Laser development has made it possible to easily obtain an ultrashort light pulse on the order of a picosecond and femtosecond. A light pulse of 1 ps has a length of only 0.3 mm and propagates at a speed of 300,000 km/s. Of course, it cannot be directly seen. Moreover, unlike a light from a continuous-wave (cw) laser, interference between two such short pulses occurs only when they arrive at a point simultaneously. Recording such interference as a hologram makes it possible to observe the propagation of the light, which is analogous to the propagation of a ring of waves on water.
This chapter demonstrates the propagation of a light pulse undergoing refraction and total reflection inside a medium, as well as diffraction by a grating. These phenomena themselves are well known in optics and the formulae have been established. Picosecond- and femtosecond-pulsed lasers are used to record the hologram in this chapter’s example.
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