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Optical second harmonic generation in the centrosymmetric magnetic semiconductors EuTe and EuSe

KAMINSKI, B.; LAFRENTZ, M.; PISAREV, R. V.; YAKOVLEV, D. R.; PAVLOV, V. V.; LUKOSHKIN, V. A.; Henriques, Andre Bohomoletz; SPRINGHOLZ, G.; BAUER, G.; ABRAMOF, E.; RAPPL, P. H. O.; BAYER, M.
Fonte: AMER PHYSICAL SOC Publicador: AMER PHYSICAL SOC
Tipo: Artigo de Revista Científica
ENG
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The magnetic europium chalcogenide semiconductors EuTe and EuSe are investigated by the spectroscopy of second harmonic generation (SHG) in the vicinity of the optical band gap formed by transitions involving the 4f and 5d electronic orbitals of the magnetic Eu(2+) ions. In these materials with centrosymmetric crystal lattice the electric-dipole SHG process is symmetry forbidden so that no signal is observed in zero magnetic field. Signal appears, however, in applied magnetic field with the SHG intensity being proportional to the square of magnetization. The magnetic field and temperature dependencies of the induced SHG allow us to introduce a type of nonlinear optical susceptibility determined by the magnetic-dipole contribution in combination with a spontaneous or induced magnetization. The experimental results can be described qualitatively by a phenomenological model based on a symmetry analysis and are in good quantitative agreement with microscopic model calculations accounting for details of the electronic energy and spin structure.; DFG - Deutsche Forschungsgemeinschaft[YA65/4-1]; RFBR Russian Foundation for Basic Research; European Science Foundation; FAPESP; CNPq; (DAAD) Deutscher Akademischer Austausch Dienst, Germany; FWF (Vienna...

Theory of near-gap second harmonic generation in centrosymmetric magnetic semiconductors: Europium chalcogenides

Henriques, Andre Bohomoletz; ABRAMOF, E.; RAPPL, P. H. O.
Fonte: AMER PHYSICAL SOC Publicador: AMER PHYSICAL SOC
Tipo: Artigo de Revista Científica
ENG
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Second harmonic generation is strictly forbidden in centrosymmetric materials, within the electric dipole approximation. Recently, it was found that the centrosymmetric magnetic semiconductors EuTe and EuSe can generate near-gap second harmonics, if the system is submitted to an external magnetic field. Here, a theoretical model is presented, which well describes the observed phenomena. The model shows that second harmonic generation becomes efficient when the magnetic dipole oscillations between the band-edge excited states of the system, induced by the excitation light, enter the in-phase regime, which can be achieved by applying a magnetic field to the material.; FAPESP; CNPq; (DAAD) Deutscher Akademischer Austausch Dienst, Germany

Estudo da orientação molecular em filmes automontados de azopolímeros por meio da técnica de geração de segundo harmônico (SHG); Molecular orientation in self-assembled azo-polymer thin films studied by second harmonic generation (SHG).

Lopes, Fábio Juliano da Silva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/08/2006 PT
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Filmes ultrafinos de polímeros que contém azocromóforos são importantes para muitas aplicações como armazenamento óptico, formação de grades de relevo superficiais, alinhamento de camadas de cristal líquido e dispositivos ópticos com propriedades não-lineares. Dentre as muitas técnicas de fabricação de filmes orgânicos ultrafinos, a técnica de Automontagem eletrostática camada a camada (Layer-by-Layer, LBL) é muito atrativa devido a sua simplicidade e versatilidade, permitindo o controle na espessura e na composição dos filmes em escalas nanométricas. Contudo, a completa caracterização estrutural de tais filmes enfrenta dificuldades devido à falta de técnicas experimentais apropriadas. Utilizamos a Geração de Segundo Harmônico (SHG) para estudar a orientação molecular de filmes automontados de um polieletrólito catiônico (PAH - Poli(alilamina hidroclorada)) e um polieletrólito aniônico contendo azocromóforos como grupos laterais (Ma-co-DR13) sobre substrato de vidro. O sinal de SHG é proporcional à susceptibilidade não-linear de segunda ordem do filme, que por sua vez depende da distribuição orientacional dos azocromóforos nesse filme. Os resultados indicam que existem uma orientação preferencial dos azocromóforos...

Desenvolvimento de lasers no azul, a partir da geração de segundo harmônico de um laser de Nd:YAG operando em 946 nm; DEVELOPMENT OF BLUE LASERS, FROM SECOND HARMONIC GENERATION USING A Nd:YAG LASER EMITTING AT 946 nm

Nogueira, Gustavo Bernardes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/10/2010 PT
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Lasers emitindo no azul vêm sendo largamente utilizado em diversas aplicações como por exemplo, blu-ray, displays, e podem representar uma excelente fonte de bombeio para o meio ativo Ti:safira. Neste trabalho utilizamos um cristal de Nd:YAG, com diffusion bonded end-caps e um bombeamento com diodo semicondutor no comprimento de onda de 803,2 nm, dessintonizado do pico de absorção 808 nm de neodímio, a fim de minimizar os efeitos de lente térmica do Nd:YAG. Dessa forma, conseguiu-se uma melhor distribuição de temperatura dentro do cristal. Testando diferentes raios de curvatura para os espelhos da cavidade, obteve-se a melhor relação entre a cintura do feixe de bombeio e feixe laser, alcançando 6,75 W cw (continuous wave) de potência de saída laser em 946 nm e slope efficiency de 48%. Em um segundo passo foi inserido, em diferentes tipos de cavidades, um cristal dobrador de freqüência para obtenção de emissão no azul em 473 nm, e a potência de saída azul foi medida em função da potência absorvida.; Blue lasers have attracted much attention for applications such as blu-ray, displays and as pumped source for the Ti:sapphire laser. A Nd:YAG crystal with diffusion bonded end-caps was used together with a pump wavelength of 802...

Geração de segundo harmônico sintonizável por modulação de fase de pulsos de laser ultracurtos; Tunable second harmonic generation by phase-modulated ultrashort laser pulses

Oliveira, Anderson Roberto de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/02/2012 PT
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Neste trabalho é feito um estudo da formatação de pulsos ultracurtos de laser de Ti:Safira para a geração de segundo harmônico em cristal de KDP. Para a formatação dos pulsos, é utilizado um aparato que inclui um modulador espacial de luz de cristal líquido (LC SLM), que altera unicamente a fase espectral dos pulsos. Este aparelho tem a vantagem de não introduzir perdas durante a propagação da luz, além de sua ação ser controlada via computador, através de um software em LabVIEW. Utilizando uma função senoidal, é feito um estudo das limitações do controle da geração do segundo harmônico provindas da pixelação do LC SLM, isto é, do fato de que os elementos moduladores possuem tamanhos finitos e produzem uma modulação discreta ao longo das componentes espectrais do pulso. É apresentada a geração de luz sintonizável em torno de 400 nm por duplicação de frequências de pulsos cuja fase espectral é modulada por uma soma de funções senoidais de frequências diferentes. A largura de banda do ultravioleta produzido é da ordem de 1 nm, em contraste com a largura de linha de cerca de 12 nm do segundo harmônico gerado na ausência de modulação do pulso fundamental. A sintonização é feita basicamente através de uma varredura na fase das funções moduladoras do pulso fundamental. Esse tipo de sintonização nessa região do espectro possui algumas aplicações...

Microscopias de óptica não linear : fluorescência excitada por absorção de dois fótons, geração de segundo harmônico e geração de terceiro harmônico; Non linear optical microscopies : two photon excited fluorescence, second harmonic generation and third harmonic generation

Vitor Bianchin Pelegati
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/12/2010 PT
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Biologia celular é um novo mundo promissor com enorme impacto social, econômico e na saúde. Organismos vivos são capazes de, produzir a própria energia a partir da luz do sol, se reproduzir, de se auto-reparar, sinalizar e navegar por sinais bioquímicos, biomecânicos, luminosos, térmicos, e outros, e produzir materiais à temperatura ambiente. As possibilidades abertas por essa área incluem, desde bactérias e protozoários usados para destruir células de câncer, regeneração de órgãos inteiros, produção de etanol a partir de algas, e outros. Entretanto, para o entendimento da biologia em seu nível mais profundo, ferramentas de observação não destrutivas fazem-se necessária para seguir os processos celulares durante seu tempo de vida. A óptica tem a única onda não destrutiva capaz de fornecer informações em tempo real com suficiente resolução espacial de eventos acontecendo internamente à célula. Ademais, porque feixes de luz não colidem, a óptica permite a integração de diferentes técnicas capazes de reunir informações simultâneas de processos celulares. Óptica não linear é especialmente adequada para tal, pois não requer marcação ou processamentos especiais de amostras que poderiam destruir...

Second Harmonic Generation Microscopy Used to Evaluate the Effect of the Dimethyl Sulfoxide Cryopreservation Process in Collagen Fibers of Differentiated Chondrocytes

Andreoli-Risso, M. F.; Duarte, A. S. S.; Ribeiro, T. B.; Bordeaux-Rego, P.; Luzo, A.; Baratti, M. O.; Adur, J.; de Thomaz, A. A.; Pelegati, V. B.; Carvalho, H. F.; Cesar, C. L.; Kharmadayan, P.; Costa, F. F.; Olalla-Saad, S. T.
Fonte: Spie-Int Soc Optical Engineering; Bellingham Publicador: Spie-Int Soc Optical Engineering; Bellingham
Tipo: Artigo de Revista Científica
ENG
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Cartilaginous lesions are a significant public health problem and the use of adult stem cells represents a promising therapy for this condition. Cryopreservation confers many advantages for practitioners engaged in cell-based therapies. However, conventional slow freezing has always been associated with damage and mortality due to intracellular ice formation, cryoprotectant toxicity, and dehydration. The aim of this work is to observe the effect of the usual Dimethyl Sulfoxide (DMSO) cryopreservation process on the architecture of the collagen fiber network of chondrogenic cells from mesenchymal stem cells by Second Harmonic Generation (SHG) microscopy. To perform this study we used Mesenchymal Stem Cells (MSC) derived from adipose tissue which presents the capacity to differentiate into other lineages such as osteogenic, adipogenic and chondrogenic lineages. Mesenchymal stem cells obtained after liposuction were isolated digested by collagenase type I and characterization was carried out by differentiation of mesodermic lineages, and flow cytometry using specific markers. The isolated MSCs were cryopreserved by the DMSO technique and the chondrogenic differentiation was carried out using the micromass technique. We then compared the cryopreserved vs non-cryopreserved collagen fibers which are naturally formed during the differentiation process. We observed that non-cryopreserved MSCs presented a directional trend in the collagen fibers formed which was absent in the cryopreserved MSCs. We confirmed this trend quantitatively by the aspect ratio obtained by Fast Fourier Transform which was 0.76 for cryopreserved and 0.52 for non-cryopreserved MSCs...

Use of the second harmonic generation microscopy to evaluate chondrogenic differentiation of mesenchymal stem cells for cartilage repair

Bordeaux-Rego, P.; Baratti, M. O.; Duarte, A. S. S.; Ribeiro, T. B.; Andreoli-Risso, M. F.; Vidal, B.; Miranda, J. B.; Adur, J.; de Thomaz, A. A.; Pelegati, V. B.; Costa, F. F.; Carvalho, H. F.; Cesar, C. L.; Luzo, A.; Olalla Saad, S. T.
Fonte: Spie-Int Soc Optical Engineering; Bellingham Publicador: Spie-Int Soc Optical Engineering; Bellingham
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
999.503%
Articular cartilage injury remains one of the major concerns in orthopedic surgery. Mesenchymal stem cell (MSC) transplantation has been introduced to avoid some of the side effects and complications of current techniques.. With the aim to evaluate chondrogenic differentiation of mesenchymal stem cells, we used Second Harmonic Generation (SHG) microscopy to analyze the aggregation and orientation of collagen fibrils in the hyaline cartilage of rabbit knees. The experiment was performed using implants with type II collagen hydrogel (a biomaterial that mimics the microenvironment of the cartilage), one implant containing MSC and one other without MSC (control). After 10 weeks, the rabbit knees were dissected and fibril collagen distribution and spatial organization in the extracellular matrix of the lesions were verified by SHG. The result showed significant differences, whereas in histological sections of the cartilaginous lesions with MSC the collagen fibers are organized and regular; in the control sections the collagen fibers are more irregular, with absence of cells. A macroscopic analysis of the lesions confirmed this difference, showing a greater percentage of lesions filling in knees treated with MSC than in the knees used as controls. This study demonstrates that SHG microscopy will be an excellent tool to help in the evaluation of the effectiveness of MSC-based cell therapy for cartilage repair.

The role of ferroelectric domain structure in second harmonic generation in random quadratic media

Roppo, Vito; Wang, Wenjie; Kalinowski, Ksawery; Kong, Y; Cojocaru, Crina; Trull, Jose; Vilaseca, Ramon; Scalora, Michael; Krolikowski, Wieslaw; Kivshar, Yuri
Fonte: http://www.osa.org/ Publicador: http://www.osa.org/
Tipo: Journal article; Published Version; Optical Society of America Formato: 11 pages
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We study theoretically and numerically the second harmonic generation in a nonlinear crystal with random distribution of ferroelectric domains. We show that the specific features of disordered domain structure greatly affect the emission pattern of the generated harmonics. This phenomena can be used to characterize the degree of disorder in nonlinear photonic structures.

Second Harmonic Generation of Chiral-Modified Silver Nanoparticles

Tao, Yue
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
1010.8796%
Chiral molecules, which exist under enantiomers with non-mirror-symmetrical structures, have been the subject of intense research for their linear and nonlinear optical activities. Cysteine is such a chiral amino acid found as a building block of proteins throughout human bodies. Second harmonic generation (SHG) has been considered to investigate chiral molecules. SHG from metallic nanoparticles is promising for nanoplasmonics and photonic nanodevice applications. Therefore, it’s desirable to combine and study nonlinear properties due to both chirality and metallic nanoparticles, and help developing an alternatively optical diagnostic of chiral molecules. Our experiments are carried out with the FemtoFiber Scientific FFS laser system. SHG of silver nanoparticles (Ag NPs) modified by either L-Cysteine (L-C) or D-Cysteine (D-C) is observed, where L-Cysteine and D-Cysteine are a pair of enantiomers. Ag NPs are deposited through Vacuum Thermal Evaporation, controlled under different deposition thicknesses. UV-Vis/IR spectra and AFM are used to characterize Ag NPs under different conditions. Transmitted SHG measurements dependent on incidence are recorded with standard lock-in techniques. Deposition thickness of vacuum thermal evaporation plays an important role in forming diverse Ag NPs...

Transverse second-harmonic generation from disordered nonlinear crystals

Fischer, Robert; Saltiel, Solomon; Neshev, Dragomir; Krolikowski, Wieslaw; Kivshar, Yuri
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
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999.503%
We investigate the transverse second-harmonic generation in as grown strontium barium niobate (SBN) crystals with a random structure of anti-parallel ferroelectric domains. We consider both, single and counter-propagating pulse geometries. We investigate

Spatial quantum correlations in the fluorescence of traveling-wave second-harmonic generation

Scotto, Pierre
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artículo Formato: 2373 bytes; 199758 bytes; text/plain; application/pdf
ENG
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913.5504%
15 pages, 14 figures.-- PACS nrs.: 42.50.Lc, 42.50.Dv, 42.65.Ky.; We investigate theoretically the spatial quantum correlations of the light produced by spontaneous emission in type-I second-harmonic generation in the traveling-wave configuration. It is first shown that spontaneous emission occurs at both fundamental and second-harmonic frequency. Considering the quantum fluctuations of the intensities collected in symmetrical parts of the far-field plane, nonclassical correlations below the shot noise are predicted not only at fundamental frequency, but also at second-harmonic frequency. The latter cannot be traced back to any twin-photon emission mechanism, but are generated by a secondary process acting on twin photons. This mechanism also creates correlations between fundamental and second-harmonic field, at a given transverse wave number, and at opposite wave numbers. The analysis of a simplified few-mode model, on a quantum level, provides a good qualitative understanding of these correlations.; Financial support from the European Commission Project QUANTIM (Grant No. IST-2000-26019), as well as from CONOCE: MCyT (Spain, Project No. BFM2000-1108) is acknowledged.; Peer reviewed

Use of nonlinear properties of intracavity type II second harmonic generation for image processing

Jacobo, Adrián; Colet, Pere; Scotto, Pierre; San Miguel, Maxi
Fonte: Springer Publicador: Springer
Tipo: Artículo Formato: 2373 bytes; 2764074 bytes; text/plain; application/pdf
ENG
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902.03984%
8 pages, 10 figures.-- PACS nrs.: 42.30.-d; 42.65.Ky; 42.65.Pc.; We discuss the use of intracavity type-II second harmonic generation for all-optical processing of images. Injecting an image in a pump beam linearly polarized and a homogeneous field in the orthogonally polarized pump it is possible to magnify the contrast and to recognize the contour of any part of the image whose intensity is above a tunable reference level. This can be done using ideal planar cavities where all the fields are resonant as well as in the more realistic situation where only the fundamental fields are resonant and using cavities with spherical mirrors.; We acknowledge financial support from MEC (Spain) and FEDER under projects FIS2004-00953 (Conoce2), BFM2001-0341-C02-02 (Sinfibio) and BFM2001-4180-E. AJ acknowledges a PhD fellowship from MEC (Spain).; Peer reviewed

Second harmonic generation in a photonic crystal

Martorell, Jordi; Vilaseca, Ramon; Corbalán, R.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //1997 ENG
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Phase matched second harmonic generation is observed experimentally in a centrosymmetric crystalline lattice of dielectric spheres of optical dimensions. The inversion symmetry is broken locally at the surface of each sphere in such a way that the scattered second harmonic light interferes constructively leading to a nonvanishing macroscopic field. Phase matching of the fundamental and second harmonic waves in such periodic lattice is observed to be naturally provided by the bending of the photondispersion curve at the edge of the Bragg reflection band of a given set of lattice planes.

Modulation-free control of a continuous-wave second-harmonic generator

Shaddock, Daniel; Buchler, Benjamin; Bowen, Warwick P; Gray, Malcolm; Lam, Ping Koy
Fonte: Institute of Physics Publishing Publicador: Institute of Physics Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
900.8483%
We present results for continuous-wave second-harmonic generation of 532 nm light in an external cavity locked using a spatial mode interference technique. This technique does not require frequency modulation and thus yields a clean second-harmonic spectrum devoid of modulation sidebands. The performance is compared with the same system controlled by Pound-Drever-Hall locking. Both techniques achieved the same maximum output power with comparable stability which is predominantly limited by fluctuations in the pump power and the nonlinear crystal temperature.

Electric Field Induced Second Harmonic Generation in Vacuum Evaporated Disperse Red 1 films

Taunaumang, H; Herman, N/A; Tjia, M O; Samoc, Marek
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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1007.157%
We have observed the electric field induced second harmonic (EFISH) generation effect on vacuum deposited Disperse Red 1 (DR1) films using corona poling. There is no second harmonic generation (SHG) signal in the absence of the corona. Room temperature corona charging results in an SHG signal which appears and disappears almost instantaneously upon turning on and turning off the corona field respectively. Combined with earlier spectroscopic studies on molecular organization in vacuum deposited DR1 thin film which suggested vertical orientation of most of the molecules, these results clearly indicate that the DR1 molecules in the film are most likely aligned in antiparallel arrangement. The EFISH effect as well as its fast responses to the on-off operation of corona field and the reduction of the SHG signal at elevated film temperature are explained in terms of effective dc field induced polarization effect on the molecules due to third-order nonlinearity of DR1.

Second-harmonic Generation in Vortex-induced Waveguides

Salgueiro, J; Carlsson, A; Ostrovskaya, Elena; Kivshar, Yuri
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
1009.92586%
We study the second-harmonic generation and localization of light in a reconfigurable waveguide induced by an optical vortex soliton in a defocusing Kerr medium. We show that the vortex-induced waveguide greatly improves conversion efficiency from the fundamental to the second-harmonic field.

In situ second harmonic geenration in disperse red 1-doped polymer and sol-gel films.

Samoc, Anna; Samoc, Marek; Luther-Davies, Barry; Kolev, Vesselin Z; Bagien, Radoslaw; Luo, Xinshi; Zha, Congji
Fonte: Taylor & Francis Group Publicador: Taylor & Francis Group
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
905.3591%
We investigated linear optical and second-order nonlinear optical (NLO) properties of films of poly(bisphenol A carbonate) resin, and a newly synthesised titania/silica/hybrid sol-gel polymer resin doped with Disperse Red 1 (DR1) molecular chromophore. DC electric field induced second harmonic generation (SHG) technique has been used to monitor in situ the polar alignment and relaxation of orientation of the guest molecules in the corona-poled films. The temporal behaviour of the second harmonic signal was remarkably different in these two polymers both during poling and when the poling field was turned off. A fast decay of the second harmonic intensity was observed at room temperature in 3 wt% DR1-doped sol-gel film, and a long relaxation time constant was found in 13 wt% DR1-doped polycarbonate film. Resonantly enhanced d eff coefficient of about 9 pm/V was found in the sol-gel film, and 25 pm/V in the polycarbonate film at the fundamental wavelength 1053 nm. The d 33 values were about 20 pm/V, and 60 pm/V in these films, respectively. The SHG results were used to estimate the average rotation mobility parameter of DR1 molecules in the host polymers.

Squeezed singly resonant second-harmonic generation in periodically poled lithium niobate

Lawrence, Michael John; Byer, Robert L; Fekel, Francis C; Bowen, Warwick P; Lam, Ping Koy; Bachor, Hans
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
999.503%
We determine the theoretical singly resonant second-harmonic generation squeezing performance of several cavity designs and nonlinear materials. We show that, for the doubling of the 1064-nm output of Nd:YAG lasers, monolithic cavities made from periodically poled LiNbO3 (PPLN) will produce the largest amount of squeezing. We also present experimental results for a free-space cavity with a PPLN sample that yielded slightly less than 0.6 dB of measured squeezing. The cavity performance as a function of input power agrees with our theoretical predictions and shows the superior performance of periodically poled materials for the production of bright squeezed light.

Second harmonic generation as a technique to probe buried interfaces

Neethling,P.H.; Scheidt,T.; Rohwer,E.G.; von Bergmann,H.M.; Stafast,H.
Fonte: South African Journal of Science Publicador: South African Journal of Science
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2009 EN
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Since the advances of femtosecond laser technology during the last decade, optical second harmonic generation (SHG) has proven itself a powerful tool to investigate the electronic and structural properties of semiconductor materials. Its advantage lies in the fact that it is a contact-less, non-intrusive method that can be used in situ. It is sensitive to systems with broken symmetry, in particular interfaces and surfaces. The Si/SiO2 system is technologically important since it forms a component of most modern electronic equipment. Furthermore, it has been shown that it is possible to induce an electric field across this interface by means of laser irradiation as a result of defect formation and defect population. This electric field can be measured since it determines the SHG signal. The anisotropy of the SHG signal from the Si/SiO2 interface was measured and showed four-fold symmetry, illustrating that the SHG technique was able to characterise the electrical properties of the interface below the 5 nm thick oxide layer.