Q. Determine the total carrier recombination lifetime of a double heterojunction LED where the radioactive and nonradioactive recombination lifetime of minority carriers in active region are 70 ns and 100 ns respectively.

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Q. Determine the internal quantum efficiency generated within a device when it has a radiative recombination lifetime of 80 ns and total carrier recombination lifetime of 40 ns.

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Q. Compute power internally generated within a double-heterojunction LED if it has internal quantum efficiency of 64.5 % and drive current of 40 mA with a peak emission wavelength of 0.82 μm.

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Q. The Lambertian intensity distribution __________ the external power efficiency by some percent.

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Q. A planar LED fabricated from GaAs has a refractive index of 2.5. Compute the optical power emitted when transmission factor is 0.68.

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Q. A planar LED is fabricated from GaAs is having a optical power emitted is 0.018% of optical power generated internally which is 0.018% of optical power generated internally which is 0.6 P. Determine external power efficiency.

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Q. For a GaAs LED, the coupling efficiency is 0.05. Compute the optical loss in decibels.

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Q. In a GaAs LED, compute the loss relative to internally generated optical power in the fiber when there is small air gap between LED and fiber core. (Fiber coupled = 5.5 * 10⁻⁴ Pint)

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Q. Determine coupling efficiency into the fiber when GaAs LED is in close proximity to fiber core having numerical aperture of 0.3.

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Q. If a particular optical power is coupled from an incoherent LED into a low-NA fiber, the device must exhibit very high radiance.

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Q. The amount of radiance in planer type of LED structures is ____________

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Q. In optical fiber communication _____________ major types of LED structures are used.

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Q. As compared to planar LED structure, Dome LEDs have ______________ External power efficiency ___________ effective emission area and _____________ radiance.

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Q. The techniques by Burros and Dawson in reference to homo structure device is to use an etched well in GaAs structure.

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Q. In surface emitter LEDs, more advantage can be obtained by using ____________

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Q. Internal absorption in DH surface emitter Burros type LEDs is ____________

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Q. DH surface emitter generally give ____________

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Q. A DH surface emitter LED has an emission area diameter of 60 μm. Determine emission area of source.

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Q. Estimate optical power coupled into fiber of DH SLED having emission area of 1.96*10⁻⁵, radiance of 40 W/rcm², numerical aperture of 0.2 and Fresnel reflection coefficient of 0.03 at index matched fiber surface.

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Q. In a multimode fiber, much of light coupled in the fiber from an LED is ____________

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