Control of terahertz emission in photoconductive antennas through an additional optical continuous wave

This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-38-16-3123. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.The manipulation of the operating conditions of photoconductive antennas by means of an additional continuous wave (CW) is reported. It is used to control a fiber-based terahertz (THz) time-domain-spectroscopy system at telecom wavelengths. The injection of an optical CW into the transmitter allows the control of the THz amplitude without causing major degradation to the system performance. This, for instance, can be exploited to perform modulation of the THz signal.This work was supported by the Spanish Ministerio de Economia y Competitividad through project TEC2012-35797. The work of Alexander Bockelt is supported by the Formacion de Profesorado Universitario (FPU) grant program of the Ministerio de Economia y Competitividad.Bockelt, A.; Palací López, J.; Vidal Rodriguez, B. (2013). Control of terahertz emission in photoconductive antennas through an additional optical continuous wave. Optics Letters. 38(16):3123-3125. https://doi.org/10.1364/OL.38.003123S312331253816Siegel, P. H. (2002). Terahertz technology. IEEE Transactions on Microwave Theory and Techniques, 50(3), 910-928. doi:10.1109/22.989974Tonouchi, M. (2007). Cutting-edge terahertz technology. Nature Photonics, 1(2), 97-105. doi:10.1038/nphoton.2007.3Jepsen, P. U., Cooke, D. G., & Koch, M. (2010). Terahertz spectroscopy and imaging - Modern techniques and applications. Laser & Photonics Reviews, 5(1), 124-166. doi:10.1002/lpor.201000011Smith, P. R., Auston, D. H., & Nuss, M. C. (1988). Subpicosecond photoconducting dipole antennas. IEEE Journal of Quantum Electronics, 24(2), 255-260. doi:10.1109/3.121Hu, B. B., Zhang, X. ‐C., Auston, D. H., & Smith, P. R. (1990). Free‐space radiation from electro‐optic crystals. Applied Physics Letters, 56(6), 506-508. doi:10.1063/1.103299Sartorius, B., Roehle, H., Künzel, H., Böttcher, J., Schlak, M., Stanze, D., … Schell, M. (2008). All-fiber terahertz time-domain spectrometer operating at 1.5 μm telecom wavelengths. Optics Express, 16(13), 9565. doi:10.1364/oe.16.009565Sartorius, B., Schlak, M., Stanze, D., Roehle, H., Künzel, H., Schmidt, D., … Schell, M. (2009). Continuous wave terahertz systems exploiting 15 µm telecom technologies. Optics Express, 17(17), 15001. doi:10.1364/oe.17.015001Ryu, C., & Kong, S. G. (2010). Boosting terahertz radiation in THz-TDS using continuous-wave laser. Electronics Letters, 46(5), 359. doi:10.1049/el.2010.0142Kyoung, J., Seo, M., Park, H., Koo, S., Kim, H., Park, Y., … Kim, D.-S. (2010). Giant nonlinear response of terahertz nanoresonators on VO_2 thin film. Optics Express, 18(16), 16452. doi:10.1364/oe.18.016452Fan, F., Gu, W.-H., Chen, S., Wang, X.-H., & Chang, S.-J. (2013). State conversion based on terahertz plasmonics with vanadium dioxide coating controlled by optical pumping. Optics Letters, 38(9), 1582. doi:10.1364/ol.38.00158

SOA-based optical processing for terahertz time-domain spectroscopy

All-fibre control of a terahertz time-domain spectroscopy system based on photoconductive antennas fed with optical sources in the telecom band is demonstrated. A semiconductor optical amplifier (SOA) is used to obtain continuously tunable delays on 100 fs optical pulses. Additionally, the modulation required to carry out lock-in detection can be simultaneously performed avoiding mechanical choppers or high-voltage alternate biasing of the transmitter antenna.This work was supported by the Spanish Ministerio de Ciencia e Innovacion TEC2009-08078. J. Palaci's work is supported by an FPI-UPV grant programme of the Universitat Politecnica de Valencia.Palací López, J.; Bockelt, A.; Vidal Rodriguez, B. (2012). SOA-based optical processing for terahertz time-domain spectroscopy. Electronics Letters. 48(10):593-594. https://doi.org/10.1049/el.2012.0761S5935944810Conelly, M.J.: ‘Semiconductor optical amplifiers’, (Kluwer Academic, Boston, MA 2002)Agrawal, G. P., & Olsson, N. A. (1989). Self-phase modulation and spectral broadening of optical pulses in semiconductor laser amplifiers. IEEE Journal of Quantum Electronics, 25(11), 2297-2306. doi:10.1109/3.42059Sedgwick, F. G., Pesala, B., Uskov, A. V., & Chang-Hasnain, C. J. (2007). Chirp-enhanced fast light in semiconductor optical amplifiers. Optics Express, 15(26), 17631. doi:10.1364/oe.15.017631Inohara, R., Nishimura, K., Tsurusawa, M., & Usami, M. (2003). Experimental analysis of cross-phase modulation and cross-gain modulation in SOA-injecting CW assist light. IEEE Photonics Technology Letters, 15(9), 1192-1194. doi:10.1109/lpt.2003.816121Pesala, B., Sedgwick, F., Uskov, A. V., & Chang-Hasnain, C. (2007). Electrically tunable fast light at THz bandwidth using cascaded semiconductor optical amplifiers. Optics Express, 15(24), 15863. doi:10.1364/oe.15.01586

Social identity and engagement: An exploratory study at university

Within the framework of research on students' active performance in their study habits, the aim of this study is to analyze a model predicting the effect of social identity and personal initiative on engagement in university students. We conducted a cross-sectional study on 266 students from different Spanish universities. The resulting data were analyzed using SPSS Macro MEDIATE. Evidence was found for the proposed model. Only group-identity predicted personal initiative and engagement. Analysis revealed the mediating role of proactive behavior on engagement in university students. It is concluded that the university management may intervene, from an organizational-culture approach, promoting guidelines to reinforce students'' sense of belonging by enhancing initiative and autonomous problem solving in learning behaviors

Energy loss of relativistic projectiles in non-ideal electron liquids

[EN] The energy loss of relativistic projectiles in collisional one-component plasmas is analyzed within the method of moments. Both the canonical and non-canonical solutions of the Hamburger moment problem corresponding to five convergent power frequency moments of the electron plasma loss function are employed with the static, purely imaginary, Nevanlinna parameter with the imaginary part iqual to the collision frequency calculated within the Green-Kubo formalism in terms of static structure factors evaluated in the HNC approximation using the Deutsch effective potential.Thus we take into account the dissipation processes in the plasma. It is pointed out that the correlations only slightly influence the deviation of the stopping power with the relativistic corrections taken into account from the classical Bethe-Bohr-Larkin asymptotic form.The financial support of the Spanish Ministerio de Educación y Ciencia Project # ENE2010-21116-C02-02 and the Ministry of education and science of the Republic of Kazakhstan projects #1128/GF, 1129/GF, 1099/GF are gratefully acknowledged. IMT acknowledges also the hospitality of the al-Farabi Kazakh National UniversityArkhipov, YV.; Ashikbayeva, A.; Askaruly, A.; Davletov, A.; Palací, D.; Tkachenko Gorski, IM. (2013). Energy loss of relativistic projectiles in non-ideal electron liquids. International Journal of Mathematics and Physics. 4(1):50-55. http://hdl.handle.net/10251/15511450554

Multi-meridian corneal imaging of air-puff induced deformation for improved detection of biomechanical abnormalities

19 pags., 10 figs., 2 tabs.Corneal biomechanics play a fundamental role in the genesis and progression of corneal pathologies, such as keratoconus; in corneal remodeling after corneal surgery; and in affecting the measurement accuracy of glaucoma biomarkers, such as the intraocular pressure (IOP). Air-puff induced corneal deformation imaging reveals information highlighting normal and pathological corneal response to a non-contact mechanical excitation. However, current commercial systems are limited to monitoring corneal deformation only on one corneal meridian. Here, we present a novel custom-developed swept-source optical coherence tomography (SSOCT) system, coupled with a collinear air-puff excitation, capable of acquiring dynamic corneal deformation on multiple meridians. Backed by numerical simulations of corneal deformations, we propose two different scan patterns, aided by low coil impedance galvanometric scan mirrors that permit an appropriate compromise between temporal and spatial sampling of the corneal deformation profiles. We customized the air-puff module to provide an unobstructed SSOCT field of view and different peak pressures, air-puff durations, and distances to the eye. We acquired multi-meridian corneal deformation profiles (a) in healthy human eyes in vivo, (b) in porcine eyes ex vivo under varying controlled IOP, and (c) in a keratoconus-mimicking porcine eye ex vivo. We detected deformation asymmetries, as predicted by numerical simulations, otherwise missed on a single meridian that will substantially aid in corneal biomechanics diagnostics and pathology screening.Horizon 2020 Framework Programme (666295, 713694, 779960); Ministerio de Economía, Industria y Competitividad, Gobierno de España (FJC2018-038736-I); Fundacja na rzecz Nauki Polskiej (MAB/2019/12)

Customized swept-source optical coherence tomography system for air-puff induced corneal deformation imaging on multiple meridians

PIE BiOS, San Francisco, California, United States, 17 Marzo 2020. -- SPIE Proceedings Vol. 11218: Ophthalmic Technologies XXX . -- https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11218/2546050/Customized-swept-source-optical-coherence-tomography-system-for-air-puff/10.1117/12.2546050.full?SSO=