41 research outputs found
Synthetic adjacent pulse repetition interval length method to solve integer ambiguity problem: theoretical analysis
This paper describes a novel approach for realizing femtosecond optical frequency comb (FOFC)-based length measurement. This approach is based on the analogy between the phase unwrapping problem and the integer ambiguity problem. Because the conventional synthetic wavelength method can solve the former, we investigated the possibility of using a synthetic adjacent pulse repetition interval length method to solve the latter. The results of theoretical analyses and numerical investigations show the feasibility of the proposed method. Our results should contribute toward the further development of FOFC-based length measurement methods
Temporal coherence shaping based on spectral-domain destructive interference of pulses with different self-phase modulations
We show via a numerical simulation that the temporal coherence function (TCF) can be shaped by the destructive interference of pulses characterized by different amounts of self-phase modulation (SPM) in the spectral domain. We find that pulse spectra destructively interfering with one another can yield a TCF with distinct peaks. Numerical investigation demonstrates that the shape of the TCF is changeable not only by broadening the spectrum but also by overlapping spectra of the pulses that have experienced different amounts of SPM
Large Magnetic Susceptibility Anisotropy of Metallic Carbon Nanotubes
Through magnetic linear dichroism spectroscopy, the magnetic susceptibility
anisotropy of metallic single-walled carbon nanotubes has been extracted and
found to be 2-4 times greater than values for semiconducting single-walled
carbon nanotubes. This large anisotropy is consistent with our calculations and
can be understood in terms of large orbital paramagnetism of electrons in
metallic nanotubes arising from the Aharonov-Bohm-phase-induced gap opening in
a parallel field. We also compare our values with previous work for
semiconducting nanotubes, which confirm a break from the prediction that the
magnetic susceptibility anisotropy increases linearly with the diameter.Comment: 4 pages, 4 figure
CALIBRATION OF 2-DOF PARALLEL MECHANISM
Abstract In order to avoid some drawbacks of traditional Coordinate measuring machine (CMM) based on serial mechanism, we are developing Parallel-CMM based on a parallel mechanism. We have already built the prototype of 3-DOF Parallel CMM and now we are researching about the calibration of our Parallel CMM. When we use a CMM to measure the objects, we need to calibrate the geometrical parameters of the CMM to evaluate the uncertainty of measurement. In this paper, we discuss the details of calibration for 2-DOF parallel mechanism instead of 3-DOF parallel mechanism
Femtosecond optical frequency comb-based tandem interferometer
The principle of a unique interferometer, called a femtosecond optical frequency comb-based (FOFC-based) tandem interferometer, is proposed and demonstrated for the first time. By taking advantage of both the temporal coherence characteristic of an FOFC light source and the transmission characteristics of acquired length information based on a tandem interferometer, the present technique is expected to be useful for high-precision measurement of long distances for not only science purposes but also industry requirements
Spin-phonon coupled modes in the incommensurate phases of doped CuGeO
The doping effect of the folded phonon mode at 98 cm was investigated
on the Si-doped CuGeO by magneto-optical measurements in far-infrared (FIR)
region under high magnetic field. The folded phonon mode at 98 cm
appears not only in the dimerized (D) phase but also in the
dimerized-anitiferromagnetic (DAF) phase on the doped CuGeO. The splitting
was observed in the incommensurate (IC) phase and the antiferromagnetically
ordered incommensurate (IAF) phase above . The split-off branches exhibit
different field dependence from that of the pure CuGeO in the vicinity of
, and the discrepancy in the IAF phase is larger than that in the IC
phase. It is caused by the interaction between the solitons and the impurities.Comment: 7 pages, 4 figures, resubmitted to Phys. Rev.
Field-Induced Magnetic Ordering in the Quantum Spin System KCuCl
KCuCl is a three-dimensional coupled spin-dimer system and has a singlet
ground state with an excitation gap K. High-field
magnetization measurements for KCuCl have been performed in static magnetic
fields of up to 30 T and in pulsed magnetic fields of up to 60 T. The entire
magnetization curve including the saturation region was obtained at K.
From the analysis of the magnetization curve, it was found that the exchange
parameters determined from the dispersion relations of the magnetic excitations
should be reduced, which suggests the importance of the renormalization effect
in the magnetic excitations. The field-induced magnetic ordering accompanied by
the cusplike minimum of the magnetization was observed as in the isomorphous
compound TlCuCl. The phase boundary was almost independent of the field
direction, and is represented by the power law. These results are consistent
with the magnon Bose-Einstein condensation picture for field-induced magnetic
ordering.Comment: 9 pages, 7 figures, 9 eps files, revtex styl
Far-Infrared Spectroscopy in Spin-Peierls Compound CuGeO_3 under High Magnetic Fields
Polarized far-infrared (FIR) spectroscopic measurements and FIR
magneto-optical studies were performed on the inorganic spin-Peierls compound
CuGeO_3. An absorption line, which was found at 98 cm in the dimerized
phase (D phase), was assigned to a folded phonon mode of B symmetry. The
splitting of the folded mode into two components in the incommensurate phase
(IC phase) has been observed for the first time. A new broad absorption
centered at 63 cm was observed only in the axis
polarization, which was assigned to a magnetic excitation from singlet ground
state to a continuum state.Comment: 9 pages multicolREVTeX, 10 figure
Possible Phase Transition Deep Inside the Hidden Order Phase of Ultraclean URu2Si2
To elucidate the underlying nature of the hidden order (HO) state in
heavy-fermion compound URu2Si2, we measure electrical transport properties of
ultraclean crystals in a high field/low temperature regime. Unlike previous
studies, the present system with much less impurity scattering resolves a
distinct anomaly of the Hall resistivity at H*=22.5 T well below the
destruction field of the HO phase ~36 T. In addition, a novel quantum
oscillation appears above a magnetic field slightly below H*. These results
indicate an abrupt reconstruction of the Fermi surface, which implies a
possible phase transition well within the HO phase caused by a band-dependent
destruction of the HO parameter. The present results definitely indicate that
the HO transition should be described by an itinerant electron picture.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
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