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6: A ray of 610 nm light goes from air into fused quartz at an incident angle of 55.0o. At what incident angle must 470 nm light enter flint glass to have the same angle of refraction?

Speckle optimization refers to the combined effects of speckle shaping and speckle following. The former technique requires an active transmitter, while the latter requires and active receiver. Both require closed-loop feedback, and both use dithering and metric peak-up.

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Any type of wave can exhibit dispersion. Sound waves, all types of electromagnetic waves, and water waves can be dispersed according to wavelength. Dispersion occurs whenever the speed of propagation depends on wavelength, thus separating and spreading out various wavelengths. Dispersion may require special circumstances and can result in spectacular displays such as in the production of a rainbow. This is also true for sound, since all frequencies ordinarily travel at the same speed. If you listen to sound through a long tube, such as a vacuum cleaner hose, you can easily hear it is dispersed by interaction with the tube. Dispersion, in fact, can reveal a great deal about what the wave has encountered that disperses its wavelengths. The dispersion of electromagnetic radiation from outer space, for example, has revealed much about what exists between the stars—the so-called empty space.

To further investigate fade mitigation, we have developed an extensive suite of beam propagation simulation tools. The core simulation capability is a library of fully validated wave-optic propagation code. It can be used to model laser propagation through atmosphere (horizontal path, slant path, airborne and satellite platforms) and imaging through turbulent atmosphere. Active optical components (steering mirrors, DMs) and control system elements are included.

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There is considerable interest in extending the range of laser communications. This can be done quite feasibly in space or the upper atmosphere. Near the ground, however, atmospheric aberrations are relatively strong and distributed along the entire path. The result is severe beam spreading and wander, which reduces the signal that is captured by the receiver terminal.

Douglas College Physics 1207 Copyright © August 22, 2016 by OpenStax is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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We have simulated a speckle optimization scenario with typical parameters for a laser communication system over a long horizontal path length. The results of these simulations show that even with a modest number of phase modulators it is possible to very significantly reduce the occurrence of deep fades. Our analysis of system performance indicates that speckle following and shaping can maintain the received power stabilized within a 10 db band under conditions that produce fades deeper than 30 db for an uncompensated system.

Y Wang · 2017 · 43 — Fig. 3. Paraxial refractive axicon with radius a, base angle α, and refractive index n. A plane wave with a Gaussian amplitude distribution is normally incident ...

The characteristics of the speckle pattern at the detector plane are determined by the atmospheric aberrations and the optical system. If the typical size of an individual speckle is larger than the sensor then it is possible to dither the sensor (using motion control hardware) to determine the local gradient of the speckle. Then it is a matter of climbing the gradient and constantly positioning the sensor at the peak intensity of a speckle, termed Speckle Following.

Everyone enjoys the spectacle of a rainbow glimmering against a dark stormy sky. How does sunlight falling on clear drops of rain get broken into the rainbow of colors we see? The same process causes white light to be broken into colors by a clear glass prism or a diamond. (See Figure 1.)

1: (a) What is the ratio of the speed of red light to violet light in diamond, based on Table 2? (b) What is this ratio in polystyrene? (c) Which is more dispersive?

Dispersion may produce beautiful rainbows, but it can cause problems in optical systems. White light used to transmit messages in a fiber is dispersed, spreading out in time and eventually overlapping with other messages. Since a laser produces a nearly pure wavelength, its light experiences little dispersion, an advantage over white light for transmission of information. In contrast, dispersion of electromagnetic waves coming to us from outer space can be used to determine the amount of matter they pass through. As with many phenomena, dispersion can be useful or a nuisance, depending on the situation and our human goals.

Refraction is responsible for dispersion in rainbows and many other situations. The angle of refraction depends on the index of refraction, as we saw in Chapter 25.3 The Law of Refraction. We know that the index of refraction n depends on the medium. But for a given medium, n also depends on wavelength. (See Table 2. Note that, for a given medium, n increases as wavelength decreases and is greatest for violet light. Thus violet light is bent more than red light, as shown for a prism in Figure 3(b), and the light is dispersed into the same sequence of wavelengths as seen in Figure 1 and Figure 2.

A severely perturbed beam will exhibit intensity scintillation, essentially a speckle pattern. If a very dark portion of the speckle pattern covers either the aperture or the active region of the detector, the total power captured by the sensor is reduced. This phenomenon is called a fade and exacerbates bit error rate reducing information bandwidth. During such events the power reaching the detector may be reduced by a factor of more than a thousand relative to the average power. It is very difficult to design a communications link that can maintain a low bit error rate (BER) during these deep fade events. Fading of the signal due to the effects of atmospheric turbulence is a well documented problem for optical communication links.

2: A beam of white light goes from air into water at an incident angle of 75.0 degrees. At what angles are the red (660 nm) and violet (410 nm) parts of the light refracted?

Speckle evolution is more complex than simple translations; they grow and fade. Shaping can be employed to ensure that there is a large enough speckle near the sensor. This technique involves modulating the phase at the transmitter, similar to the action of a deformable mirror. Dithering the phase will cause the speckle pattern to evolve and a hill-climbing algorithm can be devised to maintain the power on the sensor.

Free-space optical (FSO) communication systems occupy a niche market as a solution to the last mile problem. Digging trenches to lay fiber is expensive especially in urban areas. A pair of high bandwidth FSO terminals can be deployed faster and cheaper than fiber of equivalent bandwidth. Compared to other wireless technology, FSO is more secure due to the difficulty of clandestine interception of a narrow laser beam of an AO system.

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by T Erdogan · Cited by 3 — Gratings are based on diffraction and interference: Diffraction gratings can be understood using the optical principles of diffraction and interference.

Free-space optical (FSO) communication systems occupy a niche market as a solution to the last mile problem. Digging trenches to lay fiber is expensive especially in urban areas.

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Varifocal (variable focus) lenses will give all ranges of focal length in one lens, with no visible lines or markings to be seen. Simply package ...

We see about six colors in a rainbow—red, orange, yellow, green, blue, and violet; sometimes indigo is listed, too. Those colors are associated with different wavelengths of light, as shown in Figure 2. When our eye receives pure-wavelength light, we tend to see only one of the six colors, depending on wavelength. The thousands of other hues we can sense in other situations are our eye’s response to various mixtures of wavelengths. White light, in particular, is a fairly uniform mixture of all visible wavelengths. Sunlight, considered to be white, actually appears to be a bit yellow because of its mixture of wavelengths, but it does contain all visible wavelengths. The sequence of colors in rainbows is the same sequence as the colors plotted versus wavelength in Figure 2. What this implies is that white light is spread out according to wavelength in a rainbow. Dispersion is defined as the spreading of white light into its full spectrum of wavelengths. More technically, dispersion occurs whenever there is a process that changes the direction of light in a manner that depends on wavelength. Dispersion, as a general phenomenon, can occur for any type of wave and always involves wavelength-dependent processes.

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Absorption (electromagnetic radiation) ... In physics, absorption of electromagnetic radiation is how matter (typically electrons bound in atoms) takes up a ...

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Rainbows are produced by a combination of refraction and reflection. You may have noticed that you see a rainbow only when you look away from the sun. Light enters a drop of water and is reflected from the back of the drop, as shown in Figure 4. The light is refracted both as it enters and as it leaves the drop. Since the index of refraction of water varies with wavelength, the light is dispersed, and a rainbow is observed, as shown in Figure 5 (a). (There is no dispersion caused by reflection at the back surface, since the law of reflection does not depend on wavelength.) The actual rainbow of colors seen by an observer depends on the myriad of rays being refracted and reflected toward the observer’s eyes from numerous drops of water. The effect is most spectacular when the background is dark, as in stormy weather, but can also be observed in waterfalls and lawn sprinklers. The arc of a rainbow comes from the need to be looking at a specific angle relative to the direction of the sun, as illustrated in Figure 5 (b). (If there are two reflections of light within the water drop, another “secondary” rainbow is produced. This rare event produces an arc that lies above the primary rainbow arc—see Figure 5 (c).)

Our simulations show that there is a limit to benefits of traditional adaptive optics for the deep fade regime, where speckle and beam spreading effects prevent high fidelity measurement of the wavefront. In this scenario, non-traditional AO techniques for fade mitigation are employed, such as speckle optimization.

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4: (a) A narrow beam of light containing yellow (580 nm) and green (550 nm) wavelengths goes from polystyrene to air, striking the surface at a 30.0o incident angle. What is the angle between the colours when they emerge? (b) How far would they have to travel to be separated by 1.00 mm?

This 3ft Micro USB Cable meets the USB 2.0 Hi-Speed specification, it is also backward compatible with 1.0 and 1.1. The type A male end plugs into your ...

How does a lens form an image? See how light rays are refracted by a lens. Watch how the image changes when you adjust the focal length of the lens, move the object, move the lens, or move the screen.

5: A parallel beam of light containing orange (610 nm) and violet (410 nm) wavelengths goes from fused quartz to water, striking the surface between them at a 60.0o incident angle. What is the angle between the two colours in water?

AOA Xinetics has investigated the benefits of traditional adaptive optics for laser communications. We have built custom wavefront sensors to gather data from field measurements of turbulence over horizontal line of sight paths. The results have shown feasibility of achieving a degree of correction using successive modal corrections from the atmospheric turbulence.

7: A narrow beam of light containing red (660 nm) and blue (470 nm) wavelengths travels from air through a 1.00 cm thick flat piece of crown glass and back to air again. The beam strikes at a 30.0o incident angle. (a) At what angles do the two colours emerge? (b) By what distance are the red and blue separated when they emerge?

8: A narrow beam of white light enters a prism made of crown glass at a 45.0o incident angle, as shown below in Figure 7. At what angles, θRed and θViolet do the red (660 nm) and violet (410 nm) components of the light emerge from the prism?

How far is 3⁄8 of an inch in millimeters? 0.375 in to mm conversion. Amount. From.