Harmonic and subharmonic RF injection locking is demonstrated in a terahertz (THz) quantum-cascade vertical-external-cavity surface-emitting laser (QC-VECSEL). By tuning the RF injection frequency around integer multiples and submultiples of the cavity round-trip frequency, different harmonic and subharmonic orders can be excited in the same device. Modulation-dependent behavior of the device has been studied with recorded lasing spectral broadening and locking bandwidths in each case. In particular, harmonic injection locking results in the observation of harmonic spectra with bandwidths over 200 GHz. A semiclassical Maxwell-density matrix formalism has been applied to interpret QC-VECSEL dynamics, which aligns well with experimental observations.
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http://dx.doi.org/10.1021/acsphotonics.4c00608 | DOI Listing |
J Acoust Soc Am
December 2024
Department of Otorhinolaryngology and Head & Neck Surgery, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan.
The fundamental frequency (fo) is pivotal for quantifying vocal-fold characteristics. However, the accuracy of fo estimation in hoarse voices is notably low, and no definitive algorithm for fo estimation has been previously established. In this study, we introduce an algorithm named, "Spectral-based fo Estimator Emphasized by Domination and Sequence (SFEEDS)," which enhances the spectrum method and conducted comparative analyses with conventional estimation methods.
View Article and Find Full Text PDFACS Photonics
November 2024
Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States.
Harmonic and subharmonic RF injection locking is demonstrated in a terahertz (THz) quantum-cascade vertical-external-cavity surface-emitting laser (QC-VECSEL). By tuning the RF injection frequency around integer multiples and submultiples of the cavity round-trip frequency, different harmonic and subharmonic orders can be excited in the same device. Modulation-dependent behavior of the device has been studied with recorded lasing spectral broadening and locking bandwidths in each case.
View Article and Find Full Text PDFWe report the design and characterization of a femtosecond optical parametric oscillator containing an intracavity Herriott cell. Pumped by a 49.16-MHz Yb:fiber laser, the signal wavelength could be tuned over 1440-1530 nm, with the Herriott cell containing 81% of the free-space cavity length required for synchronous operation.
View Article and Find Full Text PDFSmall
December 2024
School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
Ising solvers are important for efficiently addressing non-deterministic polynomial-time (NP)-hard combinatorial optimization problems (COPs), where scalability and compactness are crucial for practical applications. In this study, an experimental demonstration of an oscillator-based Ising solver employing a highly scalable 4F InGaAs bi-stable resistor (biristor) is presented. It is first explored the oscillation behavior of the InGaAs biristor, establishing that classical Ising spins can be emulated using the sub-harmonic injection locking (SHIL) technique.
View Article and Find Full Text PDFPhys Med Biol
October 2024
Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, SHFJ, Orsay, France.
Cavitation dose monitoring plays a key role in ultrasound drug delivery to the brain. The use of capacitive micromachined ultrasonic transducer (CMUT) technology has a great potential for passive cavitation detection (PCD).Here, a circular (diameter 7 mm) CMUT centered at 5 MHz was designed to be inserted into a therapeutic transducer (1.
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