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.&#10;A)0.61&#10;B)0.12&#10;C)0.32&#10;D)0.48

Accepted Answer

The reflectivity R at normal incidence is given by the formula R = ((n1 - n2) / (n1 + n2))^2, where n1 is the refractive index of GaAs (3.6) and n2 is the refractive index of air (approximately 1). Substituting these values, R = ((3.6 - 1) / (3.6 + 1))^2 = (2.6 / 4.6)^2 ≈ 0.32.

Question 2

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

Accepted Answer

A homo-junction is an interface between two regions of a single-crystal semiconductor that have the same band-gap energy but are doped differently, not between semiconductors with different band-gap energies.

Question 3

How many types of hetero-junctions are available?&#10;A)two&#10;B)one&#10;C)three&#10;D)four

Accepted Answer

There are two types of heterojunctions: isotype (n-n or p-p) and anisotype (n-p or p-n), based on the semiconductor materials' doping types involved in the junction.

Question 4

The ______________ system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region.&#10;A)inp&#10;B)gasb&#10;C)gaas/gasb&#10;D)gaas/alga as dh

Accepted Answer

The GaAs/AlGaAs (Gallium Arsenide/Aluminum Gallium Arsenide) system is best developed for fabricating both lasers and LEDs, especially for shorter wavelength applications. This material system allows for efficient light emission in the visible to infrared spectrum and is widely used in optoelectronics.

Question 5

Stimulated emission by recombination of injected carriers is encouraged in&#10;A)semiconductor injection laser&#10;B)gas laser&#10;C)chemist laser&#10;D)dye laser

Accepted Answer

Stimulated emission by recombination of injected carriers is a fundamental principle in semiconductor injection lasers. In these devices, electrical current is injected into the semiconductor material, creating a population inversion that leads to stimulated emission of light. This is different from the mechanisms in gas, dye, and chemist (which is not a standard term for a laser type) lasers, where the processes involve different methods of exciting the laser medium.

Question 6

In semiconductor injection laser, narrow line bandwidth is of the order&#10;A)1 nm or less&#10;B)4 nm&#10;C)5 nm&#10;D)3 nm

Accepted Answer

In semiconductor injection lasers, the narrow line bandwidth is typically of the order of 1 nm or less, due to the very specific energy levels at which electrons and holes recombine to emit photons.

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

Accepted Answer

Injection lasers typically have a high threshold current density of 10^4 acm^-2 and more, which is necessary to achieve the population inversion required for laser action.

Question 8

?T&#160;Is known as slope quantum efficiency. State true or false

Accepted Answer

η (eta) is often used to represent quantum efficiency, not T. Quantum efficiency refers to the effectiveness of a device in converting photons into electrons, not slope.

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.&#10;A)7.8 %&#10;B)10 %&#10;C)12 %&#10;D)6 %

Accepted Answer

The external power efficiency, also known as the wall-plug efficiency, can be calculated using the formula: $\eta_{external} = \frac{\eta_{total} \times E_g}{eV}$, where $\eta_{total}$ is the total efficiency (12%), $E_g$ is the band gap energy (2.34 eV), $e$ is the charge of an electron (approximately 1.6 x 10^-19 C but not needed directly since we're working in eV), and $V$ is the applied voltage (3.6 V). Plugging the values in, we get: $\eta_{external} = \frac{12\% \times 2.34}{3.6} = 7.8\%$.

Question 10

In a DH laser, the sides of cavity are formed by _______________&#10;A)cutting the edges of device&#10;B)roughening the edges of device&#10;C)softening the edges of device&#10;D)covering the sides with ceramics

Accepted Answer

The answer of In a DH laser, the sides of...

Question 11

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

Accepted Answer

The answer of A particular laser structure is designed so...

Question 12

Gain guided laser structure are&#10;A)chemical laser&#10;B)gas laser&#10;C)dh injection laser&#10;D)quantum well laser

Accepted Answer

The answer of Gain guided laser structure are&#10;A)chemical laser&#10;B)gas laser&#10;C)dh...

Question 13

Laser modes are generally separated by few&#10;A)tenths of micrometer&#10;B)tenths of nanometer&#10;C)tenths of pico-meter&#10;D)tenths of millimeter

Accepted Answer

The answer of Laser modes are generally separated by few&#10;A)tenths...

Question 14

The spectral width of emission from the single mode device is&#10;A)smaller than broadened transition line-width&#10;B)larger than broadened transition line-width&#10;C)equal the broadened transition line-width&#10;D)cannot be determined

Accepted Answer

The answer of The spectral width of emission from the...

Question 15

Single longitudinal mode operation is obtained by&#10;A)eliminating all transverse mode&#10;B)eliminating all longitudinal modes&#10;C)increasing the length of cavity&#10;D)reducing the length of cavity

Accepted Answer

The answer of Single longitudinal mode operation is obtained by&#10;A)eliminating...

Question 16

A correct DH structure will restrict the vertical width of waveguide region&#10;A)0.5?m.&#10;B)0.69 ?m&#10;C)0.65 ?m&#10;D)less than 0.4 ?m

Accepted Answer

The answer of A correct DH structure will restrict the...

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&#10;A)0.198&#10;B)0.283&#10;C)0.366&#10;D)0.467

Accepted Answer

The answer of The external power efficiency of an injection...

Question 18

The strip width of injection laser is&#10;A)12 ?m&#10;B)11.5 ?m&#10;C)less than 10 ?m&#10;D)15 ?m

Accepted Answer

The answer of The strip width of injection laser is&#10;A)12...

Question 19

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

Accepted Answer

The answer of Some refractive index variation is introduced into...

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.&#10;A)gas lasers.&#10;B)gain guided lasers.&#10;C)weak index guiding lasers.&#10;D)strong index guiding lasers.

Accepted Answer

The answer of Buried hetero-junction (BH) device is a type...

Question 21

In Buried hetero-junction (BH) lasers, the optical field is confined within&#10;A)transverse direction.&#10;B)lateral direction.&#10;C)outside the strip.&#10;D)both transverse and lateral direction.

Accepted Answer

The answer of In Buried hetero-junction (BH) lasers, the optical...

Question 22

A double-channel planar buried hetero-structure (DCP BH) has a planar active region, the confinement material is&#10;A)alga as&#10;B)ingaasp&#10;C)gaas&#10;D)sio2

Accepted Answer

The answer of A double-channel planar buried hetero-structure (DCP BH)...

Question 23

Problems resulting from parasitic capacitances can be overcome&#10;A)through regrowth of semi-insulating material.&#10;B)by using oxide material.&#10;C)by using a planar ingaasp active region.&#10;D)by using a algaas active region.

Accepted Answer

The answer of Problems resulting from parasitic capacitances can be...

Question 24

Quantum well lasers are also known as&#10;A)bh lasers.&#10;B)dh lasers.&#10;C)chemical lasers.&#10;D)gain-guided lasers.

Accepted Answer

The answer of Quantum well lasers are also known as&#10;A)bh...

Question 25

Quantum well lasers are providing high inherent advantage over&#10;A)chemical lasers.&#10;B)gas lasers.&#10;C)conventional dh devices.&#10;D)bh device.

Accepted Answer

The answer of Quantum well lasers are providing high inherent...

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