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Low-GDD Ultrafast Mirrors for 700 - 930 nm
UM15-45A Ø1.5" Mirror
Thorlabs' low group delay dispersion (GDD) mirrors feature a coating designed for high reflectance in the 700 nm - 930 nm wavelength range and use at a 45° angle of incidence (AOI). These mirrors are ideal for Ti:Sapphire femtosecond pulsed lasers where pulse broadening is a concern, as well as imaging applications such as two photon microscopy. They offer an ideal combination of greater than 99% reflectance and less than |30 fs2| GDD; for details, please see the Graphs tab.
These mirrors are available in four different diameters: Ø1/2", Ø1", Ø1.5", or Ø2". The Ø1.5" version is ideal for use with amplified Ti:Sapphire laser systems, as it provides more surface area than a Ø1" mirror for expanded high-power beams while providing a more compact footprint than a Ø2" mirror.
The edge of each optic is engraved with the item number and an arrowhead pointing to the coated surface. The back surface of the Ø1/2", Ø1", and Ø1.5" mirrors is polished so that the small percentage of light that leaks through the reflective coating may be used for applications such as power monitoring. The fine ground back surface of the Ø2" mirror is ideal for use with higher power lasers, as the light passing through the mirror will be diffusely scattered.
Our low-GDD coating offers the highest reflectance of any of our mirrors for the Ti:Sapphire wavelength range. For a general comparison of the performance of our low-GDD mirrors, ultrafast-enhanced silver mirrors, standard protected silver mirrors, and broadband dielectric mirrors, please see the Mirror Comparison tab.
In addition to the low-GDD mirrors here, Thorlabs also offers low-GDD mirrors for various other wavelength ranges. For our full selection of optics for ultrafast applications, please see the Ultrafast Optics tab.
The graph on the left below shows measured results of the reflectance as a function of wavelength for both s- and p-polarizations. The graph on the right shows theoretical results for the group delay dispersion and represents the designed performance of our 700 nm - 930 nm low GDD coating. Both plots are for 45° AOI.
Click to Enlarge
Click for Raw Data
The shaded region represents the specified wavelength range where the absolute RS > 99%. Please note that the reflectance outside of this specified region is typical and can vary from lot to lot, especially where the reflectance is fluctuating or sloped.
This tab compares four of Thorlabs' coatings for the Ti:Sapphire wavelength range: our low-GDD dielectric coating for 700 - 930 nm, our ultrafast-enhanced silver coating, our standard protected silver coating, and our broadband dielectric -E02 coating.
The Protected Silver Coating offers the widest spectral range and minimal dependence on the angle of incidence. However, its reflectance at typical Ti:Sapphire wavelengths is somewhat lower than our low-GDD dielectric and ultrafast-enhanced silver coatings.
Our -E02 Broadband Dielectric Mirror Coating has resonance structures within the dielectric coating layers. These structures cause ripples in the group delay dispersion and can furthermore vary strongly between coating runs. While these variations do not impact CW performance, when an ultrafast laser pulse hits such a mirror, the pulse is strongly distorted. Thorlabs' low-GDD dielectric coating and the dielectric overcoat on our ultrafast-enhanced silver mirrors are designed in such a way that there is no resonance inside the layers, thereby maintaining smooth dispersion and reflectance across the design wavelength range.
Thorlabs offers a wide selection of optics optimized for use with femtosecond and picosecond laser pulses. Please see below for more information.