Abstract-Improved Tuning Fork for Terahertz Quartz-Enhanced Photoacoustic Spectroscopy

Angelo Sampaolo 1,2

, Pietro Patimisco 1,2

, Marilena Giglio 1

, Miriam S. Vitiello 3

, Harvey E. Beere 4

,David A. Ritchie 4

, Gaetano Scamarcio 1

, Frank K. Tittel 2

 and Vincenzo Spagnolo 1,* 

1 Dipartimento Interateneo di Fisica, Università degli studi di Bari Aldo Moro e Politecnico di Bari, Via Amendola 173, Bari I-70126, Italy2 Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA3 NEST, CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa I-56127, Italy4 Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK

* Author to whom correspondence should be addressed.

Academic Editor: Markus W. Sigrist

Received: 8 February 2016 / Revised: 14 March 2016 / Accepted: 23 March 2016 / Published: 25 March 2016

http://www.mdpi.com/1424-8220/16/4/439

We report on a quartz-enhanced photoacoustic (QEPAS) sensor for methanol (CH3OH) detection employing a novel quartz tuning fork (QTF), specifically designed to enhance the QEPAS sensing performance in the terahertz (THz) spectral range. A discussion of the QTF properties in terms of resonance frequency, quality factor and acousto-electric transduction efficiency as a function of prong sizes and spacing between the QTF prongs is presented. The QTF was employed in a QEPAS sensor system using a 3.93 THz quantum cascade laser as the excitation source in resonance with a CH3OH rotational absorption line located at 131.054 cm−1. A minimum detection limit of 160 ppb in 30 s integration time, corresponding to a normalized noise equivalent absorption NNEA = 3.75 × 10−11 cm−1W/Hz½, was achieved, representing a nearly one-order-of-magnitude improvement with respect to previous reports.

Abstract-Photo-generated metamaterials induce modulation of CW terahertz quantum cascade lasers.

Francesco P Mezzapesa, Lorenzo L Columbo, Carlo Rizza, Massimo Brambilla, Alessardro Ciattoni,Maurizio Dabbicco, Miriam S Vitiello, Gaetano Scamarcio

http://www.pubfacts.com/detail/26549166/Photo-generated-metamaterials-induce-modulation-of-CW-terahertz-quantum-cascade-lasers

Periodic patterns of photo-excited carriers on a semiconductor surface profoundly modifies its effective permittivity, creating a stationary all-optical quasi-metallic metamaterial. Intriguingly, one can tailor its artificial birefringence to modulate with unprecedented degrees of freedom both the amplitude and phase of a quantum cascade laser (QCL) subject to optical feedback from such an anisotropic reflector. Here, we conceive and devise a reconfigurable photo-designed Terahertz (THz) modulator and exploit it in a proof-of-concept experiment to control the emission properties of THz QCLs. Photo-exciting sub-wavelength metastructures on silicon, we induce polarization-dependent changes in the intra-cavity THz field, that can be probed by monitoring the voltage across the QCL terminals. This inherently flexible approach promises groundbreaking impact on THz photonics applications, including THz phase modulators, fast switches, and active hyperbolic media.

Abstract-Electronic temperatures of terahertz quantum cascade active regions with phonon scattering assisted injection and extraction scheme

Pietro Patimisco, Gaetano Scamarcio, Maria Vittoria Santacroce, Vincenzo Spagnolo, Miriam Serena Vitiello, Emmanuel Dupont, Sylvain R. Laframboise, Saeed Fathololoumi, Ghasem S. Razavipour, and Zbigniew Wasilewski

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-8-10172

We measured the lattice and subband electronic temperatures of terahertz quantum cascade devices based on the optical phonon-scattering assisted active region scheme. While the electronic temperature of the injector state (j = 4) significantly increases by ΔT = T_e⁴ – T_L ~40 K, in analogy with the reported values in resonant phonon scheme (ΔT ~70-110 K), both the laser levels (j = 2,3) remain much colder with respect to the latter (by a factor of 3-5) and share the same electronic temperature of the ground level (j = 1). The electronic population ratio n₂/n₁ shows that the optical phonon scattering efficiently depopulates the lower laser level (j = 2) up to an electronic temperature T_e ~180 K.
© 2013 OSA

Abstract-Electronic temperatures of terahertz quantum cascade active regions with phonon scattering assisted injection and extraction scheme

http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-21-8-10172&id=252863

Pietro Patimisco, Gaetano Scamarcio, Maria Vittoria Santacroce, Vincenzo Spagnolo, Miriam Serena Vitiello, Emmanuel Dupont, Sylvain R. Laframboise, Saeed Fathololoumi, Ghasem S. Razavipour, and Zbigniew Wasilewski

We measured the lattice and subband electronic temperatures of terahertz quantum cascade devices based on the optical phonon-scattering assisted active region scheme. While the electronic temperature of the injector state (j = 4) significantly increases by ΔT = T_e⁴ – T_L ~40 K, in analogy with the reported values in resonant phonon scheme (ΔT ~70-110 K), both the laser levels (j = 2,3) remain much colder with respect to the latter (by a factor of 3-5) and share the same electronic temperature of the ground level (j = 1). The electronic population ratio n₂/n₁ shows that the optical phonon scattering efficiently depopulates the lower laser level (j = 2) up to an electronic temperature T_e ~180 K.
© 2013 OSA