Harmonic Generation Conversion Efficiency Research Articles

Theoretical analysis of electromagnetic field distribution and Cerenkov second harmonic generation conversion efficiency based on lithium niobate ion-implanted channel waveguide

Cerenkov type second harmonic generation (CSHG) is proposed in ion-implanted Z-cut lithium niobate (LiNbO3) channel waveguides. We have obtained exact analytical solutions for the field distribution and the power of second-harmonic waves. Conditions for attaining higher conversion efficiency are discussed on the basis of numerical calculations.

Growth, structural, optical and mechanical studies on acid mixed glycine metal salt (GABN) crystal as potential NLO material

Transparent crystals of α-glycine with ammonium nitrate and barium nitrate (GABN) have been grown from aqueous solution by slow evaporation technique at room temperature. Crystals of size 11 × 7 × 4 mm 3 have been obtained in about 3–4 weeks time. The solubility of GABN has been determined in water. The grown crystal belongs to orthorhombic system with cell parameters a = 7.317 A.U, b = 12.154 A.U and c = 5.468 A.U with a unit cell volume 486.35 (A.U) 3. The presence of chemical components/groups has been identified by CHN, EDAX and NMR analysis. Comparative IR and Raman studies indicate a molecule with a lack of centre of symmetry. A wide transparency window useful for optoelectronic applications is indicated by the UV Studies. Using a Nd-YAG laser (1064 nm), the optical second harmonic generation (SHG) conversion efficiency of GABN is found to be 1.406 times of that of standard KDP. On exposure to light the GABN crystals are found to exhibit negative photoconductivity. I–V characteristics, SEM studies, dielectrics studies, and Vickers micro hardness measurement have been carried out.

Crystal growth, optical and thermal studies of nonlinear optical γ-glycine single crystal grown from lithium nitrate

Single crystals of the nonlinear material γ-glycine have been grown in the presence of lithium nitrate by slow-evaporation method. Structural characterization of the grown crystals was carried out by powder and single crystal X-ray diffraction (XRD) methods and it is observed that the samples crystallize in hexagonal system with non-centrosymmetric space groups. The modes of vibrations of different molecular groups present in glycine have been identified by spectral analyses. UV–visible transmittance study was performed to analyze optical transparency of γ-glycine crystals and found that the crystal was transparent in the entire visible-NIR region. Second harmonic generation (SHG) conversion efficiency has been estimated as 62mV and the output power by the crystal was 1.72 times that of potassium dihydrogen phosphate (KDP) crystal. The thermal stability and decomposition of the sample have been studied by thermal analysis and it is observed that the γ-glycine crystal have good thermal stability.

Structural, optical and electrical studies on amino acid based new GBC crystals having non linear optical response

Transparent crystals of α-glycine with barium nitrate and calcium nitrate (GBC) have been grown from aqueous solution by slow evaporation technique at room temperature. Crystals of size 22 × 25 × 4 mm 3 have been obtained in 3–4 weeks time. The solubility of GBC has been determined in water. The grown crystal belongs to orthorhombic system with cell parameters a = 12.7321 A.U, b = 13.7752 A.U and c = 8.6002 A.U with unit cell volume of 1508.36 (A.U) 3. Comparative IR and Raman studies indicate a molecule with a lack of center of symmetry. A wide transparency window useful for optoelectronic applications is indicated by the UV Studies. Using Nd:YAG laser (1064 nm), the optical second harmonic generation (SHG) conversion efficiency of GBC is found to be 0.702 times than that of standard KDP. On exposure to light the GBC crystals exhibit positive photoconductivity. I–V characteristics, dielectrics studies, electrical and Vickers micro hardness measurement have been carried out. The GBC crystal exhibits more mechanical strength compared to the reported GSN crystals.

Crystal growth and characterization of organic single crystal: N-(2-hydroxybenzylidene)acetohydrazide

Single crystals of N-(2-hydroxybenzylidene)acetohydrazide were grown by evaporating the solvents from a methanol solution. The single crystal X-ray structure solution confirmed the monoclinic system of the compound with P2 1/n space group. The functional groups were identified using FT-IR spectroscopic technique. 1H NMR spectral analysis were carried out to identify the position of protons. The optical properties such as UV–vis in transmittance mode and second harmonic generation (SHG) conversion efficiency were investigated to explore the nonlinear optical (NLO) characteristics of the above crystals. In addition, the thermal properties of the title crystal were also evaluated with thermogravimetrical analysis.

Crystal growth and characterization of semiorganic single crystals of l-histidine family for NLO applications

Single crystals of l-histidine hydrochloride monohydrate and tartaric acid mixed l-histidine hydrochloride monohydrate have been grown by slow evaporation solution growth technique from appropriate mixtures of respective chemicals. Single crystal and powder X-ray diffraction analyses, Fourier transform infrared, nuclear magnetic resonance spectral analysis, thermo-gravimetric (TG), differential thermal analysis (DTA) have been employed to characterize the as-grown crystals. It is observed to be a wide transparency window for both the crystals from 300 to 1000 nm, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics have been studied using Q switched Nd: YAG laser ( λ=1064 nm). The second harmonic generation conversion efficiency of the grown crystal shows the suitability for frequency conversion applications.

Scaling of high harmonic generation conversion efficiency

A theory, first shown in Falcão-Filho et al (2009 Opt. Express 17 11217–29), for the calculation of high harmonic conversion efficiencies using top-hat driver pulses is presented. The theory is further extended to include dynamic ionization in each half cycle of the driver laser pulse which is crucial for the quantitative prediction of high-order harmonic efficiencies and spectra. The results are compared with numerical and experimental results from the literature for 1.6 and 2 µm drive wavelengths and good agreement is demonstrated. Particularly, it is shown that for long wavelength driver pulses, there is increased sensitivity to phase mismatch.

The relationship between conversion efficiency of high-order harmonic generation from atom and wavelength in two-color combined fields

By solving the time-dependent Schrödinger equation under velocity gauge with split-operator method, we studied the high harmonics of one-dimensional helium atom exposed to one-color laser field and two-color fields composed of IR field and UV field. And the relationship between conversion efficiency of high-order harmonic generation near the cut-off position and wavelength of the laser (800—2000 nm) was also analyzed. It was found that high-order harmonic conversion efficiency driven by two-color laser field near the cut-off position changes with wavelength as η(λ)∝λ－x,where the x value depends on the intensity of laser field, and the appropriate selection of intensity of combined laser field can improve high harmonic conversion efficiency near the cut-off position.

The wavelength dependence of high-order harmonic generationand attosecond pulses from atom in infrared laser field

Basing on the strong-field approximation, we study high harmonic generation of hydrogen atom exposed to the long wavelength infrared laser field, and analyze the wavelength dependence of conversion efficiency of high-order harmonic generation near the cut-off position. It is found that high-order harmonic yield is much lower near cut-off than in the beginning of the plateau of the harmonic generation, but the width of the attosecond pulse is narrowed with increasing wavelength.

夹持方式对KDP晶体三倍频转换效率的影响

夹持方式对KDP晶体三倍频转换效率的影响

Growth, structural and optical studies on amino acid based new GSB crystals having non-linear optical characteristics

Transparent crystals of α-glycine with sodium nitrate and barium nitrate (GSB) have been grown from aqueous solution by slow evaporation technique at room temperature. Crystals of size 11 × 7 × 4 mm 3 have been obtained in 3–4 weeks time. The solubility of GSB has been determined in water. The grown crystal belongs to orthorhombic system with cell parameters a = 4.684 a.u., b = 12.184 a.u. and c = 10.969 a.u. with unit cell volume of 625.99 (a.u.) 3. Comparative IR and Raman studies indicate a molecule with a lack of centre of symmetry. A wide transparency window useful for optoelectronic applications is indicated by the UV studies. Using Nd–YAG laser (1064 nm), the optical second harmonic generation (SHG) conversion efficiency of GSB is found to be 0.648 times that of standard KDP. On exposure to light the GSB crystals exhibit positive photoconductivity. I– V characteristics, dielectrics studies and Vickers micro hardness measurement have been carried out. The GSB crystal exhibits more mechanical strength compared to the reported GSN crystals.

Sawtooth grating-assisted phase-matching

We show that a sawtooth phase-modulation is the optimal profile for grating assisted phase matching (GAPM). Perfect (sharp) sawtooth modulation fully corrects the phase-mismatch, exhibiting conversion equal to conventional phase matching, while smoothened, approximate sawtooth structures are more efficient than sinusoidal or square GAPM modulations that were previously studied. As an example, we demonstrate numerically optically-induced sawtooth GAPM for high harmonic generation. Sawtooth GAPM is the most efficient method for increasing the conversion efficiency of high harmonic generation through quasi-phase-matching, with an ultimate efficiency that closely matches the ideal phase-matching case.

Study on defects in hydrothermal-grown KBe2BO3F2 crystals

Sizeable crystals of KBe2BO3F2 (KBBF) were successfully grown by the hydrothermal method, but their conversion efficiency of second harmonic generation (SHG) was much lower than that of the flux grown crystals. In order to find the reason, extensive studies on defects in hydrothermal-grown KBBF crystals were carried out for the first time. Dislocations, grain boundaries and twins were revealed and observed on the (001) plane of hydrothermal-grown KBBF crystals by chemical etching and microscopy. X-ray rocking curves indicate the hydrothermal-grown crystals are of poor crystalline quality. Moreover, powder X-ray diffraction measurements show some small unidentified peaks for hydrothermal-grown KBBF crystals. Powder SHG intensities of hydrothermal-grown KBBF crystals were found to be several times lower than those of the flux grown ones. These indicate the hydrothermal-grown KBBF crystals may contain structural defects.

Crystal growth, structural and optical characterization of a semi-organic single crystal for frequency conversionapplications

Single crystals of semi-organic l-histidine hydrobromide have been grown by slow evaporation technique from a mixture of l-histidine and hydrobromic acid in aqueous solution at ambient temperature. From high-resolution X-ray diffraction analysis, the crystalline perfection of the grown crystal has been studied. Single crystal X-ray diffraction analyses, Nuclear Magnetic Resonance spectral analysis, Thermo-Gravimetry (TG), Differential Thermal Analysis (DTA) and hardness test have been employed to characterize the as-grown crystals. The UV cutoff wavelength of the grown crystal is below 300 nm and has a wide transparency window, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics have been studied using Q switched Nd:YAG laser ( λ=1064 nm). The second harmonic generation conversion efficiency of the grown crystals confirms their suitability for frequency conversion applications.

Synthesis, growth and characterization of l-valine cadmium chloride monohydrate—A novel semiorganic nonlinear optical crystal

Single crystals of l-valine cadmium chloride monohydrate (LVCC), a novel semiorganic nonlinear optical material were synthesized and grown from aqueous solution by slow evaporation method at room temperature. The powder X-ray diffraction pattern and FT IR spectrum analysis confirmed the formation of the new crystal. LVCC has good optical transmission in the entire visible region, which is an essential requirement for a nonlinear crystal. The thermal studies reveal that the material has good thermal stability. The LVCC crystal was characterized by energy dispersive X-ray analysis. The optical second harmonic generation conversion efficiency of LVCC was determined using Kurtz powder technique.

Crystal growth and spectral studies of nonlinear optical γ-glycine single crystal grown from phosphoric acid

Single crystals of the organic nonlinear material γ-glycine have been grown in the presence of phosphoric acid by slow-evaporation method. The crystal structure is confirmed by X-ray powder diffraction method. The thermal stability and decomposition of the sample have been studied by thermal analysis. The result shows that the transition temperature, i.e. transition from γ- to α-glycine is enhanced from 165 °C to 191 °C. The modes of vibrations of different molecular groups present in glycine have been identified by spectral analyses. The transmittance spectrum of γ-glycine crystal shows that the lower UV cut-off wavelength lies at 230 nm. Second harmonic generation (SHG) conversion efficiency has been estimated as 125 mV and the output power by the crystal was 1.3 times that of potassium dihydrogen phosphate (KDP) crystal. The dielectric and microhardness measurements have been carried out on the γ-glycine crystal.

Growth of gamma glycine crystal and its characterisation

Single crystal of gamma-glycine, an organic nonlinear optical material, has been grown by solvent evaporation technique from a mixture of aqueous solutions of glycine and potassium nitrate, lithium nitrate at room temperature. Gamma glycine crystals have been grown up to the dimension of 20mmx15mmx12mm. Powder X-ray diffraction of the grown crystal was recorded and indexed. Single crystal X-ray diffraction studies were carried out and the unit cell parameters were compared with the literature values. The gamma-phase of glycine is confirmed by single crystal XRD and FTIR spectral analysis. The crystals were characterised by UV-vis-NIR transmission spectrum in the range 200-1100nm. The second harmonic generation conversion efficiency of gamma-glycine crystal was twice the efficiency of KDP crystal. Thermal characteristics of gamma-glycine crystals were determined by thermogravimetric analysis (TGA) and differential thermal analysis, which shows the thermal stability of the grown crystals. Dielectric constant and dielectric loss measurements were carried out at different temperatures and frequencies. The microhardness of the grown crystals has been studied using Vicker's microhardness tester.

Crystal growth and characterization of l-tyrosine bromide (LTB) nonlinear optical single crystals

Single crystals of l-tyrosine bromide (LTB) have been grown by slow evaporation method from different solutions prepared with different normality of the solvent at ambient temperature. It has been observed that the growth rate along the crystallographic axes is considerably changed for different normality of solvent and remarkable morphological changes have been observed for the grown crystals. X-ray diffraction analysis, NMR and FTIR spectral analyses, thermo gravimetric (TG), and differential thermal analysis (DTA) have been employed to characterize the as-grown crystal. The UV cutoff (LTB) is below 300 nm and has a wide transparency window, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics of LTB have been studied using Q-switched Nd:YAG laser ( λ=1064 nm). The second harmonic generation conversion efficiency of LTB is 1.2 times that of KDP. Hardness of the LTB crystal has also been determined. The laser damage threshold energy density has been found to be 625 MW/cm 2.

The evolution law of KTP SHG conversion efficiency in special repetition rate

Based on the conduction band electron density and the expression of the effective dielectric function, the absorption coefficient at 532nm of KTP crystal is deduced. The evolution law of conduction band electron density, absorption coefficient and second harmonic generation (SHG) conversion efficiency are comparatively studied. The results are as follows. The 532 nm absorption coefficient of KTP crystal is increasing with conduction band electron density, and the SHG conversion efficiency is decreasing with conduction band electron density. When the power density of fundamental frequency laser is a fixed value, conduction band electron density shows accumulation effects a different repetition rates, which caused the 532 nm transmission and the SHG conversion efficiency of KTP crystal to vary exponentially with acting time, and the accumulation effect is increasing obviously with repetition rate, but conduction band electron density and absorption coefficient approach thir steady values.

Blue 473-nm solid state diode pumped Nd:YAG/BiBO microchip laser

AbstractIn this paper we present a design of a compact, low power diode-pumped CW Nd:YAG laser operating at 946 nm with intracavity blue light generation at 473 nm for battery operated applications. The nonlinear crystal used in the experiment is a BiBO crystal cut for phase-matching type I. Using 0.8 W of pumping power, 20-mW stabile output power of blue light was achieved. The second harmonic generation conversion efficiency was 2.5%.