Laser Handwritten Notes

StarLine Date Page: 4. Lasers -# Einstein's theory of matter radiation interaction :- This theory describes how atoms and radiations. interact with each other, and how energy and Momentur are exchanged between therr. 1. Absorption:- Suppose an atom is in the lower energy level Es. If a photon of energy hu = (E₂-Es) is incident on the atom, it imparts its energy to the atom and disappears. Then we say that that the atom absorbed the incident photon. As a result of absorption of energy, the atom jumps to the excited state. Ez. This transition is called an absorption transition. Ez Excited State 10-8 sec. E hu=E-E1 Incident photon E1 Ground State E Transition EE Probability P&N..((2)) Energy density P12 = B12. N.. P(v) 2. Spontaneous Emission :- When an ator at lower level is excited state to a energy higher energy level, it cannot stay in the excited. for a longer time. In a time of about 108s, State for the atom revers to the lower releasing a energy state by photon of energy hu. Emission of a phatan S Star Date: Page: by an atom without any Called spontaneous Enicich. external impetus is Ez hu Ex Before After Txansidion Ex E1 Probability Par = A21. Na 3. Stimulated Emission :- If an atom in the excited State interacts with. photon af energy hu= Ex-Es. The photan induces the excited state atom to make a downward transition, before the atom can make a spontaneet transition. The electric field of the light wave interact with the electrons of the excited atom and triggers stimulated emission. Es E E E Isansition EE Bobability Par CN.P() PBN P(v) Cate StarLink Pane # What is Laser Ans. The word LASER is an an intense Mana-acronym for Light, Amplification by stimulated Emission of Radiation:" It is a device to produce chromatic, collinated and highly coherent beam of light and depends an erission. The first Successful laser was Laser. the phenomenon of Stimulates Ruby #Derivation of Einstein A & B Coefficients:-at thermal equilibrium - Rate of absorption = Rate of Sp. En + Rate of St.2. Pi = P + P From eq... Baz N₂ P(V) = Az. Na + Bar N. P(V) Baa Na P(B) - Be, Na P(1) = Ai N A21 N2 Bie Ni-Bai Na P() P() = A (divided by Na) Bi N/N-B P(0) = A21/B01 (divided by Bar) Biz Ni-1 BN From Boltzman distribution when I particular N= e-E/KT A TN AT Ne ENT e-ELINT EEKT N e N 5 Cabal ongk Pay cladding Star Date: Fiber oals Abys Page: Fiber aur's Cata Page The numerical aperture CANA) of an optical fiber is a measure of its light gathering ability on the range of angles over which is can accept light. It is a key parameter that character. izes the performance of the fiber in Jems of its ability to capture and guide light efficiently. NA Sin Omexx #Acceptance Cone: the acceptance Cone is a 3-dimensional representation of the acceptance angle.. It describes the range of within which light can enter the fiber angles Come and still be efficiently guided along its length. The acceptance cone is defined by the numerical aperture (NA) of the optical fiber, a measure of its light-gethening ability. which is Cladding Fibex s Full acceffance A #Numerical aperture:- Acceptance Acceptance come Cladding #V-number: The v number, also known as the Normalized freg, parameter, or cut-off parameter, is a dissensiontess quantity used to Characterize multimode optical fibers. The Vnumber helps determine the maximum number mode of the Liber. to in More A Worx) refractive index nons higher v number indicate's a larger care diameter xeldiva supported the wavelength of light, resulting, Modes of propagation. Comulire Pay Pisey -17=2xYNA/^ 2 indicates a smaller core diameter relative to the wavelength, supporting fewer nodes. The number the establishes the correlation among radius (x), the refractive indices int and na of the core and cladding materials, and the wavelength of light propagating within the optical #Attenuation :- When light braved along the fiber.the loss of optical potser stichis alle 162 attenuation. Attenuation represents the evitar In sup