Compact shearing interferometry surface plasmon resonance biosensor based on VCSEL wavelength modulation

Le résumé fourni par la source

Abstract Phase-sensitive surface plasmon resonance sensors (pSPRs) offer high detection sensitivity; however, their sophisticated optical design and susceptibility to noise hinder broader adoption. To address such concerns, we propose a new genre of phase-sensitive plasmonic sensors, named shearing interferometery SPR (SiSPR). This novel proposition combines an ‘on-the-chip’ interferometry design and a tailored phase extraction strategy. This design leads to a pSPR level detection sensitivity without compromising robustness and setup simplicity. The SiSPR chip is made of a double-sided coated design, which generates monolithic interferometric sensing performance and minimizes the need for multiple optics required in conventional settings. A vertical cavity surface emitting laser (VCSEL) diode is then used to extract phase information, taking advantage of its wavelength tunability. VCSEL is used both as an optical source and phase modulator, further eliminating the need for phase modulation components. The use of VCSEL current drive to excite phase modulation comes with the challenge of having residual power modulation. Therefore, a digital lock-in amplifier is designed to address this problem. The experimental data reveal that the SiSPR offers low-noise measurements down to 1.4 × 10 −4 rad, with a limit of detection down to 5.5 × 10 − 8 RIU. Meanwhile, the setup still delivers exceptional noise canceling capacity, as shown by its long-term baseline stability over 9000 s. The primary reason for these performances is attributed to the quasi-common-path chip design. Long-term drift issues are further addressed, using the P–S differential phasogram. To fully leverage the benefits of the proposed design, a portable version is realized using a smartphone. An exceptionally low noise level is still achieved under portable configuration. The noise resistance capacity and the potential for miniaturization make SiSPR a highly promising establishment for point-of-care applications in the future.

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