We demonstrate a compact interrogation method for resonance-based biosensors, based on an integrated photonic chip with an array of resonant-cavity enhanced photodetectors. Due to the high signal-to-noise ratio, wavelength shifts in the 10 pm range can be measured, orders of magnitude smaller than the sensor and interrogator linewidths. This approach allows the read-out of resonance-based optical biosensors with simple integrated components, potentially enabling compact and low-cost sensing systems for point-of-care diagnostics.
We demonstrate a novel paradigm for fiber sensing, based on the combination of an electrical sensor and a fiber-tip electro-optic metasurface. We transfer a semiconductor photodiode on the tip of an optical fiber and measure its current-voltage characteristics using an electro-optic photonic crystal. Any change in the electrical characteristics due to the environment can then be sensed via the fiber, greatly extending the application scope of fiber sensors. As a proof of principle, we demonstrate cryogenic temperature sensing.
Fiber-tip sensors have been used extensively for measuring chemical and physical parameters. Particularly, multimode fibers (MMF) tip sensors have become attractive since they open the possibility of using simple light-emitting diodes. While common techniques to fabricate MM fiber-tip sensors are labor-intensive, we developed a simple and controllable method to transfer large-area nanophotonic structures to the fiber end-face by mechanical contact, without using glue or micromanipulator. As proof of concept, a 2D photonic crystal (PhC) was successfully transferred to the tip of a multimode fiber, and its response to changes in refractive index was characterized, obtaining a sensitivity of 244 nm/RIU.
We investigate the possibility of probing the electrical status of a p-i-n junction via an optical fiber, without the need for electrical contacts. A photonic crystal with a resonance in the near-infrared is etched in a thin membrane of III-V semiconductor with an embedded p-i-n junction and placed on the cleaved facet of a fiber. We measure the effect of photoexcited carriers on the built-in voltage of the diode through the Pockels effect. This may enable the all-optical read-out of electrical signals from sensors in a distant or inaccessible environment.
Nano-optomechanical structures enable displacement and force sensing with ultimate precision, but their practical application is hindered by the complexity of the optical coupling. Here, we demonstrate that nano-optomechanical sensing can be realized on a fiber-tip without the use of any coupling optics. We use a photonic crystal optomechanical structure fabricated using standard wafer-scale processing. Afterwards the sensors are transferred on a fiber-tip using a simple pickup method. We demonstrate thermomechanical noise measurements with a high signal to noise ratio, using simple reflectance read-out via the fiber.
We developed a method to easily transfer optical structures from a semiconductor substrate to a fiber-tip facet without the need for glues and preserving the pristine or functionalized condition of the structure surface. An opening is etched on the back of the fabrication wafer and the structure is suspended via breakable support. The transfer is achieved by mechanical contact with the fiber facet. Using a photonic crystal structure designed for high vertical coupling at the Gamma point a reflectance fiber-tip sensor with refractive index sensitivity of 120 nm/RIU has been assembled and could be further functionalized for application in biosensing.
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