Highly-Dispersive Ultrafast Mirrors for Dispersion Compensation

Hi, my name is Tony Karam and I am the Laser Optics Product Line Manager for Ultrafast Optics at Edmund Optics. Highly-Dispersive Ultrafast Mirrors are designed to be used with lasers that have pico-, femto-, or atto-second pulse durations. These types of lasers are called ultrafast Lasers. Because of their extreme pulse duration, these ultrafast lasers ablate tissues and other materials with higher precision than previously used technology, like nanosecond lasers. As such, ultrafast lasers are used in medical applications to make procedures like corrective eye surgery safer by reducing the risk of infection and reducing patient recovery time. Ultrafast lasers are also used for advanced material processing and to micromachine small features with higher accuracy and efficiency than other types of lasers. In addition to the biomedical and material processing industries, Highly-Dispersive Ultrafast Mirrors are also used in a wide variety of other applications such as 3D printing of medical devices, nonlinear imaging, and spectroscopy. The broad energy bandwidth of ultrashort pulses is due to the uncertainty principle that arises from the inherent wave properties of photons, where the precision of time-energy is limited by the Fourier transform. As they travel, ultrafast pulses temporally distort. Hence, compression and dispersion-compensation are required when working with ultrafast lasers. Fortunately, Highly-Dispersive Ultrafast Mirrors can correct this dispersion with mirror coatings that feature large negative group delay dispersions and low loss over large bandwidths. Large group delay dispersion is achieved by combining and optimizing the effects from two simpler mirror coating technologies known as chirped mirrors and Gires-Tournois Interferometer mirrors. Traditional chirped mirrors achieve negative group delay dispersion by using the wavelength-dependent relation to penetration depth. However, this technology introduces wavelength-dependent GDD oscillations as well, similar to Fabry-Perot resonators and is only able to achieve limited negative GDD. Gires-Tournois Interferometer mirrors achieve angle-dependent negative group delay dispersion based on resonant cavity structures. However, this technology is only usable for a very narrow bandwidth and introduces third and higher order dispersion. Optimizing these two technologies allows for coatings with larger group delay dispersion values to be achieved, with lower losses and over a broader bandwidth, than traditional chirped mirrors or GTI mirrors, without increasing the thickness of multilayer coatings. For more information on Highly-Dispersive Ultrafast Mirrors and the applications in which they are used, visit www.edmundoptics.com/highly-dispersive-mirrors.