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Biasco S, Beere HE, Ritchie DA, Li L, Davies AG, Linfield EH, Vitiello MS. Frequency-tunable continuous-wave random lasers at terahertz frequencies. LIGHT, SCIENCE & APPLICATIONS 2019; 8:43. [PMID: 31044073 PMCID: PMC6491491 DOI: 10.1038/s41377-019-0152-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 03/20/2019] [Accepted: 04/02/2019] [Indexed: 06/09/2023]
Abstract
Random lasers are a class of devices in which feedback arises from multiple elastic scattering in a highly disordered structure, providing an almost ideal light source for artefact-free imaging due to achievable low spatial coherence. However, for many applications ranging from sensing and spectroscopy to speckle-free imaging, it is essential to have high-radiance sources operating in continuous-wave (CW). In this paper, we demonstrate CW operation of a random laser using an electrically pumped quantum-cascade laser gain medium in which a bi-dimensional (2D) random distribution of air holes is patterned into the top metal waveguide. We obtain a highly collimated vertical emission at ~3 THz, with a 430 GHz bandwidth, device operation up to 110 K, peak (pulsed) power of 21 mW, and CW emission of 1.7 mW. Furthermore, we show that an external cavity formed with a movable mirror can be used to tune a random laser, obtaining continuous frequency tuning over 11 GHz.
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Affiliation(s)
- Simone Biasco
- NEST, CNR – Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Harvey E. Beere
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE UK
| | - David A. Ritchie
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE UK
| | - Lianhe Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT UK
| | - A. Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT UK
| | - Edmund H. Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT UK
| | - Miriam S. Vitiello
- NEST, CNR – Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
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Szedlak R, Hisch T, Schwarz B, Holzbauer M, MacFarland D, Zederbauer T, Detz H, Andrews AM, Schrenk W, Rotter S, Strasser G. Ring quantum cascade lasers with twisted wavefronts. Sci Rep 2018; 8:7998. [PMID: 29789653 PMCID: PMC5964118 DOI: 10.1038/s41598-018-26267-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/09/2018] [Indexed: 11/15/2022] Open
Abstract
We demonstrate the on-chip generation of twisted light beams from ring quantum cascade lasers. A monolithic gradient index metamaterial is fabricated directly into the substrate side of the semiconductor chip and induces a twist of the light's wavefront. This significantly influences the obtained beam pattern, which changes from a central intensity minimum to a maximum depending on the discontinuity count of the metamaterial. Our design principle provides an interesting alternative to recent implementations of microlasers operating at an exceptional point.
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Affiliation(s)
- Rolf Szedlak
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria.
| | - Thomas Hisch
- Institute for Theoretical Physics, TU Wien, Wiedner-Hauptstraße 8-10/136, 1040, Vienna, Austria
| | - Benedikt Schwarz
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
| | - Martin Holzbauer
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
| | - Donald MacFarland
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
| | - Tobias Zederbauer
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
| | - Hermann Detz
- Austrian Academy of Sciences, Dr. Ignaz Seipel-Platz 2, 1010, Vienna, Austria
| | - Aaron Maxwell Andrews
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
| | - Werner Schrenk
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
| | - Stefan Rotter
- Institute for Theoretical Physics, TU Wien, Wiedner-Hauptstraße 8-10/136, 1040, Vienna, Austria
| | - Gottfried Strasser
- Institute of Solid State Electronics & Center for Micro- and Nanostructures, TU Wien, Floragasse 7, 1040, Vienna, Austria
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Abstract
Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states with pseudogaps in the energy spectrum, but lacking translational invariance, they also intrinsically feature a pattern of 'defects', which can give rise to critically localized modes confined in space, similar to Anderson modes in random structures. If used as laser resonators, photonic quasi-crystals open up design possibilities that are simply not possible in a conventional periodic photonic crystal. In this letter, we exploit the concept of a 2D photonic quasi crystal in an electrically injected laser; specifically, we pattern the top surface of a terahertz quantum-cascade laser with a Penrose tiling of pentagonal rotational symmetry, reaching 0.1-0.2% wall-plug efficiencies and 65 mW peak output powers with characteristic surface-emitting conical beam profiles, result of the rich quasi-crystal Fourier spectrum.
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