Filippos Kapsalidis


Last Name

Kapsalidis

First Name

Filippos

ORCID

0000-0001-5927-0038

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2016 - 201972020 - 202551
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Publications 1 - 10 of 58
  • Coherent Broadening and Tuning of QCL Frequency Combs via RF-Injection
    Item type: Other Conference Item
    Schneider, Barbara; Kapsalidis, Filippos; Singleton, Matthew; et al. (2021)
    2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)
    Quantum cascade laser (QCL) optical frequency combs [1] , [2] are emerging as promising sources in mid-infrared spectroscopy due to their ability to act as coherent broadband sources at room temperature with equidistant phase-locked modes. Their short sub-picosecond upper-state lifetime enables high modulation speeds of the device in the order of tens of gigahertz [3] . Since the devices are electrically driven, the intermode beating, which is in the RF-domain, can be read out electronically as current-modulations. Through external RF-modulation of the driving current, the comb-modes can be injection-locked for stabilization as well as enhancement of the four-wave-mixing process which is one of the main driving mechanisms of comb formation in QCLs [5] .
  • Mid-infrared femtosecond pulses from a quantum cascade laser
    Item type: Conference Paper
    Täschler, Philipp; Bertrand, Mathieu; Schneider, Barbara; et al. (2022)
    Proceedings of SPIE ~ Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXII
    In recent years, quantum cascade lasers have matured to become compact, powerful sources of coherent mid infrared light. Yet, the ultrafast carrier dynamics in these sources has so far restricted the formation of high intensity ultrashort pulses. In this work, we demonstrate the formation of ~ 630 fs QCL pulses with a peak power of ~ 4.3 W. We break the picosecond barrier in an approach similar to chirped pulse amplification, where we externally recompress the maximally chirped output of a quantum cascade laser frequency comb. Ultrashort pulse formation is confirmed with a novel asynchronous optical sampling technique. These results emphasise the potential of quantum cascade lasers also as sources for non-linear experiments in the mid-infrared.
  • Ridge-width dependence of the dispersion and performance of mid-infrared quantum cascade laser frequency combs
    Item type: Conference Paper
    Wang, Ruijun; Kapsalidis, Filippos; Shahmohammadi, Mehran; et al. (2020)
    OSA Technical Digest ~ Conference on Lasers and Electro-Optics
    We investigate the effects of ridge width on the characteristics of quantum cascade laser frequency combs and study how to achieve optimal performance. Very narrow ridges lead to much broader lasing spectra but also result in weaker comb stability.
  • Ultra-low threshold quantum cascade laser
    Item type: Other Conference Item
    Wang, Xhixin; Kapsalidis, Filippos; Wang, Ruijun; et al. (2021)
    OSA Technical Digest ~ Conference on Lasers and Electro-Optics
    We present a quantum cascade laser operating at 4.3 µm wavelength and exhibiting a threshold current of only 9.5 mA while generating a single-mode maximum power of 0.9 mW at-20 °C in continuous-wave operation.
  • Low-Loss RF Cavity for Quantum Cascade Laser Frequency Combs
    Item type: Conference Paper
    Kapsalidis, Filippos; Singleton, Matthew; Beck, Mattias; et al. (2019)
    2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)
  • Linewidth Enhancement Factor of Mid-IR Quantum Cascade Lasers
    Item type: Other Conference Item
    Bertrand, Mathieu; Franckié, Martin; Forrer, Andres; et al. (2021)
    2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)
    Schawlow and Townes theorized that the ratio between the spontaneous emission and stimulated emission in a semiconductor laser defines its linewidth lower limit [1] . However, experiments showed that this intrinsic linewidth is larger, which was later demonstrated to be due to the coupling between the optical gain and the phase noise [2] . The linewidth enhancement factor (LEF) was introduced to quantify this process and as a correction to the linewidth formula in [1] .
  • Noise Correlation Between the Two Degrees of Freedom of a Mid-Infrared Quantum Cascade Laser Frequency Comb
    Item type: Conference Paper
    Shehzad, Atif; Brochard, Pierre; Komagata, Kenichi; et al. (2020)
    OSA Technical Digest ~ Conference on Lasers and Electro-Optics
    We present a detailed frequency noise characterization of a mid-infrared QCL comb with separate investigations of an optical line, the mode spacing and the offset frequency, and show strong anti-correlation between the two free-running comb parameters.
  • Optomechanical control of quantum cascade laser frequency combs
    Item type: Conference Paper
    Burghoff, David; Han, Ningren; Kapsalidis, Filippos; et al. (2019)
    Proceedings of SPIE ~ Novel In-Plane Semiconductor Lasers XVIII
  • All-Mid-Infrared Stabilized Quantum Cascade Laser Frequency Comb with 30-kHz Frequency Stability at 7.7 mu m
    Item type: Conference Paper
    Komagata, Kenichi; Shehzad, Atif; Hamrouni, Marin; et al. (2021)
    2021 Conference on Lasers and Electro-Optics (CLEO)
    High-resolution spectroscopy in the mid-infrared requires stable frequency references. A frequency comb emitted by a quantum cascade laser is locked to a molecular transition, demonstrating 30-kHz frequency stability up to 5000-s integration time.
  • Ultra-low threshold lasing through phase front engineering via a metallic circular aperture
    Item type: Journal Article
    Wang, Zhixin; Kapsalidis, Filippos; Wang, Ruijun; et al. (2022)
    Nature Communications
    Semiconductor lasers with extremely low threshold power require a combination of small volume active region with high-quality-factor cavities. For ridge lasers with highly reflective coatings, an ultra-low threshold demands significantly suppressing the diffraction loss at the facets of the laser. Here, we demonstrate that introducing a subwavelength aperture in the metallic highly reflective coating of a laser can correct the phase front, thereby counter-intuitively enhancing both its modal reflectivity and transmissivity at the same time. Theoretical and experimental results manifest a decreasing in the mirror loss by over 40% and an increasing in the transmissivity by 104. Implementing this method on a small-cavity quantum cascade laser, room-temperature continuous-wave lasing operation at 4.5 μm wavelength with an electrical consumption power of only 143 mW is achieved. Our work suggests possibilities for future portable applications and can be implemented in a broad range of optoelectronic systems.
Publications 1 - 10 of 58