In recent years, piezoelectric materials, such as AlN, lithium niobate (LN) and GaAs, are frequently applied to acoustooptic (AO) coupling interactions with great potentials. [16][17][18][19][20][21][22][23][24] With a travelling SAW actuated by the interdigital transducer (IDT), the optical waves in waveguides are scattered by the travelling refractive index gratings and frequencyshifted through Doppler effect. [25] The AO coupling in piezoelectric materials offers a promising way to implement on-chip AO modulation, microwave photonic filtering, acousto-optic frequency shift, and nonreciprocal light propagation. [16,17,26,27] Different from the intrinsic optomechanical interactions in waveguides, [28][29][30][31][32][33][34] it is unnecessary to design suspended waveguides or optomechanical cavities for the AO interactions, which guarantees the stability and feasibility for on-chip applications. [16,35] Meanwhile, the electrically driven AO interactions exhibit higher AO scattering efficiency than the intrinsic optomechanical interactions, which can be adjusted in both optical domain and electrical domain. [36,37] Although LN (d 33 = 6 pC N -1 ) is a good candidate in AO interactions for its outstanding optical and piezoelectric properties, [38] it is not compatible with complementary metal-oxide-semiconductor (CMOS) technology to achieve large-scale fabrication. [20][21][22] As for AlN, it is generally deposited on silicon substrate through magnetic sputtering that is compatible with CMOS technology, but it poses a challenge to design waveguide structures in AlN layer because of the smaller refractive index than silicon substrate. [17,18] Therefore, suspended waveguide structures are indispensable for AlN on silicon substrate to carry out AO interactions. Surprisingly, a nonsuspended structure of AlN deposited on silicon-on-insulator (SOI) platform with a SiO 2 interlayer had realized AO modulation recently, where the optical wave is mostly confined in the nonpiezoelectric silicon layer instead of AlN layer. [39] In that structure, the SAW actuated by the IDT propagates from AlN layer across SiO 2 interlayer and finally modulates the optical waves in the silicon waveguides, where the SiO 2 interlayer greatly increases the SAW propagation loss and degrades the acoustic performances. [40] At last, with the same CMOS-compatible deposition as AlN and better piezoelectric properties than AlN, Aluminum scandium nitride (AlScN) has attracted extensive attention for its excellent piezoelectric properties in the micro-electromechanical system applications. In this work, AlScN is demonstrated to be a promising candidate for on-chip acousto-optic coupling interactions with outstanding piezoelectric properties as well. Based on piezoelectric Al 0.6 Sc 0.4 N film deposited on silicon-on-insulator platform, the proposed devices exhibit impressive acousto-optic coupling performances over a short interaction length of 210 µm with surface acoustic waves actuated by interdigital transducers. Meanwhile, the acousto-optic coupling...

An ultra-sensitive colorimetric method to quantitate hundreds of polynucleotide molecules by gold nanoparticles with silver enhancement has been developed. The hybridization products from the target polynucleotides with biotin-labeled probes and gold nanoparticle-functioned oligonucleotides were immobilized to microplates via avidin-biotin system, and the absorbance signals of gold nanoparticles were amplified by silver enhance solution. This sandwich colorimetric assay can detect as few as 600 molecules for single-strand oligonucleotides and as few as 6000 molecules for double-strand polynucleotides in a 50 μL reaction system.

We propose and demonstrate an efficient grating coupler for integrated SiGe photonic devices. A bottom metal layer is adopted to enhance the coupling efficiency on the wafer backside. A low coupling loss of −1.34 dB and −0.79 dB can be theoretically obtained with optimal parameters for uniform and apodized grating couplers, respectively. The fabrication process is CMOS compatible without need of wafer bonding. The influence of fabrication errors on the coupling efficiency is analyzed in terms of substrate thickness, grating dimension and material refractive index. The results indicate a large tolerance for the deviations in practical fabrication. The measured coupling loss of the uniform grating is −2.7 dB at approximately 1465 nm with a 3 dB bandwidth of more than 40 nm. The proposed grating coupler provides a promising approach to realize efficient chip-fiber coupling for the SiGe photonic integration.