Optical resonator-based ultrasound detection plays a significant role in the modern ultrasonography. It consists of two steps including the optical readout of the acoustic wave signal and the electrical demodulation of the acoustic response. In this paper, we conduct innovative researches on both of them for improved performance. High quality-factor (Q-factor) chalcogenide glass (ChG) microdisk and microring resonators as optical readout configurations are designed and fabricated. High-precision digital optical frequency comb (DOFC) technique is proposed to monitor the minor resonance frequency shift. The sensitivity up to 2.86 dB/Pa and noise equivalent pressure (NEP) down to 4 Pa are obtained under the 40 KHz ultrasound vibration using a 100-μm radius ${\rm{Ge_{11.5} A_{s24}Se_{64.5}}}$ microdisk resonator with the Q-factor of ${11.5\times10^{6}}$ . As a proof-of-concept, three cascaded ${\rm{SiN_{x}}}$ microring resonators-based ultrasound detector is fabricated and characterized to further validate the versatility of DOFC in the arrayed microcavities. Successful realization of the threedimensional ultrasound detection paves the way to the development of high-performance photoacoustic imaging.

1. The aim was to employ real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) technology (TaqMan ®) to examine the induction of some selected cytochrome P450 (CYP) forms in precision-cut rat liver slices. 2. Taqman ® primers and probe sets were developed for rat CYP1A1, CYP1A2, CYP2B1 and CYP4A1 forms. 3. Rat liver slices were cultured in control medium or medium containing either 10 µg ml -1 Aroclor 1254 (ARO), 500µM sodium phenobarbitone (NaPB) or 50µM Wy-14,643 (WY) for 3, 6 and 24 h. 4. Compared with control liver slices, treatment with ARO for 3 and 6 h produced 24- and 184-fold increases, respectively, in CYP1A1 mRNA levels, and after 24h produced an 85-fold increase in CYP1A2 mRNA levels. Levels of CYP1A1 and CYP1A2 mRNA were not markedly affected by NaPB and WY. 5. Treatment with ARO and PB for 24 h produced 10.6- and 23.8-fold increases, respectively, in CYP2B1 mRNA. Levels of CYP2B1 mRNA were not markedly affected by WY. 6. Treatment with WY, but not ARO and NaPB, for 24h produced a 20.4-fold increase in levels of CYP4A1 mRNA. 7. These results demonstrate that cultured liver slices may be used to evaluate the effect of xenobiotics on CYP form mRNA levels.

On-chip waveguide-integrated suspended microcavity resonator as a good sensing element is constantly pursued combining with the advantages of an optical material to enhance device performance. In this work, low-loss waveguide-integrated suspended Ge $_11.5$ As $_24$ Se $_64.5$ microdisk resonators have been successfully demonstrated using an optimized etching recipe. The realization of propagation loss down to 0.48 dB/cm verifies the low-loss characteristic of chalcogenide glass rectangular waveguide. An optical loaded quality factor of 1.1×10 $^6$ for the no suspended microdisk resonator, approaching to the highest figure (1.2×10 $^6$ ) so far reported in planar chalcogenide optical devices, is obtained experimentally to reveal the natural evolution of high quality chalcogenide glass membrane thermally evaporated into an oxidized silicon wafer during the engineering of shallow suspension configuration. By comparing with the scattering loss of mode in no suspended case, the contributions of bottom roughness scattering to the optical losses increase exceeding 50% in the shallowly suspended counterparts. The development of waveguide-integrated suspended chalcogenide glass microdisk resonator is expected to enhance the interactional abilities in applications of the gas sensing and ultrasound detection.

In this letter, a resolution enhancement and signal-to-noise ratio (SNR) improvement scheme for digital optical frequency comb (DOFC)-based Brillouin optical time-domain analysis (BOTDA) ultrafast distributed sensing employing a pump pulse array is proposed. Based on the properties of the time-invariant linear system and the cyclic revolution theorem, experimental results indicate that its spatial resolution reaches 10.24 m while the frequency uncertainty is below 2 MHz over a 9.5 km fiber. Moreover, the response time is only 209.6 μs and the temperature measurement error is less than 0.52 °C.

Optical fiber sensing (OFS) systems can be used to accurately measure temperature, strain, pressure and other physical parameters by detecting the change in the field of lightwave. As they are used in more application areas, a new type of OFS with the ability of multi-dimensional, highly sensitive, ultra-fine and real-time measurement is necessary. This is possible with the application of digital coherent optical technologies in the OFS systems. In this paper, we show that many aspects of OFS systems can be replaced or updated by digital coherent optical technologies. For example, digital optical frequency comb (DOFC) can replace the sweeping laser source, and the digital coherent optical receiver can simultaneously detect all the dimensions of lightwave signal. Based on these techniques, we present our research progresses on OFS with multi-dimensional, real-time, ultra-fine spectral analysis and single-shot Brillouin optical time-domain analysis based DOFC for distributed OFS. We show that the OFS systems can be bought to a whole new level with the capabilities of real-time time-frequency analysis, ultra-fine spectral resolution and ultra-low sensitivity. Opportunities and challenges of using digital coherent optical technologies in OFS systems are also discussed.