Dissertation Defense

Quantum Dot-Rolled-up and Edge Emitting Lasers

Sishir Bhowmick

Due to their unique optoelectronic properties, lasers incorporating quantum dots exhibit superior characteristics compared with those incorporating equivalent quantum wells and quantum dashes. The three-dimensional confinement of carriers in the quantum dots produces an atomic-like density of states which results in better temperature stability, chirp-free high speed operation, higher modulation bandwidth in the lasers and therefore makes them a favorable candidate for practical applications.
The threshold behavior of novel GaAs based InAs quantum dot rolled-up microtube lasers has been investigated. The threshold condition was derived considering the radiation, bending, and substrate losses associated with these device geometries and verified with experimental data. A microtube directional coupler sensor and a microtube phototransceiver circuit have also been demonstrated. The growth of self-organized InAs/In0.53Ga0.23Al0.24As quantum dots on InP substrates for 1.55 Â µm lasers has been achieved by limiting the anisotropic migration of In adatoms on the growth surface. Quantum dot lasers incorporating tunnel injection and modulation p-doping of the active region have been demonstrated. These lasers are characterized by high temperature stability with a characteristic temperature To ~227 K in the temperature range 5 to 45 oC and a maximum 3-dB modulation bandwidth of 14.4 GHz has also been achieved.

Sponsored by

Pallab K. Bhattacharya