Technology: A distorted route to the perfect beam
But because the fiber will distort some of the optical properties of the light, their use in more precise applications is limited.
Now, researchers in the United States have developed a system that uses holographic images to detect distortion of the fiber and then pre-
Treat the light to compensate for its distortion so that it appears from the fiber in its original state.
A widely used fiber called multi-mode fiber in communication, which has a relatively large diameter and can carry a large amount of data.
However, although the intensity change of light is more or less maintained in this fiber, other properties, such as phase and polarization, have also changed.
The phase of the light is related to its position along the cycle of the light.
Due to the wide diameter of the multi-mode fiber, light can enter at various angles and then bounce from one side to the other while moving along the fiber.
This means that different light travels different lengths along the fiber.
Therefore, if all the waves are synchronized, or are in phase (
As in the beam)
At the beginning of the fiber, they are out of sync or out of phase at the end.
The light also loses its uniform polarization, and the resulting beam spreads more than the original one.
In many applications, the transmission capability of optical fibers without these distortions is useful.
For example, in microsurgery, the beam must be focused on a very small point, which is impossible if the emerging beam deviates too much.
It is often necessary to maintain phase and polarization in holographic photography.
Less distortion can be achieved using a fiber called single fibermode fibre.
This fiber transmits light without distorting polarization and phase, and produces very small divergence.
Their cores are very narrow, usually only a few microns in diameter, so all the light travels along roughly the same path.
But they are limited in diameter, which means they cannot carry too much light.
Now a technology to obtain a single feature
Researchers from Northwestern University in Evanston, Illinois have developed pattern fibers from multi-mode fibers.
A laser beam with desired optical properties passes through A multi-mode fiber and appears from the far end with A completely different set of properties, now called B.
The new system first converts the beam A into A beam that has the exact opposite optical properties of B and is written as B *.
When the beam passes through the fiber, it should appear from the other end as the desired beam.
A is reflected into B * by reflection from the hologram *.
First, divide the beam A into two (see Diagram).
Part of it passes through the part that is usually the output of the fiber and appears from the input.
At this time, it has the optical properties of B.
The other half of the beam A is reflected from phase
A total mirror-a kind of absorbing light and then
The direction in which it is emitted is the same as the direction in which it enters, and the phase and polarization are opposite.
This beam is now *.
These two bundles, B and A *, combine on the surface of the light
They record sensitive plates for interference patterns-where peaks meet peaks, they reinforce each other and offset each other where peaks meet lows.
The interference pattern is a form of holographic photography.
When the holographic is subsequently illuminated separately using A beam A, the reflected beam has the properties of B.
The beam is fed through the fiber, and the beam eventually emitted from the far end will have the properties of.
It will have the same phase, polarization and divergence properties as the original beam.
There are two main limitations to this technology.
First, the holographic technology that the team is using is only 33 efficient in converting the lighting beam A to B.
The team is using better holographic material to overcome this problem.
Another drawback of the system is that if the fiber is bent, it will distort the light in a different way;
Thus, the correct negative distortion will no longer be produced by holographic photography.
However, the researchers believe that this technology is still useful for a large number of applications requiring beams with precise optical properties but with fixed beam paths.
Laser cutting is one of the applications.
It can be mounted further behind, and the beam is sent through holographic images and fixed fiber, rather than laser at the end of the industrial robot arm.