Nano-displacement sensing by phase-diversity optical digital coherent detection utilizing alternating quadrature...

Area of Science:

• Optical Metrology
• Nanotechnology
• Sensing Systems

Background:

• Non-contact displacement sensing is crucial for precision manufacturing and scientific research.
• Previous methods using narrow-linewidth (NLW) lasers and 90° optical hybrids were complex and expensive.
• There is a need for more cost-effective and streamlined nanometer-scale sensing solutions.

Purpose of the Study:

• To introduce a simplified and economical nanometer-scale non-contact displacement sensing system.
• To demonstrate the feasibility of using alternating quadrature phase modulation (AQPM) with a distributed feedback (DFB) laser for displacement sensing.
• To evaluate the performance and potential of the new system compared to existing technologies.

Main Methods:

• Implemented a phase-diversity optical digital coherent detection system.
• Utilized alternating quadrature phase modulation (AQPM) reference light generated by a phase modulator and a balanced amplified photodetector (BAP).
• Employed an economical distributed feedback (DFB) laser instead of a narrow-linewidth (NLW) laser.

Main Results:

• Achieved nanometer-scale displacement sensing with a capability of 1.6 nm and a resolution of 0.6 nm using the DFB-AQPM system.
• Observed performance degradation due to phase noise compared to the NLW laser system (0.6 nm sensing, 0.2 nm resolution).
• Demonstrated the effectiveness of the streamlined configuration for high-resolution sensing.

Conclusions:

• The DFB-AQPM system offers a significant advancement in cost-effective nanometer-scale displacement sensing.
• The simplified configuration reduces complexity and cost while maintaining high resolution.
• This technology holds substantial potential for widespread adoption in various high-precision applications.