Polarized three-photon-pumped laser in a single MOF microcrystal

Higher order multiphoton-pumped polarized lasers have fundamental technological importance. Although they can be used to in vivo imaging, their application has yet to be realized. Here we show the first polarized three-photon-pumped (3PP) microcavity laser in a single host–guest composite metal–organic framework (MOF) crystal, via a controllable in situ self-assembly strategy. The highly oriented assembly of dye molecules within the MOF provides an opportunity to achieve 3PP lasing with a low lasing threshold and a very high-quality factor on excitation. Furthermore, the 3PP lasing generated from composite MOF is perfectly polarized. These findings may eventually open up a new route to the exploitation of multiphoton-pumped solid-state laser in single MOF microcrystal (or nanocrystal) for future optoelectronic and biomedical applications.

3PP F-P lasing (one-spot pattern, b). (c-d) Mode spacing (Δ s , around 635 nm) as a function of the inverse of side length (R) towards two 3PP lasing performances (c for two-spot lasing pattern and d for one-spot lasing pattern) with different feedback mechanisms. It should be noted that the ratio of slopes in these two formulas is calculated to be S one-spot /S two-spot = 1.47  1.5, consistent with the ratio of the cavity path lengths of the WGMs and F-P cavity mechanisms (L WGMs /L F-P ).   Figure 11). Ethyl 7-bromoquinoline-3-carboxylate (2.8 g, 10 mmol), K 2 CO 3 (2.8 g, 20 mmol), and (4-(methoxycarbonyl)phenyl)boronic acid (2.7 g, 15 mmol) were dissolved in dioxane (100 mL).

Measurements
Micrographs and microscopic spectra were taken on an Olympus IX71 inverted fluorescence microscope. Confocal laser scanning images were taken on an Olympus FV1000 laser scanning confocal microscope equipped with an Olympus IX81 inverted microscope.
The decay curves of multiphoton pumped emissions were measured by a picosecond lifetime spectrometer (Lifespec-ps, Edinburgh Instruments). For the lifetime measurement of upconverted fluorescence, the pump power was under the lasing threshold to ensure that no stimulated emission was generated. To measure the decay of the multiphoton pumped lasing, the pump power was enhanced over the threshold so that the ultra-strong lasing could be achieved.
Quantum yield measurements were performed using the absolute method on a FLS920 from Edinburgh Instruments equipped with a BaSO 4 -coated integrating sphere, a 450W Xe900 Xenon lamp and a R928P PMT detector. The samples ZJU-68DMASM were measured at an excitation S19 wavelength of 450 nm (Supplementary Figure 6). A 142-mm (inner)-diameter integrating sphere equipped with a cuvette holder and mounts for solid samples and two access ports for the light path was fitted in place of the standard sample holder to collect the excitation and emission light.
The absolute quantum yields were calculated by comparing the integral of emission and the absorption of excitation light, with a sensitivity correction for the detector.

Determination of dye contents.
Contents of well-dried dye-included ZJU-68DMASM crystals were determined by 1 H NMR.