Mr. Tudor Olariu Profile

Tudor Olariu

at ETH Zurich

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Author

Publications (5)

Proceedings Article | 3 June 2022 Presentation

Planarized tapered waveguides for THz quantum cascade laser frequency combs

Urban Senica, Tudor Olariu, Andres Forrer, Paolo Micheletti, Mattias Beck, Jérôme Faist, Giacomo Scalari

Proceedings Volume PC12134, PC1213406 (2022) https://doi.org/10.1117/12.2626797

KEYWORDS: Waveguides, Terahertz radiation, Frequency combs, Quantum cascade lasers, Temperature metrology, Wave propagation, Standards development, Signal attenuation, Scattering, Polymers

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Terahertz (THz) quantum cascade lasers (QCLs) based on double metal waveguides are compact sources of broadband THz radiation, which can also operate as frequency combs. We present a planarized double metal waveguide THz QCL platform, where the active region is embedded in a low-loss BCB polymer and covered by an extended top metallization. The latter enables placing bonding wires on the sides above the BCB-covered area, hindering the formation of any defects on the active region and enables the fabrication of waveguides with narrow widths below the bonding wire size. This can then be employed as a fundamental mode selection mechanism for comb operation without any side absorbers, and also features improved heat dissipation properties in continuous wave operation. The extended top metallization also enhances the RF properties of the device, as it encompasses a metallic cavity with the global ground plane. Experimentally, we present results on two different device geometries. First is a simple ridge waveguide with a width of 40 μm, narrow enough to act as a mode selection filter. Free-running frequency comb states with bandwidths above 600 GHz and single beatnotes up to -60 dBm are measured. With a strong external RF signal, close to the natural repetition frequency, we can broaden the emission to over 1.4 THz. The second type of device is a tapered waveguide, where the narrow sections act as a transversal mode filter, while the wider ones have lower waveguide losses and provide more gain. Due to a field-enhancement effect in the narrow sections, there is a significant enhancement in the four wave mixing, a third order nonlinear process responsible for comb formation. Free-running devices produce beatnotes close to -30 dBm, three orders of magnitude higher than for ridge devices. Improved comb performance is maintained also for high operating temperatures. A comb bandwidth above 200 GHz and a single beatnote above -60 dBm are measured at 115 K, very close to the maximum lasing temperature of 118 K. Beyond the improved laser and comb performance, the planarized waveguide platform also enables a relatively straightforward co-integration of active and passive elements.

Proceedings Article | 5 March 2022 Presentation

Planarized waveguides for high-performance THz quantum cascade laser frequency combs

Urban Senica, Tudor Olariu, Andres Forrer, Mattias Beck, Jérôme Faist, Giacomo Scalari

Proceedings Volume PC12009, PC120090E (2022) https://doi.org/10.1117/12.2609363

KEYWORDS: Waveguides, Terahertz radiation, Frequency combs, Quantum cascade lasers, Metals, Dispersion, Continuous wave operation, Temperature metrology, Reflectors, Polymers

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Proceedings Article | 5 March 2021 Presentation

Systematic search for single mode THz QCL and post-processing frequency tuning

Tudor Olariu, Mattias Beck, Giacomo Scalari, Jérôme Faist

Proceedings Volume 11685, 116851B (2021) https://doi.org/10.1117/12.2578573

KEYWORDS: Quantum cascade lasers, Terahertz radiation, Antennas, Refractive index, Reflectors, Polymers, Waveguide lasers, Silica, Semiconductors, Reflectivity

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Proceedings Article | 30 March 2020 Presentation

RF control of THz quantum cascade laser frequency combs (Conference Presentation)

Giacomo Scalari, Andres Forrer, David Stark, Urban Senica, Tudor Olariu, Philipp Täschler, Mattias Beck, Jerome Faist

Proceedings Volume 11348, 113480C (2020) https://doi.org/10.1117/12.2556090

KEYWORDS: Terahertz radiation, Quantum cascade lasers, Frequency combs, Mid-IR, Photon transport, Microwave radiation, Feedback control, Time metrology, Physics

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Proceedings Article | 8 March 2019 Presentation

Wide-bandwidth low-threshold THz frequency combs (Conference Presentation)

Giacomo Scalari, Tudor Olariu, Andres Forrer, David Stark, Mattias Beck, Jerome Faist

Proceedings Volume 10926, 109262J (2019) https://doi.org/10.1117/12.2507299

KEYWORDS: Terahertz radiation, Frequency combs, Mid-IR, Quantum cascade lasers, Time metrology, Bolometers, Time resolved spectroscopy, Spectroscopy, Actuators

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