The phase-matching bandwidth of nonlinear crystal is of great significance in ultrashort laser pulse characterization. In order to satisfy the phase-matching bandwidth, ultra-thin nonlinear crystals are generally required. However, the significantly reduced conversion efficiency, as well as the machining difficulties, limits its applications. Here, we show that sufficient spectrum bandwidth response can be achieved for a thick crystal when the phase-matching wavelength is tuned outside of the spectral window of the measured pulse. By applying this phenomenon to a single-shot second-harmonic generation frequency resolved optical gating (SHG-FROG) device, we successfully characterized a few-cycle pulse using a 150µ-barium borate (BBO) crystal. The accuracy of the method was verified by comparing the conventional pulse retrieving approach with a 5µ BBO crystal, which has a sufficient phase-matching bandwidth.
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http://dx.doi.org/10.1364/OL.417098 | DOI Listing |
The non-oxide BaGaSe (BGSe) crystal with broad transparency range, large nonlinearity, and high damage threshold has been widely utilized to build optical parametric oscillators/amplifiers that convert the well-developed near-infrared pump laser around 1 µm into the developing mid-infrared radiation. However, the inherent narrow phase-matching bandwidth of BGSe with a pump around 1 µm hampers the generation of ultrashort mid-infrared pulses. Here, we demonstrate that by pumping the BGSe crystal around 2 µm, it is possible to achieve a sufficient phase-matching bandwidth to support ultrashort pulses across a broad mid-infrared spectral range.
View Article and Find Full Text PDFSensors (Basel)
December 2024
Department of Mechanical Engineering, Stanford University, Stanford, CA 93405, USA.
Distributed feedback lasers, which feature rapid wavelength tunability, are not presently available in the yellow and orange spectral regions, impeding spectroscopic studies of short-lived species that absorb light in this range. To meet this need, a rapidly tunable laser system was constructed, characterized, and demonstrated for measurements of the NH radical at 597.4 nm.
View Article and Find Full Text PDFJ Chem Phys
December 2024
Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA.
Generating wavelength-tunable picosecond laser pulses from an ultrafast laser source is essential for femtosecond stimulated Raman scattering (FSRS) measurements. Etalon filters produce narrowband (picosecond) pulses with an asymmetric temporal profile that is ideal for stimulated resonance Raman excitation. However, direct spectral filtering of femtosecond laser pulses is typically limited to the laser's fundamental and harmonic frequencies due to very low transmission of broad bandwidth pulses through an etalon.
View Article and Find Full Text PDFThe polarization splitter-rotator (PSR) is a key device for polarization processing in polarization diversity systems, which has wide applications in achieving polarization independence and mixed multiplexing. However, it remains a significant challenge to simultaneously achieve a better balance in bandwidth, crosstalk (CT), polarization extinction ratio (PER), and compact footprint of the PSR. In this article, a photonic crystal nanobeam (PCN) structure is introduced to PSR for large bandwidth and compact size, with a device length of only 104 µm.
View Article and Find Full Text PDFThin-film lithium niobate (TFLN) waveguides have emerged as a pivotal platform for on-chip spontaneous parametric down-conversion (SPDC), serving as a crucible for the generation of entangled photon pairs. The periodic poling of TFLN, while capable of generating high-efficiency SPDC, demands intricate fabrication processes that can be onerous in terms of scalability and manufacturability. In this work, we introduce a novel approach to the generation of entangled photon pairs via SPDC within TFLN waveguides, harnessing the principles of modal phase-matching (MPM).
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