arXiv subjects

Ina Heckelmann

Publications and source records attributed to Ina Heckelmann.

9 recordsLinked to original sources

arXiv2025

Free-Running Ring Quantum Cascade Laser with 50 kHz Linewidth

We report on the noise characterization of a free-running ring quantum cascade laser resonator emitting a single frequency mode around 7.7 $\mu$m. Using a gas cell filled with N$_2$O as a frequency-to-voltage discriminator, we measured the frequency noise power spectral density of the laser from which we extracted its linewidth. The results show a full width at half maximum close to 50 kHz at 1 s integration time, which represents at least a sixfold improvement compared to state-of-the-art quantum cascade lasers operating in a spectral region above 7 $\mu$m. We also demonstrate that such lasers can be efficiently used for frequency modulation spectroscopy, which opens up new possibilities for high resolution metrology and spectroscopic applications in the mid-infrared.

physics.optics↗

arXiv2025

Fast and compact time-resolved spectroscopy enabled by Quantum Walk Combs

Optical frequency combs paved the way for fast and compact multi-component optical chemical analysis due to their broadband spectra. Dual-comb spectrometers embody this technology, but their design requires a pair of matched combs, adding complexity to the system. In this study, we propose and implement a scheme for a rapid, compact spectroscopic analyser that operates without moving components, leveraging the tunability and speed of a single quantum walk comb laser. Previously, these combs have been shown to deliver stable, tunable and broadband lasing. Here, a single quantum cascade laser-based comb emitting within the significant molecular fingerprint region of the mid-infrared spectrum was employed in a non-interferometric setup for targeted and non-targeted analysis of various organic solvent vapours. With a time resolution as small as 10 microseconds and a high dynamic range reaching three orders of magnitude in concentration, this approach is suitable for the real-time analysis of chemical kinetics.

physics.optics↗

arXiv2025

Time-resolved spectroscopy of noise-driven collective states of light

We study a collective liquid state of light in a fast-gain laser. Controlled temporal noise on the cavity modulation creates a fluctuating linear potential along the synthetic frequency lattice of the cavity modes. We identify three regimes of lattice occupation as noise increases: an extended distribution, a Gaussian envelope, and exponential localization. Time-resolved spectroscopy on single realizations of noise reveals distinct dynamics in the latter two: transport persists in the Gaussian regime, modulated by the fluctuating potential, but is fully suppressed at all times in the localized regime. Averaging over many noise realizations shows that noise reduces the transport speed and confirms ergodicity of the system.

physics.optics↗

arXiv2025

Spectral shaping of fast-gain frequency combs through phases in synthetic dimensions

Optical frequency comb devices have unlocked new capabilities in telecommunications, sensing, and metrology. Yet, precise in situ control of the comb spectral envelope remains extremely challenging. By introducing mode coupling with non-trivial phases, we demonstrate a spectral shaping technique that enables continuous tuning of a dominant spectral lobe across the full bandwidth of a semiconductor laser frequency comb. We achieve this jointly leveraging the engineered geometry of the synthetic lattice formed by the cavity modes of the laser and the coherent dynamics enabled by its fast-gain recovery. We use dual-tone modulation of the cavity at its repetition rate and twice this frequency with a controlled relative phase to couple the comb modes into a triangular lattice. The relative phase between the two tones defines a lattice phase that breaks time-reversal symmetry and steers the lattice dynamics through the fast gain. With this approach, we experimentally control the spectral envelope of the comb such that a targeted region contains more than twice the intensity expected from a uniform distribution, demonstrating tunable spectral selectivity. This capability, achieved directly at the light generation stage in a fast-gain device, opens routes for efficient programmable waveform engineering with potential applications in ranging, data transmission, and sensing.

physics.optics↗

arXiv2024

Quench dynamics of Wannier-Stark states in an active synthetic photonic lattice

Photonic emulators have facilitated the investigation of numerous solid-state phenomena and have contributed to the development of optical devices inspired by quantum mechanics. Although current photonic emulators are constrained to bosonic behavior with local interactions, the utilization of active synthetic lattices holds promise for surpassing these limitations. In this study, we propose employing the modulated ring fast-gain laser as a foundation for emulating quench dynamics within a synthetic lattice that conforms to equal density filling of its reciprocal space. To illustrate the effectiveness of this emulation platform, we subject a dispersed Wannier-Stark ladder to quenching and directly observe oscillations, enabled by the fast-gain, along with their coherent stabilization to a single Wannier stark state. These coherent dynamics stem directly from our lasers liquid state of light, a characteristic resulting from fast-gain and explained by the rapid decay of fluctuations occurring on the system's shortest timescale. Additionally, by adequately biasing the lattice through detuning the modulation from the cavity resonance, this process supports oscillatory dynamics within the synthetic space.

physics.optics↗

arXiv2023

Quantum Walk Comb in a Fast Gain Laser

Synthetic lattices in photonics enable the exploration of light states in new dimensions, transcending phenomena common only to physical space. We propose and demonstrate a Quantum Walk Laser in synthetic frequency space formed by externally modulating a ring-shaped semiconductor laser with ultrafast recovery times. In this device, the initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, thanks to the fast-gain nonlinearity of our quantum cascade laser active material, the state stabilizes in a broad frequency comb, unlocking the full potential of the lattice. This device produces a low-noise, nearly-flat broadband comb (reaching 100 cm$^{-1}$ bandwidth), well predicted by our models. The proposed Quantum Walk Laser offers a promising platform to generate broadband, tunable and stable frequency combs.

physics.optics↗

arXiv2023

Backscattering-Induced Dissipative Solitons in Ring Quantum Cascade Lasers

Ring quantum cascade lasers have recently gained considerable attention, showing ultrastable frequency comb and soliton operation, thus opening a way to integrated spectrometers in the midinfrared and terahertz fingerprint regions. Thanks to a self-consistent Maxwell-Bloch model, we demonstrate, in excellent agreement with the experimental data, that a small but finite coupling between the counterpropagating waves arising from distributed backscattering is essential to stabilize the soliton solution.

physics.optics↗

arXiv2022

Supramolecular self-assembly as a tool to preserve electronic purity of perylene diimide chromophores

Small molecule organic semiconductors hold great promise for efficient, printable, and flexible optoelectronic applications like solar cells and displays. However, strong excited-state quenching due to uncontrolled aggregation currently limits their performance and employability in devices. Here, we report on the self-assembly of a supramolecular pseudo-cube formed from six modified tetradentate perylene diimides (PDIs). The rigid, shape-persistent cage sets the distance and orientation of the PDI chromophores and suppresses intramolecular rotations and vibrations, leading to non-aggregated, monomer-like electronic properties in solution as well as in the solid state, in contrast to the fast fluorescence quenching in the free ligand. The stabilized excited state and electronic purity of the cage enable the observation of delayed fluorescence due to a bright excited multimer state, which acts as an excited state reservoir, due to a rare case of benign inter-chromophore interactions in the cage. Our results suggest that not only the photophysical properties of the subcomponents but the geometric structure is crucial for the overall optoelectronic properties of supramolecular systems. We show that self-assembly provides a powerful tool for retaining and controlling the electronic properties of well-studied chromophores, providing a route to bring molecular electronics applications in reach.

physics.chem-ph↗

arXiv2022

Universal mechanism of luminescence enhancement in doped perovskite nanocrystals from symmetry analysis

Metal-halide perovskite nanocrystals have demonstrated excellent optoelectronic properties for light-emitting applications. Isovalent doping with various metals (M2+) can be used to tailor and enhance their light emission. Although crucial to maximize performance, an understanding of the universal working mechanism for such doping is still missing. Here, we directly compare the optical properties of nanocrystals containing the most commonly employed dopants, fabricated under identical synthesis conditions. We show for the first time unambiguously and supported by first principles calculations and molecular orbital theory that element-unspecific symmetry-breaking rather than element-specific electronic effects dominate these properties under device-relevant conditions. The impact of most dopants on the perovskite electronic structure is predominantly based on local lattice periodicity breaking and resulting charge carrier localization, leading to enhanced radiative recombination, while dopant-specific hybridization effects play a secondary role. Our results suggest specific guidelines for selecting a dopant to maximize the performance of perovskite emitters in the desired optoelectronic devices.

cond-mat.mtrl-sci↗