In laser spectroscopy, researchers often need to measure the absorption coefficient of light in a gas, or some other effect resulting from the interaction of a gas with light, such as frequency-dependent phase changes. A gas cell is a gas chamber filled with a gas to which spectroscopy is applied, usually for laser absorption spectroscopy. It is typically formed of a transparent material, such as borosilicate, heat-resistant glass, or fused silica, and is cylindrical in shape. For wavelength reference or chemical analysis in spectroscopic devices like Fourier Transform Infrared (FTIR) spectroscopy and Laser Absorption Spectroscopy, Alfa Chemistry offers a variety of gas cells that can be customized (LAS).
Our Customization Capabilities
Two primary optical elements, a cylinder and a transmission window, are present in the gas chamber. Here are a few of our standard substrate choices for altering the cylinder and transmission window parts.
| Transmission window materials include | Sodium chloride (NaCl); Potassium bromide (KBr); Zinc selenide (ZnSe); Calcium fluoride (CaF2) |
| Cylinder materials include | Borosilicate; Pyrex; Soda lime float; Fused quartz; Other materials: aluminium |
All of the materials mentioned above have transmission windows that can pass light into the infrared band and transmit over a broad spectrum of wavelengths. Alfa Chemistry may offer you each of these windows separately, along with a little wedge to decrease interference.
The following details must be provided to us if the customer requests a custom reference gas chamber that is filled with the chosen gas or gas mixture.
Substrates for Transmissive Windows and Cylinders
The research team at Alfa Chemistry can collaborate with clients to find appropriate materials.
Gas Mixture and Desired Concentration
Methane (CH4), acetylene (AC), hydrogen cyanide (HCN), and ammonia (NH3) are typical gases used in reference cells (C2H2). We can provide other reference gases, so please ask for more information.
Path Length
This is the distance that the incident beam travels through the gas, which is typically categorized as short, long, or variable. We need to know the path length and if it is fixed or variable for the unique reference gas chamber.
A brief light path is sufficient for highly concentrated mixes, such as a reference cell filled entirely with methane. If the gas concentration is lower and usually given in parts per billion (ppb), a longer light path is required, for example, when measuring greenhouse gas levels in an air sample.
Depending on the exact needs, we may also offer gas cells with fixed or variable light ranges; the variable kind uses mirrors to expand the light range by reflecting the beam across the cell rather than allowing it to flow through directly.
In addition, Alfa Chemistry can provide cell types that are also used to accommodate vapors and liquids. For example, drilled cuvette windows can be used in removable cuvette holders that typically hold liquid samples.
Quality Assurance
- We test the transmission window's flatness, irregularity, transmission wavefront error, and other properties with an interferometer.
- Using a photometer, which can conduct spectral scans at various incidence angles and polarizations, we execute transmission and reflection scans.
- We can use the spectrometer to further test IR transmission.
- Prior to packaging, all optics are rigorously visually inspected, and our crew is highly trained to look for scratches and gouges as small as 10/5, which is crucial for laser applications.
If you need technical advice, please contact our technical team to learn more about our high-quality services.