Abstract

It is well known that waves with frequencies within the forbidden gap inside a crystal are transported only over a limited distance-the Bragg length-before being reflected by Bragg interference. Here, we demonstrate how to send waves much deeper into crystals in an exemplary study of light in two-dimensional silicon photonic crystals. By spatially shaping the wave fronts, the internal energy density-probed via the laterally scattered intensity-is enhanced at a tunable distance away from the front surface. The intensity is up to 100× enhanced compared to random wave fronts, and extends as far as 8× the Bragg length, which agrees with an extended mesoscopic model. We thus report a novel control knob for mesoscopic wave transport that pertains to any kind of waves.

Highlights

  • It is well known that waves with frequencies within the forbidden gap inside a crystal are transported only over a limited distance—the Bragg length—before being reflected by Bragg interference

  • In this Letter, we demonstrate the tunable control of wave transport in real photonic crystals

  • We report a novel control knob for mesoscopic wave transport that pertains to any kind of waves, including

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Summary

Spatially Shaping Waves to Penetrate Deep inside a Forbidden Gap

It is well known that waves with frequencies within the forbidden gap inside a crystal are transported only over a limited distance—the Bragg length—before being reflected by Bragg interference. We report a novel control knob for mesoscopic wave transport that pertains to any kind of waves. Stop gaps, emerge in the band structure as a result of interference between the incident and Bragg diffracted waves [12,13]. In disordered media without gaps spatially shaping the phases of incident waves sets interferences between the channels resulting in new control, termed wave front shaping [20,21,22]. In this Letter, we demonstrate the tunable control of wave transport in real photonic crystals.

PC Si
SLM xz
Uncontrolled Controlled
Enhancement EW
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