DE19831392A1 - Two-range reflection reduction for the visible spectral range and a wavelength of: (248 +/- 15) NM - Google Patents

Abstract

The invention relates to a double-range reflection reducing coating for the visible spectral range which consists of nine layers. The reflection-reducing coating is also effective at a wavelength of lambda = (248 +/- 15) nm. The nine layers are made of a substrate containing quartz glass (SiO2); .373 M; .390 K; 2.086 M; .320 K; 1.124 M; 1.467 K; .689 M; .320 K; 1.044 M; and air: 1.00, where M is magnesium fluoride (MgF2) and K is aluminium oxide (Al2O3). The layer thicknesses are configured in quarter-lambda units and the reference wavelength is 300 nm for an angle of incidence of (0 +/- 15) degrees.

Description

aim

Representation of a reflection-reducing coating that both in the visible spectral range and for the Excimer wavelength (248 nm) works. It is in addition to note that the excimer laser is suitable for the application is a power laser for material processing. The Coating must therefore have a correspondingly high level of destruction have threshold.

Is based on a high quality coating of the lens surfaces ceases, this means that to achieve the required Minimum energies on the material to be processed with a laser higher power must be used. In the coated here Objective are eight lenses (equal to 16 glass-air surfaces) for constructive beam guidance from the laser source to the sample necessary. If the high-quality remuneration were now waived, this would result in a reflection loss of approx. 50% would stand. A laser with double power would have to be be used. Since acquisition and maintenance costs are one Excimer lasers rather disproportionately with the increase in output rise, it can be seen that the effort for an ent speaking remuneration of the components is worthwhile.

Another reason for using high-quality compensation layers is avoiding false light. Through uncontrolled re Flexions on the optical components can lead to a diffuse Backlights come on the sample that one of the Laser light intensity dependent defined material removal sword.

The simultaneous reduction in reflection for the visible spectrum allows the in-situ control of the beam guidance of the laser on the Sample and use everyone else in microscopy and imaging recording usual procedures.

Result

The two-range reflection reduction presented here meets the above requirements:

• - for the UV-compatible materials calcium fluoride, Lithium fluoride, quartz, quartz glass and other materia lien, whose refractive index at 248 nm is less than or equal to 1.6 is;
• - In this case, destruction thresholds of 3 J / cm ² for Suprasil and 4 J / cm ² for calcium fluoride are verified by measurement;
• - Fig. 1 shows the measured reflection reduction using Suprasil as an example;
• - The measured increase in transmission is shown in Fig. 2 on a 3 mm thick Suprasil disc coated on both sides.

solution

The layer system required for implementation consists of nine individual layers, which in turn consist of magnesium fluoride and aluminum oxide. Figures 3 and 4 show the calculations for GaF ₂ and SiO ₂ substrates. The dispersion is taken into account in the calculation for both the substrates and the layer materials. The thicknesses are given in lambda / 4 units.

The refractive indices may fluctuate by ± 0.02; the fat ones by ± 5%. The assumed angle of incidence is (0 ± 15 °).

Claims (2)

1. Two-region reflection reduction layer for the visible spectral range, characterized in that it is additionally effective for a wavelength of lambda = (248 ± 15) nm and has the following structure consisting of nine layers:
Substrate: quartz glass (SiO2)
.373M
.390 K
2,086 M
.320 K
1,124 m
1,467 K
.689M
.320 K
1,044 M
Air: 1.00,
where: M = magnesium fluoride (MgF2); K = aluminum oxide (Al2O3 :); Layer thicknesses in lambda / quarter units; Reference wavelength: 300 nm; Angle of incidence: (0 ± 15) degrees. 2. Two-region reflection reduction layer for the visible spectral range, characterized in that it is additionally effective for a wavelength of lambda = (248 ± 15) nm and has the following structure consisting of nine layers:
Substrate: calcium fluoride (CaF2)
.500 M
.320 K
2,086 M
.320 K
1,124 m
1,467 K
.570 M
.320 K
1,044 M
Air: 1.00,
where: M = magnesium fluoride (MgF2); K = aluminum oxide (Al2O3); Layer thicknesses in lambda / quarter units; Reference wavelength: 300 nm; Angle of incidence: (0 ± 15) degrees.