Low-GDD Ultrafast Mirrors for 700 - 930 nm

UM10-0A

(Ø1", 0° AOI)

UM20-45A

(Ø2", 45° AOI)

UM05-0A

(Ø1/2", 0° AOI)

Application Idea

UM15-45A Ø1.5" Mirror
in a POLARIS-K15S4 Mount

UM15-45A

(Ø1.5", 45° AOI)

Ideal for Ti:Sapphire Lasers
High Reflectance Over 720 - 900 nm (0° AOI) or 700 - 930 nm (45° AOI)
Group Delay Dispersion: |GDD| < 30 fs²

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Overview
Graphs
Mirror Comparison
Feedback
Ultrafast Optics

Features

Low Group Delay Dispersion: |GDD| < 30 fs²
Ideal for Pulses Shorter than 250 fs
Reflectance Greater than 99%
Designed for 0° or 45° Angle of Incidence (AOI)
Sizes Available:
- For 0° AOI: Ø1/2" or Ø1"
- For 45° AOI: Ø1/2", Ø1", Ø1.5", or Ø2"

Thorlabs' Low Group Delay Dispersion (GDD) Mirrors offer an ideal combination of greater than 99% reflectance and |GDD| less than 30 fs². These mirrors are ideal for Ti:sapphire femtosecond lasers where pulse broadening is a concern, as well as imaging applications such as two photon microscopy. Item #s ending in -0A are designed for use at 0° angle of incidence (AOI) with wavelengths 720 nm - 900 nm, while Item #s ending in -45A are designed for use at 45° AOI with wavelengths from 700 nm - 930 nm. The dielectric coating is applied with an ion-beam-sputtering (IBS) technique, providing a highly controlled and durable dielectric thin film coating. Please see the Graphs tab for reflectance and GDD data.

The low-GDD mirrors for 0° AOI are available in 1/2" or 1" diameters. The low-GDD mirrors for 45° AOI 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.

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.

UMxx-0A Low-GDD Mirrors for 720 - 900 nm at 0° AOI

Click to Enlarge
Click for Raw Data
This graph shows the theoretical reflectance as a function of wavelength. Since these mirrors are designed for normal incidence, the reflectance does not vary with polarization. The shaded region represents the specified wavelength range where the absolute reflectance is >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.

Click to Enlarge
Click for Raw Data
This graph shows theoretical results for the group delay dispersion (GDD). The shaded region represents the 720 nm - 900 nm wavelength range for which GDD is specified. Since these mirrors are designed for normal incidence, the GDD does not vary with polarization.

UMxx-45A Low-GDD Mirrors for 700 - 930 nm at 45° AOI

Click to Enlarge
Click for Raw Data
This graph shows the measured reflectance as a function of wavelength for both s- and p-polarizations. The shaded region represents the specified wavelength range where the absolute R_S > 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.

Click to Enlarge
Click for Raw Data
This graph shows theoretical results for the group delay dispersion (GDD). The shaded region represents the 700 - 930 nm wavelength range for which GDD is specified. The GDD values fluctuate rapidly outside of the specified wavelength range for s-polarized light.

This tab compares Thorlabs' mirror coatings recommended for the Ti:sapphire wavelength range: our 720 - 900 nm low-GDD dielectric with 0° angle of incidence (AOI), our 700 - 930 nm low-GDD dielectric with 45° AOI, our ultrafast-enhanced silver, our standard protected silver, and our broadband dielectric -E02 coatings.

Qualitative Comparison
Our Low-GDD Dielectric Coatings and Ultrafast-Enhanced Silver Coating are specifically designed for femtosecond Ti:sapphire lasers. The low-GDD dielectric coatings provide the highest reflectance, making them suitable for laser cavities, while the ultrafast-enhanced silver coating provides slightly lower reflectance and a slightly broader wavelength range. Each offers low group delay dispersion of |GDD| < 30 fs² or better.

The Protected Silver Coatings offer the widest spectral range and minimal dependence on the angle of incidence. However, their reflectance at typical Ti:sapphire wavelengths is somewhat lower than our low-GDD dielectric and ultrafast-enhanced silver coatings, and the GDD is not specified.

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 coatings 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.

Specs Comparison
The table below summarizes the reflectance, spectral range, and group delay dispersion of the different coatings.

Mirror Coating	Item # Suffix	Angle of Incidence	Spectral Range	Reflectance	Group Delay Dispersion
Low-GDD Dielectric Coatings	-0A	0°	720 - 900 nm	R > 99%	\|GDD\| < 30 fs²
Low-GDD Dielectric Coatings	-45A	45°	S-Pol: 700 - 930 nm P-Pol: 730 - 870 nm	R_s > 99% R_p > 99%	S-Pol: \|GDD\| < 30 fs² P-Pol: \|GDD\| < 30 fs²
Ultrafast-Enhanced Silver Coating	-AG	45°	750 - 1000 nm	R_s > 99.0% R_p > 98.5%	S-Pol: \|GDD\| < 20 fs² P-Pol: \|GDD\| < 30 fs²
Protected Silver Coatings	-P01	0° - 45°	450 nm - 20 µm	R_avg > 97.5% for 450 nm - 2 µm R_avg > 96% for 2 - 20 µm	Not Specified^a,b	-
Protected Silver Coatings	-P02	0° - 45°	450 nm - 20 µm	R_avg > 97% for 450 nm - 2 µm R_avg > 95% for 2 - 20 µm	Not Specified^a,b	-
Broadband Dielectric Coating	-E02	0° - 45°	400 - 750 nm	R_avg > 99%	Not Specified^b	-

While a bare silver coating has almost no dispersion, some silver mirrors have a dielectric coating which can increase the dispersion, especially when the dielectric coating is used to enhance spectral features. Our protected silver mirrors feature such a dielectric coating for protection of the fragile silver coating.
Our standard -P01, -P02, and -E02 coated mirrors are not specified for ultrafast applications, so we do not quantify their GDD from coating run to coating run. In contrast, our -0A, -45A, and -AG coated mirrors are guaranteed to provide their specified GDD values.

Posted Comments:

Shaogang Yu (posted 2020-08-25 11:24:26.863)

你好，我向贵司购买的UM10-45镜子，发现有很大一部分光透过，请问这是什么原因了？我是用的飞秒光脉宽是10fs，功率为600mW。

YLohia (posted 2020-08-25 10:18:11.0)

Hello, thank you for contacting Thorlabs. An applications engineer from our team in China will contact you directly.

Brennan Peterson (posted 2019-09-05 13:03:53.227)

Hello, Can you provide the coating type (IBS or ebeam) to understand the damage behavior.

YLohia (posted 2019-09-05 02:35:59.0)

Hello, thank you for contacting Thorlabs. Most of our low dispersion mirror coatings, including the -45A, are IBS.

Volker Sonnenschein (posted 2019-06-13 07:55:32.9)

How accurate is the Reflectance curve provided for these mirrors? As i doubt it is truly up to 99.996% as indicated in the excel sheet, i wonder how much absorption+scatter should be subtracted from the reflectivity value.

asundararaj (posted 2019-06-22 11:16:01.0)

Thank you for contacting Thorlabs. The reflectance curves on the website are theoretical and don't account for absorption or scatter. We only specify 99% reflectance because we can confidently say that the coating has significantly less than 1% loss to scatter and absorption.

slm9 (posted 2014-08-22 11:23:26.39)

Dear Thorlabs-Team Do you have some specs for this coating if this mirror will be used under AOI 0°? I would like to know the spectral shift and the low GDD behavior @AOI 0°. Thanks and with best regards Markus

jlow (posted 2014-09-18 02:07:45.0)

Response from Bweh at Thorlabs USA: We have theoretical plots for the reflectivity and GDD when used at 0 deg in comparison to 45 deg. Our European office will followup with you by email regarding this.

oliver.sandig (posted 2014-06-08 11:48:35.417)

Hallo, ich suche ein Ultrafast-Spiegel der reflektierend für 800nm und transparent für 400nm ist, oder umgedreht. Können Sie mir dafür ein Spiegel empfehlen? Vielen Dank, Oliver Sandig

besembeson (posted 2014-06-12 05:05:59.0)

A Response from Bweh at Thorlabs Newton-USA: Thanks for contacting Thorlabs. We don't carry such an ultrafast mirror at the moment that will reflect 400nm and transmit 800nm or vice versa. We do have dual band 400nm and 800nm high reflectivity ultrafast mirrors: (http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3179). I am curious about your application so I will contact you through our Germany office to find out more, and to determine if another stock item may work or if we have to look into a special coating for your application.

theresa.bruemmer (posted 2014-02-10 10:52:39.893)

Do You have estimates on the damage threshold of these mirrors? Thanks, Theresa

besembeson (posted 2014-02-12 03:59:33.0)

Response from Bweh E. at Thorlabs: Hi Theresa, These mirrors are ideal for Ti:Sapphire femtosecond pulsed lasers. The coating on this should withstand 1.5W of 800nm ultra-fast pulse with durations as short as 50fs, and 300mW of 400nm ultra-fast pulses with durations as short as 50fs. These numbers are based on a minimum laser beam diameter of about 1.2mm. Note that Pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material (avalanche ionization). I will send you separate email requesting your laser characteristics to determine if this optic is suitable for your laser or not.

tcohen (posted 2013-01-15 12:09:00.0)

Response from Tim at Thorlabs to Neil: Thank you for your feedback. I will send you measured data to supplement the calculated data provided on the “Graphs” tab. We will continue to update our presentation with more data.

steve.u.smith (posted 2013-01-14 14:15:34.98)

Do you have the measured GDD curve to share to help me make a purchasing decision? Thanks Neil

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

Low-GDD Mirrors

355 - 445 nm	460 - 590 nm	700 - 930 nm	970 - 1150 nm	1400 - 1700 nm	1760 - 2250 nm

Dielectric Mirror	High-Power Mirrors for Picosecond Lasers	Metallic Mirrors

Dual-Band Dielectric Mirror, 400 nm and 800 nm	Ytterbium Laser Line Mirrors, 250 nm - 1080 nm	Ultrafast-Enhanced Silver Mirrors, 750 - 1000 nm	Protected Silver Mirrors, 450 nm - 20 µm	Unprotected Gold Mirrors, 800 nm - 20 µm

Deterministic GDD Beamsplitters	Low-GDD Harmonic Beamsplitters	Low-GDD Polarizing Beamsplitters	Low-GDD Pump-Through Mirrors	Dispersion-Compensating Optics

Beamsplitters & Windows, 600 - 1500 nm or 1000 - 2000 nm	Harmonic Beamsplitters, 400 nm and 800 nm or 500 nm and 1000 nm	Low-GDD, High Power, Broadband Polarizing Beamsplitter, 700 - 1100 nm	Pump-Through Mirrors, 1030 - 1080 nm and 940 - 980 nm	Dispersion-Compensating Mirrors, 650 - 1050 nm	Dispersion-Compensating Prisms, 700 - 900 nm

Low-GDD Ultrafast Mirrors, 720 - 900 nm, 0° AOI

Zoom

Item #	UM05-0A	UM10-0A
Design Wavelength Range	720 - 900 nm
Diameter	1/2" (12.7 mm)	1" (25.4 mm)
Diameter Tolerance	+0.00 / -0.10 mm
Clear Aperture	>80% of Diameter
Thickness	6.4 mm (0.25")	9.5 mm (0.37")
Thickness Tolerance	±0.20 mm
Reflectance	R > 99%
Angle of Incidence	0°
Group Delay Dispersion	\|GDD\| < 30 fs²
Laser Induced Damage Threshold^a	0.40 J/cm² (800 nm, 52 fs FWHM, S-Pol, 1000 Pulses)
Substrate	Fused Silica
Front Surface Flatness^b	λ/3	λ/10
Front Surface Quality	15-5 Scratch-Dig
Parallelism	≤3 arcmin
Back Surface	Polished

For ultrafast optics, the laser induced damage threshold (LIDT) is defined as the fluence (per pulse) that produces visible damage after a given number of pulses. LIDT values are not guaranteed in the ultrashort pulse regime. As such, they are provided as a service to customers.
At 632.8 nm Over Clear Aperture

Low-GDD Ultrafast Mirrors, 700 - 930 nm, 45° AOI

Zoom

Item #	UM05-45A	UM10-45A	UM15-45A	UM20-45A
Design Wavelength Range	700 - 930 nm
Diameter	1/2" (12.7 mm)	1" (25.4 mm)	1.5" (38.1 mm)	2" (50.8 mm)
Diameter Tolerance	+0.00 / -0.10 mm
Clear Aperture	>80% of Diameter
Thickness	6.4 mm (0.25")	9.5 mm (0.37")	12.0 mm (0.47")	12.0 mm (0.47")
Thickness Tolerance	±0.20 mm			±0.10 mm
Reflectance	R_s > 99% (700 - 930 nm) R_p > 99% (730 - 870 nm)
Angle of Incidence	45°
Group Delay Dispersion	\|GDD_s\| < 30 fs² (700 - 930 nm) \|GDD_p\| < 30 fs² (730 - 870 nm)
Laser Induced Damage Threshold^a	0.40 J/cm² (800 nm, 52 fs FWHM, S-Pol, 1000 Pulses)
Substrate	Fused Silica
Front Surface Flatness^b	λ/4	λ/6	λ/4	λ/2
Front Surface Quality	15-5 Scratch-Dig			20-10 Scratch-Dig
Parallelism	≤3 arcmin			≤5 arcmin
Back Surface	Polished			Fine Ground

For ultrafast optics, the laser induced damage threshold (LIDT) is defined as the fluence (per pulse) that produces visible damage after a given number of pulses. LIDT values are not guaranteed in the ultrashort pulse regime. As such, they are provided as a service to customers.
At 632.8 nm Over Clear Aperture