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UNIVERSITY OF VICTORIA

FINAL EXAMINATIONS APRIL 2013

ELEC 434 – Biophotonics – SECTION(S) A01

CRN 27564 

NAME: STUDENT NO.: V00

INSTRUCTOR: Dr. Tao Lu SECTION: A01

DURATION: 3 HOURS

TO BE ANSWERED ON THE PAPER 

STUDENTS MUST COUNT THE NUMBER OF PAGES IN THIS EXAMINATION

PAPER BEFORE BEGINNING TO WRITE, AND REPORT ANY DISCREPANCY

IMMEDIATELY TO THE INVIGILATOR.

THIS EXAM HAS 4 PAGES, INCLUDING THIS COVER SHEET AND

INSTRUCTIONS

1.  Text book and class notes are allowed,

2. 

Only university-approved models of calculators are allowed,

3.  Write down the final results on the exam sheet and the intermediate steps on the

booklet.

4.  Laptop/ipad is allowed for reading ebooks only. No internet connection is allowed

during the exam period.

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2ELEC 434 Biophotonics

1.  [25pts] A Fabry-Perot laser diode operating in continuous wave mode. Its gain medium has a

refractive index of ( = 1.45). It emits laser around 800 nm wavelength with an average power of

100 mW and forms a beam spot of 1 mm in diameter. The cavity loss is = 50cm-1 and the cavity

length is = 250 and MPE is 0.001W/cm2.

a. 

[5pts]Compute the central wavelength closest to 800: = _________________ nm;

 b.  [5pts]Calculate the Free spectral range in wavelength Δ = _______________nm;

c. 

[5pts]Calculate Reflectivity at the end facets = ______________________;

d.  [5pts]Calculate the total loss = _____________________cm-1;

e.  [5pts]The suitable laser protective goggle should have an OD reading

above______________.

2.  [25pts]Assume the laser diode in Question 1 operates as a mode locked laser, 50 longitudinal modes

are locked with an average power of 100 mW, the beam spot is still 1 mm in diameter,

a.  [5pts]Estimate the repetition rate_______________s-1;

 b.  [5pts]Estimate the pulse width________________s;

c.  [5pts]Calculate the total energy in each pulse _____________J;

d.  [5pts]Calculate peak power___________________W;

e.  [5pts]The suitable laser protective goggle should have an OD reading

above______________.

3. 

[5pts]The fluorescence intensity of a specimen is plotted in Fig. 1. If the fluorescence photons

detected at 1 = 1 ms is 1 = 100 and at 2 = 1.5 ms is 2 = 10, the fluorescence lifetime of the

specimen is = ___________________________ms.

Fig. 1

Time

   N  u  m   b  e  r

  o   f   f   l  u  o  r  e  s  c  e  n  c  e

  p   h  o   t  o

  n  s   d  e   t  e  c   t  e   d

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3ELEC 434 Biophotonics

4.  [30pts]A finite-tube-length microscope illuminated with green light = 532  is shown in Fig. 2,

the target resolution of the microscope is = 1  along the transverse direction, the eyepiece

magnification is =10×, and its diameter is = 2 to match the pupil of human eye;

The diameter of the objective lens is = 2. Neglect the distance between eye and eyepiece

and assume the numerical aperture of the objective lens equals to that computed in e).

a. 

[3pts]In order to view the image comfortably, the distance between the eyepiece and final image

is: = _________________________ ;

 b.  [3pts]The circle of confusion of a naked eye at the distance above is = __________ ;

c.  [3pts]The minimum magnification of the objective lens is = _______________________;

d. 

[3pts]The minimum numeric aperture of the eyepiece lens due to Rayleigh criteria is

= ____________________;

e.  [3pts]The minimum numeric aperture of the object lens is = _________________;

f.  [3pts]The focal length of the eyepiece is   = _______________________________ ;

g.  [3pts]The working distance between object and objective lens is = ______________ ;

h.  [3pts]The distance between the eyepiece and objective is = _______________________ ;

i. 

[3pts]The focal length of the objective lens is   = _______________________________ ;

 j.  [3pts]The depth of focus is = ________________________________________________ .

5. [15pts] Describe the operational principle of optical coherent tomography:

 ________________________________________________________________________

 ________________________________________________________________________

 ________________________________________________________________________ 

 ________________________________________________________________________ 

 ________________________________________________________________________ 

 ________________________________________________________________________ 

 ________________________________________________________________________ 

 ________________________________________________________________________

===============================End=============================

          object 

Objective lens  eyepiece 

Fig. 2