Quasi-2D perovskites have gained significant attention in the field of optics and photonics recently due to their intriguing optical properties. Endowed with optical properties typically found in both 2D and 3D systems, they offer a premier platform for tunable optical devices. Here we studied the prospects of Quasi-2D perovskites for lasing by first delving into excitonic and free carrier ultrafast dynamics, exploring into random lasing from naturally formed cavities in planar films and investigating lasing from structurally-tuned nanowires. Our results give insights on the fundamental radiative processes in these novel materials and build a foundation for future experiments and applications.
Dynamic control over the permittivity of materials enables control over the amplitude, phase, and polarization of light. Thus, to realize practical tunable devices, it is important to perform a detailed dynamic characterization of technology-relevant materials with substantially tunable optical properties. In this work, we demonstrate extraordinarily large, unity-order permittivity modulation in zinc oxide through interband pumping. The large permittivity changes actively enable large reflectance modulation in both lithography-free mirrors (70% at 31.6 mJ/cm2 pump) and nanodisk resonators (55% at 7.6 mJ/cm2 pump fluence). The relaxation time for this response is 20 ps. We explore the physical origins of the permittivity modulation and determine the physical limits. The results of this study will advance the realization of ultrafast dynamic optical devices for optical switching, beam-steering, and spectroscopy.
Controlling the permittivity of materials enables control over the amplitude, phase and polarization of light interacting with them. Tailorable and tunable transparent conducting oxides have applications in optical switching, beam steering, imaging, sensing, and spectroscopy.
In this work, we experimentally demonstrate wide tailoring and tuning of the optical properties of oxides to achieve fast switching with large modulation depths. In cadmium oxide, the permittivity and the epsilon-near-zero points can be tailored via yttrium doping to achieve large, ENZ-enhanced mid-IR reflectance modulation. In zinc oxide, the permittivity is tuned by interband pumping, achieving large reflectance modulation in the telecom regime. With aluminum-doped zinc oxide, we demonstrate tailorable Berreman-type absorbers that can achieve ultrafast switching in the telecom frequencies. Our work will pave the way to practical optical switching spanning the telecom to the mid-infrared wavelength regimes.
All-optical switching of metasurfaces enables dynamic control of the amplitude, phase and the polarization of light at picosecond timescales. The large free-carrier induced permittivity changes in transparent conducting oxides enable all-optical switching at femtosecond to picosecond timescales in planar, unpatterned films, without the need for lithography.
In this work, we experimentally demonstrate the wide-tuning of the optical properties of three materials to achieve fast optical switching with large modulation depth. Lithography-free designs such as Fabry-Perot cavities, metal-dielectric mirrors, and Berreman-type metasurfaces are demonstrated to showcase optical switching at powers on the order of 1 mJ/cm2. The switching speeds can vary from 50 ps in cadmium oxide, 20 ps in ZnO to 2 ps in aluminum-doped zinc oxides. Our work will pave the way to practical optical switching spanning the telecom to the mid-infrared wavelength regimes.
We experimentally investigate how the static and dynamic optical properties of cadmium oxide evolve with yttrium doping, for the design of optical and plasmonic devices spanning the near-infrared to the mid-infrared wavelengths. The metallicity is seen to increase and the epsilon-near-zero point blue-shifts with increasing yttrium-concentrations. We demonstrate broadband, optical-pump-induced reflection and transmission modulation ((up to 135% near ENZ), with picosecond response-times controlled by doping-concentration.
All-optical modulation of light using metallic nanostructures can potentially enable processing of information with speed in the terahertz range. This is because the optical nonlinearity of metals dictated by the electron-phonon coupling is intrinsically fast. Nobel metals have achieved great success to this end due to their superior plasmonic properties in the visible. However, each type of noble metals only works in a specific wavelength range and therefore broadband spectral response covering the wide visible spectrum can be a challenge. Here we introduce indium-tin-oxide nanorod arrays (ITO-NRAs) which exhibit broadband response covering the visible spectrum. We show that the static spectral response of ITO-NRAs does not depend on the incident polarization and is insensitive to whether the lattice is a square or a rectangle. We further demonstrate that the transmission spectrum can be slightly shifted by changing the sample temperature, as well as adjusting the doping concentration which can be achieved by annealing the sample in oxygen rich environments. When pumped by an optical pulse with photon energy above the bandgap, the transmission can be modified in the entire visible range. These preliminary results show that ITONRAs offer unique opportunities for all-optical modulation in optical frequencies.
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