The Semiconductor Injection Laser

Optical Communications

This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on “The Semiconductor Injection Laser”.

1. Stimulated emission by recombination of injected carriers is encouraged in __________
a) Semiconductor injection laser
b) Gas laser
c) Chemist laser
d) Dye laser

2. In semiconductor injection laser, narrow line bandwidth is of the order?
a) 1 nm or less
b) 4 nm
c) 5 nm
d) 3 nm

3. Injection laser have a high threshold current density of __________
a) 104Acm-2 and more
b) 102Acm-2
c) 10-2Acm-2
d) 10-3Acm-2

4. ηT is known as slope quantum efficiency.
a) True
b) False

5. The total efficiency of an injection laser with GaAs active region is 12%. The applied voltage is 3.6 V and band gap energy for GaAs is 2.34 eV. Determine external power efficiency.
a) 7.8 %
b) 10 %
c) 12 %
d) 6 %

6. In a DH laser, the sides of cavity are formed by _______________
a) Cutting the edges of device
b) Roughening the edges of device
c) Softening the edges of device
d) Covering the sides with ceramics

7. A particular laser structure is designed so that the active region extends the edges of devices.
a) True
b) False

8. Gain guided laser structure are __________
a) Chemical laser
b) Gas laser
c) DH injection laser
d) Quantum well laser

9. Laser modes are generally separated by few __________
a) Tenths of micrometer
b) Tenths of nanometer
c) Tenths of Pico-meter
d) Tenths of millimeter

10. The spectral width of emission from the single mode device is __________
a) Smaller than broadened transition line-width
b) Larger than broadened transition line-width
c) Equal the broadened transition line-width
d) Cannot be determined

11. Single longitudinal mode operation is obtained by __________
a) Eliminating all transverse mode
b) Eliminating all longitudinal modes
c) Increasing the length of cavity
d) Reducing the length of cavity

12. A correct DH structure will restrict the vertical width of waveguide region is?
a) 0.5μm.
b) 0.69 μm
c) 0.65 μm
d) Less than 0.4 μm

13. The external power efficiency of an injection laser with a GaAs is 13% having band gap energy of 1.64 eV. Determine external power efficiency.
a) 0.198
b) 0.283
c) 0.366
d) 0.467

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