Observation of tunable optical parametric fluorescence.
Optical fluorescence, thermally tunable over significant portion of visible and near IR SPECTRUM, from phase-matched parametric system
THERMAL EFFECT↗
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High-quantum-efficiency infrared up-conversion.
Experimental study in which 100% conversion of infrared photons into visible photons was achieved through three wave interactions in a nonlinear medium. The first experimental evidence of overconversion is presented, and the classical theory of up-conversion in the high-conversion-efficiency region is confirmed. A laser pump light feedback technique is described that promises to make the process practical with modestly powerful pump lasers and less than perfect nonlinear crystals. The nonlinear medium used was a LiIO3 crystal that cannot be 90-deg phase-matched. The 'walk off' that resulted helped make possible the attainment of 100% conversion efficiency.
Gurski, T. R.↗
Generation of ultraviolet and vacuum ultraviolet radiation
The paper describes nonlinear optical techniques that use phase-matched mixtures of metal vapors and inert gases, or, in certain cases, only inert gases for the generation of ultraviolet radiation. These systems are transparent where nonlinear crystals are opaque and their high ionization permits optical power densities of 10 to the 10 or 10 to the 11 W/sq cm to be utilized. An experiment designed to convert incident 1.064 micron radiation to 3547 A radiation is described as are experiments designed to generate vacuum ultraviolet at 1773, 1520, 1182 and 887 A. Theoretical considerations on the use of this nonlinear optical technique for the generation of soft X-rays are presented and the construction of a vacuum ultraviolet holographic grating with a fringe spacing of 836 A is reported on.
Harris, S. E.↗
An infrared upconverter for astronomical imaging
An imaging upconverter has been constructed which is suitable for use in the study of the thermal 10-micron radiation from astronomical sources. The infrared radiation is converted to visible radiation by mixing in a 1-cm-long proustite crystal. The phase-matched 2-kayser bandpass is tunable from 9 to 11 microns. The conversion efficiency is 2 by 10 to the -7th power and the field of view of 40 arc seconds on the sky contains several hundred picture elements, approximately diffraction-limited resolution in a large telescope. The instrument has been used in studies of the sun, moon, Mercury, and VY Canis Majoris.
Boyd, R. W.↗
Simultaneous observation of rotational coherent Stokes Raman scattering and coherent anti-Stokes Raman scattering in air and nitrogen
Rotational coherent Stokes Raman scattering (CSRS) and coherent anti-Stokes Raman scattering (CARS) in air and in nitrogen were observed simultaneously by using broadband generation and detection. In the broadband technique used, the entire CARS and CSRS spectrum was generated in a single laser pulse; the CSRS and CARS signals were dispersed by a spectrograph and detected simultaneously by an optical multichannel analyzer. A three-dimensional phase-matching geometry was used to achieve spatial resolution of the CSRS and CARS beams from the input beams. Under resonant conditions, similar experiments may provide a means of investigating the possible interaction between the CSRS and CARS processes in driving the rotational levels.
Snow, J. B.↗
Harnessing surface plasmons for solar energy conversion
NASA research on the feasibility of solar-energy conversion using surface plasmons is reviewed, with a focus on inelastic-tunnel-diode techniques for power extraction. The need for more efficient solar converters for planned space missions is indicated, and it is shown that a device with 50-percent efficiency could cost up to 40 times as much per sq cm as current Si cells and still be competitive. The parallel-processing approach using broadband carriers and tunable diodes is explained, and the physics of surface plasmons on metal surfaces is outlined. Technical problems being addressed include phase-matching sunlight to surface plasmons, minimizing ohmic losses and reradiation in energy transport, coupling into the tunnels by mode conversion, and gaining an understanding of the tunnel-diode energy-conversion process. Diagrams illustrating the design concepts are provided.
Anderson, L. M.↗
Spatially and spectrally resolved multipoint coherent anti-Stokes Raman scattering from N2 and O2 flows
Single-shot spectrally resolved broadband rotational coherent anti-Stokes Raman scattering (CARS) from multiple points along a line intersecting a flow has been observed for N2 and O2. A large-angle phase-matching configuration was used to achieve spatial resolution of 0.1 mm x 0.1 mm x 0.1 mm for each of 20 points in the interaction volume. Single-shot multipoint CARS of N2 at different temperatures and of several species in a coflowing jet was observed.
Snow, J. B.↗
Longitudinal-mode control in integrated semiconductor laser phased arrays by phase velocity matching
The spectrum of semiconductor-laser arrays with separate contacts is investigated. It is demonstrated that the individual laser currents can be selected such that the array operates in a single longitudinal mode, in contrast to the multimode nature of its individual constituents. Moreover, it is possible to tune the lasing frequency by varying the laser currents. Wavelength tuning range of about 50 A, with tuning rate of about 5 A per milliampere, is demonstrated. It is suggested that these spectral features, characteristic of lasers which are coupled in parallel, result from the strong frequency dependence of their spatial mode pattern near the phase-matching frequency of their coupled waveguides.
Kapon, E.↗
Analysis of Nd3+:glass, solar-pumped, high-powr laser systems
The operating characteristics of Nd(3+):glass lasers energized by a solar concentrator were analyzed for the hosts YAG, silicate glass, and phosphate glass. The modeling is based on the slab zigzag laser geometry and assumes that chemical hardening methods for glass are successful in increasing glass hardness by a factor of 4. On this basis, it was found that a realistic 1-MW solar-pumped laser might be constructed from phosphate glass 4 sq m in area and 2 mm thick. If YAG were the host medium, a 1-MW solar-pumped laser need only be 0.5 sq m in area and 0.5 cm thick, which is already possible. In addition, Nd(3+) doped glass fibers were found to be excellent solar-pumped laser candidates. The small diameter of fibers eliminates thermal stress problems, and if their diameter is kept small (10 microns), they propagate a Gaussian single mode which can be expanded and transmitted long distances in space. Fiber lasers could then be used for communications in space or could be bundled and the individual beams summed or phase-matched for high-power operation.
Zapata, L. E.↗
Some optical properties of KTP, LiIO3, and LiNbO3
Measurements of the absorption coefficient for KTP, LiIO3, and LiNbO3 are discussed. The variation of the refractive index with temperature has been measured for KTP and LiIO3. It is necessary to know both the absorption coefficient beta and the variation in the indexes of refraction with temperature change dn/dT to determine the average power limit of a nonlinear interaction. With the dn/dT information, it is also possible to estimate the temperature half width of any nonlinear interaction by calculating the variation of the phase-matching condition with temperature.
Gettemy, Donald J.↗
Solid-state lasers for coherent communication and remote sensing
Semiconductor-diode laser-pumped solid-state lasers have properties that are superior to other lasers for the applications of coherent communication and remote sensing. These properties include efficiency, reliability, stability, and capability to be scaled to higher powers. We have demonstrated that an optical phase-locked loop can be used to lock the frequency of two diode-pumped 1.06 micron Nd:YAG lasers to levels required for coherent communication. Monolithic nonplanar ring oscillators constructed from solid pieces of the laser material provide better than 10 kHz frequency stability over 0.1 sec intervals. We have used active feedback stabilization of the cavity length of these lasers to demonstrate 0.3 Hz frequency stabilization relative to a reference cavity. We have performed experiments and analysis to show that optical parametric oscillators (OPO's) reproduce the frequency stability of the pump laser in outputs that can be tuned to arbitrary wavelengths. Another measurement performed in this program has demonstrated the sub-shot-noise character of correlations of the fluctuations in the twin output of OPO's. Measurements of nonlinear optical coefficients by phase-matched second harmonic generation are helping to resolve inconsistency in these important parameters.
Byer, Robert L.↗
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.↗
Multiple-mode reconfigurable electro-optic switching network for optical fiber sensor array
This paper reports the first switching network compatible with multimode fibers. A one-to-many cascaded reconfigurable interconnection was built. A thin glass substrate was used as the guiding medium which provides not only higher coupling efficiency from multimode fiber to waveguide but also better tolerance of phase-matching conditions. Involvement of a total-internal-reflection hologram and multimode waveguide eliminates interface problems between fibers and waveguides. The DCG polymer graft has proven to be reliable from -180 C to +200 C. Survivability of such an electrooptic system in harsh environments is further ensured. LiNbO3 was chosen as the E-O material because of its stability at high temperatures (phase-transition temperature of more than 1000 C) and maturity of E-O device technology. Further theoretical calculation was conducted to provide the optimal interaction length and device capacitance.
Chen, Ray T.↗
Self-Frequency-Doubling Glass-Fiber Laser
Specially prepared germanium and phosphorous-doped glass optical fiber doped with neodymium shown to act as self-frequency-doubling laser. Self-frequency-doubling fiber laser with further refinements, eliminates need for expensive, easily damaged, nonlinear crystals currently used. Enables one to avoid loss and damage mechanisms associated with interfaces of nonlinear crystals as well as to eliminate angle/temperature phase-matching tuning.
Selker, Mark D.↗
A loophole-free Bell's inequality experiment
The proof of Nature's nonlocality through Bell-type experiments is a topic of longstanding interest. Nevertheless, no experiments performed thus far have avoided the so-called 'detection loophole,' arising from low detector efficiencies and angular-correlation difficulties. In fact, most, if not all, of the systems employed to date can never close this loophole, even with perfect detectors. In addition, another loophole involving the non-rapid, non-random switching of various parameter settings exists in all past experiments. We discuss a proposal for a potentially loophole-free Bell's inequality experiment. The source of the EPR-correlated pairs consists of two simultaneously-pumped type-2 phase-matched nonlinear crystals and a polarizing beam splitter. The feasibility of such a scheme with current detector technology seems high, and will be discussed. We also present a single-crystal version, motivated by other work presented at this conference. In a separate experiment, we have measured the absolute detection efficiency and time response of four single-photon detectors. The highest observed efficiencies were 70.7 plus or minus 1.9 percent (at 633 nm, with a device from Rockwell International) and 76.4 plus or minus 2.3 percent (at 702 nm, with an EG&G counting module). Possible efficiencies as high as 90 percent were implied. The EG&G devices displayed sub-nanosecond time resolution.
Kwiat, Paul G.↗
Novel solutions to low-frequency problems with geometrically designed beam-waveguide systems
The poor low-frequency performance of geometrically designed beam-waveguide (BWG) antennas is shown to be caused by the diffraction phase centers being far from the geometrical optics mirror focus, resulting in substantial spillover and defocusing loss. Two novel solutions are proposed: (1) reposition the mirrors to focus low frequencies and redesign the high frequencies to utilize the new mirror positions, and (2) redesign the input feed system to provide an optimum solution for the low frequency. A novel use of the conjugate phase-matching technique is utilized to design the optimum low-frequency feed system, and the new feed system has been implemented in the JPL research and development BWG as part of a dual S-/X-band (2.3 GHz/8.45 GHz) feed system. The new S-band feed system is shown to perform significantly better than the original geometrically designed system.
Imbriale, W. A.↗
Average Power Effects in Parametric Oscillators and Amplifiers
Thermally induced phase mismatch and thermally induced lensing will limit the average power available from a parametric oscillator or amplifier. Expressions are derived that describe both of these average power effects for the commonly used radial heat extraction as well as for longitudinal heat extraction. It is shown that the effects of thermally induced phase mismatch can be mitigated by a judicious selection of the phase-matching conditions.
Barnes, Norman P.↗
DSS-13 S-Band Design Optimization Using The Focal-Plane Method
In this paper, the Focal-Plane (Complex-Conjugate Phase-Matching) Method is used to select the appropriate gain and location of a feed for S-Band (2.295 GHz) operation of DSS-13, the new NSA/JPL Deep Space Network (DSN) 34-m Beam WaveGuide (BWG) antenna. It is found empirically that the Focal-Plane Method gives a better design in terms of the G/T figure than previous S-Band designs.
Focal Plane S-Band↗