Metasurface analogue of the phenomenon of electromagnetically induced transparency (EIT) that is originally observed in atomic gases offers diverse applications for new photonic components such as nonlinear optical units, slow-light devices, and biosensors. The development of functional integrated photonic devices requires an active control of EIT in metasurfaces. We demonstrate a reversible switching of the metasurface-induced transparency in the near-infrared region by incorporating a nonvolatile phase change material, Ge2Sb2Te5, into the metasurface design. This leads to an ultrafast reconfigurable transparency window under an excitation of a nanosecond pulsed laser. The measurement agrees well with both theoretical calculation and finite-difference time-domain numerical simulation. Our work paves the way for dynamic metasurface devices such as reconfigurable slow light and biosensing.
In this work, we extend the scope of the metallic and dielectric states by treating a pure metal or dielectric as the limiting case of a metal-dielectric layered metamaterial. The metamaterial with metal filling ratio larger than one-half shares the same topological invariant as a pure metal and thus exhibits some metallic behaviors. In contrast, the dielectric-rich metamaterial and a pure dielectric are topologically equivalent and display dielectric properties. This new understanding gives surface plasmon polariton (SPP) at a metal/dielectric interface a new physical meaning: the limiting case of a topological edge state. Finally, a complex structure also supports hidden topological effects if it is transformed from a layered metamaterial possessing an edge state.
We study the polarisation and geometry dependence of four-wave mixing (FWM) on nanocross arrays. The arrays are composed of gold meta-atoms fabricated via EBL and lift-off on a glass substrate coated with a 15 nm ITO film. The individual nanocrosses are C4-symmetric, 360 nm by 360 nm, with 80 nm wide arms. The array period is 550 nm.
FWM is generated by two-colour illumination. The two input wavelengths are 1028 nm (wavelength 1) and 1310 nm (wavelength 2), and we look for the degenerate FWM signal at 846 nm (2*frequency 1 - frequency 2). Using all combinations of handedness for circularly polarised inputs, we verify the theoretical selection rules for FWM on systems of this type. They are LLL-L, RRR-R, LRR-L, and RLL-R, where the first letter is the handedness of beam 2, the following two are the handedness of beam 1, and the last letter is the handedness of the output FWM.
We measure several metasurfaces. In each, the two nanocrosses in a unit cell are rotated towards each other by an angle theta, which is varied 0 to 45 degrees in 7.5 degree increments. With co-polarised inputs (LLL and RRR) the FWM signal is the same from all metasurfaces. With cross-polarised inputs (LRR and RLL) it follows cos^2(4*theta). This behaviour, which is predicted theoretically, is due to the nonlinear Pancharatnam-Berry geometric phase of the FWM from the rotated nanocrosses.
We further support our results with numerical simulations, which match the experimental behaviour for all metasurfaces and show the angle-dependent phase of the nonlinear polarisations on the meta-atoms.
The emerging field of metasurfaces has offered unprecedented functionalities for shaping wave fronts and optical responses. Here, we realize a new class of metasurfaces with nanorod array, which can generate abrupt interfacial phase changes to control local wave front at subwavelength scale. The physical mechanism under the phase modulation is geometry phase in essence, thus can achieve broadband operation, as well as helicity-dependent property. Multiple applications have been demonstrated, such as anomalous refraction, ultrathin dual-polarity metalenses, helicitydependent unidirectional surface plasmon polariton (SPP) excitation, and three-dimensional (3D) holography.
In this paper, a testing and analyzing system for volt-current and optic-power characteristics of semiconductor laser
diodes (LDs) based on virtual instrumentation is designed and developed by using PCI-6014 DAQ. The design methods
of hardware circuit and software for NI-DAQ are introduced. Some protective methods to LDs, such as driving current
limit, avoiding electrical pulse and delay start-up etc. problems, are completely finished by the software, instead of
mostly considering the resolvent on hardware circuits. The detailed tested data for the function and performance of the
system is presented, and the every tested data of LDs indicates that the whole system is of excellent performance and
stability to obtain the parameters of LDs.
KEYWORDS: Sensors, Short wave infrared radiation, Photodetectors, Picosecond phenomena, Single photon detectors, Absorption, Infrared radiation, Signal to noise ratio, Temperature metrology, Infrared imaging
A novel short wave infrared single photon detector was conceived for wavelengths beyond 1 μm. The detector, called the nano-injection photon detector, is conceptually designed with biological inspirations taken from the eye. Based on a detection process similar to the human visual system, the detector couples a nano-scale sensory region with a large absorption volume to provide a low-noise internal amplification mechanism, high signal-to-noise ratio and quantum efficiency. Tens of thousands of devices were fabricated in different configurations with conventional processing methods in more than 20 iterations. For low speed imaging applications, the detectors have shown gain values reaching 10,000 with bias voltages around 1 V. Ultra-low noise levels were measured at gain values exceeding 4,000 at room temperature: Fano factors as low as 0.55 has been achieved, which indicated a statistically stable amplification mechanism and resulting sub-Poissionian shot noise. An alternate version of the detector, which is specialized towards high-speed applications, has also been developed with slight changes in processing steps. The fast detectors with bandwidth beyond 3 Ghz were demonstrated which provide gain values around 20. The measured risetime was less than 200 ps. Femtosecond pulsed illumination measurements exhibited ultra-low jitter around 15 ps. Transient delay experiments revealed that the measured jitter is due to the transit time in the large absorption region. Hence the amplification process has insignificant time-uncertainty in addition to low amplitude-variance (noise), which is consistent with statistically stable nature of amplification.
The shooting range test is an important field in modern weapon development. The modern weaponry is developing towards long distance and automation directions, therefore the shooting range test is put forward new higher requirements. A novel method of target detection based on the digital image processing technology is proposed in the paper. Experiments indicate the strategy is fit to the request of the dynamic target detection and tracking in the shooting range.
The method of screening semiconductor lasers by using electrical derivative technique is described in detail. The nonlinear diffusion equation is applied to denoising of electrical derivative data according to its denoising theory in signal processing. The denoising experiments of electrical derivative data for several dozens semiconductor lasers indicate that the denoising method can effectively reduce the noise in electrical derivative data and the errors of the measured parameters. The farther experiments indicate that the accurate estimate ratio of the devices can be effectively increased by using the measured parameters which have been denoised, to estimate the quality and reliability of semiconductor lasers.
TiO2 and Mn0.2Ti0.8O2thin films were prepared by sol-gel process and their structural and optical properties were examined. The structural properties of samples were investigated by the X-ray diffraction (XRD) and auto force microscope (AFM). The XRD results showed that TiO2 thin film calcined at 650°C was anatase phase, and Mn0.2Ti0.8O2 thin films calcined at the same temperature was rutile. The AFM results of both samples showed quite a smooth surface. Optical properties of samples were examined by UV absorption spectrum. The absorption edge of Mn0.2Ti0.8O2 red-shifted.
The variable optical attenuator (VOA) has played very important roles in wavelength division multiplexed (WDM) systems, it is an essential optical component aimed to continuously adjust the optical power transmitting in optical networks. In this paper, we began to study a new type of variable optical attenuator using polymer liquid crystal material. We hanged the liquid crystal technologies and MEMS technologies together to design variable optical attenuator. This paper describes the methods and process of the preparation of polymer liquid crystal material, presents some experimental results obtained in laboratory.
TiO2 thin films were prepared at various calcinations temperatures by sol-gel process and their structural and optical properties were examined. The influence of calcinations temperature on the structural properties of the prepared TiO2 thin films was investigated by the X-ray diffraction (XRD) and atomic force microscope (AFM). The XRD results showed that TiO2 thin film was transformed into the anatase phase at 350°C, and further into rutile phase at 850°C. The AFM results show quite a smooth surface and are in reasonably well agreement with the crystallite sizes estimated by XRD peak broadening. The influence of calcinations temperature on the optical properties of the prepared TiO2 thin films was investigated by UV-Vis spectrum and variable angle incidence spectroscopic ellipsometer (VASE). The results showed the both anatase phase and rutile phase of the TiO2 thin films prepared have good optical properties in UV region.
Indium tin oxide (ITO) films as transparent conductors have caused a great deal of interest due to their prominent electro-optical behavior. This paper describes a study of the properties of ITO thin films that are used for a new type variable optical attenuator using polymer network liquid crystal (PNLC). The mechanism of PNLC optical attenuator operation is that the light from the input fiber is scattered when no voltage is applied, and the light passes through the attenuator when sufficient voltage is applied. So the ITO thin films can provide transparent electrodes for PNLC. They were deposited under various preparation conditions using the radio-frequency (rf) magnetron sputtering technique. Here discuss the results of the structural, electrical and optical properties of the ITO films. The paper presents some experimental results obtained in laboratory.
Micromechanical optical switch has a good quality for free-space optical cross connects, particularly in terms of the low insertion loss, low crosstalk, low polarization dependent loss (PDL), wavelength-independence, and bit-rate transparency. In research of micromechanical optical switches, the electrostatic torsion beam actuator is widely used. But this actuator needs high-applied voltage. In this paper, the actuator with the slant counter electrode was proposed and fabricated with tilted 3° (111) silicon wafer.
The optical variable attenuators (VOA) play important roles in wavelength division multiplexing (WDM) transmutation systems, this paper describes a new type variable optical attenuator made by using fiber U-grooves in silicon wafer and polymer-network liquid crystal. Fibers are placed in the U-grooves of silicon wafer, and the
polymer-network liquid crystal is filled in the gaps between the ends of the docking fibers. The paper explains the principle of the attenuator operation and presents experimental method in laboratory.
In order to achieve controlled degree of intermixing in selected areas (CISA), SiO2 gratings are checked first to be able to influence the degree of intermixing during high-temperature rapid thermal annealing of InGaAs/GaAs quantum wells. Subsequently, SiO2/MgF2 gratings with different periods are used to cover different parts of MWQ sample and found to be suitable for achieving CISA after only a single annealing procedure.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.