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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Observation of seeded second harmonic generation in bulk germanosilicate fiber preforms

Simultaneous irradiation of a bulk fiber preform with molar concentrations of 3 pct Ge and 0.5 pct P doped silica core region resulted in self-organized second harmonic generation with an effective chi(2) of about 1.2 x 10 to the -16th m/V. The experiments revealed that the bulk preform requires the same critical IR intensity (10 GW/sq cm) as the drawn fibers to prepare. Attempts to self-prepare the preform field, indicating that self-preparation in fibers is most likely initiated by second harmonic generation associated with the core-cladding interface.

Lawandy, N. M.↗
NASA NTRS1972

Efficient second harmonic generation of picosecond laser pulses.

Efficient conversion to the second harmonic (SH) using KD2PO4 and CsH2AsO4 crystals inside a folded cavity of a high-power-dye mode-locked neodymium-glass laser is reported. For the first time, frequency-doubled picosecond light pulses have been obtained in CsH2AsO4 with peak powers of the order of 1 GW/sq cm at 0.531 micron for an effective pump power density of 4 GW/sq cm.

Rabson, T. A.↗
NASA NTRS1987

Second harmonic plasma emission involving ion sound waves

The theory for second harmonic plasma emission by the weak turbulence (or random phase) processes L + L + or - S to T, proceeding in two three-wave steps, L + or - S to L prime and L + L prime to T, where L, S and T denote Langmuir, ion sound and electromagnetic waves, respectively, is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes, and constraints on the characteristics of the source plasma, are derived. Limits on the brightness temperature of the radiation and the levels of the L prime and S waves are determined. Expressions for the growth rates and path-integrated wave temperatures are derived for simple models of the wave spectra and source plasma.

Cairns, Iver H.↗
NASA NTRS1990

Compounds Generate Optical Second Harmonics

Newly synthesized organic salts found to generate relatively large second-harmonic signals when illuminated by fundamental signals in near-infrared spectrum. Made by crystallizing, with appropriate counterions, organic ions having large molecular hyperpolarizibilities. Large second-order nonlinear susceptibilities observed. These and other compounds having large nonlinear optical properties used in electro-optical modulators, switches, and signal-processing equipment.

Marder, Seth R.↗
NASA NTRS1991

Second harmonic conversion in cubic silicon carbide at 1.06 micron

This letter describes second harmonic conversion in cubic silicon carbide (beta-SiC) at a wavelength of 1.06 micron. Epitaxial layers of beta-SiC formed by vapor phase growth on silicon are indeed birefringent, and thus phase matchable. Phase-matched films of beta-SiC have respectable conversion efficiencies even in the presence of adsorption at 532 nm. The measured value of the effective second order nonlinear susceptibility for beta-SiC is chi super (2) eff = 1.05 +/- 0.3 x 10 exp -9 esu.

Harris, G. L.↗
NASA NTRS2011

Controlling Second Harmonic Efficiency of Laser Beam Interactions

A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

Barnes, Norman P.↗
NASA NTRS1992

Limitations on squeezing and formation of the superposition of two macroscopically distinguishable states at fundamental frequency in the process of second harmonic generation

The results of numerical simulations of quantum state evolution in the process of second harmonic generation (SHG) are discussed. It is shown that at a particular moment of time in the fundamental mode initially coherent state turns into a superposition of two macroscopically distinguished states. The question of whether this superposition exhibits quantum interference is analyzed.

Nikitin, S. P.↗
NASA NTRS1973

Two-pass-internal second-harmonic generation using a prism coupler.

A dispersive quartz prism is used to couple the total second harmonic generated in both directions by an internal cavity frequency doubler. The study shows that the dispersion of air and mirror reflection phase shifts can be compensated for by a slight nonphase match condition in the doubler.

Gonzalez, D. G.↗
NASA NTRS1990

Absolute and relative nonlinear optical coefficients of KDP, KD(asterisk)P, BaB2O4, LiIO3, MgO:LiNbO3, and KTP measured by phase-matched second-harmonic generation

Both absolute and relative nonlinear optical coefficients of six nonlinear materials measured by second-harmonic generation are discussed. A single-mode, injection-seeded, Q-switched Nd:YAG laser with spatially filtered output was used to generate the 1.064-micron fundamental radiation. The following results were obtained: d36(KDP) = 0.38 pm/V, d36(KD/asterisk/P) = 0.37 pm/V, (parallel)d22(BaB2O4)(parallel) = 2.2 pm/V, d31(LiIO3) = -4.1 pm/V, d31(5 percentMgO:MgO LiNbO3) = -4.7 pm/V, and d(eff)(KTP) = 3.2 pm/V. The accuracy of these measurements is estimated to be better than 10 percent.

Eckardt, Robert C.↗
NASA NTRS1993

Diacetylene and Polydiacetylene Derivatives of 2-Methyl-4-Nitroaniline for Second-Harmonic Generation

A novel diacetylene derivative of 2-Methyl-4-NitroAniline (MNA), a well-known material for Second-Harmonic Generation (SHG), is synthesized. This monomer DiAcetylene MethylNitroAniline, (DAMNA) is characterized by means of the Kurtz technique at 1064 nm and is found to have an SHG powder efficiency 62.5 % that of MNA itself. Thin crystalline films of DAMNA are grown onto quartz, Teflon, and Kapton substrates by means of vapor deposition in vacuum. These films are then polymerized in the solid state by exposure to long-wavelength UV radiation to give crystalline polydiacetylene thin films (PDAMNA). The films are next characterized for SHG, using an unpolymerized DAMNA film as a reference. Interestingly, films grown onto Teflon exhibit greater orientation and significantly greater SHG than those grown onto quartz and Kapton. This result is promising in that it demonstrates the potential of PDAMNA as both a crystalline and polymeric material for SHG applications, in which highly oriented thin films are desired. Computational modeling (usingAM1) is also carried out on DAMNA and is compared to the experimental results.

Paley, M. S.↗
NASA NTRS1976

A 230-GHz radiometer system employing a second-harmonic mixer

A radiometer system for use in the 1.3 mm region has been constructed and used for radio astronomical observations. A second-harmonic mixer employing a single Schottky diode downconverts the incident power to an IF frequency of about 1400 MHz. The measured double-sideband system noise temperature is 6000 K (noise figure = 13 dB) and the double-sideband mixer conversion loss is calculated to be 10 dB. The mixer is tunable over a range of at least 15 GHz.

Goldsmith, P. F.↗
NASA NTRS1990

Generating Second Harmonics In Nonlinear Resonant Cavities

Single-axial-mode lasers pump very-low-loss doubling crystals. Important advance in making resonant generation of second harmonics possible for diode-laser-pumped solid-state lasers is recent development of monolithic nonplanar ring geometries in neodymium:yttrium aluminum garnet (Nd:YAG) lasers that produce frequency-stable single-mode outputs. Other advance is development of high-quality MgO:LiNbO3 as electro-optically nonlinear material. Series of experiments devised to improve doubling efficiency of low-power lasers, and particularly of diode-laser-pumped continuous-wave Nd:YAG lasers.

Kozlovsky, William J.↗