Silicon integrated terahertz quantum cascade ring laser frequency comb

Jaidl, M.; Opačak, Nikola; Kainz, Martin A.; Theiner, Dominik; Limbacher, Benedikt; Beiser, Maximilian; Giparakis, Miriam; Andrews, A. M.; Strasser, G.; Schwarz, Benedikt; Darmo, J.; Unterrainer, K.

doi:10.1063/5.0078749

Cited by 12 publications

(7 citation statements)

References 28 publications

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“…Recent advances in the high-temperature operation of these devices 6 , 7 , combined with their frequency agility 8 and the possibility to operate as frequency combs 9 , 10 as well as very fast detectors 11 make them extremely appealing as key building blocks for THz photonics. Some of the previous approaches to THz integration include hybrid plasmonic waveguides 12 , monolithically integrated THz transceivers 13 , coupled cavity devices 14 , and most recently devices integrated on silicon 15 .…”

Section: Introductionmentioning

confidence: 99%

Planarized THz quantum cascade lasers for broadband coherent photonics

et al. 2022

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Recently, there has been a growing interest in integrated THz photonics for various applications in communications, spectroscopy and sensing. We present a new integrated photonic platform based on active and passive elements integrated in a double-metal, high-confinement waveguide layout planarized with a low-loss polymer. An extended top metallization keeps waveguide losses low while improving dispersion, thermal and RF properties, as it enables to decouple the design of THz and microwave cavities. Free-running on-chip quantum cascade laser combs spanning 800 GHz, harmonic states with over 1.1 THz bandwidth and RF-injected broadband incoherent states spanning over nearly 1.6 THz are observed using a homogeneous quantum-cascade active core. With a strong external RF drive, actively mode-locked pulses as short as 4.4 ps can be produced, as measured by SWIFTS. We demonstrate as well passive waveguides with low insertion loss, enabling the tuning of the laser cavity boundary conditions and the co-integration of active and passive elements on the same THz photonic chip.

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Section: Introductionmentioning

confidence: 99%

Planarized THz quantum cascade lasers for broadband coherent photonics

et al. 2022

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“…To gain further insights into the process of comb formation in ring QCLs, we conducted extensive numerical simulations of our structure. Similar simulations 32 have previously been undertaken in both mid-IR [33][34][35] and THz QCL 14,22 studies to enhance our comprehension of the underlying dynamics of QCL systems. In this particular investigation, we utilized a master equation formalism previously derived from a two-level Maxwell-Bloch formalism 15,36,37 .…”

Section: Theory and Discussionmentioning

confidence: 85%

“…Their generation hinges on a delicate balance between dispersion, Kerr nonlinearity, parametric gain, and cavity loss 18,21 . Recent experimental demonstrations have successfully established THz QCL ring frequency combs employing both defect-containing 14 and defect-free cavities 22 . In defectincorporated cavities, the presence of a reflection point within the defect leads to the persistence of spatial hole burning (SHB).…”

Section: Introductionmentioning

confidence: 99%

Exploring frequency comb generation in optically injected ring quantum cascade lasers

Khan,

Xiao,

Addamane

et al. 2024

Nonlinear Frequency Generation and Conversion: Materials and Devices XXIII

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Quantum cascade lasers (QCLs) have immense potential for generating chip-scale frequency combs in the mid-infrared and terahertz spectral regions. In this work, we demonstrate the formation of frequency combs within ring terahertz QCLs using optical injection from a distributed feedback (DFB) laser. By carefully selecting a DFB design frequency that aligns with the ring cavity modes (around 3.3 THz) and employing a bus waveguide for light injection, we show that combs can be selectively formed and controlled within the ring cavity. Numerical modeling suggests that the observed comb formation is frequency-modulated in nature, with the optical injection acting as a trigger. Furthermore, we demonstrate the ring cavity's ability to function as a filter, a feature that could hold significant value for terahertz photonic integrated circuits. Our findings highlight the promise of waveguide couplers as a robust approach for injecting and extracting radiation from ring terahertz comb and offer exciting possibilities for generation of new comb states in the terahertz domain, including frequency-modulated waves, solitons, and more.

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“…Recent important milestones in THz QCL development include advances in high-temperature narrowband operation, [6][7][8] comb formation in ring cavities, [9] spontaneous pulses from solitons, [10] heterogeneous integration on silicon substrates, [11] operation as fast detectors, [12,13] and the development of a planarized waveguide platform with improved dispersion, radio frequency (RF) and thermal properties. [14] For use in spectroscopy, combs with flat intensity spectra are often desired, as this relaxes the conditions on the required signal-to-noise ratio (or integration time) for measuring all the spectral components.…”

Section: Introductionmentioning

confidence: 99%

“…Recent important milestones in THz QCL development include advances in high‐temperature narrowband operation, [ 6–8 ] comb formation in ring cavities, [ 9 ] spontaneous pulses from solitons, [ 10 ] heterogeneous integration on silicon substrates, [ 11 ] operation as fast detectors, [ 12,13 ] and the development of a planarized waveguide platform with improved dispersion, radio frequency (RF) and thermal properties. [ 14 ]…”

Section: Introductionmentioning

confidence: 99%

Frequency‐Modulated Combs via Field‐Enhancing Tapered Waveguides

Senica,

Dikopoltsev,

Forrer

et al. 2023

Laser & Photonics Reviews

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Frequency‐modulated (FM) combs feature flat intensity spectra with a linear frequency chirp, useful for metrology and sensing applications. Generating FM combs in semiconductor lasers generally requires a fast saturable gain, usually limited by the intrinsic gain medium properties. Here, it is shown how a spatial modulation of the laser gain medium can enhance the gain saturation dynamics and nonlinearities to generate self‐starting FM combs. This is demonstrated with tapered planarized terahertz (THz) quantum cascade lasers (QCLs). While simple ridge THz QCLs typically generate combs presenting a mixture of amplitude and frequency modulation, the on‐chip field enhancement resulting from extreme spatial confinement leads to an ultrafast saturable gain regime, generating a pure FM comb with a flatter intensity spectrum and a clear linear frequency chirp. The observed linear frequency chirp is reproduced using a spatially inhomogeneous mean‐field theory model, which confirms the crucial role of field enhancement. In addition, the modified spatial temperature distribution within the waveguide results in an improved high‐temperature comb operation, up to a heat sink temperature of 115 K, with comb bandwidths of 600 GHz at 90 K. The spatial inhomogeneity leads as well to very intense radio frequency (RF) beatnotes up to ‐30 dBm and facilitates dynamic switching between various harmonic states in the same device.

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Silicon integrated terahertz quantum cascade ring laser frequency comb

Cited by 12 publications

References 28 publications

Planarized THz quantum cascade lasers for broadband coherent photonics

Planarized THz quantum cascade lasers for broadband coherent photonics

Exploring frequency comb generation in optically injected ring quantum cascade lasers

Frequency‐Modulated Combs via Field‐Enhancing Tapered Waveguides

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