In this lab we will experiment with instruments that compare different beams of light. These instruments are remarkably sensitive and are capable of making measurements with extreme accuracy. We will experiment with two general types of interferometers and a few applications of those instruments. This is especially true of the first surface mirrors.

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In this lab we will experiment with instruments that compare different beams of light. These instruments are remarkably sensitive and are capable of making measurements with extreme accuracy. We will experiment with two general types of interferometers and a few applications of those instruments. This is especially true of the first surface mirrors.

Do not eat food or have any drinks in the vicinity of the optical tables. Be very careful not to touch any optical surface with things like the screwdriver tip or the soldering iron. Do not over tighten any screws. Do not leave optical components just sitting on the optical table when not in use. Take the unused equipment and bolt it down to the optical table somewhere out of the way.

Figure 1. The data acquisition box and detector box. The exact configuration of this box is currently in flux, it might change a bit. The main parts are: Part 1: Michelson Interferometer. Part 2: Index of Refraction of Air. Part 3: Index of Refraction of a Glass Plate. Part 4: Fabry-Perot Interferometer.

There is some software written in LabVIEW that will not only collect your data for you but it will also count the fringes. Use whichever detector works best. If possible you should document your results with a digital camera. It is fairly easy to cast fringes onto a screen and then photograph the screen. Make sure the number of significant figures that you determine for the index of refraction of air and glass and the wavelength of the diode laser light are reasonable.

Part 1: Michelson Interferometer Construct the interferometer as shown in Figure 2. The Michelson Interferometer is incredibly useful and common, you will want to be comfortable with building this system quickly and efficiently.

To set the system up first run the laser beam down the center of the optical table. To set the height, determine a typical height for your optical components and adjust the laser to the center of that height. Use a ruler or your thumb and a ball-end driver to verify that the beam is horizontal.

Do this by measuring the beam height at two places, one near the laser and one near the far end of the optical table. Make sure the beam is running parallel to the side of the table, use the bolt hole pattern on the top of the optical table as a reference grid.

Note, the beam expanding lens is not inserted until nearly the end of the alignment process. Sometimes it is helpful to use a business card to locate the beam.

Do this by holding the edge of the business card near the center of the optical element the beam splitter in this case and adjusting the optical element so that the laser beam goes approximately through the center. Note: Be careful not to touch the optical surfaces with the business card. When you insert an optical element that has adjuster screws, start with the screws in a neutral position.

Make coarse adjustments with the entire mount by moving the base or by rotating the post in the post holder. Use the adjustment screws only for fine adjustments. Insert mirror 1 about 5 centimeters from the beamsplitter and adjust it so that the beam hits near the center of the mirror and returns though the beamsplitter and hits the screen. Similarly, insert mirror 2 in such a position as to keep the two arms of the interferometer approximately the same length.

Adjust mirror 2 so that beams 1 and 2 overlap on the screen. You might be able to see some hint of fringes by now such as the laser spot winking in and out. Finally, insert the beam expanding lens. Use a short focal length lens. It does not matter in this case if the lens is a positive or negative lens. Before you insert this lens, make a mental note of the position of the unexpanded laser beam. When you insert the beam expanding lens, adjust it and it only until the large expanded beam is approximately centered at the location of the previously unexpanded Figure 2.

Michelson interferometer, note that for this setup the distance between the mirrors, beamsplitter and the lens should be pretty tight and about the same. Doing this will insure that your lens is centered on the optical axis. You should have some hint of fringes by now. At this point you should turn the soldering iron on to warm up for the next part of the experiment. Set it safely out of the way.

Make careful adjustments of the fine adjust screws on one of the mirrors until the fringes on the screen are clear and large. You should be able to adjust the instrument such that you have only 1 to 2 large fringes across the surface. Describe your observations and answer the questions for the following situations: Case 1: Insert the tip of the hot soldering iron into the middle of one arm of the interferometer.

Insert it into the other arm, are the two arms symmetric? For the sake of comparison, insert some room temperature object such as the hex screwdriver tip, what is the effect? Question 1: What is happening and why? Case 2: Without actually blocking the beam path, hold your hand just below the light beams in one arm of the interferometer. Another interesting thing to try is to hold something cold, such as a can of soda, above one arm of the interferometer.

Questions 2: What do you see? Why is this happening? Part 2: Measuring the index of refraction of air. Note: You need to measure the room temperature and pressure at the day and time that you do this experiment. Your results will not match as well otherwise. Referring to Figure 3, reassemble your interferometer with the mirrors located about 20 to 30 cm from the beamsplitter.

Install the beam expanding lens placing it between the beamsplitter and the screen, i. As before, adjust the lens to center the expanded spot at the same place as the unexpanded dot was located.

Adjust the mirrors with the fine adjustment screws until you obtain a pretty set of fringes. Remove the beam expanding lens assembly by sliding it out of the post holder. Align the spots on the screen, i.

Reinsert the beam expanding lens. Fine adjust the interferometer to provide a spot with several fringes. You will want the screen far enough away to give easily visible fringes. While gently holding the air hose against the table to reduce shaking, use the vacuum pump to evacuate the air inside the test cell.

There are two valves that control the vacuum, one opens the cell to the pump and the other lets air back into the pump. While slowly pumping out the air, count the number of fringes that move past a Figure 3. A Michelson interferometer with large enough arms to admit the vacuum chamber. You can mount the chamber on a ring stand with a clamp. It does not matter which arm the chamber is in. Do you know why? Should you count dark and bright fringes or just dark or just bright fringes?

When you take your measurement you should run it several times and take an average. Make sure that you pump all the air out, the last bit of air is the slowest to remove, watch carefully to see that the fringes stop moving. What we are interested in is the change in these values. As we pump out the air, the only things that will change are the number of fringes and the index of refraction in part of one arm of the interferometer.

Hence we find that For gases we often report the value for the index of refraction as n-1 rather than as n because the value is so close to one. And, since the index for vacuum equals one by definition, we can write the last equation as Think carefully about your value, d, for the length of the cell.

Determine n air -1 from your measurements. You will obtain a more precise value next It is interesting to ponder the effect of atmospheric pressure and temperature on air. There are numerous empirical relationships for this complex phenomenon, one commonly used relationship is, where.

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Lab Interferometers.pdf

Fabryrot interferometer pdf Optical interferometers have made feasible a variety of precision. Interferometers can be classified as two-beam interferometers or multiple-beam. Interferometers are basic optical tools used to precisely measure earth changes and messages from the founders pdf wavelength. Interferometer, study the fringe patterns resulting from both a point source and a. A practical guide ebook find pdf to building and using your own interferometer. Interferometers work, how to build an interferometer and how to test telescope optics by.


Fabryrot Interferometer PDF

Mot Indosopubrgrsuanmathan conventional solid-state lasers. An implementation of the discussed scheme with a total of 16 transceivers is shown in the figure. In this example, transmitters and receivers are used to interferomeetr the standard CWDM transmission link comprising of 16 channels between and nm. There were three basic types of Ethernet transceivers: It also depends on the modal bandwidth, the maximum segment lengths is m. It is related to the distortion that occurs when multiple pulses of sunshine, although issued at the same time, arrive at the end of a fiber at slightly different times.

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