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OptiLayer:  Your Partner in Design and Post-Production Characterization of Optical Coatings

 

One-octave Dispersive Mirror

  • Spectral range: 550-1100 nm (one octave);
  • Substrate: Suprasil;
  • Layer Materials: SiO2, Nb2O5 described by Cauchy formula;
  • Incidence Angle 70, P-polarization;
  • Target Reflectance 100%;
  • Target GDD \(-40-10(\omega-\omega_0)\;fs^2\)
dispersive mirror
 dispersive mirror "Classical approach" (Gradual evolution with combination of thin Layer Removal) leads to oscillations in GDD.

It is mathematically proved that oscillations of GDD are inevitable. It means that it is required to find a way to suppress them or to reduce their effect on the output pulse characteristics. 

OptiLayer provides various tricks/design tools to solve this problem.

Approach 1: Phase optimization with floating constants:

Any given dependence \(GDD(\omega)\) can be integrated twice and converted to phase target:

\[ \varphi(\omega)=\int\limits_{\omega_0}^\omega\int\limits_{\omega_0}^{\omega_1}GDD(\omega_2)d\omega_2+C_1\omega+C_2 \]

\(C_1\) and \(C_2\) – arbitrary constants.

Merit function now depends on these constants:

\[ MF=F(d_1,...,d_m; C_1, C_2)\]

For any set of thicknesses \(\{d_1,...,d_m\}\) constants can be excluded from the merit function analytically, because \(F\) is quadratic function with respect to \(C_1\) and \(C_2\):

\[ \frac{\partial F}{\partial C_1}=0, \;\;\frac{\partial F}{\partial C_2}=0\]

Resulting merit function is optimized with needle optimization technique.

This approach can be applied to coatings of all types. Learn more...

Result: 69-layer one-octave dispersive mirror.

dispersive optical coating

group delay dispersion

 

Approach 2: Complimentary pairs

For dispersive mirror pair reflectance and GDD can be defined as:

\[ R_p=\sqrt{R_1\cdot R_2}; \;\; GDD_p=\frac{GDD_1+GDD_2}{2} \]

  • It is possible to achieve suppression of GDD oscillations if GDDs for each mirror are almost in anti-phase;
  • Production is extremely challenging since it is necessary to deposit precisely matching pair with extremely high accuracy;
  • Special procedures for reducing sensitivity of the designs to the production errors, i.e., in order to find more robust design;
  • It is possible to achieve pulse compression in the range up to 1.5 octave (400nm – 1200nm)

 dispersive mirror

Result: A pair of 72-layer and 70-layer dispersive mirrors (complimentary pair). Green and blue curves represent GDD of two diespersive mirrors and black curve shows resulting GDD

Easy to start

Icons 100x100 1OptiLayer provides user-friendly interface and a variety of examples allowing even a beginner to effectively start to design and characterize optical coatings.        Read more...

Docs / Support

Icons 100x100 2Comprehensive manual in PDF format and e-mail support help you at each step of your work with OptiLayer.

 

Advanced

Icons 100x100 3If you are already an experienced user, OptiLayer gives your almost unlimited opportunities in solving all problems arising in design-production chain. Visit our publications page and challenge page.

 

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