CU photonics

 The main three optical sources that we deal with n day to day life are incandescent light, LED, and laser. Noise should be very less. 1610 nm is the usual wavelength of a light source to be used. LED has a larger spectrum range. Basic concept - E= E2-E1 = hf Absorption-> When the electron gains energy hf and moves to a higher state or energy level. Spontaneous emission is when the electron moves from a higher state to a lower state. Stimulated emission is when the transition of electron takes place from a higher energy level to a lower energy level on the supply of external energy hf, at the cost of two coherent energies released by the electron. The Einstein relation --- Two energy level E2 E1 Population density-   number of atoms per unit volume Conditions for LASER- 1. metastable state - 2. population inversion-  3. stimulated emulation-  Stimulated emission- it is controlled from outside energy transition takes place between definite selected energy leve...