A 3.5-THz, ×6-Harmonic, Single-Ended Schottky Diode Mixer for Frequency Stabilization of Quantum-Cascade Lasers

Jayasankar, Divya; Drakinskiy, Vladimir; Rothbart, Nick; Richter, Heiko; Lü, Xiang; Schrottke, L.; Grahn, H. T.; Wienold, Martin; Hübers, Heinz‐Wilhelm; Sobis, Peter; Stake, Jan

doi:10.1109/tthz.2021.3115730

“…The overall sensitivity of the design was analyzed employing a relative sensitivity coefficient RS S11 [27], [28]. The coefficient is described as follows:…”

Section: B Sensitivity Analysis and Fabricationmentioning

confidence: 99%

Ultra-Wideband 90° Waveguide Twist for THz Applications

López

¹

,

Montofre

²

,

Desmaris

³

et al. 2023

IEEE Trans. THz Sci. Technol.

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We report on the design, fabrication, and characterization of a novel 90º waveguide step twist with 56% fractional bandwidth. The proposed twist provides 90º field rotation in the frequency range 210-375 GHz. The experimental results are in good agreement with the electromagnetic simulations showing an insertion loss below 0.3 dB and a return loss better than 20 dB over most of the band. The ultra-wideband performance, tolerance to fabrication inaccuracies and compactness makes the proposed design attractive for various mm and sub-millimeter applications. The twist geometry is optimized for simple fabrication through direct milling. Furthermore, the design remains highly compact since both steps are fabricated on a single washer.

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“…A subharmonic diode mixer is used to down convert the QC-VECSEL signal to an intermediate RF frequency that can then be phase locked to an RF reference source. This strategy has been demonstrated previously with ridge waveguide THz QCLs [19,20,41]. Here, we start with a ~11 GHz signal generator (Agilent E8257D), followed by a Spacek Labs tripling amplifier, followed by a JPL-made passive tripler.…”

Section: Qc-vecsel Construction and Mountingmentioning

confidence: 99%

Phase locking of THz QC-VECSELs to a microwave reference

Curwen¹,

Kawamura²,

Hayton³

et al. 2023

Preprint

0

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<p>High resolution frequency study and phase-locking have been performed on terahertz quantum-cascade vertical-external-cavity surface-emitting-lasers at 2.5 THz and 3.4 THz. A subharmonic diode mixer is used to downconvert the THz signal to a gigahertz intermediate frequency (IF). Feedback from reflections at the mixer are observed to have a strong influence on the free-running QC-VECSEL frequency stability as a result of efficient coupling to free-space compared to more typical ridge waveguide lasers. Instabilities in feedback result in free-running linewidths of tens of MHz, and at times >100 MHz. The QC-VECSEL IF signal is phase locked to a 100 MHz reference using the bias on the device as a means of error correction. Between 90-95% of the QC-VECSEL signal is locked within 2 Hz of the multiplied RF reference, and amplitude fluctuations on the order of 1-10% are observed, depending on the bias point of the QC-VECSEL. The bandwidth of the locking loop is ~1 MHz. Many noise peaks in the IF signal corresponding to mechanical resonances in the 10 Hz-10 kHz range are observed. These peaks are generally -30 to -60 dB below the main tone, and are below the phase noise level of the multiplied RF reference which ultimately limits the phase noise of the locked QC-VECSEL.</p>

show abstract

“…A subharmonic diode mixer is used to down convert the QC-VECSEL signal to an intermediate RF frequency that can then be phase locked to an RF reference source. This strategy has been demonstrated previously with ridge waveguide THz QCLs [19,20,41]. Here, we start with a ~11 GHz signal generator (Agilent E8257D), followed by a Spacek Labs tripling amplifier, followed by a JPL-made passive tripler.…”

Section: Qc-vecsel Construction and Mountingmentioning

confidence: 99%

Phase locking of THz QC-VECSELs to a microwave reference

Curwen¹,

Kawamura²,

Hayton³

et al. 2023

Preprint

0

View full text Add to dashboard Cite

<p>High resolution frequency study and phase-locking have been performed on terahertz quantum-cascade vertical-external-cavity surface-emitting-lasers at 2.5 THz and 3.4 THz. A subharmonic diode mixer is used to downconvert the THz signal to a gigahertz intermediate frequency (IF). Feedback from reflections at the mixer are observed to have a strong influence on the free-running QC-VECSEL frequency stability as a result of efficient coupling to free-space compared to more typical ridge waveguide lasers. Instabilities in feedback result in free-running linewidths of tens of MHz, and at times >100 MHz. The QC-VECSEL IF signal is phase locked to a 100 MHz reference using the bias on the device as a means of error correction. Between 90-95% of the QC-VECSEL signal is locked within 2 Hz of the multiplied RF reference, and amplitude fluctuations on the order of 1-10% are observed, depending on the bias point of the QC-VECSEL. The bandwidth of the locking loop is ~1 MHz. Many noise peaks in the IF signal corresponding to mechanical resonances in the 10 Hz-10 kHz range are observed. These peaks are generally -30 to -60 dB below the main tone, and are below the phase noise level of the multiplied RF reference which ultimately limits the phase noise of the locked QC-VECSEL.</p>

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A 3.5-THz, ×6-Harmonic, Single-Ended Schottky Diode Mixer for Frequency Stabilization of Quantum-Cascade Lasers

Cited by 20 publications

References 36 publications

Ultra-Wideband 90° Waveguide Twist for THz Applications

Ultra-Wideband 90° Waveguide Twist for THz Applications

Phase locking of THz QC-VECSELs to a microwave reference

Phase locking of THz QC-VECSELs to a microwave reference

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