Is Frequency Doubling the Secret to Producing Red Light in Laser Pointers?

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Discussion Overview

The discussion revolves around the possibility of changing the frequency of light using a media filter, specifically in the context of producing red light in laser pointers. Participants explore theoretical and practical aspects of light frequency manipulation, including non-linear processes and the implications of conservation of energy.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that changing light frequency typically requires non-linear processes to generate higher harmonics or to modulate the frequency of light.
  • One participant emphasizes that while light can change its wavelength when passing through different media, the frequency remains constant, and the original wavelength is restored upon exiting the medium.
  • Another participant introduces the concept of fluorescence as an analogy, noting that while it involves a change in wavelength, it results in a loss of directional information.
  • Some participants assert that it is impossible to change the frequency of light without affecting its direction, while others inquire about the specific goals of the original question.
  • A later reply mentions that the lasing medium in typical laser pointers produces infrared light, which is then converted to red light using a frequency-doubling crystal.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of changing light frequency without altering its direction. While some agree on the limitations of passive filters, others explore the potential of non-linear processes, indicating that the discussion remains unresolved.

Contextual Notes

Participants reference concepts such as conservation of energy and the behavior of light in different media, but the discussion does not resolve the underlying assumptions or the specifics of the proposed methods.

EspangeBob
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Is it possible to change light wave frequency via a media filter?
or if it is impossible is there any why to do it?

without changing light direction !
 
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Welcome to the PF. :smile:

To change the light frequency, you would normally need some non-linear process to generate higher harmonics or to modulate the frequency of the light. Is that what you are asking about?

When light changes media as it propagates (like when it goes from air to glass), the frequency stays the same but the propagation velocity changes (so what happens to the wavelength?).

And what do you mean by "media filter"? :smile:
 
Remember conservation of energy. The energy of a photon is proportional to frequency.

So the power out of a passive filter is the power in, minus any absorption or reflection.
 
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EspangeBob said:
Is it possible to change light wave frequency via a media filter?
It is not possible to change the frequency of light without loss of direction.

Light can reduce it's wavelength slightly while propagating through slower materials such as glass, but the original wavelength is restored when the light exits the material.

The closest analogy to your “wanted” effect is fluorescence, where a molecule excited by a shorter wavelength photon then releases a lower energy photon with longer wavelength. But the direction information will be lost during the quantum conversion.
 
EspangeBob said:
Is it possible to change light wave frequency via a media filter?
or if it is impossible is there any why to do it?

without changing light direction !
Can you explain better what you are trying to accomplish?
 

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