Post on 22-Dec-2015
Lasers vs. Light
• A laser differs from other sources of light in that it emits light in a narrow straight line
• A laser consists of a gain medium, a mechanism to energize it, and something to provide optical feedback.
• The energy is typically supplied as an electrical current or as light at a different wavelength.
Lasers and their color in Nanometers
• Red 660-635 nm
• Green 532-520 nm
• Blue- 405 nm
• Violet 445-405 nm
Lights vs. Corneas
• Studies have found that even low-power laser beams of not more than 5 mW can cause permanent retinal damage if gazed at for several seconds; however, the eye's blink reflex makes this highly unlikely.
• Through their ability to produce temporary or permanent vision loss in varying degrees when aimed at the eyes.
Lights vs. Corneas (Part 2)
• Studies in the early twenty-first century found that the risk to the human eye from accidental exposure to light from commercially available class laser pointers having powers up to 5 mW seemed rather small
What lasers are used for
• Medicine: Bloodless surgery, laser healing, laser eye treatment
• Industries: Welding, making/cutting metals
• Law enforcement: Fingerprints and forensics
• Military: missile defense, radars, marking targets
Free Electron Laser
• This laser generate coherent, high power radiation that is widely tunable, currently ranging in wavelength from microwaves through terahertz
• They have the widest frequency range among all of the other lasers.
Chemical Laser
• Powered by a chemical reaction permitting a large of energy to be released at a fast rate.
• Continuous wave chemical lasers at very high power levels
• Hydrogen fluoride laser transmits 2700-2900 nm
• Deuterium fluoride laser transmits 3800 nm
Fiber Laser
• Solid-state lasers or laser amplifiers
• Guiding of light allows extremely long gain regions providing good cooling conditions; fibers have high surface area to volume ratio which allows efficient cooling.
• Fiber lasers have a fundamental limit in that the intensity of the light in the fiber cannot be so high that optical
Gas Laser
• Gas lasers using many different gases have been built and used for many purposes
• These relatively low cost but highly coherent lasers are extremely common in optical research and educational laboratories.
Solid State Lasers
• Use a crystalline or glass rod which is "doped" with ions that provide the required energy states.
• The usage of the term "solid-state" in laser physics is narrower than in typical use. Semiconductor lasers
Stimulated Emission
• Definition: A transition from the higher to lower energy state in which produces an additional photon.
• Thought up by Albert Einstein
• Transition to the higher state is absorption.
Reflection
• The proportion of light are indicated by the lengths of the solids.
• Law of reflection: The angle of incidence is equal to the angle of reflection
• Critical is 43 degrees for glass
• Prisms- 29.32 degrees(more effective w/ reflection)