Optical proximity sensors using multiple quantum well didoes.

Area of Science:

• Semiconductor Physics
• Optoelectronics
• Materials Science

Background:

• Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) multiple quantum well (MQW) diodes exhibit multifunctional capabilities including light emission, modulation, and detection.
• The spectral overlap between electroluminescence (EL) and responsivity in MQW diodes allows for inter-diode light sensing.
• Existing optical sensor systems often rely on discrete, bulky components.

Purpose of the Study:

• To develop a compact, monolithic optical proximity sensing system.
• To leverage the unique spectral properties of InGaN/GaN MQW diodes for integrated sensing.
• To demonstrate the sensor's capability for noncontact detection of distance, vibration, and pressure.

Main Methods:

• Integration of an MQW-based light transmitter and detector onto a single Gallium Nitride-on-sapphire chip.
• Utilizing environmental modulation of transmitted light, with reflected light detected by the integrated MQW detector.
• Conversion of detected optical signals into extractable electrical signals for data processing.

Main Results:

• Achieved a maximum detection proximity of approximately 17 mm.
• Demonstrated a displacement detection accuracy within 1 mm.
• Successfully extended the sensor's application to detect vibrations and pressure based on distance measurements.

Conclusions:

• The monolithic integration of InGaN/GaN MQW transmitter and detector offers a miniaturized solution for reflective optical sensors.
• This novel design can replace conventional discrete optical sensing components, paving the way for advanced, compact optical sensor architectures.
• The system's versatility allows for diverse applications beyond simple proximity sensing.