摘要:
An opto-electronic oscillator (10) comprising: an optical source (12) to generate an optical carrier signal having a carrier wavelength; an optical phase modulator (14) to apply a sinusoidal phase modulation to the optical carrier signal to generate two first order sidebands having a π phase difference between them; an optical phase shifter (16) comprising an optical resonator configured to apply a substantially π phase-shift to one of the first order sidebands at a preselected wavelength within an optical spectrum of said first order sideband; and a photodetector (18) configured to perform optical heterodyne detection of the optical carrier signal with both: said one of the first order sidebands substantially π phase shifted by the optical resonator; and the other of the first order sidebands, to generate an electrical carrier signal (20), and wherein a first part of the electrical carrier signal (20a) is delivered to an electrical output (22) and a second part of the electrical carrier signal (20b) is delivered to the optical phase modulator as a drive signal.
摘要:
Die Erfindung betrifft ein Verfahren, mit dem aus Terahertz-Pulsen örtlich und zeitlich separierte Terahertz-Subpulse mit eindeutiger Zeit-Ort-Beziehung erzeugt werden, welche die Möglichkeit ortsaufgelöster Messungen mittels THz-Zeitbereichsspektroskopie eröffnen, ferner eine Messeinrichtung zur Realisierung dieses Verfahrens, aufweisend ein THz-Zeitbereichsspektrometer mit einer erfindungsgemäßen Optik zur Erzeugung solcher THz-Subpulse, ein modular aufgebautes Messsystem mit mindestens einer solchen Messeinrichtung sowie eine Verwendung des Verfahrens, der Messeinrichtung und des Messsystems zur Fehlererkennung und -lokalisierung, insbesondere zur zerstörungsfreien Inline-Qualitätskontrolle bei der kontinuierlichen industriellen Fertigung bandförmiger Endlosprodukte, z. B. Papier- und Kunststoffbahnen, mit elektromagnetischer Strahlung im THz-Bereich.
摘要:
The generation of terahertz electromagnetic radiation, using a laser which is incident upon an electrically biased photoconductor and an antenna. The device has a layered structure comprising a semiconductor substrate below a wetting layer (55) epitaxially grown on the substrate, barrier layers (57) are positioned above and below a quantum dot layer (59). A contact layer (60) is provided with a contact (61) which couples the quantum dot structure to a voltage source (63). The reduction of the carrier lifetime in a conducting state, allied to its high carrier mobility that is possibly comparable to that of bulk GaAs can provide fast photoconductive devices and produce sources of terahertz radiation.
摘要:
The invention relates to a terahertz modulator (1) to be used in a given frequency band of use. Said modulator comprises a polar semi-conductor crystal (330) having a Reststrahlen band that covers said frequency band of use, and comprising at least one interface with a dielectric means; coupling means (330) enabling the resonant coupling of an interface phonon polariton (IPhP) supported by said interface and an incident radiation (2) having a pre-determined frequency within said band of use; and control means (22) that can modify the intensity of the coupling between said interface phonon polariton and said incident radiation (2) by modifying the dielectric function of the polar crystal in the Reststrahlen band of the polar crystal (10).