Purevdorj Munkhbaatar - Academia.edu (original) (raw)

Papers by Purevdorj Munkhbaatar

The Korean Physical Society, Nov 1, 2013

Physical Review B, 2018

We calculated the polarization-dependent Raman scattering cross section spectra of LaMnO 3 below ... more We calculated the polarization-dependent Raman scattering cross section spectra of LaMnO 3 below the A-type magnetic ordering temperature. Two strong peaks appear around the MnO 6 octahedra stretching phonon frequency. One mode shows A g symmetry, while the other mode shows B g symmetry. We found that the A g symmetry peak is a Jahn-Teller phonon coupled to the orbital wave and the B g symmetry peak is an orbital wave coupled to a Q 2 phonon mode via the Jahn-Teller electron-phonon coupling.

Solid State Communications, 2021

We calculated the infrared conductivity spectrum of orbitally ordered LaMnO 3 in phonon frequency... more We calculated the infrared conductivity spectrum of orbitally ordered LaMnO 3 in phonon frequency and overtone frequency ranges. We considered orbital exchange, Jahn-Teller electron-phonon coupling, and phonon-phonon coupling. The fundamental excitation of the phonon-coupled orbiton was only Raman active, not infrared active, while its overtone modes were both Raman and infrared active. Our calculations reproduced the small peaks near 1300 cm −1 observed both in Raman scattering and infrared conductivity spectra, as consistent with previous experimental results.

Solid State Phenomena, 2021

We applied the dielectric function method to solve analytically L-NL-L structure problems with ne... more We applied the dielectric function method to solve analytically L-NL-L structure problems with negative Kerr nonlinearity. A damped wave in linear and a periodic standing wave in non-linear media had to be matched at boundaries. We gave a formulation of boundary conditions that did not explicitly include a film thickness. The boundary-value of a dielectric function can be expressed through the constant of non-trivial integral of motion. Using it, one generates a family of matched solutions satisfying boundary conditions. Then arbitrary film thickness can be checked against this family of solutions in search of matches. As a result, all fitted solutions are determined straightforwardly.

IOP Conference Series: Materials Science and Engineering, 2019

The Kerr-lens mode-locking (KLM) is known as a suitable method for generation of femtosecond puls... more The Kerr-lens mode-locking (KLM) is known as a suitable method for generation of femtosecond pulses and mode-locked Ti:sapphire laser is now widely used sources of stable, energetic femtosecond pulses. We will present the simulation of KLM in Ti:sapphire laser cavities with a folded-cavity four-mirror by applying the ABCD ray-tracing technique for a Gaussian beam. Simulations will be performed for an asymmetric resonator design. Based on the numerical analysis, we will find the optimum design parameters (slit position, gain cavity spacing, gain medium position) for KLM.

Optics Communications, 2020

We measured photon absorption in dielectric media and proposed the photon-version Beer-Lambert's ... more We measured photon absorption in dielectric media and proposed the photon-version Beer-Lambert's law to quantify the absorption. We used a Hong-Ou-Mandel interferometer and 810 nm twin-photons. We found that the depth ratio of the null point in the interference patterns of the interferometer agreed with the classical transmittance of the samples. We established a statistical model of the photon absorption process and proposed an information entropy interpretation to understand the meaning of the Beer-Lambert law. Comparisons of the results of the photon absorption experiments with classical experiments demonstrate the validity of our model and interpretation.

Solid State Phenomena, 2019

Two different pump-probe (PP) setups were developed successfully with different femtosecond pulse... more Two different pump-probe (PP) setups were developed successfully with different femtosecond pulse lasers. Using a PP setup with an ultra-short pulse laser, the excitation of coherent phonons in GaAs was measured for a calibration and an accuracy test of the developed setup. The frequencies of the coherent phonon modes were in good agreement with reported values [1, 2]. The setups for ZnSe and GaAs were transmission and reflection–type, respectively. When using the ultra-short pulse laser, the signal in the PP experiment was measured by a balanced photo diode.In the other PP experimental setup, built to measure the transient transmittance of bulk ZnSe, the light source and detector differed from the previous PP setup. A strong pulse laser was successfully used for the spectrally resolved pump probe experimental setup. A broadband, high-resolution spectrometer (HR4000CG-UV-NIR) was used as the detector.

Journal of Modern Optics, 2019

We calculated third order non-linear polarization to estimate the two-photon absorption of non-in... more We calculated third order non-linear polarization to estimate the two-photon absorption of non-interacting two-level molecules in the transmission-type degenerate pump-probe geometry. The spectral intensity and the phase changes of the laser pulses when passing through a thin dielectric slab composed of the molecules were considered. We also investigated the effect of the decay rate of the molecules and the chirp of the pulses on their spectral intensity and phase changes.

Optics Communications, 2017

We propose an excitation-probe measurement method utilizing entangled photon pulses. The excitati... more We propose an excitation-probe measurement method utilizing entangled photon pulses. The excitation-probe signal is dominated by stimulated Raman scattering as well as two-photon absorption when the time delay between the excitation pulse and the probe pulse is shorter than the pulse duration. We demonstrate that the two-photon-absorption signal can be suppressed when the photons of the pulses are entangled. The stimulated Raman scattering signal can be composed of many peaks distributed over broad photon energies owing to the transitions between numerous quantum states in complex materials. We show that the desired peaks among the many peaks can be selected by controlling the thickness of the nonlinear crystal, the pump pulse center frequency, and the polarization of the excitation pulse and probe pulse.

Journal of the Optical Society of Korea, 2012

A polarimetric experimental method was developed to determine the Jones matrix elements of transp... more A polarimetric experimental method was developed to determine the Jones matrix elements of transparent optical materials without sign ambiguity. A set of polarization dependent transmittance data of the samples was measured with polarizersampleanalyzer system and another set of data was measured with polarizersamplequarter-wave plateanalyzer. Two data sets were compared and mathematically analyzed to obtain the correct signs of the elements of the matrix. The Jones matrix elements of a quarter-wave plate were determined to check the validity of the method. The experimentally obtained matrix elements of the quarter-wave plate were consistent with the theoretical expectations. The same method was applied to obtain the Jones matrix elements of a twisted nematic liquid crystal panel.

We present the time dependent transmittance of LaMnO3 thin film and [(LaMnO3)n/(SrTiO3)8]20 (n=2 ... more We present the time dependent transmittance of LaMnO3 thin film and [(LaMnO3)n/(SrTiO3)8]20 (n=2 and 8) superlattices grown on SrTiO3 substrate. We used the laser pulse pump-probe technique. We observed two phonon oscillation in the LaMnO3 film at 8 THz and at 15 THz. In the superlattices, 8 THz mode seemed obliterated. The phonon oscillation damping time constant was also different. In LaMnO3 thin film, we could observe the oscillation until ˜ 1.5 ps. In the superlattices, the damping time constant was smaller: ˜ 0.7 ps for n=8 superlattice and ˜ 0.3 ps for n=2 superlattice. We will discuss number of phonon mode and the damping time constant in terms of the sample geometry and the electronic struncture.

Applied Physics Letters, 2015

We observed ultra-short laser pulse-induced transient optical anisotropy in a LaMnO 3 thin film. ... more We observed ultra-short laser pulse-induced transient optical anisotropy in a LaMnO 3 thin film. The anisotropy was induced by laser pulse irradiation with a fluence of less than 0.1 mJ/cm 2 at room temperature. The transmittance and reflectance showed strong dependence on the polarization states of the pulses. For parallel and perpendicular polarization states, there exists a difference of approximately 0.2% for transmittance and 0.05% for reflectance at 0.3 picoseconds after the irradiation with a pump pulse, respectively. The theoretical values for optical transmittance and reflectance with an assumption of an orbital ordering of 3d e g electrons in Mn 3+ ions showed good agreement with the experimental results, demonstrating that the transient optical anisotropy in LaMnO 3 thin film is due to the photo-induced symmetry-breaking of orbital ordering in excited states.

New Physics: Sae Mulli, 2013

Coherent oscillation modes in LaMnO3/SrTiO3 thin films were observed by using an ultra-short lase... more Coherent oscillation modes in LaMnO3/SrTiO3 thin films were observed by using an ultra-short laser-pulse pump-probe method. The time durations of both the pump and the probe pulses were about 10 femtoseconds. The pulse's center wavelength was about 780 nm which corresponds to about a 1.6-eV photon energy. LaMnO3 is a Mott insulator that is known to be orbitally ordered even at room temperature. A coherent phonon-like oscillation at a higher frequency was expected for the orbital wave response, but signals manifesting the orbital wave was not observed in this experiment. A frequency analysis of the coherent oscillation modes revealed some modes well matched to Raman phonon modes.

Solid State Communications, 2012

We report the transmittance (T) and the pump-probe transmittance change ðDTÞ of Nd 0.5 Sr 0.5 MnO... more We report the transmittance (T) and the pump-probe transmittance change ðDTÞ of Nd 0.5 Sr 0.5 MnO 3 (NSMO) thin films grown on SrTiO 3 (STO)(100) and STO(110) substrates in 1.3-1.7 eV range at room temperature. The strain of NSMO was isotropic on STO(100) and anisotropic on STO(110). Both T and DT showed no polarization dependence in NSMO/STO(100) but the intensity of T and DT was anisotropic in NSMO/STO(110). Also DT showed sharp exponential decay with increasing time delay between the pump and probe pulse. The short time decay behaviour ð t 0:3 psÞ showed no significant polarization direction and substrate dependence, which indicates that the carrier-carrier scattering rate is not sensitive to the strain state in NSMO.

We present the polarization and time dependent transmittance of Nd0.5Sr0.5MnO3 (NSMO) thin films ... more We present the polarization and time dependent transmittance of Nd0.5Sr0.5MnO3 (NSMO) thin films grown on SrTiO3 (STO) (100) and STO (110) substrates. We used the normal transmission technique and the pump-probe technique for the measurement. While the transmittance of NSMO film on STO (100) is isotropic, the transmittance of NSMO on STO (110) measured with the electric field parallel to [-110] direction (E//[-110]) is larger than that of E//[100]. The time dependent transmittance change of NSMO film on STO (100) shows a sharp increase near the zero time delay and exponential decreases as the time delay between the pump and the probe pulse increases. The transmittance change of NSMO film on STO (110) shows almost the same time dependence. The time dependent transmittance change of NSMO film on STO (100) shows no significant polarization direction dependence, however the magnitude of time dependent transmittance change of NSMO on STO (110) is different depending on the polarization d...

Journal of Modern Optics, 2014

ABSTRACT Ultrafast transient optical conductivity of spin-orbital ordered LaMnO3 was investigated... more ABSTRACT Ultrafast transient optical conductivity of spin-orbital ordered LaMnO3 was investigated theoretically. A quasi-two-dimensional Hubbard Hamiltonian based on a four-site Mn cluster was established to simulate the LaMnO3 system. The time evolution of the transient optical conductivity was numerically calculated. Intensity oscillations of the optical conductivity were observed, which were interpreted as the result of the quantum interference between phonon-coupled orbiton excited states. Also, the photo-induced anisotropy was observed, which revealed the broken orbital symmetry of the optical excited state.

Applied Optics, 2013

This paper describes a method to determine the phase retardation of birefringent optical componen... more This paper describes a method to determine the phase retardation of birefringent optical components by combining spectral interferometry and the Fourier transform method. The retardation of each orthogonal polarization component was resolved by using two rotatable linear polarizers in the interferometer. The phase retardation measured by using suggested method was compared to that measured using the conventional polarimetric method. The results of independent methods were well matched, which confirms the validity of the proposed method.

The Korean Physical Society, Nov 1, 2013

Physical Review B, 2018

We calculated the polarization-dependent Raman scattering cross section spectra of LaMnO 3 below ... more We calculated the polarization-dependent Raman scattering cross section spectra of LaMnO 3 below the A-type magnetic ordering temperature. Two strong peaks appear around the MnO 6 octahedra stretching phonon frequency. One mode shows A g symmetry, while the other mode shows B g symmetry. We found that the A g symmetry peak is a Jahn-Teller phonon coupled to the orbital wave and the B g symmetry peak is an orbital wave coupled to a Q 2 phonon mode via the Jahn-Teller electron-phonon coupling.

Solid State Communications, 2021

We calculated the infrared conductivity spectrum of orbitally ordered LaMnO 3 in phonon frequency... more We calculated the infrared conductivity spectrum of orbitally ordered LaMnO 3 in phonon frequency and overtone frequency ranges. We considered orbital exchange, Jahn-Teller electron-phonon coupling, and phonon-phonon coupling. The fundamental excitation of the phonon-coupled orbiton was only Raman active, not infrared active, while its overtone modes were both Raman and infrared active. Our calculations reproduced the small peaks near 1300 cm −1 observed both in Raman scattering and infrared conductivity spectra, as consistent with previous experimental results.

Solid State Phenomena, 2021

We applied the dielectric function method to solve analytically L-NL-L structure problems with ne... more We applied the dielectric function method to solve analytically L-NL-L structure problems with negative Kerr nonlinearity. A damped wave in linear and a periodic standing wave in non-linear media had to be matched at boundaries. We gave a formulation of boundary conditions that did not explicitly include a film thickness. The boundary-value of a dielectric function can be expressed through the constant of non-trivial integral of motion. Using it, one generates a family of matched solutions satisfying boundary conditions. Then arbitrary film thickness can be checked against this family of solutions in search of matches. As a result, all fitted solutions are determined straightforwardly.

IOP Conference Series: Materials Science and Engineering, 2019

The Kerr-lens mode-locking (KLM) is known as a suitable method for generation of femtosecond puls... more The Kerr-lens mode-locking (KLM) is known as a suitable method for generation of femtosecond pulses and mode-locked Ti:sapphire laser is now widely used sources of stable, energetic femtosecond pulses. We will present the simulation of KLM in Ti:sapphire laser cavities with a folded-cavity four-mirror by applying the ABCD ray-tracing technique for a Gaussian beam. Simulations will be performed for an asymmetric resonator design. Based on the numerical analysis, we will find the optimum design parameters (slit position, gain cavity spacing, gain medium position) for KLM.

Optics Communications, 2020

We measured photon absorption in dielectric media and proposed the photon-version Beer-Lambert's ... more We measured photon absorption in dielectric media and proposed the photon-version Beer-Lambert's law to quantify the absorption. We used a Hong-Ou-Mandel interferometer and 810 nm twin-photons. We found that the depth ratio of the null point in the interference patterns of the interferometer agreed with the classical transmittance of the samples. We established a statistical model of the photon absorption process and proposed an information entropy interpretation to understand the meaning of the Beer-Lambert law. Comparisons of the results of the photon absorption experiments with classical experiments demonstrate the validity of our model and interpretation.

Solid State Phenomena, 2019

Two different pump-probe (PP) setups were developed successfully with different femtosecond pulse... more Two different pump-probe (PP) setups were developed successfully with different femtosecond pulse lasers. Using a PP setup with an ultra-short pulse laser, the excitation of coherent phonons in GaAs was measured for a calibration and an accuracy test of the developed setup. The frequencies of the coherent phonon modes were in good agreement with reported values [1, 2]. The setups for ZnSe and GaAs were transmission and reflection–type, respectively. When using the ultra-short pulse laser, the signal in the PP experiment was measured by a balanced photo diode.In the other PP experimental setup, built to measure the transient transmittance of bulk ZnSe, the light source and detector differed from the previous PP setup. A strong pulse laser was successfully used for the spectrally resolved pump probe experimental setup. A broadband, high-resolution spectrometer (HR4000CG-UV-NIR) was used as the detector.

Journal of Modern Optics, 2019

We calculated third order non-linear polarization to estimate the two-photon absorption of non-in... more We calculated third order non-linear polarization to estimate the two-photon absorption of non-interacting two-level molecules in the transmission-type degenerate pump-probe geometry. The spectral intensity and the phase changes of the laser pulses when passing through a thin dielectric slab composed of the molecules were considered. We also investigated the effect of the decay rate of the molecules and the chirp of the pulses on their spectral intensity and phase changes.

Optics Communications, 2017

We propose an excitation-probe measurement method utilizing entangled photon pulses. The excitati... more We propose an excitation-probe measurement method utilizing entangled photon pulses. The excitation-probe signal is dominated by stimulated Raman scattering as well as two-photon absorption when the time delay between the excitation pulse and the probe pulse is shorter than the pulse duration. We demonstrate that the two-photon-absorption signal can be suppressed when the photons of the pulses are entangled. The stimulated Raman scattering signal can be composed of many peaks distributed over broad photon energies owing to the transitions between numerous quantum states in complex materials. We show that the desired peaks among the many peaks can be selected by controlling the thickness of the nonlinear crystal, the pump pulse center frequency, and the polarization of the excitation pulse and probe pulse.

Journal of the Optical Society of Korea, 2012

A polarimetric experimental method was developed to determine the Jones matrix elements of transp... more A polarimetric experimental method was developed to determine the Jones matrix elements of transparent optical materials without sign ambiguity. A set of polarization dependent transmittance data of the samples was measured with polarizersampleanalyzer system and another set of data was measured with polarizersamplequarter-wave plateanalyzer. Two data sets were compared and mathematically analyzed to obtain the correct signs of the elements of the matrix. The Jones matrix elements of a quarter-wave plate were determined to check the validity of the method. The experimentally obtained matrix elements of the quarter-wave plate were consistent with the theoretical expectations. The same method was applied to obtain the Jones matrix elements of a twisted nematic liquid crystal panel.

We present the time dependent transmittance of LaMnO3 thin film and [(LaMnO3)n/(SrTiO3)8]20 (n=2 ... more We present the time dependent transmittance of LaMnO3 thin film and [(LaMnO3)n/(SrTiO3)8]20 (n=2 and 8) superlattices grown on SrTiO3 substrate. We used the laser pulse pump-probe technique. We observed two phonon oscillation in the LaMnO3 film at 8 THz and at 15 THz. In the superlattices, 8 THz mode seemed obliterated. The phonon oscillation damping time constant was also different. In LaMnO3 thin film, we could observe the oscillation until ˜ 1.5 ps. In the superlattices, the damping time constant was smaller: ˜ 0.7 ps for n=8 superlattice and ˜ 0.3 ps for n=2 superlattice. We will discuss number of phonon mode and the damping time constant in terms of the sample geometry and the electronic struncture.

Applied Physics Letters, 2015

We observed ultra-short laser pulse-induced transient optical anisotropy in a LaMnO 3 thin film. ... more We observed ultra-short laser pulse-induced transient optical anisotropy in a LaMnO 3 thin film. The anisotropy was induced by laser pulse irradiation with a fluence of less than 0.1 mJ/cm 2 at room temperature. The transmittance and reflectance showed strong dependence on the polarization states of the pulses. For parallel and perpendicular polarization states, there exists a difference of approximately 0.2% for transmittance and 0.05% for reflectance at 0.3 picoseconds after the irradiation with a pump pulse, respectively. The theoretical values for optical transmittance and reflectance with an assumption of an orbital ordering of 3d e g electrons in Mn 3+ ions showed good agreement with the experimental results, demonstrating that the transient optical anisotropy in LaMnO 3 thin film is due to the photo-induced symmetry-breaking of orbital ordering in excited states.

New Physics: Sae Mulli, 2013

Coherent oscillation modes in LaMnO3/SrTiO3 thin films were observed by using an ultra-short lase... more Coherent oscillation modes in LaMnO3/SrTiO3 thin films were observed by using an ultra-short laser-pulse pump-probe method. The time durations of both the pump and the probe pulses were about 10 femtoseconds. The pulse's center wavelength was about 780 nm which corresponds to about a 1.6-eV photon energy. LaMnO3 is a Mott insulator that is known to be orbitally ordered even at room temperature. A coherent phonon-like oscillation at a higher frequency was expected for the orbital wave response, but signals manifesting the orbital wave was not observed in this experiment. A frequency analysis of the coherent oscillation modes revealed some modes well matched to Raman phonon modes.

Solid State Communications, 2012

We report the transmittance (T) and the pump-probe transmittance change ðDTÞ of Nd 0.5 Sr 0.5 MnO... more We report the transmittance (T) and the pump-probe transmittance change ðDTÞ of Nd 0.5 Sr 0.5 MnO 3 (NSMO) thin films grown on SrTiO 3 (STO)(100) and STO(110) substrates in 1.3-1.7 eV range at room temperature. The strain of NSMO was isotropic on STO(100) and anisotropic on STO(110). Both T and DT showed no polarization dependence in NSMO/STO(100) but the intensity of T and DT was anisotropic in NSMO/STO(110). Also DT showed sharp exponential decay with increasing time delay between the pump and probe pulse. The short time decay behaviour ð t 0:3 psÞ showed no significant polarization direction and substrate dependence, which indicates that the carrier-carrier scattering rate is not sensitive to the strain state in NSMO.

We present the polarization and time dependent transmittance of Nd0.5Sr0.5MnO3 (NSMO) thin films ... more We present the polarization and time dependent transmittance of Nd0.5Sr0.5MnO3 (NSMO) thin films grown on SrTiO3 (STO) (100) and STO (110) substrates. We used the normal transmission technique and the pump-probe technique for the measurement. While the transmittance of NSMO film on STO (100) is isotropic, the transmittance of NSMO on STO (110) measured with the electric field parallel to [-110] direction (E//[-110]) is larger than that of E//[100]. The time dependent transmittance change of NSMO film on STO (100) shows a sharp increase near the zero time delay and exponential decreases as the time delay between the pump and the probe pulse increases. The transmittance change of NSMO film on STO (110) shows almost the same time dependence. The time dependent transmittance change of NSMO film on STO (100) shows no significant polarization direction dependence, however the magnitude of time dependent transmittance change of NSMO on STO (110) is different depending on the polarization d...

Journal of Modern Optics, 2014

ABSTRACT Ultrafast transient optical conductivity of spin-orbital ordered LaMnO3 was investigated... more ABSTRACT Ultrafast transient optical conductivity of spin-orbital ordered LaMnO3 was investigated theoretically. A quasi-two-dimensional Hubbard Hamiltonian based on a four-site Mn cluster was established to simulate the LaMnO3 system. The time evolution of the transient optical conductivity was numerically calculated. Intensity oscillations of the optical conductivity were observed, which were interpreted as the result of the quantum interference between phonon-coupled orbiton excited states. Also, the photo-induced anisotropy was observed, which revealed the broken orbital symmetry of the optical excited state.

Applied Optics, 2013

This paper describes a method to determine the phase retardation of birefringent optical componen... more This paper describes a method to determine the phase retardation of birefringent optical components by combining spectral interferometry and the Fourier transform method. The retardation of each orthogonal polarization component was resolved by using two rotatable linear polarizers in the interferometer. The phase retardation measured by using suggested method was compared to that measured using the conventional polarimetric method. The results of independent methods were well matched, which confirms the validity of the proposed method.