Broadband heterogeneous terahertz frequency quantum cascade laser

Li, L.H.; Garrasi, Katia; Kundu, Iman; Han, Yazhou; Salih, Mohammed; Vitiello, Miriam S.; Davies, A. G.; Linfield, Edmund H.

doi:10.1049/el.2018.6062

Cited by 27 publications

(26 citation statements)

References 12 publications

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“…The QCL comprises a 17‐µm‐thick GaAs/AlGaAs heterogeneous heterostructure, featuring a sequence of three active region modules with frequency‐detuned gain bandwidths [ 54 ] centered at 2.5, 3, and 3.5 THz. [ 65 ] The Fabry–Pérot device operates as frequency comb synthesizer over ~1.05 THz bandwidth, and shows a stable and narrow (4.15 kHz) beatnote over a continuous current range ~106 mA, corresponding to 15% of the laser operational range. Different to previous approaches, [ 66 ] we then engineer an etalon‐like interferometric scheme, in which the modulator is tightly coupled to the back facet of the THz QCL, at a distance ~50 µm, as required for an on‐resonance GTI.…”

Section: Resultsmentioning

confidence: 99%

Tunable, Grating‐Gated, Graphene‐On‐Polyimide Terahertz Modulators

Gaspare

Pogna

Salemi

et al. 2020

Adv Funct Materials

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An electrically switchable graphene terahertz (THz) modulator with a tunable‐by‐design optical bandwidth is presented and it is exploited to compensate the cavity dispersion of a quantum cascade laser (QCL). Electrostatic gating is achieved by a metal grating used as a gate electrode, with an HfO2/AlOx gate dielectric on top. This is patterned on a polyimide layer, which acts as a quarter wave resonance cavity, coupled with an Au reflector underneath. The authors achieve 90% modulation depth of the intensity, combined with a 20 kHz electrical bandwidth in the 1.9–2.7 THz range. The modulator is then integrated with a multimode THz QCL. By adjusting the modulator operational bandwidth, the authors demonstrate that the graphene modulator can partially compensate the QCL cavity dispersion, resulting in an integrated laser behaving as a stable frequency comb over 35% of the operational range, with 98 equidistant optical modes and a spectral coverage ~1.2 THz. This paves the way for applications in the terahertz, such as tunable transformation‐optics devices, active photonic components, adaptive and quantum optics, and metrological tools for spectroscopy at THz frequencies.

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Section: Resultsmentioning

confidence: 99%

Tunable, Grating‐Gated, Graphene‐On‐Polyimide Terahertz Modulators

Gaspare

Pogna

Salemi

et al. 2020

Adv Funct Materials

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“…The gain medium of each modules is respectively centered at 3.5 THz, 3.0 THz, and 2.5 THz. The average doping was set to 3 × 10 16 cm −3 32 . Laser bars were fabricated on a standard metal–metal processing that relies on Au–Au thermo-compression wafer bonding of the 17-μm-thick active region onto a highly doped GaAs substrate.…”

Section: Methodsmentioning

confidence: 99%

Fully phase-stabilized quantum cascade laser frequency comb

et al. 2019

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Miniaturized frequency comb sources across hard-to-access spectral regions, i.e. mid- and far-infrared, have long been sought. Four-wave-mixing based Quantum Cascade Laser combs (QCL-combs) are ideal candidates, in this respect, due to the unique possibility to tailor their spectral emission by proper nanoscale design of the quantum wells. We demonstrate full-phase-stabilization of a QCL-comb against the primary frequency standard, proving independent and simultaneous control of the two comb degrees of freedom (modes spacing and frequency offset) at a metrological level. Each emitted mode exhibits a sub-Hz relative frequency stability, while a correlation analysis on the modal phases confirms the high degree of coherence in the device emission, over different power-cycles and over different days. The achievement of fully controlled, phase-stabilized QCL-comb emitters proves that this technology is mature for metrological-grade uses, as well as for an increasing number of scientific and technological applications.

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“…Electrically pumped QCLs, in either standard [21][22][23] or DFG configurations [25], are the most compact on-chip sources of FCs at THz frequencies. QCLs have indeed some peculiar features that make them unique for devising FCs: the broad optical bandwidth (OB) (up to an octave) [22], the inherently high optical power levels (hundred mW in CW, W-in pulsed mode) [26][27][28] and the high spectral purity (intrinsic linewidths of ∼100 Hz) [29]. Such a combination of specs recently allowed designing THz QCL FCs covering an OB ≤ 1.2 THz [22,23] delivering CW optical powers of 4-8 mW [23,30] with a THz power/comb tooth in the 3 µW [31] to 6 µW [21] range in standard double-metal configurations and hundred nW in the DFG configuration [25].…”

Section: Quantum Cascade Laser Frequency Combs At Thz Frequencies: Armentioning

confidence: 99%

Toward new frontiers for terahertz quantum cascade laser frequency combs

et al. 2020

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Broadband, quantum-engineered, quantum cascade lasers (QCLs) are the most powerful chip-scale sources of optical frequency combs (FCs) across the mid-infrared and the terahertz (THz) frequency range. The inherently short intersubband upper state lifetime spontaneously allows mode proliferation, with large quantum efficiencies, as a result of the intracavity four-wave mixing. QCLs can be easily integrated with external elements or engineered for intracavity embedding of nonlinear optical components and can inherently operate as quantum detectors, providing an intriguing technological platform for on-chip quantum investigations at the nanoscale. The research field of THz FCs is extremely vibrant and promises major impacts in several application domains crossing dual-comb spectroscopy, hyperspectral imaging, time-domain nanoimaging, quantum science and technology, metrology and nonlinear optics in a miniaturized and compact architecture. Here, we discuss the fundamental physical properties and the technological performances of THz QCL FCs, highlighting the future perspectives of this frontier research field.

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Broadband heterogeneous terahertz frequency quantum cascade laser

Cited by 27 publications

References 12 publications

Tunable, Grating‐Gated, Graphene‐On‐Polyimide Terahertz Modulators

Tunable, Grating‐Gated, Graphene‐On‐Polyimide Terahertz Modulators

Fully phase-stabilized quantum cascade laser frequency comb

Toward new frontiers for terahertz quantum cascade laser frequency combs

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