研究 Research

High-Q lasing via all-dielectric Bloch-surface-wave platform

Controlling the propagation and emission of light via Bloch surface waves (BSWs) has held promise in the field of on-chip nanophotonics. BSW-based optical devices are being widely investigated to develop on-chip integration systems. However, a coherent light source that is based on the stimulated emission of a BSW mode has yet to be developed. Here, we demonstrate lasers based on a guided BSW mode sustained by a gain-medium guiding structure microfabricated on the top of a BSW platform. A long-range propagation length of the BSW mode and a high-quality lasing emission of the BSW mode are achieved. The BSW lasers possess a lasing threshold of 6.7 μJ/mm2 and a very narrow linewidth reaching a full width at half maximum as small as 0.019 nm. Moreover, the proposed lasing scheme exhibits high sensitivity to environmental changes suggesting the applicability of the proposed BSW lasers in ultra-sensitive devices.

• Y. C. Lee, Y. L. Ho, B. W. Lin, M. H. Chen, D. Xing, H. Daiguji, J. J. Delaunay*, Nature Communications (2023) 14, 1, 6458.

Integration of on-chip perovskite nanocrystal laser and
long-range surface plasmon polariton waveguide
with etching-free process

Perovskite materials prepared in the form of solution-processed nanocrystals and used in top-down fabrication techniques are very attractive to develop low-cost and high-quality integrated optoelectronic circuits. Particularly, integrated miniaturized coherent light sources that can be connected to light-guiding structures on a chip are highly desired. To control light propagating on a small footprint with low-loss optical modes, long-range surface plasmon polariton (LRSPP) waveguides are employed. Herein, we demonstrate an on-chip fabricated photonic-plasmonic hybrid system consisting of a perovskite lasing structure coupled to an LRSPP waveguide achieving a low lasing threshold and a propagation length over 100 μm. Preventing perovskite material degradation and the formation of surface roughness of the laser cavity during fabrication is made possible by designing a fabrication technique without any etching step.

• H. C. Lin#, Y. C. Lee#, C. C. Lin, Y. L. Ho, D. Xing, M. H. Chen, B. W. Lin, L. Y. Chen, C. W. Chen, J. J. Delaunay*, Nanoscale (2022) 14, 10075–10081.

Solution-Processable Three-Dimensional Metamaterials
with Ultrahigh Broadband Absorption for
Photothermal Electronic Conversion

Metamaterials are promising candidates for broadband light absorbers, but complex manufacturing procedures with expensive instruments have limited their practical applications. Herein, this work develops an all-solution-processed three-dimensional (3D) metamaterial—based on a gold nanocage (GNC)/silk fibroin (SF) nanocomposite thin film—that achieves near-unity (>94%) and broadband (350–2000 nm) light absorption. At a low particle density, the film exhibits a typical signal for localized surface plasmon resonance (LSPR) absorption at 856 nm, originating from its hollow geometrical shape of GNCs. In contrast, at high particle densities the films display ultrahigh broadband absorption, even in the non-LSPR regions. This work attributes this behavior to the highly dense GNCs dispersed uniformly in the SF matrix acting optically as extremely fragmented metallic films, thereby retaining the highly absorptive nature of the metal while strongly suppressing its highly reflective properties. Moreover, the metamaterial absorber displays a desirable broadband-light-induced photothermal effect when illuminated with a halogen lamp. Finally, investigations into the photothermal electronic properties of this metamaterial combined with an Al/Si Schottky diode reveal an excellent photoresponse and photostability. The as-designed systems can function at telecommunication wavelengths longer than the typical operation wavelengths of Si-based devices. Such 3D metamaterial absorbers can be efficient platforms for various photothermal applications.

• S. H. Tsao#, A. Y. Sun#, Y. C. Lee#, C. W. Hwang, K. T. Lin, Y. S. Lai, L. C. Yang, H. L. Chen*, D. Wan*, Laser & Photonics Reviews (2023) 17, 2300315.

Optical Inspection of 2D Materials: From Mechanical Exfoliation to Wafer-Scale Growth and Beyond

Optical inspection is a rapid and non-destructive method for characterizing the properties of two-dimensional (2D) materials. With the aid of optical inspection, in situ and scalable monitoring of the properties of 2D materials can be implemented industrially to advance the development and progress of 2D material-based devices toward mass production. This review discusses the optical inspection techniques that are available to characterize various 2D materials, including graphene, transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), group-III monochalcogenides, black phosphorus (BP), and group-IV monochalcogenides. First, the authors provide an introduction to these 2D materials and the processes commonly used for their fabrication. Then they review several of the important structural properties of 2D materials, and discuss how to characterize them using appropriate optical inspection tools. The authors also describe the challenges and opportunities faced when applying optical inspection to recently developed 2D materials, from mechanically exfoliated to wafer-scale-grown 2D materials. Most importantly, the authors summarize the techniques available for largely and precisely enhancing the optical signals from 2D materials. This comprehensive review of the current status and perspective of future trends for optical inspection of the structural properties of 2D materials will facilitate the development of next-generation 2D material-based devices.

• Y. C. Lee, S. W. Chang, S. H. Chen, S. L. Chen, H. L. Chen, Advanced Science (2022) 9, 2102128.