McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electronics and Telecommunication Engineering [ENTC] .
| 301. |
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» C. 0.32 | |
| 302. |
A ho*mo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 303. |
How many types of hetero-junctions are available? |
| A. | two |
| B. | one |
| C. | three |
| D. | four |
| Answer» A. two | |
| 304. |
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 |
| Answer» D. gaas/alga as dh | |
| 305. |
Stimulated emission by recombination of injected carriers is encouraged in |
| A. | semiconductor injection laser |
| B. | gas laser |
| C. | chemist laser |
| D. | dye laser |
| Answer» A. semiconductor injection laser | |
| 306. |
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 |
| Answer» A. 1 nm or less | |
| 307. |
Injection laser have a high threshold current density of |
| A. | 104acm-2and more |
| B. | 102acm-2 |
| C. | 10-2acm-2 |
| D. | 10-3acm-2 |
| Answer» A. 104acm-2and more | |
| 308. |
ηT Is known as slope quantum efficiency. State true or false |
| A. | true |
| B. | false |
| Answer» B. false | |
| 309. |
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 % |
| Answer» A. 7.8 % | |
| 310. |
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 |
| Answer» B. roughening the edges of device | |
| 311. |
A particular laser structure is designed so that the active region extends the edges of devices. State whether the following statement is true or false. |
| A. | true |
| B. | false |
| Answer» A. true | |
| 312. |
Gain guided laser structure are |
| A. | chemical laser |
| B. | gas laser |
| C. | dh injection laser |
| D. | quantum well laser |
| Answer» C. dh injection laser | |
| 313. |
Laser modes are generally separated by few |
| A. | tenths of micrometer |
| B. | tenths of nanometer |
| C. | tenths of pico-meter |
| D. | tenths of millimeter |
| Answer» B. tenths of nanometer | |
| 314. |
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 |
| Answer» A. smaller than broadened transition line-width | |
| 315. |
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 |
| Answer» D. reducing the length of cavity | |
| 316. |
A correct DH structure will restrict the vertical width of waveguide region |
| A. | 0.5μm. |
| B. | 0.69 μm |
| C. | 0.65 μm |
| D. | less than 0.4 μm |
| Answer» D. less than 0.4 μm | |
| 317. |
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 |
| Answer» A. 0.198 | |
| 318. |
The strip width of injection laser is |
| A. | 12 μm |
| B. | 11.5 μm |
| C. | less than 10 μm |
| D. | 15 μm |
| Answer» C. less than 10 μm | |
| 319. |
Some refractive index variation is introduced into lateral structure of laser. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» A. true | |
| 320. |
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. |
| Answer» D. strong index guiding lasers. | |
| 321. |
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. |
| Answer» D. both transverse and lateral direction. | |
| 322. |
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 |
| Answer» B. ingaasp | |
| 323. |
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. |
| Answer» A. through regrowth of semi-insulating material. | |
| 324. |
Quantum well lasers are also known as |
| A. | bh lasers. |
| B. | dh lasers. |
| C. | chemical lasers. |
| D. | gain-guided lasers. |
| Answer» B. dh lasers. | |
| 325. |
Quantum well lasers are providing high inherent advantage over |
| A. | chemical lasers. |
| B. | gas lasers. |
| C. | conventional dh devices. |
| D. | bh device. |
| Answer» C. conventional dh devices. | |
| 326. |
Strip geometry of a device or laser is important. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» A. true | |
| 327. |
Better confinement of optical mode is obtained in |
| A. | multi quantum well lasers. |
| B. | single quantum well lasers. |
| C. | gain guided lasers. |
| D. | bh lasers. |
| Answer» A. multi quantum well lasers. | |
| 328. |
Multi-quantum devices have superior characteristics over |
| A. | bh lasers. |
| B. | dh lasers. |
| C. | gain guided lasers. |
| D. | single-quantum-well devices. |
| Answer» B. dh lasers. | |
| 329. |
Dot-in-well device is also known as |
| A. | dh lasers. |
| B. | bh lasers. |
| C. | qd lasers. |
| D. | gain guided lasers. |
| Answer» C. qd lasers. | |
| 330. |
A BH can have anything from a single electron to several electrons. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 331. |
QD lasers have a very low threshold current densities of range |
| A. | 0.5 to 5 a cm-2 |
| B. | 2 to 10 a cm-2 |
| C. | 10 to 30 a cm-2 |
| D. | 6 to 20 a cm-2 |
| Answer» D. 6 to 20 a cm-2 | |
| 332. |
__________________ may be improved through the use of frequency-selective feedback so that the cavity loss is different for various longitudinal modes. |
| A. | frequency selectivity |
| B. | longitudinal mode selectivity |
| C. | electrical feedback |
| D. | dissipated power |
| Answer» B. longitudinal mode selectivity | |
| 333. |
Device which apply the frequency-selective feedback technique to provide single longitudinal operation are referred to as ________________ |
| A. | dsm lasers |
| B. | nd: yag lasers |
| C. | glass fiber lasers |
| D. | qd lasers |
| Answer» A. dsm lasers | |
| 334. |
Which of the following does not provide single frequency operation? |
| A. | short cavity resonator |
| B. | dsm lasers |
| C. | coupled cavity resonator |
| D. | fabry-perot resonator |
| Answer» D. fabry-perot resonator | |
| 335. |
Conventional cleaved mirror structures are difficult to fabricate with the cavity lengths below |
| A. | 200μmand greater than 150 μm |
| B. | 100 μm and greater than 50 μm |
| C. | 50 μm |
| D. | 150 μm |
| Answer» C. 50 μm | |
| 336. |
In the given equation, corrugation period is given by lλb/2Ne. If λb is the Bragg wavelength, then what does ‘l’ stand for? |
| A. | length of cavity |
| B. | limitation index |
| C. | integer order of grating |
| D. | refractive index |
| Answer» C. integer order of grating | |
| 337. |
The first order grating (l=1) provide the strongest coupling within the device. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» A. true | |
| 338. |
The semiconductor lasers employing the distributed feedback mechanism are classified in _________________ categories |
| A. | one |
| B. | two |
| C. | three |
| D. | four |
| Answer» B. two | |
| 339. |
DBF-BH lasers exhibit low threshold currents in the range of ________________ |
| A. | 40 to 50 ma |
| B. | 21 to 30 ma |
| C. | 2 to 5 ma |
| D. | 10 to 20 ma |
| Answer» D. 10 to 20 ma | |
| 340. |
Fabry-Perot devices with BH geometries high modulation speeds than DFB-BH lasers. State whether the given statement is true or false |
| A. | true |
| B. | false |
| Answer» B. false | |
| 341. |
The InGaAsP/InP double channel planar DFB-BH laser with a quarter wavelength shifted first order grating provides a single frequency operation and incorporates a phase shift of ______________ |
| A. | π/2 radians |
| B. | 2π radians |
| C. | π radians |
| D. | 3π/2 radians |
| Answer» A. π/2 radians | |
| 342. |
The narrow line-width obtained under the CW operation for quarter wavelength shifted DFB laser is ________________ |
| A. | 2 mhz |
| B. | 10 mhz |
| C. | 3 mhz |
| D. | 1 mhz |
| Answer» C. 3 mhz | |
| 343. |
Line-width narrowing is achieved in DFB lasers by a strategy referred as _______________ |
| A. | noise partition |
| B. | grating |
| C. | tuning |
| D. | bragg wavelength detuning |
| Answer» D. bragg wavelength detuning | |
| 344. |
_________________ is a technique used to render the non-conducting material around the active cavity by producing permanent defects in the implanted area |
| A. | dispersion |
| B. | ion de-plantation |
| C. | ion implantation |
| D. | attenuation |
| Answer» C. ion implantation | |
| 345. |
The threshold temperature coefficient for InGaAsP devices is in the range of |
| A. | 10-40 k |
| B. | 40-75 k |
| C. | 120-190 k |
| D. | 150-190 k |
| Answer» B. 40-75 k | |
| 346. |
The process where the energy released during the recombination of an electron-hole event getting transferred to another carrier is known as |
| A. | inter-valence bond absorption |
| B. | auger recombination |
| C. | carrier leakage effects |
| D. | exothermic actions |
| Answer» B. auger recombination | |
| 347. |
Auger recombination can be reduced by using |
| A. | strained mqw structure. |
| B. | strained sqw structure. |
| C. | gain-guided strained structure. |
| D. | strained quantum dots lasers. |
| Answer» A. strained mqw structure. | |
| 348. |
High strain in strained MCQ structure should be incorporated. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 349. |
The parameter that prevents carrier from recombination is |
| A. | auger recombination |
| B. | inter-valence band absorption |
| C. | carrier leakage |
| D. | low temperature sensitivity |
| Answer» C. carrier leakage | |
| 350. |
Determine the threshold current density for an AlGaAs injection laser with T0=180k at 30°C. |
| A. | 6.24 |
| B. | 9.06 |
| C. | 3.08 |
| D. | 5.09 |
| Answer» D. 5.09 | |
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