| Stimulated radiation wavelength, µm | 2.797; 2.823 | 2.830 |
| Generation threshold, mW | 72 | 418 |
| Max. power output at pumping power 720 mW, 966 nm | 201 | 51 |
| Slope efficiency, % | 31.1 | 16.9 |
Characteristics and applications of YSGG:
| Dopant | Cr,Nd | Cr,Ho,Tm | Cr,Er |
| Lasing wavelength, µm | 1.058 | 2.088 | 2.791 |
| Refractive index | 1.9263 | 1.9263 | 1.9263 |
| Termooptical factor (dn/dT) | 12.3 x 10-6 x °K-1 | 12.3 x 10-6 x °K-1 | 12.3 x 10-6 x °K-1 |
| Ultimate lasing regimes, Free running mode | overall efficiency 8% | overall efficiency 2.1% slope efficiency 3.1% | overall efficiency 2.1% slope efficiency 3.0% |
| Ultimate lasing regimes, Electro-optical Q-switch | pulse energy 500 mJ overall efficiency 4% | overall efficiency 0.16% slope efficiency 0.38% | |
| Sizes, (dia x length), mm | from 3 x 30 to 12.7 x 152.4 | from 3 x 30 to 9.5 x 101.6 | from 3 x 30 to12.7 x 127.0 |
| Fields of applications | material processing, scientific investigations | material processing, medical applications, lithotripsy | material processing, medical applications, scientific investigations |
Rods with round cross-sections are manufactured:
| Diameter tolerance, mm | + 0.0 / -0.1 |
| Length tolerance, mm | +1.0 / -0.0 |
| Chamfer | 45 ± 10° x 0.2 ± 0.1 mm |
| Parallelism | < 30' |
| Perpendicularity | < 15' |
| Flatness | < 0.2 |
| Absorption loss at 1150 nm, cm-1 | < 0.005 |
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