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Fraunhofer Single Slit
The diffraction pattern at the right is taken with ahelium-neon
laserand a narrow single
slit.
More conceptual details about single slit diffraction
The active formula below can be used to model the different
parameters which affect
diffraction through a single slit. Enter the available
measurements or model
parameters and then click on the parameter you wish to
calculate.
Displacement y= (Order m xWavelengthxDistance D)/(slit width
a)
For a slit of width a = micrometers = x10^ m
and light wavelength = nm at orderm = ,
on a screen at distance D = cm
the displacement from the centerline for minimum intensity will
be
= cm.
http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasgas.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasgas.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasgas.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinslitd.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinslitd.html#c1http://var%20cal%3Ddisp%28%29/http://var%20cal%3Ddisp%28%29/http://var%20cal%3Dwav%28%29/http://var%20cal%3Dwav%28%29/http://var%20cal%3Dwav%28%29/http://var%20cal%3Ddist%28%29/http://var%20cal%3Ddist%28%29/http://var%20cal%3Dslit%28%29/http://var%20cal%3Dslit%28%29/http://var%20cal%3Dslit%28%29/http://var%20cal%3Dslit%28%29/http://var%20cal%3Ddist%28%29/http://var%20cal%3Dwav%28%29/http://var%20cal%3Ddisp%28%29/http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinslitd.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasgas.html#c1
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This corresponds to a diffraction angle of = .
This calculation is designed to allow you to enter data and then
click on the quantity
you wish to calculate in the active formula above. The data will
not be forced to be
consistent until you click on a quantity to calculate. Default
values will be entered forunspecified parameters, but all values
may be changed.
Note: Thesmall angle approximationwas not used in the
calculations above, but it is
usually sufficiently accurate for laboratory calculations.
Birefringence of crystals can modify the Polarization State of
light which is very useful in manyapplications. This type of
optical components are called birefringent wave plates or
retardation plates (orjust wave plates or retarders for short).
The velocities of the extraordinary and ordinary rays through
the birefringent materials vary inversely withtheir refractive
indices. The difference in velocities gives rise to a phase
difference when the two beams
recombine. In the case of an incident linearly polarized beam
this is given by a=2 d(ne-no)/(-phasedifference; d-thickness of
waveplate; ne, no-refractive indices of extraordinary and ordinary
rays
respectively; -wavelength). At any specific wavelength the phase
difference is governed by the thicknessof the waveplate.
Red Optronics provides the following waveplates: octadic-wave
(/8), quarter-wave (/4), half-wave (/2)
and full-wave () plates.
Half Wave Plate
The half wave plate can be used to rotate the polarization state
of a plane polarized light as shown inFigure 1.
Suppose a plane-polarized wave is normally incident on a wave
plate, andthe plane of polarization is at an angle q with respect
to the fast axis, asshown. After passing through the plate, the
original plane wave has been
rotated through an angle 2.
A half-wave plate is very handy in rotating the plane of
polarization from apolarized laser to any other desired plane
(especially if the laser is toolarge to rotate). Most large ion
lasers are vertically polarized. To obtainhorizontal polarization,
simply place a half-wave plate in the beam with its
fast (or slow) axis 45 to the vertical. The /2 plates can also
change left circularly polarized light intoright circularly
polarized light or vice versa. The thickness of half waveplate is
such that the phase
difference is 1/2 wavelength (/2, Zero order) or certain
multiple of 1/2-wavelength [(2n+1)/2, multipleorder].
Quarter Wave Plate
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Quarter wave plate are used to turn plane-polarized light
intocircularly polarized light and vice versa. To do this, we must
orient thewave plate so that equal amounts of fast and slow waves
are excited. Wemay do this by orienting an incident plane-polarized
wave at 45 to the fast
(or slow) axis, as shown in Figure 2. When a /4 plate is double
passed,
i.e., by mirror reflection, it acts as a /2 plate and rotates
the plane of
polarization to a certain angle, i.e., 90. This scheme is widely
used inisolators, Q-switches, etc.
The thickness of the quarter waveplate is such that the phase
difference is 1/4 wavelength ( /4, Zero
order) or certain multiple of 1/4-wavelength [(2n+1)/4, multiple
order].
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