Lasers
- What is population inversion and why is it necessary for laser action? In one line Population inversion is the state in which more atoms are in a higher energy level than in a lower one, and it is needed so that... 1
- What is pumping in a laser and what are the different methods of pumping? In one line Pumping is the process of supplying energy to the active medium to lift atoms to higher energy levels and create population inve... 1
- What do active medium and active centre mean in a laser? In one line The active medium is the material in which population inversion and light amplification take place, and the active centres are t... 1
- What is the difference between spontaneous emission and stimulated emission of radiation? In one line In spontaneous emission an excited atom drops to a lower level on its own and emits a photon in a random direction and phase, wh... 1
- What is the resonant (optical) cavity in a laser and what job does it do? In one line The resonant cavity is a pair of mirrors around the active medium that sends light back and forth through it many times, buildin... 1
- What are coherence length and coherence time, and how are they related? In one line Coherence time is the time for which a light wave keeps a fixed, predictable phase, and coherence length is the distance the wav... 1
- What are the main characteristics of laser light that make it different from ordinary light? In one line Laser light is highly monochromatic, coherent, directional and intense, unlike light from a bulb, which is mixed in wavelength,... 1
- How is a He-Ne laser constructed and how does it work? In one line A He-Ne laser is a gas laser in which an electric discharge excites helium atoms, which pass their energy to neon atoms by colli... 1
- How is a fibre laser constructed and how does it produce laser light? In one line A fibre laser uses an optical fibre whose core is doped with rare-earth ions as the active medium, pumped by diode lasers, with... 1
- How does LiDAR use a laser to measure distance and map surroundings? In one line LiDAR (Light Detection and Ranging) fires short laser pulses at objects and measures how long the reflected light takes to retur... 1
- How does a laser barcode reader read the product code at a shop counter? In one line A barcode reader sweeps a laser beam across the black and white bars, and a photodetector turns the pattern of reflected light i... 1
- How are lasers used in metal work such as cutting, welding and drilling? In one line A focused laser beam delivers a very high power density to a tiny spot, which heats metal fast enough to melt or vaporise it, so... 1
- With a neat energy level diagram, describe the construction and working of He-Ne Laser. He–Ne laser is a four-level gas laser that gives a continuous output at 6328 Å (red). Construction: discharge tube (He:Ne ≈ 10:1, ~1 mm Hg)... 1
- What is resonant cavity? Explain its use in the generation of Laser beams. Resonant cavity (optical resonator): A pair of mirrors placed facing each other, parallel (or confocal), at the two ends of the active mediu... 1
- Explain optical resonator in LASER? Optical resonator is the arrangement of two mirrors placed at the ends of the laser's active medium, facing each other and aligned with its... 1
- List and briefly explain any two industrial applications of laser. Lasers produce a highly directional, monochromatic, coherent and very intense beam that can be focused to a tiny spot (about µm) with power... 1
- With the help of neat diagram, explain construction and working of He Ne laser. He–Ne laser is a four-level gas laser that gives a continuous output at 6328 Å (red). Construction: discharge tube (He:Ne ≈ 10:1, ~1 mm Hg)... 1
- What is metastable state? What is the role of metastable state in LASER? Metastable state: An excited energy level of an atom in which the electron stays for an unusually long time, about 10⁻³ s, compared with an... 1
- With the neat energy level diagram, explain the construction and working of He Ne Gas laser. He–Ne laser is a four-level gas laser that gives a continuous output at 6328 Å (red). Construction: discharge tube (He:Ne ≈ 10:1, ~1 mm Hg)... 1
- What is Lidar technology and how does it work? LiDAR (Light Detection And Ranging) is a remote-sensing technique. It uses pulsed laser light to measure distances and build accurate 3-D ma... 1