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Title: Terahertz plasmonic laser radiating in an ultra-narrow beam

Abstract

Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) that is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast tomore » a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity irrespective of its operating wavelength and could bring plasmonic lasers closer to practical applications.« less

Authors:
 [1];  [1];  [2];  [1]
  1. Lehigh Univ., Bethlehem, PA (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1325914
Report Number(s):
SAND-2016-8998J
Journal ID: ISSN 2334-2536; 647337
Grant/Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Optica
Additional Journal Information:
Journal Volume: 3; Journal Issue: 7; Journal ID: ISSN 2334-2536
Publisher:
Optical Society of America
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; lasers; distributed-feedback; semiconductor lasers; quantum cascade; surface plasmons

Citation Formats

Wu, Chongzhao, Khanal, Sudeep, Reno, John L., and Kumar, Sushil. Terahertz plasmonic laser radiating in an ultra-narrow beam. United States: N. p., 2016. Web. doi:10.1364/optica.3.000734.
Wu, Chongzhao, Khanal, Sudeep, Reno, John L., & Kumar, Sushil. Terahertz plasmonic laser radiating in an ultra-narrow beam. United States. https://doi.org/10.1364/optica.3.000734
Wu, Chongzhao, Khanal, Sudeep, Reno, John L., and Kumar, Sushil. 2016. "Terahertz plasmonic laser radiating in an ultra-narrow beam". United States. https://doi.org/10.1364/optica.3.000734. https://www.osti.gov/servlets/purl/1325914.
@article{osti_1325914,
title = {Terahertz plasmonic laser radiating in an ultra-narrow beam},
author = {Wu, Chongzhao and Khanal, Sudeep and Reno, John L. and Kumar, Sushil},
abstractNote = {Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) that is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity irrespective of its operating wavelength and could bring plasmonic lasers closer to practical applications.},
doi = {10.1364/optica.3.000734},
url = {https://www.osti.gov/biblio/1325914}, journal = {Optica},
issn = {2334-2536},
number = 7,
volume = 3,
place = {United States},
year = {Thu Jul 07 00:00:00 EDT 2016},
month = {Thu Jul 07 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 33 works
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Figures / Tables:

Fig. 1 Fig. 1: The antenna-feedback concept for spasers. (a) The general principle of conventional distributed-feedback (DFB) that could be implemented in a spaser by introducing periodicity in its metallic cladding. A parallel-plate metallic cavity is illustrated; however, the principle is equally applicable to spaser cavities with a single metal-cladding. (b) Ifmore » the periodicity in (a) is implemented by making holes or slits in the metal-cladding, the guided SPP wave diffracts out through the apertures and generates single-sided SPP waves on the cladding in the surrounding medium. The figure shows phase-mismatch between successive apertures for SPP waves on either side of the cladding. Coherent single-sided SPP waves in the surrounding medium cannot therefore be sustained owing to destructive interference with the guided SPP wave inside the cavity, as illustrated in (c). (d) Principle of an antenna-feedback grating. If the periodicity in the metal film allows the guided SPP mode to diffract outside the cavity, a grating period could be chosen that leads to the first-order Bragg diffraction in the opposite direction, but in the surrounding medium rather than inside the active medium itself. Similarly, the single-sided SPP mode in the surrounding medium undergoes first-order Bragg diffraction to couple with the guided SPP wave in the opposite direction inside the cavity. (e) The grating in (d) leads to a fixed phase-condition at each aperture between counter propagating SPP waves on the either side of metal-cladding. First, this leads to significant build up of amplitude in the single-sided SPP wave in the surrounding medium, as illustrated in (f). Second, emission from each aperture adds constructively to couple to far-field radiation in the end-fire (z) direction. As argued in the text, both of these aspects lead to narrow far-field emission profile in the x - y plane.« less

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Works referencing / citing this record:

Photonic Engineering Technology for the Development of Terahertz Quantum Cascade Lasers
journal, July 2019


Continuous-wave highly-efficient low-divergence terahertz wire lasers
journal, March 2018


High power surface emitting terahertz laser with hybrid second- and fourth-order Bragg gratings
journal, April 2018


Phase-locked photonic wire lasers by π coupling
journal, December 2018


Large static tuning of narrow-beam terahertz plasmonic lasers operating at 78K
journal, February 2017


Electrical tuning of a terahertz quantum cascade laser based on detuned intersubband absorption
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Eigenmodes of a lamellar optical grating: Profile, propagation, reflection, transmission, and nonadiabatic mode coupling
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Terahertz plasmonic lasers with narrow beams and large tunability
conference, February 2017


Terahertz polarization-maintaining subwavelength filters
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High-intensity and low-divergence THz laser with 1D autofocusing symmetric Airy beams
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Key Roles of Plasmonics in Wireless THz Nanocommunications—A Survey
journal, December 2019


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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.