A cleaved-facet, DH GaAs laser has an active layer thickness of 0.1 μm, a length of 300μm, and a threshold current density of 1 kA/cm2. Assume unity injection efficiency, an internal loss of 10cm−1, a confinement factor of 0.1, and only radiative recombination. (a) What is the threshold carrier density in the active region? (b) What is the power out of one cleaved facet per micrometer of width at a current density of 2 kA/cm2?(c) What are the photon and carrier densities at 2 kA/cm2?

A planar optical waveguide of length = 5 cm is fabricated in an epitaxial layer of GaAs that has an n-type doping concentration of 1×10¹8/cm³. (a) What is ratio to the input power of the total power lost over the length of the waveguide that results from free-carrier absorption? (b) What is the answer to part (a) if the doping concentration is reduced to 1x10¹6/cm³?

We have a piece of Si (shown below) with dimensions 50 um x 200 um x 0.25 um. The Silicon is doped uniformly with ND = 1014 cm3. What is the resistance of the slab when measured along the length (200 um)? %3| If a light with photonic energy greater than the bandgap of Si were to be shone from the top surface such that it produces uniform hole-electron pairs Ap =An = 5E12 cm-3 throughout the slab, what would be the ratio of the illuminated conductivity vs the dark conductivity? What is the ratio of conductivity due to holes vs the conductivity due to electrons under illumination? How about in the dark? 200 Nm

Consider a 100 Ǻ GaAs/AlGaAs quantum well where the electron effective mass is 0.067 m0. There are 2 x 1012 electron/cm2 in the well. At low temperatures, calculate the magnetic field at which the Fermi level just enters the third Landau level of the ground state sub-band.