Source: FTIR.com

Understanding Gas and Vacuum Cells in Photonics

Introduction

In the field of photonics, the use of gas and vacuum cells is crucial for various applications, especially in laser spectroscopy. Gas cells are utilized to analyze the interaction of light with gases, measure absorption coefficients, and identify chemical species. On the other hand, vacuum cells are essential for optical trapping, high harmonic generation, and experiments requiring a controlled environment.

Gas Cells in Photonics

Gas cells are containers filled with gas, often with optical windows for injecting and extracting light. These cells are used in laser spectroscopy to measure absorption coefficients and other gas-light interactions. They can be open for gas exchange during operation or sealed for reference purposes. Gas cells are made of transparent materials like borosilicate or fused quartz and are available with various gases for different spectroscopic applications.

Sealed Gas and Vapor Cells

Sealed gas cells are used for reference purposes and are filled with a specific gas during production and then sealed. These cells have optical windows for light entry and exit and are leak-tested for reliability. Reference gas cells are available with different gases, including atomic and molecular gases like iodine, hydrogen, helium, and others. Vapor cells, containing gases with high vapor pressure, are also commonly used in spectroscopic applications.

Sensitivity and Gas Pressure

The sensitivity of laser spectroscopy depends on factors like absorption cross-sections, path length of light in the gas, and optical power. Gas pressure in the cell can affect sensitivity, with high pressure often desired for increased sensitivity. Gas purity is essential to avoid contamination, and gas cells may need heating for certain applications to achieve vapor pressure or prevent condensation.

Realizing a Long Path Length

To achieve a long path length for light in gas cells, multipass cells or hollow-core fibers can be used. Multipass cells allow multiple reflections of light through the gas, increasing the path length. Hollow-core fibers filled with gas provide a compact setup with efficient light-gas interaction. These approaches are crucial for enhancing sensitivity and performance in laser spectroscopy.

Vacuum Cells in Photonics

Vacuum cells are used for optical trapping, high harmonic generation, and experiments requiring a controlled environment. These cells are designed to be empty or contain a minimal number of atoms or ions for specific applications. Vacuum cells are essential for high-precision optical metrology, wakefield acceleration, and experiments with intense laser beams.

Conclusion

Gas and vacuum cells play a vital role in photonics applications, especially in laser spectroscopy and optical trapping. Understanding the design, sensitivity factors, and applications of these cells is crucial for conducting accurate spectroscopic measurements and experiments in controlled environments.

Source: OCI Vacuum Microengineering
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