Abstract
We report the first demonstration of a solution processable, optically switchable 1D photonic crystal which incorporates phototunable doped metal oxide nanocrystals. The resulting device structure shows a dual optical response with the photonic bandgap covering the visible spectral range and the plasmon resonance of the doped metal oxide the near infrared. By means of a facile photodoping process, we tuned the plasmonic response and switched effectively the optical properties of the photonic crystal, translating the effect from the near infrared to the visible. The ultrafast bandgap pumping induces a signal change in the region of the photonic stopband, with recovery times of several picoseconds, providing a step toward the ultrafast optical switching. Optical modeling uncovers the importance of a complete modeling of the variations of the dielectric function of the photodoped material, including the high frequency region of the Drude response which is responsible for the strong switching in the visible after photodoping. Our device configuration offers unprecedented tunability due to flexibility in device design, covering a wavelength range from the visible to the near infrared. Our findings indicate a new protocol to modify the optical response of photonic devices by optical triggers only.
Highlights
Solution processed photonic crystals offer the option of easy device fabrication on various substrates, with the additional benefit of introducing materials with diverse and complementary features
The tail from about 1500 nm towards longer wavelengths instead arises from the plasmonic response of the indium tin oxide (ITO) nanoparticles, brought about by the free carrier density N in the range of 1020–1021 cm−316,26–28
We modeled the optical response of the photonic crystal by implementing two different models that account for the respective spectral contributions: firstly, we implemented the transfer matrix theory, which takes into account the alternating refractive index of the periodic structure, and secondly we integrated the Drude model and the Maxwell-Garnet effective medium approximation (MG-EMA) to consider the contribution of the ITO nanoparticle films to the dielectric response of the photonic crystal[29,30,31]
Summary
Solution processed photonic crystals offer the option of easy device fabrication on various substrates, with the additional benefit of introducing materials with diverse and complementary features. Heavily doped semiconductor nanoparticles that show plasmonic response in the near infrared (NIR) have attracted the interest of the scientific community Such materials are very sensitive to changes in dielectric function induced by variations in their carrier density through doping control[4,5,6,7,8]. In this work we study, for the first time, such plasmonic/photonic effect in a photonic crystal composed of alternating nanoparticle layers of SiO2 and indium tin oxide (ITO) The latter is a very prominent heavily doped semiconductor with carrier densities in the range of 1021 cm−3 in which the reversible tunability of its NIR plasmonic response by various means has been demonstrated[16,26,27,28]. We demonstrate the switching of its optical response via photodoping in steady state and on ultrafast time scales, together taking a step towards a solution processed, contactless, all-optical switching device
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