269 research outputs found
Dependence of Terahertz Emission and Detection in Photoconductive Antennas on Laser Parameters
In this study, we employ a standard Terahertz time-domain spectroscopy (THz-TDS) setup based on two photoconductive antennas (PCAs) for THz radiation generation and detection. The characterization of the emission and detection performance as a function of the input pulse wavelength and bandwidth is performed
The role of nonlinear optical absorption in narrow-band difference frequency terahertz-wave generation
We present a general analysis of the influence of nonlinear optical
absorption on terahertz generation via optical difference frequency generation,
when reaching for the quantum conversion efficiency limit. By casting the
equations governing the process in a suitably normalized form, including either
two-photon- or three-photon-absorption terms, we have been able to plot
universal charts for phase matched optical-to-terahertz conversion for
different values of the nonlinear absorption coefficients. We apply our
analysis to some experiments reported to date, in order to understand to what
extent multiphoton absorption could have played a role and also to predict the
maximum achievable conversion efficiency at higher peak pump intensities.Comment: 16 pages, 2 figures. Some correction and some explanation adde
Universal charts for optical difference frequency generation in the terahertz domain
We present a universal and rigorous approach to study difference frequency
generation in the terahertz domain, keeping the number of degrees of freedom to
a minimum, through the definition of a suitable figure of merit. The proposed
method relies on suitably normalized charts, that enable to predict the
optical-to-terahertz conversion efficiency of any system based on wave
propagation in quadratic nonlinear materials. The predictions of our approach
are found to be in good agreement with the best experimental results reported
to date, enabling also to estimate the d22 nonlinear coefficient of high
quality GaSe.Comment: 3 pages in 2 columns format, 3 figures. GaSe analysis has been
corrected. Fig. 3 has been replace
parametric conversion in micrometer and submicrometer structured ferroelectric crystals by surface poling
We report on recent technological improvements concerning nonlinear patterning of lithium niobate and lithium tantalate in the micrometer and submicrometer scales using surface periodic poling for ferroelectric domain inversion. The fabricated samples were employed for frequency doubling via quasiphase-matching both in bulk and guided wave geometries, including forward and backward configurations and wavelength conversion in bands C and L. We also investigated short-period quasiperiodic samples with randomly distributed mark-to-space ratios
Ultraviolet generation in periodically poled Lithium Tantalate waveguides
We demonstrate ultraviolet generation in lithium tantalate channel waveguides for frequency doubling via quasi-phase-matching. The samples, proton exchanged and nanostructured by electric-field assisted surface periodic poling with domains as deep as 40 μm, yield continuous wave light at 365.4 nm with conversion efficiencies larger than 7.5% W-1 cm-2
- …