We develop a general model, based on a (2 + 1)D unidirectional pulse propagation equation, for describing broadband noncollinear parametric interactions in 2D quadratic lattices. We apply it to the analysis of twin-beam optical parametric generation in hexagonally poled LiTaO3, gaining further insights into experimental observations.
We develop a general model, based on a (2+1)D unidirectional pulse propagation equation, for describing broadband noncollinear parametric interactions in two-dimensional quadratic lattices. We apply it to the analysis of twin-beam optical parametric generation in hexagonally poled LiTaO<inf>3</inf>, gaining further insights into experimental observations.
A common problem when applying Raman scattering in applied research is spectral interference from laser-induced fluorescence. Extensive work has been invested in developing spectral and polarization filters as well as modulation schemes to refine spontaneous Raman signals. This current work, however, focuses on utilizing the temporal domain using a picosecond laser system and ICCD cameras with relatively short decay of the camera gate to prevent the fluorescence tail from being captured in Raman experiments. Further, the approach of using an ICCD camera to perform temporal filtering is compared to earlier proposed detection schemes using streak cameras or Kerr gates. The temporal-filtering scheme is evaluated in a spectroscopic investigation where a background subtraction algorithm is presented. The temporal-filtering scheme was also evaluated for Raman imaging of a levitated water droplet surrounded by fluorescing toluene vapor. Furthermore, the temporal-filter detection scheme was simulated in order to provide straight forward evaluation tools to estimate the potential of performing temporal filtering with a laser/camera system considering: laser-pulse duration, time jitter, camera-gate characteristics, gate delay times, fluorescence lifetimes, and relative signal strength between the Raman and fluorescence signal. The fluorescence signal was modeled with a closed two-level system, and the simulated results were compared to results from an investigation of the rising slope of toluene fluorescence. These evaluation tools and experimental investigations may serve as guidelines for planning and performing Raman measurements in situations where traditional filter-rejection schemes are insufficient.
We demonstrate optical parametric generation in two-dimensional purely nonlinear lattices. Experiments performed in hexagonally poled LiTaO3 crystals pumped around 800 nm indicate a coherent contribution to the parametric gain arising from multiple resonances of the lattice, resulting in dual-beam signal outputs in the 1-1.7 mu m range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3583444]
We demonstrate dual-beam optical parametric generation in hexagonally poled LiTaO3. The experimental results indicate a coherent contribution to the parametric gain arising from multiple resonances in the nonlinear lattice.
This paper provides an overview of our work on nonlinear optical devices in MgO-doped nearly stoichiometric LiTaO3. We present experimental results for optical parametric oscillation and broadband generation obtained with one- and two- dimensional periodically poled structures.
The talk will briefly introduce the technology and design principles for quadratic nonlinear photonic crystals and provide a few examples of optical functionalities affordable on this platform, with a particular focus on recent developments concerning frequency down-conversion and their implications for the engineering of novel parametric light sources for classical and quantum optics applications.
Nonlinear optical processes are an essential tool in modern optics, with a broad spectrum of applications, including signal processing, frequency conversion, spectroscopy and quantum optics. Ordinary parametric devices nevertheless still suffer from relatively low gains and wide spectral emission. Here we demonstrate a unique configuration for phase- matching multiple nonlinear processes in a monolithic 2D nonlinear photonic crystal, resulting in the coherent parametric emission of four signal and idler modes, featuring an exponential gain enhancement equal to the Golden Ratio. The results indicate a new route towards compact high- brightness and coherent sources for multi- photon generation, manipulation and entanglement, overcoming limitations of conventional parametric devices.
Optical parametric frequency conversion based on quasi phase matching (QPM) in nonlinear optical crystals is a powerful technique for generating coherent radiation in wavelength ranges spanning from the mid-infrared (mid-IR) to the blue, displaying low thermal load and high efficiency.This thesis shows how QPM in one- (1D) or two-dimensional (2D) lattices can be employed to engineer novel devices for parametric downconversion in the IR, af-fording freedom in designing both spectral and angular properties of the parametric output. Experimental demonstrations of parametric devices are supported by theoreti-cal modelling of the nonlinear conversion processes.In particular, broadband parametric downconversion has been investigated in 1D QPM lattices, through degenerate downconversion close to the point of zero group-velocity dispersion. Ultra-broadband optical parametric generation (OPG) of 185 THz bandwidth (at 10 dB), spanning more than one octave from 1.1 to 3.7 μm, has been achieved in periodically poled 1 mol% MgO-doped near-stoichiometric LiTaO3 (MgSLT) of 25 μm QPM period, pumped at 860 nm. Such broadband gain is of high interest for ultrashort optical pulse amplification, with applications in high harmonic generation, ultrafast spectroscopy and laser ablation. Furthermore, the det-rimental impact of parasitic upconversion, creating dips in the OPG spectrum, has been investigated. By altering the pump pulse duration, energy can be backconverted to create peaks at the involved OPG wavelengths, offering a possible tool to enhance broadband parametric gain spectra.The engineering of the angular properties of a parametric output benefits greatly from 2D QPM, which is investigated in this thesis by the specific example of hexagonally poled MgSLT. It is demonstrated how two OPG processes, supported by a single 2D QPM device, can exhibit angularly and spectrally degenerate signals (idlers). This degeneracy results in a coherent coupling between the two OPG pro-cesses and a spectrally degenerate twin-beam output in the mid-IR (near IR). 2D QPM devices exhibiting such coherently coupled downconversion processes can find applications as compact sources of entangled photon-pairs. This thesis further illus-trates the design freedom of 2D QPM through the demonstration of a device support-ing multiple parametric processes, thus generating multiple beams from the mid-IR to the blue spectral regions.
We theoretically and experimentally investigate multistep parametric processes in broadband optical parametric generators (OPGs) based on periodically poled 1 mol. % MgO-doped stoichiometric LiTaO3. We demonstrate that parametric collateral processes may deplete or enhance spectral portions of the OPG output, depending on pump pulse duration.
We investigate theoretically and experimentally multistep processes in broadbandoptical parametric generation (OPG) and demonstrate the possibility to control fine features in thegain spectra via the OPG pump.
We investigate the effect of angular tuning on coherently coupled optical parametric generation (OPG) in two-dimensional purely nonlinear lattices and demonstrate how it allows accessing both shared signal and shared idler regimes, resulting in twin-beam outputs in the mid- and near infrared, respectively. Furthermore, we present the results of a systematic spectral and angular mapping of the twin-beam OPG response in the near-infrared as a function of the pump incidence angle.
Purely nonlinear photonic crystals (NPCs) [1], fabricated by 2D periodic poling of ferroelectric materials, offer novel degrees of freedom to engineer the response of single step and cascaded frequency up-converters [2-3]. Recently, we demonstrated a novel configuration for frequency down-conversion in hexagonally poled LiTa03 (hexLT) [4], whereby two lattice resonances are coherently coupled to yield twin-beam optical parametric generation (OPG) with a shared signal or idler, significantly enhancing the OPG spectral and angular responses [5]. In this paper we show how the twin-beam OPG output in turn initiates multiple up-conversion processes (mediated by higher-order RLVs of the lattice) resulting in further enrichment of the spectral and angular range of cascaded up-conversions processes in the visible.
Collinear broadband optical parametric generation was achieved in periodically poled Mg-doped stoichiometric lithium tantalate by picosecond pumping at 820-890 nm, i.e. close to zero group velocity dispersion.Flat signal spectra as broad as 500nm (3dB bandwidth), around ~1450 nm,were detected for periods of 25 and 26micrometers.
We experimentally investigate parametric downconversion approaching zero group velocity dispersion in Mg-doped stoichiometric LiTaO3. Pumping in the 820-842 nm range yields a 14 THz gain bandwidth with signal (idler) wavelengths around 1.23 μm (2.66 μm).
We experimentally investigate parametric downconversion approaching zero group velocity dispersion in Mg-doped stoichiometric LiTaO3. Pumping in the 820-842 nm range yields a 14 THz gain bandwidth with signal (idler) wavelengths around 1.23 mu m (2.66 mu m).
We report on the possibility to affect the direction of energy transfer of cascaded sumfrequency conversion processes associ-ated to broadband parametric generation (OPG) in periodically poled MgO:LiTaO3, by means of the OPG pump. This holds promise for a coherent control of the gain profiles of optical parametric generators and amplifiers.
We investigate experimentally the spectral and angular degrees of freedom of multi-resonant optical parametric generation in hexagonally poled LiTaO3 and demonstrate access to twin-beam output for either signal or idler waves by pump angle tuning.
We investigate experimentally the spectral and angular degrees of freedom of multi-resonant optical parametric generation in hexagonally poled LiTaO 3 and demonstrate access to twin-beam output for either signal or idler waves by pump angle tuning.
We report on broadband gain in an optical parametric generator based on periodically poled 1 mol% magnesium-doped stoichiometric LiTaO(3) (PPMg:SLT). More than an octave-spanning parametric gain, stretching from near to mid-infrared, is generated by pumping the crystals close to the point where, at parametric degeneracy, the waves experience zero group-velocity dispersion. Using a picosecond Ti:sapphire source, we measured the broadest parametric gain bandwidths, 180 THz at 10 dB, in PPMg: SLT gratings with a period of 25 mu m pumped at 860 nm.