Transcript Advanced Optics Lab at San Jose State University Ramen

Advanced Optics Lab at San
Jose State University
Ramen Bahuguna
Department of Physics
• We meet once a week for 4 hours. One
hour lecture+3 hours of Lab
• There are about 6 labs and one project.
The project takes about a month
• The prerequisite is Physics 158 Optics
course using Pedrotti or Hecht’s book
We do the following experiments:
• Experiment (1) (Lecture on “Familiarity with
optical techniques and optical components)
• Cleaning of Optics
• Aligning a laser beam through a narrow glass
tube with two plane mirrors
• Aligning a spatial filter for filtering an expanded
laser beam
• Collimating an expanded Laser beam using a
wedged plate shearing interferometer
• Rotation of Polarization by two reflections
• Use of wave plates
• Use of Beam Splitters (cube as well as variable
• Experiment (2): (lecture on refraction in a
prism)
• Measuring refractive index of a liquid placed in a
hollow prism by minimum deviation method
• Experiment (3): (Lecture on Geometrical
Optics-imaging with lens combinations)
• imaging with a single lens
• imaging with concave and convex mirrors
• imaging with lens combinations
• real and virtual images
• proper use of a doublet to collimate a beam
• Experiment (4): (Lecture on Interferometery)
• (a)Alignment of a Michelson Interferometer
using three techniques
• (b)Measurement of refractive index of air with a
Michelson Interferometer
• Experiment (5): (Lecture on Holography and
diffraction Gratings)
• (a)Fabrication of a Reflection Hologram
• (b)Fabrication of a Holographic Diffraction
Grating and determining its diffraction efficiency
• Experiment (6): (Lecturer on Fourier
transforming properties of lenses)
• (a)Abbe-Porter experiment in Fourier Optics.
• (b) Different Fourier transforming configurations
using a lens: scaling properties
• Experiment (7): (Lecture on Subjective and
Objective laser speckles)
• (a) measurement of small translation of a diffuse
object by Laser Speckle Photography
• (b) measurement of small rotation of a diffuse
object by laser Speckle Photography
• Experiment (8): (Lecture on Holographic
Interferometry)
• Measurement of small rotations of a diffuse
object by Holographic Interferometry
PROJECTS
• Student Grating Spectrometer
• (a) building a collimator
A variable slit is provided to the students. They are
supposed to select a doublet lens of the proper focal
length from a catalog such that for a typical source the
lens is substantially illuminated. This in turn will
illuminate a substantial part of the grating which will
result in higher resolution.
• (b) building a telescope
The students select two doublet lenses for the telescope
keeping in mind the fact that they have to overfill the
pupil of their eyes so that the spectrum does not
disappear on moving one's head slightly. Over filling the
pupil will result in loss of intensity.
• (c) Fabrication of a holographic
diffraction grating
The students are asked to fabricate a
holographic grating with 600 lines/mm.
They calculate the angle between the two
plane waves by the formula: d= λ/(2sinθ)
A laser beam is expanded, collimated and then split with
a beam splitter and then combined with the help of
mirrors on a holographic plate (PFG-01). Once
fabricated, the grating constant is determined by
diffracting a laser beam.
• (d) Mounting of the collimator, telescope and the
grating on the turn table provided.
All the components are mounted on the turn table and
aligned. Interaction with the mechanical shop is key to
the success of the project. Finally the spectrometer is
tested with a known spectrum.
Fingerprint Sensor
• In this project the students are asked to study a
patent on Fingerprint sensor based on Total
Internal Reflection. They are asked to select a
prism from a catalog with parameters close to
that mentioned in the patent. They are also
provided with a CCD camera.
• (a) The Light Source. The students come up
with several LEDs' as a source of uniform
illumination of the finger.
• Image Capture. They calculate the
viewing angle from the given formula.
Viewing at this angle reduces the keystone
image. They are also asked to derive the
formula from the fundamentals.
finger
image of fingerprint
LED source
Camera l lens
Refractive Index measurement of a
given liquid
• In this project the students measure the refractive index
of several liquids. The principle is based on the well
known "Apparent depth technique" but with better
precision.
• (a) Expansion and collimation of the laser beam
A He-Ne laser is used as a source of light. The laser light
is expanded by means of a microscopic objective. The
beam is spatially filtered through a pin hole to remove
diffraction artifacts. A hollow glass cell is placed in the
path of the expanded beam. The expanded beam is
collimated by a doublet mounted on a axial translational
stage. The collimation is tested with a parallel plate
shearing interferometer. The reading on the translational
stage is recorded.
• (b) Testing Collimation after the cell is filled
with the desired liquid
The glass cell is then filled with the given liquid.
The collimation is obviously disturbed due to the
apparent position of the laser point source. The
lens is translated to get back the collimation
using the interferometer and the new position of
the stage recorded. From the two data one can
easily calculate the refractive index of the liquid
by the well known formula:
N= Real Depth/Apparent Depth
Interference
bands on
screen
Laser
point
source
Collimated
beam
Liquid
cell
lens
Wedged
plate