On-chip, self-detected terahertz dual-comb source

Rösch, Markus; Scalari, Giacomo; Villares, Gustavo; Bosco, Lorenzo; Beck, Mattias; Faist, Jérôme

doi:10.1063/1.4948358

Cited by 86 publications

(74 citation statements)

References 36 publications

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“…We employ a self-detection scheme in which the light emitted from QCL 1 is injected, after passing through an optical isolator, into the cavity of QCL 2 ( Figure 3f). The latter acts at the same time as a reference comb and a fast photomixer 23 , from which we can extract electrically the multiheterodyne signal generated by the intracavity beating of the optical fields of the two lasers. The attractive feature of this scheme is that it provides better signal stability as compared to a standard approach utilizing an external fast photodiode.…”

Section: Several Techniques To Generate Optical Frequency Combs (Ofcsmentioning

confidence: 99%

Self-starting harmonic frequency comb generation in a quantum cascade laser

et al. 2017

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Optical frequency combs1,2 establish a rigid phase-coherent link between microwave and optical domains and are emerging as high-precision tools in an increasing number of applications 3 . Frequency combs with large intermodal spacing are employed in the field of microwave photonics for radiofrequency arbitrary waveform synthesis 4,5 and for generation of THz tones of high spectral purity in the future wireless communication networks 6,7 . We demonstrate for the first time self-starting harmonic frequency comb generation with a THz repetition rate in a quantum cascade laser. The large intermodal spacing caused by the suppression of tens of adjacent cavity modes originates from a parametric contribution to the gain due to temporal modulations of the population inversion in the laser 8,9 . The mode spacing of the harmonic comb is shown to be uniform to within 5 × 10 −12 parts of the central frequency using multiheterodyne self-detection. This new harmonic comb state extends the range of applications of quantum cascade laser frequency combs 10-13 . Several techniques to generate optical frequency combs (OFCs) have been demonstratedin the last decades based on different nonlinear mechanisms that fulfill the modelocking condition. Originally, passively modelocked lasers based on saturable absorption and Kerr lensing were used to create short light pulses, and were subsequently shown to also constitute frequency combs. This type of modelocking is an example of amplitude-modulated modelocking, so-named for the temporal behavior of the electric field of the emitted light. However, these techniques usually result in elaborate optical systems. More recently, new routes promising chip-scale comb generators have been investigated based on optically-pumped ultra-high-quality-factor crystalline microresonators 14-16 and on broadband quantum cascade lasers (QCLs) with specially designed multistage active regions 10,17 . In both cases the essential underlying mechanism responsible for the generation of OFCs is cascaded four-wave mixing (FWM) enabled by a third-order χ (3) Kerr nonlinearity. The temporal behavior of these OFCs is not restricted to ultrashort pulses but can represent rather sophisticated waveforms due to a non-trivial relationship among the spectral phases of the comb teeth. In fact, the output of a QCL-based frequency comb resembles that of a frequency-modulated laser with nearly constant output intensity 10,18 .A novel mechanism of OFC generation in QCLs was suggested by the recent discovery of a new laser state 19 , which comprises many modes separated by higher harmonics of the 2 cavity free spectral range (FSR) (Figure 1a). This spectrum radically differs from that of fundamentally modelocked QCL combs where adjacent cavity modes are populated ( Figure 1b THz repetition rates in other semiconductor lasers 20 . Rather, the modes are locked passively due to the behavior of the QCL gain medium itself.In this work we employed two Fabry-Perot (FP) QCLs fabricated from the same growth process with 6 mm-long cavit...

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Section: Several Techniques To Generate Optical Frequency Combs (Ofcsmentioning

confidence: 99%

Self-starting harmonic frequency comb generation in a quantum cascade laser

et al. 2017

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“…For a strongly saturated absorber only the leading edge of the pulse experiences absorption which introduces an effective pulse delay (Fig. 4.13(a)) [43]. For our laser the incident pulse fluence on the saturable absorber is more then 10-times larger than the saturation fluence of the absorber.…”

Section: Noise Correlation Studymentioning

confidence: 82%

“…The estimated pulse delay is in the order of 10 fs for a pulse duration of around 13 ps (Eq. (9) in [43]). This delay is not the same for both pulse trains, because it depends on the energy in each pulse and of course also on the saturable absorber.…”

Section: Noise Correlation Studymentioning

confidence: 97%

“…Noise analysis of dual-comb modelocked lasers common for both beams. We wanted to explore the most likely sources for these decoupled noise such as time delay on the saturable absorber [43] and pump laser noise.…”

Section: Phase Noise Of the Dual-comb Mixselmentioning

confidence: 99%

“…Despite their current drawbacks and limitations QCLs are interesting sources for dual-comb spectroscopy since they cover wavelengths in the range of 7-10 µm [42] and with cryogenic cooling also 2-5 THz [43] with relatively high average output power. These spectral domains are interesting for spectroscopy and challenging to reach with other laser sources.…”

Section: Usually In a Qcl Nearly 70% Of The Light Is Coupled Out Thromentioning

confidence: 99%

See 2 more Smart Citations

Dual-comb modelocked lasers

et al. 2015

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Broadband Terahertz Quantum Cascade Laser Dual‐Comb Sources under Off‐Resonant Microwave Injection

Liao

Zhou

et al. 2022

Advanced Photonics Research

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Broadband dual‐comb spectroscopy has attracted increasing interests due to its unique advantages in high spectral resolution, fast detection, and so on. Although the dual‐comb technique is relatively mature in the infrared wavelengths, it is, currently, not commercially capable of practical applications in the terahertz regime due to the lack of high‐performance broadband terahertz dual‐comb sources. In the terahertz frequency range, the electrically pumped quantum cascade laser (QCL) is a suitable candidate for the dual‐comb operation. Although the resonant microwave injection locking is widely used to broaden the emission spectra of terahertz QCLs, it is challenging to be employed to obtain broadband dual‐comb sources that can fully exploit the laser gain bandwidth due to the large phase noise induced by the resonant injection and nonideal microwave circuits. Herein, an off‐resonant microwave injection to significantly broaden the dual‐comb bandwidth of a terahertz QCL dual‐comb source is used. The measured optical dual‐comb bandwidth is broadened from 147 GHz in free running to >450 GHz under the off‐resonant injection. By performing a numerical analysis based on a rate equation model, the broadband dual‐comb operation under the off‐resonant microwave injection can result from a wider lasing bandwidth and a higher degree of phase matching.

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On-chip, self-detected terahertz dual-comb source

Cited by 86 publications

References 36 publications

Self-starting harmonic frequency comb generation in a quantum cascade laser

Self-starting harmonic frequency comb generation in a quantum cascade laser

Dual-comb modelocked lasers

Broadband Terahertz Quantum Cascade Laser Dual‐Comb Sources under Off‐Resonant Microwave Injection

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