Available Photonics Experiments:

P5881-1 Michelson’s laser interferometer I PDF Download page

  • Coherence of laser radiation
  • Two beam interference
  • Wave fronts
  • Fringe contrast
  • Coherence length
  • Fringe detection
  • Two mode HeNe laser
  • Longitudinal mode spacing
Principle of operation
The beam of the probe laser is expanded (BE) and divided into two beams at the beam splitter plate (BSP). One beam is directed to the mirror M1 and the other to M2. The returning beams are superimposed by the beam splitter plate and expanded by means of the concave lens (EL). The resulting interference pattern is imaged on a white screen. Depending on the beam divergence circular or linear fringes are generated and observed.
  • Examples of investigations and measurements
Set-up a Michelson’s interferometer
The beam of the HeNe probe laser (6) is expanded (11) and divided by the beam splitter plate (4) which is mounted into the adjustment holder (12). From here the beams are directed to the mirror (10) which are precisely adjustable (13) in such a way that the returning beams are exactly superimposed. A concave lens (2) expands the interference pattern of the superimposed beams on the white screen (15). By changing the divergence of the laser beam by adjusting the beam expander (11) the radius of curvature of the wave front is modified resulting in special interference pattern. For plane wave fronts linear and for curved ones circular interference pattern occur
Measuring the coherence length of the probe laser
The coherence length of a light source is determined by the bandwidth of its emission. To determine this important parameter one of the mirror holder (14) is provided with a gear and pinion drive allowing the mirror holder to be translated along the rail. By measuring the contrast at various position by means of the photo detector (5) and an oscilloscope the coherence length can be derived from the measured contrast function. Since the provided HeNe laser emits two orthogonal modes, the coherence length can be calculated ab initio and compared to the measured one.
  • P5881-1 Michelson laser interferometer 1 consisting of:
13L-03501BNC connection leads, set of 1
24B-00901Biconcave lens f=-10 mm, free opening 10 mm, click 25
34B-02401Optic cleaning set
44B-03901Beam splitter plate 50/50 @ 632 nm, mounted on 25 mm holder
5ED-02001Photodetector Si PIN
6LS-01501HeNe Pilot laser Ø30 mm
7MC-01701Target screen, click 25
8MC-02502Profile Rail MG-65, 300 mm
9MC-02702Laser adjustment holder, soft ring 30 mm, carrier 20 mm
10PM-00302Laser mirror 1/2”, flat, HR @ 632 nm, click 30 mm
11PM-00601Beam expander 8x, click 25 mm
12XM-01501 Angle joint mount OCM 650 cross-piece with adjustable prism stage, theta, phi
13XM-01601Laser mirror adjustment holder 30 mm opening and carrier
14XM-01701Laser mirror adjustment holder 30 mm opening with carrier and longitudinal
15XM-04701Screen with carrier 20 mm
16XM-10903Mounting Plate, including carrier 20 mm, C 25
17XM-90301Profile Rail OCM 650, 500 mm with gear rack 200 mm
 Required Options: 
 TP-01001Oscilloscope 100 MHz digital, two channel
 XM-04501Motorised translation unit with triple reflector, travel 50 mm
 XP-10401Technical laser interferometer extension
 XP-10801Set of spare parts