Available Photonics Experiments:

P5831 Interferometer
PDF Download page

  • Michelson's interferometer
  • Mach Zehnder interferometer
  • Interference
  • Index of refraction of air
  • Wavelength of light
  • Beam expander
  • Beam splitter
  • Examples of investigations and measurements
Michelson Interferometer
The emission of the laser (5) has a wavelength of 532 nm. The beam is expanded by a factor of 2.7 by the beam expander (3) which is mounted into a mounting plate. The beam splitter of module (A) divides the beam into two beams with equal intensity. The reflected beams are recombined by the beam splitter in such a way that the interference pattern is imaged to the white screen (8). To enlarge the image a biconcave lens (2) placed in front of the white screen is used.
The interference of both beams can be aligned by the adjustment screws of the mirror adjustment holder as well as by the fine pitch adjustment screws of the 4 axes laser adjustment holder. In case of almost plane wave fronts the interference pattern will show stripes and turns into rings when the divergence of the laser beam is changed by misaligning the beam expander
Mach Zehnder Interferometer
By rearranging the components a Mach Zehnder interferometer is composed. On the contrary to the Michelson setup the beam splitter and combiner are different components. The beam of the laser (5) is directed without expansion to the beam splitter of the module (13). One part of the beam is deflected by means of the adjustable mirror of the module (13). The other beam is deflected by the mirror of the module (12). Both beams are superimposed with the adjustable beam splitter unit of module (12). The resulting interference pattern is enlarged by means of the biconcave lens (2) and imaged to the white screen.
Once the interferometer has been aligned the impressive high precision measurements of the index of the air are performed.

The index of refraction of air depends mainly on the pressure (p) and the absolute temperature (T). The task of this experiment is to measure the index of refraction by using a cell as shown in the figure on the right. The change the pressure inside the cell is done by the provided manual pump which operates from vacuum (100 mBar) up to 3 Bar. The pressure cell has a separate in and outlet so that also other gases than air can be measured.The cell is placed in one arm of the Mach Zehnder interferometer. The number of fringes is counted when changing the pressure. With the known optical length of the cell the index of refraction can be calculated

   
   
  • P5831 Optical Interferometer consisting of:
ItemCodeQtyDescription
12B-12201Angle joint, four way cross type
24B-00901Biconcave lens f=-10 mm, C25 mount
34B-07241Beam expander magnification 2.7x
4ED-00101Adaptive power supply APS-05
5LS-01101DIMO diode laser module, 532 nm
6MC-00021Profile Rail MG-65, 200 mm
7MC-01001Screen holder on carrier 20
8MC-01121Screen 80 x 40 mm, horizontal and vertical scale
9MC-02501Profile Rail MG-65, 300 mm
10MC-02601Optical rail MG 65, 500 mm
11XM-06901Gas cuvette assembly
12XM-07101Mach Zehnder beam combining assembly
13XM-07401Mach-Zehnder beam splitting assembly
14XM-10902Mounting plate C25 with carrier 20 mm
15XM-11101Adjustment holder, 4 axes, carrier 20 mm