Viktoras Vaicikauskas - Academia.edu (original) (raw)

Papers by Viktoras Vaicikauskas

Applied Sciences, 2020

In the present work we reveal the existence of the hot carrier photovoltage induced across a p–n ... more In the present work we reveal the existence of the hot carrier photovoltage induced across a p–n junction in addition to the classical carrier generation-induced and thermalization-caused photovoltages. On the basis of the solution of the differential equation of the first-order linear time-invariant system, we propose a model enabling to disclose the pure value of each photovoltage component. The hot carrier photovoltage is fast since it is determined by the free carrier energy relaxation time (which is of the order of 10−12 s), while the thermal one, being conditioned by the junction temperature change, is relatively slow; and both of them have a sign opposite to that of the electron-hole pair generation-induced component. Simultaneous coexistence of the components is evidenced experimentally in GaAs p–n junction exposed to pulsed 1.06 μm laser light. The work is remarkable in two ways: first, it shows that creation of conditions unfavorable for the rise of hot carrier photovoltag...

Coatings

We report a systematic nanoscale investigation on the ultrathin Cr film growth process and proper... more We report a systematic nanoscale investigation on the ultrathin Cr film growth process and properties. Polycrystalline metallic films were manufactured by magnetron sputtering on fused silica substrates. The film growth was observed in situ by broad-band optical monitoring (BBM) and plasma-emission spectroscopy (OES) methods. The ex situ characterization of the Cr films with thicknesses varying from 2.6 nm up to 57 nm were performed by both non-destructive and destructive techniques. Recently, we reported on a novel set of data for optical and electrical properties of sputtered chromium films. The optical and electrical properties of the films are known to be governed by their structure and microstructure, which were analyzed in detail in the present research. Moreover, the optical properties of the films were studied here in a significantly wider optical range and obtained using both in situ and ex situ measurements. Reliable in situ nanoscale characterization of metal films was sh...

Smart Optical Inorganic Structures and Devices, 2001

The cut-off effect in slightly asymmetric systems prevent the wider practical usage of long range... more The cut-off effect in slightly asymmetric systems prevent the wider practical usage of long range surface polaritons (LRSP) in the infrared region. Due to asymmetry caused by the presence of even a few nanometers wide air gap the LRSP mode disappear. We propose a solution of this problem by using an effective medium approach. The basic idea is to compensate for the air gap induced asymmetry by introducing an additional layer into the system. That allows us to shift the cut-off to values sufficiently for experimental observation of LRSP. FTIR spectra of end-fire coupled LRSPs in the GaAs/Au/GaAs multilayer system were measured in the (800-3000) cm-1 range. Various geometric and polarization sensitive effects of the infrared system capable of influencing the LRSP coupling is discussed. A pronounced increase in the p and s polarized light transmission ratio at long-wavelengths is explained as an increase in the propagation distance L of LRSPs. A fairly good fit between experimental and calculated curves was achieved at long wavelengths. The width of the air gap was used as a parameter in the calculations.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

SPIE Proceedings, 1997

In2O3(Sn) film CO senors in the Kretschmann configuration were investigated using a rotating anal... more In2O3(Sn) film CO senors in the Kretschmann configuration were investigated using a rotating analyzer spectrometer. From the experimental surface plasmon resonance (SPR) angular dependencies, applying the best fit method complex dielectric permitivity of In2O3(Sn) films ((epsilon) equals 2.4-i0.2) were obtained. Under exposition of sensor by CO gas at 134 degrees Celsius temperature, SPR shifted to higher angles and sufficiently broadened. Most significant change possesses an imaginary part of dielectric permitivity -- after 0.8% CO exposition it becomes 4.1, whereas a real part equals to 1.2.

Surface electromagnetic waves (SEW) due to their unique fielddistribution (field maximum occurs a... more Surface electromagnetic waves (SEW) due to their unique fielddistribution (field maximum occurs at the two adjacent mediainterface) is a highly sensitive instrument for studying both metalsurfaces and thin films on them. The experimentally measurableparameters in SEW experiments are the SEW propagation distance L(14=1/4m)n—) and the real part of SEW refraction index n'ef efC C i/2i 2)). For metals in middle and far infrared region y,ef C +ci 2u01..) (p , - - plasmon frequency and damping constant) n' is directlyP p efdetermined by plasma frequency. Therefore, the difference between thelight line k =())/c and the surface polariton dispersion curve0k =w/chi is insignificant and in such circumstances the measurement$p efof n' is problematic. Usually it is measured by scanningefinterference pattern of bulk radiation with SEW launched on thesample edge [1]. In the FIR region SEW propagation distance on metalsis too large (a few meters) and transparent films are sputter...

LAMILADIS '91 Intl Workshop: Laser Microtechnology and Laser Diagnostics of Surfaces, 1992

Experimental results of FIR ((nu) equals 85 - 142 cm-1) surface electromagnetic wave propagation ... more Experimental results of FIR ((nu) equals 85 - 142 cm-1) surface electromagnetic wave propagation in n-type semiconductors (InSb, GBaAs, InP) and ferroelectric films BaxSr1-xTiO3 are presented. A technique for measuring the plasma frequency (nu) p and the damping constant of plasmons (gamma) (or the concentration and relaxation time of electrons) in doped semiconductors was designed. The SEW propagation distance dependence on electron concentration in GaAs has been obtained. The relationship between the SEW propagation distance L and the 'soft mode' parameters in ferroelectric films was found. In the L dependence on temperature the minimum was observed at T equals 380 K in BaxSr1-xTiO3, which is explained by the increase of dielectric losses tan (delta) in the film under phase transition.

Lithuanian Journal of Physics, 2008

The difference frequency generation in the AgGaSe2 crystal between output waves of a periodically... more The difference frequency generation in the AgGaSe2 crystal between output waves of a periodically poled MgO doped lithium niobate (PP-MgO : LN) optical parametric oscillator (OPO) is described in this paper. The wavelength of the generated radiation is tunable from 6 to 13 µm with the average generated power in the range of several microwatts. The setup allows a rapid tuning of the wavelength in the limited region of spectra without changing the temperature of the PP-MgO : LN crystal. A typical spectral linewidth of 5 cm −1 makes this source suitable for spectrometry of complex molecules under atmospheric conditions. The measured spectrum of the acetone vapour is presented to confirm this fact.

Lithuanian Journal of Physics, 2007

The surface plasmon resonance (SPR) method combined with spectral ellipsometry was used to study ... more The surface plasmon resonance (SPR) method combined with spectral ellipsometry was used to study the chemically formed octadecanthiol (ODT) monolayer on a gold film in Kretchmann configuration. Measurements were made with a commercial spectral ellipsometer GES-5 (SOPRA). The optical constants of an Au film and ODT at 1000 nm wavelength were determined by the best fit procedure from experimental data (Au: n = 0.202, k = 5.970 and ODT: n = 1.4, k = 0). Combination of the SPR method with advantages of phase measurements of ellipsometry demonstrated a substantial increase in sensitivity (more than one order of magnitude) compared with conventional ellipsometry.

Lithuanian Journal of Physics, 2006

The surface plasmon resonance method was used for determination of 9-(5'-ferrocenylpentanoyloxy) ... more The surface plasmon resonance method was used for determination of 9-(5'-ferrocenylpentanoyloxy) nonyl disulfide (FPONDS) and lipase thin film thicknesses and optical constants. Surface plasmons were excited in the Kretchmann configuration on the thin 50 nm gold film on the BK7 or SF10 glass prism. Sufficient sensitivity of the method for investigation of lipase interaction with a thin FPONDS layer (d = 2.9 nm) kinetics was demonstrated. From the experimental plasmon minimum shift to higher angles it could be concluded that lipase is adsorbed on the FPONDS and as a result it causes an increase in the effective layer thickness. The obtained results are important in understanding the interaction of these molecules, determination of their size and distribution on the surface.

2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008

Transients of an InGaAs-based bow-tie diode with broken symmetry are experimentally investigated.... more Transients of an InGaAs-based bow-tie diode with broken symmetry are experimentally investigated. The 100 MHz bandwidth low-noise preamplifier is designed and successfully adapted. The main peculiarities of the terahertz detector are detection in passive scheme, flat frequency response up to 1 THz, the voltage sensitivity of about 5 V/W, and the rise time less than 40 ns.

SPIE Proceedings, 2004

We describe a new project (acronym LISATNAS) approved by the Lithuanian Research Council in 2003 ... more We describe a new project (acronym LISATNAS) approved by the Lithuanian Research Council in 2003 devoted to the development of differential absorption lidar (DIAL) and stationary spectrometric systems based on the mid-infrared tunable Optical Parametric Oscillator (OPO), pumped by compact Q-switched lasers. The purpose of the project is to construct a mobile infrared lidar, assembled in the truck for selective pollutant analysis - possessing spatial resolution of a few meters in the distance range extending from hundred of meters to a few kilometers. A reliable cascade mid-IR generation scheme was developed. Pulse energies up to milijoule in mid-IR have been already obtained using nonlinear AgGaSe2 crystal. Optoacoustic and multipass cells were constructed for stationary spectrometers. Preliminary results with detection of CO2, CH4, H2O and other gases in the ppm concentration range show good sensitivity. Special pollutants were synthesized by chemical group of the project for spectrometric experiments: multiatomic nitrocompounds, such as trinitrotoluen (TNT) or trotyl, DNT (dinitrotoluoen), MNT (mononitrotoluoen) and RDX (heksahydro-1.3.5-triazyn). The mobile DIAL system based on the tunable laser in the 8-12 μm region, 10" goldmirror telescope, MCT cooled detector with control electronics is under construction and should be finished in 2005.

Thin Solid Films, 2005

The cutoff effect in slightly asymmetric systems prevents the wider practical usage of long-range... more The cutoff effect in slightly asymmetric systems prevents the wider practical usage of long-range surface polaritons (LRSP). Due to asymmetry caused by the presence of even a few nanometers wide air gap, the LRSP mode disappears. We propose a solution to this problem by using an effective medium approach. The basic idea is to compensate for the air gap induced asymmetry by introducing an additional layer into the system. That allows us to shift the cutoff to values sufficient for experimental observation of LRSP. Fourier transform infrared spectra of end-fire coupled LRSP in the GaAs/Au/GaAs multilayer system were measured in the (800-3000) cm À1 range. Various geometric and polarization sensitive effects of the infrared system capable of influencing the LRSP coupling are discussed. A pronounced increase in the p-polarized light transmission at long-wavelengths is explained as an increase in the propagation distance L of LRSP. A fairly good fit between experimental and calculated curves was achieved at long wavelengths.

International Journal of Infrared and Millimeter Waves, 1994

International Journal of Infrared and Millimeter Waves, 1991

The results of YBa2Cu3O7-x films on SrTiO3 investigation by far infrared surface electromagnetic ... more The results of YBa2Cu3O7-x films on SrTiO3 investigation by far infrared surface electromagnetic waves (SEW) amplitude and phase spectroscopy at temperatures 80–350 K are presented. Strong SEW absorption at frequency 142 cm-1 has been observed. The origin of the observed absorbtion is proposed to be concerned with slab- phonons in YBa2Cu3O7-x. The optical constants of the films have been obtained. Also has been determined, that only the imaginary part of the SEW refraction index changes when the film transits into superconducting state, while the real part remains unchanged.

Infrared Physics & Technology, 1995

The results of investigation of low-frequency modes in SrTiO 3 crystals by FIR surface electromag... more The results of investigation of low-frequency modes in SrTiO 3 crystals by FIR surface electromagnetic waves (SEW) are presented. Amplitude and phase spectroscopy methods, including SEW heterodying for the complex SEW refraction index nef measurements at temperatures of 80-300 K were applied. The SEW method appears to be convenient for the soft mode (SM) frequency and damping measurements and advantages against other methods are discussed. The possible reasons of disagreement of SEW damping values at v = 84 cm-t obtained by us and others are discussed. Sharp increase of SEW damping at this frequency when temperature increases was explained by transition of Fano type mode (v < Vro) to Zenneck-Sommerfeld one (v > VTO) with sufficiently larger damping. At liquid N temperature SM frequency take the value of 43 cm ~. It sufficiently well agrees with the one obtained by hyper-Raman and IRR methods. Preliminary experiments with ferroelectric Ba~Sr~ ~TiO 3 and superconducting YBa2Cu307_ • thin films on SrTiO3 showed the SEW sensitivity to the phase transitions of films. The maximum of SEW damping in Ba~Sr~ ,TiO 3 at the phase transition temperature was obtained. The plasma frequency vp as well as electron collisional frequency v~ in Y Ba2Cu30~ , was obtained (Vp = 104 cm-I vt = 3000 cm-i at 300 K).

Applied Optics, 2006

A time-resolved reflection pump-probe method was combined with a surface plasmon resonance techni... more A time-resolved reflection pump-probe method was combined with a surface plasmon resonance technique in Kretschmann geometry for the investigation of ultrafast light-induced processes in thin films. Transient changes in the gold layer's reflectivity were observed when the layer was excited by 3 ps duration pulses with photon energy exceeding the interband transition and by probing with photon energy close to the interband transition. Comparison of the experimental and modeling results has shown that the imaginary part of the dielectric function of gold increases linearly during excitation, whereas the real part remains unchanged. The decay of the light-induced changes has two components. The first component is faster than the pulse duration, and the second is much longer than 1.5 ns; they are related to cooling of the electron plasma and lattice, respectively.

Lithuanian Journal of Physics, 2007

A differential absorption lidar system for detection of atmospheric pollutants based on the middl... more A differential absorption lidar system for detection of atmospheric pollutants based on the middle infrared tandem optical parametric oscillator is presented. The characteristics of the signal obtained by detecting radiation backscattered from different topographical objects were measured in the field test of the system. These characteristics were used to calculate the minimum detectable concentration of several atmospheric pollutants: ozone, methane, ammonia, etc. Most of the gases can be detected below typical background concentrations for the low-polluted atmosphere.

Laser Radar Technology and Applications XI, 2006

We describe all solid state differential absorption lidar (DIAL) based on the mid-infrared (IR) t... more We describe all solid state differential absorption lidar (DIAL) based on the mid-infrared (IR) tunable Optical Parametric Oscillator (OPO). Generation of tunable mid-infrared laser radiation using a two stage tandem OPO was demonstrated. The first stage was based on the nonlinear KTP crystal and produced up to 45 mJ of 1.57 µ m radiation, while pumped by a commercial Q-switched Nd:YAG laser. The quality of signal beam was improved by the use of unstable resonator. The AgGaSe 2 crystal was used in the second stage OPO. Idler energies up to 1 mJ were generated at this stage within tuning range from 6 to 12 µ m. The receiver consisted of a 250 mm gold mirror telescope, two channel detection system and control electronics. We have designed a photoacoustic cell for wavelength calibration of lidar. Preliminary lidar field test results are presented.

The Surface Electromagnetic waves method was applied for determination of plasma frequency and pu... more The Surface Electromagnetic waves method was applied for determination of plasma frequency and pulse relaxation time in doped A 3 B 5 semiconductors. The influence of plasmon phonon interaction, nonparabolity of the conduction band, electron scattering peculiarities, presence of disturbed layers are under consideration.

Applied Sciences, 2020

In the present work we reveal the existence of the hot carrier photovoltage induced across a p–n ... more In the present work we reveal the existence of the hot carrier photovoltage induced across a p–n junction in addition to the classical carrier generation-induced and thermalization-caused photovoltages. On the basis of the solution of the differential equation of the first-order linear time-invariant system, we propose a model enabling to disclose the pure value of each photovoltage component. The hot carrier photovoltage is fast since it is determined by the free carrier energy relaxation time (which is of the order of 10−12 s), while the thermal one, being conditioned by the junction temperature change, is relatively slow; and both of them have a sign opposite to that of the electron-hole pair generation-induced component. Simultaneous coexistence of the components is evidenced experimentally in GaAs p–n junction exposed to pulsed 1.06 μm laser light. The work is remarkable in two ways: first, it shows that creation of conditions unfavorable for the rise of hot carrier photovoltag...

Coatings

We report a systematic nanoscale investigation on the ultrathin Cr film growth process and proper... more We report a systematic nanoscale investigation on the ultrathin Cr film growth process and properties. Polycrystalline metallic films were manufactured by magnetron sputtering on fused silica substrates. The film growth was observed in situ by broad-band optical monitoring (BBM) and plasma-emission spectroscopy (OES) methods. The ex situ characterization of the Cr films with thicknesses varying from 2.6 nm up to 57 nm were performed by both non-destructive and destructive techniques. Recently, we reported on a novel set of data for optical and electrical properties of sputtered chromium films. The optical and electrical properties of the films are known to be governed by their structure and microstructure, which were analyzed in detail in the present research. Moreover, the optical properties of the films were studied here in a significantly wider optical range and obtained using both in situ and ex situ measurements. Reliable in situ nanoscale characterization of metal films was sh...

Smart Optical Inorganic Structures and Devices, 2001

The cut-off effect in slightly asymmetric systems prevent the wider practical usage of long range... more The cut-off effect in slightly asymmetric systems prevent the wider practical usage of long range surface polaritons (LRSP) in the infrared region. Due to asymmetry caused by the presence of even a few nanometers wide air gap the LRSP mode disappear. We propose a solution of this problem by using an effective medium approach. The basic idea is to compensate for the air gap induced asymmetry by introducing an additional layer into the system. That allows us to shift the cut-off to values sufficiently for experimental observation of LRSP. FTIR spectra of end-fire coupled LRSPs in the GaAs/Au/GaAs multilayer system were measured in the (800-3000) cm-1 range. Various geometric and polarization sensitive effects of the infrared system capable of influencing the LRSP coupling is discussed. A pronounced increase in the p and s polarized light transmission ratio at long-wavelengths is explained as an increase in the propagation distance L of LRSPs. A fairly good fit between experimental and calculated curves was achieved at long wavelengths. The width of the air gap was used as a parameter in the calculations.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

SPIE Proceedings, 1997

In2O3(Sn) film CO senors in the Kretschmann configuration were investigated using a rotating anal... more In2O3(Sn) film CO senors in the Kretschmann configuration were investigated using a rotating analyzer spectrometer. From the experimental surface plasmon resonance (SPR) angular dependencies, applying the best fit method complex dielectric permitivity of In2O3(Sn) films ((epsilon) equals 2.4-i0.2) were obtained. Under exposition of sensor by CO gas at 134 degrees Celsius temperature, SPR shifted to higher angles and sufficiently broadened. Most significant change possesses an imaginary part of dielectric permitivity -- after 0.8% CO exposition it becomes 4.1, whereas a real part equals to 1.2.

Surface electromagnetic waves (SEW) due to their unique fielddistribution (field maximum occurs a... more Surface electromagnetic waves (SEW) due to their unique fielddistribution (field maximum occurs at the two adjacent mediainterface) is a highly sensitive instrument for studying both metalsurfaces and thin films on them. The experimentally measurableparameters in SEW experiments are the SEW propagation distance L(14=1/4m)n—) and the real part of SEW refraction index n'ef efC C i/2i 2)). For metals in middle and far infrared region y,ef C +ci 2u01..) (p , - - plasmon frequency and damping constant) n' is directlyP p efdetermined by plasma frequency. Therefore, the difference between thelight line k =())/c and the surface polariton dispersion curve0k =w/chi is insignificant and in such circumstances the measurement$p efof n' is problematic. Usually it is measured by scanningefinterference pattern of bulk radiation with SEW launched on thesample edge [1]. In the FIR region SEW propagation distance on metalsis too large (a few meters) and transparent films are sputter...

LAMILADIS '91 Intl Workshop: Laser Microtechnology and Laser Diagnostics of Surfaces, 1992

Experimental results of FIR ((nu) equals 85 - 142 cm-1) surface electromagnetic wave propagation ... more Experimental results of FIR ((nu) equals 85 - 142 cm-1) surface electromagnetic wave propagation in n-type semiconductors (InSb, GBaAs, InP) and ferroelectric films BaxSr1-xTiO3 are presented. A technique for measuring the plasma frequency (nu) p and the damping constant of plasmons (gamma) (or the concentration and relaxation time of electrons) in doped semiconductors was designed. The SEW propagation distance dependence on electron concentration in GaAs has been obtained. The relationship between the SEW propagation distance L and the 'soft mode' parameters in ferroelectric films was found. In the L dependence on temperature the minimum was observed at T equals 380 K in BaxSr1-xTiO3, which is explained by the increase of dielectric losses tan (delta) in the film under phase transition.

Lithuanian Journal of Physics, 2008

The difference frequency generation in the AgGaSe2 crystal between output waves of a periodically... more The difference frequency generation in the AgGaSe2 crystal between output waves of a periodically poled MgO doped lithium niobate (PP-MgO : LN) optical parametric oscillator (OPO) is described in this paper. The wavelength of the generated radiation is tunable from 6 to 13 µm with the average generated power in the range of several microwatts. The setup allows a rapid tuning of the wavelength in the limited region of spectra without changing the temperature of the PP-MgO : LN crystal. A typical spectral linewidth of 5 cm −1 makes this source suitable for spectrometry of complex molecules under atmospheric conditions. The measured spectrum of the acetone vapour is presented to confirm this fact.

Lithuanian Journal of Physics, 2007

The surface plasmon resonance (SPR) method combined with spectral ellipsometry was used to study ... more The surface plasmon resonance (SPR) method combined with spectral ellipsometry was used to study the chemically formed octadecanthiol (ODT) monolayer on a gold film in Kretchmann configuration. Measurements were made with a commercial spectral ellipsometer GES-5 (SOPRA). The optical constants of an Au film and ODT at 1000 nm wavelength were determined by the best fit procedure from experimental data (Au: n = 0.202, k = 5.970 and ODT: n = 1.4, k = 0). Combination of the SPR method with advantages of phase measurements of ellipsometry demonstrated a substantial increase in sensitivity (more than one order of magnitude) compared with conventional ellipsometry.

Lithuanian Journal of Physics, 2006

The surface plasmon resonance method was used for determination of 9-(5'-ferrocenylpentanoyloxy) ... more The surface plasmon resonance method was used for determination of 9-(5'-ferrocenylpentanoyloxy) nonyl disulfide (FPONDS) and lipase thin film thicknesses and optical constants. Surface plasmons were excited in the Kretchmann configuration on the thin 50 nm gold film on the BK7 or SF10 glass prism. Sufficient sensitivity of the method for investigation of lipase interaction with a thin FPONDS layer (d = 2.9 nm) kinetics was demonstrated. From the experimental plasmon minimum shift to higher angles it could be concluded that lipase is adsorbed on the FPONDS and as a result it causes an increase in the effective layer thickness. The obtained results are important in understanding the interaction of these molecules, determination of their size and distribution on the surface.

2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008

Transients of an InGaAs-based bow-tie diode with broken symmetry are experimentally investigated.... more Transients of an InGaAs-based bow-tie diode with broken symmetry are experimentally investigated. The 100 MHz bandwidth low-noise preamplifier is designed and successfully adapted. The main peculiarities of the terahertz detector are detection in passive scheme, flat frequency response up to 1 THz, the voltage sensitivity of about 5 V/W, and the rise time less than 40 ns.

SPIE Proceedings, 2004

We describe a new project (acronym LISATNAS) approved by the Lithuanian Research Council in 2003 ... more We describe a new project (acronym LISATNAS) approved by the Lithuanian Research Council in 2003 devoted to the development of differential absorption lidar (DIAL) and stationary spectrometric systems based on the mid-infrared tunable Optical Parametric Oscillator (OPO), pumped by compact Q-switched lasers. The purpose of the project is to construct a mobile infrared lidar, assembled in the truck for selective pollutant analysis - possessing spatial resolution of a few meters in the distance range extending from hundred of meters to a few kilometers. A reliable cascade mid-IR generation scheme was developed. Pulse energies up to milijoule in mid-IR have been already obtained using nonlinear AgGaSe2 crystal. Optoacoustic and multipass cells were constructed for stationary spectrometers. Preliminary results with detection of CO2, CH4, H2O and other gases in the ppm concentration range show good sensitivity. Special pollutants were synthesized by chemical group of the project for spectrometric experiments: multiatomic nitrocompounds, such as trinitrotoluen (TNT) or trotyl, DNT (dinitrotoluoen), MNT (mononitrotoluoen) and RDX (heksahydro-1.3.5-triazyn). The mobile DIAL system based on the tunable laser in the 8-12 μm region, 10" goldmirror telescope, MCT cooled detector with control electronics is under construction and should be finished in 2005.

Thin Solid Films, 2005

The cutoff effect in slightly asymmetric systems prevents the wider practical usage of long-range... more The cutoff effect in slightly asymmetric systems prevents the wider practical usage of long-range surface polaritons (LRSP). Due to asymmetry caused by the presence of even a few nanometers wide air gap, the LRSP mode disappears. We propose a solution to this problem by using an effective medium approach. The basic idea is to compensate for the air gap induced asymmetry by introducing an additional layer into the system. That allows us to shift the cutoff to values sufficient for experimental observation of LRSP. Fourier transform infrared spectra of end-fire coupled LRSP in the GaAs/Au/GaAs multilayer system were measured in the (800-3000) cm À1 range. Various geometric and polarization sensitive effects of the infrared system capable of influencing the LRSP coupling are discussed. A pronounced increase in the p-polarized light transmission at long-wavelengths is explained as an increase in the propagation distance L of LRSP. A fairly good fit between experimental and calculated curves was achieved at long wavelengths.

International Journal of Infrared and Millimeter Waves, 1994

International Journal of Infrared and Millimeter Waves, 1991

The results of YBa2Cu3O7-x films on SrTiO3 investigation by far infrared surface electromagnetic ... more The results of YBa2Cu3O7-x films on SrTiO3 investigation by far infrared surface electromagnetic waves (SEW) amplitude and phase spectroscopy at temperatures 80–350 K are presented. Strong SEW absorption at frequency 142 cm-1 has been observed. The origin of the observed absorbtion is proposed to be concerned with slab- phonons in YBa2Cu3O7-x. The optical constants of the films have been obtained. Also has been determined, that only the imaginary part of the SEW refraction index changes when the film transits into superconducting state, while the real part remains unchanged.

Infrared Physics & Technology, 1995

The results of investigation of low-frequency modes in SrTiO 3 crystals by FIR surface electromag... more The results of investigation of low-frequency modes in SrTiO 3 crystals by FIR surface electromagnetic waves (SEW) are presented. Amplitude and phase spectroscopy methods, including SEW heterodying for the complex SEW refraction index nef measurements at temperatures of 80-300 K were applied. The SEW method appears to be convenient for the soft mode (SM) frequency and damping measurements and advantages against other methods are discussed. The possible reasons of disagreement of SEW damping values at v = 84 cm-t obtained by us and others are discussed. Sharp increase of SEW damping at this frequency when temperature increases was explained by transition of Fano type mode (v < Vro) to Zenneck-Sommerfeld one (v > VTO) with sufficiently larger damping. At liquid N temperature SM frequency take the value of 43 cm ~. It sufficiently well agrees with the one obtained by hyper-Raman and IRR methods. Preliminary experiments with ferroelectric Ba~Sr~ ~TiO 3 and superconducting YBa2Cu307_ • thin films on SrTiO3 showed the SEW sensitivity to the phase transitions of films. The maximum of SEW damping in Ba~Sr~ ,TiO 3 at the phase transition temperature was obtained. The plasma frequency vp as well as electron collisional frequency v~ in Y Ba2Cu30~ , was obtained (Vp = 104 cm-I vt = 3000 cm-i at 300 K).

Applied Optics, 2006

A time-resolved reflection pump-probe method was combined with a surface plasmon resonance techni... more A time-resolved reflection pump-probe method was combined with a surface plasmon resonance technique in Kretschmann geometry for the investigation of ultrafast light-induced processes in thin films. Transient changes in the gold layer's reflectivity were observed when the layer was excited by 3 ps duration pulses with photon energy exceeding the interband transition and by probing with photon energy close to the interband transition. Comparison of the experimental and modeling results has shown that the imaginary part of the dielectric function of gold increases linearly during excitation, whereas the real part remains unchanged. The decay of the light-induced changes has two components. The first component is faster than the pulse duration, and the second is much longer than 1.5 ns; they are related to cooling of the electron plasma and lattice, respectively.

Lithuanian Journal of Physics, 2007

A differential absorption lidar system for detection of atmospheric pollutants based on the middl... more A differential absorption lidar system for detection of atmospheric pollutants based on the middle infrared tandem optical parametric oscillator is presented. The characteristics of the signal obtained by detecting radiation backscattered from different topographical objects were measured in the field test of the system. These characteristics were used to calculate the minimum detectable concentration of several atmospheric pollutants: ozone, methane, ammonia, etc. Most of the gases can be detected below typical background concentrations for the low-polluted atmosphere.

Laser Radar Technology and Applications XI, 2006

We describe all solid state differential absorption lidar (DIAL) based on the mid-infrared (IR) t... more We describe all solid state differential absorption lidar (DIAL) based on the mid-infrared (IR) tunable Optical Parametric Oscillator (OPO). Generation of tunable mid-infrared laser radiation using a two stage tandem OPO was demonstrated. The first stage was based on the nonlinear KTP crystal and produced up to 45 mJ of 1.57 µ m radiation, while pumped by a commercial Q-switched Nd:YAG laser. The quality of signal beam was improved by the use of unstable resonator. The AgGaSe 2 crystal was used in the second stage OPO. Idler energies up to 1 mJ were generated at this stage within tuning range from 6 to 12 µ m. The receiver consisted of a 250 mm gold mirror telescope, two channel detection system and control electronics. We have designed a photoacoustic cell for wavelength calibration of lidar. Preliminary lidar field test results are presented.

The Surface Electromagnetic waves method was applied for determination of plasma frequency and pu... more The Surface Electromagnetic waves method was applied for determination of plasma frequency and pulse relaxation time in doped A 3 B 5 semiconductors. The influence of plasmon phonon interaction, nonparabolity of the conduction band, electron scattering peculiarities, presence of disturbed layers are under consideration.