Collinear optical links based on a GaN-integrated chip for fiber-optic acoustic detection

This Letter reports a collinear optical interconnect architecture for acoustic sensing via a monolithic integrated GaN optoelectronic chip. The chip is designed with a ring-shaped photodiode (PD) surrounding a light-emitting diode (LED) of a spectral range from 420-530 nm. The axisymmetric structure helps the coaxial propagation of light transmission and reception. By placing this multiple-quantum wells (MQW)-based device and a piece of aluminum-coated polyethylene terephthalate (Al/PET) film on fiber ends, an ultra-compact acoustic sensing system is built. The sound vibrations can be simply detected by direct measurement of the diaphragm deformation-induced power change. An average signal noise ratio (SNR) of 40 dB and a maximum sensitivity of 82 mV/Pa are obtained when the acoustic vibration frequency changes from 400 Hz to 3.2 kHz. This work provides a feasible solution to miniaturize the sensing system footprint and reduce the cost.