Components for higher harmonics of Nd:YAG and Nd:YVO4 Lasers
The harmonics of Nd:YAG and Nd:YVO4 lasers are widely used for materials processing as well as for measurement applications. On these pages we introduce dual wavelength mirrors and separators for the fourth (266nm) and fifth harmonic (213nm). All designs are calculated according to customer specification.
| Reflectance at centre|
| Reflectance at the corresponding longer|
Nd:YAG wavelengths [%]
|3rd harmonic||355nm||> 99.7||> 99||< 5||< 2||< 10||< 2|
|4th harmonic||266nm||> 99.7||> 99||< 5||< 2||< 10||< 2||< 10||< 2|
|5th harmonic||213nm||> 97||> 93||< 5||< 2||< 10||< 2||< 10||< 2||< 10||< 2|
|Table 1:||Common specifications of separators for the harmonics in the UV|
|*||Fluoridic coating on CaF2|
(a): HR (0°, 532nm) > 99.5% + R (0°, 266nm) < 10% (rear side uncoated)
(b): HR (0°, 532nm) > 99.9% + R (0°, 266nm) < 5% (rear side uncoated)
Components for 266nm are normally produced by e-beam evaporation. These coatings exhibit high damage thresholds, but the reflectivity in the visible spectral range is limited to R > 99.5% (see figure 3a). Recent research results on sputtered coatings for the UV show, that separators with a significantly improved reflectivity in the VIS can be produced, which have similar properties in the UV (see figure 3b).
HRr (45°, 266nm) > 98% + Rr (45°, 213nm) < 10% for unpolarized light
a) oxide coatings optimized for low straylight losses (rear side uncoated)
b) fluoride coatings for high laser induced damage thresholds (rear side uncoated)
The fifth harmonic at 213nm is a critical wavelength for oxide coatings, because the absorption edge of aluminum oxide begins in this wavelength range. For high power applications we recommend fluoridic coatings on calcium fluoride which are produced according to the technology of ArF-excimer laser mirrors.
Thin Film Polarizers
a) HRs(56°, 266 nm) > 98 % + Rp(56°, 266 nm) < 1 %
b) HRs(56°, 213 nm) > 97 % + Rp(56°, 213 nm) < 5 %;
Please note that Tp ist only about 75% because of the above mentioned absortion losses
Magnetron sputtering enables us to offer thin film polarizers also for the fourth and fifth harmonic of the Nd:YAG laser.