Gaas laser (a) the degenerate occupation of the conduction and valence bands with electrons and holes to maintain the laser requirement that emission must overcome absorption. explain how the degeneracy prevents band-to-band absorption at the emission wavelength of 867 nm (b) assuming equal electron and hole concentrations, and same effective masses for electrons and holes, calculate the minimum carrier concentration n -p for population inversion in gaas at 300 k. the intrinsic carrier concentration at 300 k in gaas is 1x106 cm3, the gap energy is 1.43 ev.

Aspring has a relaxed length of 33 cm (0.33 m) and its spring stiffness is 6 n/m. you glue a 76 gram block (0.076 kg) to the top of the spring, and push the block down, compressing the spring so its total length is 15 cm. you make sure the block is at rest, then at time t=0 you quickly move your hand away. the block begins to move upward, because the upward force on the block by the spring is greater than the downward force on the block by the earth. calculate y vs. time for the block during a 0.09-second interval after you release the block, by applying the momentum principle in three steps each of 0.03-second duration.