All-optical octave-broad ultrafast switching of Si woodpile photonic band gap crystals

Abstract

We present ultrafast all-optical switching measurements of Si woodpile photonic band gap crystals. The crystals are spatially homogeneously excited and probed by measuring reflectivity over an octave in frequency ͑including the telecommunication range͒ as a function of time. After 300 fs, the complete stop band has shifted to higher frequencies as a result of optically excited free carriers. The switched state relaxes quickly with a time constant of 18 ps. We present a quantitative analysis of switched spectra with theory for finite photonic crystals. The induced changes in refractive index are well described by a Drude model with a carrier relaxation time of 10 fs. We briefly discuss possible applications of high-repetition-rate switching of photonic crystal cavities.

Kerr and free carrier ultrafast all-optical switching of GaAs/AlAs nanostructures near the three photon edge of GaAs

“…To shift the cavity resonance by one linewidth the refractive index change should be equal to ͑⌬nЈ / nЈ͒ = ͑1 / Q͒. 10 Thus for an experiment with a cavity having a quality factor Q of 1000, this means a refractive index change of 0.1%. It is widely assumed ͑see Ref.…”

“…2 Switching the directional properties of photonic crystals also leads to fast changes in the reflectivity, where interesting changes have been reported for Bragg stacks, 3,4 two-dimensional photonic crystals, [5][6][7] first-order stop bands of three-dimensional ͑3D͒ opaline crystals, 8,9 and 3D photonic bandgap crystals. 10,11 Ultrafast control of the propagation of light is essential to applications in active photonic integrated circuits. 12 Different mechanisms are possible for switching photonic structures.…”

Cavity quantum electrodynamics with three-dimensional photonic band gap crystals

“…Measured spectra indicate stop gaps with a transmission reduced to 15% at that wavelength. While no convincing evidence for a bandgap was presented and the structures seem to have a significant misalignment between consecutive layers, kudos are in order for this pioneering work, considering that a broad stopgap with a high reflectivity has been observed [89].…”

“…Fast dynamics was observed -500 fs up and 21 ps down -implying that switching could potentially be repeated at GHz rates. Ultrafast switching has also been performed on Si woodpile crystals that were probed by reflectivity over an octave in frequency including the telecom range [89]. Only 300 fs after the switching pulse, the complete band gap shifted to higher frequencies before quickly relaxing within 18 ps.…”

Spontaneous emission of near-infrared quantum dots controlled with photonic crystals

“…The excitation intensity ix corresponds to approximately 8 GWcm −2 . This is only about one to two orders of magnitude smaller than the pump intensities used in optical switching experiments with non-linear, two photon absorption [169,170]. The broad and constant width of the emission spectrum is ix using Φ(0) from Equation B.10 times the pulse power, i.e., the energy per pulse divided by the pulse duration.…”