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Bauteile für ArF Laser

Mirrors, Output Couplers and Lenses

All fluoride systems guarantee high reflectivities and high damage thresholds
PR coatings with tolerances of:
- ± 2 % for R = 10 … 30 %
- ± 3 % for R = 30 … 75 %
- ± 2 % for R = 75 … 90 % and
- ± 1 % for R > 90 %
High quality mirror substrates, windows and lenses of CaF₂ (193 nm excimer grade) and fused silica
Development and production of customer specific components such as beamsplitters and variable attenuators on request
Single wavelength AR coating with residual reflectivities of R < 0.25 % at AOI = 0° and R < 0.6 % at AOI = 45° (unpolarized light)
Broadband and multiple wavelength AR coatings

Figure 1: Measured reflectance and transmittance spectra of a turning mirror (AOI = 45°) for 193 nm for random polarized light (a) and a CaF₂ window coated on both sides with a fluoride AR coating for 193 nm (b)

Variable Attenuators

Attenuators with different transmission ranges on request
Attenuators can be delivered with AR coated compensation plates of CaF₂ of fused silica

Figure 2: Measured transmittance spectra of a variable attenuator at different AOI (a) and transmittance vs. AOI (b); the transmittance varies from T > 88 % at AOI = 0° to T < 2 % at AOI = 45°

Aluminium Mirrors

Enhanced aluminum mirrors:
- R_p > 93 %
- R_s > 99 %
- R_r > 96 %

Figure 3: Measured reflectance spectra of a protected Al mirror optimized for 193nm (a) and an enhanced Al mirror for 193 nm, AOI = 45° (b)

Technical Data of standard ArF Laser Components

Coating	Substrate	Damage threshold*	Lifetime test
Fluoride coatings
AR(0°, 193 nm), R < 0.25 %	CaF₂	4 – 5 J/cm²	2.5 x 10⁸ pulses, no damage**
AR(0°, 193 nm), R < 0.25 %	fused silica	2 – 3 J/cm²
PR(0°, 193 nm), R = 25 %	CaF₂	3 – 4 J/cm²	2.5 x 10⁸ pulses, no damage**
PR(0°, 193 nm), R = 50 %	CaF₂	2 – 3 J/cm²	10⁹ pulses***
HR(0°, 193 nm), R > 96 %	CaF₂	2 – 3 J/cm²	10⁹ pulses*, no damage 10¹⁰ pulses, no damage 4 x 10⁹ pulses***, no damage
HR(45°, 193 nm), R > 95 % (random polarized)	CaF₂	2 – 3 J/cm²
Oxide coatings
HR(0°, 193 nm), R > 92 %	fused silica	<1 J/cm²

*	1000-on-1, 14 ns; measurements were performed at Laser Labor Göttingen and at Friedrich-Schiller-Universität Jena
**	Energy density: 18 mJ/cm², repetition rate: 4 kHz, pulse duration: 30 ns; tested at COHERENT AG, Göttingen
***	Energy density: 55 mJ/cm², repetition rate: 1 kHZ, pulse duration 15 ns; tested at COHERENT AG, München
****	Energy density: 27 mJ/cm², repetition rate: 4 kHz, pulse duration: 30 ns; tested at COHERENT AG, Göttingen
*****	Energy density: 80 mJ/cm², repetition rate: 1 kHz, pulse duration: 12 ns; tested at COHERENT AG, München