Active phase-nulling of the self-mixing phase in a terahertz frequency quantum cascade laser

We demonstrate an active phase-nulling scheme for terahertz (THz) frequency quantum cascade lasers (QCLs) under optical feedback, by active electronic feedback control of the emission frequency. Using this scheme the frequency tuning rate of a THz QCL is characterised, with significantly reduced experimental complexity compared to alternative approaches. Furthermore, we demonstrate real-time displacement sensing of targets, overcoming the resolution limits imposed by quantisation in previously-implemented fringe counting methods. Our approach is readily applicable to high-frequency vibrometry and surface profiling of targets, as well as frequency-stabilisation schemes for THz QCLs

Phase-locking of a 2.7-THz quantum cascade laser to a mode-locked erbium-doped fibre laser

We demonstrate phase-locking of a 2.7-THz metalmetal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier-chain (x2x3x2) from a microwave synthesizer at 15 GHz. Both laser and reference radiations are coupled into a hot electron bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. Spectral analysis of the beat signal (see fig. 1) confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range

The Prospect of the Russian Language in Georgia. Insights from the Educated Youth

After the collapse of the Soviet Union, the status of the Russian language in the new-born Republics became a central issue. In the Southern Caucasus, all the Constitutions promulgated by the three Republics opted for ethnocentric language policies that accepted the titular language as the only State Language. However, the role of the Russian language as a lingua franca remained crucial for international communication and everyday interaction. It followed that it continued to play an important role also in education. The present study focuses on Georgia, where a strong derussification policy has taken place in the last decades and aims at understanding to what extent the use of Russian among the young generations has contracted. In particular, we present an analysis conducted on data collected via (i) a survey for young people consisting of questions on their sociolinguistic background and a proficiency test in Russian, and (ii) semi-structured interviews for teachers of Russian and English as Foreign Languages on the research topics

Cimbrian as a Test Case for Synchronic and Diachronic Language Variation: a Conceptual Approach for the Information Space

In this paper we present the effort made to define a conceptual approach for the information space entailed by a multidisciplinary and collaborative project, named ``Cimbrian as a test case for synchronic and diachronic language variation'', which provides linguists with a test bed for formal hypotheses concerning human language. Aims of the project are to collect, digitize and tag linguistic data from the German variety of Cimbrian~--~spoken in three relevant areas of northern Italy: Giazza (VR), Luserna (TN), and Roana (VI)~--~and to make available on-line a valuable and innovative linguistic resource for the in-depth study of Cimbrian. The task is addressed by a multidisciplinary team of linguists and computer scientists who, combining their competence, aim to make available new tools for linguistic analysis