Sound amplification by stimulated emission of radiation mechanism and an active medium. The pumping procedure can be induced for example by an alternating electric field or with some mechanical vibrations of resonators, followed by acoustic amplification in the active medium. The fact that a SASER operates on principles remarkably similar to a laser, can lead to an easier way of understanding the relevant operation circumstances. Instead of a feedback-built potent wave of electromagnetic radiation, a SASER delivers a potent sound wave. Some methods for sound amplification of GHz-THz have been proposed so far. Some have been explored only theoretically and others have been explored in non-coherent experiments.
Optic axis of a crystal displays. Optic axis of a crystal An optic axis of a crystal is a direction in which a ray of transmitted light suffers no birefringence (double refraction). An optical axis is a direction rather than a single line: all rays that are parallel to that direction exhibit the same lack of birefringence. Crystals may have a single optic axis, in which case they are "uniaxial", or two different optic axes, in which case they are "biaxial". Non-crystalline materials generally have no birefringence and thus, no optic axis. A uniaxial crystal (e.g. calcite, quartz) is isotropic within the plane orthogonal to