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OSE 5312 FUNDAMENTALS OF OPTICAL SCIENCE
Spring 2007
Mid Term Exam 2
Wednesday, March 28, 2007.
This is a open notes, open book exam. Answer all questions. Try to use drawings
& figures to help explain your answers. Clearly state all your assumptions,
definitions and approximations. The number of points for each question is given
in italics.
Useful Physical Constants are given on the next page.
________________________________________________________________
Name: ___________________________________
Question
Max
points
Score
Total 100
- a. List the names of four different optical absorption processes that can occur in a polar semiconductor. ( 8 points )
b. Briefly describe the physical nature of the absorption processes listed in question a (or in plain English: describe “what happens”) ( 8 points )
c. For each of the four processes, list the typical photon energies at which these absorptions can occur ( 4 points )
- The data below represent the real and imaginary refractive index of GaAs.
a. Use the table of elements to calculate the effective mass μ. for GaAs ( 10 points )
b. Based on the graph, give the approximate values of ωT and ωL for GaAs (10 points )
( note: the horizontal lines occur at values of 1,3, and 5 )
GaAs
(a) A Doppler-broadened line has an absorption spectrum, α(ω), with a FWHM of 10^10 r/s. find Δω, where:
2 0 0 ( )
( ) exp ω
ω ω αω α
(10 points)
(b) Explain, in less than 100 words, why Δω is larger than for an individual atom. (10 points)
- (a) A material consisting of chiral molecules has a magnetic susceptibility of 10 -5^ that results in a magnetization along the electric field component of an incident electromagnetic wave. How much is the polarization of a linearly polarized wave at a wavelength of 633 nm rotated by upon propagating through 5 cm of such a material? The refractive index is 1.5. (10 points)
(b) If transmitted linearly polarized light is reflected back through the material, what is its polarization state after the second pass? (10 points)
