Recently, wearable sensor technology has drawn attention to many health-related appliances due to its varied existing optical, electrical, and mechanical applications. Similarly, we have designed a simple and cheap lift-off fabrication technique for the realization of large-area biocompatible random lasers to customize wearable sensors. A large-area random microcavity comprises a matrix element polymethyl methacrylate (PMMA) in which rhodamine B (RhB, which acts as a gain medium) and gold nanorods (Au NRs, which offer plasmonic feedback) are incorporated via a spin-coating technique. In regards to the respective random lasing device residing on a heterogenous film (area > 100 cm²), upon optical excitation, coherent random lasing with a narrow linewidth (~0.4 nm) at a low threshold (~23 μJ/cm² per pulse) was successfully attained. Here, we maneuvered the mechanical flexibility of the device to modify the spacing between the feedback agents (Au NRs), which tuned the average wavelength from 612.6 to 624 nm under bending while being a recoverable process. Moreover, the flexible film can potentially be used on human skin such as the finger to serve as a motion and relative-humidity sensor. This work demonstrates a designable and simple method to fabricate a large-area biocompatible random laser for wearable sensing.

Light-emitting fabric can facilitate the innovation of wearable display applications. Electronic and luminescent textiles capable of communicating, sensing, and supplying energy have been achieved. However, a facile strategy for fabricating large-area flexible lasing textiles has not yet been reported. In this work, we propose a gravity-assisted rotatory drawing method for fabricating flexible lasing microfibers, which can be woven into multicolor lasing textiles. By regulating the doped dyes and solution viscosity, we achieve the mass manufacturing of lasing microfibers with different emission colors and modes and further weave them into full-color textiles with a wide color gamut, approximately 79.1% larger than that of standard RGB space. For application, we print nanoparticle patterns on the lasing textile and encode it with programmable lasing signal distribution, which can supply an anticounterfeiting label for efficient authentication. This work unifies the fabrication and application of lasing textiles, and we expect that this will provide a new platform for flexible lasing devices.

Lasing emissions with multiple and tunable modes are promising in coding field as a novel cryptographic primitive. With the advantages of simple fabrication, full-color and high-quality-factor whispering gallery mode lasing inside a circular cross-section, polymer microfibers are attractive for photonic devices. However, polymer lasing microfibers for information encryption have never been reported. Herein, we propose a design of printable lasing microfiber encryption chip by in-situ tuning the effective refractive index of the microresonator arrays via a facile approach. Through inkjet printing high-refractive-index nanoparticles on the designated position of lasing microfiber arrays, the effective refractive index of the microcavities is regulated, and the ratio of wavenumber spacing between transverse electric and transverse magnetic mode to the free spectral range can be modulated, particularly with neglectable influence by the size factor. Thus, the programmable region selective encoding process can be conducted simply by a printing program within several minutes. Besides, the encoded microfiber arrays are encapsulated into polydimethylsiloxane to reduce the scattering loss and environmental interference, and a printable encryption chip is realized. This work is expected to provide a platform for the printable encrypted devices.

Tunable whispering-gallery-mode (WGM) lasers have been paid lots of attention for their potential applications in the photonic field. Here, a tunable polymer WGM laser based on laser diode pumping is realized with a threshold of 0.43 MW/cm² per pulse. The WGM laser is realized by a microfluidic microcavity, which consists of a quartz capillary and gain materials. The laser performance keeps stable for a long time (3.5 h), pumped by a 50-ns 50 Hz laser diode with a pumping peak power density of 1.08 MW/cm² per pulse. The lasing wavelength can be tuned over 15 nm by changing the gain material concentration from 3.5 mg/mL to 12.5 mg/mL in the microfluidic channel. Moreover, the lasing mode can be switched between transverse magnetic (TM) and transverse electric (TE) modes by adjusting the pump polarization. These results provide the basis for designing nanophotonic devices with laser diode pumping.