![]() Temporal (or longitudinal) coherence implies a polarized wave at a single frequency, whose phase is correlated over a relatively great distance (the coherence length) along the beam. Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have a very low divergence to concentrate their power at a great distance. Spatial (or transverse) coherence is typically expressed through the output being a narrow beam, which is diffraction-limited. Lasers are distinguished from other light sources by their coherence. This permits a much smaller emitting area due to the much greater radiance of a laser and avoids the droop suffered by LEDs such devices are already used in some car headlamps. Semiconductor lasers in the blue to near-UV have also been used in place of light-emitting diodes (LEDs) to excite fluorescence as a white light source. Lasers are used in optical disc drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optic, and free-space optical communication, semiconducting chip manufacturing ( photolithography), laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. Alternatively, temporal coherence can be used to produce ultrashort pulses of light with a broad spectrum but durations as short as a femtosecond. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Spatial coherence also allows a laser beam to stay narrow over great distances ( collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Ī laser differs from other sources of light in that it emits light that is coherent. The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. The word laser is an anacronym that originated as an acronym for light amplification by stimulated emission of radiation. Red (660 & 635 nm), green (532 & 520 nm), and blue-violet (445 & 405 nm) lasers A laser beam used for weldingĪ laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Discuss, both qualitatively and quantitatively theĬhallenges associated with making Blue-ray discs and Blue-ray readers."Lase" redirects here. Holds 700 Megabytes of data, determine the storage capacity of a DVD.Ĭheck your results. Įxplain carefully how you arrived at your prediction. Extrapolateįrom your results to predict a storage ratio. Your results), determine the track spacing on the CD and DVD. Using two different color lasers (average You will need to reflect a laser off of the surface to see the Should be able to remove a small area of the coating. By scraping the CD surface and then applying strong tape, you ![]() The main challenge is that both CDs and DVDs haveĬoatings. Track separation (using the same process as you used for finding the thickness Should be able to produce a diffraction pattern and use it to determine the By shining a laser on one of the discs, you Procedure: At your station you should find In CDs and DVDs and deduce the ratio of their storage capacities. Of this exploration is to use laser diffraction to measure the track separation Most modern computers have opticalĭrives that use lasers to read information from spinning discs. You should also include all derivations of the formulas governing this phenomena that you used to deduce the hair/wire thickness.Ĭompact Discs and DVDs are the most common and least expensive portable storage Your report should include a carefully written discussion of Single Slit Interference, including diagrams showing how light interferes to create the patterns you observed in the lab. For each, you will need to explain exactly how you deduced the thickness from the fringe spacings and the geometry of your setup. Measure the thickness of two different thin wires/hairs. Once you have done this, you should be able to use your results to determine the thickness of hair/wire you used. Once you understand the theory behind a single slit diffraction pattern (which is different from a double slit interference pattern), you will need to deduce analytically/mathematically the connection between the light/dark fringe spacings and the thickness of the hair. Your group should research "Single Slit Interference". Unlike the other labs this this quarter, this lab requires you to research the observed phenomena independently. Diffraction Pattern made by shining a Laser on a Hair
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