Broadband photonic-assisted microwave receiver with high cross-channel interference suppression and image rejection.

A broadband photonic-assisted microwave receiver with high cross-channel interference suppression and image rejection is proposed and experimentally demonstrated. At the input of the microwave receiver, a microwave signal is injected into an optoelectronic oscillator (OEO), which functions as a local oscillator (LO) to generate a low-phase noise LO signal as well as a photonic-assisted mixer to down-convert the input microwave signal to the intermediate frequency (IF). A microwave photonic filter (MPF), realized by the joint operation of a phase modulator (PM) in the OEO and a Fabry-Perot laser diode (FPLD), is used as a narrowband filter to select the IF signal. Thanks to the wide bandwidth of the photonic-assisted mixer and the wide frequency tunable range of the OEO, the microwave receiver can support broadband operation. The high cross-channel interference suppression and image rejection are enabled by the narrowband MPF. The system is evaluated experimentally. A broadband operation from 11.27 to 20.85 GHz is demonstrated. For a multi-channel microwave signal with a channel spacing of 2 GHz, a cross-channel interference suppression ratio of 21.95 dB and an image rejection ratio of 21.51 dB are realized. The spurious-free dynamic range (SFDR) of the receiver is also measured to be 98.25 dB·Hz2/3. The performance of the microwave receiver for multi-channel communications is also experimentally evaluated.

Nucleic acid hybridization on a plasmonic nanointerface of optical microfiber enables ultrahigh-sensitive detection and potential photothermal therapy.

Quantifying the microRNA (miRNA) level and manipulating them in complex samples, such as serum, is of intense interest because miRNAs are important diagnostic markers. Here, we demonstrate an optical microfiber integrating of untrasensitive detection function and local photothermal therapy potential. A nanointerface consisting of GO supported Cu2-xS nanoplates presented the localized surface plasmon resonance (LSPR) tuned to be consistent with the operation wavelength of the microfiber transducer. It enhanced the surface energy density of evanescent field, on which the miRNA sensing and therapy occurred. With evanescent field enhancement by the plasmonic nanointerface, the sensor exhibits an ultrahigh sensitivity for detecting microRNA at concentrations ranging from 0.1 aM to 10 pM. It is also capable of differentiating one-base mismatches of miRNA at ultralow concentrations (as low as 10 aM) in serum. The photothermal effect of nanointerface simultaneously endows the sensor with the potential for localized photothermal therapy. This work presents a possible approach for the in-situ integration of diagnosis and treatment in early stage.