FIG 2 - uploaded by Paul Dawson
Content may be subject to copyright.
Optical layout for the prism coupler rig with input laser beams in the infrared and visible. Investigations are performed in the infrared and systemand sample/prism-alignment procedures in the visible. The components in the system are as follows: IR HeNe infrared HeNe laser 3.392 m; HeNe visible HeNe laser 632.8 nm; M1-M4R mirrors removable ; C chopper; P infrared polarizer; A1,2 apertures; BS1–3 beam splitters; BE beam expander; (D ref ,D sig ) reference, signal detectors cooled InSb; FL focusing lens; PL projection lens; VS viewing screen. Note that M4 reflects the input beam up out of the plane of the page into the vacuum system. For infrared measurements mirrors M1, M4 are in place and M2, M3 removed. For beam alignment through the system mirror M2 is inserted and M3 is replaced by a viewing screen. For the sample/prism alignment procedure, i.e., setting up a parallel coupling gap, M3 is inserted and an expanded visible HeNe beam is injected into the system via BS2; interference fringes set up between prism and sample surfaces are projected on the viewing screen, VS, by lens PL.
Source publication
The field of surface polariton physics really took off with the prism coupling techniques developed by Kretschmann and Raether, and by Otto. This article reports on the construction and operation of a rotatable, in vacuo, variable temperature, Otto coupler with a coupling gap that can be varied by remote control. The specific design attributes of t...
Contexts in source publication
Context 1
... low-T Otto coupler is illustrated in Fig. 1 in side views, both along the axis of rotation Fig. 1b and normal to that direction Fig. 1a. Figure 2 gives an outline of the optical system as a whole, detailing the components and beam paths for both the visible laser used for alignment and the infrared laser used in the investigations. The Otto coupler is housed in a small high-vacuum system typical, operating base pressure of 10 7 Torr supported on an optical table. ...
Context 2
... experimental investigations. Beam selection is TABLE I. A comparison of the principal design features, set against the pertinent physical considerations a-g, of the air-based, variable-gap Otto coupler and the vacuum-based, variable-gap coupler. effected by the insertion/removal of mirrors as illustrated in the diagram of the optical layout of Fig. 2. In the experiment the IR HeNe beam runs parallel to the optical table before being deflected vertically upwards into the vacuum chamber. The beam then impinges on the entrance hypotenuse face of the prism and undergoes retroreflection in the prism, as illustrated in Figs. 1b and 3a, to return parallel to, but laterally displaced from ...
Context 3
... to the optical table before being deflected vertically upwards into the vacuum chamber. The beam then impinges on the entrance hypotenuse face of the prism and undergoes retroreflection in the prism, as illustrated in Figs. 1b and 3a, to return parallel to, but laterally displaced from the input beam. On the return reflec- tion from mirror M4 see Fig. 2 the lateral displacement becomes a vertical displacement, the usefulness of this fea- ture being explained shortly. Apart from the apertures and guiding mirrors there are three in-line components in the horizontal part of the beam path. The first is a polarizer which is oriented such that radiation with the electric field vector in the ...
Context 4
... polarizer and beam splitter there is inserted a mechanical chopper operating at 600 Hz to modulate the light input for phase sensitive detection using lock-in amplifiers. The radia- tion intensity in the reference and signal reflected beams is measured using high quality, cooled indium antimonide InSb detectors, D ref and D sig , respectively, in Fig. ...
Context 5
... components in the system. The axis of rotation is first located relative to the prism holder. The prism is placed in the holder defining the correct x position and is then adjusted with the flexure stage to the correct y position to give the optimum placement of the rotation axis. The beam displacement is systematically adjusted using mirror M4 Fig. 2 to yield ''walkoff'' points in the angle scan that are consistent with those calculated, as in Fig. 3b. It is then straightforward to set to center the beam relative to the sample face of the ...
Context 6
... coupling gap of uniform width is crucial to the suc- cessful operation of the system. Information on the parallel- ism between the sample surface and the sample short face of the prism is obtained by the use of an expanded laser beam 632.8 nm incident below critical angle in the prism see Fig. 2 where there is significant transmission across the sample face of the prism. In this situation, light reflected off the sample face of the prism interferes with light transmitted across the prism/gap interface and reflected off the sample surface. Interference fringes are observed outside the system using a beam splitter, a projection ...
Context 7
... transmission across the sample face of the prism. In this situation, light reflected off the sample face of the prism interferes with light transmitted across the prism/gap interface and reflected off the sample surface. Interference fringes are observed outside the system using a beam splitter, a projection lens, and a screen as illustrated in Fig. 2. The sample orientation is ad- justed in very small steps using the set of three piezoactua- tors supporting the copper sample mounting plate, to yield only one bright fringe in the field of view. This process ren- ders the sample parallel to the prism within half a wave- length of visible light, vis /2, or within ir /10 where ir is ...
Citations
... A schematic of the core of the optical set-up is shown in Fig. 1. Since the precursor to the system used here has been described in detail in Ref. [41] we concentrate on recapping only the principle of operation and on the changes that have been implemented by comparison to the system of Ref. [41]. ...
... A schematic of the core of the optical set-up is shown in Fig. 1. Since the precursor to the system used here has been described in detail in Ref. [41] we concentrate on recapping only the principle of operation and on the changes that have been implemented by comparison to the system of Ref. [41]. ...
... The principal improvements incorporated in the new Otto coupler system used in this work, compared to that described previously [41] are as follows: ...
The contribution of electron–phonon scattering and grain boundary scattering to the mid-IR (λ = 3.392 μm) properties of Au has been assessed by examining both bulk, single crystal samples—Au(1 1 1) and Au(1 1 0)—and thin film, polycrystalline Au samples at 300 K and 100 K by means of surface plasmon polariton excitation. The investigation constitutes a stringent test for the in-vacuo Otto-configuration prism coupler used to perform the measurements, illustrating its strengths and limitations. Analysis of the optical response is guided by a physically based interpretation of the Drude model. Relative to the reference case of single crystal Au at 100 K (ε = −568 + i 17.5), raising the temperature to 300 K causes increased electron–phonon scattering that accounts for a reduction of ∼40 nm in the electron mean free path. Comparison of a polycrystalline sample to the reference case determines a mean free path due to grain boundary scattering of ∼17 nm, corresponding to about half the mean grain size as determined from atomic force microscopy and indicating a high reflectance coefficient for the Au grain boundaries. An analysis combining consideration of grain boundary scattering and the inclusion of a small percentage of voids in the polycrystalline film by means of an effective medium model indicates a value for the grain boundary reflection coefficient in the range 0.55–0.71.
... A diagram of the ATR optical measurement setup, following the scheme of Otto [22], is shown in Fig. 1 and a detailed description of the system may be found in Refs. [23,24]. In essence, a high refractive index sapphire 30°-60°-90°prism (with critical angle for total internal reflection, h TIR i , of $36°) couples photons to the slower surface plasmon polaritons (SPPs). ...
... It has an electric component in the saggital (x-z) plane and has the same propagation vector component, k x , and frequency, x, as the incident beam within the prism; it extends across the vacuum gap between prism and film. At an appropriate resonant angle of incidence [23], where their momentum component, k x , and frequency, x, match, photons from the evanescent field can couple to SPPÕs on the YBCO surface with an efficiency that depends on the width of the coupling gap between prism and sample. At optimal coupling the reflectance dips to a few percent or less. ...
... The system has been designed to allow the vacuum gap to be remotely adjusted while installed in the vacuum chamber [23]. This has advantages over fixed gap systems of (a) improved parallelism at all temperatures, (b) improved optimization of the coupling to the SPP resonance, and (c) the possibility of acquisition of several reflectance scans for different gaps, which facilitates more robust modeling. ...
The mid-infrared optical response of c-axis thin films of YBa2Cu3O7−δ has been studied using Otto-configuration attenuated total reflectance. The measured reflectance––angle characteristics are dominated by a strong absorption feature due to the excitation of surface plasmons, and can be modeled to determine the a–b plane dielectric function. The results show that while εi, and therefore σr, are temperature independent, |εr| exhibits a moderate decrease with increasing temperature. A stronger dependence on doping is observed: the magnitudes of εi and |εr| are both strongly suppressed as δ increases. Critical comparison is made with the extensive body of infrared normal reflectance data. A generalized Drude analysis shows that the plasma frequency is independent of temperature, but decreases with decreasing doping. The scattering rate increases with temperature, and also increases with decreasing doping, consistent with stronger coupling in the underdoped regime. The mass-enhancement is small but increases to 30–40% at δ=0.6. Difficulties in reconciling the results with some current theories of high-Tc materials are discussed. Finally, the surface plasmon propagation lengths and penetration depths are shown to vary systematically with doping.
The present report aims at analyzing the quantum well (QW) structures using the highly sensitive surface plasmon resonance (SPR) technique in Otto configuration. The optical properties of ZnO and Ni doped ZnO (NiZnO) based QW structures grown using Pulsed laser deposition technique are investigated. An optimal value of QW width (8 nm) is deduced from the SPR study for maximum charge carrier confinement which is in coherence with the photoluminescence (PL) studies conducted on the same QW structures. The metal-dielectric interfaces were modelled primarily for the design of QW structures to be analysed experimentally. The mechanism behind the coupling of QWs with SP excitation has been proposed theoretically and experimentally to substantiate the results of PL and SPR studies. The variation in the SPR curves observed as a function of the QW width can be attributed to the interaction of evanescent SP field originating at the Au/QW interface and electroabsorptive behaviour of QWs towards the SP field.
A simple imaging geometry in which total internal reflection in a glass prism is frustrated by the proximity of a metal surface is implemented for observation of surface plasmon resonance. At a certain angle of incidence, the total internal reflection is completely suppressed at a certain distance between the metal and the prism surfaces. Using planar metal and spherical prism surfaces, the distance parameter is sampled in a single image. This allows a direct determination of the complex refractive index in bulk samples as well as in thin films. Our experimental data are in good agreement with previously published data.
Results are reported on the a-b plane dielectric function (ε) of thin-film c-axis NdBa2Cu3O7-δ with close to optimal oxygen doping (Tc~90 K) in the mid-infrared (wavelength 3.392 µm) over the temperature range 85 K to 300 K. An attenuated total reflectance technique based on the excitation of surface plasmon polaritons is used. The results show that |εr| decreases quasi-linearly with increasing temperature, while εi is invariant with temperature to within experimental uncertainties. Representative values are ε = [εr + iεi] = (-12.9±0.6) + i(23.0±1.5) at T~295 K and ε = (-15.7±0.7) + i(23.5±1.1) at T~90 K. The raw data are interpreted in terms of the generalized Drude model which gives effective scattering rates (1/τ*) that increase with temperature from about 3800 cm-1 at 90 K to about 4300 cm-1 at 295 K. There are indications of a superlinear T-dependence in the scattering, 1/τ*; a fit to a function of the form 1/τ* = A + BTα gives α = 2.8±0.7. The effective plasma frequency, ωp*, with an average value of approximately 21 000 cm-1 was independent of temperature.
