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Self-rolled-up microtubes have been developed over the past decade as optical ring resonators, which exhibit unique merits such as directional emission, perfect emitter-field overlap, controlled transferability and flexible structural design, and find various applications in coherent light sources, micro-sensing, nanomechanics and topological devices. Nevertheless, the reported rolled-up microtube resonators so far are based on either passive material or active media with relatively small exciton binding energy and oscillator strength, making it less favorable for strong light-matter interaction at room temperature. Although wide bandgap materials, such as GaN, ZnO and organics, exhibit large exciton binding energy and oscillator strength, it is very challenging to make such materials into 3D rolled-up structures. In this work, we overcome the technical difficulties and fabricat GaN-based self-rolled-up microtubes from coherently strained AlGaN/GaN bilayer around 50nm thick with an embedded InGaN quantum well grown by MOCVD. Such ultrathin-walled microtubes can then be easily shifted onto an etched trench to become freestanding, with a typical Q-factor measured to be over 800. Both the on-substrate and freestanding microtubes exhibit lasing at room temperature, which have not been observed on ultrathin-walled microtubes based on other materials, highlighting the outstanding optical properties of the active media. Based on the same method, we also fabricated self-bent-up microdisks which support 3-dimensional WGM with a Q-factor of ~1300 and single mode lasing at room temperature, which is not achieved by conventional microdisks with the same size and material. Such rolled-up devices provide the degree of freedom of the WGM photons in the vertical dimension and is promising for applications in multifunction on-chip devices.
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