Molecules have specific absorption lines dependent on the molecular energy level transitions particular to the species. For gases these lines are also particularly accurately known (subpicometer), narrow, and insensitive to environmental conditions. A gas cell is simply a tube filled with a gas or gas mixture of known chemical and isotopic purity and pressure and may be used as is or coupled to fiber optic cables. They have been widely researched as wavelength standards and are the basis of NIST SRMs 2514, 2515, 2517, 2517A, and 2519.

Some examples of uses for gas cells include:

• Tunable laser calibration
• Sensing system calibration
• Reference for chemical detector or medical instrumentation
• Optical instrument calibration source (wavelength, dispersion, etc)

Wavelength References is an industry leader in providing a full breadth of NIST traceable gas cells in a number of configurations. They can be ordered coupled to fiber optic cables, with built in detectors, or as a bare absorption tube. Special requests are welcomed. Species include acetylene, hydrogen cyanide, carbon monoxide, water, hydrogen fluoride, methane, hydrogen chloride, ammonia, and mixtures. These species can provide subpicometer accuracy over full Telcordia environmental specification. Custom faceplate material is available for extended operation in the infared to >4 microns. Other species may be available on request.

• Acetylene ¹²C₂H₂ The acetylene cells are the equivalent of the NIST SRM 2517 and 2517A Wavelength Calibration Reference for 1510nm-1540nm. We can offer a variety of pressures that can be used to tailor the absorption width to the application. These fiber coupled gas cells are the smallest (4.7cm by 1.4cm by 1 cm) and lowest cost offered by Wavelength References. As an example for ordering:
  C2H2-12-M-F-200-FCAPC
  This would be a fiber coupled carbon 12 acetylene gas cell with 200 Torr pressure and FC/APC connectors.
• Hydrogen Cyanide H¹³CN The hydrogen cyanide cell is the equivalent of the NIST SRM 2519, Wavelength Calibration Reference for 1530nm-1560nm. This device covers the entire C-band. As an example for ordering : HCN-13-C-100-FCAPC This would be a fiber coupled carbon 13 hydrogen cyanide gas cell at 100Torr pressure and with FC/APC connectors. We also offer a NEW “mini” HCN cell with a 5cm absorption path. This much smaller cell has a peak absorption level of 1.2 dB as compared with the 16.5cm path standard HCN cell 3.2 dB peak absorption level.
• Carbon Monoxide ¹²CO and ¹³CO Carbon monoxide covers the L-band with the carbon 12 isotope covering from 1560nm to 1595nm and the carbon 13 isotope from 1595nm to 1630nm. These devices are in our 80cm path multipass housing which offers a compact 5 pass design only a little larger then our HCN cell.