We present a high-sensitivity and high-resolution birefringence coefficient
determination system for nm-level membrane films based on weak measurement,
addressing the sensitivity-resolution trade-off. A tunable bandwidth light
source is exploited to achieve complementary momentum (P-pointer) and intensity
(I-pointer) measurements,enabling calibration-free operation across various
bandwidths, and to realize high-precision phase difference monitoring of the
measured membranes.This method maps the birefringence effect to a weak-value
amplified signal of spectral shift and light intensity. The optimal resolution,
achieved at a spectral width of 6 nm, is $1.5 \times 10^{-8}$ RIU, while the
optimal sensitivity is achieved when the light source is a narrow-linewidth
coherent laser, reaching 4710 mV/RIU. The linear range of the system covers a
broad birefringence coefficient range for crystals,from $10^{-6}$ to 0.1.
Furthermore, the auxiliary optical path eliminates substrate interference,
achieving a detection limit of the birefringence coefficient as low as
$10^{-8}$ RIU.This approach, characterized high precision, high sensitivity,
and strong robustness, provides an effective solution for the detection of
optical nano-thin membrane parameters.

Cet article explore les excursions dans le temps et leurs implications.

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