Which property of a LASER indicates that it emits energy at one specific frequency?

The property of a LASER that indicates it emits energy at one specific frequency is monochromaticity. Monochromatic means that the light emitted by the LASER is of a single wavelength, which corresponds to a specific frequency of light. This characteristic is crucial for many applications of LASERS, such as in communication, medical procedures, and precise measurements, where the purity of a single frequency allows for more effective and reliable results.

In contrast, coherence refers to the ability of the light waves to maintain a fixed and predictable phase relationship over time, while highly directional describes how focused and straight the beam of light is, ensuring minimal spread over distance. High intensity relates to the power of the LASER beam but does not imply anything about the frequency or wavelength. Thus, monochromaticity is the defining feature regarding the emission of energy at a specific frequency.