about 4 months ago - 1 comment
Posted by: amit_physics on January 18, 2012. One must have seen and if not seen then must have heard the term laser. But if you have seen the laser light emitting from a source, then there should be natural question how does a laser work? Therefore let us discuss how the laser works? As already
about 1 year ago - 3 comments
Posted by: amit_physics on January 13, 2011. As we have discussed in the previously, that principle of laser is stimulated emission and for it to take place, population inversion has to be achieved and maintained. For this, there must be a source of external energy, which can continuously supply energy to energy to laser medium,
about 1 year ago - 2 comments
Posted by: amit_physics on January 10, 2011. When energy is given to laser medium (solid, liquid or gas), then only a small fraction of laser medium shows lasing action. This part of laser medium is called active medium or active centre. Thus, due to this reason, the laser medium is also called the heart of
about 1 year ago - No comments
Posted by: amit_physics on January 9, 2011. The lasers can be classified on the basis of state as explained below: a) State of laser medium: According to the state of laser medium, we have solid state lasers like ruby laser,gas lasers like He-Ne laser and carbon dioxide laser, semiconductor laser and liquid laser like dye
about 1 year ago - 1 comment
Posted by: amit_physics on January 9, 2011. It is also the excited state but having life time of 10-5 to 10-3 seconds. Population inversion occurs only in between the metastable state and lower state. The two states in between the population inversion occurs and laser is achieved, the upper one is known as upper laser
about 1 year ago - 3 comments
Posted by: amit_physics on January 9, 2011. Normally the population density of atoms/electrons is more in the ground state than the excited state. But if the process of stimulated emission dominates over the process of spontaneous emission, then it may be possible that N2 > N1. Where N1 is the number of atoms in the
about 1 year ago - 3 comments
Posted by: amit_physics on January 8, 2011. If the atom is in the excited state E2 and a photon of energy exactly equal to E2 – E1 = hυ is incident on it, then the incident photon interacts with the atom in the excited state and then it stimulates or induces the atom to come
about 1 year ago - 3 comments
Posted by: amit_physics on January 8, 2011. If the atom in the excited state automatically decays to the ground state by emitting a photon of energy (E2 – E1 = hυ), then this process is called spontaneous emission. Generally an atom/electron in excited state can stay for 10-9 – 10-8 seconds. Characteristics of spontaneous emission:
about 1 year ago - No comments
Posted by: amit_physics on January 6, 2011. A laser beam has the following important characteristics: 1. Directionality: An ordinary source of light emits light waves in all the directions and is highly divergent. But the divergence or angular spread of a laser is very small. 2. Monochromaticity: It means that all the laser rays have
about 1 year ago - No comments