Drag effect of one-dimensional electrons upon photoionization of D<Superscript>(−)</Superscript> centers in a longitudinal magnetic field

A theory is elaborated for the impurity photon drag effect in a semiconductor quantum wire exposed to a longitudinal magnetic field B directed along the axis of the quantum wire. The phonon drag effect is associated with the transfer of the longitudinal photon momentum to localized electrons in optical transitions from D^(?) states to hybrid-quantized states of the quantum wire, which is described by a confinement parabolic potential. An analytical expression for the drag current density is derived within the model of a zero-range potential in the effective mass approximation, and the spectral dependence of the drag current density is examined at different magnitudes of B and parameters of the quantum wire upon electron scattering by a system of impurities with short-range potentials. It is established that the spectral dependence of the drag current density exhibits a Zeeman doublet with a clear beak-shaped peak due to optical transitions of electrons from D^(?) states to states with the magnetic quantum number m=1. The possibility of using the photon drag effect in a longitudinal magnetic field for the development of laser radiation detectors is analyzed.     

Performance of photon drag and photon drag-optical rectification detectors in the 2 to 33 μm range

Previous studies of the spectral response of p-Ge photon drag and n-Gap photon drag-optical rectification detectors have been extended. Measurements have also been made of the spectral response of p-Si photon drag, p-GaP photon drag-optical rectification and p-GaAs photon drag-optical rectification detectors. The wavelength range of main interest is between 2 and 11 μm, (HF, HCl, HBr, H₂O vapour and CO₂ lasers), but some measurements have also been made at 28 and 33 μm, (H₂O vapour laser).     

A photometer to measure light scattering in optical glass

A photometer is described for the measurement of light-scattering in high-quality, optical bulk glass. The photometer operates continuously over the wavelength range 0.5 to 1m and can measure scattering coefficients down to a level of 5×10^–7 cm^–1. A photon counting technique is used for light measurement and calibration is by reflection of the incident beam from an ideal diffusing screen. Measurements with high-purity benzene are in good agreement with computed and previous experimental values. Results of scattering from two samples of optical glass are given.     

Oscillations of the photon echo intensity in a pulsed magnetic field: Zeeman splitting in LiLuF<Subscript>4</Subscript>:Er<Superscript>3+</Superscript>

A method of high-resolution time-resolved optical spectroscopy using oscillations of the photon echo intensity in the presence of a perturbation, which splits the optical frequencies of the transitions of two or more ion subgroups, has been proposed and demonstrated. This method has been applied to systems in which the Zee-man effect is manifested. The transition frequencies of ions are switched by a pulsed magnetic field. Oscillations of the photon echo intensity were observed in LiLuF₄:Er³⁺ and LiYF₄:Er³⁺. The first minimum corresponding to the accumulated phase of the electric dipole moment π/2 is reached in the pulsed magnetic field with an amplitude of ～2 G at a duration of 30 ns. The Zeeman splitting in this field is ～10 MHz, which is much less than the laser spectral width (0.15 Å ～ 9 GHz). The g factor of the ⁴ F _9/2(I) excited state of the Er³⁺ ion in the LiLuF₄ matrix has been determined in zero magnetic field. The comparison with the g-factor value found from the measurement of the absorption spectrum in a magnetic field of 8 kG has been performed.     

150 Mbits−1 ch−1 12-channel optical parallel interface using an LED and a PD array

An optical fibre parallel interface has been developed for card-cage to card-cage and board-to-board interconnections, representing a practical and promising optical interconnection. For a system design of a 12 channel, 150 Mbits^–1 ch^–1 optical parallel interface over a distance of 100 m, it is shown that the choice of a long wavelength LED/PD array with graded index optical fibre array meets the requirements for both power budget and skew limitation over this transmission distance. A 7 mm thick compact package transmitter and receiver module was developed, employing a Zn-doped, mesa structure, 1.3m LED array and an isolated InGaAs PD array. An optical parallel transmission experiment over 100 m was successfully demonstrated using these modules.     

Angular dependence of the polarization of the recoil proton from the reaction γp→π0p in the region of the third resonance

The polarization of the recoil proton from the reactionp ⁰ p has been measured for photon energies between 900–1,350 MeV and pion c.m. angles between 70° and 150°. There are significant deviations from recent analysis.     

Measurement of dijet production at low <Emphasis Type="Italic">Q</Emphasis><Superscript>2</Superscript> at HERA

Triple differential dijet cross sections in interactions are presented in the region of photon virtualities 2 < Q ² < 80 GeV², inelasticities 0.1 < y < 0.85, jet transverse energies E ^* _{T 1} > 7 GeV, E ^* _{T 2} > 5 GeV, and pseudorapidities . The measurements are made in the centre-of-mass frame, using an integrated luminosity of 57 pb^-1. The data are compared with NLO QCD calculations and LO Monte Carlo programs with and without a resolved virtual photon contribution. NLO QCD calculations fail to describe the region of low Q ² and low jet transverse energies, in contrast to a LO Monte Carlo generator which includes direct and resolved photon interactions with both transversely and longitudinally polarised photons. Initial and final state parton showers are tested as a mechanism for including higher order QCD effects in low E _T jet production.Received: 13 January 2004, Revised: 21 July 2004, Published online: 18 August 2004     

The nonlinear optical rectification of a confined exciton in a quantum dot

An exciton in a disc-like quantum dot (QD) with the parabolic confinement, under applied electric field, is studied within the framework of the effective-mass approximation. The nonlinear optical rectification between the ground and the first-excited states has been examined through the computed energies and wave functions in details for the excitons. The results show that the optical rectification susceptibility obtained in a disc-like QD reach the magnitude of 10⁻² m/V, which is 3-4 orders of magnitude higher than in one-dimensional QDs. It is found that the second-order nonlinear optical properties of exciton states in a QD are strongly affected by the confinement strength and the electric field.     

Spectroscopic study of potential magneto-optic storage layers

We present an experimental investigation of magneto-optic (MO) thin film materials of interest in optical storage. XPS valence band spectra of ultrahigh vacuum deposited rare earth — Fe₅₀Co₅₀ alloys are correlated to magneto-optic and reflectivity spectra measured ex-situ in the photon energy range 0.5 E _ph 5.5 eV. It is found that 4f ⁿ 4f ^n–15d ¹ optical transitions contribute to room temperature Kerr spectra in Pr-FeCo and Nd-FeCo, but only in the UV spectral region (300 nm). Eu is found to enter Eu-FeCo intermetallic alloys with a 4f ⁷ ground state at –2 eV binding energy. However, no substantial contribution to the Kerr effect from excitations of this electronic state has been observed n either at room temperaturen or at 100 K. We present a general argument that 4f excitations of RE ions in typical intermetallic alloys can never be expected to contribute more than some tenths of a degree to _k in contrast to the well known huge rotations in RE-chalcogenides.For Yb-FeCo we have observed in XPS a mixed valence behavior of Yb showing a discontinuous transition from divalent Yb²⁺ in the pure metal to mixed valent Yb^2.55+ in amorphous Yb-FeCo films. Nofd contributions to the room temperature MO spectra have been detected. Strong optical enhancement effects are presented for metallic bilayer and multilayer structures of the type MO-layer/reflector. The total thickness of an optimized structure corresponds to about two times the penetration depth of light. Enhancement occurs predominantly at photon energies below the plasma frequency of the reflector material and is caused by low values of the optical constantsn andk of the reflector. In storage materials like Tb-FeCo the read-out performance can be improved by about a factor of 2 with a bilayer of 30 nm Tb-FeCo on Cu. Quantitative modelling of the optical and magneto-optic properties of these films is discussed.     

Measurement of Optical Constants of CVD-Diamond for Short-Wavelength Far-Infrared Lasers

A diagnostic system using short-wavelength far-infrared (FIR) lasers (40–70 m in wavelength) is now being developed for high density and large volume plasmas. In the wavelength region, a CVD-diamond is the excellent materials for optical windows of the laser and the plasma vessel and beam splitters of a multichannel interferometer. To design these optical elements, the optical constants (refractive index n, absorption coefficient and transmissivity T) of the CVD-diamond have been measured precisely by using FIR lasers of 48-, 57- and 71-m in wavelength. As an example, the result for 57.1511 m light is n = 2.383(1) ± 0.002, = 0.19 ± 0.05 cm^-1 and T = 97.5 ± 1.5% at 1.023 mm in thickness.     

Electron drag in intermediate magnetic fields with low electron density

Electron drag between two two-dimensional electron systems has been measured in intermediate magnetic fields (/τ<ω_ck_BT) with a relatively low electron density. We explore, in this sample, the unusual increase of drag in intermediate magnetic fields which was well characterized by a nearly temperature independent B³ dependence. The anomalous behavior of electron drag observed in higher density samples is found to persist for low sample density.     

Phase transformations in quaternionic quantum field theory

Phase transformations of a scalar quaternionic quantum field are examined as unitarily implemented symmetries. Under very general quantization conditions it is shown, in both global and local cases, that the only sensible phase invariance that has been suggested is pp ^–1, wherep is a quaternion and a quaternionic scalar field.     

Charge Exchange of the Centers in Electron–Irradiated Zinc Selenide

The optical absorption induced by the photosensitive centers formed upon electron irradiation (E = 5 MeV, = 1.7·10¹⁸ cm^–2) of polycrystalline ZnSe has been studied. A comparison of the optical properties of the irradiated crystals with the known data for ZnS has allowed the assumption that the 496–, 563–, and 652–nm bands in ZnSe are associated with the anion vacancies being in different charge states. The ratio between the concentrations of the optical absorption centers in the crystals photoexcited at 80 K is determined by the electron traps participating in the processes of charge exchange of the vacancies.     

The Biot-Savart-Ampère law and the vacuum fieldB (3)

It is shown that the longitudinal vacuum fieldB ⁽³⁾ emerges from the Biot-Savart-Ampère law governing the motion of an electron with intrinsic spin moving at the speed of light, in which case the expression forB ⁽³⁾ is identical with that obtained from the Dirac equation of one electron accelerated to the speed of light by an electromagnetic field. Use of an O(3), non-Abelian, gauge geometry forB ⁽³⁾ identifies the quantized photon momentum appearing in the Dirac equation witheA ⁽⁰⁾, wheree is the charge on the electron andA ⁽⁰⁾ the amplitude of the vector potential. The condition =eA ⁽⁰⁾ can be obtained in turn from the relativistic Hamilton-Jacobi equation of an electron accelerated to the speed of light by an electromagnetic field.     

Infrared free electron laser measurement of the photon drag effect in P-silicon

We report the use of FELIX (free electron laser for infrared experiments) to study photon drag in p-silicon over the wavelength range 25–80m. Previous spot measurements using a pulsed water vapour laser had indicated high response at 28 and 33m associated with transitions within the valence band. These earlier results have been confirmed and the main futures of the extended photon drag spectrum are also explainable by reference to the valence band structure. A practical outcome of the experiment is the design of a subnanosecond response time detector to observe the 1GHz frequency micropulse output from FELIX.     

Precise measurement of quadrupole moment of8B by use of a modified β-NMR

The nuclear quadrupole moment of⁸B(I =2⁺,T _1/2=769 ms) has been determined by use of a modified -NMR detection as |Q(⁸B)|=68.3±2.1 mb. A field gradient was obtained in a single crystal Mg at room temperature.     

3,3′-Benzene-1,4-diylbis[1-(substituted)phenylprop-2-en-1-one] derivatives: A new class of materials for third-order nonlinear optical applications

We have investigated the third-order nonlinear optical parameters of Bischalcones embedded in DMF solution and in solid PMMA matrix, by Z-scan technique using nanosecond laser pulse trains at 532 nm. Z-scan results reveal that the Bischalcones exhibits negative nonlinear refractive index as high as 10⁻¹¹ esu. The molecular two-photon absorption cross-section of Bischalcones were of the order 10⁻⁴⁶ cm⁴ s/photon, which is nearly two orders of magnitude larger than that of Rhodamine 6G which is 10⁻⁴⁸ - 10⁻⁵⁰ cm⁴ s/photon. We found that, the two-photon absorption (TPA) is the dominating nonlinear process leading to nonlinear absorption in both the cases in solution and as well as in solid medium. Based on TPA process, the Bischalcones exhibit good optical power limiting of nanosecond laser pulses at the input wavelength. The nonlinear optical parameters found to increase on enhancing the strength of the electron donor groups indicating the dependence and importance of electron donor/acceptor units on third-order nonlinear optical susceptibility χ⁽³⁾.     

Linear High-Tc YBa2Cu3O7?δ Superconducting Thin Film Infrared Detectors Coupled with a Cylindrical Microlens Array in Quartz Glass Substrate

Monolithic linear cylindrical microlens array in a quartz glass substrate is fabricated using photolithography and ion beam etching technique, the high-Tc YBa₂Cu₃O_7– superconducting thin films are deposited through excimer laser scanning ablation, the superconducting thin films are patterned by photolithographic method and ion beam etching technique, and the hybrid structure of the microlens array component and the superconducting IR detectors has been obtained using an IR glue to cement the microlens component onto the superconducting device. We also investigate the optical response characteristics of the hybrid device in the optical spectral region of 1 ~ 5 m, as follows. The average optical responsivity of the hybrid device is 1.6×10⁴ V/W, average noise equivalent power is 2.3×10^–12 WHz^–1/2, average detectvity is 3.2×10⁹ cmHz^1/2W^–1, and the non-uniformity of detectvity (D*) is not more than 14%. The experimental results show that the performance of the superconducting device is improved notably using a quartz glass refractive microlens array as the incident IR radiation concentrators.