Empty Glass Cells with Angled Windows

  • Empty UV Fused Silica Glass Cells for Spectroscopy
  • Ø1/2" or Ø1" Wedged Windows Angled at 11°
  • High Transmission in the UV Spectral Range
  • Custom Solutions Available


Empty UV Fused Silica Cell with
Ø1/2" Wedged Windows Angled at 11°


Empty UV Fused Silica Cell with
Ø1" Wedged Windows Angled at 11°

Sealed Windows Angled at 11°

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Inside Thorlabs: Scientific Glassblowing
Item # GC20 GC50
Cell Lengtha 20.0 ± 3.0 mm 50.0 ± 3.0 mm
Cell Outer Diameter 12.0 ± 0.2 mm 24.0 ± 0.2 mm
Cell Clear Aperture >Ø8.0 mm >Ø20.0 mm
Pressure <10-7 Torr to 5 psi at 25 °C
Fill Tube Length 90.0 mm
Fill Tube Outer Diameter 6.35 mm (0.25")
Window Angle 11.0° ± 1.0°
Window Item # WW40530 WW41050
Window Flatness λ
Window Wedge Angle 30 ± 10 arcmin
Window & Cell Substrate UV Fused Silicab
UVFS Transmission
(Click for Plot)
Diagram (Click to View)
  • Length of the center of the cell including the windows.
  • Click link for detailed specifications on the substrate.


  • Glass Cells for Spectroscopy Applications
  • Pair of Windows Angled at 11°
    • Keeps Stray Reflections out of Beam Path
    • Compensates for Beam Offset
  • Wedged Windows Eliminate Etalon Effects
  • Both Ends Include Ø1/2" or Ø1" Windows
  • UV Fused Silica Substrate for Cell and Windows
  • High Transmission in the UV Spectral Range (See Table to the Lower Right)
  • Available with One Tube for Filling
  • Custom Design and Manufacturing Services Available (Contact Tech Support)
  • Cells Compatible with our HT10K and TLK-H Resistive Foil Heaters

Thorlabs' Empty UV Fused Silica (UVFS) Cells with Angled Windows provide high transmission from 185 nm to 2.1 µm (see the table to the lower right for a graph of UVFS transmission). The windows are angled (as seen in the family image above) to ensure that stray reflections do not interfere with the beam path. Since the two windows are angled opposite to each other, any beam translation from the first window is compensated by the second window. To eliminate etalon effects, the windows have a 30 arcmin wedge. We also offer empty glass cells with vertical windows and threaded empty glass cells for a self-assembled set-up.

Cells are available with one fill tube which is useful when introducing a sample into the cell and sealing it off for measurements. These fill tubes have a 1/4" outer diameter and are compatible with Ø1/4" compression fittings; for more information see the Vacuum Seal tab. As shown in the video to the right, custom reference cells can be manufactured upon request, including different cell lengths, cell diameters, or fill tube configurations. Please contact Tech Support with inquiries.

Each cell is made from UVFS, a rugged material known to resist chipping and cracking, and has high transmission from 185 nm to 2.1 μm. The ends of each cell include either Ø1/2" or Ø1" UVFS wedged windows. All glass cells on this page can hold a vacuum below 10-7 Torr and withstand pressure up to 5 psi. The post-production cleaning process for these cells consists of an ultrasonic cleaning followed by a methanol rinse. The cell is then connected to a vacuum system and leak tested. The cells are not vacuum sealed when shipped; before using the cell in a vacuum setup, we advise users to follow a similar cleaning process for each cell.

These cells are commonly used in spectroscopic applications such as tunable diode laser calibration, stabilization of laser frequencies, and calibration of wavelength meters. Refer to the Application tab for a general overview of use with absorption spectroscopy. We also offer compact and Herriott multipass cells for gas absorption spectroscopy applications, as well as filled and sealed vapor and acetylene reference cells.

Mounting & Heating Options
The glass cells can be mounted in our V-Clamp Mounts, which are available in standard, kinematic, or Ø1.5" post-compatible versions. Please check that the cell diameter is supported by the mount. Our HT10K and TLK-H Resistive Foil Heaters can attach to the outside of the glass cells via adhesive backing.

Glass Cells Selection Guide
Empty Glass Cells Empty Glass Cells with Angled Windows Threaded Empty Glass Cells Vapor Reference Cells Acetylene Reference Cells Glass Cell Heaters
Glass Cell Mounted in V-Clamp
Click to Enlarge

Angled Windows Eliminate Etalon Effects
Glass Cell Mounted in V-Clamp
Click to Enlarge

Wedged Windows Seal Off the Empty Cell

Absorption Spectroscopy

The reference substance pumped into the glass cell is associated with a unique absorption spectrum that serves as its fingerprint. The contents of a reference cell can be determined via a linear absorption measurement (as depicted by the simplified schematic below). By scanning a tunable diode laser over a wavelength range and detecting light absorption with a photodetector, a series of peaks will be recorded, which is characteristic of the vapor inside the cell. Please note that we also offer pre-filled and sealed acetylene reference cells, as well as vapor reference cells with quartz or borosilicate substrates.

Reference Cell Setup
Animated Example of a Vacuum-Sealed System

Creating a Vacuum Seal with a KF Flange

Thorlabs' empty quartz cells can be used with our KF25-flanged components and accessories in order to manage gas flow in and out of the cell. The glass cells that are terminated with one or two Ø0.25" (Ø6.35 mm) fill tubes that can be inserted into the KF25C025 flange-to-compression-fitting adapter.

To input the cell into a vacuum system:

  1. Coat a cleaned and inspected KF25CR-F O-Ring in vacuum grease and place it on a base post or pipe.
  2. Place the KF25C025 flange-to-compression-fitting adapter on top of the O-ring and secure them with the KF25WNC wing nut clamp.
  3. Loosen and remove the knurled locking knob of the KF25C025 so its mating surface can be inspected and the included O-ring can be coated in vacuum grease. This will create a vacuum seal when the cell is inserted into the system.
  4. Loosely tighten the knurled locking knob and insert the fill tube of the borosilicate cell and tighten the knob by hand.

For an animated representation of the above process but using the KF25C050 flange-to-compression-fitting adapter, please see the video to the right.

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Empty Glass Cells with Angled Windows, One Fill Tube

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+1 Qty Docs Part Number - Universal Price Available
GC20 Support Documentation
GC20Empty Glass Cell with Angled Ø1/2" Fused Wedged Windows, 20.0 mm Long, One Fill Tube
GC50 Support Documentation
GC50Empty Glass Cell with Angled Ø1" Fused Wedged Windows, 50.0 mm Long, One Fill Tube