The performance of bio-chemical sensing devices has been greatly improved by the development of surface plasmon resonance (SPR) based sensors. Advancements in micro- and nano-fabrication technologies have led to a variety of structures in SPR sensing systems being proposed. In this review, SPR sensors (from typical Kretschmann prism configurations to fiber sensor schemes) with micro- or nano-structures for local light field enhancement, extraordinary optical transmission, interference of surface plasmon waves, plasmonic cavities, etc. are discussed. We summarize and compare their performances and present guidelines for the design of SPR sensors.

In this paper, we report the highly-sensitive and -linear cryogenic temperature response of long-period fiber gratings (LPFGs) written on B–Ge-codoped photosensitive single-mode fiber. The resonance wavelength of the fabricated LPFG was monitored at a temperature range from 77 to 295 K. The temperature sensitivity of the resonance wavelength was measured as ~398 pm/K, which was higher than that of fiber grating sensors in a comparable cryogenic temperature range reported by other research groups. In particular, the linearity of the temperature response curve was very good (R² value of ~0.9979).

We propose a resonant optical Yagi-Uda nano-antenna fabricated at the end of the optical fiber probe for the sake of extracting the information of the angular directivity by absorption of directional emission as a subwavelength optical microscopy. A Yagi-Uda nano-antenna consists of a feed element surrounded by a reflector and three directors. The reflector and directors are optimized in pitches with regards to resonance of the antenna elements using the finiteelement method. We used a focused ion beam (FIB) to cut the end of the fiber probe tip away and make the flattened surface to mount the metal nano-antenna structure, followed by FIB platinum deposition patterning for the nano-antenna. To verify the characteristics of the probe based nano-antenna, directional emission from the metal slit with asymmetric metallic surface gratings is probed and detected using the photomultiplier tube. Our approach of the nano-antenna based fiber probe is suitable for scanning applications such as detection of directional emission.

Based on recent studies of our group, we will present various methods of plasmonic field enhancement and hotspot generation. Especially, we will focus on the potential of utilizing localization of propagating surface plasmon polaritons (SPPs) for the sensor applications. The advantage of using localization of propagating SPPs instead of using directly excited localized SPPs will be investigated.