Abstract

The spaser (a plasmonic nanolaser) has rapidly advanced as a subwavelength light source candidate. Herein, we introduce a spaser based on a quantum-dot, mesoporous-oxide, and metal structure from top to bottom consisting of CdS/ZnS core/shell quantum dots, a mesoporous silica film (MSF), and an Au film, respectively. Two-photon pumping using femtosecond laser pulses at 800 nm creates amplified spontaneous emission at approximately 451 nm. The advantages of MSF as a dielectric gap layer are examined through numerical simulations. Measuring the dependence of the luminescence intensity on the average pump power confirms the occurrence of two-photon up-conversion luminescence.

Highlights

  • Laser miniaturization is a key factor in the integration of photonic devices and has the potential to improve on-chip optical communications, medical imaging, and sensing.1–5 The dimensions of traditional miniaturized semiconductor nanolasers have only ever been slightly reduced due to the diffraction limit

  • Several semiconductor materials have been previously employed as gain materials in spasers, including gallium nitride (GaN), cadmium sulfide (CdS), cadmium selenide (CdSe), and perovskite materials

  • The high performance of fluorescence up-conversion in the near-infrared region coupled with light in this spectral region inflicting minimal damage to biological tissues has enabled the unique potential of CdS quantum dots (QDs) in biological applications

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Summary

Introduction

Laser miniaturization is a key factor in the integration of photonic devices and has the potential to improve on-chip optical communications, medical imaging, and sensing. The dimensions of traditional miniaturized semiconductor nanolasers have only ever been slightly reduced due to the diffraction limit. Researchers have fabricated spasers with specific structures that are smaller than the diffraction limit in two and three dimensions based on the theory of plasmonics.. Several CdS-based nanostructures, such as nanorods, nanotubes, and nanosheets, have been used to build spasers.19–21 Compared with these nanostructures, quantum dots (QDs) have smaller dimensions and their luminescence mechanism is related to surface effects.. The high performance of fluorescence up-conversion in the near-infrared region coupled with light in this spectral region inflicting minimal damage to biological tissues has enabled the unique potential of CdS QDs in biological applications.. The high performance of fluorescence up-conversion in the near-infrared region coupled with light in this spectral region inflicting minimal damage to biological tissues has enabled the unique potential of CdS QDs in biological applications.26,27 Research on this property of CdS QDs in spasers holds considerable promise A spaser can amplify surface plasmons (SPs) using semiconductor dielectrics as the gain material to generate collective electron oscillations at a metal–dielectric interface. Researchers have fabricated spasers with specific structures that are smaller than the diffraction limit in two and three dimensions based on the theory of plasmonics. Several semiconductor materials have been previously employed as gain materials in spasers, including gallium nitride (GaN), cadmium sulfide (CdS), cadmium selenide (CdSe), and perovskite materials. CdS has been commonly applied in spasers because of its unique properties, including its direct bandgap, relatively low work function, and excellent transport. Several CdS-based nanostructures, such as nanorods, nanotubes, and nanosheets, have been used to build spasers. Compared with these nanostructures, quantum dots (QDs) have smaller dimensions and their luminescence mechanism is related to surface effects. The electronic oscillation of SPs is an interfacial effect, and interactions between these effects can produce interesting new phenomena, such as multiphoton absorption enhancement and fluorescence enhancement. The high performance of fluorescence up-conversion in the near-infrared region coupled with light in this spectral region inflicting minimal damage to biological tissues has enabled the unique potential of CdS QDs in biological applications. research on this property of CdS QDs in spasers holds considerable promise

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