Publications by authors named "Seita Iwahashi"

Three-dimensional coupled-wave theory is extended to model triangular-lattice photonic-crystal surface-emitting lasers with transverse-electric polarization. A generalized coupled-wave equation is derived to describe the sixfold symmetry of the eigenmodes in a triangular lattice. The extended theory includes the effects of both surface radiation and in-plane losses in a finite-size laser structure.

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We develop a coupled-wave model that is capable of treating finite-size square-lattice photonic crystal surface emitting lasers with transverse-electric polarization. Various properties of interest including threshold gain, mode frequency, field intensity envelope within the device, far-field pattern, as well as polarization and divergence angle of the output beam for the band-edge modes are calculated. Theoretical predictions of the lowest threshold mode and the output beam profile are in good agreement with our experimental findings.

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Article Synopsis
  • - The extended coupled-wave theory (CWT) provides a fast and effective way to analyze the radiative characteristics of two-dimensional photonic-crystal surface-emitting lasers (PC-SELs) with complex sidewall geometries.
  • - The study focuses on the interaction of light in different air-hole shapes and the effects of tapered and tilted sidewalls, finding that in-plane asymmetries can significantly enhance laser output power through constructive interference.
  • - The research aligns CWT results with finite-difference time-domain (FDTD) simulations and suggests using a top-down reactive ion etching (RIE) method for creating these optimized photonic structures.
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We have successfully generated vector beams with higher-order polarization states using photonic-crystal lasers. We have analyzed and designed lattice structures that provide cavity modes with different symmetries. Fabricated devices based on these lattice structures produced doughnut-shaped vector beams, with symmetries corresponding to the cavity modes.

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