F₂ Lasers (157 nm)

High quality mirror substrates, windows and lenses of CaF₂ (193 nm excimer grade quality, HELLMA Materials GmbH)
Please note that the 157 nm excimer grade CaF₂ can no longer be offered. The market for this kind of material is too small compared to the huge effort necessary for the crystal manufacturers to test the material according to this quality standard. Thus, all LAYERTEC optics for F₂ lasers will be manufactured using 193 nm excimer grade material in the future.
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 like beam splitters and variable attenuators on request

Mirrors

Fig.1:Measured reflectance and transmittance spectra of mirrors for 157 nm

a)Laser mirror (AOI = 0°)

b)Turning mirror (AOI = 45°)

Fig.2:Measured reflectance spectra of standard output couplers with:
R = 50 % ±3 % and R = 25 % ±2 % (rear side uncoated)

Fig.3:Reflectance spectra of aluminum mirrors

a)Protected aluminum mirror

b)Enhanced aluminum mirror for 157 nm

Protected aluminum mirrors (optimized for 157 nm):
R = 74 % … 78 %
Dielectrically enhanced aluminum mirrors: up to R = 94 % at AOI = 0°
For more information on aluminum mirrors see page Front Surface Aluminum Mirrors (150 – 900 nm).

Table 1:Technical Data of Standard F₂ Laser Components

Coating	Spectral Performance	Lifetime Tests
HR (0°, 157 nm)	R = 92 % … 95 %	2 × 10⁸ – 1 × 10⁹ pulses*
HR (45°, 157 nm)	R = 90 % … 94 % (unpol. light)
PR (0°, 157 nm)	R = 50 % ±3 %	2 × 10⁸ – 1 × 10⁹ pulses*
PR (0°, 157 nm)	R = 25 % ±2 %	2 × 10⁸ – 1 × 10⁹ pulses*
AR (0°, 157 nm)	R = 0.3 % … 0.7 %
* Energy density 25 mJ/cm², repetition rate 800 Hz, pulse duration 15 ns; tested at COHERENT AG, München

Mirrors and separators for the 133 nm and 160 nm range are produced by coating techniques which were developed for F₂ laser coatings. For more information please see page Components for the Higher Harmonics of the Ti:Sapphire Laser (140 – 250 nm).