10-fold detection range increase in quadrant-photodiode position sensing for photonic force microscope.

Area of Science:

• Optics and Photonics
• Nanotechnology
• Microscopy

Background:

• Photonic force microscopy (PFM) is crucial for nanoscale force measurements.
• Quadrant photodetectors (QPDs) are standard sensors in PFM for probe displacement detection.
• Current QPD-based PFM systems have limited detection ranges, restricting their application scope.

Purpose of the Study:

• To develop a technique for significantly extending the detection range of QPDs in PFM.
• To overcome the limitations of linear response assumptions in QPD signal processing.
• To improve the sensitivity and applicability of photonic force microscopy.

Main Methods:

• Utilizing the inherent cross-talk between QPD output signals.
• Developing a non-linear signal processing method for QPD outputs.
• Implementing the technique on a PFM setup with a trapped polystyrene sphere probe.

Main Results:

• Achieved a tenfold increase in the position sensing detection range.
• Extended the detection range from 150 nm to 1400 nm.
• Demonstrated the technique's effectiveness with a 300 nm radius polystyrene sphere probe.

Conclusions:

• The proposed technique effectively enhances the detection range of QPDs in PFM.
• This advancement broadens the operational capabilities of photonic force microscopy.
• Non-linear signal analysis of QPD cross-talk offers a powerful method for improving sensor performance.