For two simultaneously varying external perturbation parameters, namely, temperature and strain, we propose and theoretically demonstrate a novel, to the best of our knowledge, scheme of developing inherently insensitive biosensors based on long-period fiber gratings (LPFGs). The insensitivities have been achieved by inherently nullifying (i) temperature-induced phases of the core and cladding modes by judiciously adjusting the core dopants and their concentrations and (ii) strain-induced phase changes generated inside one LPFG with that inside the other LPFG by optimizing the grating parameters (grating period, strength, and length). The resulting biosensor has ultrahigh overall bulk refractive index sensitivity of ${\sim}3\;\unicode{x00B5} {\rm{m/RIU}}$ for biosamples (RI varying in the range of 1.33 to 1.34 RIU) and an affinity sensitivity of ${\sim}1.4\;{\rm{nm/nm}}$ for biomolecules (${\rm{RI}} \sim 1.45\;{\rm{RIU}}$). Our study should find application in developing ultrasensitive, high-precision bio/chemical sensors that are inherently immune to environmental temperature and strain variations.

中文翻译：

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基于长周期光纤光栅的高灵敏度生物传感器固有地不受温度和应变影响

对于两个同时变化的外部扰动参数，即温度和应变，我们提出并在理论上证明了一种新颖的，据我们所知，开发基于长周期光纤光栅 (LPFG) 的固有不敏感生物传感器的方案。通过明智地调整纤芯掺杂剂及其浓度和 (ii) 在一个 LPFG 内部与另一个 LPFG 内部产生的应变诱导相变，固有地消除了 (i) 纤芯和包层模式的温度诱导相位，从而实现了不敏感性优化光栅参数（光栅周期、强度和长度）。由此产生的生物传感器具有超高的整体体积折射率灵敏度${\sim}3\;\unicode{x00B5} {\rm{m/RIU}}$对于生物样品（RI 在 1.33 到 1.34 RIU 范围内变化）和亲和灵敏度${\sim}1.4\;{\rm{nm/nm}}$用于生物分子（${\rm{RI}} \sim 1.45\;{\rm{RIU}}$）。我们的研究应该在开发超灵敏、高精度的生物/化学传感器方面得到应用，这些传感器本身就不受环境温度和应变变化的影响。