Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers

Wójcik, Aleksander K.; Malara, P.; Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico; Belyanin, Alexey

doi:10.1063/1.4838275

Cited by 45 publications

(44 citation statements)

References 15 publications

(14 reference statements)

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“…One approach is to numerically solve the full spatiotemporal Maxwell-Bloch equations [53,54]. To obtain analytical results, we follow a common approximation and decouple the spatial and temporal dependencies [55], writing the field as…”

Section: A General Frameworkmentioning

confidence: 99%

Single-mode instability in standing-wave lasers: The quantum cascade laser as a self-pumped parametric oscillator

et al. 2016

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We report the observation of a clear single-mode instability threshold in continuous-wave Fabry-Perot quantum cascade lasers (QCLs). The instability is characterized by the appearance of sidebands separated by tens of free spectral ranges (FSR) from the first lasing mode, at a pump current not much higher than the lasing threshold. As the current is increased, higher-order sidebands appear that preserve the initial spacing, and the spectra are suggestive of harmonically phase-locked waveforms. We present a theory of the instability that applies to all homogeneously broadened standing-wave lasers. The low instability threshold and the large sideband spacing can be explained by the combination of an unclamped, incoherent Lorentzian gain due to the population grating, and a coherent parametric gain caused by temporal population pulsations that changes the spectral gain line shape. The parametric term suppresses the gain of sidebands whose separation is much smaller than the reciprocal gain recovery time, while enhancing the gain of more distant sidebands. The large gain recovery frequency of the QCL compared to the FSR is essential to observe this parametric effect, which is responsible for the multiple-FSR sideband separation. We predict that by tuning the strength of the incoherent gain contribution, for example by engineering the modal overlap factors and the carrier diffusion, both amplitude-modulated (AM) or frequency-modulated emission can be achieved from QCLs. We provide initial evidence of an AM waveform emitted by a QCL with highly asymmetric facet reflectivities, thereby opening a promising route to ultrashort pulse generation in the mid-infrared. Together, the experiments and theory clarify a deep connection between parametric oscillation in optically pumped microresonators and the single-mode instability of lasers, tying together literature from the last 60 years.

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Section: A General Frameworkmentioning

confidence: 99%

Single-mode instability in standing-wave lasers: The quantum cascade laser as a self-pumped parametric oscillator

et al. 2016

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“…Fundamental mode-locking of QCLs has led to intense discussion in the literature [32][33][34] . Mode-locked operation of QCLs is difficult to achieve but have been demonstrated at cryogenic temperatures in the mid-infrared in a design where the upper-state lifetime was significantly increased using a highly diagonal laser transition 32 and in the terahertz where that lifetime is naturally much longer 35 .…”

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confidence: 99%

Dual-comb spectroscopy based on quantum-cascade-laser frequency combs

et al. 2014

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Dual-comb spectroscopy performed in the mid-infrared-where molecules have their strongest rotovibrational absorption lines-offers the promise of high spectral resolution broadband spectroscopy with very short acquisition times (ms) and no moving parts. Recently, we demonstrated frequency comb operation of a quantum-cascade-laser. We now use that device in a compact, dual-comb spectrometer. The noise properties of the heterodyne beat are close to the shot noise limit. Broadband (15 cm À 1 ) high-resolution (80 MHz) absorption spectroscopy of both a GaAs etalon and water vapour is demonstrated, showing the potential of quantum-cascade-laser frequency combs as the basis for a compact, all solid-state, broadband chemical sensor.

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“…This arrangement simplifies the mode selection because it minimizes the spatial hole burning effect, and it also allows the use of modulation frequencies low enough to enable complete switching of the laser on and off. This geometry has been analyzed both theoretically [51] and experimentally [52,53].…”

Section: Mode-locking Of Qclsmentioning

confidence: 99%

Quantum Cascade Laser Frequency Combs

Faist

Villares²,

Scalari³

et al. 2016

Nanophotonics

193

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It was recently demonstrated that broadband quantum cascade lasers can operate as frequency combs. As such, they operate under direct electrical pumping at both mid-infrared and THz frequencies, making them very attractive for dual-comb spectroscopy. Performance levels are continuously improving, with average powers over 100 mW and frequency coverage of 100 cm −1 in the midinfrared region. In the THz range, 10 mW of average power and 600 GHz of frequency coverage are reported. As a result of the very short upper state lifetime of the gain medium, the mode proliferation in these sources arises from four-wave mixing rather than saturable absorption. As a result, their optical output is characterized by the tendency of small intensity modulation of the output power, and the relative phases of the modes to be similar to the ones of a frequency modulated laser. Recent results include the proof of comb operation down to a metrological level, the observation of a Schawlow-Townes broadened linewidth, as well as the first dual-comb spectroscopy measurements. The capability of the structure to integrate monothically nonlinear optical elements as well as to operate as a detector shows great promise for future chip integration of dual-comb systems.

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Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers

Cited by 45 publications

References 15 publications

Single-mode instability in standing-wave lasers: The quantum cascade laser as a self-pumped parametric oscillator

Single-mode instability in standing-wave lasers: The quantum cascade laser as a self-pumped parametric oscillator

Dual-comb spectroscopy based on quantum-cascade-laser frequency combs

Quantum Cascade Laser Frequency Combs

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