Chirped mirrors and matched pairs
One can think of a chirped mirror as a Bragg mirror where the thickness of the layers slowly increases or decreases from bottom to top, so that the different “colours” are reflected at different depths resulting in different group delays which gives a non-zero GDD.
There are unavoidable residual GDD oscillations of such mirrors. If necessary they can be suppressed for example by using chirped mirror pairs where the oscillations of two different mirrors cancel each other out.
It is possible to produce chirped mirrors spanning more than one optical octave and having extra features like a high transmission pumping pass band.
LASEROPTIK's cooperation with leading research institutes in the field of ultrashort lasers and frequency combs helps to generate new results about the producibility of complex GDD coatings of which some findings are published.*
* Chia, S.-H., Cirmi, G., Fang, S., Rossi, G. M., Mücke, O. D., Kärtner, F. X., Two-octave-spanning dispersion-controlled precision optics for sub-optical-cycle waveform synthesizers, in: Optica, Vol. 1 (2014), Iss. 5, pp. 315-322
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
532 nm: T > 95%; 650-1100 nm: R > 99.9%; 780-1010 nm: GDD (R) = -88 → 0 fs² ±50 fs² (IBS-coating)
730-930 nm: Ravg > 99.9%, GDD ±40 fs² vs. theoretical curve (IBS-coating)
Two examples for chirped mirror pairs
target specifications for a mirror pair, best effort (IBS-coating):
532 nm: T > 98%; 675-975 nm: Rp > 99.9%, GD (R)-ripple < 2 fs
700-900 nm: Ravg > 99.9%; 710-860 nm: GDD ±10 fs² (IBS-coating)
Example for chirped mirror pairs with combination of positive and negative GDD
A combination of positively and negatively chirped mirrors gives low average dispersion while having significantly lower absorption losses than metal mirrors.
830-1230 nm: R > 99.8%, GD = const ±3 fs, GDD = 0 ±30 fs² (IBS-coating)
Every coating type can be optimized
• substrate material
• angle of incidence
• GDD value
Alternatively we can create
a totally new design for you.