RF Injection of THz QCL Combs at 80 K Emitting over 700 GHz Spectral Bandwidth

Forrer, Andres; Bosco, Lorenzo; Beck, Mattias; Faist, Jérôme; Scalari, Giacomo

doi:10.3390/photonics7010009

Cited by 15 publications

(16 citation statements)

References 36 publications

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“…The active a) Electronic mail: aforrer@phys.ethz.ch b) Electronic mail: scalari@phys.ethz.ch region itself was previously studied in the fundamental frequency comb regime including injection-locking in Refs. 18,19 . The active region is embedded in a double metal gold-gold (Au-Au) 18 resp.…”

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confidence: 99%

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Self-starting harmonic comb emission in THz quantum cascade lasers

Forrer

Wang

Beck

et al. 2021

Applied Physics Letters

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Harmonic comb state has proven to be emerging in quantum cascade lasers and promoted by an interplay between parametric gain and spatial hole burning. We report here on robust, pure, self-starting harmonic mode locking in Copper-based double-metal THz quantum cascade lasers. Different harmonic orders can be excited in the same laser cavity depending on the pumping condition and stable harmonic combs spanning more than 600 GHz bandwidth at 80 K are reported. Such devices can be RF injected and the free running coherence is assessed by means of self-mixing technique performed at 50 GHz. A theoretical model based on Maxwell-Bloch equations including an asymmetry in the gain profile is used to interpret the data.

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confidence: 99%

“…The active region is embedded in a double metal gold-gold (Au-Au) 18 resp. low loss copper-copper (Cu-Cu) 19 waveguides featuring lossy setbacks in the top cladding 20 for transverse mode control. As was mentioned in Ref.…”

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confidence: 99%

Self-starting harmonic comb emission in THz quantum cascade lasers

Forrer

Wang

Beck

et al. 2021

Applied Physics Letters

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“…In recent years, the continuous maturity of quantum cascade lasers (QCLs) [5][6][7][8] from mid-infrared to the THz spectral range provides an opportunity for advancing the development of OFCs by a mechanism of intracavity nonlinear four-wave mixing and injection locking [9]. However, emergence of more promising THz QCL OFCs toward yielding more stable comb operating, wider current dynamic range and spectral range [10][11][12], higher output power [13] and narrower beam divergence is still expected for further application.…”

Section: Introductionmentioning

confidence: 99%

THz Quantum Cascade Laser Operating Frequency Comb Over Near-full-current Dynamic Range

Liu

Zhuo

et al. 2021

Preprint

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We report a terahertz quantum cascade laser frequency comb (THz QCL FC) with low threshold current density, high power, and wide current dynamic range. The active region design with the semi-insulated surface plasma waveguide is beneficial to optimize the gain dispersion value and temperature stability. At 10K, the comb with 3-mm-long and 150-µm-wide is capable of emitting 22mW with the threshold current density Jth = 64.4 A·cm−2. The total spectral emission is of about 300 GHz centered around 4.6 THz. Without any extra dispersion compensation measures, the intermode beatnote map reveals stable frequency comb operating within a current dynamic range more than 97% and the narrowest beatnote linewidth is 7.2 kHz. The stable FC operation of a free-running THz QCL makes our device an ideal source for further development of dual-comb spectroscopy.

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“…Likewise, external radio-frequency (RF) injection can be used as a means for injection-locking and thus manipulation of these internal oscillations. [24][25][26] In earlier experiments, stabilization [27,28] active mode-locking [29][30][31] and tuning of the free spectral range of the device [32] have been demonstrated. The trade-off between RF-compatibility and thermal efficiency has been recently addressed by Kapsalidis et al.…”

Section: Introductionmentioning

confidence: 99%

Controlling Quantum Cascade Laser Optical Frequency Combs through Microwave Injection

Kapsalidis¹,

Mathieu²,

Singleton³

et al. 2021

Preprint

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In this work, control over the precise state emitted by quantum cascade laser frequency combs through strong radio-frequency current modulation close to their repetition frequency is demonstrated. In particular, broadening of the spectrum from about 20 cm −1 to 60cm −1 can be achieved throughout most of the current dynamical range while preserving the coherence, as measured by shifted wave interference Fourier transform spectroscopy (SWIFTS). The required modulation frequency to achieve this broadening is redshifted compared to the free-running beatnote frequency at increasing modulation powers starting from 25 dBm, whereas the range where it occurs narrows. Outside of this maximum-bandwidth range, the spectral bandwidth of the laser output is gradually reduced and the new center frequency is red-or blue-shifted, directly dependent on the detuning of the modulation frequency. By switching between two modulation frequencies detuned symmetrically with respect to the free-running beatnote, we can generate two multiplexed spectral regions with negligible overlap from the same device at rates of at least 20 kHz. In the time-domain we show with both SWIFTS and interferometric autocorrelation (IAC) measurements a transition from quasi-continuous output to pulsed (τp ≈ 55 ps) output by ramping up the injection power to 35 dBm.

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RF Injection of THz QCL Combs at 80 K Emitting over 700 GHz Spectral Bandwidth

Cited by 15 publications

References 36 publications

Self-starting harmonic comb emission in THz quantum cascade lasers

Self-starting harmonic comb emission in THz quantum cascade lasers

THz Quantum Cascade Laser Operating Frequency Comb Over Near-full-current Dynamic Range

Controlling Quantum Cascade Laser Optical Frequency Combs through Microwave Injection

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