Low GDD Ultrafast Mirrors for 1760 nm - 2250 nm

  • High Reflectance Over 1760 nm - 2250 nm
  • Group Delay Dispersion < 30 fs2
  • Ideal for Femtosecond Thulium (Tm)
    and Holmium (Ho) Lasers





Application Idea

UM05-45D Low GDD Mirror in a
POLARIS-K05F1 Low-Distortion Mount
and Mounted with a POLARIS-CA1
Clamping Arm

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Item # UM05-45D UM10-45D
Design Wavelength Range 1760 - 2250 nm
Diameter 1/2" (12.7 mm) 1" (25.4 mm)
Diameter Tolerance +0.00 / -0.10 mm
Thickness 6.4 mm (0.25") 9.5 mm (0.37")
Thickness Tolerance ±0.20 mm
Clear Aperture >80% of Diameter
Reflectance Rs > 99% (1760 - 2250 nm)
Rp > 99% (1900 - 2050 nm)
Angle of Incidence 45°
Group Delay Dispersion |GDDs| < 30 fs² (1760 - 2250 nm)
|GDDp| < 30 fs² (1900 - 2050 nm)
Substrate Fused Silica
Front Surface Flatness λ/6 at 632.8 nm
Over Clear Aperture
λ/4 at 632.8 nm
Over Clear Aperture
Front Surface Quality 15-5 Scratch-Dig
Parallelism ≤3 arcmin
Back Surface Polished


  • Low Group Delay Dispersion: |GDD| <30 fs2
  • Ideal for Pulses Shorter than 250 fs
  • Reflectance Greater than 99%
  • Ø1/2" and Ø1" Mirrors Available

Thorlabs' Low Group Delay Dispersion (GDD) Mirrors feature a coating designed for high reflectance in the 1760 nm - 2250 nm range. The wavelength range is optimized for lasers around 2 µm in wavelength, such as thulium (Tm) and holmium (Ho) doped lasers. These mirrors are ideal for applications where pulse broadening is a concern and are designed for a 45° angle of incidence. The dielectric coating is applied with an ion-beam-sputtering (IBS) technique, providing a highly controlled and durable dielectric thin film coating.

These mirrors offer an ideal combination of greater than 99% reflectance and less than |30 fs2| GDD. For details, please see the Graphs tab.

Our low GDD mirrors are available with either a 1/2" or 1" diameter. The edge of each optic is engraved with the item number and an arrowhead pointing to the coated surface. The back surface of these 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.

In addition to these mirrors for 1760 - 2250 nm, 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 graphs below are measured and theoretical results of the reflectance and the group delay dispersion, respectively, at an AOI of 45°.

Click to Enlarge

Click for Raw Data
The shaded region represents the specified wavelength range where RS>99%.
Click to Enlarge

Click for Raw Data
The shaded region represents the specified wavelength range where S-Polarization GDD<|30 fs2|. The GDD values fluctuate rapidly outside of this region.

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Thorlabs offers a wide selection of optics optimized for use with femtosecond and picosecond laser pulses. Please see below for more information.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
UM05-45D Support Documentation
UM05-45DØ1/2" Low GDD Ultrafast Mirror, 1760 nm - 2250 nm, 45° AOI
UM10-45D Support Documentation
UM10-45DØ1" Low GDD Ultrafast Mirror, 1760 nm - 2250 nm, 45° AOI
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