Showing papers on "Supercontinuum published in 2018"
TL;DR: In this article, the authors demonstrate a simple, yet effective, method for the direct generation of mid-infrared optical frequency combs in the region from 2.5 to 4.0μm from a conventional and compact erbium-fibre-based femtosecond laser in the telecommunication band.
Abstract: Mid-infrared optical frequency combs are of significant interest for molecular spectroscopy due to the large absorption of molecular vibrational modes on the one hand, and the ability to implement superior comb-based spectroscopic modalities with increased speed, sensitivity and precision on the other hand. Here, we demonstrate a simple, yet effective, method for the direct generation of mid-infrared optical frequency combs in the region from 2.5 to 4.0 μm (that is, 2,500–4,000 cm−1), covering a large fraction of the functional group region, from a conventional and compact erbium-fibre-based femtosecond laser in the telecommunication band (that is, 1.55 μm). The wavelength conversion is based on dispersive wave generation within the supercontinuum process in an unprecedented large-cross-section silicon nitride (Si3N4) waveguide with the dispersion lithographically engineered. The long-wavelength dispersive wave can perform as a mid-infrared frequency comb, whose coherence is demonstrated via optical heterodyne measurements. Such an approach can be considered as an alternative option to mid-infrared frequency comb generation. Moreover, it has the potential to realize compact dual-comb spectrometers. The generated combs also have a fine teeth-spacing, making them suitable for gas-phase analysis. The direct generation of mid-infrared optical frequency combs in the region 2.5–4.0 μm from a 1.55-μm conventional and compact erbium-fibre-based femtosecond laser is demonstrated via coherent dispersive wave generation in silicon nitride nanophotonic waveguides.
223 citations
TL;DR: Tissue imaging was demonstrated in transmission at selected wavelengths between 5.7 and 7.3 μm by point scanning over a sub-millimeter region of colon tissue, and the results were compared to images obtained from a commercial instrument.
Abstract: We present, to the best of our knowledge, the first demonstration of mid-infrared supercontinuum (SC) tissue imaging at wavelengths beyond 5 μm using a fiber-coupled SC source spanning 2–7.5 μm. The SC was generated in a tapered large-mode-area chalcogenide photonic crystal fiber in order to obtain broad bandwidth, high average power, and single-mode output for diffraction-limited imaging performance. Tissue imaging was demonstrated in transmission at selected wavelengths between 5.7 (1754 cm−1) and 7.3 μm (1370 cm−1) by point scanning over a sub-millimeter region of colon tissue, and the results were compared to images obtained from a commercial instrument.
121 citations
20 Apr 2018
TL;DR: In this article, the authors report supercontinuum generation in an air-clad $Si 0.6}$$Ge 0.4}$/Si waveguide that emits a broad spectrum spanning from 3.0 μm to 8.5 μm.
Abstract: Efficient on-chip molecule and bio-agent detection can be achieved by accessing strong molecular absorption lines in the mid-infrared, but it requires high output power broadband mid-IR sources. Here, we report supercontinuum generation in an air-clad $Si_{0.6}$$Ge_{0.4}$/Si waveguide that emits a broad spectrum spanning from 3.0 μm to 8.5 μm. These waveguides have anomalous dispersion and low propagation loss (<0.4 dB/cm) in the mid-IR, which leads to a supercontinuum output with a high average power of more than 10 mW on-chip. The realization of broadband mid-IR sources with high spectral brightness makes the SiGe-on-Si platform promising for a wide range of applications.
118 citations
TL;DR: The use of this x-ray radiation emerges as a single attosecond-to-femtosecond pulse with peak brightness exceeding 10^{26} photons/s/mrad^{2]/mm^{2}/1% bandwidth, these novel coherent x-rays sources are ideal for probing the fastest molecular and materials processes on femtose Cond-to -attosecond time scales and picometer length scales.
Abstract: Recent advances in high-order harmonic generation have made it possible to use a tabletop-scale setup to produce spatially and temporally coherent beams of light with bandwidth spanning 12 octaves, from the ultraviolet up to x-ray photon energies >1.6 keV. Here we demonstrate the use of this light for x-ray-absorption spectroscopy at the K- and L-absorption edges of solids at photon energies near 1 keV. We also report x-ray-absorption spectroscopy in the water window spectral region (284-543 eV) using a high flux high-order harmonic generation x-ray supercontinuum with 10^{9} photons/s in 1% bandwidth, 3 orders of magnitude larger than has previously been possible using tabletop sources. Since this x-ray radiation emerges as a single attosecond-to-femtosecond pulse with peak brightness exceeding 10^{26} photons/s/mrad^{2}/mm^{2}/1% bandwidth, these novel coherent x-ray sources are ideal for probing the fastest molecular and materials processes on femtosecond-to-attosecond time scales and picometer length scales.
116 citations
TL;DR: In this article, an octave-spanning coherent supercontinuum was generated in a silicon waveguide covering the spectral region from the near-to short-wave-infrared, and the generated signal spans the wavelength range from the edge of the silicon transmission window, approximately 1.06 to beyond 2.4
Abstract: Efficient complementary metal-oxide semiconductor-based nonlinear optical devices in the near-infrared are in strong demand. Due to two-photon absorption in silicon, however, much nonlinear research is shifting towards unconventional photonics platforms. In this work, we demonstrate the generation of an octave-spanning coherent supercontinuum in a silicon waveguide covering the spectral region from the near- to shortwave-infrared. With input pulses of 18 pJ in energy, the generated signal spans the wavelength range from the edge of the silicon transmission window, approximately 1.06 to beyond 2.4 μm, with a −20 dB bandwidth covering 1.124–2.4 μm. An octave-spanning supercontinuum was also observed at the energy levels as low as 4 pJ (−35 dB bandwidth). We also measured the coherence over an octave, obtaining , in good agreement with the simulations. In addition, we demonstrate optimization of the third-order dispersion of the waveguide to strengthen the dispersive wave and discuss the advantage of having a soliton at the long wavelength edge of an octave-spanning signal for nonlinear applications. This research paves the way for applications, such as chip-scale precision spectroscopy, optical coherence tomography, optical frequency metrology, frequency synthesis and wide-band wavelength division multiplexing in the telecom window. A silicon-based source that generates a wide spectrum of light, spanning the near-infrared transparency window of silicon, has been made. Supercontinuum generation involves using short, high-power pulses to generate broad continuous spectra by propagating them through nonlinear media. Supercontinuum sources are needed for applications in spectroscopy and optical coherence tomography. Silicon is an attractive medium since it is compatible with standard semiconductor fabrication processes but it suffers from losses due to nonlinear processes such as two-photon absorption. Now, Neetesh Singh of Massachusetts Institute of Technology in the USA and co-workers have realized a fully coherent supercontinuum generation in a silicon waveguide over a full octave that spans the near to shortwave infrared window. The researchers envision their source being used in applications such as chip-scale precision spectroscopy, optical frequency metrology and optical communications.
113 citations
TL;DR: The presented concept is based on power-scalable near-infrared lasers emitting at a wavelength near 1 μm, which pump optical parametric amplifiers, resulting in spectral coverage from 1.6 to 10.2 μm with power densities exceeding state-of-the-art synchrotron sources over the entire range.
Abstract: Spectroscopy in the wavelength range from 2 to 11 μm (900 to 5000 cm-1) implies a multitude of applications in fundamental physics, chemistry, as well as environmental and life sciences. The related vibrational transitions, which all infrared-active small molecules, the most common functional groups, as well as biomolecules like proteins, lipids, nucleic acids, and carbohydrates exhibit, reveal information about molecular structure and composition. However, light sources and detectors in the mid-infrared have been inferior to those in the visible or near-infrared, in terms of power, bandwidth, and sensitivity, severely limiting the performance of infrared experimental techniques. This article demonstrates the generation of femtosecond radiation with up to 5 W at 4.1 μm and 1.3 W at 8.5 μm, corresponding to an order-of-magnitude average power increase for ultrafast light sources operating at wavelengths longer than 5 μm. The presented concept is based on power-scalable near-infrared lasers emitting at a wavelength near 1 μm, which pump optical parametric amplifiers. In addition, both wavelength tunability and supercontinuum generation are reported, resulting in spectral coverage from 1.6 to 10.2 μm with power densities exceeding state-of-the-art synchrotron sources over the entire range. The flexible frequency conversion scheme is highly attractive for both up-conversion and frequency comb spectroscopy, as well as for a variety of time-domain applications.
89 citations
TL;DR: An all-fiber supercontinuum source that generates a continuous spectrum from 1.6 μm to >11 μm with 417 mW on-time average power at 33% duty cycle is demonstrated.
Abstract: We demonstrate an all-fiber supercontinuum source that generates a continuous spectrum from 1.6 μm to >11 μm with 417 mW on-time average power at 33% duty cycle. By utilizing a master oscillator power amplifier pump with three amplification stages and concatenating solid core ZBLAN, arsenic sulfide, and arsenic selenide fibers, we shift 1550 nm light to ∼4.5 μm, ∼6.5 μm, and >11 μm, respectively. With 69 mW past 7.5 μm, this source provides both high power and broad spectral expansion, while outputting a single fundamental mode.
89 citations
TL;DR: In this article, a supercontinuum source integrated on-chip spectroscopic sensor is presented, where nonlinear Ge22Sb18Se60 chalcogenide glass waveguides are used as a unified platform for both broadband super-continuum generation and chemical detection.
Abstract: On-chip spectroscopic sensors have attracted increasing attention for portable and field-deployable chemical detection applications. So far, these sensors largely rely on benchtop tunable lasers for spectroscopic interrogation. Large footprint and mechanical fragility of the sources, however, preclude compact sensing system integration. In this paper, we address the challenge through demonstrating, for the first time to our knowledge, a supercontinuum source integrated on-chip spectroscopic sensor, where we leverage nonlinear Ge22Sb18Se60 chalcogenide glass waveguides as a unified platform for both broadband supercontinuum generation and chemical detection. A home-built, palm-sized femtosecond laser centering at 1560 nm wavelength was used as the pumping source. Sensing capability of the system was validated through quantifying the optical absorption of chloroform solutions at 1695 nm. This work represents an important step towards realizing a miniaturized spectroscopic sensing system based on photonic chips.
83 citations
TL;DR: It is demonstrated that the PMI introduces a power dependence not found in a scalar model, which means that even with short ~120 fs pump pulses the coherence of ANDi SC can be degraded at reasonable power levels above ~40 kW.
Abstract: Supercontinuum (SC) generated with all-normal dispersion (ANDi) fibers has been of special interest in recent years due to its potentially superior coherence properties when compared to anomalous dispersion-pumped SC. However, care must be taken in the design of such sources since too long pump pulses and fiber length has been demonstrated to degrade the coherence. To assess the noise performance of ANDi fiber SC generation numerically, a scalar single-polarization model has so far been used, thereby excluding important sources of noise, such as polarization modulational instability (PMI). In this work we numerically study the influence of pump power, pulse length and fiber length on coherence and relative intensity noise (RIN), taking into account both polarization components in a standard ANDi fiber for SC generation pumped at 1064 nm. We demonstrate that the PMI introduces a power dependence not found in a scalar model, which means that even with short ~120 fs pump pulses the coherence of ANDi SC can be degraded at reasonable power levels above ~40 kW. We further demonstrate how the PMI significantly decreases the pump pulse length and fiber length at which the coherence of the ANDi SC is degraded. The numerical predictions are confirmed by RIN measurements of fs-pumped ANDi fiber SC.
81 citations
TL;DR: In this paper, the authors compared the brightness of IR supercontinuum (SC) sources with those of synchrotron IR beamlines and SiC thermal emitters (Globars).
80 citations
20 Oct 2018
TL;DR: In this paper, the authors used a 60 cm long fluorotellurite fiber with a core diameter of 6.8μm as the nonlinear medium and a high power 1980-nm femtosecond fiber laser as the pump source.
Abstract: High power mid-infrared supercontinuum (SC) laser sources are important for a wide range of applications in sensing, spectroscopy, imaging, defense, and security. Despite recent advances on high power mid-infrared SC laser sources using fluoride fibers, the lack of mid-infrared fibers with good chemical and thermal stability remains a significant technological challenge. Here we show that all solid fluorotellurite fibers we developed can be used as the nonlinear media for constructing 10-W-level mid-infrared SC laser sources. All solid fluorotellurite fibers are fabricated by using a rod-in-tube method. The core and cladding materials are TeO2-BaF2-Y2O3 and TeO2 modified fluoroaluminate glasses with good water resistance and high transition temperature (∼424°C). By using a 60 cm long fluorotellurite fiber with a core diameter of 6.8 μm as the nonlinear medium and a high power 1980 nm femtosecond fiber laser as the pump source, we obtain 10.4 W SC generation from 947 to 3934 nm in the fiber for a pump power of ∼15.9 W, and the corresponding optical-to-optical conversion efficiency is about 65%. The spectral broadening is caused by self-phase modulation, soliton fission, soliton self-frequency shift, and dispersive wave generation. Our results show that all solid fluorotellurite fiber can be used for constructing high power mid-infrared SC laser sources for real applications.
TL;DR: In this article, a gallium-arsenide-on-insulator (GaAs) platform for nonlinear photonics is demonstrated, and the use of a silica cladding results in waveguides with a large refractive index contrast and low propagation loss.
Abstract: Tremendous scientific progress has been achieved through the development of nonlinear integrated photonics. Prominent examples are Kerr frequency comb generation in microresonators, and supercontinuum generation and frequency conversion in nonlinear photonic waveguides. A high conversion efficiency is enabling for applications of nonlinear optics, including such broad directions as high-speed optical signal processing, metrology, and quantum communication and computation. In this work, a gallium-arsenide-on-insulator (GaAs) platform for nonlinear photonics is demonstrated. GaAs has among the highest second- and third-order nonlinear optical coefficients, and the use of a silica cladding results in waveguides with a large refractive index contrast and low propagation loss for expanded designs of nonlinear processes. By harnessing these properties and developing nanofabrication with GaAs, a record normalized second-harmonic efficiency of 13 000%�W-1cm-2 at a fundamental wavelength of 2��m is reported. This work paves the way for high performance nonlinear photonic integrated circuits, which not only can transition advanced functionalities outside the lab through fundamentally reduced power consumption and footprint, but also enables future optical sources and detectors.
TL;DR: In this paper, the history and recent developments in mid-infrared supercontinuum generation from chalcogenide fibers according to three kinds of fiber structures: step-index, microstructured and tapered fibers.
Abstract: Chalcogenide glasses have the advantages of a wide transparency window (over 20 μm) and high optical nonlinearity (up to a thousand times greater than that of silica glasses), making them good candidates for mid-infrared supercontinuum generation. In this review, we describe both the history and recent developments in mid-infrared supercontinuum generation from chalcogenide fibers according to three kinds of fiber structures: step-index, microstructured and tapered fibers. We also review the coherence properties of mid-infrared supercontinuum generation and all-fiber supercontinuum sources based on chalcogenide fibers.
20 Apr 2018
TL;DR: In this article, the authors demonstrate that fiber-based supercontinuum sources in the mid-infrared enable fast spectral mapping of localized material properties with close to diffraction-limited resolution.
Abstract: Fourier-transform infrared (FTIR) spectromicroscopy combines the spatial resolution of optical microscopy with the spectral selectivity of vibrational spectroscopy. Synchrotron sources can provide diffraction-limited beams in the infrared, and therefore synchrotron-based FTIR spectromicroscopy is nowadays an indispensable tool for biology and materials science studies where high spatial resolution is required. However, the increasing need for accurate and highly spatially resolved characterization is calling for alternative laboratory-based sources to complement synchrotron radiation. To date, the low brightness of thermal emitters or high temporal coherence and narrow bandwidth or tunability of laser sources have hindered the progress of bench-top FTIR spectromicroscopy. Here, we demonstrate that fiber-based supercontinuum sources in the mid-infrared enable fast spectral mapping of localized material properties with close to diffraction-limited resolution (3 μm×3 μm) and pave the way to table-top, on-demand, fast, and highly spatially resolved studies. We illustrate these capabilities by imaging thin sections of human liver samples and compare the results and performance with those obtained using a synchrotron source.
TL;DR: Recent spectacular advances in filamentation of ultra-short TW-class lasers are reviewed both in the laboratory and in the field, their underlying mechanisms are revealed, and the applicability of using these new non-linear photonic catalysts for real scale weather control is discussed.
Abstract: Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1-1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015-1017 cm-3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013-1014 W cm-2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.
TL;DR: In this paper, the authors demonstrate soliton generation in a 15 GHz silica resonator, and chip-scale supercontinuum generation at 15 GHz pulse rates in a silicon nitride waveguide.
Abstract: The development of chip-scale frequency combs would enable precision optical-frequency measurements outside the laboratory, in real-world operating environments. Microresonators supporting soliton pulses provide an important step towards this goal, but reliable soliton stabilization and supercontinuum generation is challenging. The authors demonstrate streamlined soliton generation in a 15-GHz silica resonator, and chip-scale supercontinuum generation at 15-GHz pulse rates in a silicon nitride waveguide. Self-referencing this frequency-comb system with $f-2f$ interferometry has allowed them to measure the relative drift between two optical references, an important advance in metrology.
TL;DR: To the knowledge, this is the first high peak power fiber-based gas Raman laser in mid-infrared region and a range of applications in supercontinuum generation, laser surgery, molecular tracing and gas detection are in prospect.
Abstract: We demonstrate a 2.8 μm gas Raman laser in a methane-filled hollow-core negative-curvature fiber with average power of 113 mW, pulse energy of 113 μJ and estimated peak power of 9.5 MW. Raman quantum efficiency of 40% has been reached from the pump source at 1.064 μm to the 2nd order vibrational Stokes at 2.812 μm using 1.8 MPa methane gas. To our knowledge, this is the first high peak power fiber-based gas Raman laser in mid-infrared region and a range of applications in supercontinuum generation, laser surgery, molecular tracing and gas detection are in prospect.
TL;DR: It is shown that C2Cl4 has the potential for observing non-instantaneous soliton dynamics along meters of liquid-core fiber opening a feasible route for directly observing hybrid Soliton dynamics.
Abstract: We report on soliton-fission mediated infrared supercontinuum generation in liquid-core step-index fibers using highly transparent carbon chlorides (CCl4, C2Cl4) By developing models for the refractive index dispersions and nonlinear response functions, dispersion engineering and pumping with an ultrafast thulium fiber laser (300 fs) at 192 μm, distinct soliton fission and dispersive wave generation was observed, particularly in the case of tetrachloroethylene (C2Cl4) The measured results match simulations of both the generalized and a hybrid nonlinear Schrodinger equation, with the latter resembling the characteristics of non-instantaneous medium via a static potential term and representing a simulation tool with substantially reduced complexity We show that C2Cl4 has the potential for observing non-instantaneous soliton dynamics along meters of liquid-core fiber opening a feasible route for directly observing hybrid soliton dynamics
TL;DR: In this article, the authors proposed an all-solid microstructured fiber composed only of hexagonal glass elements, which has an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55μm.
Abstract: High flatness, wide bandwidth, and high-coherence properties of supercontinuum (SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, since special dispersion profiles are required, especially when pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from approximately 1030 to 2030 nm (corresponding to nearly one octave) with flatness <3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 3.19 fs, corresponding to only 0.62 optical cycles.
Institut national de la recherche scientifique1, University of Glasgow2, Harvard University3, University of Sussex4, Chinese Academy of Sciences5, City University of Hong Kong6, Saint Petersburg State University of Information Technologies, Mechanics and Optics7, Swinburne University of Technology8, University of Electronic Science and Technology of China9
TL;DR: An actively-controlled photonic chip is used to prepare and manipulate patterns of femtosecond optical pulses that give access to an enhanced parameter space in the framework of supercontinuum generation, and takes advantage of machine learning concepts to exploit this tunable access.
Abstract: Modern optical systems increasingly rely on complex physical processes that require accessible control to meet target performance characteristics. In particular, advanced light sources, sought for, for example, imaging and metrology, are based on nonlinear optical dynamics whose output properties must often finely match application requirements. However, in these systems, the availability of control parameters (e.g., the optical field shape, as well as propagation medium properties) and the means to adjust them in a versatile manner are usually limited. Moreover, numerically finding the optimal parameter set for such complex dynamics is typically computationally intractable. Here, we use an actively controlled photonic chip to prepare and manipulate patterns of femtosecond optical pulses that give access to an enhanced parameter space in the framework of supercontinuum generation. Taking advantage of machine learning concepts, we exploit this tunable access and experimentally demonstrate the customization of nonlinear interactions for tailoring supercontinuum properties.
TL;DR: In this review, the fundamentals and fabrication of PCF infiltrated with different materials are discussed, and potential applications of infiltrated PCF sensors are reviewed, identifying the challenges and limitations to scale up and commercialize this novel technology.
Abstract: Photonic crystal fibers (PCFs) are a special class of optical fibers with a periodic arrangement of microstructured holes located in the fiber's cladding. Light confinement is achieved by means of either index-guiding, or the photonic bandgap effect in a low-index core. Ever since PCFs were first demonstrated in 1995, their special characteristics, such as potentially high birefringence, very small or high nonlinearity, low propagation losses, and controllable dispersion parameters, have rendered them unique for many applications, such as sensors, high-power pulse transmission, and biomedical studies. When the holes of PCFs are filled with solids, liquids or gases, unprecedented opportunities for applications emerge. These include, but are not limited in, supercontinuum generation, propulsion of atoms through a hollow fiber core, fiber-loaded Bose⁻Einstein condensates, as well as enhanced sensing and measurement devices. For this reason, infiltrated PCF have been the focus of intensive research in recent years. In this review, the fundamentals and fabrication of PCF infiltrated with different materials are discussed. In addition, potential applications of infiltrated PCF sensors are reviewed, identifying the challenges and limitations to scale up and commercialize this novel technology.
TL;DR: A chip-scale f-2f interferometer for carrier-envelope-offset frequency (fCEO) detection is demonstrated by simultaneously producing octave-spanning coherent supercontinuum generation and second-harmonic generation in a single dispersion-engineered silicon nitride waveguide.
Abstract: We demonstrate a chip-scale f−2f interferometer for carrier-envelope-offset frequency (f
CEO
) detection This is enabled by simultaneously producing octave-spanning coherent supercontinuum generation and second-harmonic generation in a single dispersion-engineered silicon nitride waveguide We measure the f
CEO
beatnote of an 80 MHz modelocked pump source with a signal-to-noise ratio of 25 dB Our simple approach for f−2f interferometry enables a straightforward route towards a chip-scale self-referenced frequency comb source that can operate at low pulse energies
TL;DR: The presented results show that a high-quality tellurite fiber is a promising candidate for developing lasers in the 2.3 μm atmospheric window which are particularly relevant for applications in gas sensing, eye-safe laser radars, breath analysis, remote sensing and stand-off trace gas detection.
Abstract: Ultrabroadband amplification and two-color CW lasing simultaneously near 1.9 μm and 2.3 μm in a Tm3+-doped tellurite fiber were demonstrated experimentally, for the first time to the best of our knowledge. A low-loss Tm3+-doped core fiber from TeO2–ZnO–La2O3–Na2O glasses stable against crystallization was produced by a special technique, providing a low concentration of hydroxyl groups. Supercontinuum from a highly GeO2 doped silica fiber pumped by an Er fiber laser system was used as a seed for an amplifier. A maximum gain of 30 dB and 7 dB was measured at 1.9 μm and 2.3 μm, respectively. We report detailed experimental and theoretical studies, which are in a very good agreement, of laser amplification and generation in the manufactured fiber with carefully measured and calculated parameters. A quantitatively verified numerical model was used to predict power scalability at 2.3 μm in schemes with optimized parameters at increased pump power. The presented results show that a high-quality tellurite fiber is a promising candidate for developing lasers in the 2.3 μm atmospheric window which are particularly relevant for applications in gas sensing, eye-safe laser radars, breath analysis, remote sensing and stand-off trace gas detection.
TL;DR: In this article, the infrared supercontinuum (SC) generation in step-index fluoroindate-based fiber by using an all-fiber laser source was reported.
Abstract: We report on infrared supercontinuum (SC) generation in step-index fluoroindate-based fiber by using an all-fiber laser source. In comparison to widely used ZBLAN fibers for high-power mid-infrared (MIR) SC generation, fluoroindate fibers have multiphoton absorption edges at significantly longer wavelengths and can sustain similar intensities. Recent developments highlighted in the present study allowed the production of fluoroindate fibers with MIR background loss of 2 dB/km, which is similar to or even better than ZBLAN fibers. By using an all-fiber picosecond laser source based on an erbium amplifier followed by a thulium power amplifier, we demonstrate the generation of 1.0 W infrared SC spanning over 2.25 octaves from 1 μm to 5 μm. The generated MIR SC also exhibits high spectral flatness with a 6 dB spectral bandwidth from 1.91 μm to 4.77 μm and an average power two orders of magnitude greater than in previous demonstrations with a similar spectral distribution.
TL;DR: The development and performances of the first mid-infrared Fourier-domain optical coherence tomography based on a supercontinuum source and low-cost pyroelectric detector are reported, designed to operate in the spectral region around 4 μm.
Abstract: Optical technology in the mid-infrared wavelength range is currently a rapidly developing field initiated by the availability of novel high-power and spatially coherent sources. Non-destructive testing techniques based on these sources are very promising for industrial and medical applications. However, there are still many engineering problems due to the technical challenges and high prices of the optical elements suitable for the mid-infrared region. In this paper, we report the development and performances of the first mid-infrared Fourier-domain optical coherence tomography based on a supercontinuum source and low-cost pyroelectric detector. The system is designed to operate in the spectral region around 4 μm. Experimental results are demonstrated for detections of embedded microstructures in ceramic materials and subsurface oil paint layers.
TL;DR: A high repetition rate optical parametric chirped-pulse amplification (OPCPA) laser system based on fiber-laser-seeded Innoslab to generate few-cycle pulses around 2 µm with passively stable carrier-envelope phase (CEP) by difference frequency generation (DFG).
Abstract: We developed a high repetition rate optical parametric chirped-pulse amplification (OPCPA) laser system based on fiber-laser-seeded Innoslab to generate few-cycle pulses around 2 µm with passively stable carrier-envelope phase (CEP) by difference frequency generation (DFG). Incorporating a piezo mirror before the DFG stage permits rapid CEP control. The OPCPA system is seeded by a stable supercontinuum generated in bulk material with the picosecond Innoslab pulses. Few-cycle pulses with durations of 17 fs and energies of over 100 μJ were produced in a single OPCPA stage. Three different nonlinear crystals: BBO, BiBO, and LNB were tested in the final parametric amplifier, and their average power related limitations are addressed.
TL;DR: It is demonstrated how an SC source combined with a tunable filter allows high-resolution spectroscopic photoacoustic imaging and the spectroscopy of lipids in the first overtone transition band of C-H bonds (1650-1850 nm).
Abstract: We propose a cost-effective high-pulse energy supercontinuum (SC) source based on a telecom range diode laser-based amplifier and a few meters of standard single-mode optical fiber, with a pulse energy density as high as ~25 nJ/nm in the 1650-1850 nm regime (factor >3 times higher than any SC source ever used in this wavelength range). We demonstrate how such an SC source combined with a tunable filter allows high-resolution spectroscopic photoacoustic imaging and the spectroscopy of lipids in the first overtone transition band of C-H bonds (1650-1850 nm). We show the successful discrimination of two different lipids (cholesterol and lipid in adipose tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue at three different locations. The proposed high-pulse energy SC laser paves a new direction towards compact, broadband and cost-effective source for spectroscopic photoacoustic imaging.
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TL;DR: The first practical mid-infrared spectral-domain optical coherence tomography system is demonstrated, with immediate applications in real-time non-destructive testing for the inspection of defects and thickness measurements in samples that exhibit strong scattering at shorter wavelengths.
Abstract: The potential for improving the penetration depth of optical coherence tomography systems by using increasingly longer wavelength light sources has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at 4 micron central wavelength with an axial resolution of 8.6 microns is demonstrated. The system produces 2D cross-sectional images in real-time enabled by a high-brightness 0.9-4.7 micron mid-infrared supercontinuum source with 1 MHz pulse repetition rate for illumination and broadband upconversion of more than 1 micron bandwidth from 3.58-4.63 microns to 820-865 nm, where a standard 800 nm spectrometer can be used for fast detection. Images produced by the mid-infrared system are compared with those delivered by a state-of-the-art ultra-high-resolution near-infrared optical coherence tomography system operating at 1.3 {\mu}m, and the potential applications and samples suited for this technology are discussed. In doing so, the first practical mid-infrared optical coherence tomography system is demonstrated, with immediate applications in real-time non-destructive testing for the inspection of defects and thickness measurements in samples that are too highly scattering at shorter wavelengths.
TL;DR: A supercontinuum source based on a figure-eight Er-doped fiber ring cavity has been experimentally demonstrated with low repetition rate and wide spectrum was generated directly from the fiber resonator, which can be easily applied in numerous areas, such as the optical frequency metrology, optical spectroscopy, optical coherence tomography, optical communications, and medical sciences.
Abstract: A supercontinuum source based on a figure-eight Er-doped fiber ring cavity has been experimentally demonstrated with low repetition rate. The proposed configuration of the experiment is a figure-eight fiber laser grounded in Nonlinear Optical Loop Mirror (NOLM) technique. A broad spectrum of approximately 410 nm spanning the range 1315-1725 nm at the level of 30 dB can be obtained at a given average power of 2.6 mW and without any amplifier. Such wide spectrum can be directly achieved in the fiber resonator, which makes the structure compact and robust. By changing the pump power, the temporal pulse width can be adjusted accordingly. The pulse width is about 4 ns at the pump power of around 240 mW. The broadband spectrum was generated directly from the fiber resonator, which can be easily applied in numerous areas, such as the optical frequency metrology, optical spectroscopy, optical coherence tomography, optical communications, and medical sciences.
TL;DR: The recent progress in ultrafast real-time measurement techniques are exploited to demonstrate ultrafast, scan-free, ghost imaging in the frequency domain using a continuous spectrum from an incoherent supercontinuum light source with random spectral fluctuations.
Abstract: Ghost imaging is a technique that generates high-resolution images by correlating the intensity of two light beams, neither of which independently contains useful information about the shape of the object. Ghost imaging has been demonstrated in both the spatial and temporal domains, using incoherent classical light sources or entangled photon pairs. Here we exploit the recent progress in ultrafast real-time measurement techniques to demonstrate ultrafast, scan-free, ghost imaging in the frequency domain using a continuous spectrum from an incoherent supercontinuum light source with random spectral fluctuations. We demonstrate the application of this technique to broadband spectroscopic measurements of methane absorption performed with sub-nanometer resolution. Our results offer novel perspectives for remote sensing in low light conditions, or in spectral regions where sensitive detectors are lacking.