The following is not a candidate material for Laser source in Fiber Optics
Phosphorous
In the field of Fiber Optics, laser sources are crucial components responsible for generating the light signals that carry information through optical fibers. These sources must meet specific requirements, such as producing light at a particular wavelength, having a narrow spectral width, and maintaining high power and stability. Different materials are used as active media in lasers to produce light through stimulated emission.
Several materials are commonly used as active media in various types of lasers, many of which find applications in fiber optic communication systems:
Phosphorous is a chemical element (P) known for its phosphorescence (light emission after absorbing radiation) and fluorescence properties, especially in compounds. However, elemental phosphorous or its simple compounds are not typically used as the primary active medium for generating coherent laser light. Lasers require materials that can sustain a population inversion and efficiently undergo stimulated emission. While phosphorous can be an important dopant in certain optical materials or semiconductors (like in LEDs), it is not a standalone candidate material for the active gain medium in a laser source for fiber optics or any other primary laser application. The active media for lasers are usually specific types of crystals, glasses, gases, or semiconductors.
Therefore, among the given options, Phosphorous is not considered a candidate material for a laser source in Fiber Optics.
What is a DISADVANTAGE of LED lights over LASER lights?
In a LASER device the instantaneous populations of energy $E_1$ and $E_2$ (figure below) to be $n_1$ and $n_2$ respectively. At thermal equilibrium the relative population is given by $n_2 = n_1e^{-h\nu_{12}/KT}$
The condition for population inversion when stimulated emission dominates is given by

The following are correct about a semiconductor LASER :
1. It requires population inversion
2. It has shorter lifetime than LED
3. It demonstrates spontaneous emission phenomenon
4. It generates monochromatic incoherent light.
Find out the correct answer :
In comparison to LED, LASER has
1. high emission frequency
2. no tuning arrangement
3. narrow spectral bandwidth
4. provision for confinement