Search results for "harmonic generation"
showing 10 items of 217 documents
Wavelength tuning of femtosecond pulses generated in nonlinear crystals by using diffractive lenses
2010
We demonstrate that diffractive lenses (DLs) can be used as a simple method to tune the central wavelength of femtosecond pulses generated from second-order nonlinear optical processes in birefringent crystals. The wavelength tunability is achieved by changing the relative distance between the nonlinear crystal and the DL, which acts in a focusing configuration. Besides the many practical applications of the so-generated pulses, the proposed method might be extended to other wavelength ranges by demonstrated similar effects on other nonlinear processes, such as high-order harmonic generation.
Towards CEP stable sub two cycle IR pulse compression with bulk material
2010
We demonstrate both experimentally and numerically that self-steepening during propagation in a hollow-fiber followed by linear propagation through glass in the anomalous dispersion enables pulse compression down to 1.9 cycles at 1.8 micron wavelength.
Backward frequency doubling of near infrared picosecond pulses.
2014
We report on backward second-harmonic generation using ps laser pulses in congruent lithium niobate with 3.2 µm periodic poling. Three resonant peaks were measured between 1530 and 1730 nm, corresponding to 16th, 17th and 18th quasi-phase-matching orders in the backward configuration, with a conversion efficiency of 4.75 x 10(-5%)/W for the 16th order. We could also discriminate the contributions from inverted domains randomized in duty-cycle.
Grating-assisted third-harmonic generation in photonic crystal fibers using a pulse pump
2011
We demonstrate that quasi-phase-matching of the third-harmonic generation process can be obtained for a pulse pump in the photonic crystal fiber with a refractive-index grating. Conversion efficiency is calculated numerically using a system of coupled generalized nonlinear Schrodinger equations. We propose a special design of the microstructured fiber for the third-harmonic generation and analyze different phenomena limiting the maximum efficiency for short (femtosecond) and long (picosecond) pump pulses. Moreover, we show that a certain level of a group-velocity mismatch between the pump and the third harmonic can increase the maximum efficiency in the long pulse regime.
Soft proton exchanged channel waveguides in congruent lithium tantalate for frequency doubling
2010
We report on stable optical waveguides fabricated by soft-proton exchange in periodically-poled congruent lithium tantalate in the a-phase. The channel waveguides are characterized in the telecom wavelength range in terms of both linear properties and frequency doubling. The measurements yield a nonlinear coefficient of about 9.5pm/V, demonstrating that the nonlinear optical properties of lithium tantalate are left nearly unaltered by the process. (C) 2010 Optical Society of America
Triple excitation effects in coupled-cluster calculations of frequency-dependent hyperpolarizabilities
1998
Abstract We describe an implementation of an analytic scheme for the calculation of static and dynamical first hyperpolarizabilities at the CC3 level in the framework of coupled-cluster response theory. Calculations are reported for the static, the second harmonic generation, and the optical rectification hyperpolarizabilities of FH. The results indicate the importance of triple excitation effects for accurate theoretical predictions of hyperpolarizabilities and lend further support to previous contentions that an experimental value for the second harmonic generation hyperpolarizabilities of FH should be reconsidered.
Light-Driven Extremely Nonlinear Bulk Photogalvanic Currents
2021
We predict the generation of bulk photocurrents in materials driven by bichromatic fields that arc circularly polarized and corotating. The nonlinear photocurrents have a fully controllable directionality and amplitude without requiring carrier-envelope-phase stabilization or few-cycle pulses, and can be generated with photon energies much smaller than the band gap (reducing heating in the photoconversion process). We demonstrate with ab initio calculations that the photocurrent generation mechanism is universal and arises in gaped materials (Si, diamond, MgO, hBN), in semimetals (graphene), and in two- and three-dimensional systems. Photocurrents are shown to rely on sub-laser-cycle asymme…
Harmonic generation from nanorings driven by a two-color laser field
2014
We study the high harmonic generation and the polarization of the harmonics emitted by a nanoring driven by two laser fields of angular frequency ?1 and ?2, with ?2?=?2?1, and ?1 resonant between the ground and the first excited state. We show that by varying parameters, such as laser intensity, photon energy and the delay between the two laser pulses, we can control the number of harmonics and the polarization of the radiation. In particular we show that with this choice of two-laser photon frequency rate we obtain more harmonics with respect to other configurations. We also calculated the average absorbed energy and the average angular momentum acquired by the electron as a function of th…
Laser driven quantum rings: one byte logic gate implementation
2018
We study the effect of the carrier-envelope-phase (CEP) on the high harmonic generation (HHG) from a quantum ring driven by two short orthogonal lasers polarized along the x and y axes. In particular, by varying only the phase of the laser polarized along y it is possible to control the intensity of the emitted harmonics. In fact, we show that the system can efficiently emit harmonics if the laser polarized along y is small and that the cut-off of the spectra can be controlled by changing the phase or the intensity ratio between the two lasers. The wavelet analysis of the emitted harmonics and the time dependence of the angular momentum and of the energy acquired by the electron show that t…
High-order-harmonic generation in dimensionally reduced systems
2013
The time-dependent wave function of a nanoring driven by a laser field is obtained by exploiting the symmetries inherent to the system and used for studying the properties of the electromagnetic radiation emitted by the nanoring as a function of the polarization state of the laser. The diffused radiation has the characteristics of high-order-harmonic generation. For a noncircularly polarized laser field an extension of the expected cutoff position is evident, indicating that nanorings are efficient sources of radiation. The polarization state of the emitted harmonics can be opportunely controlled by varying the parameters of the pump field. The profile of the absorbed angular moment shows t…