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Title: Multiple lobes in the far-field distribution of terahertz quantum-cascade lasers due to self-interference

Abstract

The far-field distribution of the emission intensity of terahertz (THz) quantum-cascade lasers (QCLs) frequently exhibits multiple lobes instead of a single-lobed Gaussian distribution. We show that such multiple lobes can result from self-interference related to the typically large beam divergence of THz QCLs and the presence of an inevitable cryogenic operation environment including optical windows. We develop a quantitative model to reproduce the multiple lobes. We also demonstrate how a single-lobed far-field distribution can be achieved.

Authors:
; ; ;  [1]
  1. Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5–7, 10117 Berlin (Germany)
Publication Date:
OSTI Identifier:
22611530
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 6; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BEAMS; DISTRIBUTION; EMISSION; GAUSS FUNCTION; INTERFERENCE; LASERS; OPACITY; OPERATION; THZ RANGE

Citation Formats

Röben, B., E-mail: roeben@pdi-berlin.de, Wienold, M., Schrottke, L., and Grahn, H. T. Multiple lobes in the far-field distribution of terahertz quantum-cascade lasers due to self-interference. United States: N. p., 2016. Web. doi:10.1063/1.4953596.
Röben, B., E-mail: roeben@pdi-berlin.de, Wienold, M., Schrottke, L., & Grahn, H. T. Multiple lobes in the far-field distribution of terahertz quantum-cascade lasers due to self-interference. United States. doi:10.1063/1.4953596.
Röben, B., E-mail: roeben@pdi-berlin.de, Wienold, M., Schrottke, L., and Grahn, H. T. 2016. "Multiple lobes in the far-field distribution of terahertz quantum-cascade lasers due to self-interference". United States. doi:10.1063/1.4953596.
@article{osti_22611530,
title = {Multiple lobes in the far-field distribution of terahertz quantum-cascade lasers due to self-interference},
author = {Röben, B., E-mail: roeben@pdi-berlin.de and Wienold, M. and Schrottke, L. and Grahn, H. T.},
abstractNote = {The far-field distribution of the emission intensity of terahertz (THz) quantum-cascade lasers (QCLs) frequently exhibits multiple lobes instead of a single-lobed Gaussian distribution. We show that such multiple lobes can result from self-interference related to the typically large beam divergence of THz QCLs and the presence of an inevitable cryogenic operation environment including optical windows. We develop a quantitative model to reproduce the multiple lobes. We also demonstrate how a single-lobed far-field distribution can be achieved.},
doi = {10.1063/1.4953596},
journal = {AIP Advances},
number = 6,
volume = 6,
place = {United States},
year = 2016,
month = 6
}
  • There has been growing interest in the use of terahertz (THz) quantum cascade lasers (QCLs) for sensing applications. However, the lack of compact and sensitive THz detectors has limited the potential for commercial exploitation of sensors based on these devices. We have developed a self-mixing sensing technique in which THz QCLs are used for both generation and interferometric sensing of THz radiation, eliminating the need for a separate detector. Using this technique, we have measured the displacement of a remote target, both with and without opaque (in the visible spectrum) materials in the beam path and demonstrated a stand-off distancemore » of up to 7 m in air.« less
  • We report two-dimensional apertureless near-field terahertz (THz) imaging using a quantum cascade laser (QCL) source and a scattering probe. A near-field enhancement of the scattered field amplitude is observed for small tip-sample separations, allowing image resolutions of ∼1 μm (∼λ/100) and ∼7 μm to be achieved along orthogonal directions on the sample surface. This represents the highest resolution demonstrated to date with a THz QCL. By employing a detection scheme based on self-mixing interferometry, our approach offers experimental simplicity by removing the need for an external detector and also provides sensitivity to the phase of the reinjected field.
  • We report the demonstration of distributed-feedback terahertz quantum-cascade lasers based on a first-order grating fabricated via a lateral corrugation in a double-sided metal ridge waveguide. The phase of the facet reflection was precisely set by lithographically defined facets by dry etching. Single-mode emission was observed at low to moderate injection currents, although multimode emission was observed far beyond threshold owing to spatial hole burning. Finite-element simulations were used to calculate the modal and threshold characteristics for these devices, with results in good agreement with experiments.
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