We demonstrate a femtosecond tunable light source with a variable pulse repetition rate based on a synchronously pumped fiber-feedback optical parametric oscillator (FFOPO) that incorporates an extended-cavity design. The repetition rate can be reduced by an acousto-optical modulator in the FFOPO pump beam. The extended FFOPO cavity supports signal oscillation down to the 64 subharmonic. The high nonlinearity of the FFOPO threshold suppresses signal output for residual pump pulses that are transmitted by the pulse picker. We characterize the temporal pulse contrast ratio of the FFOPO signal output with a second-order cross-correlation measurement. This FFOPO system enables pulse picking with extraordinarily high values up to 111 dB suppression of adjacent pulses and exhibits a temporal contrast ratio that exceeds 130 dB. It generates fs-pulses with tunable wavelength from 1415-1750 nm and 2.5-3.8 µm and variable repetition rates ranging from 640 kHz to 41 MHz.
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http://dx.doi.org/10.1364/OE.439226 | DOI Listing |
J Clin Endocrinol Metab
January 2025
Department of Internal Medicine and Therapeutics, University of Pavia, 27100 Pavia, Italy.
Background: Thyroid nodules classified cytologically as low-risk indeterminate lesions (TIR3A) on fine-needle aspiration biopsy (FNAB) present a clinical challenge due to their uncertain malignancy risk. This single-center study aimed to evaluate the natural history of TIR3A nodules.
Materials And Methods: FNABs performed between July 2017 and December 2019 were retrospectively retrieved and patients with TIR3A nodules were evaluated at baseline and throughout a follow-up based on ultrasound (US) parameters and clinical data.
Phys Rev Lett
December 2024
Stanford University, Department of Mechanical Engineering, Stanford, California 94305, USA.
The extreme electric fields created in high-intensity laser-plasma interactions could generate energetic ions far more compactly than traditional accelerators. Despite this promise, laser-plasma accelerator experiments have been limited to maximum ion energies of ∼100 MeV/nucleon. The central challenge is the low charge-to-mass ratio of ions, which has precluded one of the most successful approaches used for electrons: laser wakefield acceleration.
View Article and Find Full Text PDFWe demonstrate a widely spaced, stabilized, and self-referenced opto-electronic oscillator driven electro-optic modulator based optical frequency comb. Using an ultra-stable Fabry-Perot etalon as a stable reference, we simultaneously stabilize a CW laser and generate a low noise and stable RF oscillation used to drive an electro-optic comb. In such a manner, the Fabry-Perot etalon pins both the carrier-envelope-offset frequency ( ) and the repetition rate of the comb in place ( ), eliminating the need for an external RF oscillator.
View Article and Find Full Text PDFRecent advancements in display technology have led to the development and diversification of complex glass materials. Among them, Corning's Lotus NXT glass offers excellent optical properties, high thermal stability, and dimensional accuracy, which are crucial for display applications. However, these characteristics make it difficult to apply pre-existing machining techniques developed for conventional glass materials directly to NXT glass.
View Article and Find Full Text PDFChirp modulation can generate a relatively flat electro-optic frequency comb (EO comb) and offers the advantage of frequency reconfigurability, demonstrating significant potential in high-precision sensing and absorption spectroscopy measurements. However, nonresonant devices such as waveguides are susceptible to limitations in modulation efficiency and bandwidth during electro-optic modulation. In this paper, by utilizing chirp modulation resonance mode, we have realized an EO comb based on a lithium niobate resonator with small tooth spacing and high flatness.
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