Spectral Shaping of a Superluminescent Diode for Terahertz Cross-Correlation Spectroscopy

Tybussek, Kai-Henning; Kolpatzeck, Kevin; Cherniak, Vladyslav; Engelbrecht, Sebastian; Fischer, Bernd; Balzer, Jan C.

doi:10.3390/app12041772

Cited by 5 publications

(5 citation statements)

References 20 publications

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“…This approach was demonstrated for the first time in 2019 [52]. However, the continuous spectrum is accompanied by a reduction of the dynamic range [53].…”

Section: Compact Systemsmentioning

confidence: 92%

THz Systems Exploiting Photonics and Communications Technologies

et al. 2023

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Terahertz (THz) systems open up the possibility of new applications of electromagnetic waves. Enormous bandwidths up to several terahertz enable the development of powerful spectroscopy systems that can provide insights into the structure and material of objects with micrometer resolution. New high power and compact THz time-domain spectroscopy (TDS) systems will be presented. The wide bandwidth also enables high-resolution imaging under far-field conditions to analyze arbitrary objects from a distance. In addition, a near-field system-on-a-chip imaging system is presented that achieves a resolution of 10 μm. Additionally, the application of terahertz waves presents challenges due to the low transmit power of the sources, high attenuation in free space, and the high noise figures of the receivers. These challenges can be overcome by antennas with high gain. Since -depending on the application -spatial scanning or focusing in a time-varying direction is required, beam steering is an essential component of many THz systems. In terms of communications, terahertz carrier frequencies offer wide bandwidths, enabling correspondingly high data rates of 100 Gbit/s and more. As a result, the frequency bands between 250 GHz and 450 GHz have already been identified and/or allocated for communication services and are being discussed as a component of 6G mobile communications. Concepts and demonstrations for 6G terahertz mobile communications will be presented. The high bandwidth of terahertz waves can also be used for high-accuracy indoor localization.INDEX TERMS THz time-domain spectroscopy, high average power THz systems, THz far-field imaging, THz near-field imaging, THz communication, THz localization, MTT 70th Anniversary Special Issue.

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“…This approach was demonstrated for the first time in 2019 [52]. However, the continuous spectrum is accompanied by a reduction of the dynamic range [53].…”

Section: Compact Systemsmentioning

confidence: 92%

THz Systems Exploiting Photonics and Communications Technologies

et al. 2023

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“…Author year of publication System type Peak dynamic range / dB Bandwidth / THz * M. Tani et al 24 1997 QTDS/CCS 13 0.4 * O. Morikawa et al 25 44 2011 QTDS/CCS 30 1.1 * M. Scheller et al 45 2012 QTDS/CCS 55 0.6 J. C. et al 46 2016 QTDS/CCS 62 0.9 K. Merghem et al 35 2017 a) TDS 45 0.6 R. Kohlhaas et al 28 2017 b) QTDS/CCS 60 1.8 A. Rehn et 30 2018 QTDS/CCS 56 1 J. C. Balzer et al 47 2019 a) TDS 65 0.9 D. Molter et al 32 2019 b) QTDS/CCS 50 1.5 Tonder et al 48 2019 c) TDS 60 1 K. Tybussek et al 49 2019 d) TDS 56 1.4 K. Kolpatzeck et al 36 2020 a) TDS 68 1.6 V. Cherniak et al 50 2020 b) TDS 65 1.1 V. Cherniak et al 37 2021 a) TDS 70 1.22 K. Tybussek et al 33 2022 QTDS/CCS 60 2…”

Section: Signal Processingmentioning

confidence: 99%

“…Recently, the system bandwidth was increased by operating the MMLD with a low duty cycle 30 and with optical feedback into the laser 31 , respectively. A variation of the THz-CCS concept using a superluminescent diode (SLD) as a mode-less semiconductor light source was first demonstrated by Molter et al 32 and later studied in greater detail with spectral shaping by Tybussek et al 33 . The mode-less nature of the SLD generates a continuous terahertz spectrum, so that the system's frequency resolution is only limited by the length of the optical delay unit (ODU).…”

Section: Introductionmentioning

confidence: 99%

Laser Diode based THz-TDS System with 133 dB peak Signal-to-Noise Ratio

Cherniak

Kubiczek

Kolpatzeck

et al. 2023

Preprint

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Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful and versatile tool in various scientific fields. These include – among others – imaging, material characterization, and layer thickness measurements. While THz-TDS has achieved significant success in research environments, the high cost and bulky nature of most systems have hindered widespread commercialization of this technology. Two primary factors contributing to the size and cost of these systems are the laser and the optical delay unit (ODU). Consequently, our group has focused on developing THz-TDS systems based on compact monolithic mode-locked laser diodes (MLLDs). The ultra-high repetition rate (UHRR) of the MLLD has the added benefit that it allows us to utilize shorter ODUs, thereby reducing the overall cost and size of our systems. However, achieving the necessary precision in the ODU to acquire accurate terahertz time-domain signals remains a crucial aspect.To address this issue, we have developed and enhanced an interferometric extension for UHRR-THz-TDS systems. This extension is inexpensive, compact, and easy to incorporate. In this article, we present the system setup, the extension itself, and the algorithmic procedure for reconstructing the delay axis based on the interferometric reference signal. We evaluate a dataset comprising 10,000 signal traces and report a standard deviation of the measured terahertz phase at 1.6 THz as low as 3 mrad. Additionally, we demonstrate a remaining peak-to-peak jitter of only 20 fs and a record-high peak dynamic range of 133 dB after averaging. The method presented in this paper allows for simplified THz-TDS system builds, reducing bulk and cost. As a result, it further facilitates the transition of terahertz technologies from laboratory to field applications.

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“…Recently, the system bandwidth was increased by operating the MMLD with a low duty cycle 30 and with optical feedback into the laser 31 , respectively. A variation of the THz-CCS concept using a superluminescent diode (SLD) as a mode-less semiconductor light source was first demonstrated by Molter et al 32 and later studied in greater detail with spectral shaping by Tybussek et al 33 . The mode-less nature of the SLD generates a continuous terahertz spectrum, so that the system’s frequency resolution is only limited by the length of the optical delay unit (ODU).…”

Section: Introductionmentioning

confidence: 99%

“…Although the bandwidth of THz-CCS systems has quite frequently been shown to exceed 1 THz, with one work going up to 2 THz 33 , their dynamic range has been lacking compared to conventional THz-TDS systems. The highest demonstrated values range around 60 dB.…”

Section: Introductionmentioning

confidence: 99%

Laser diode based THz-TDS system with 133 dB peak signal-to-noise ratio at 100 GHz

Cherniak,

Kubiczek,

Kolpatzeck

et al. 2023

Sci Rep

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Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful and versatile tool in various scientific fields. These include—among others—imaging, material characterization, and layer thickness measurements. While THz-TDS has achieved significant success in research environments, the high cost and bulky nature of most systems have hindered widespread commercialization of this technology. Two primary factors contributing to the size and cost of these systems are the laser and the optical delay unit (ODU). Consequently, our group has focused on developing THz-TDS systems based on compact monolithic mode-locked laser diodes (MLLDs). The ultra-high repetition rate (UHRR) of the MLLD has the added benefit that it allows us to utilize shorter ODUs, thereby reducing the overall cost and size of our systems. However, achieving the necessary precision in the ODU to acquire accurate terahertz time-domain signals remains a crucial aspect. To address this issue, we have developed and enhanced an interferometric extension for UHRR-THz-TDS systems. This extension is inexpensive, compact, and easy to incorporate. In this article, we present the system setup, the extension itself, and the algorithmic procedure for reconstructing the delay axis based on the interferometric reference signal. We evaluate a dataset comprising 10,000 signal traces and report a standard deviation of the measured terahertz phase at 1.6 THz as low as 3 mrad. Additionally, we demonstrate a remaining peak-to-peak jitter of only 20 fs and a record-high peak signal-to-noise ratio of 133 dB at 100 GHz after averaging. The method presented in this paper allows for simplified THz-TDS system builds, reducing bulk and cost. As a result, it further facilitates the transition of terahertz technologies from laboratory to field applications.

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Spectral Shaping of a Superluminescent Diode for Terahertz Cross-Correlation Spectroscopy

Cited by 5 publications

References 20 publications

THz Systems Exploiting Photonics and Communications Technologies

THz Systems Exploiting Photonics and Communications Technologies

Laser Diode based THz-TDS System with 133 dB peak Signal-to-Noise Ratio

Laser diode based THz-TDS system with 133 dB peak signal-to-noise ratio at 100 GHz

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