Name: SOLUTIONS
ECE 55200 Midterm Exam
Spring 2025
Purdue University
Show all your work for the following problems so that partial credit can be assigned. Cross out
clearly any work which is to be disregarded. Be certain that your answer is distiguishable from
your work. You may use extra paper for your answers if necessary. Be sure to put your name on
each page of your exam, and label the problem number on each page of your work. Use units
where required. Be sure that your work, discussions and explanations are clear, concise and
organized.
You may use a calculator. It’s open book and open notes test. You can also use the class info
available on the Brightspace.
Problem Max. Points Score
1 30
2 30
3 40
Total
Page 1
, Name: SOLUTIONS
1. Consider the following cavity bounded by two mirrors and containing an optical element
T whose ABCD matrix is shown. Assume there are no spaces between the mirrors and the
optical element.
R
/ cosαC sinCα3
T =∣
α3cosCα3J∣
-sinC3
a. [ 10 points] Sketch the unit cell for the cavity starting with mirror R. Indicate the unit
cell boundaries clearly!
SOLUTION: Show the unit cell with the lens and the optical element twice.
b. [ 10 points] Determine the ABCD matrix for the unit cell from part a.
SOLUTION:
Page 2
ECE 55200 Midterm Exam
Spring 2025
Purdue University
Show all your work for the following problems so that partial credit can be assigned. Cross out
clearly any work which is to be disregarded. Be certain that your answer is distiguishable from
your work. You may use extra paper for your answers if necessary. Be sure to put your name on
each page of your exam, and label the problem number on each page of your work. Use units
where required. Be sure that your work, discussions and explanations are clear, concise and
organized.
You may use a calculator. It’s open book and open notes test. You can also use the class info
available on the Brightspace.
Problem Max. Points Score
1 30
2 30
3 40
Total
Page 1
, Name: SOLUTIONS
1. Consider the following cavity bounded by two mirrors and containing an optical element
T whose ABCD matrix is shown. Assume there are no spaces between the mirrors and the
optical element.
R
/ cosαC sinCα3
T =∣
α3cosCα3J∣
-sinC3
a. [ 10 points] Sketch the unit cell for the cavity starting with mirror R. Indicate the unit
cell boundaries clearly!
SOLUTION: Show the unit cell with the lens and the optical element twice.
b. [ 10 points] Determine the ABCD matrix for the unit cell from part a.
SOLUTION:
Page 2
