About creating standing wave with laser

In summary, the conversation discusses the concept of standing waves, specifically in relation to lasers. It is possible to produce a standing wave using superpositions of laser beams, known as optical lattices. The frequency of a laser is typically very high, around 10^14 Hz, which may make it difficult to observe the standing wave. However, there are ways to lower the frequency to make it visible.
  • #1
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Hi all,
I remember the standing wave is introduced in a chapter of mechanical wave in my undergraduate physics times ago. It is said that two waves of the same frequency propagating the opposite directions will form a standing wave in space. I wonder if it is possible to produce the standing wave with laser (light) also. I read something about laser, takes 780nm single-mode laser as example, I wonder if the light is always in the form of sinusoidal wave or not. If should does it mean we only have to split the laser beam from the same source into two and use two mirrors to change the path of the light such that they moves in opposite direction to get the standing wave? If this's the idea, I have something confusing me. In my book, a mechanical wave has both wave vector and frequency. Assuming two waves forming the standing wave has the same frequency (f) but opposite wave vector, we will see a standing wave with amplitude is oscillating in the frequency f. In laser, what's that frequency and where does it come from?

This is confusing because I am reading a book introducing laser and it seems that the laser beam is pretty much just spatial sinusoidal wave. I didn't see the frequency discussed. If there is frequency for a laser beam, what's the typical value of it. It is any way to make that frequency low enough so we can see the optical standing wave with amplitude oscillating in visible way.

Thanks.
 
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  • #2
You can produce standing wave using superpositions of laser beams, which are called optical lattices. The result is a periodic oscillating potential for an atom, either because of a spatially varying amplitude or polarization. If you want to learn more, and have institutional access, I really recommend this review article: http://dx.doi.org/10.1016/S0370-1573(01)00017-5

As for the frequency of a laser, it is simply ##\nu = c/\lambda##.
 
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  • #3
Thanks DrClaude. Let say the laser beam is of the form

$$y(x) = A\cos(kx + \omega t)$$

So by adding two counter-propagating waves, we have
$$
A\cos(kx + \omega t) + A\cos(-kx + \omega t) = 2\cos(\omega t)\cos(kx)
$$

If the laser frequency is ##\omega=2\pi c/ \lambda##, it will have the order of ##10^{14}##Hz, it so big. So if it is oscillating that fast, the ##\cos(\omega t)## will be averaged to zero so does it mean there is not observable standing wave?
 

1. How does a laser create a standing wave?

A laser can create a standing wave by emitting a beam of coherent light that is bounced back and forth between two mirrors, creating interference patterns that result in a stationary wave pattern.

2. What factors affect the creation of a standing wave with a laser?

The factors that affect the creation of a standing wave with a laser include the wavelength of the laser, the distance between the mirrors, and the angle at which the laser beam is reflected.

3. Can any type of laser create a standing wave?

No, not all lasers are capable of creating standing waves. The laser must have a stable and coherent beam to produce the necessary interference patterns for a standing wave to form.

4. How is a standing wave with a laser different from a regular laser beam?

A standing wave with a laser is different from a regular laser beam because it is a stationary pattern of light rather than a moving beam. The energy is concentrated in specific areas, creating nodes and antinodes, rather than being spread out over a larger area.

5. What are the practical applications of creating a standing wave with a laser?

Creating standing waves with lasers has numerous practical applications, including in optical communication, spectroscopy, and measuring small changes in distance. It is also used in research and development for studying wave behavior and interference.

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