We experimentally demonstrate frequency non-degenerate photon-pair generation via spontaneous four-wave mixing from a novel CS2-filled microstructured optical fiber. CS2 has high nonlinearity, narrow Raman lines, a broad transmission spectrum, and also has a large index contrast with the microstructured silica fiber. We can achieve phase matching over a large spectral range by tuning the pump wavelength, allowing the generation of idler photons in the infrared region, which is suitable for applications in quantum spectroscopy. Moreover, we demonstrate a coincidence-to-accidental ratio of larger than 90 and a pair generation efficiency of about [Formula: see text] per pump pulse, which shows the viability of this fiber-based platform as a photon-pair source for quantum technology applications.
Here, we demonstrate the properties of bromotrichloromethane (CBrCl3) in the context of ultrafast supercontinuum generation in liquid-core fibers. Broadband interferometric and spectroscopic measurements of liquids and fibers indicate suitable optical properties of this halomethane for near-IR supercontinuum generation, which were confirmed in corresponding experiments using ultrashort pulses. The associated simulations showed consistent broadband power redistributions, thus confirming that this halomethane is a suitable candidate for ultrafast nonlinear frequency conversion in liquid-core fibers. It uniquely combines the advantages of an inorganic, i.e., CH-free, material with a non-vanishing hyperpolarizability, allowing to anticipate an integration of second-order nonlinearity into the fiber.
We demonstrate supercontinuum generation in a liquid-core microstructured optical fiber using carbon disulfide as the core material. The fiber provides a specific dispersion landscape with a zero-dispersion wavelength approaching the telecommunication domain where the corresponding capillary-type counterpart shows unsuitable dispersion properties for soliton fission. The experiments were conducted using two pump lasers with different pulse duration (30 fs and 90 fs) giving rise to different non-instantaneous contributions of carbon disulfide in each case. The presented results demonstrate an extraordinary high conversion efficiency from pump to soliton and to dispersive wave, overall defining a platform that enables studying the impact of non-instantaneous responses on ultrafast soliton dynamics and coherence using straightforward pump lasers and diagnostics.
Accurate dispersion management is key for efficient nonlinear light generation. Here, we demonstrate that composite-liquid-core fibers-fibers with binary liquid mixtures as the core medium-allow for accurate and tunable control of dispersion, loss, and nonlinearity. Specifically, we show numerically that mixtures of organic and inorganic solvents in silica capillaries yield anomalous dispersion and reasonable nonlinearity at telecommunication wavelengths. This favorable operation domain is experimentally verified in various liquid systems through dispersion-sensitive supercontinuum generation, with all results being consistent with theoretical designs and simulations. Our results confirm that mixtures introduce a cost-effective means for liquid-core fiber design that allows for loss control, nonlinear response variation, and dispersion engineering.
Dark-field imaging is a well-known optical method for obtaining edge-enhanced images of objects containing steep gradients in either amplitude or phase. Edge enhancement is commonly achieved by using a small physical obstruction in the center of the Fourier plane of a 4f imaging setup. By blocking the low spatial frequencies in the center of the Fourier plane, only the higher spatial frequencies from the object reach the image plane. In this work, simultaneous optical image processing (i.e., dark-field imaging) and sum-frequency generation are performed by placing a periodically poled lithium niobate crystal in the Fourier plane of a 4f setup and using a 1575 nm upconversion pump beam with a dark core. We demonstrate upconversion dark-field (UDF) imaging in which edge-enhanced images are obtained at the upconverted wavelength ($\sim{630}\;{\rm nm}$â¼630nm) as a result of infrared object illumination ($\sim 1\;\unicode{x00B5}{\rm m}$â¼1µm). Furthermore, we experimentally confirm that UDF imaging can be extended from collinear to noncollinear interactions between the signal and pump. The presented system allows for adjustment of the spatial cutoff frequency while maximizing the power conversion efficiency. Simultaneous collinear and noncollinear upconversion imaging of phase objects is demonstrated using broadband 1 µm illumination with a spectral bandwidth of 6 nm-resulting in a UDF imaging system with an enhanced field of view at video frame rates.
We show that the ultrafast nonlinear dynamics in supercontinuum generation can be tailored via mixture-based liquid core fibers. Samples containing mixtures of inorganic solvents allow changing dispersion from anomalous to normal, i.e., shifting zero dispersion across pump laser wavelength. A significant control over modulation instability and four-wave mixing has been demonstrated experimentally in record-long (up to 60 cm) samples in agreement with simulations when using sub-psec pulses at 1.555 µm. The smallest concentration ratio yields indications of soliton-fission based supercontinuum generation at soliton numbers that are beyond the coherence limit. The presented dispersion tuning scheme allows creating unprecedented dispersion landscapes for accessing unexplored nonlinear phenomena and selected laser sources.
Mid-infrared hyperspectral imaging has in the past decade emerged as a promising tool for medical diagnostics. In this work, nonlinear frequency upconversion based hyperspectral imaging in the 6 to 8 µm spectral range is presented for the first time, using both broadband globar and narrowband quantum cascade laser illumination. AgGaS2 is used as the nonlinear medium for sum frequency generation using a 1064 nm mixing laser. Angular scanning of the nonlinear crystal provides broad spectral coverage at every spatial position in the image. This study demonstrates the retrieval of series of monochromatic images acquired by a silicon based CCD camera, using both broadband and narrowband illumination and a comparison is made between the two illumination sources for hyperspectral imaging.
