G192121 Pages:2

Reg No.:_ Name:

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

SEVENTH SEMESTER B.TECH DEGREE EXAMINATION(R&S), DECEMBER 2019

Max. Marks: 100

1 ஐ
b)
2 ಬ
b)
3 a)
b)
4 a)
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5 a)
b)
6 ஐ

Course Code: EC469
Course Name: OPTO ELECTRONIC DEVICES

PARTA
Answer any two full questions, each carries 15 marks.

Derive an equation for radiative lifetime for spontaneous band to band
recombination.

With the help of suitable diagram discuss band to band absorption and
recombination process in semiconductor.

Explain the need for laser cavity.

With the aid of suitable diagram discuss heterojunction laser. Mention two
disadvantage of homogeneous laser.

Discuss the principle of exciton absorption and free carrier absorption

Find out total number of longitudinal modes and frequency spacing between the
modes of an AlGaAs laser supported by the gain spectrum which has a
bandwidth of 6 nm. The laser has a cavity length of 200 ‏سر‎ and the emission

wavelength is 800 nm. (Assume n, = 3.6)

PART B

Answer any two full questions, each carries 15 marks.
Explain the generation of white light using dichromatic light emitting diode
Draw the structure of InGaN/GaN light emitting diodes and discuss the
properties of such light emitting diodes
Differentiate between Kerr and Pockel effects
What is meant by electro-optic effect? Explain the working principle of electro-
optic phase modulator.

Explain the generation of white light using wavelength convertors

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Duration: 3 Hours

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