Source: National Institute of Standards and Technology

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The Concept of Optical Frequency in Optics

The optical frequency refers to the oscillation frequency of an electromagnetic wave, such as a laser beam. In the case of visible light, optical frequencies typically range between 400 THz and 700 THz, corresponding to vacuum wavelengths between 700 nm and 400 nm. Infrared light has lower optical frequencies, while ultraviolet light has higher frequencies.

Angular Optical Frequencies

Many equations in optics involve angular optical frequencies, which are times the optical frequency. Light usually does not have a single optical frequency; its power is distributed over a range of frequencies. The optical spectrum describes how the power is distributed over these frequencies.

Optical Frequency Standards

Highly frequency-stabilized lasers can produce light with very narrow optical bandwidths, even below 1 Hz, and high frequency stability. These sources, known as optical frequency standards, are crucial for applications like optical clocks.

Calculating Optical Frequency

The optical frequency can be calculated by dividing the vacuum velocity of light by the vacuum wavelength. For measuring the frequency difference between two similar wavelengths, an approximate equation involving the mean wavelength can be used.

Optical Frequency Metrology

Optical frequencies can be measured more precisely than wavelengths using methods like stabilized frequency combs. These measurements allow for accurate comparisons between optical and microwave frequencies.

Significance of Optical Frequency

The optical frequency of light is fundamental, especially in interactions with matter. Atoms and ions respond to the optical frequency rather than the wavelength. Resonant excitation processes occur when the optical frequency matches certain internal resonant frequencies.

Conclusion

Understanding optical frequency is essential in various optical applications, from laser technology to optical clocks. The precise control and measurement of optical frequencies play a critical role in modern optics and photonics.

Source: Sites at USC – University of Southern California
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