Quality Factor Photonic Crystal Microcavities Research Articles

High-Q microcavities in low-index one-dimensional photonic crystal slabs based on modal gap confinement

Recently, various high quality factor photonic crystal microcavities have been demonstrated theoretically and experimentally with only one-dimensional periodicity. However, in most cases high-index materials such as silicon were chosen for easily achievable large photonic bandgap and elaborate refractive index modulation or taper structure is required for reducing radiation loss. Here, we present a design of high-Q microcavities in one-dimensional multilayer polystyrene photonic crystal slab structures with a low-index contrast of 1.59:1. Microcavities are introduced by simply decreasing the thickness of layers at the center region to form a double-heterostructure. A resonant mode with a quality factor up to 20 000 is obtained and found to originate from the modal gap confinement by comparing with a Fabry–Perot cavity. The dependence of the maximal quality factor on the cavity length further reveals that the small group velocity of light within the heterostructure cavity contributes significantly to the high-Q. In terms of the high quality factor, ease of fabrication, and large Kerr nonlinearity of polystyrene, our double-heterostructure microcavities will find potential application in realizing all-optical modulation devices.

Fabrication of high quality factor photonic crystal microcavities in InAsP∕InP membranes combining reactive ion beam etching and reactive ion etching

The process of fabrication of high quality factor photonic crystal microcavities in slabs of InP with light emission at 1.5μm is reported. The process includes e-beam lithography, reactive ion beam etching with a CHF3∕N2 gas mixture, and reactive ion etching with a CH4∕H2 gas mixture and O2 cycling. An InGaAs sacrificial layer is removed by chemical wet etching in order to obtain the photonic crystal membrane. Microphotoluminescense measurements have been performed to assess the quality of the fabricated structures. Quality factors up to ≃30000 and laser emission with thresholds of excitation pump power around 34μW have been obtained.

High Quality Factor Photonic Crystal Micro-Cavity Design to Utilize Semiconductor Nonlinearities

Photonic crystal based microcavity structure with high quality factor (Q) and small mode volume is designed to make use of the semiconductor nonlinearities. Two and three-dimensional finite difference time domain calculations are performed, to study the dependence of Q on the defect size and shape and the position, shape and size of the nearest neighbor holes, to obtain the optimum structures. Structures are optimized to utilize semiconductor materials in the defect region to realize solid-state devices. The effect of nonlinearity in controlling the Q-factor is also reported.

Temporal behaviour of field in high quality factor photonic crystal microcavity structure

Temporal behaviour of incident pulse in high-quality (Q) factor photonic crystal microcavities are studied by two dimensional finite difference time domain calculations. For high-Q mode excitation, two periods of oscillation are observed in addition to the exponential decay corresponding to the cavity mode photon life time. Long and short period oscillations correspond to beats with low-Q mode (for short pulse widths) and to lattice periodicity for all pulse widths, respectively. For low-Q mode and off-resonant excitations, long period oscillations correspond to coupling to bandedge states.

Experimental demonstration of a high quality factor photonic crystal microcavity

Subthreshold measurements of a photonic crystal (PC) microcavity laser operating at 1.3 μm show a linewidth of 0.10 nm, corresponding to a quality factor (Q)∼1.3×104. The PC microcavity mode is a donor-type mode in a graded square lattice of air holes, with a theoretical Q∼105 and mode volume Veff∼0.25 cubic half-wavelengths in air. Devices are fabricated in an InAsP/InGaAsP multi-quantum-well membrane and are optically pumped at 830 nm. External peak pump power laser thresholds as low as 100 μW are also observed.