Dynamically Modulated GaN Whispering Gallery Lasing Mode for Strain Sensor

Abstract

The continuous development of strain sensors offers significant opportunities for improving human-machine interfaces and health monitoring. The dynamically modulated lasing mode is a novel approach to realize a flexible, noncontact, high color-resolvability, high-resolution, and ultrasensitive strain sensor. Here, a flexible strain sensor perceiving stress variations is reported via the dynamical regulation of a GaN whispering gallery lasing mode based on the piezoelectric effect. The refraction index of GaN shows a linear relationship with the applied external tensile strain, resulting in a redshift phenomenon of the lasing mode peak at room temperature due to the predominant function of the piezoelectric polarization in the GaN microwire. Compared with a strain sensor relying on the wavelength shift of a photoluminescence (PL) emission peak, the differences and advantages of a sensor based on the strain-induced lasing mode variation are also investigated and analyzed systematically. This strain sensor may serve as an essential step toward the color mapping of mechanical signals by optical methods, with potential applications in color-perceived touching sensing, noncontact stress measurement, laser modulation, and optical communication technologies.

Piezophototronic Effect in Nanosensors

“…Adapted with permission. [ 94 ] Copyright 2019, Wiley‐VCH. b) Optical image of the single ZnO NW with the two ends fixed on the flexible substrate.…”

“…Furthermore, they transferred the GaN microwires synthesized by CVD method to the flexible substrates, and then studied the GaN microcavity lasing mode under strain by applying pressure on the substrate. [ 94 ] Due to the piezoelectric polarization effect of wurtzite structure GaN, the piezophototronic effect will affect the refractive index of GaN, so as to achieve the dynamic controlling the laser mode under stress (Figure 9e). The refractive index of GaN changed linearly with the increase in applied tensile strain.…”

“…“NW lasing strain sensors” Reproduced with permission. [ 94 ] Copyright 2019, Wiley‐VCH. “New tactile sensors” Reproduced with permission.…”

Highly Stretchable, Adhesive, and Self‐Healing Silk Fibroin‐Dopted Hydrogels for Wearable Sensors

“…Flexible sensors have been widely used in human motions detection, [1] health monitoring, [2][3][4][5][6][7][8][9][10] electronic skin, [11][12][13][14][15] soft robots, [12,16,17] and human-computer interaction. [18][19][20] Normally, these sensors are usually designed with conductive materials (such as metal nanowires, [21][22][23] conductive polymers, [24][25][26] and DOI: 10.1002/adhm.202002083 carbon materials [27][28][29][30] ) on flexible substrates, and they work by converting mechanical deformations under external force into electrical signals such as resistance or capacitance. However, the low tensile property, poor durability, and irreparable damage restrict their further applications.…”

A Self‐Powered Photodetector Based on MAPbI3 Single‐Crystal Film/n‐Si Heterojunction with Broadband Response Enhanced by Pyro‐Phototronic and Piezo‐Phototronic Effects

“…Besides, piezo‐phototronic effect, a three‐way coupling effect among piezoelectricity, photoexcitation, and semiconductor, can also be utilized to modulate the performance of optoelectronic devices. [ 35–37 ] External stress‐induced piezo‐charges at the interface can also effectively modulate the optoelectronic processes. This effect had been proven to enhance the performances of halide perovskite‐based PDs [ 38,39 ] and combined with pyro‐phototronic effect to further boost the ZnO‐based PDs’ performance.…”