Download Laser Beam Profiling Using a Scanning Knife Edge-Physics-Lab Report and more Exercises Physics in PDF only on Docsity! Laser Beam Profiling Using a Scanning Knife Edge Technique Submitted to: Dr. Asloob Ahmad Mudassar Submitted by: Yasir Ali M.Phil. Physics DPAM PIEAS docsity.com Objective: To investigate spatial characteristics of a He-Ne Laser using Scanning Knife Technique. To measure the FWHM (full width half maximum) and 1/e 2 diameters of the beam. Introduction In every laser application, whether in medical, industrial, laser printing, marking, welding and cutting, or fiber optics, the beam profile provides valuable information for the most efficient use of the laser. In laser industry it is desired to measure laser beam profile before its use. The beam profile tells all about the beam’s spatial characteristics, which in turn describe the distribution of beam’s energy, propagation, beam quality and utility of the beam. By knowing beam profile we get information about shape of beam and can improve it for our applications. Profiling is particularly helpful in building optical systems for laser printers and fiber optic collimators. Until you know the beam profile, it is difficult or even impossible to put the laser light to use. TEM mode:- Transverse modes are those modes in laser output beam which lie in direction perpendicular to beam. These are observed by focusing laser beam on screen. In a He-Ne system where you can adjust the position of one of the mirrors, the transverse modes are seen by misaligning (making slightly unparallel) the two mirrors Figure.1 Different transverse modes. that define the laser cavity. Transverse modes are represented by ordered integral docsity.com Ib= 0.7 and X1=4.5 and X2 = 14 distance is in micrometers and intensity is in mV. Position(µm) Intensity Position(µm) Intensity Position(µm) Intensity Position(µm) Intensity 4.5 3.33 7 3.21 9.5 1.91 12 0.79 5 3.33 7.5 3.04 10 1.64 12.5 0.72 5.5 3.33 8 2.82 10.5 1.35 13 0.7 6 3.32 8.5 2.58 11 1.11 13.5 0.7 6.5 3.3 9 2.25 11.5 0.93 14 0.7 D1/2= 14.51-6.5 = 8.01 µm or diameter D2= 16.02 µm. Here Ib=0.25 , x1 =6.5 and x2 = 15.5 distance is in micrometers and intensity is in mV. Position(µm) Intensity Position(µm) Intensity Position(µm) Intensity Position(µm) Intensity 6.5 2.31 9.0 2.08 11.5 1.3 14.0 0.3 7.0 2.29 9.5 1.93 12.0 1.04 14.5 0.26 7.5 2.28 10.0 1.85 12.5 0.81 15.0 0.25 8.0 2.26 10.5 1.74 13.0 0.59 15.5 0.25 8.5 2.19 11.0 1.58 13.5 0.42 docsity.com D1/2= 13.89-6.18 = 7.71 µm or diameter = 15.42 µm. Here Ib= 0.26, x1=5 and x2= 14.5. Distance is in micrometers and intensity is in mV. Position(µm) Intensity Position(µm) Intensity Position(µm) Intensity Position(µm) Intensity 5 0.94 7.5 0.89 10 0.62 12.5 0.29 5.5 0.94 8 0.87 10.5 0.58 13 0.28 6 0.94 8.5 0.83 11 0.54 13.5 0.26 6.5 0.92 9 0.78 11.5 0.45 14 0.26 7 0.91 9.5 0.72 12 0.37 14.5 0.26 From above observation we can find that Therefore D= 15.707µm. Precautions:-. As this experiment give results intensity based, therefore care should be taken about background radiations. Make sure that small light is reflected from your clothes so results are not affected. docsity.com
