Local probing of Bloch mode dispersion in a photonic crystal waveguide

Abstract

Abstract:The local dispersion relation of a photonic crystal waveguide is directly determined by phase-sensitive near-field microscopy. We readily demonstrate the propagation of Bloch waves by probing the band diagram also beyond the first Brillouin zone. Both TE and TM polarized modes were distinguished in the experimental band diagram. Only the TE polarized defect mode has a distinctive Bloch wave character. The anomalous dispersion of this defect guided mode is demonstrated by local measurements of the group velocity. The measured dispersion relation and measured group velocities are both in good agreement with theoretical calculations.

Ultrafast evolution of photonic eigenstates in k-space

“…1b, we know that the low-frequency components couple more efficiently to the lower output waveguide. Owing to anomalous dispersion 23 , these low-frequency components arrive at a later time at the directional coupler, and therefore the output appears at a later time. The error of ±20 fs has two main contributions: the error in determining the centre-of-mass of the curves and a correction for the slightly different length of the measured output waveguides.…”

Enhanced stitching for the fabrication of photonic structures by electron beam lithography

“…More direct monitoring would require a nontrivial technique such as scanning near-field optical microscopy-type measurements. 13 In order to relate this variation in the peak ratio to the scattering loss due to the stitching error and consequently obtain more directly comprehensible information than is given by the peak ratios, a numerical model was fitted to the experimental results.…”

Characterizing photonic crystal waveguides with an expanded k-space evanescent coupling technique

“…Previously, several techniques have been employed including observation of Fabry-Pérot (FP) resonances in the transmission spectrum from photonic crystal/ ridge waveguide interfaces [7], analysis of fringes from an external Mach-Zehnder interferometer [8], phase sensitive near field microscopy [9] and Fourier optics techniques [10]; although those techniques have proven their ability to retrieve the dispersion curve, they require the presence of conventional index guiding access waveguides that 1) can limit the insertion efficiency unless an elaborate and multistep manufacturing process (such as inverse tapers [3,11]) is employed, 2) can hinder the measurements due to coupling issues in the slow light regime between the photonic [12]. This technique does not require access waveguides but relies on the use of internal emitters such as quantum wells or quantum dots, making it incompatible with passive structures.…”