Research On Optomechanical Acoustic Sensor Based On GaN Microcavity

Ga N,a typical representative of the third generation semiconductor materials,has the advantages of large band gap,strong radiation resistance and stable chemical properties.It has been widely used in emerging industries such as electronic information,5G communication and new energy.With its unique mechanical and optical properties,it has attracted extensive attention in the application of sensors.At present,most acoustic sensors transform an acoustic pressure wave into vibrations of a mechanical element,and detect these vibrations quantitatively via changes in piezoelectricity,resistivity,magnetic transduction or capacitance.This form of sensor has a large size,high transmission load impedance and large optical loss,which is significantly affected by noise.For more and more applications,high spatial,temporal and directional resolution has become the key demand of such devices.In recent ten years,optomechanical sensors have emerged as a new class of ultraprecise photonic sensors.A characteristic feature of optomechanical sensors is that they are often only limited by optical shot noise and mechanical thermal noise,allowing the intrinsic limits in sensing performance to be approached.Therefore,the research on optomechanical acoustic sensors has become a hot spot in the field of acoustic sensing.From the perspective of the scientific research idea of new materials and new structures,a suspended Ga N-based Benz ring optomechanical acoustic sensor combining the third generation semiconductor material Ga N and optomechanical structure is proposed in this paper.The microcavity deformation caused by acoustic vibration will cause the change of resonant wavelength in Ga N active microcavity,so that the corresponding relationship between the acoustic wave and the laser frequency difference can be established,thus,the sound frequency can be reflected by the laser frequency difference.Based on this,this paper uses COMSOL software to carry out acoustic simulation experimental research on Ga N Benz ring optomechanical device in the three frequency ranges of ultrasonic,audible acoustic and infrasonic.Then,Ga N optomechanical device is designed and prepared with the help of laboratory instruments and micro nano processing technology,and its optical properties are analyzed and characterized.The research content of this paper mainly has two aspects.First,the acoustic response performance of Ga N Benz optomechanical device is explored from the perspective of simulation.Firstly,the sound field displacement simulation experiments of devices with radius of 50μm,75μm and 100μm are carried out by COMSOL software.It is found that under the same sound wave conditions,the annular microcavity shape variable of 100μm device is the largest,which reflects the highest sensitivity of this size device.Then,the deformation of the same device under three different direction sound sources of forward direction,lateral direction and 45° oblique direction is explored.It is found that the device shape variable under the45° oblique angle is the largest,reflecting the highest detection sensitivity of this angle.In addition,the low-frequency band of 0.02～200Hz and the high-frequency band of 20k～1MHz are studied.It is found that this device has very good deformation in the infrasound band of 0.02～5Hz,the audible sound band of 50～100Hz and the ultrasonic band above 20 k Hz,reflecting the large detection range of the acoustic sensor.The simulation theory research has important guiding significance for the design and preparation of optomechanical acoustic sensor.The second is to explore the optical response performance of this device from an experimental point of view.A silicon column supported suspended Benz ring microcavity device was designed and fabricated by dry etching Ga N and isotropic wet etching silicon.Its morphology is characterized by scanning electron microscope,and the optical properties of the device are explored with the help of spectral test system.The results show that the central wavelength of 100 micron device is 373.8 nm,FWHM is 0.25 nm,and the quality factor Q is as high as 1500.Finally,a photoacoustic testing system for photoacoustic coupling analysis is proposed and its rationality is explained theoretically.The high-Q Gan Benz ring optomechanical acoustic sensor designed and prepared in this paper has high acoustic sensitivity and the detection range covers the field of infrasound to ultrasonic.It has important research significance in micro high-precision sensors and has broad application prospects in the fields of medical diagnosis,sonar navigation,trace gas sensing and industrial processes.