Deck 13: Semiconductor Laser Technologies: Refractive Index, Junctions, Efficiency, and Structures

Question 1

A GaAs injection laser with an optical cavity has refractive index of 3.6. Calculate the reflectivity for normal incidence of the plane wave on the GaAs-air interface.

A)0.61
B)0.12
C)0.32
D)0.48

Answer 1

0.32

Question 2

A homo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies.

Answer 2

False

Question 3

How many types of hetero-junctions are available?

A)two
B)one
C)three
D)four

Answer 3

two

Question 4

The ______________ system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region.

A)inp
B)gasb
C)gaas/gasb
D)gaas/alga as dh

Question 5

Stimulated emission by recombination of injected carriers is encouraged in

A)semiconductor injection laser
B)gas laser
C)chemist laser
D)dye laser

Question 6

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

Question 7

Injection laser have a high threshold current density of

A)10⁴acm^?2and more
B)10²acm^?2
C)10^-2acm^?2
D)10^-3acm^?2

Question 8

?T Is known as slope quantum efficiency. State true or false

Question 9

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 %

Question 10

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

Question 11

A particular laser structure is designed so that the active region extends the edges of devices.

Question 12

Gain guided laser structure are

A)chemical laser
B)gas laser
C)dh injection laser
D)quantum well laser

Question 13

Laser modes are generally separated by few

A)tenths of micrometer
B)tenths of nanometer
C)tenths of pico-meter
D)tenths of millimeter

Question 14

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

Question 15

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

Question 16

A correct DH structure will restrict the vertical width of waveguide region

A)0.5?m.
B)0.69 ?m
C)0.65 ?m
D)less than 0.4 ?m

Question 17

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

Question 18

The strip width of injection laser is

A)12 ?m
B)11.5 ?m
C)less than 10 ?m
D)15 ?m

Question 19

Some refractive index variation is introduced into lateral structure of laser.

Question 20

Buried hetero-junction (BH) device is a type of _____________ laser where the active volume is buried in a material of wider band-gap and lower refractive index.

A)gas lasers.
B)gain guided lasers.
C)weak index guiding lasers.
D)strong index guiding lasers.

Question 21

In Buried hetero-junction (BH) lasers, the optical field is confined within

A)transverse direction.
B)lateral direction.
C)outside the strip.
D)both transverse and lateral direction.

Question 22

A double-channel planar buried hetero-structure (DCP BH) has a planar active region, the confinement material is

A)alga as
B)ingaasp
C)gaas
D)sio2

Question 23

Problems resulting from parasitic capacitances can be overcome

A)through regrowth of semi-insulating material.
B)by using oxide material.
C)by using a planar ingaasp active region.
D)by using a algaas active region.

Question 24

Quantum well lasers are also known as

A)bh lasers.
B)dh lasers.
C)chemical lasers.
D)gain-guided lasers.

Question 25

Quantum well lasers are providing high inherent advantage over

A)chemical lasers.
B)gas lasers.
C)conventional dh devices.
D)bh device.