Model calculations for enhanced fluorescence in photonic crystal phosphor

Abstract

We propose a novel photonic structure, based on the photonic crystal (PC) effect, which simulations show results in an improved fluorescence efficiency from embedded phosphor. To be specific, the phosphor pumping efficiency can be significantly improved by tuning the pump photon energy to a photonic band-edge (PBE) of the PC phosphor. We have confirmed this theoretically by calculating optical properties of one-dimensional PC phosphor structures using the transfer-matrix method and plane-wave expansion method. For a particular model structure based on a quantum dot phosphor, the fluorescence enhancement factor was estimated to be as high as 6.9 for a monochromatic pump source and 2.2 for a broad bandwidth (20 nm) pump source.

25th Anniversary Article: Ordered Polymer Structures for the Engineering of Photons and Phonons

“…(d) Reflectance spectrum of a 1D PhC comprised of 30 unit cells showing the electric field intensity profiles for four selected wavelengths within and outside the PBG. Reproduced with permission . Copyright 2012, Optical Society of America.…”

2D Square Lattice Photonic Crystal Phosphor Films for Efficient and Excitation Polarization Insensitive Color Conversion

“…Mainstream phosphor development—to improve color conversion efficiency or to tune absorption/emission bands—has so far been predominantly materials‐oriented . Quite recently, the authors' group proposed and demonstrated a paradigm‐shifting concept in phosphor research, called photonic crystal (PhC) phosphors . The basic idea behind PhC phosphors is to structurally engineer phosphor materials into periodic PhCs—with the associated photonic band‐edge (PBE) modes tuned to the phosphor excitation wavelength—to induce an enhancement in phosphor excitation efficiency (and therefore color conversion efficiency).…”

“…The basic idea behind PhC phosphors is to structurally engineer phosphor materials into periodic PhCs—with the associated photonic band‐edge (PBE) modes tuned to the phosphor excitation wavelength—to induce an enhancement in phosphor excitation efficiency (and therefore color conversion efficiency). To demonstrate the viability and applicability of the technology, we stacked two batches of the PhC phosphor films emitting in red and green on top of a blue LED chip to efficiently and economically produce high‐quality white light 4d…”

“…The PhC phosphors employed in the previous conceptual demonstrations comprised simple 1D PhC film structures, in which parallel grating lines were arranged periodically in the lateral plane 4c,d. Consequently, their response to vertically impinging excitation photons is inevitably polarization‐sensitive, thereby limiting their overall efficiency when used with unpolarized excitation sources.…”

“…Our design strategy is to make the 2D PhC PBE modes at the zone center (Γ‐point) match the excitation photon energy to induce an enhanced interaction between the excitation photons and CQDs. The use of Γ‐point PBEs (among various PBEs available), where the lateral momentum ( k ∥ ) and group velocity (∇ k ω) of photons are zero, is critically important because they enable the PhC structure to resonate with the excitation photons that are incident in the direction normal to the phosphor film plane 4c. In addition to the utilization of 2D PhC patterns (instead of 1D PhC), we intentionally increased the thickness of the silicon nitride backbone layer (to a nominal thickness of 110 nm) to make it substantially thicker than those in our previous versions (90 nm), so that the structure can support not only the transverse‐electric (TE) but also the transverse‐magnetic (TM) fundamental waveguide modes.…”