Discuss the applications of LASER in: Bar-code scanners, LASER cooling
Applications of LASER
i) LASER in Bar-code Scanners
Bar-code scanners use LASER diodes (typically red LASERs like He-Ne) for reading printed barcodes.
Working Principle:
- The LASER beam is directed onto the barcode.
- The black and white lines reflect the LASER light differently:
- White spaces reflect more light.
- Black bars absorb more light.
- A photodetector detects this variation in reflection and converts it into an electrical signal.
- The signal is decoded to identify product information.
Advantages:
- High speed and precision.
- Can scan from longer distances.
- Useful in supermarkets, libraries, warehouses, and inventory systems.
ii) LASER Cooling
LASER cooling is a technique used to reduce the motion (kinetic energy) of atoms, thereby lowering their temperature to near absolute zero.
Working Principle:
- Atoms absorb photons from a Doppler-tuned LASER beam.
- Due to momentum transfer, atoms moving toward the beam are slowed down.
- When photons are re-emitted, their momentum is random, resulting in a net cooling effect.
- This is often done in six directions using opposing LASER beams, forming what is called an optical molasses.
Applications:
- Fundamental physics research (e.g., Bose–Einstein condensates).
- Atomic clocks.
- Quantum computing and precision measurements.