Standard Mirror Research Articles

Near-field characterization of Bragg mirrors engraved in surface plasmon waveguides

Surface plasmon waveguides (SPW's) are metal ridges featuring widths in the micrometer range and thicknesses of a few tens of nanometers. A focused ion beam has been used to carve microscatterers into gold SPW's and the near-field distributions around these microstructures are observed by means of photon scanning tunneling microscopy (PSTM). On the basis of near-field images, we show that a finite length periodic arrangement of narrow slits can reflect a surface plasmon mode propagating along a SPW. The reflection efficiency of the micrograting is found to depend upon the number of slits, the period of the grating, and the incident wavelength. The optimum reflection efficiency is obtained for a period of the micrograting equal to half the incident wavelength in vacuum. The PSTM images of the plasmon mirrors taken at different wavelengths allow us to measure the experimental dispersion curve of the SPW in the near-infrared. From this dispersion curve, we found that, in analogy with a surface plasmon (SP) excited on extended thin films, the group velocity of a SPW mode is close to the speed of light. For a given frequency in the near-infrared, the effective index of the SP mode supported by a $2.5\text{\penalty1000-\hskip0pt}\ensuremath{\mu}\mathrm{m}$-wide SPW is also found to be significantly larger than the effective index of an extended thin film SP. Finally, we show that the optical properties of microgratings engraved into a SPW can be qualitatively approached by a standard Bragg mirror model.

Laser Mode Locking Using a Saturable Absorber Incorporating Carbon Nanotubes

This paper describes a new class of saturable absorber device based on single-wall carbon nanotube (SWNT)-the saturable absorber incorporating nano tube (SAINT). The device possesses ultrafast optical properties comparable to that of the industrial standard semiconductor saturable absorber mirror (SESAM). Passively mode-locked picosecond fiber lasers in different configurations are demonstrated using SAINTs as mode lockers. This is the first demonstration of optical pulsed lasers based on the carbon nanotube technology, and the first practical application of carbon nanotubes in the field of applied optics.

Ray chaos in optical cavities based upon standard laser mirrors

We present a composite optical cavity made of standard laser mirrors; the cavity consists of a suitable combination of stable and unstable cavities. In spite of its very open nature the composite cavity shows ray chaos, which may be either soft or hard, depending on the cavity configuration. This opens a convenient route for experimental studies of the quantum aspects of a chaotic wave field.

Proposal for enhanced spatial resolution and efficiency of a fast-neutron scintillator detector by use of a parabolic mirror

The limitation on the detector efficiency due to the required spatial resolution of a fast-neutron imaging system is known as the detector problem. Here, this problem is described and a proposal for a novel fast-neutron imaging system is given to overcome this problem. The novelty is to replace the standard flat mirror in an imaging system by a parabolic mirror with its focal point at the fast-neutron source position. The spatial resolution will only be limited by the intrinsic resolution of the scintillator of the order of 0.06mm. The intrinsic fast-neutron detection efficiency can be increased to about 20–30% without loss of spatial resolution.

High extinction ratio Mach–Zehnder interferometer filter and implementation of single-channel optical switch

A novel structure of high extinction ratio filter based on a Mach–Zehnder (M–Z) interferometer and a standard single-mode fiber loop mirror (SMFLM) is proposed for the first to our knowledge. The numerical simulation and experimental results show that the extinction ratio can be improved greatly in comparison with the conventional M–Z interferometer in the same parameters. The improvement of the extinction ratio depends on mainly the difference between the two arms and the measuring resolution. A single-channel optical switch is also demonstrated by using a fiber Bragg grating (FBG) instead of the SMFLM. The dynamic range of greater than 37.4 dB at wavelength-selective port is obtained.

Leveraged current mirror op amp

A small change to the standard current mirror op amp configuration is shown to improve performance, with few, if any, disadvantages. Adding a pair of fixed current sources allows reduced operating-point current in the output stage, while the resulting "leveraging" effect increases slew rate. For equal total power dissipation, the new configuration improves DC gain and gain-bandwidth (GBW) over conventional current-mirror and folded cascode op amps, as shown by hand analyses and SPICE simulations. Also, because of increased input stage transconductance, the new configuration reduces thermal and flicker noise.

Spatially coherent radiation from a coaxial free-electron laser with a resonator composed of one-dimensional and two-dimensional Bragg mirrors

It is shown that the application of a resonator composed of one-dimensional and two-dimensional coaxial Bragg mirrors provides a spatially coherent radiation from a hollow electron beam with a transverse size several orders of magnitude larger than the wavelength. The two-dimensional Bragg mirror placed at the cathodic end of the resonator synchronizes the radiation across the hollow electron beam. The standard one-dimensional Bragg mirror placed at the collector end closes the feedback loop and reduces ohmic losses to as low as 5–10% of the lasing power.

Standard X-ray mirror systems for SPring-8 beamlines

More than 20 X-ray mirror systems have been constructed in the SPring-8 beamlines since 1997. To simplify the design and reduce the construction, alignment, and maintenance time, the X-ray mirror systems have been standardized as far as possible. An overview of the design, alignment method, and performance of the standard X-ray mirror systems in SPring-8 is given here.

Phase-locking and self-imaging properties of a Talbot resonator applied to circular structures

The geometry of diode-pumped high power multicore fiber (MCF) lasers is characterized by many individual laser emitters (microcores) placed on a ring inside a large pump core. These microcores form a circular laser array. The circular geometry leads to a quite different behavior compared to linear arrays when a Talbot resonator is used for phase-locking. We investigate analytically and numerically phase-locking and self-imaging properties of a Talbot resonator applied to a MCF. Phase-locking of a MCF in a Talbot cavity is demonstrated in the experiment by using a standard mirror with uniform reflectivity.

The Use of Mirrors during an Assembly Task: A Study of Ergonomics and Productivity

Assembly jobs often require sustained, awkward neck and/or shoulder postures. It has been shown in previous studies that these postures increase musculoskeletal discomfort and can impact long-term productivity. The aim of this study was to investigate the effects of ergonomic interventions designed to eliminate these awkward postures. Subjects used a cordless screwdriver to drive screws into a pre-tapped aluminum block, simulating a simple assembly task. Four distinct assembly postures were tested: standard industry (in-line screwdriver, work at elbow height, no visual aid), pistol grip (pistol grip screwdriver, work at shoulder height, no visual aid), mirror (in-line screwdriver, work at elbow height, single mirror visual aid) and periscope (in-line screwdriver, work at elbow height, two mirror visual aids). Each was performed for fifteen minutes. Muscular activity, discomfort, postural deviation from neutral, productivity, and operator subjective assessment were recorded to determine the effects of the interventions. Both interventions (mirror and periscope) resulted in lower muscle activity, smaller postural deviations from neutral and lower subjective discomfort levels. Productivity, however, was highest in the standard industry posture followed by the pistol grip (9% lower), the periscope (13% lower) and the mirror posture (23% lower).

Measurement of nonlinear polarization rotation in a highly birefringent optical fibre using a Faraday mirror

We present both a theoretical and experimental analysis of nonlinear polarization rotation in an optical fibre. Starting from the coupled nonlinear Schrodinger equations an analytical solution for the evolution of the state of polarization, valid for fibres with large linear birefringence and quasi cw input light with arbitrary polarization, is given. It allows us to model straightforwardly go-and-return paths as in interferometers with standard or Faraday mirrors. In the experiment all the fluctuations in the linear birefringence, including temperature- and pressure-induced ones, are successfully removed in a passive way by using a double pass of the fibre under test with a Faraday mirror at the end of the fibre. This allows us to use long fibres and relatively low input powers. The match between the experimental data and our model is excellent, except at higher intensities where deviations due to modulation instability start to appear.

Soliton and quasi-soliton switching in nonlinear optical loop mirror constructed from dispersion decreasing fiber

The performance of a standard nonlinear optical loop mirror (NOLM) device and the NOLM constructed with a dispersion decreasing fiber (DDF) operating in the soliton and quasi-soliton regime is investigated numerically. Results showed that the soliton regime present best behavior when compared with the quasi-soliton regime. One concludes that operating the NOLM in the soliton regime, the first, second and third transmission maxim could be obtained with low pump power compared with the quasi-soliton regime. It was also observed that in the basic NOLM device, the output pulse duration is very dependent on length of the fiber. In the quasi-soliton regime, the transmitted pulse present strong shaping effects (compression). However, in the soliton regime, the transmitted pulses present fewer fluctuations in the time duration with pump power. The output pulse duration present more stability with a bigger time duration ( C=0.6). Our simulations considering four different profiles, linear, hyperbolic, exponential and Gaussian conclude that, on average, the hyperbolic profile gives the lowest pump power for the first, second and third transmission peaks of transmission compared with the other profiles. The Gaussian profile presents the worse behavior. It was also observed that with a proper choice of the dispersion profile we could have a transmitted pulse with no distortion in the soliton regime. For the quasi-soliton regime, strong compression was observed.

Ultrafast Optical Switching in a Nonlinear Loop Mirror Constructed from Dispersion Decreasing Fiber

The performance of a standard nonlinear optical loop mirror (NOLM) device and the NOLM constructed with a dispersion decreasing fiber (DDF) operating in the soliton and quasi-soliton regime is investigated numerically. Results showed that the soliton regime present best behavior when compared with the quasi soliton regime. One concludes that operating the NOLM in the soliton regime, the first, second and third transmission maxim could be obtained with low pump power compared with the quasi-soliton regime. It was also observed that in the basic NOLM device, the output pulse duration is very dependent on length of the fiber. In the quasi-soliton regime, the transmitted pulse present strong shaping effects (compression). However in the soliton regime, the transmitted pulses present fewer fluctuations in the compression factor with the pump power. The output pulse duration is more stable with a bigger time duration (C = 0.6). Our simulations considering constant and linear profile conclude that it is possible to have, in the soliton regime, the NOLM operating with no time distortion in the transmitted pulse. For the quasi-soliton regime, strong compression was observed. Our results suggest that the decrease of the final value of dispersion profile lead to strong pulse compression of the transmitted pulse.

Dispersion-imbalanced nonlinear optical loop mirrorwith lumped dispersive elements

Self switching of optical pulses by a dispersion-imbalanced nonlinear optical fibre loop mirror is analysed. The loop mirror consists of an anomalous-dispersion fibre and a lumped dispersive element, such as a chirped fibre grating, which is required to brake the symmetry of the loop for self-switching operation. It is shown that a higher switching contrast and a smaller switching power can be achieved compared with those for a standard nonlinear optical loop mirror.

Measurement of standard aluminium mirrors, reflectance versus light polarization

The dependence of the reflectance of standard aluminium mirrors on the polarization status of the incident light has been calculated and measured for an angle of incidence close to normal , so that the systematic uncertainty introduced by not controlling the light polarization status in spectrophotometric measurements of specular reflectance can be known and then eliminated or minimized.

Energy gap-determination of a carbon contaminated thermal silicon oxide thin film using reflection electron energy loss spectroscopy

The energy gap of a carbon-contaminated 15 nm thick thermally grown SiO 2 film has been deduced from reflection electron energy loss spectroscopy (REELS) experiments using various primary electron energies (80 eV ≤ E p ≤ 1500 eV) and a standard single-pass cylindrical mirror analyzer (CMA). Doing so the probed depth is expected to increase with E p. An adsorbed carbon concentration of ∼ 18 at.%, as deduced from an Auger electron spectroscopy (AES) analysis, induces the appearance of wide peaks of localized gap states in the REELS spectrum recorded with E p = 80 eV. The existence of an energy gap in the surface region of the sample is thus questionable. However, when E p is increased to 200 eV the intensity of these gap states vanishes and the characteristic REELS spectrum of amorphous SiO 2 is clearly observed. The deduced energy gap is then 9.0 ± 0.1 eV ( E p ≥ 200 eV) as expected. These findings are consistent with an in-depth analysis of the electronic properties of the film under investigation.

Localized ballooning modes in two component gas dynamic trap

Among the different schemes for 14 MeV neutron generators designed for the material testing of the elements of a fusion reactor, the concept of a generator based on a gas dynamic trap has been seriously studied during the last ten years. It is assumed that an oblique injection of fast tritium atoms is used in order to enhance the density of the neutron flux. In this case, a high energy `sloshing' ion component creates a strongly anisotropic plasma pressure with P||>>Pperpendicular to . The effect of anisotropy on the stability of localized ballooning modes and the interrelation of the latter with the `fire-hose' instability are studied on the basis of the paraxial energy principle. In contrast to the standard mirror calculation, the anisotropic model allows a complete analytical treatment of the problem. The fire-hose instability is shown to be of importance for flat radial profiles, while the stability of peaked configurations is restricted by the ballooning modes. In many cases of practical interest, the fire-hose criterion beta ||<or=2 can be used for a rough estimate of marginal stability

Design and fabrication of double-chirped mirrors

We present an analytic design method for the reproducible fabrication of double-chirped mirrors to achieve simultaneously a high reflectivity and dispersion compensation over an extended bandwidth compared with those of standard quarter-wave Bragg mirrors. The mirrors are fabricated by ion beam sputtering. Use of these mirrors in a Ti:sapphire laser leads to 6.5-fs pulses directly out of the laser. The method can also be applied to the design of chirped-fiber gratings and general optical filters.

Remembering the Slope of a Line: Tests of a Propositional Theory of Oblique Orientation

Two experiments are reported for which the objectives were to test facets of the Olson and Bialystok (1983) theory of spatial cognition as applied to the oblique effect. Olson and Bialystok propose that spatial information is encoded in the form of propositions that will vary in complexity depending on the number of spatial predicates required to represent that information. Experiment 1 tested this theory by varying the number of spatial predicates required to represent three oblique pairs: the standard mirror image, different direction, different slope (DD) and same direction, different slope (SD). With few exceptions, both accuracy judgments and reaction times (RTs) were consistent with predictions derived from the theory, However, the theory does not specify the order in which spatial predicates are analyzed, or whether all spatial predicates must be analyzed when making judgments about spatial information. Experiment 2 was designed to determine the steps involved in extracting spatial predicates from stunuli when making oblique comparisons. Based on the results of this experiment, a process model of the mental operations involved in making oblique comparisons was proposed.

Clinical evaluation of an illuminated dental mirror

The purpose of this study was to determine whether the use of an illuminated mirror improved a dental student's ability to detect oral disease or abnormalities and whether an oral examination could be conducted more efficiently with it when compared with the use of a conventional mirror and chair-mounted light source. Students examined patients with the illuminated mirror and with a standard dental mirror for caries, defective restorations, dental staining, etc. Students were observed to determine how often they adjusted the overhead light or shifted their positions to see better and the length of time the examination was noted. After each examination, students were asked to rate how well they could see in various intraoral sites. There was no difference in specificity ratios between the two techniques, and the only significant difference (p < or = 0.05) in sensitivity ratios was in the detection of caries. There was no difference in the number of position shifts or length of examinations; students made fewer external light adjustments when using the illuminated mirror. On a 10-point scale, students rated their ability to see intraorally better with the illuminated mirror.