Coatings on Crystal Optics (340 – 3000 nm)

Laser applications using crystal optics have reached a high standard in industry and research. Optical coatings on crystals are an essential part of modern laser designs. They cover a wide range from single wavelength AR coatings on laser and nonlinear optical crystals up to complex multilayer coatings providing several high reflectance and high transmittance wavelength ranges and thus, replacing external laser mirrors. LAYERTEC has a lot of experience in coating laser crystals. LAYERTEC coatings are used in industrial high power Q-switched and cw lasers of several laser manufacturers. The quality of coatings on crystals depends on the coating technique as well as on the surface quality of the crystal. All coatings are produced using sputtering techniques which guarantee very low scattering losses and high environmental stability of the optical parameters.

The rapid progress in crystal growth techniques resulted in a wide variety of new crystals for laser applications, e.g. laser crystals like tungstanates and vanadates or nonlinear optical crystals like RTP. Each crystal type requires optimized polishing procedures and coating techniques. The coating design is determined by the optical properties of the crystal. However, the thermal expansion coefficients and the surface quality after storage and transport influence the coating quality as well. Especially, hygroscopic crystals like LBO or BBO require special pretreatments to achieve high damage thresholds and long lifetime for the coatings. Thus, coatings on new crystals always require experimental investigations to find the best coating procedures. Different dimensions and uncommon sizes and shapes are possible using the special LAYERTEC coating technology. The following table gives an overview about the crystals which have already been coated at LAYERTEC and the types of layer systems which have been applied successfully.

Table 1:Examples of available coatings on crystals

Crystal Type	AR/BBAR	Single HR optional with HT	Double HR/BBHR optional with HT
α-SiO₂ (Quartz)	x	x	x
BBO	x	—	—
BiBO	x	x
CaCO₃	x
CdMnTe	x
CTA	x
Nd:GdVO₄	x	x	x
Nd:GGG	x	x
Nd:Cr:GSGG	x	x
KTA	x	x
KTP	x	x	x
Yb:KGW, Yb:KYW	x	x	x
LBO	x	—	—
LiNbO₃	x
LMA	x
Nd:LSB	x	x	x
RTP	x
Ruby	x	x	x
Ti:Sapphire	x	x	x
Spinell	x	x	x
Cr:YAG	x	x	x
Er:YAG	x	x	x
Ho:YAG	x	x	x
Nd:YAG, Yb:YAG	x	x	x
Nd:YALO (YAP)	x
YLF	x
Nd:YVO₄	x	x	x
ZGP	x
ZnSe	x	x
x: established coating process
—: not possible due to technical reasons
empty box: not requested yet

Detailed measurement reports are available for each batch. Do not hesitate to contact LAYERTEC for a discussion or a quotation regarding your special coating project.

Coatings on Doped Laser Crystals

Coatings on Nonlinear Optical Crystals

Coatings on Doped Laser Crystals

Fig.1:Reflectance spectrum of a dual HR mirror with an HT region for pumping with a laser diode (on Nd:YAG):
HR (0°, 532 nm + 1064 nm) + HT (0°, 808 nm)

Fig.2:Reflectance spectrum of an AR coating for an Yb:KYW crystal:
AR (0°, 1030 nm) < 0.2 % + AR (0° – 30°, 980 nm) < 0.2 %.
Please note the large acceptance angle for the pump radiation

Sputtered coatings on laser rods, discs and slabs with:

High laser-induced damage thresholds for critical industrial applications of Q-switched and cw lasers
Low residual reflectance
Broadband and multiple wavelength AR coatings
Complex HR and HR/HT-coatings for compact laser designs, e.g. HR (0°, 532 nm + 1064 nm) > 99.9 % + R (0°, 808 nm) < 5 %, on Nd:YVO₄ for diode-pumped and frequency-doubled “green” lasers)
Coating of crystals with variable or special sizes and shapes
Coating of the full aperture of small crystals

Coatings on Nonlinear Optical Crystals

Fig.3:Reflectance spectrum of a triple wavelength AR coating on KTP:
AR (0°, 1064 nm + 1575 nm + 3400 nm) < 0.5 %

Fig.4:Reflectance spectrum of an AR-coating:
AR (0°, 750 – 850 nm) < 0.5 % on CdMnTe

Fig.5:Reflectance spectrum of a triple wavelength AR-coating:
R (0°, 343 nm + 515 nm + 1030 nm) < 0.75 % on BBO

Fig.6:Reflectance spectrum of a dichroic mirror on KTP:
R (0°, 532 nm) < 1 % + HR (0°, 1064 nm) > 99.95 %

Coatings on Crystal Optics (340 – 3000 nm)

Coatings on Doped Laser Crystals

Sputtered coatings on laser rods, discs and slabs with:

Coatings on Nonlinear Optical Crystals

Coatings on Crystal Optics (340 – 3000 nm)