May 15 2014
A chirped mirror is a dielectric mirror that has chirped surfaces on it. Chirped spaces are spaces of varying depths for reflecting the light of varying wavelengths. These spaces are positioned between the dielectric layers or stacks.
Chirped mirrors that are robustly optimized are extremely useful in dispersion compensation in ultra-short pulse lasers.
In another type of chirped mirror, called the double chirped mirror, a multi-layered interference coating is used. As the bandwidth increases, the number of dielectric layers also needs to be increased.
Basic Principle
An ordinary dielectric mirror is capable of reflecting a single frequency of light. A dielectric mirror is a transparent material that is stacked as layers, having a depth equal to ¼th the wavelength of light to be reflected.
In chirped mirrors, layers of varying depths are stacked, in order to reflect the light of different wavelengths. The layers are stacked so that the entire range of wavelengths that are to be reflected are accommodated.
Light reflected off the deeper layers traverses longer distances than that reflected off the surface layers. A chirped mirror essentially modifies the relative times of wavefronts of different wavelengths.
Applications
Some of the typical applications of chirped mirrors are listed below:
- Compensation of chromatic aberration
- Mode-locking lasers
- Chirped pulse amplification
Sources and Further Reading