Components for F2 Lasers
Mirrors, Output Couplers and Lenses
Figure 1: Measured reflectance and transmittance spectra of a laser mirror (AOI = 0°, a) and a turning mirror (AOI = 45°, b) for 157 nm 
Figure 2: Measured reflectance spectra of standard output couplers with R = 50 ± 3 % and R = 25 ± 2 % (rear side uncoated) - Laser mirrors: R = 92 … 95 % at AOI = 0°
- Turning mirrors (AOI = 45°):
- Rs > 97 %
- Rp > 90 %
- Rr > 92 %
- High quality mirror substrates, windows and lenses of CaF2 (157 nm excimer grade quality)
- PR coatings with tolerances of
- ± 2 % for R = 10 … 30 %
- ± 3 % for R = 30 … 75 % and
- ± 2 % for R = 75 … 90 %
- Development and production of customer specific components as beamsplitters and variable attenuators on request
Variable Attenuators
Figure 3: Measured transmittance spectra of a variable attenuator at different AOI (a) and transmittance vs. AOI (b); the transmittance varies from T > 75 % at AOI = 0° to T < 5% at AOI = 45°Aluminium Mirror for F2 Lasers
Figure 4: Reflectance spectrum of a protected Al mirror (a) and an enhanced Al mirror for 157 nm (b) - Protected Al mirrors (optimized for 157 nm): R = 74 … 78 %
- Dielectrically enhanced Al mirrors: up to R = 94 % at AOI = 0°
Technical Data of standard F2 Laser Components
| Coating | Spectral performance | Lifetime test |
|---|
| HR(0°, 157 nm) | R = 92 … 95 % | 2 x 108 – 1 x 109 pulses* |
| HR(45°, 157 nm) | R = 90 … 94 % (random pol.) | |
| PR(0°, 157 nm) | R = 50 ± 3 % | 2 x 108 – 1 x 109 pulses* |
| PR(0°, 157 nm) | R = 25 ± 3 % | 2 x 108 – 1 x 109 pulses* |
| Attenuator | T = 67 ± 3 % | 5 x 107 pulses**, no damage |
| Attenuator | T = 33 ± 3 % | 1 x 108 pulses***, no damage |
| Beamsplitter | T = 20 ± 3 % | 1 x 108 pulses***, no damage |
| AR(0°, 157 nm) | 0.3 … 0.7 % | |
| * | Energy density: 25mJ/cm2, repetition rate: 800Hz, pulse duration: 15ns; tested at COHERENT AG, München |
| ** | Energy density: 15mJ/cm2, rep. rate: 200Hz, pulse duration: 20ns; tested at Institut für Photonische Technologien (IPHT) Jena |
| *** | Energy density: 20mJ/cm2, rep. rate: 50Hz, pulse duration: 20ns; tested at Institut für Photonische Technologien (IPHT) Jena |
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