Germanium Wedged Windows

30 arcminute Wedge
Eliminate Etalon Effects and Prevent Cavity Feedback
Uncoated and AR-Coated Germanium Substrates
Custom Options Available

Back Reflections from Wedges Are not Collinear with the Incident Beam
(Drawing not to Scale)

WW91050

Ø1"

WW90530-E3

Ø1/2"

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Overview
Graphs
Feedback
Window Guide

Wedged Window Selection Guide
Wavelength Range	Substrate Material
180 nm - 8.0 µm	Calcium Fluoride (CaF₂)
185 nm - 2.1 μm	UV Fused Silica
200 nm - 5.0 µm	Sapphire
200 nm - 6.0 µm	Magnesium Fluoride (MgF₂)
200 nm - 11 µm	Barium Fluoride (BaF₂)
250 nm - 1.6 µm	UV Fused Silica for 45° AOI
350 nm - 2.0 μm	N-BK7
600 nm - 16 µm	Zinc Selenide (ZnSe)
1.2 - 8.0 µm	Silicon (Si)
2.0 - 16 µm	Germanium (Ge)
V-Coated Wedged Windows

Features

30 Arcmin Wedged Windows
Ø1/2" and Ø1" Germanium Windows Available
Available Uncoated (2.0 - 16 µm) or with -E3 Broadband AR Coating (7 - 12 µm)
Custom AR Coatings and Sizes Available by Contacting Tech Support

Thorlabs offers Ø1/2" and Ø1" wedged germanium (Ge) windows that are uncoated or AR-coated for 7 - 12 µm. These wedged optics eliminate fringe patterns and can be used to help avoid cavity feedback. Windows are useful for protecting a laser output from environmental effects and for beam sampling applications.

Due to its broad transmission range (2.0 - 16 µm) and opacity in the visible portion of the spectrum, germanium is well suited for IR laser applications. As shown in the Graphs tab, this substrate also acts as a longpass filter for wavelengths greater than 2 µm. In addition, germanium is inert to air, water, alkalis, and acids (except nitric acid). Germanium's transmission properties are highly temperature sensitive; in fact, the absorption becomes so large the material is nearly opaque at 100 °C and completely non-transmissive at 200 °C.

When handling optics, one should always wear gloves. This is especially true when working with germanium, as dust from the material is hazardous. For your safety, please follow all proper precautions, including wearing gloves when handling this material and thoroughly washing your hands afterward.

In addition to the germanium wedged windows offered here, Thorlabs also offers wedged windows with other substrate materials (see the selection guide above and to the right). Wedged Laser Windows with AR coatings centered around common lasing wavelengths and wedged Beam Samplers with broadband AR coatings on only one face are also available. Additionally, wedged windows with our standard AR coatings or custom sizes and thicknesses are available; please contact Tech Support for more information. We also supply planar windows with a variety of substrate materials and coating options. We also supply planar windows with a variety of substrate materials and coating options.

All of these germanium wedged windows can be ordered uncoated or with a 7 - 12 µm AR coating (designated as -E3).

Thorlabs' high-performance -E3 broadband AR coating has an average reflectance of less than 1.0% (per surface) across its specified wavelength range (denoted by the shaded blue area in the Coating graph below). The AR coating provides good performance for angles of incidence (AOI) between 0° and 30° (0.5 NA). The substrate transmission graph below shows the transmission of light through an uncoated Ge substrate. Please contact Tech Support to order optics with custom coatings or sizes.

Uncoated Ge Window

Click to Enlarge
Click for Raw Data
This graph shows the full scale measured transmission of an uncoated germanium window at normal incidence.

Click to Enlarge
Click for Raw Data
This graph shows the measured transmission of an uncoated germanium window at normal incidence in the visible wavelength range. The values reported in the visible and near infrared are limited by the noise floor of the spectrometer used. Please note that out-of-band transmission is not monitored during production and will vary from lot to lot.

Ge Window, AR Coated for 7 - 12 µm

Click to Enlarge
Click for Raw Data
This plot gives the measured reflectance (per surface) at normal incidence of our AR-coated germanium window. The average reflectance is <1.0% per surface within the shaded wavelength range of 7 µm - 12 µm.

Click to Enlarge
Click for Raw Data
Shown above is a graph of the measured transmission of a 5 mm thick AR-coated germanium substrate. The blue shaded region denotes the 7 - 12 μm spectral range where we suggest using these Ge wedged windows. For this wavelength range, the measured transmission is in excess of 90%.

Posted Comments:

Mohammed Alshehri (posted 2023-01-22 20:04:25.69)

Dear ThroLabs theam, Hope you are doing well. This is Mohammed Alshehri from NCMS. I am enquiring about WW91050-E3 product, Is it both side coating? We are looking for wedge germanioum with AR coating with one surface coating and the other is Grinding surface with reflection less than 1 %. Many thanks Best regards, Mohammed Alshehri. mfshehri@ncms.sa

ksosnowski (posted 2023-02-03 05:49:35.0)

Hello Mohammed, thanks for reaching out to Thorlabs. For WW91050-E3 both surfaces have the same AR coating. Surface S2 also has a 30 arcmin wedge angle. Over the 7 - 12 µm range, the average reflectance for both S- and P- states is <1% per surface, and the average transmission is >94% for the whole window. The Reflection and Transmission plots and raw data can be accessed on the Graphs tab of this page. I have reached out directly to discuss this further.

Window Selection Guide (Table Sorted by Wavelength)
Substrate and Window Type	Wavelength Range	Available AR Coatings	Reflectance over AR Coating Range^a	Transmission Data	Reflectance Data
Calcium Fluoride (CaF₂): Flat or Wedged	180 nm - 8.0 μm	Uncoated	-	Raw Data	-
Calcium Fluoride (CaF₂): Flat or Wedged	180 nm - 8.0 μm	-D Coating, 1.65 - 3.0 µm	R_avg < 1.0%; R_abs < 2.0% at 0° AOI	Raw Data	Raw Data
UV Fused Silica: Flat, Wedged, V-Coated Flat, or V-Coated Wedged	185 nm - 2.1 μm	Uncoated (Flat or Wedged)	-	Raw Data	-
		-UV Coating, 245 - 400 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C3 Coating, 261 - 266 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C6 Coating, 350 - 450 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-A Coating, 350 - 700 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-B Coating, 650 - 1050 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C Coating, 1050 - 1700 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
Sapphire: Flat or Wedged	200 nm - 5.0 μm	Uncoated	-	Raw Data	-
		-D Coating, 1.65 - 3.0 µm	R_avg < 1.0% at 0° AOI	Raw Data	Raw Data
		-E1 Coating, 2.0 - 5.0 µm	R_avg< 1.50%, R_abs< 3.0% (per Surface, 2.0 - 5.0 µm); R_avg < 1.75% (per Surface, 2.0 - 4.0 µm) at 0° AOI	Raw Data	Raw Data
Magnesium Fluoride (MgF₂): Flat or Wedged	200 nm - 6.0 μm	Uncoated	-	Raw Data	-
Barium Fluoride (BaF₂): Wedged (Flat BaF₂ Windows Available Below)	200 nm - 11 µm	Uncoated	-	Raw Data	-
	200 nm - 11 µm	-E1 Coating, 2 - 5 µm	R_avg < 1.25%; R_abs < 2.5% at 0° AOI	Raw Data	Raw Data
UV Fused Silica, for 45° AOI: Flat or Wedged	250 nm - 1.6 µm	Coating for 250 nm - 450 nm	R_avg < 1.0% at 45° AOI	Raw Data
		Coating for 350 nm - 1100 nm	R_avg < 2.0% at 45° AOI	Raw Data
		Coating for 400 nm - 700 nm	R_avg < 1.0% at 45° AOI	Raw Data
		Coating for 600 nm - 1700 nm	R_avg < 1.5% at 45° AOI	Raw Data
		Coating for 700 nm - 1100 nm	R_avg < 1.0% at 45° AOI	Raw Data
		Coating for 1200 nm - 1600 nm	R_avg < 1.0% at 45° AOI	Raw Data
Potassium Bromide (KBr): Flat	250 nm - 26 µm	Uncoated	-		-
Infrasil^®: Flat	300 nm - 3 µm	Uncoated	-	Raw Data	-
N-BK7: Flat, Wedged, V-Coated Flat, or V-Coated Wedged	350 nm - 2.0 μm	Uncoated (Flat or Wedged)	-	Raw Data	-
		-A Coating, 350 - 700 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C7 Coating, 400 - 700 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C10 Coating, 523 - 532 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C11 Coating, 610 - 860 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-B Coating, 650 - 1050 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C13 Coating, 700 - 1100 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		C14 Coating, 1047 - 1064 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C15 Coating, 523 - 532 nm & 1047 - 1064 nm (V-Coated)	R_avg < 0.5% at 0° AOI	-	Raw Data
		-C Coating, 1050 - 1700 nm (Flat or Wedged)	R_avg < 0.5% at 0° AOI	-	Raw Data
Zinc Selenide (ZnSe): Flat or Wedged	600 nm - 16 µm	Uncoated	-	Raw Data	-
		-D Coating, 1.65 - 3.0 µm	R_avg < 1.0%; R_abs < 2.0% at 0° AOI	Raw Data	Raw Data
		-E4 Coating, 2 - 13 µm (Only Flat)	R_avg < 3.5%; R_abs < 6% at 0° AOI	Raw Data	Raw Data
		-E2 Coating, 4.5 - 7.5 µm (Only Flat)	R_avg < 1.0%; R_abs < 2.0% at 0° AOI	Raw Data	Raw Data
		-E3 Coating, 7 - 12 µm (Only Wedged)	R_avg < 1.0%; R_abs < 2.0% at 0° AOI	Raw Data	Raw Data
		-G Coating, 7 - 12 µm (Only Flat)	R_avg < 1% at 0° AOI	Raw Data	Raw Data
Silicon (Si): Flat or Wedged	1.2 - 8.0 μm	Uncoated	-	Raw Data	-
		-E1 Coating, 2 - 5 µm (Only Wedged)	R_avg < 1.25%; R_abs < 2.5% at 0° AOI	Raw Data	Raw Data
		-E Coating, 3 - 5 µm (Only Flat)	R_avg < 2% at 0° AOI	Raw Data	Raw Data
Germanium (Ge): Flat or Wedged	1.9 - 16 μm	Uncoated, 2.0 - 16 μm	-	Raw Data	-
		-C9 Coating, 1.9 - 6 µm (Only Flat)	R_avg < 2% at 0° AOI	Raw Data	Raw Data
		-G Coating, 7 - 12 µm (Only Flat)	R_avg < 1% at 0° AOI	Raw Data	Raw Data
		-E3 Coating, 7 - 12 µm (Only Wedged)	R_avg < 1.0%; R_abs < 2.0% at 0° AOI	Raw Data	Raw Data
Barium Fluoride (BaF₂): Flat (Wedged BaF₂ Windows Available Above)	2 - 5 μm	-E Coating, 2 - 5 µm	R_avg < 1.25% at 0° AOI	Raw Data	Raw Data

Reflectance is given per surface and each window is coated on both sides.

Germanium Wedged Windows, Uncoated

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Item #	WW90530	WW91050
Wedge Angle	30 ± 10 arcmin
Diameter	1/2" (12.7 mm)	1" (25.4 mm)
Diameter Tolerance	+0.0 / -0.2 mm
Thickness	3.0 mm	5.0 mm
Thickness Tolerance	±0.1 mm
Clear Aperture	≥Ø11.43 mm	≥Ø22.86 mm
Surface Flatness^a	≤λ/2 Over Central Ø5 mm ≤λ Over Entire Clear Aperture	≤λ/2 Over Central Ø10 mm ≤λ Over Entire Clear Aperture
Surface Quality	40-20 Scratch-Dig
Wavelength Range	2.0 - 16 µm (Uncoated)
Substrate	Germanium^b
Transmission Data (Click for Graph)	Raw Data

Measured at 633 nm
Click Link for Detailed Specifications on the Substrate

Germanium Wedged Windows, AR Coating: 7 - 12 µm

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Item #	WW90530-E3	WW91050-E3
Wedge Angle	30 ± 10 arcmin
Diameter	1/2" (12.7 mm)	1" (25.4 mm)
Diameter Tolerance	+0.0 / -0.2 mm
Thickness	3.0 mm	5.0 mm
Thickness Tolerance	±0.1 mm
Clear Aperture	>Ø11.4 mm	>Ø22.9 mm
Surface Flatness^a	≤λ/2 Over Central Ø5 mm ≤λ Over Entire Clear Aperture	≤λ/2 Over Central Ø10 mm ≤λ Over Entire Clear Aperture
Surface Quality	40-20 Scratch-Dig
AR Coating Range	7 µm - 12 µm (-E3 Coating)
Reflectance over AR Coating Range^b	R_avg < 1.0% (per Surface) R_abs < 2.0% (per Surface) Both Sides are Coated
Transmission over AR Coating Range^b	T_avg > 94% T_abs > 90%
Reflectance Data (Click for Graph)	Raw Data
Substrate	Germanium^c
Transmission Data (Click for Graph)	Raw Data

Measured at 633 nm
For Normal Incidence
Click Link for Detailed Specifications on the Substrate