Vertically emitting microdisk lasers

Mahler, L.; Tredicucci, Alessandro; Green, R.P.; Beltram, Fabio; Walther, Christoph; Faist, Jérôme; Beere, Harvey E.; Ritchie, D. A.

doi:10.1038/nphoton.2008.248

Cited by 121 publications

(60 citation statements)

References 23 publications

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“…Thus, the experiment indeed demonstrates that almost diffraction limited beams can be obtained, implying in-phase coherent emission from the laser surface leading to a Gaussian-like far-field due to constructive interference, similar to a 2nd order DFB laser. The distinctive feature of the presented random lasers compared to previously demonstrated concepts [14][15][16][17][18]20] is the fact that the far-fields consist of multiple spectral components. Although different scattering configurations with the same filling fraction show different emission patterns (see Fig.…”

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confidence: 95%

Random lasers for broadband directional emission

Schönhuber

Brandstetter

Hisch

et al. 2016

Optica

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Broadband coherent light sources are becoming increasingly important for sensing and spectroscopic applications, especially in the mid-infrared and terahertz (THz) spectral regions, where the unique absorption characteristics of a whole host of molecules are located. The desire to miniaturize such light emitters has recently lead to spectacular advances with compact on-chip lasers that cover both of these spectral regions. The long wavelength and the small size of the sources result in a strongly diverging laser beam that is difficult to focus on the target that one aims to perform spectroscopy with. Here, we introduce an unconventional solution to this vexing problem relying on a random laser to produce coherent broadband THz radiation as well as an almost diffraction limited far-field emission profile. Our random lasers do not require any fine-tuning and thus constitute a promising example of practical device applications for random lasing.Various spectroscopic techniques rely on the specific absorption features of numerous molecules within the midinfrared and terahertz (THz) spectral regions, which allow their unambiguous identification. Although broadband coherent sources of radiation are already available within these frequency regions [1][2][3][4][5], a compact size and electrically pumped operation are additionally desired for actual applications. These criteria are fulfilled by quantum cascade lasers (QCLs), semiconductor sources which are able to provide broadband emission at mid-infrared [6,7] and THz [8,9] frequencies. However, for typically used THz QCL waveguides the output aperture is on the order of 10 µm, while the emission wavelength is about 100 µm. This, in fact, leads to a very divergent output beam, which is additionally distorted by interference effects [10,11]. Since external optical elements such as lenses or antennas are difficult to handle on a large scale [12,13], several monolithic concepts have been pursued to address this issue. To improve the far-field for facet emission, e.g., a 3rd order distributed feedback (DFB) grating can be used [14]. Another approach is to coherently emit from a large area on the laser surface. In contrast to interband semiconductor lasers, QCLs can only generate in-plane radiation due to intersubband selection rules, preventing the realization of VCSELtype resonators. Thus several concepts have been developed to couple out the in-plane cavity mode in vertical direction, including 2nd order DFB gratings [15,16] , and photonic crystal (PhC) cavities [17]. Recently, also non-periodic resonator structures such as graded photonic heterostructures [18], or quasicrystal cavities [19,20] have been developed. However, all on-chip techniques providing surface emission demonstrated so far are designed to support a single laser mode only, while for many spectroscopic applications a broadband coherent light source is necessary. To achieve the objective of a broadband and at the same time very collimated laser light emission in the THz regime, we propose here a radical ...

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confidence: 95%

Random lasers for broadband directional emission

Schönhuber

Brandstetter

Hisch

et al. 2016

Optica

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“…Specifically, we aim to obtain significantly higher powers than have been observed to date using either 2D photonic crystals [12][13][14][15][16][17][18] or second-order DFB gratings. [19][20][21][22][23][24] Recently, we have demonstrated surface-emitting THz QCLs based on graded photonic heterostructure (GPH) resonators (shown schematically in Fig. 1(a)).…”

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confidence: 99%

Surface-emitting terahertz quantum cascade lasers with continuous-wave power in the tens of milliwatt range

Isac

et al. 2014

Appl. Phys. Lett.

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We demonstrate efficient surface-emitting terahertz frequency quantum cascade lasers with continuous wave output powers of 20-25 mW at 15 K and maximum operating temperatures of 80-85 K. The devices employ a resonant-phonon depopulation active region design with injector, and surface emission is realized using resonators based on graded photonic heterostructures (GPHs). GPHs can be regarded as energy wells for photons and have recently been implemented through grading the period of the photonic structure. In this paper, we show that it is possible to keep the period constant and grade instead the lateral metal coverage across the GPH. This strategy ensures spectrally singlemode operation across the whole laser dynamic range and represents an additional degree of freedom in the design of confining potentials for photons. V C 2014 AIP Publishing LLC.

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“…The perfect destructive interference is lost, and the attendant surface emission is observed. This idea has been applied to THz QCLs, first in a work on microdisks [27] and soon afterwards by the implementation of ring geometries [29,42]. Circular geometries for DFB structures are particularly appealing, because they naturally incorporate the best possible approximation of an infinite grating, thus resolving issues like the reduced yield of single-mode lasers due to uncontrolled positions of facets.…”

Section: Circular Resonatorsmentioning

confidence: 99%

“…The thin layers can, however, be incorporated in a different way: the full material stack is analyzed with a slab waveguide model; the full model is then created with bodies of resulting effective refractive index and perfect electric conductors (E t = 0) representing the involved metal sheets. Such models have been successfully used to simulate microdisk resonators [26,27] like the ones shown in Fig. 2, or, by taking into account mirror symmetries, linear DFB resonators [19,20,25].…”

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confidence: 99%

Photonic engineering of surface‐emitting terahertz quantum cascade lasers

Mahler

Tredicucci

2011

Laser & Photonics Reviews

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Various resonators for surface emission are reviewed that have recently been developed to improve radiative- and collection-efficiencies of terahertz quantum cascade lasers (THz QCL). While the fabrication of waveguides for long wavelengths is challenging in terms of molecular beam epitaxy, long wavelengths also provide a wonderful testbed for new photonics structure concepts, since these can be easily produced by conventional optical lithography because of the typically large size of the required features. This led to novel geometries, like one-and two-dimensional non-periodic photonic crystals, or circular gratings for microdisk- and ring-lasers, which are all implemented by simply patterning the top metal cladding of a metal-metal wave-guide. The modeling of such resonators with the finite element method is also described, highlighting the importance of this tool for the engineering of surface losses and far-field patterns

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Vertically emitting microdisk lasers

Cited by 121 publications

References 23 publications

Random lasers for broadband directional emission

Random lasers for broadband directional emission

Surface-emitting terahertz quantum cascade lasers with continuous-wave power in the tens of milliwatt range

Photonic engineering of surface‐emitting terahertz quantum cascade lasers

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