Chip-scale packaged in-line polarization-resolved detector for optically pumped magnetometers

Area of Science:

• Quantum sensing
• Optics and photonics
• Materials science

Background:

• Optically pumped magnetometers (OPMs) are advanced quantum sensors vital for neuroscience, geophysics, and non-destructive testing.
• Current OPM detection methods use bulky components, hindering miniaturization.
• Faraday rotation detection in OPMs requires precise polarization measurement.

Purpose of the Study:

• To develop a miniaturized, chip-scale detector for OPMs.
• To improve the performance and reduce the size of OPM systems.
• To enable next-generation, field-deployable quantum sensing.

Main Methods:

• Integration of a wire grid polarizer (WGP) and a bi-cell photodiode into a chip-scale packaged in-line polarization-resolved detector (CSP-iPRD).
• Characterization of the WGP's polarization extinction ratio (PER) at 795 nm.
• Assembly and testing of the CSP detector, measuring common-mode rejection ratio (CMMR) and angular resolution.
• Incorporation of the CSP detector into a spin-exchange relaxation-free (SERF) OPM to evaluate magnetic sensitivity.

Main Results:

• The integrated WGP achieved a PER of 25.3 dB.
• The CSP detector (3.5×3.5×1.8 mm³) demonstrated a CMMR of 29.6 dB and angular resolution of 8.4 × 10⁻⁵ degree/Hz¹/².
• The SERF OPM with the CSP detector achieved a magnetic sensitivity of 33.5 fT/Hz¹/² at 10 Hz.

Conclusions:

• The CSP-iPRD offers a scalable, CMOS-compatible solution for OPM detection.
• This miniaturized detector significantly advances OPM technology.
• The developed platform supports the creation of smaller, more efficient quantum sensors for diverse applications.