ArF Lasers (193 nm)

Mirrors

Fig.1:Reflectance and transmittance spectra of mirrors for 193 nm

a)Resonator mirror (AOI = 0°)

b)Turning mirror (AOI = 45°, unpolarized light)

All-fluoride systems guarantee high reflectance and high damage thresholds
High quality mirror substrates, windows and lenses of CaF₂ (193 nm excimer grade, HELLMA Materials GmbH) and Fused Silica
Development and production of customer specific components such as beam splitters and variable attenuators on request

Fig.2:Reflectance spectra of output couplers with
R (0°, 193 nm) = 50 % ±3 % and
R (0°, 193 nm) = 25 % ±2 % (coated side only)

PR coatings with tolerances of:
- ±2 % for R = 10 % … 30 %
- ±3 % for R = 30 % … 75 %
- ±2 % for R = 75 % … 90 %
- ±1 % for R > 90 %
Single wavelength AR coating with residual reflectance values of:
- R < 0.25 % at AOI = 0° and
- R < 0.6 % at AOI = 45° (unpolarized light)
Broadband and multiple wavelength AR coatings

Fig.3:Reflectance spectra of aluminum mirrors.

a)Protected aluminum mirror optimized for 193 nm

b)Enhanced aluminum mirror for 193 nm, AOI = 45°

For more information on aluminum mirrors see page Front Surface Aluminum Mirrors (150 – 900 nm).

Table 1:Technical Data of Standard ArF Laser Components

Coating/Reflectance Fluoride Coating	Substrate	Damage Threshold*	Lifetime Test
AR (0°, 193 nm) R < 0.25 %	CaF₂	4 – 5 J/cm²	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	10¹⁰ pulses, no damage**
PR (0°, 193 nm) R = 50 %	CaF₂	2 – 3 J/cm²	10¹⁰ pulses**
HR (0°, 193 nm) R > 97 % (typically R > 98 %)	CaF₂	2 – 3 J/cm²	10¹⁰ pulses, no damage 4 × 10⁹ pulses*, no damage
HRu (45°, 193 nm) R > 97 % (typically R > 98 %)	CaF₂	2 – 3 J/cm²
* 1000-on-1, pulse duration 14 ns; measurements were performed at Laser Labor Göttingen, Laser Zentrum Hannover and at Friedrich Schiller University Jena
** Energy density 55 mJ/cm², repetition rate 1 kHz, pulse duration 15 ns; tested at COHERENT AG, München
*** Energy density 80 mJ/cm², repetition rate 1 kHz, pulse duration 12 ns; tested at COHERENT AG, München

Mirrors and separators for the 4^th harmonic of Ti:Sapphire lasers in the wavelength range around 200 nm are produced by coating techniques which were developed for ArF laser coatings. For more information please see page Components for the Higher Harmonics of the Ti:Sapphire Laser (140 – 250 nm).