00000EC469121903 Pages: 2

Reg No.: Name:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
Seventh Semester B.Tech Degree Regular and Supplementary Examination December 2021 (2015 Scheme)

Course Code: EC469
Course Name: OPTO ELECTRONIC DEVICES
Max. Marks: 100 Duration: 3 Hours
PARTA
Answer any two full questions, each carries 15 marks. Marks

1 a) Derive the equation for radiative recombination efficiency or internal quantum (7)
efficiency.
b) Derive the equation for threshold condition for lasing operation and derive the (8)

expression for threshold gain.

2 a) Write short notes on hetero-junction laser. (7)

b) Briefly describe the heat sources in optoelectronic devices. (8)

3 a) Describe the structure and working of DBR lasers. (7)

b) Describe the structure and working of tunneling based lasers. (8)
PART 13

Answer any two full questions, each carries 15 marks.
4 a) Describe the materials used and principles of operation of white light sources (5)

based on wavelength converters.

b) Calculate the change in refractive index in GaAs for an applied electric field of (5)
2x10° V/em.

c) Explain the material properties and applications of nitride light emitters. (5)

5 9) Explain the structure and working of Raman-Nath modulator. (5)

b) Calculate the value of Vz for GaAs amplitude modulator when the wavelength (5)
of the incoming light is 1.1 um. The waveguide is | um thick and 1.5 mm long.
c) Differentiate between electro-optic and acousto-optic modulators. (5)
6 a) What is electro-optic effect? Explain how this effect can be used for modulating (8)
the phase of the optical signal.
b) With the help of an emission spectrum, explain the generation of white light by (7)

trichromatic sources.

Page lof 2