Recently , quantum cascade laser proved to be an extremely interesting platform for frequency combs both in Mid-IR and THz frequency ranges. We will discuss some peculiar aspects of these devices arising from the combination of ultrafast gain, circular cavities and strong RF modulation. Despite the ultrafast nature of the gain medium, by properly engineering dispersion we demonstrate dissipative Kerr solitons both in Mid-IR and THz , with pulse durations of 3.7 ps in the Mid-IR and 10 ps in the THz. Then, by RF modulating a circular cavity, we demonstrate a quantum walk comb in synthetic frequency space. The initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, the state stabilizes in a broad frequency comb, unlocking the full potential of the synthetic frequency lattice. Combs as broad as 100 cm-1 in the Mid-IR with flat top profile are reported.
We demonstrate that resonant phase-modulation of circular Quantum Cascade Laser cavities gives rise to a novel kind of frequency comb, that is remarkably stable, fully tunable and broadband. When the backscattering in such ring cavities is sufficiently low, unidirectional lasing in the free-running device yields single-mode emission. As soon as resonant RF injection is enabled, the spectrum continuously and predictably broadens to span up to 100 cm-1 with nearly-flatted topped spectra. The bandwidth of the resulting comb is fully governed by the depth of the modulation and reaches the fundamental limit dictated by dispersion.
Ultrashort signals are integral for conducting high-resolution measurements. In the mid-infrared, the generation of ultrashort pulses is notoriously difficult to achieve and usually requires large optical setups. In our work we use direct sampling to demonstrate the spontaneous generation of stable ultrashort features in the time-domain signal of a mid-infrared quantum cascade laser frequency comb. The full-width at half-maximum of these features is measured to be ~500 fs, right below the Fourier-limit derived from the corresponding optical spectrum and RF-injection can be used for stabilization and manipulation. Using Maxwell-Bloch equation-based simulations, we can reproduce the generation of such features, including the position in relation to the instantaneous frequency and show their width can be lowered even further below the Fourier limit, thus opening new possibilities for high-resolution measurements based on quantum cascade laser frequency combs.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.