Rotational angle and speed detection via a chip-scale GaN optoelectronic device.

In this paper, a new method for rotational angle and speed measurements is proposed by integrating a GaN optoelectronic chip with a stepped disc. The optoelectronic chip that integrates a light-emitting diode (LED) and a photodiode (PD) is fabricated by wafer-level microfabrication. The disc is designed with a spiral staircase shape, and has increasing thickness distribution along the circumferential direction. The sensing mechanism is that the optoelectronic chip measures angle-dependent intensity change of the light reflected off the stepped disc. Through a series of performance tests, the chip is highly sensitive to a continuous rotation from 0 ∘ to 360 ∘, and produces photocurrent to indicate the rotational angle and speed. A rotational speed up to 5000 rpm is measured with a relative error less than 1.27%. The developed sensing architecture provides an alternative solution for constructing a low-cost, miniaturized, and high-efficiency rotational angle and speed sensing system.

Effect of temperature on GaN-integrated optical transceiver chips.

The gallium nitride (GaN) integrated optical transceiver chip based on multiple quantum wells (MQW) structure exhibits great promise in the fields of communication and sensing. In this Letter, the effect of ambient temperature on the performance of GaN-integrated optical transceiver chips including a blue MQW light-emitting diode (LED) and a MQW photodiode (PD) is comprehensively studied. Temperature-dependent light-emitting and current-voltage characteristics of the blue MQW LEDs are measured with the ambient temperature ranging from -70°C to 120°C. The experimental results reveal a decline in the electroluminescent (EL) intensity and an obvious redshift in the emission peak wavelength of the LED with increasing ambient temperature. The light detection performance of MQW PD under different temperatures is also measured with the illumination of an external blue MQW LED, indicating an enhancement in the PD sensitivity as the temperature rises. Finally, the temperature effect on the MQW PD under the illumination of the MQW LED on the GaN-integrated optical transceiver chip is characterized, and the PD photocurrent increases with higher ambient temperature. Furthermore, the measured temperature characteristics indicate that the GaN-integrated optical transceiver chip offers a promising application potential for optoelectronic temperature sensor.

Large-sized light-emitting diode integrated with a thermopile for on-chip temperature and power monitoring.

A large-sized multiple quantum well (MQW) light-emitting diode (LED) integrated with a thermopile for on-chip temperature and power monitoring is presented in this study. Seven thermopile structures, fully compatible with the fabrication of LEDs, are strategically placed at different locations on the LED to monitor its temperature during the operation. Additionally, the thermopile allows for monitoring the power of the LED, as there exists an approximate linear relationship between the light output power and temperature. Compared to traditional methods of measuring LED temperature, the thermopile offers several advantages, including no moving parts, long lifetime, no maintenance, high reliability, and direct conversion without intermediate processes. The results demonstrate that the integration of the thermopiles onto the LED provides superior temperature and power monitoring capabilities. Furthermore, this integrated solution has the potential to enable real-time management and control of LED temperature.

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.