Whispering Gallery Mode Lasing Performance's Evolution of Floating GaN Microdisks Varying with Their Thickness

Optical gain and loss of microcavity greatly affect the quality of lasing,how to improve optical gain and decrease optical loss is of great significance for the preparation of laser.In this study,four types standard microdisks with different thicknesses of 2.2μm,1.9μm,1.7μm,and 1.45μm were fabricated by micromachining technology process to modulate optical gain and loss of microdisk lasing.The whispering gallery mode lasing in the ultraviolet range of Ga N microdisk devices was investigated for these devices in order to clarify the effect of microdisk thickness on device characteristics.The quality factor Q and lasing mode number for different thicknesses are calculated from the stimulated spectra.The lifetimes of the exciton combination properties of the devices were observed using time-resolved PL spectroscopy.The lasing modes are modulated,and the lifetime decreases,while the Q factor of the devices first increases and then decreases with decreasing thickness.All these results are induced by optical gain and loss competition.

Concentration sensing system with monolithic InGaN/GaN photonic chips

Using an identical monolithic InGaN/GaN light emitting diode (LED) array as the sensing module and a well-designed data processing module, we demonstrate a small-size concentration sensing prototype. Overlap between the emission and the response spectra of the InGaN/GaN LED makes each pair of LEDs in the arrayed chip form a sensing channel. The changes in liquid concentration can be transformed into variation of photocurrent. The system's sensing properties are further optimized by varying the position, number of receivers, and packaging reflectors. With methyl orange as a tracer agent, the sensing system's resolution is 0.286 μmol/L with a linear measurement region below 40 μmol/L.

Doped microspheres for whispering gallery mode microlasing

Whispering gallery mode(WGM)optical microcavities,which are capable of light field confinement and manipulation in a relatively small volume,have gained considerable attention from fundamentals in enhanced light-matter interactions to laser applications[1].Undergoing decades of development,the improvement of lasing performance is always a significant issue,including low threshold and high quality(Q)factor[2].Increasing optical gain and reducing the losses are the key aspects towards the realization of a high-quality WGM laser.A perfect cavity structure and a smooth surface are the most crucial determinants to reduce optical losses and enhance light field confined abilities.

Optical trapping-enhanced probes designed by a deep learning approach

Realizing optical trapping enhancement is crucial in biomedicine,fundamental physics,and precision measurement.Taking the metamaterials with artificially engineered permittivity as photonic force probes in optical tweezers will offer unprecedented opportunities for optical trap enhancement.However,it usually involves multi-parameter optimization and requires lengthy calculations;thereby few studies remain despite decades of research on optical tweezers.Here,we introduce a deep learning(DL)model to attack this problem.The DL model can efficiently predict the maximum axial optical stiffness of Si∕Si_(3)N_(4)(SSN)multilayer metamaterial nanoparticles and reduce the design duration by about one order of magnitude.We experimentally demonstrate that the designed SSN nanoparticles show more than twofold and fivefold improvement in the lateral(k_(x)and k_(y))and the axial(k_(z))optical trap stiffness on the high refractive index amorphous TiO_(2)microsphere.Incorporating the DL model in optical manipulation systems will expedite the design and optimization processes,providing a means for developing various photonic force probes with specialized functional behaviors.

Electrically pumped optomechanical beam GaN-LED accelerometer based on the quantum-confined Stark effect

Micro-nano optomechanical accelerometers are widely used in automobile,aerospace,and other industrial applications.Here,we fabricate mechanical sensing components based on an electrically pumped GaN light-emitting diode(LED)with a beam structure.The relationship between the blueshift of the electroluminescence(EL)spectra and the deformation of the GaN beam structure based on the quantum-confined Stark effect(QCSE)of the InGaN quantum well(QW)structure is studied by introducing an extra mass block.Under the equivalent acceleration condition,in addition to the elastic deformation of GaN-LED,a direct relationship exists between the LED’s spectral shift and the acceleration’s magnitude.The extra mass block(gravitational force:7.55×10^(-11)N)induced blueshift of the EL spectra is obtained and shows driven current dependency.A polymer sphere(PS;gravitational force:3.427×10^(-12)N)is placed at the center of the beam GaN-LED,and a blueshift of 0.061 nm is observed in the EL spectrum under the injection current of 0.5 mA.The maximum sensitivity of the acceleration is measured to be 0.02 m∕s^(2),and the maximum measurable acceleration is calculated to be 1.8×10^(6)m∕s^(2).It indicates the simultaneous realization of high sensitivity and a broad acceleration measurement range.This work is significant for several applications,including light force measurement and inertial navigation systems with high integration ability.