Laser beams and beat frequency.

In summary, combining two laser beams of different wavelengths can result in a beat frequency of the difference between the two lasers. This can also lead to the generation of harmonic waves and cause issues in telecommunication networks due to optical nonlinearity. Special optical fibers have been developed to reduce this effect, but older fibers may still be affected.
  • #1
Bill E
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If I combine 2 laser beams of different wavelengths, would I get a beat frequency of the difference between the 2 lasers?

Thanks, Bill
 
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  • #2
It is possible to measure both the sum and difference frequencies (heterodyne detection). IIRC, implementation requires the detector to be 'locked' to one of the oscillators- at least, the heterodyne optical systems I used have all set one of the oscillators as the 'reference'.
 
  • #3
You can get even more: mixing two laser beams of close frequencies: f, f+Df (Df<<f) in a real medium (a little bit nonlinear) you may get harmonic waves: f+2Df, f-Df, etc.

This effect causes lots of problems to WDM telecommuniaction networks, as optical nonlinearity in the glass used for fibres is sufficient to generate cross-talks between lambda-channels: the data in channel f+2Df are noised by cross-talk generated by harmonic beat of signals transmitted in f and f+Df.
Special kind of optical fibres had to be developed to reduce this effect, they are installed nowadays, but it is impossible to use even half of channels of WDM over 30 years old long-distance fibres, which were not aware about such effects.
 
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1. What are laser beams and how do they work?

Laser beams are highly concentrated beams of light that are created by stimulating atoms or molecules to emit photons in a specific direction. This process is known as stimulated emission and it creates a coherent and monochromatic light beam. The light produced by laser beams is also highly directional and can travel long distances without dispersing.

2. How is the frequency of a laser beam measured?

The frequency of a laser beam is measured in Hertz (Hz) and it represents the number of cycles per second that the light beam completes. It is determined by the energy level of the atoms or molecules that are stimulated to emit the light, and can be controlled by adjusting the energy source or the material used to create the laser beam.

3. What is beat frequency and how is it related to laser beams?

Beat frequency is the difference in frequency between two waves that are superimposed on each other. In the context of laser beams, it refers to the difference in frequency between two laser beams that are produced by two different sources. This effect is commonly used in laser interferometry to measure and detect small changes in distance or motion.

4. Can laser beams be harmful to humans?

Yes, laser beams can be harmful to humans if proper precautions are not taken. High-powered laser beams can cause eye damage, skin burns, and even start fires. Therefore, it is important to handle and operate lasers safely, and use protective equipment such as goggles and shields when necessary.

5. What are some practical applications of laser beams and beat frequency?

Laser beams have a wide range of practical applications, including in medicine (surgery, eye treatments), communication (optical fibers, barcode scanners), manufacturing (cutting, welding, drilling), and research (spectroscopy, microscopy). Beat frequency is also used in various industries for precision measurements, such as in metrology, geodesy, and navigation systems.

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