wavelengths
 

Low GDD mirrors

After having managed to produce short laser pulses, it is necessary to propagate these pulses without disturbing the temporal beam profile. This is the moment where low dispersive beam steering mirrors enter the game.

Often metal mirrors like gold or special enhanced silver mirrors are the most economical solution while having low dispersion.

The major drawbacks of these mirrors are limited reflectivity and higher absorption los­ses, which may cause problems in applications with high average power.

Alternatively dielectric mirrors can be optimi­zed for low GDD. They offer very low losses avoiding thermal problems but normally have a near-zero GDD only for a limited spectral bandwidth. To overcome this, it is possible to make use of the concept of chirped mirror pairs.

In general, the difference in the refractive index of the applied coating materials determines the spectral width of the low GDD. The greater the difference, the higher the possible bandwidth.

Every coating material has a fixed optical band gap value. The higher the refractive index, the lower the value. Unfortunately, this is also linked to the LIDT and a low optical band gap correlates with a low LIDT.

Low-GDD-miorrsTherefore, spectral broadband low GDD mirrors come along with a lower LIDT compared to ones with a narrower spectral width. For example, this diagram shows the GDD-curves of two mirrors which have the same coating design but use different standard coating materials.

IBS offers extended strategies to deposit more complex designs with improved LIDT and the highest possible spectral width for low GDD mirrors.

All low GDD coatings can be designed on customer request, see examples:

Examples

If not mentioned otherwise, all values and diagrams are given

... for the standard substrate material used in the described wavelength area (mostly Fused Silica or CaF2).

... without consideration of the rear surface.

... with EBE coating technique for a good cost-performance ratio.

Customized coatings are available for all types.

 

–––– dashed lines show the zoomed curve with the stated magnification

HR 500–530 nm / 45° s+p low GDD
[B-18399]HR 500–530 nm / 45° s+p low GDD

500–530 nm: Rs,p > 99.5%; target | GDD (R) | < 20 fs²; 515 nm: Rs,p > 99.8% (IBS-coating)

HR 760–910 nm / 45°p low GDD
[B-12162]HR 760–910 nm / 45°p low GDD

760–910 nm: Rp > 99.8%; | GDD (Rp) | < 50 fs² (IBS-coating)

Please note: Optimized for highest power in ultrashort pulsed regime with > 0.9 J/cm² at 42 fs, 1 kHz. Developed for HAPLS at ELI Beamlines.

HR 770–850 nm / 44-46° p low GDD
[B-16700]HR 770–850 nm / 44-46° p low GDD

770–850 nm: Rs > 99.9%, Rp > 99.8%; | GDD (Rs,p) | < 50 fs² (IBS-coating)

R 99.5% 990–1090 nm / 0° low GDD
[B-12042]R 99.5% 990–1090 nm / 0° low GDD

990–1090 nm: T ±0.15%; | GDD (R) | < 10 fs² (IBS-coating)

HR 1020–1040 nm / 0–10° low GDD
[B-11072]HR 1020–1040 nm / 0–10° low GDD

1020–1040 nm: R > 99.9%; | GDD (R) | < 20 fs² (IBS-coating)

HT 970–982 nm T 7.5% 1035–1055 nm / 0° low GDD
[B-11872]HT 970–982 nm T 7.5% 1035–1055 nm / 0° low GDD

970–982 nm: R < 5%; 1035–1055 nm: R ±1% (IBS-coating)

HR 1950–2200 nm / 45° p low GDD
[B-17475]HR 1950–2200 nm / 45° p low GDD

1950–2200 nm: Rp > 99.9% (IBS-coating)

Ag enhanced 450–1000 nm
[B-11437]Ag enhanced 450–1000 nm

450–1000 nm: R > 90%; Ravg > 97%

 
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