Integrated waveguide sensor utilizing organic photodiodes

We present a novel optical sensor platform, combining monolithically integrated ring‐like sensor waveguides together with ring‐shaped thin‐film organic photodiodes (OPDs) on one substrate. The OPDs serve as integrated light detectors, simplifying the detection system by minimizing the number of required optical components. The waveguide structures, including a means of coupling light in and out of the waveguides, serve as sensing elements. The functionality of the concept is demonstrated by an integrated carbon dioxide sensor, utilizing absorbance as sensing principle. The integrated optical sensor platform is suitable for the parallel detection of multiple parameters in a single sensor chip using sensor arrays. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thick junction broadband organic photodiodes

Inorganic semiconductor‐based broadband photodetectors are ubiquitous in imaging technologies such as digital cameras and photometers. Herein a broadband organic photodiode (OPD) that has performance metrics comparable or superior to inorganic photodiodes over the same spectral range is reported. The photodiode with an active layer comprised of a poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)]:[6,6]‐phenyl‐C₇₁‐butyric acid methyl ester bulk heterojunction blend had a dark current < 1 nA/cm², specific detectivity of ∼10¹³ Jones, reverse bias −3 dB frequency response of 100 kHz to 1 MHz, and state‐of‐the‐art Linear Dynamic Range for organic photodiodes of nine orders of magnitude (180 dB). The key to these performance metrics was the use of a thick junction (700 nm), which flattened the spectral response, reduced the dark current and decreased performance variations. The strategy also provides a route to large area defect free “monolithic” structures for low noise integrated photo‐sensing, position determination, or contact, non‐focal imaging.     

Integrated Si‐based nanoplasmonic sensor with phase‐sensitive angular interrogation

This work is related to the development of an integrated Surface Plasmon Resonance (SPR) sensor on silicon platform. The optical properties of metallic nanogratings fabricated on the semiconductor structure allow direct plasmonic detection in transmission mode. Specially designed angular interrogation method provides a periodic signal with phase dependent on the conditions of surface plasmon excitation. Proposed technique leads to sensitivity better than 10^?6 RIU for conventional SPR Kretschmann configuration and was tested on the integrated Si‐based nanoplasmonic chip. Developed concept is promising for low‐cost mono and multi ‐sensing applications by portable or stationary platforms.     

Electro‐optic Polymer Ring Resonator Modulator on a Flat Silicon‐on‐Insulator

Optical polymers are a promising material of choice in the development of hybrid silicon photonics devices. Particularly, recent progress in electro‐optic (EO) active polymers has shown a strong Pockels effect. A ring resonator modulator is a vital building block for practical applications, such as signal processing, routing, and monitoring. However, the properties of the hybrid silicon and EO polymer ring modulators are still far from their theoretical limits. Here, we demonstrate a unique design of a hybrid ring resonator modulator simply located onto a silicon‐on‐insulator (SOI) substrate. Extra doping and etching of the SOI wafer is not required, even so we measured an in‐device electro‐optic coefficient r₃₃ = 129 pm/V. The ring modulator exhibited a high sensitivity of the electrically tunable resonance, which enabled a 3 dB bandwidth of up to 18 GHz. The proposed technique will enable efficient mass‐production of the micro‐footprint modulators and promote the development of integrated silicon photonics.     

Controlling fluorescence emission with split‐ring‐resonator‐based plasmonic metasurfaces

Metasurfaces, which consist of resonant metamaterial elements in the form of two‐dimensional thin planar structures, retain great capabilities in manipulating electromagnetic wave and potential applications in modifying interaction with fluorescent molecules. The metasurfaces with magnetic responses are favorable to weakening fluorescence quenching while less investigated in controlling fluorescence. In this paper, we demonstrate control over fluorescence emission by engineering the magnetic and electric modes in plasmonic metasurfaces consisting of 45‐nm‐thick gold split‐ring‐resonators (SRRs). The fluorescence emission exhibits an enhancement factor of ∼18 and is predominantly x‐polarized with assistance of the magnetic mode excited by oblique incidence with an x‐polarized electric field. The magnetic and electric modes excited by oblique incidence with a y‐polarized electric field contribute to the rotation of emission polarization with respect to the incident polarization. The results demonstrate manipulating the interaction of fluorescent emitters with different resonant modes of the SRR‐based metasurface at the nanoscale by the polarization of incident light, providing potential applications of metasurfaces in a wide variety of areas, including optical nanosources, fluorescence spectroscopy and compact biosensors.

     

基于十字连通形环形谐振腔金属-介质-金属波导的折射率传感器和滤波器

提出了由十字连通形环形谐振腔耦合两个金属-介质-金属(metal-insulator-metal, MIM)波导的结构,并用有限元法数值研究了表面等离极化激元在结构中的传输特性.通过对透射谱的研究,系统地分析了MIM结构的传感特性.结果表明,在透射光谱中有三个共振峰,即存在三种共振模式,其中透射峰与材料的折射率呈线性关系.通过对结构参数的优化,得到了折射率灵敏度(S)高达1500 nm/RIU的理论值,相应的传感分辨率为1.33×10~(-4)RIU.更重要的是,灵敏度不受结构参数变化的影响,这意味着传感器的灵敏度不受制造偏差的影响.此外,谐振波长与环形腔中心半径成线性关系,该器件在较大波长范围内实现可调谐带通滤波.透射强度随着波导与环形腔间距的增大而减小,透射带宽同时减小,因此,可以通过控制环形腔与波导的耦合距离来调谐透射强度及透射带宽.研究结果对高灵敏度纳米级折射率传感器和带通滤波器的设计以及在生物传感器方面的应用都具有一定的指导意义.     

Fast piezoresistive sensor and UV photodetector based on Mn‐doped ZnO nanorods

A low cost hydrothermal synthesis method to synthesize Mn‐doped ZnO nanorods (NRs) with controllable morphology and structure has been developed. Ammonia is used to tailor the ammonium hydroxide concentration, which provides a source of OH^– for hydrolysis and precipitation during the growth instead of HMT. The morphological, chemical composition, structural, and electronic structure studies of the Mn‐doped ZnO NRs show that the Mn‐doped ZnO NRs have a hexagonal wurtzite ZnO structure along the c‐axis and the Mn ions replace the Zn sites in the ZnO NRs matrix without any secondary phase of metallic manganese element and manganese oxides observed. The fabricated PEDOT:PSS/Zn_0.85Mn_0.15O Schottky diode based piezoresistive sensor and UV photodetector shows that the piezoresistive sensor has pressure sensitivity of 0.00617 kPa^–1 for the pressure range from 1 kPa to 20 kP and 0.000180 kPa^–1for the pressure range from 20 kPa to 320 kPa with relatively fast response time of 0.03 s and the UV photodetector has both relatively high responsivity and fast response time of 0.065 A/W and 2.75 s, respectively. The fabricated Schottky diode can be utilized as a very useful human‐friendly interactive electronic device for mass/force sensor or UV photodetector in everyday living life. This developed device is very promising for small‐size, low‐cost and easy‐to‐customize application‐specific requirements. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Random lasing in an organic light‐emitting crystal and its interplay with vertical cavity feedback

The simultaneous vertical‐cavity and random lasing emission properties of a blue‐emitting molecular crystal are investigated. The 1,1,4,4‐tetraphenyl‐1,3‐butadiene samples, grown by physical vapour transport, feature room‐temperature stimulated emission peaked at about 430 nm. Fabry‐Pérot and random resonances are primed by the interfaces of the crystal with external media and by defect scatterers, respectively. The analysis of the resulting lasing spectra evidences the existence of narrow peaks due to both the built‐in vertical Fabry‐Pérot cavity and random lasing in a novel, surface‐emitting configuration and threshold around 500 μJ cm⁻². The anti‐correlation between different modes is also highlighted, due to competition for gain. Molecular crystals with optical gain candidate as promising photonic media inherently supporting multiple lasing mechanisms.     

Synchrotron fluorescence nanoimaging of a single Co‐implanted ZnO nanowire

In this study, we report the application of synchrotron radiation nanoprobe technique to the elemental analysis of single as‐grown and Co‐implanted ZnO nanowires. The nano‐X‐ray fluorescence technique enabled us not only to examine the spatial variation of Zn and Co elements, but also to disregard the presence of residual impurities in the nanowires, as well as the detection of Fe and Sn residual impurities in the substrates. Our observations provide strong evidence for the overall elemental uniformity of Zn and Co along the wires, without clustering or segregation effects. Within the nanoprobe spatial resolution, our findings indicate a Co localization within thicker irregularities observed with scanning electron microscopy. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A magnetoelectric laminate based passive micro‐displacement sensor

A passive micro‐displacement sensor (for ～μm displacement) was fabricated based on a magnetoelectric laminate, in which the displacement change can result in a change of the magnetic flux around the magnetoelectric sensor. The displacement measurement was realized by measuring the magnetoelectric output voltage. The displacement detecting coefficient was ～2.5 mV/μm at a frequency of ～1 kHz. This passive displacement sensor possesses the advantages of low cost, high resolution, low energy consumption and good linearity and has potential for application in future displacement detectors.

     

Methodological challenges of optical tweezers‐based X‐ray fluorescence imaging of biological model organisms at synchrotron facilities

Recently, a radically new synchrotron radiation‐based elemental imaging approach for the analysis of biological model organisms and single cells in their natural in vivo state was introduced. The methodology combines optical tweezers (OT) technology for non‐contact laser‐based sample manipulation with synchrotron radiation confocal X‐ray fluorescence (XRF) microimaging for the first time at ESRF‐ID13. The optical manipulation possibilities and limitations of biological model organisms, the OT setup developments for XRF imaging and the confocal XRF‐related challenges are reported. In general, the applicability of the OT‐based setup is extended with the aim of introducing the OT XRF methodology in all research fields where highly sensitive in vivo multi‐elemental analysis is of relevance at the (sub)micrometre spatial resolution level.     

Integrated all‐optical switch with 10 ps time resolution enabled by ALD

Abstract The potential of GaAs‐based photonic crystals for fast all‐optical switching in the telecom spectral range is exploited by controlling the surface recombination and, thereby, the carrier relaxation dynamics. The structure is entirely coated with a layer of aluminium oxide using atomic layer deposition. This results in a carrier lifetime of about 10 ps, as determined by spectrally resolved pump–probe measurements. We show that the nonlinear response of the resonator is optimized when it is excited with a few‐picoseconds pulse. This dynamics is perfectly captured by our model accounting for the carrier diffusion with an impulse response function. Moreover, the suppression of photo‐induced oxidation is revealed to be crucial to demonstrate all‐optical operation at GHz rates with average coupled pump power of 0.5 mW (hence 100 fJ/bit). The switching window is 12 ps wide (1/e), as resolved by homodyne pump–probe measurements. The devices respond to a sequence of closely spaced pump pulses demonstrating a gating window close to 10 ps, with a contrast as high as 7 dB.

     

Energy yield of fluorescence of complex organic compounds upon electron excitation

With use of electron energy loss spectra for vapors of anthracene, perylene, 1,4[di(2,5-phenyloxazolyl)] benzene, and paratherphenyl the energy yields of fluorescence are calculated for electron collision. It is shown that they are considerably smaller than those for optical excitation conditions. Deceased Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 146–148, January–February, 1998.     

Single and networked CuO nanowires for highly sensitive p‐type semiconductor gas sensor applications

Development of high‐performance p‐type semiconductor based gas sensors exhibiting fast‐response/recovery times with ultra‐high response are of major importance for gas sensing applications. Recent reports demonstrated the excellent properties of p‐type semiconducting oxide for various practical applications, especially for selective oxidation of volatile organic compounds (VOCs). In this work, sensors based on CuO nanowire (NW) networks have been successfully fabricated via a simple thermal oxidation process on pre‐patterned Au/Cr pads. Our investigation demonstrates high impact of the process temperature on aspect ratio and density of copper oxide NWs. An optimal temperature for growth of thin and densely packed NWs was found to be at 425 °C. The fabricated sensors demonstrated ultra‐high gas response by a factor of 313 to ethanol vapour (100 ppm) at an operating temperature of 250 °C. High stability and repeatability of these sensors indicate the efficiency of p‐type oxide based gas sensors for selective detection of VOCs. A high‐performance nanodevice was fabricated in a FIB‐SEM system using a single CuO NW, demonstrating an ethanol response of 202 and rapid response and recovery of ～198 ms at room temperature. The involved gas sensing mechanism of CuO NW networks has been described. We consider that the presented results will be of a great interest for the development of higher‐performance p‐type semiconductor based sensors and bottom‐up nanotechnologies. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

基于荧光分析的氨基甲酸酯类农药残留检测系统

通过对氨基甲酸酯类农药在紫外光照射下能够产生荧光的机理研究,设计了一种用于检测氨基甲酸酯类农药残留的荧光系统。该系统采用单光源、双光路结构,能够对测量信号和参考信号同时进行处理。采用所设计的筒式光纤探头激发并探测荧光,设计了相应的信号处理电路,实现了计算机管理。利用该系统和稳态光谱仪对西维因进行了对比实验。结果表明:在激发波长为319nm、荧光波长为654nm时,最小检测浓度为5×10-7μg/L。当西维因浓度范围在0.0～120.0μg/L之间时,系统具有较好的线性关系,线性相关系数r=0.9996(信噪比S/N=5)。该系统达到了荧光检测的指标。     

Reconstruction of parameters of an adlayer on the surface of a channel optical waveguide

A simple solution of an inverse problem of reconstruction of thickness, permittivity and surface coverage of an adlayer disposed on the surface of a channel optical waveguide is proposed and substantiated theoretically. It is shown that the reconstruction errors for the parameters of the adlayer can be minimized by a choice of the channel waveguide parameters. The application of the procedure to biochemical sensors is considered.     

Fiber‐optic sensor active networking with distributed erbium‐doped fiber and Raman amplification

This work is meant to provide a review of different multiplexing topologies employing distributed erbium‐doped fiber and Raman amplification to solve the problem of power‐loss compensation in fiber‐optic sensor (FOS) networks. This is a key parameter in large multiplexing networks, particularly when employing intensity‐modulated sensors. These topologies are studied both theoretically and experimentally, and a comparative analysis is carried out between them. The main parameters considered in the analysis are power budget, optical signal‐to‐noise ratios, scalability and architecture complexity.     

Sensitivity‐enhancement methods for surface plasmon sensors

Surface plasmon resonance (SPR) sensors have been a mature technology for more than two decades now, however, recent investigations show continuous enhancement of their sensitivity and their lower detection limit. Together with the recent investigations in localized SPR phenomena, extraordinary optical transmission through nanoapertures in metals, and surface‐enhanced spectroscopies, drastic developments are expected to revolutionize the field of optical biosensing. Sensitivity‐enhancement (SE) techniques are reviewed focusing both on the physical transduction mechanisms and the system performance. In the majority of cases the SE is associated with the enhancement of the electromagnetic field overlap integral describing the interaction energy within the analyte. Other important mechanisms are the interaction between plasmons and excitons and between the analyte molecules and the metal surface. The lower detection limit can be reduced significantly if systems with high signal‐to‐noise ratio are used such as common‐path interferometry, ellipsometry or polarimetry systems.