Simulation of Spontaneous Emission in FDTD and Realization of Monolithically Integrated Narrow Linewidth Super Compact Grating Laser

The simulation of spontaneous emission, noise and laser linewidth in finite-difference time- domain (FDTD) method is of great importance for the modeling and simulation of active photonic devices like lasers and amplifiers. We report a general computational model of spontaneous emission noise of atomic media based on multi-level multi-electron system with induced fluctuation of atomic dipoles using FDTD method. Quantum derivations of rate equations are present. To apply the model in classical simulation, certain classical assumptions were required and the quantum operator equations were transformed into classical complex number equations. Energy conservation condition was used to derive the noise correlation. Noise terms were realized with classical random number generators. The modification to the model required for applying to 2D geometry are also proposed. Unlike the stimulated emission light which is coherent, the spontaneous emission light is not coherent and care needs to be taken when adding up the light coming from different sources. The model was implemented in our Multi-level Multi-Electron FDTD (MLME-FDTD) model. Total spontaneous emission power by one atom was examined in simulation to be equal to one photon. Laser linewidth of a micro-ring semiconductor laser was successfully simulated directly using FDTD for the first time to our knowledge. The linewidth obtained agreed with that estimated analytically.;We also realized a novel monolithically integrated "external cavity" semiconductor laser with curved Echelle Rowland Grating capable of narrow spectral linewidth, high output power, low relative intensity noise and emission at 1550nm wavelength range. By monolithically integrating Super-compact Curved Grating (SCG) with very high wavelength resolution, single-frequency operation with side mode suppression ratio (SMSR) much higher than DFB/DBR approaches can possibly be achieved, and integrated "external cavity" is much less susceptible to vibration noise and temperature fluctuation than usual external-cavity semiconductor laser approaches.;The super-compact monolithically integrated grating lasers were fabricated and tested. The lasers were tested to be single-frequency lasing and the laser linewidth was measured to be around 300kHz at output power level of 0.25mW, which is significantly lower than usual DFB laser diodes.