White light Interferometry
Links about Michelson Interferometers
Sodium-vapor lamps uses excited sodium atoms to create its signature yellow colored light. It is a great monochromatic light source and is very efficent due to the fact that is uses all its supplied current to create light. Sodium lamps get very hot so when in use one has to be careful about touching the bulb or casing.
While switching the bulbs on one of our lamps, we noticed that the bulb seemed to flicker when looked at through the corner of your eye. When trying to take an image or a video of the lamp a visual band of darkness could be seen moving across the light. To test whether the lamp was flickering, we used a photodetector attached to an oscilloscope, if the lamp is actually flickering a pulse like image should appear on the oscilloscope. After some tuning on the oscilloscope, a pulsed wave appeared indicating that the lamp was indeed flickering. When seen from the corner of your eye, the lamp appears to be flickering quite fast but when viewed through a camera it slows down. This occurs because of the FPS rate of the camera and of the frequency at which the lamp is flickering at. I believe if the FPS rate is the same as the lamp's frequency, the lamp won't appear to flicker while if the fps rate is above or below the lamp's frequency the flickering will appear faster or slower.
White Light Source
The white light source that we used to align the interferometer was a Fiber-Lite Model 3100 with a EKZ lamp. In general white light sources have a pretty broad optical bandwidth, in this case the white light source was emitting visible white light ranging mainly from 490 nm to 742 nm, which was measured using the lab's spectrometer. It is also possible to have a white light source that emits in non-visible spectral regions.
From Laser Light to White Light
Loosely following the procedure described in this lab experiment done at William and Mary, it was possible to align the interferometer so as to produce white light fringes. Progressing from laser light to white light in the steps described gives an easier transition for the changing coherence and a much easier time for finding interference fringes.
Progression of Set-up
"Sodium Lamp". M. Whelan,Rick DeLair. http://www.edisontechcenter.org/SodiumLamps.html