Map tutorial(laser)

Lasers consist of:
- An active medium (e.g., ruby).
- Two mirrors on either end to reflect light.
- An optical pump (usually a lamp) supplying energy.

Optical Pumping:
- Energy from the optical pump is used to excite electrons in the active medium from the ground state to an excited state.
- Electrons eventually fall back to ground state naturally, leading to spontaneous emission of photons.
Key Concepts:
- Excited State: A higher energy level reached by electrons due to energy absorption.
- Metastable State: An intermediate energy state where electrons can remain longer, helping achieve population inversion.

Spontaneous Emission:
- Electrons drop to ground state spontaneously without external influence, emitting photons irregularly.
Stimulated Emission:
- A photon with exact energy interacts with an excited atom, causing the emission of a second photon in phase and direction. This principle leads to light amplification.

Emission of stimulated photons leads to optical amplification:
- Each emitted photon can further stimulate other excited electrons, creating a chain reaction of light emission.
Diagram Representation:
- Full mirror on one side, partially silvered mirror on the other: allows most light reflection and a small portion to exit as coherent laser light.

Coherence: All laser light waves are in phase and travel in the same direction.
Monochromatic: Emission of light of a single wavelength (one color).

Penetration Depth:
- The optical penetration depth of laser light in biological tissues varies with wavelength.
- Shorter wavelengths (near UV) are absorbed more superficially, while longer wavelengths (near infrared) penetrate deeper.
Key Interactions with Biological Tissues:
- Photothermal Interaction: Utilized in treating conditions like port-wine stains, where heat from laser light destroys abnormal blood vessels by heating them up to the point of necrosis.
- Photoablation: Involves thermally removing tissue; common in laser surgical procedures.
- Photochemical Interaction: Used in targeted treatments, such as dynamic therapy, where light activates a drug to produce singlet oxygen that is toxic to cancer cells.

Total Internal Reflection (TIR):
- Phenomenon where light reflects entirely within a medium due to an angle of incidence greater than the critical angle, essential for fiber optics and laser technology.
Refractive Index:
- The relationship between different media (e.g., glass core and plastic cladding in fiber optics) facilitates TIR.
Examples of Wavelength Interaction:
- For hemoglobin: absorption peaks differ for saturated (near infrared) and unsaturated (red light).

Lasers combine advanced physical principles with medical applications, ensuring precise targeting of tissues while minimizing damage to surrounding areas. Essential for modern therapies ranging from cosmetic to surgical interventions.