Four level laser. Thus the number of atoms in E3 exceeds the number of atoms in E2. The population inversion is achieved between E3 and E2. The laser action takes place between E3 and E2 by stimulated emission. The atoms from energy state E2 get deexcited to E1. The atoms from E1 are again pumped to E4. Example: HeliumNeon laser is four level laser system.Optical amplification in the gain medium of a laser or laser amplifier arises from stimulated emission, where the input light induces transitions of laseractive ions from some excited state to a lower state. In a threelevel system, the laser transition ends on the ground state. advantages of 4 level laser system
Since it is way easier for a 4level laser to get population inversion than 3level laser, 3level laser is still in use nowadays. So what's the advantage of 3level laser over 4level laser?
Sep 14, 2017 Answer Wiki. In 4 level laser, with the help of pumping the atoms from ground state n1 are raised to excited state n4. From the n4, the atoms decay to n3 by spontaneous emission. The transition rate of atoms from n4 to n3 is much faster because of life time of the atoms is very small of the order of 108 seconds as compared to transition rate Figure 2. 7: Energy level diagram in a four level laser. The pumping operation of a four level laser is similar to the pumping of a three level laser. This is done by a rapid population of the upper laser level (E 3), through the higher energy level (E 4). The advantage of the four level laseris the low population of the lower laser energy level (E 2). advantages of 4 level laser systemRating: 4.49 / Views: 897