Metasurface external cavity laser

Xu, Luyao; Curwen, Christopher A.; Hon, Philip W. C.; Chen, Qi-Sheng; Itoh, T.; Williams, Benjamin S.

doi:10.1063/1.4936887

Cited by 81 publications

(48 citation statements)

References 25 publications

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“…A THz vertical-external-cavity surface-emitting-laser (VECSEL) formed by an active metasurface reflector and a flat output coupler reflector was proposed to address this challenge [30]. Lasing was possible when the meta-surface reflector was placed into a low-loss external cavity such that the external cavity determined the beam properties.…”

Section: Developments Of Phase-locked Arrays Of Thz Qclsmentioning

confidence: 99%

“…Obtaining the coherence within an array relies on the ability to control the coupling between individual lasers. Inspired by concepts developed in more mature, shorter wavelength diode laser systems, several coupling schemes, including coupling through exponentially decaying fields outside the high index dielectric core (evanescent-wave coupled) [27][28][29], through feedback from external reflectors (diffraction-wave coupled) [30], connecting two ridges to one single-mode waveguide (Y coupled or tree coupled) [31][32][33][34][35], through lateral propagating waves (leaky-wave coupled) [36][37][38] and combining gradedphotonic-heterostructure (GPH) QCLs with a ring resonator [39], have exhibited excellent performance on phase-locking QCL arrays, especially in mid-infrared range.…”

Section: Brief Review Of Qcl Arraysmentioning

confidence: 99%

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Power Amplification and Coherent Combination Techniques for Terahertz Quantum Cascade Lasers

Xie¹,

Li²,

Wang³

et al. 2017

Quantum Cascade Lasers

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Power amplification and coherent combination are important ways to improve the output power and beam quality of single-mode terahertz quantum cascade lasers (THz QCLs). Up to date, the tapered waveguide is the most convenient way to amplify the power of THz QCLs. The self-focusing effect in tapered THz QCLs induces nonmonotonic behaviours of the peak power and far-field beam divergence, which lead to the existence of optimal structural parameters. The surface and lateral grating techniques have also been employed in tapered THz QCLs to further improve the spectral purity. For coherent combinations, the progress of facet-emitting phase-locked arrays of THz QCLs is still limited due to both the lack of the understanding of dynamics of coupled QCLs and the difficulties in designing high-performance coupled waveguides. We will briefly review the developments of coherent arrays of THz QCLs and present a design of monolithic QCL arrays with common coupled cavity to achieve the optical mutual injection, which may provide a new way for coherent combination of THz QCLs.

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Section: Developments Of Phase-locked Arrays Of Thz Qclsmentioning

confidence: 99%

Section: Brief Review Of Qcl Arraysmentioning

confidence: 99%

Power Amplification and Coherent Combination Techniques for Terahertz Quantum Cascade Lasers

Xie¹,

Li²,

Wang³

et al. 2017

Quantum Cascade Lasers

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“…Recently, emission beam with the very low divergence angle (<10 Â 10 ) has been demonstrated in a phased array of THz-QCLs and a THz-QCL vertical-external-cavity surfaceemitting-laser. 13,16 In the THz-MOPA-QCL, the beam divergence is determined by the dimensions of the emission aperture. Therefore, a tapered PA section with a widened diffraction grating will efficiently decrease the divergence angle.…”

Section: à3mentioning

confidence: 99%

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17] Related results include third-order distributed feedback (DFB) lasers, 5,6 second-order DFB THzQCLs with dual slits, 7 THz-QCLs with a graded photonic heterostructure resonator, [9][10][11] phase-locked arrays of secondorder DFB lasers, [12][13][14] etc. However, to ensure that lasing occurs on transverse and longitudinal single-mode, the dimensions of the photonic coupling structure must be limited, thus restricting the available output power and increasing the divergence of the emitted beam.…”

mentioning

confidence: 99%

Terahertz master-oscillator power-amplifier quantum cascade lasers

Zhu

Wang

Yan

et al. 2016

Applied Physics Letters

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We report on the realization of a monolithically integrated master-oscillator power-amplifier architecture in a terahertz quantum cascade laser (THz-QCL) with a metal-metal waveguide. The master-oscillator section is a first-order distributed feedback (DFB) laser. Instead of using a thick anti-reflection coating, we exploit a diffraction grating together with an absorbing boundary in the power-amplifier section to efficiently extract the laser radiation and suppress the self-lasing in it. The devices demonstrate a stable generation and power amplification of single-mode emission. The amplification factor is about 5, and the output power is approximately twice that of the standard second-order DFB lasers fabricated from the same material. Emission beam pattern with a divergence angle of $18 Â 40 is achieved. Our work provides an avenue for the realization of singlemode THz-QCLs with high output power and good beam quality. Published by AIP Publishing.[http://dx.doi.org/10.1063/1.4969067] Terahertz quantum cascade lasers (THz-QCLs) with single-mode emission are highly desired for applications such as spectroscopy, trace gas detection, and free space communication.1-3 Intensive studies have been devoted to develop unique photonic coupling structures in order to approach a high output power and a directional beam pattern for singlemode THz-QCLs. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] Related results include third-order distributed feedback (DFB) lasers, 5,6 second-order DFB THzQCLs with dual slits, 7 THz-QCLs with a graded photonic heterostructure resonator, 9-11 phase-locked arrays of secondorder DFB lasers, 12-14 etc. However, to ensure that lasing occurs on transverse and longitudinal single-mode, the dimensions of the photonic coupling structure must be limited, thus restricting the available output power and increasing the divergence of the emitted beam.Monolithically integrated master-oscillator power-amplifier (MOPA) is a promising architecture to realize single-mode emission with a high output power and a near diffractionlimited beam quality. It has been implemented in near-infrared diode lasers and also in mid-infrared quantum cascade lasers. [18][19][20][21][22] In order to suppress the self-lasing in the poweramplifier (PA) section and to fully exploit the material gain, the front facet of the PA section needs to be coated by antireflection (AR) layers. However, extending the MOPA architecture to the THz frequency range is a challenge because of the lack of suitable AR coatings.Only a few researches related to MOPA devices based on THz quantum cascade structures have been reported. 23,24 In these devices-which are based on a single plasmon waveguide-the master oscillator (MO) section is a Fabry-P erot laser and is separated from the PA section by a deep air gap. The PA section is another Fabry-P erot cavity with one facet angled or coated by a thick parylene layer. The Fabry-P erot MO section intrinsically results in multimode emission, while the deep air gap degrades the coupling efficiency o...

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“…Such devices, with elongated resonators coupled to an external cavity, have been recently reported but only in the case of a thick active region (>10 lm) and much larger modal volume. 21 Considering the high field confinement and hence high power densities enabled by square patch microcavities, these are a promising means to realize sources based on optical nonlinearities, such as up conversion or second harmonic generation.…”

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confidence: 99%

Patch antenna microcavity terahertz sources with enhanced emission

Madéo

Todorov

Gilman

et al. 2016

Applied Physics Letters

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We study the emission properties of an electroluminescent THz frequency quantum cascade structure embedded in an array of patch antenna double-metal microcavities. We show that high photon extraction efficiencies can be obtained by adjusting the active region thickness and array periodicity as well as high Purcell factors (up to 65), leading to an enhanced overall emitted power. Up to a 44-fold increase in power is experimentally observed in comparison with a reference device processed in conventional mesa geometry. Estimation of the Purcell factors using electromagnetic simulations and the theoretical extraction efficiency are in agreement with the observed power enhancement and show that, in these microcavities, the overall enhancement solely depends on the square of the total quality factor. Published by AIP Publishing. The ability to realize efficient sources and detectors at terahertz (THz) frequencies is of importance as this opens the way to a wide range of potential applications in molecular spectroscopy, imaging, security scanning, and in the fundamental studies of low energy chemical and physical processes.1 For optoelectronic devices operating in the THz range, the light-matter interaction can be significantly enhanced by confining the electromagnetic field into highly sub-wavelength metallic structures. Effective volumes as low as 10, where k is the radiation wavelength, have been achieved in passive double-metal micro-cavities comprising a dielectric layer bounded by a metallic back-plane and a patterned top metal layer.2 Similarly, Purcell enhancement of spontaneous emission has been observed in LC microresonators as well as mirror-grating metal cavities 3,4 and microcavity effects for THz quantum cascade lasers have been discussed. 5,6 Double-metal confinement lends itself to the creation of arrays of patch antenna microcavities and has led to the demonstration of the ultra-strong lightmatter coupling regime and the realization of efficient infrared and THz detectors. [7][8][9] In the case of square resonators, the resonant wavelength, k, is set by the length of the square side, s, through the formula s ¼ k/2n eff, where n eff is the effective mode index. This photonic structure is ideal for intersubband (ISB) emitters as the oscillating dipoles of the electronic transition align with the intracavity TM mode polarization. In addition, this geometry behaves as a patch antenna, rotating the polarization of the confined field by 90 when radiating into the far-field. Therefore, one can realize surface emitting photonic devices in which the light-matter interaction can be enhanced by resonantly tuning the energy of the microcavity mode with a radiative ISB transition by adjusting only the geometric parameter s. 10In this letter, we study THz frequency emission from arrays of double-metal patch microcavities containing a quantum cascade (QC) active region. We demonstrate the enhancement of the electroluminescence owing to an efficient out-coupling that is achieved by carefully choosing the thickness of ...

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Metasurface external cavity laser

Cited by 81 publications

References 25 publications

Power Amplification and Coherent Combination Techniques for Terahertz Quantum Cascade Lasers

Power Amplification and Coherent Combination Techniques for Terahertz Quantum Cascade Lasers

Terahertz master-oscillator power-amplifier quantum cascade lasers

Patch antenna microcavity terahertz sources with enhanced emission

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