Q. The lower energy level contains more atoms than upper level under the conditions of ________________

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Q. __________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.

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Q. A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes.

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Q. A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.

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Q. Doppler broadening is a homogeneous broadening mechanism.

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Q. An injection laser has active cavity losses of 25 cm⁻¹ and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500 μm.

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Q. Longitudinal modes contribute only a single spot of light to the laser output.

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Q. Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser. (Frequency separation = 2 GHz, Wavelength = 0.5 μm)

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Q. A perfect semiconductor crystal containing no impurities or lattice defects is called as __________

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Q. The energy-level occupation for a semiconductor in thermal equilibrium is described by the __________

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Q. What is done to create an extrinsic semiconductor?

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Q. The majority of the carriers in a p-type semiconductor are __________

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Q. _________________ is used when the optical emission results from the application of electric field.

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Q. In the given equation, what does p stands for?

p = 2πhk

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Q. The recombination in indirect band-gap semiconductors is slow.

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Q. Calculate the radioactive minority carrier lifetime in gallium arsenide when the minority carriers are electrons injected into a p-type semiconductor region which has a hole concentration of 10¹⁸ cm⁻³. The recombination coefficient for gallium arsenide is 7.21*10⁻¹⁰ cm³s⁻¹.

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Q. Which impurity is added to gallium phosphide to make it an efficient light emitter?

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Q. Population inversion is obtained at a p-n junction by __________

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Q. A GaAs injection laser has a threshold current density of 2.5*10³ Acm⁻² and length and width of the cavity is 240 μm and 110 μm respectively. Find the threshold current for the device.

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Q. 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.

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