PHYS 408
Applied Optics
(Lecture 13)
JA N - A PRIL 2 0 1 6 E DI T ION
JE F F YOUN G
AMPEL RM 113
Midterm Survey
12 responses before midterm, 10 post midterm, no major differences:
The good: generally happy with lecture format, with activities, emphasis on concepts, and
practical examples
The not so good: most concern over homework being hard and long and perceived as not
useful; pre-reading doesn’t necessarily help with concepts; some requests for more clearly articulated
questions, and more details in posted lecture slides; use data cam instead of board; cover stuff in
lecture directly related to solving homework problems
Self analysis: largely that should spend more time doing pre-reading and getting to class, and
starting homework earlier
-
Peer analysis: wake up and participate more
-
Workload: 10-14 hr/wk
-
TA assistance (lecture and labs); generally positive
Discuss
My analysis of results
Possible changes:
A)
Can use data cam if you prefer (test drive and vote?)
B)
Make sure we reiterate explain clearly what the question is asking for in lectures
C)
Pre-reading: encourage you to just Google or Wikipedia the general topic that is going to be covered?
D)
Be more clear in homework question expectations.
Prefer not to change:
E)
more math and homework related content in lectures (that is what the help sessions are for, and hardly
anyone is showing up)
F)
I have been adding more notes to the lecture slides…can add more, but also want to encourage notetaking and attendance….?
G)
Note sure about homework: a large part of what you will be expected to do in a job involves analysis
and numerical solution of problems….quantity is less than in previous years…
Quick review of key points from last
lecture
Gaussian beams have various mathematical representations, but fundamentally are
characterized by only two independent parameters.
Can choose the independent parameters from (R(z), w(z), z0, w0, l, etc.), but once you
know those two independent parameters, you can define the Gaussian function
everywhere in space.
The radius of curvature of the Gaussian wavefronts is infinite at z=0 and z=+ infinity and
– infinity, and is a minimum (most curved) at z= z0, where z0 is the Rayleigh length.
They are only useful in practice for paraxial beams that do not diverge “too much”
The q parameterization
The real and imaginary parts of 1/q
Follow q through a paraxial optical system
The ABCD Matrix: Ray Optics
Fundamentally based on
Fermat’s Principle, which is?
Fermat’s Principle
Examples
Examples
Examples
Gaussian Example #1
(free space propagation)
Gaussian Example #2
(effect of a thin lens)
From the sketch, what are q1 and
1/ q1 at entrance to lens?
What is the relevant ABCD
matrix to propagate just
through the lens?
What are q2 and 1/ q2 just after
the lens?