Example of A Model of Gain Medium
A universal model valid for all laser types does not exist. The simplest model includes two systems of sub-levels: upper and lower. Within each level, the fast transitions lead to the Boltzmann distribution of excitations among sub-levels (fig.1). The upper level is assumed to be metastable. Also, gain and refractive index are assumed independent of a particular way of excitation.
For good performance of the gain medium, the separation between sub-levels should be larger than working temperature; then, at pump frequency, the absorption dominates.
In the case of amplification of optical signals, the lasing frequency is called signal frequency. However, the same term is used even in the laser oscillators, when amplified radiation is used to transfer energy rather than information. The model below seems to work well for most optically-pumped solid-state lasers.
Read more about this topic: Active Laser Medium
Famous quotes containing the words model, gain and/or medium:
“The best way to teach a child restraint and generosity is to be a model of those qualities yourself. If your child sees that you want a particular item but refrain from buying it, either because it isn’t practical or because you can’t afford it, he will begin to understand restraint. Likewise, if you donate books or clothing to charity, take him with you to distribute the items to teach him about generosity.”
—Lawrence Balter (20th century)
“The honest Man has, I know, that modest Desire of Gain which is peculiar to those who understand better Things than Riches; and I dare say he would be contented with much less than what is called Wealth in that Quarter of the Town which he inhabits, and will oblige all his Customers with Demands agreeable to the Moderation of his Desires.”
—Richard Steele (1672–1729)
“In the one instance, the dreamer ... loses sight of this object in a wilderness of deductions and suggestions ... until ... he finds the incitamentum, or first cause of his musings,... forgotten. In my case, the primary object was invariably frivolous, although assuming, through the medium of my distempered vision, a refracted and unreal importance.”
—Edgar Allan Poe (1809–1849)