RESUMEN
Wavelength conversion afforded by stimulated Raman scattering within a hollow core fiber is potentially useful for multispectral light detection and ranging (LiDAR). Herein, we make use of the ideal 1550 cm-1 vibrational Raman shift of an antiresonant fiber filled with gaseous oxygen so that the first and second Raman orders as well as the transmitted pump are all located in separate atmospheric transmission windows. To the best of our knowledge, this is the first report of stimulated Raman scattering in an oxygen-filled fiber. The host of closely spaced rotational stimulated Raman scattering (SRS) lines (12 cm-1) accompanying the transmitted pump and vibrational Raman orders form continuum bands allowing for much greater spectral coverage of the atmospheric transmission windows. The temporal profiles of the Raman orders can be separated without the use of a grating to potentially achieve a multi-band LiDAR.
RESUMEN
Although χ(2) nonlinear optical processes, such as difference frequency generation (DFG), are often used in conjunction with fiber lasers for wavelength conversion and photon-pair generation, the monolithic fiber architecture is broken by the use of bulk crystals to access χ(2). We propose a novel solution by employing quasi-phase matching (QPM) in molecular-engineered hydrogen-free, polar-liquid core fiber (LCF). Hydrogen-free molecules offer attractive transmission in certain NIR-MIR regions and polar molecules tend to align with an externally applied electrostatic field creating a macroscopic χ e f f(2). To further increase χ e f f(2) we investigate charge transfer (CT) molecules in solution. Using numerical modeling we investigate two bromotrichloromethane based mixtures and show that the LCF has reasonably high NIR-MIR transmission and large QPM DFG electrode period. The inclusion of CT molecules has the potential to yield χ e f f(2) at least as large as has been measured in silica fiber core. Numerical modeling for the degenerate DFG case indicates that signal amplification and generation through QPM DFG can achieve nearly 90% efficiency.
RESUMEN
Spectrally pure photons heralded from unentangled photon pair sources are crucial for any quantum optical system reliant on the multiplexing of heralded photons from independent sources. Generation of unentangled photon pairs in gas-filled hollow-core photonic crystal fibers specifically remains an attractive architecture for integration into quantum-optical fiber networks. The dispersion design offered by selection of fiber microstructures and gas pressure allows considerable control over the group-velocity profile which dictates the wavelengths of photon pairs that can be generated without spectral entanglement. Here, we expand on this design flexibility, which has previously been implemented for four-wave mixing, by modeling the use of a static, periodically poled electric field to achieve an effective quasi-phase-matched three-wave mixing nonlinearity that creates spontaneous parametric downconversion. Electric-field-induced quasi-phase-matched spontaneous parametric downconversion enables control of phase matching conditions that is independent of the group velocity, allowing phase matching at arbitrary wavelengths without affecting the entanglement of photons at those wavelengths. This decoupling of entanglement engineering and phase matching facilitates spectrally pure photon pair generation with efficiency and wavelength-tunability that is otherwise unprecedented.
RESUMEN
Laser sources in the short- and mid-wave infrared spectral regions are desirable for many applications. The favorable spectral guidance and power handling properties of an inhibited coupling hollow-core photonic crystal fiber (HC-PCF) enable nonlinear optical routes to these wavelengths. We introduce a quasi-phase-matched, electric-field-induced, pressurized xenon-filled HC-PCF-based optical parametric amplifier. A spatially varying electrostatic field can be applied to the fiber via patterned electrodes with modulated voltages. We incorporate numerically modeled electrostatic field amplitudes and fringing, modeled fiber dispersion and transmission, and calculated voltage thresholds to determine fiber lengths of tens of meters for efficient signal conversion for several xenon pressures and electrode configurations.
RESUMEN
We present a novel light detection and ranging (LiDAR) polarimeter that enables measurement of 12 of 16 sample Mueller matrix elements in a single, 10 ns pulse. The new polarization state generator (PSG) leverages Kerr phase modulation in a birefringent optical fiber, creating a probe pulse characterized by temporally varying polarization. Theoretical expressions for the Polarization State Generator (PSG) Stokes vector are derived for birefringent walk-off and no walk-off and incorporated into a time-dependent polarimeter signal model employing multiple polarization state analyzers (PSA). Polarimeter modeling compares the Kerr effect and electro-optic phase modulator-based PSG using a single Polarization State Analyzer (PSA) and a scattering sample yielding similarly good performance for both. We include results from an experimental demonstration of the Kerr effect PSG.
RESUMEN
The Extreme-Ultraviolet Imaging Spectrometer (EIS) is the first of a new generation of normal-incidence, two-optical-element spectroscopic instruments developed for space solar extreme-ultraviolet astronomy. The instrument is currently mounted on the Solar-B satellite for a planned launch in late 2006. The instrument observes in two spectral bands, 170-210 A and 250-290 A. The spectrograph geometry and grating prescription were optimized to obtain excellent imaging while still maintaining readily achievable physical and fabrication tolerances. A refined technique using low ruling density surrogate gratings and optical metrology was developed to align the instrument with visible light. Slit rasters of the solar surface are obtained by mechanically tilting the mirror. A slit exchange mechanism allows selection among four slits at the telescope focal plane. Each slit is precisely located at the focal plane. The spectrograph imaging performance was optically characterized in the laboratory. The resolution was measured using the Mg iii and Ne iii lines in the range of 171-200 A. The He ii line at 256 A and Ne iii lines were used in the range of 251-284 A. The measurements demonstrate an equivalent resolution of ~2 arc sec? on the solar surface, in good agreement with the predicted performance. We describe the EIS optics, mechanisms, and measured performance.
RESUMEN
The laboratory end-to-end testing of the Extreme-Ultraviolet Imaging Spectrometer (EIS) for the Solar-B satellite is reported. A short overview of the EIS, which observes in two bands in the extreme-ultraviolet wavelength range, is given. The calibration apparatus is described, including details of the light sources used. The data reduction and analysis procedure are outlined. The wavelength calibration using a Penning source to illuminate the aperture fully is presented. We discuss the aperture determination using a radiometrically calibrated hollow-cathode-based source. We then give an account of the predicted and measured efficiencies from consideration of the efficiencies of individual optical elements in first order, an account of efficiencies out of band when radiation incident in one band is detected in the other, and efficiencies in multiple orders. The efficiencies measured in first order for in band and out of band are compared with the predictions and the sensitivity, and its uncertainties are derived. Application of the radiometric calibration is discussed.