Engineering Physics

10.2 Characteristics of laser radiation

Laser radiation has the following important characteristics over ordinary light source. They are: i) monochromaticity, ii) directionality, iii) coherence and iv) brightness.

(i) Monochromaticity: A laser beam is more or less in single wavelength. i.e., the line width of laser beams are extremely narrow. The wavelengths spread of conventional light sources is usually 1 in 10⁶, whereas in case of laser light it will be 1 in 10¹⁵. i.e., if the frequency of radiation is 10¹⁵ Hz, then the width of line will be 1 Hz. So, laser radiation is said to be highly monochromatic. The degree of non-monochrotmaticity has been expressed as where dλ or dν is the variation in wavelength or variation in frequency of radiation. ...