On-chip sensor for light direction detection.

Area of Science:

• Optoelectronics
• Integrated Photonics
• Semiconductor Devices

Background:

• Traditional optical direction sensors often require bulky external components like baffles or mirrors.
• Integrating sensing functionality directly onto a chip offers miniaturization and reduced system complexity.
• Standard semiconductor fabrication processes are desirable for cost-effective mass production.

Purpose of the Study:

• To develop an on-chip optical sensor for detecting incident light direction.
• To achieve directional sensing without external optical or mechanical modifications.
• To validate the sensor's performance, including its relationship with light angle and intensity.

Main Methods:

• Implementation of a novel sensor design using a standard 0.5 μm complementary metal-oxide semiconductor (CMOS) process.
• Utilizing a pair of on-chip photodiodes separated by a metal stack wall to create on-chip shadowing.
• Developing a theoretical model to describe the sensor's photocurrent response to incident light.

Main Results:

• The metal stack wall effectively creates shadowing, causing differential photocurrents between the photodiodes.
• A linear relationship was established between the photocurrent ratio and the incident light's angle.
• The sensor demonstrated robustness against variations in light intensity, with the ratio remaining largely independent.

Conclusions:

• The developed on-chip optical sensor reliably detects light direction with high sensitivity and accuracy.
• The sensor's performance is validated by experimental results, confirming the theoretical model's predictions.
• This integrated solution offers a compact, cost-effective alternative for directional light sensing applications.