Frequency Conversion Applications Research Articles

A Half-Bridge Converter With Input Current Ripple Reduction for DC Distribution Systems

Employing an L-C-L filter cell to modify the half-bridge converter (HBC), a HBC with input current ripple reduction (HBC-CRR) is proposed. In addition to having low-voltage stress, lossless snubbing, and voltage-clamping features inherited from its predecessor, the proposed converter can shape input current waveform of HBC to a nonpulsating fashion. Consequently, the ripple and undesired harmonic components of the input current can be significantly reduced without adding a large input filter. These characteristics make it suitable for high frequency, high efficiency, high-input voltage, and low electromagnetic interference (EMI) dc distribution power conversion applications. In addition to the circuit analysis and design consideration, moreover, a proposed converter and a HBC with the same specification, 360–400-V input, 12-V/20-A output, and 100-kHz switching frequency, are built and tested for the purpose of the comparison. Several performance comparisons are made to demonstrate the superiority of the proposed converter over HBC.

Injection-seeded optical parametric amplifier for generating chirped nanosecond pulses

We constructed an optical parametric amplifier with BiBO crystals, which was injection seeded by a phase-modulated cw beam in the 1,040-1,070 nm region. Two-stage pre-amplification by Yb-doped fibers were implemented for stable injection to the OPA. The frequency chirp in the OPA pulse was actively controlled by adjusting the RF wave for the phase modulation and its synchronization to the OPA firing. Down/up chirps with up to 500 MHz shift were demonstrated. The output pulse energy was ~40 mJ, which is sufficient for future application of frequency conversion and coherent population transfer.

Growth technique to increase the device purpose yield of a KDP crystal and assessment of its quality using X-ray and optical techniques

A methodology to increase the device purpose yield of a KDP crystal is reported in this paper. The method is based on increasing the cross-section of the prismatic sector {100} of the growing KDP crystal at the expense of the unusable pyramidal cap portion by restricting the growth of the crystal up to a particular height, decided by the solution–air interface in the crystallizer. Due to the lack of solution above the interface, the crystal ceases to grow in the upward direction whereas it continues to grow laterally. This leads to an increase in the usable volume of the grown crystal for the fabrication of crystal elements required for electro-optic switching and frequency conversion applications. An empirical relationship has been introduced as a condition to grow flat-top shaped KDP crystals. It relates the growth parameters with the apparatus design parameters. Several flat-top shaped crystals have been grown as a validation of the growth methodology and the empirical relationship. The influence of the growth methodology on the crystalline quality of the grown crystal was assessed by measuring the defect structure of different sectors of the grown crystal by X-ray topography (XRT). The crystalline perfection was estimated by recording the rocking curve widths using high resolution X-ray diffraction (HRXRD). The optical quality was assessed by measuring the UV-vis-NIR transmission of the different sectors of the crystal and the refractive index homogeneity using interferometric techniques of conoscopy. It is found that restricting the growth of the crystal in the [001] direction by the solution–air interface does not have any detrimental effect on the crystalline and optical qualities of the grown crystal.

Application of frequency conversion of starlight to high-resolution imaging interferometry. On-sky sensitivity test of a single arm of the interferometer

Abstract We investigate the sensitivity of frequency conversion of starlight using a non-linear optical sum frequency process. This study is being carried out in the context of future applications of optical interferometry dedicated to high-resolution imaging. We have implemented a complete experimental chain from telescope to detector. The starlight frequency is shifted from the infrared to the visible using an optically non-linear crystal. To fulfil the requirements of interferometry, our experimental setup uses spatially single-mode and polarization maintaining components. Due to the small size of the collecting aperture (8 inches Celestron C8) with a 3 nm spectral bandwidth, on-sky tests were performed on bright stars in the H band. The detection was achieved in a true photon counting operation, using synchronous detection. Betelgeuse (HMag =−3.9), Antares (HMag =−3.6) and Pollux (HMag =−1) were successfully converted and detected in visible light. Despite the low transmission of our experiment, our results prove that the efficiency of frequency conversion offers sufficient sensitivity for future interferometric applications.

Experimental analysis of overall thermal properties of Nd:La2CaB10O19crystals

Pure or rare-earth-ion-doped La2CaB10O19(LCB) is a promising optical material for nonlinear frequency conversion, laser and self-frequency doubling applications. In this paper, the thermophysical properties of Nd3+-doped LCB (Nd:LCB) crystals were measured and compared with those of pure and of Yb3+- and Er3+-doped LCB, as well as other borate nonlinear optical crystals. The melting points of rare-earth-doped LCB crystals are lower than that of pure LCB. Thermal expansion coefficients along thea,b,c,c*,a*, 〈110〉 and 〈110〉* directions have been measured, and the principal expansion coefficients were calculated to be 1.85 × 10−6, 4.13 × 10−6and 8.79 × 10−6 K−1. The measured specific heat of Nd:LCB is lower than that of pure LCB, resulting in a larger internal temperature gradient under irradiation by a pulsed laser beam. The measured thermal expansion anisotropy of Nd:LCB is stronger than that of pure LCB. The thermal conductivities of Nd:LCB along thecandc* directions are smaller than those along other crystallographic directions.

Borate Crystals for Nonlinear Optical and Laser Applications: A Review

The development of borate‐based single crystals for laser and frequency conversion applications is reviewed. The basic idea behind nonlinear optics and the role of anionic groups in the borate crystals are summarized. The properties of borate crystals—BBO, LBO, CBO, KBBF, SBBO, CLBO, YCOB, GdCOB, GdYCOB, KAB and LCB—are discussed. The growth and characterization of several rare earth‐based borate crystals are mainly focused. Several borate crystals are grown from the melt techniques and a few crystals are grown adopting the flux technique. Many rare earth‐based borate crystals are extensively used in device applications as they exhibit the frequency conversion ability along with high laser‐induced damage tolerance.

Broadband cascading of second-order nonlinearity in randomized nonlinear photonic crystal

We study both experimentally and theoretically optical parametric process in one-dimensional nonlinear photonic crystal with random variation to the sign of the second-order nonlinear coefficient. We demonstrate that the structure randomness enables broadband third-harmonic generation via cascading of two second-order nonlinear parametric wave interactions with the overall conversion efficiency higher than previously recorded in fully disordered media such as the as-grown strontium barium niobate crystal. Furthermore, thanks to the one-dimensional modulation of the second-order nonlinearity, the emitted broadband harmonics preserve well the spatial intensity profile of the incident fundamental light beam, a feature critical for applications of optical frequency conversion but unavailable in two-dimensional fully random media due to the beam divergence caused by the simultaneous emission of noncollinear harmonic.

Thick orientation-patterned GaAs grown by low-pressure HVPE on fusion-bonded templates

Quasi-phase-matched GaAs layers up to 600μm thick have been produced by low-pressure hydride vapor phase epitaxy (HVPE) regrowth on templates fabricated using wafer fusion bonding. We have used this combination of techniques to demonstrate an alternative approach for commercial development of orientation-patterned GaAs (OP-GaAs) for nonlinear optical frequency conversion applications. We report on the characterization of this material and present a comparison with OP-GaAs grown using the conventional all-epitaxial templates. The primary advantages of the wafer fusion method are the avoidance of the molecular beam epitaxy growth of GaAs/Ge/GaAs and the ability to use substrates without misorientation. We have observed that some of the misorientation-related growth defects which affect conventional OP-GaAs growth are not as problematic for regrowth on wafer fusion bonded templates. The overall quality of antiphase domain propagation was similar to conventional OP-GaAs layers. A disadvantage was that growth rates were approximately half the values measured for regrowth on misoriented templates.

Resonant cascaded down-conversion

We analyze an optical parametric oscillator (OPO) in which cascaded down-conversion occurs inside a cavity resonant for all modes but the initial pump. Due to the resonant cascade design, the OPO presents two ${\ensuremath{\chi}}^{(2)}$-level oscillation thresholds that are therefore much lower than for a ${\ensuremath{\chi}}^{(3)}$ OPO. This is promising for reaching the regime of an effective third-order nonlinearity well above both thresholds. Such a ${\ensuremath{\chi}}^{(2)}$ cascaded device also has potential applications in frequency conversion to far-infrared regimes. But, most importantly, it can generate novel multipartite quantum correlations in the output radiation, which represent a step beyond squeezed or entangled light. The output can be highly non-Gaussian and therefore not describable by any semiclassical model. In this paper, we derive quantum stochastic equations in the positive-$P$ representation and undertake an analysis of steady-state and dynamical properties of this system.

Crystal growth and characterization of l-histidine hydrochloride monohydrate semiorganic nonlinear optical single crystals

Nearly perfect single crystals of l-histidine hydrochloride monohydrate have been grown from the solution prepared from the mixture of l-histidine and hydrochloric acid using slow evaporation solution growth technique. Single crystal X-ray diffraction analysis, High resolution X-ray diffraction analysis, fourier transform infrared and FT-Raman analyzes were employed for structural characterization. Linear and nonlinear optical properties have been studied by UV–Vis transmission spectrum and Kurtz Perry technique respectively. The refractive index, redox behavior and hardness of the grown crystal have been found by suitable methods. Thermogravimetric, differential thermal analysis were employed to characterize the as-grown crystals. The second harmonic generation conversion efficiency of the grown crystal and other properties show the suitability of the grown crystal for frequency conversion applications.

Synthesis, growth and characterization of L-proline dimercuricchloride single crystals for frequency conversion applications

A semi-organic nonlinear optical L-proline dimercuricchloride (LPDMC) material has been synthesized. LPDMC single crystals were grown from aqueous solution by a slow cooling method. Good quality single crystals of size 19×6×3 mm3 have been grown over a period of 3 weeks. The grown crystals have been subjected to single crystal X-ray diffraction analysis to determine the cell parameters. The title compound crystallizes in the triclinic system with a noncentrosymmetric space group P1 and with unit-cell parameters a=7.2742(4) A, b=9.4472(5) A, c=10.4767(6) A, α=108.621(3)∘, β=107.260(2)∘, γ=97.353(2)∘ and volume=631.51(6) A3. Optical and dielectric properties of the crystals have been studied. The thermal stability of the crystals was determined by thermogravimetric analysis/differential thermal analysis. The second harmonic generation efficiency of the crystals was obtained by the classical powder technique using a Nd:YAG laser and it is found to be 2.5 times that of potassium dihydrogen phosphate.

Application of Frequency Conversion in Preparation of Semisolid A356 Alloy Slurry

The semisolid A356 alloy slurry was prepared by low superheat pouring and slightly electromagnetic stirring (LSPSES). The effects of frequency conversion on the slurry were researched for energy-saving. The results indicated that it was feasible to prepare the slurry with particle primary phases by LSPSES. The application of frequency conversion technique into the preparation of the slurry by LSPSES was favorable to satisfying the requirements of rheo-forming and reducing the energy consumption.

A study of the optical properties of semi-organic crystals doped with erbium

Organic crystals have nonlinear optical effects (NLO) that make them attractive for applications in frequency conversion and optical processing. Among these we find the amino acids. glycine is the simplest of all amino acids in the crystalline form, has three different polymorphs a, b and g in which the molecules exist in the dipolar form (NH3+CH2COO-). In this work, we obtained glycine crystals doped with erbium growth by slow evaporation at room temperature. The chemical composition of the crystal was determined by Fourier transform infrared (FTIR), and Raman spectroscopy and was conducted for glycine with different concentrations of erbium. The optical absorption spectrum recorded in the wavelength range of UV-vis revealed that the crystal has good optical transparency in the range of 350 to 1100 nm. The crystalline phase was determined by X-ray diffraction and the second harmonic generation efficiency of the crystal measured by using the Kurtz Perry modified method. Key words: Glycine, erbium, nonlinear optical effects (NLO), second harmonic generation (SHG).

Pyroelectrically induced photorefractive damage in magnesium-doped lithium niobate crystals

Beam distortion due to photorefraction limits the usability of lithium niobate (LiNbO3) crystals for frequency conversion applications. To prevent beam distortion in LiNbO3, 5 mol.% magnesium-doped LiNbO3 (MgO:LN) is usually used. However, we show that strong beam distortion of green laser light can occur within seconds in MgO:LN, starting at light intensity levels in the 100 mW/cm2 regime, if the crystal is heated by several degrees Celsius during or before illumination. Beam distortion does not occur in undoped congruent LiNbO3 (CLN) under the same conditions. We show that the pyroelectric effect together with an elevated photoconductivity compared to that of CLN causes this beam distortion and that this effect also influences frequency conversion experiments in the infrared even if no external heating is applied.

Design and Application of Frequency Conversion Constant Pressure Water Supply System

Firstly, this paper analysed the existed problem on traditional controlling way of city water supply system, then elaborated the controlling principle of frequency conversion. Finally, a designed practical example by frequency conversion technical is given on the water supply system. It is proved that frequency conversion can maintain constant pressure water, and it is a very ideal efficient measure for energy saving. Therefore design and transformation on water supply system has a broad market application prospect.

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.

Nonlinear plasmonic frequency conversion through quasiphase matching

Received 9 September 2010; published 6 October 2010An efficient frequency conversion scheme of surface-plasmon polariton SPP is proposed for nonlinearplasmonic applications. Lossy coupling wave equations are deduced to describe the interaction among involvedSPP frequency components. The reciprocal vector of a microstructure could partially compensate the SPPwave-vector mismatch through quasiphase matching QPM . As an example, the frequency doubling of SPPover a periodically poled lithium niobate is studied. The high-field concentration of SPP greatly enhanced thesecond-harmonic generation SHG over a short traveling distance. Although the high attenuation of SPPaffects the SHG severely, a long-range SPP SHG is further proposed and investigated, which shows greatefficiency improvement. The applications of QPM SPP frequency conversion are also discussed showing greatpotentials in miniature plasmonic sources and processors.DOI: 10.1103/PhysRevB.82.155107 PACS number s : 73.20.Mf, 42.65.Ky, 78.20.Bh

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.

Experimental investigation into conversion efficiency of cascading four-wave mixing

We have proposed and experimentally demonstrated a scheme for cascading four-wave mixing (CFWM) by exploiting nonlinearity in highly nonlinear fiber (HNLF). Through utilizing optical spectrum analyzer (OSA), the second-order sideband products are observed in our experiment by only launching two waves into HNLF, and the conversion efficiency from the injected wave to each sideband is discussed in detail. It is found that only the conversion efficiency of the satellite wave will be increased with the power of the tunable injected wave when the power and the wavelength of the other one are fixed. Furthermore, the conversion efficiency of all the sidebands will be decreased with the absolute value of detune of injected wavelengths increasing. Also, the authors have demonstrated that the power of the satellite wave will be influenced most among all the sidebands if tuning the injected wave power. The proposed scheme can find potential applications in parametric amplification, frequency conversion, and optical quantum-information processing.

ChemInform Abstract: Wide Spectral Range Nonlinear Optical Crystals of One-Dimensional Coordination Solids [Et4N][Cd(SCN)3] and [Et4N][Cd(SeCN)3] and the General Design Criteria for [R4N][Cd(XCN)3] (Where R: Alkyl and X: S, Se, Te) as NLO Crystals.

We report herein two new nonlinear optical (NLO) crystals, [Et4N][Cd(XCN)3], where X = S (1) and Se (2), that are transparent from 220 to 3300 nm, covering the entire near-ultraviolet, the visible, and the near-infrared spectral regions and giving rise to a very wide and continuous optical window, which is useful for many frequency conversion applications. Both 1 and 2 exhibit highly efficient second harmonic generation (SHG) as measured via the Kurtz−Perry method. The corresponding [Me4N]+ salts, [Me4N][Cd(XCN)3 where X = S (3) and Se (4), show no SHG effects. All four structures adopt noncentrosymmetric space groups (Cmc21 for 1 and 2 and Pna21 for 3 and presumably 4) and are based on one-dimensional anionic [Cd(XCN)3-]∞ zigzag chains. However, a detailed analysis of the structures of [R4N][Cd(XCN)3], where R = Et, Me, and X = S, Se revealed that the difference in the second-order nonlinear responses of the Et4N+ salts (1 and 2) and the Me4N+ salts (3 and 4) is attributable to the relative alignment of ...