Band-edge-induced Bragg diffraction in two-dimensional photonic crystals

Abstract

Two-dimensional photonic crystals composed of two orthogonal volume diffraction gratings have been photogenerated in photopolymers. When the read beam is set at the Bragg angle, the diffraction efficiency of the transmission grating is strongly enhanced at the band edge of the reflection grating recorded in the material. Such a device provides Bragg operation and enhancement of the diffraction efficiency of the thin diffraction grating together with good wavelength selectivity. Such advantages could be interesting for optical signal processing.

Selective grating obtained by dye microstructuration based on local photobleaching using a laser writer

“…We have periodically insolated dye on silver showing many patterning possibilities for wavelength selective grating fabrication. This work thus highlights the high potential of the localphoto-bleaching method for obtaining many kind of micro-structured geometries in organic emitters, and could be applied for different applications like strong coupling studies [6,7,19,26] or wavelength selective grating [11][12][13][14][15]17].…”

“…To validate the efficiency of our method, we propose to apply this concept to the fabrication of wavelength selective gratings of different shapes and periods. This easy processing technique could be a convenient alternative to the previously described methods [11][12][13][14][15] for selective wavelength grating fabrication, such as multiple interference [11][12][13], cholesteric liquid crystal [14,15] or plasmonic system [16,17].…”

Bragg diffraction in thin 2D refractive index modulated semiconductor samples

“…The thickness is also an issue as it must not be too large if an integrated device is wanted, although the diffraction regime associated with thin crystals is a Raman-Nath regime involving multiple diffracted beams. Besides the already wellknown simple [2][3][4] and double resonance [5][6][7][8][9] in a Fabry-Perot cavity, a new approach using slow light at the band edge of a one-dimensional photonic crystal (1D-PC) was recently demonstrated to overcome these difficulties, first in photopolymers [10] and then in semiconductor Bragg reflectors [11]. Results are especially attractive in the latter case due to the high index contrast of Bragg reflectors.…”

Efficient Bragg diffraction in thin semiconductor two-dimensional gratings

“…Such a drawback was circumvented by placing the holographic material in an asymmetric cavity [6][7][8], and the Bragg operation of the device was obtained, even with a thin recording material [9,10]. Recently, another solution using two-dimensional (2D) photonic crystals was proposed and demonstrated in photopolymers [11]. However, due to the low refractive index contrast ͑⌬n = 0.045͒ that could be reached in such materials, the device performances remained limited.…”

“…As explained in detail in [11], the technique of band-edge-induced Bragg diffraction in 2D gratings is based on the enhancement of light intensity at the band edge wavelength of the one-dimensional (1D) refractive index modulation along the mean propagation direction Ẑ of the read and diffracted beams. Indeed, for a transmission grating with a refractive index modulation perpendicular to the Ẑ direction, very strong enhancement of the diffraction efficiency is predicted if the read beam propagation direction is set at Bragg incidence on this transmission grating while its wavelength is at the band edge resonance of the one-dimensional photonic crystal (1D-PC).…”