An MOF-Based Multicolor Single-Mode Microlaser

Optical micrographs of hierarchically dye-assembled ZJU-68 microcrystals. (Source: H. He et al., Zhejiang U.)

Since different tissues, cells or bio­chemicals have different – such as optical, thermal and acoustic – responses to different wave­lengths of light, a light source with visible to near-infrared (NIR) multicolor output provides the funda­mental for multi-modal/multidimensional sensing/imaging. On the other hand, the polari­zation properties of light provide an oppor­tunity for the analysis and processing of scattered light signals and can also help to obtain rich structural infor­mation in biological materials.

In addition, single-mode micro-nano lasers meet the appli­cation requirements of miniaturized photonic devices with high infor­mation accuracy, avoiding false signals and overlapping inter­ference of different optical signals, which have the potential to achieve targeted sensing/imaging of various cells and molecules when combined with multi-color output charac­teristics. If a material can combine the advantages of broadband multi-color output, polarization and single-mode micro-nano lasing, it is very useful for multi-mode minia­turized biochemical sensing or imaging, but there is no report of corres­ponding materials to date.

Now, a research group led by Guodong Qian from the Zhejiang University in Hangzhou have reported the hierarchical assembly of different dye molecules based on homo­epitaxy process in a host-guest hybrid metal-organic framework (MOF) micro-resonator to achieve up to three-wave­length single-mode polarized lasing in green, red and NIR. The segmented and oriented assembly of different dye molecules within the MOF micro­crystal (named ZJU-68) acting as shortened resonator, help to achieve dynamically controllable multi-color single-mode lasing with a low three-color-lasing threshold of 1.72 mJ/cm2 and degree of polari­zation >99.9 %. Furthermore, the resulting three-color single-mode lasing possesses the largest wavelength coverage of ~186 nm (range from 534 nm to 720 nm) ever reported.

The researchers summarized their ideas: “It is well known that the spatial confinement effect of the metal-organic framework can greatly reduce the aggre­gation-caused quenching (ACQ) of organic dye systems. However, when we need to load different dye molecules to broaden the emission band, how should we try to avoid their adverse energy transfer between each other, especially for the lasing system that requires extremely large optical gain? Fortu­nately, we found one of the solutions, that is the combi­nation of in-situ assembly and epitaxial growth.”

“Of course, the size matching between the host framework channels and the dye molecules is also an important factor for the final successful hierar­chical assembly. Because we need the prepared dye-loaded crystal segments to not leak the previous dye molecules during the epi­taxial growth process,” they added. “These MOF-based hybrid micro­crystals can be selectively regionally excited to produce single-mode linearly polarized lasing in green, red, and near-infrared, which will be potential in multi-modal bio­chemical sensing/imaging and on-chip photon infor­mation processing.” (Source: LPC-CAS)

Reference: H. He et al.: Controllable broadband multicolour single-mode polarized laser in a dye-assembled homoepitaxial MOF microcrystal, Light Sci. Appl. 9, 138 (2020); DOI: 10.1038/s41377-020-00376-7

Link: State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China

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