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1
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Photoinduced Phase Transition in Pr_{0.5}Ca_{0.5}CoO_3 Studied by Sequential Pulse Excitations

100%
Seko K., Okimoto Y., Kurashima M., Fukaya R., Egawa T., Ishikawa T., Onda K., Koshihara S., Kyomen T., Itoh M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2
369-371
EN
A perovskite-type cobalt oxide, Pr_{0.5}Ca_{0.5}CoO_3 (PCCO), shows photoinduced phase transition. In this study, we successively irradiated two laser pulses with different intensities to PCCO and probed the transient change of the reflection at 2.0 eV. Assuming propagation of the two different photoinduced metallic states, we could reproduce the time profiles as well as the magnitude in the reflectance change, indicating the fabrication of the photoinduced multilayered thin film in Pr_{0.5}Ca_{0.5}CoO_3.
2
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Femtosecond Reflection Spectroscopy in La_{1.5}Sr_{0.5}CoO_4

100%
Egawa T., Okimoto Y., Fukaya R., Onda K., Ishikawa T., Koshihara S., Isayama A., Sasagawa T.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2
307-309
EN
Ultrafast optical response has been investigated using fs laser system on a perovskite-type cobalt oxide, La_{1.5}Sr_{0.5}CoO_4. After the photoirradiation at room temperature, the time profile of relative change of reflectance (Δ R/R) shows a sudden change within the pulse duration ( ≈ 150 fs) and decays with a lifetime of ≈ 330 fs. The sign of Δ R/R after the photoexcitation is positive in the mid-infrared region (at 0.50 eV) while negative in the visible energy region (at 2.0 eV), implying photoinduced change of the electronic structure after the photoexcitation.
3
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Extension of the p-Spectrum Method to the Higher Frequencies

80%
Pałka N.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
534-537
EN
The p-spectrum method is a time domain spectroscopy-based technique for reflection analysis of materials (including explosives) that takes into account only part of the reflected signal, which is next analyzed via the Fourier transform. The method is limited to the frequencies of about 1.8 THz due to the pulse properties of our time domain spectroscopy setup. In this paper we theoretically prove that application of a shorter pulse can increase this frequency range up to 2.2 THz, that enables analysis of penthrite and octogen, two important explosives.
4
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Transmission Spectra of Materials in the Terahertz Range Measured by a Hot Electron Bolometer-Based System

80%
Pałka N., Walczakowski M., Zagrajek P., Czerwiński A., Sypek M., Szustakowski M.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
538-541
EN
This paper presents an optical system for transmission spectral measurements in the terahertz range. The source of radiation is a tunable solid-state laser, which generates a narrow-band nanosecond pulses in the range 0.67-2.68 THz and based on optical parametric oscillator phenomenon. The signal is detected with a fast and sensitive hot electron bolometer. Principle of generation and detection of pulses as well as methodology of measuring spectral characteristics are presented. We compared the results obtained with the free-space setup, which is based on the optical parametric oscillator and hot electron bolometer, with a purged time domain spectroscopy system in the range of 0.7-2.2 THz.
5
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Photoinduced Ionic to Neutral Phase Transition in TTF-CA Studied by Time-Resolved Infrared Vibrational Spectroscopy

80%
Matsubara Y., Yoshida T., Ishikawa T., Okimoto Y., Koshihara S., Onda K.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2
340-342
EN
We studied the photoinduced ionic to neutral phase transition in tetrathiafulvalene-p-chloranil (TTF-CA) using time-resolved infrared vibrational spectroscopy. By monitoring the charge sensitive b_{1u} ν_{10} band of CA after photoexcitation by a 1.55 eV pulse, we found that the photoinduced N-phase has the same charge of the N-phase in thermal equilibrium and there is no charge variation during the photoinduced phase transition. We also found that the photoinduced N-phase grows through at least two steps over 300 ps.
6
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Hyperspectral Imaging Infrared Sensor Used for Enviromental Monitoring

80%
Kastek M., Piatkowski T., Zyczkowski M., Chamberland M., Lagueux P., Farley V.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
463-467
EN
This paper presents detection, identification and quantification of gases using an infrared imaging Fourier-transform spectrometer. The company Telops has developed an imaging Fourier-transform spectrometer instrument, Hyper-Cam sensor, which is offered as short or long wave infrared sensor. The principle of operation of the spectrometer and the methodology for gases detection, identification and quantification has been shown in the paper, as well as theoretical evaluation of gases detection possibility. The variation of a signal reaching the imaging Fourier-transform spectrometer caused by the presence of a gas has been calculated and compared with the reference signal obtained without the presence of a gas in the imaging Fourier-transform spectrometer field of view. Some result of the detection of various types of gases has been also included in the paper.
7
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Complex THz Reflectance Spectra of Hexogen Measured for Various Surfaces

70%
Palka N.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
854-857
EN
In this paper, we report on measurements of reflection spectra of hexogen (RDX) by means of time domain spectroscopy. We analyzed both phase and amplitude of reflected impulses for three cases: detuning, samples with rough surfaces and samples with curved surfaces. It can be concluded that both spectral characteristics can be applied for identification of explosives in the reflection configuration.
8
Content available remote

Slow Dynamics of the Photoinduced Phase Transition in Pd(dmit)_2 Salts (dmit = 1,3-dithiol-2-thione-4,5-dithiolate)

70%
Ishikawa T., Tanaka T., Fukazawa N., Matsubara Y., Okimoto Y., Onda K., Koshihara S., Tamura M., Kato R.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2B
316-318
EN
Slow dynamics of the initially photoinduced state has been observed by the pump-probe type time-resolved reflection spectroscopy in the charge separated phase of the half-filled strong dimer system, Et_2Me_2Sb[Pd(dmit)_2]_2 (dmit = 1,3-dithiol-2-thione-4,5-dithiolate). We have succeeded to reproduce the probe photon energy dependence of the time profile qualitatively in the time delay range from 10 ps to 1 ns assuming the dynamical expansion of the domain of the photo-induced dimer-Mott insulating phase in the host charge-separated one.
9
Content available remote

Room Temperature Carrier Kinetics in the W-type GaInAsSb/InAs/AlSb Quantum Well Structure Emitting in Mid-Infrared Spectral Range

61%
Syperek M., Ryczko K., Dallner M., Dyksik M., Motyka M., Kamp M., Höfling S., Misiewicz J., Sęk G.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1224-1228
EN
Room temperature carrier kinetics has been investigated in the type-II W-design AlSb/InAs/Ga_{0.80}In_{0.20}As_{0.15}Sb_{0.85}/InAs/AlSb quantum well emitting in the mid-infrared spectral range (at 2.54 μ m). A time-resolved reflectance technique, employing the non-degenerated pump-probe scheme, has been used as a main experimental tool. Based on that, a primary carrier relaxation time of 2.3±0.2 ps has been found, and attributed to the initial carrier cooling process within the quantum well states, while going towards the ground state via the carrier-optical phonon scattering mechanism. The decay of a quasi-equilibrium carrier population at the quantum well ground states is primarily governed by two relaxation channels: (i) radiative recombination within distribution of spatially separated electrons and holes that occurs in the nanosecond time scale, and (ii) the hole tunnelling out of its confining potential, characterized by a 240±10 ps time constant.
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