The photonics bandgap cavities are studied theoretically and experimentally. Cavity analysis by finite element method is formulated with anisotropic perfectly matched layer boundary condition. And the method to calculate spontaneous emission rate in general micro-cavities is proposed. The two-dimensional slab photonics bandgap lasers are demonstrated at room-temperature.
The finite element approach far the eigenmode analysis of the photonic bandgap cavity is presented using an anisotropic perfectly matched layer absorbing boundary condition. This method calculates rigorously the resonant frequency, the field pattern and the quality factor of the resonant mode of the finite-sized cavity in free space. The validity of the approach is examined through its application to two dimensional photonic bandgap cavities. Numerical error analyses for the resonant frequencies and the quality ftctors of the cavities demonstrate the accuracy and reliability of our approach which used non-uniform grids, higher-order elements and the perffctly matched layer. Far-field patterns of the resonant modes are obtained by simple transformation. Since the perfectly matched layer can represent the real boundary condition very well, cavities of any size and shape can be analyzed with desired accuracy.
A simple method to obtain the spontaneous emission rate of a dipole placed in a general micro-cavity is proposed and demonstrated. In our approach, Maxwell's equations are solved directly in real space instead of k-space by the finite-difference time-domain method with a free space boundary condition. It is advantageous that allowed eigenmodes need not to be calculated and the total radiation rates to all the allowed modes are obtained from the first. All the localized modes, guided modes and extended modes are inherently included in this ffrmulation. The validity of method is tested for a dipole placed in idea planar micro-cavity and the calculated results agree well with the closed-form analytic solutions. The enhancement and the inhibition of the spontaneous emission rate in several photonic band gap structures are studied. Point dipole analyses show three-dimensional efffcts in two-dimensional in-plane photonic band gaps and of effects of loealized, guided and extended modes on radiation rates.
Thermally- and mechanically-dependable two-dimensional photonic bandgap lasers are propesed and realized at room temperature. The thin slab photonic bandgap laser strueture is sandwiched between air and a drilled aluminum oxide layer provided by wafer fusion techniques. In this thin slab structure, the optical confinement of photons is achieved by two-dimensional triangular photonic lattice in horizontal planeand total internal reflection in vertical direction. For small cavities pulsed lasingactign is observed at 1.54μm by optical pumping with duty cycle up to 30%. For large cavities, continuous operation is realized at room temperature. The incident threshold pump power at 0,98μm is 9.2mW for a 21-defect cavity lasing at λ=1.6μm. Polarization characteristics and laser mode of two-dimensional photonic bandgap defect modes are also studied below and above the lasing threshold.
Lasing action from two-dimensional distributed feedback(DFB) is reported. Compared to conventional DFB lasers, it incororates the modified densiy of states of electromagnetic modes near the bandedge. In this structure, the enhanced spontaneous emission rate to desired laser mode with the reduced spontaneous emission rate to other modes makes low threshold lasing possible. The incident threshold pump power at 0.95μm is 1mW lasing at λ=1.53μm.
