Ultrafast Control of Phase and Polarization of Light Expedited by Hot-Electron Transfer

All-optical modulation is an entangled part of ultrafast nonlinear optics with promising impacts on tunable optical devices in the future. Current advancements in all-optical control predominantly offer modulation by means of altering light intensity, while the ultrafast manipulation of other attributes of light have yet to be further explored. Here, we demonstrate the active modulation of the phase, polarization, and amplitude of light through the nonlinear modification of the optical response of a plasmonic crystal that supports subradiant, high Q, and polarization-selective resonance modes. The designed mode is exclusively accessible via TM-polarized light, which enables significant phase modulation and polarization conversion within the visible spectrum. To tailor the device performance in the time domain, we exploit the ultrafast transport dynamics of hot electrons at the interface of plasmonic metals and charge acceptor materials to facilitate an ultrafast switching speed. In addition, the operating wavelength of the proposed device can be tuned through the control of the in-plane momentum of light. Our work reveals the viability of dynamic phase and polarization control in plasmonic systems for all-optical switching and data processing

Resonant Light-Induced Heating in Hybrid Cavity-Coupled 2D Transition-Metal Dichalcogenides

Hybrid structures based on integration of two-dimensional (2D) transition-metal dichalcogenides (TMDCs) with optical resonators have recently earned significant attention. The enhanced interaction of light with 2D materials in such hybrid structures can enable devices such as efficient light-emitting diodes and lasers. However, one of the factors affecting the performance of such devices is the effect of the optically induced heat on the optoelectronic properties of the 2D materials. In this study, we systematically investigate principal roots of heat generation in hybrid cavity-coupled few-atomic-layer-thick 2D TMDC films under optical pumping. The optical resonator exploited here is a Fabry–Perot (FP) resonator, which can enhance the light–MoS₂ interaction by a significant factor of 60 at its resonance wavelength. We have combined an accurate theoretical modeling with experimental Raman spectroscopy to determine the roots of heat generation in MoS₂ films integrated with FP resonators. Our investigations reveal that the strong modulation of light absorption in the MoS₂ film, induced by excitation of an FP cavity at its resonant frequency, plays the primary role in excess heat generation in 2D materials. Furthermore, through varying the cavity length, we show that on-resonance and off-resonance excitation of the cavity results in completely different temperature profiles in the cavity-coupled MoS₂ films. Also, by changing the resonance medium of the FP cavity (SiO₂ and air), we take into account the role of the heat sinking effect of the substrate in heat generation in MoS₂ films. In this study, the temperature-dependent red-shift of the Raman spectra is employed to monitor the local temperature of the MoS₂ films. Our results show the importance of the heating effect in such hybrid structures and represent a step forward for the design of practical hybrid optical devices based on layered semiconducting 2D materials

Cell-Imprinted Substrates Act as an Artificial Niche for Skin Regeneration

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly­(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed (involucrin, collagen type I, and keratin 10) together with protein expression data showed that human adipose-derived stem cells (ADSCs) seeded on these cell-imprinted substrates were driven to adopt the specific shape and characteristics of keratinocytes. The observed morphology of the ADSCs grown on the keratinocyte casts was noticeably different from that of stem cells cultivated on the stem-cell-imprinted substrates. Since the shape and geometry of the nucleus could potentially alter the gene expression, we used molecular dynamics to probe the effect of the confining geometry on the chain arrangement of simulated chromatin fibers in the nuclei. The results obtained suggested that induction of mature cell shapes onto stem cells can influence nucleus deformation of the stem cells followed by regulation of target genes. This might pave the way for a reliable, efficient, and cheap approach of controlling stem cell differentiation toward skin cells for wound healing applications

Cell-Imprinted Substrates Act as an Artificial Niche for Skin Regeneration

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly­(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed (involucrin, collagen type I, and keratin 10) together with protein expression data showed that human adipose-derived stem cells (ADSCs) seeded on these cell-imprinted substrates were driven to adopt the specific shape and characteristics of keratinocytes. The observed morphology of the ADSCs grown on the keratinocyte casts was noticeably different from that of stem cells cultivated on the stem-cell-imprinted substrates. Since the shape and geometry of the nucleus could potentially alter the gene expression, we used molecular dynamics to probe the effect of the confining geometry on the chain arrangement of simulated chromatin fibers in the nuclei. The results obtained suggested that induction of mature cell shapes onto stem cells can influence nucleus deformation of the stem cells followed by regulation of target genes. This might pave the way for a reliable, efficient, and cheap approach of controlling stem cell differentiation toward skin cells for wound healing applications

Cell-Imprinted Substrates Act as an Artificial Niche for Skin Regeneration

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly­(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed (involucrin, collagen type I, and keratin 10) together with protein expression data showed that human adipose-derived stem cells (ADSCs) seeded on these cell-imprinted substrates were driven to adopt the specific shape and characteristics of keratinocytes. The observed morphology of the ADSCs grown on the keratinocyte casts was noticeably different from that of stem cells cultivated on the stem-cell-imprinted substrates. Since the shape and geometry of the nucleus could potentially alter the gene expression, we used molecular dynamics to probe the effect of the confining geometry on the chain arrangement of simulated chromatin fibers in the nuclei. The results obtained suggested that induction of mature cell shapes onto stem cells can influence nucleus deformation of the stem cells followed by regulation of target genes. This might pave the way for a reliable, efficient, and cheap approach of controlling stem cell differentiation toward skin cells for wound healing applications