Presentation

1. Presented by
• Ali zia (Bsf1702570)
• Hafiz Muhammad Ubaid Arif (Bsf1702533)
• Muhammad Tahir Mehmood (Bsf1702589)
• Muhammad Mashhood (Bsf1601428)
• Jafar Nadeem Bhatti (Bsf1702454)

2. Interferometry

3. Interferometer
• An interferometer is an optical device which utilizes the concept of
interference. Typically it starts with same input beams, split it into
separate beams with some kind of beam splitter(a partially
transmissive mirror), possibly exposes some of these beams to some
external influence, and then combine the beams on a surface to
visualize the pattern of fringes being formed.

4. Principle
• If two rays of same wavelength meet at some point mutual
interference occurs & mutual interference depends upon phase of
two waves at their meeting points.
• If two rays are in same phase then the resulting intensity will be the
sum of two intensities.
• If two rays are out of phase the resulting intensity will be the
difference of two intensities.
• If two rays having the same amplitude are in same phase, then the
resultant will be twice and result will be bright spot and vice versa.

5. Typical Interferometer
• The expanded beam exiting from the light source is divided by a Beam
splitter into two beams.
• One beam is reflected from the Reference Mirror, and the other one
from the Sample.
• These two beams are recombined by the Beam splitter to interfere.
• The imaging lens images the interferogram onto the CCD camera.

6. Optical Path Difference (OPD)
- difference in optical path lengths that
beams travel in Reference and Test arms

7. Michelson's interferometer
• A Michaelson interferometer is a tool to produce interference
between two beams of light.
• Michelson interferometer produces interference fringes by splitting a
beam of monochromatic light such that one beam hits a fixed mirror
and the other a movable mirror. When the reflected beams are
combined an interference pattern is formed.
• To create interference fringes on a detector the path has to be of
different lengths or composed of different materials.

8. Construction
• The main optical path consists of two highly polished mirrors and a plane
parallel plate of glass(compensator) and a beam splitter.
• sometimes the rear side od the beam splitter is slightly silvered so that
coming light is converted into a reflected and transmitted light of equal
intensity.
• To obtain interference fringes two mirrors are made exactly perpendicular
to each other.
• Even when these adjustments have been made, fringes will not be seen
unless tow important requirements are fulfilled
1. Light must originate from an extended source
2. The light must generally be monochromatic or nearly so.

11. Working and interpretations
• For certain path lengths the waves are in phase when combined, and
constructive interference occurs.
• Moving the mirror changes the position at which light interferes
constructively or destructively.
• The interference pattern is projected onto a surface as a series of
concentric rings of light and dark.
• With a path difference of an integral of wavelength of light bright
fringes appear due to the constructive interference.
• With a path difference of odd multiple of half wavelength of light
destructive interference pattern or dark bands are formed.

12. Interferogram