Er:YAG Lasers and the 3 µm Region

Er:YAG lasers are widely used in medical applications, especially in dermatology, due to the high absorption coefficient of water for 2940 nm radiation. This makes surgical applications easier but is also a challenge for the optical coatings which must be completely free of water. Coatings produced by magnetron sputtering have proved to be ideal for this kind of application.

Cavity Mirrors

Fig.1:Reflectance spectrum of an HR cavity mirror
HR (0°, 2940 nm) > 99.8 %

Pump Mirrors

Fig.2:Reflectance spectrum of a HR cavity mirror with an HT region between 800 nm and 1100 nm

Reflectance of cavity mirrors and pump mirrors: R > 99.9 % at AOI = 0°
Pump mirrors with high transmittance between 800 nm and 1100 nm for pumping with a Nd:YAG laser or a diode laser

Turning Mirrors

Fig.3:Reflectance spectrum of a turning mirror for unpolarized light

Reflectance of turning mirrors: R > 99.8 % at AOI = 45° for unpolarized light

LIDT Info
400 J/cm², 2940 nm, 400 µs

Beam Combiners and Alignment Laser Mirrors

Fig.4:Reflectance spectra of turning mirrors

a)Dual wavelength turning mirror for 2940 nm and an alignment laser between 630 nm and 655 nm

b)Separator/combiner for 2940 nm and an alignment laser between 630 nm and 655 nm

Designs for beam splitters and alignment laser mirrors are calculated according to customer specifications

Output Couplers and Lenses

Fig.5:Reflectance spectra of output couplers with
R = 70 % ±1 % and R = 84 % ±1 %

Output couplers with precisely adjusted degrees of reflectance (tolerances of ±1 % at reflectance values between 70 % and 90 %)
AR coatings with residual reflectance of R < 0.2 % on the rear side of output couplers as well as on lenses and windows
Possible subtrate materials (see page Fused Silica):
- Fused Silica with low OH-content, like Corning 7979^®, Infrasil^®,Suprasil^® 3001/3002/300
- Sapphire and undoped YAG