Abstract-Broadband molecular sensing with a tapered spoof plasmon waveguide

Broadband molecular sensing with a tapered spoof plasmon waveguide Jingjing Yang, Yan Francescato, Dezhang Chen, Jianfeng Yang, and Ming Huang  »View Author Affiliations

Optics Express, Vol. 23, Issue 7, pp. 8583-8589 (2015)
http://dx.doi.org/10.1364/OE.23.008583

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-7-8583

View Full Text Article

Enhanced HTML    Acrobat PDF (1988 KB)

Unambiguous identification of low concentration chemical mixtures can be performed by broadband enhanced infrared absorption (BEIRA). Here we propose and numerically study a corrugated parallel plate waveguide (CPPW) with gradient grooves which is capable of directly converting transmission modes to surface plasmon modes and could hence serve as a powerful chemical sensor. Such a waveguide can be designed to exhibit a wide pass band covering an extended portion of a molecule absorption spectrum. Broadband sensing of toluene and ethanol thin layers is demonstrated by calculating the transmission coefficient of the waveguide and is shown to correspond exactly to their infrared spectra. In addition, the upper limit and the lower limit of the bandgap are mainly dependent on the minimum and maximum groove height, respectively, which provide an effective way of tuning the working frequency of the device in order to support surface plasmon modes within a desired frequency range according to a specific application.

© 2015 Optical Society of America

Abstract-High-temperature, continuous-wave operation of terahertz quantum-cascade lasers with metal-metal waveguides and third-order distributed feedback

M. Wienold, B. Röben, L. Schrottke, R. Sharma, A. Tahraoui, K. Biermann, and H. T. Grahn  »View Author Affiliations

Optics Express, Vol. 22, Issue 3, pp. 3334-3348 (2014)
http://dx.doi.org/10.1364/OE.22.003334

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-3-3334

Currently, different competing waveguide and resonator concepts exist for terahertz quantum-cascade lasers (THz QCLs). We examine the continuous-wave (cw) performance of THz QCLs with single-plasmon (SP) and metal-metal (MM) waveguides fabricated from the same wafer. While SP QCLs are superior in terms of output power, the maximum operating temperature for MM QCLs is typically much higher. For SP QCLs, we observed cw operation up to 73 K as compared to 129 K for narrow (≤ 15 μm) MM QCLs. In the latter case, single-mode operation and a narrow beam profile were achieved by applying third-order distributed-feedback gratings and contact pads which are optically insulated from the intended resonators. We present a quantitative analytic model for the beam profile, which is based on experimentally accessible parameters.

© 2014 Optical Society of America

Abstract-Terahertz quantum cascade lasers with thin resonant-phonon depopulation active regions and surface-plasmon waveguides

M. Salih, P. Dean, A. Valavanis, S. P. Khanna, L. H. Li, J. E. Cunningham, A. G. Davies, E. H. Linfield
http://arxiv.org/abs/1303.3205
We report three-well, resonant-phonon depopulation terahertz quantum cascade lasers with semi-insulating surface-plasmon waveguides and reduced active region (AR) thicknesses. Devices with thicknesses of 10, 7.5, 6, and 5 {\mu}m are compared in terms of threshold current density, maximum operating temperature, output power and AR temperature. Thinner ARs are technologically less demanding for epitaxial growth and result in reduced electrical heating of devices. However, it is found that 7.5-{\mu}m-thick devices give the lowest electrical power densities at threshold, as they represent the optimal trade-off between low electrical resistance and low threshold gain.