Fiber Supercontinuum Research Articles

Supercontinuum-tailoring multicolor imaging reveals spatiotemporal dynamics of heterogeneous tumor evolution

Tumor heterogeneity and tumor evolution contribute to cancer treatment failure. To understand how selective pressures drive heterogeneous tumor evolution, it would be useful to image multiple important components and tumor subclones in vivo. We propose a supercontinuum-tailoring two-photon microscope (SCT-TPM) and realize simultaneous observation of nine fluorophores with a single light beam, breaking through the ‘color barrier’ of intravital two-photon fluorescence imaging. It achieves excitation multiplexing only by modulating the phase of fiber supercontinuum (SC), allowing to capture rapid events of multiple targets with maintaining precise spatial alignment. We employ SCT-TPM to visualize the spatiotemporal dynamics of heterogeneous tumor evolution under host immune surveillance, particularly the behaviors and interactions of six tumor subclones, immune cells and vascular network, and thus infer the trajectories of tumor progression and clonal competition. SCT-TPM opens up the possibility of tumor lineage tracking and mechanism exploration in living biological systems.

Ultraflat, Monolithic, Highly Stable Supercontinuum Source Based on Fluorotellurite Fiber

Supercontinuum (SC) sources covering near‐infrared and midinfrared region have attracted enormous interest and found significant applications in tissue imaging, sensing, spectroscopy, defense, and environmental monitoring. Herein, an 8.45 W all‐fiber ultraflat SC source with a spectral range of 1.01–4.05 μm using a flat high‐power 1.9–2.7 μm SC fiber source to pump a piece of fluorotellurite fiber is presented. The SC spectrum exhibits a 3 dB bandwidth of 1850 nm, ranging from 1870 to 3720 nm, and a 10 dB bandwidth of 2770 nm, ranging from 1120 to 3890 nm. The measured power stability is 0.19% (root mean square) for 5 h of continuous operation, proving the excellent power stability of the system. To the best of knowledge, the SC spectrum exhibits the widest reported 3 and 10 dB bandwidths for 1–4 μm SC sources.

Stable high-peak-power fiber supercontinuum generation for adaptive femtosecond biophotonics

Stable high-peak-power fiber supercontinuum generation for adaptive femtosecond biophotonics

A hybrid network with DNN and WGAN for supercontinum prediction

In this paper, a Hybrid Network is reported for predicting the output pulse shape parameters of the supercontinuum in optical fibers. The network incorporates the Wasserstein generative adversarial network (WGAN) and the deep neural network (DNN) with a TCN layer. The WGAN augments a limited set of original data, while the designed DNN accurately predicts supercontinuum. The simulation results show the spectra agreement (Agm) of the predictions by individual DNN is 89% and the root mean square error (RMSE) is 0.1092. After retraining with WGAN's extended dataset, the Agm of DNN predictions is improved to 98% and the RMSE is reduced to 0.0513. The input pump power corresponding to the appearance of the fourth soliton peak can be predicted by the retrained DNN. Numerical analysis demonstrates the effectiveness and generalization ability of a Hybrid Network in predicting pulse parameters. The network fits the propagation dynamics in the spectral domain of SC, which provides a promising tool for further research in this field.

Compact and efficient high-power mid-infrared supercontinuum fiber laser source based on a noise-like pulse and germania fiber

Here, we demonstrate a compact and efficient high-power mid-infrared supercontinuum (MIR-SC) laser source based on a tunable noise-like pulse (NLP) fiber laser system and a short section of single-mode germania-core fiber (GCF). The NLP all-polarization-maintaining fiber laser system can deliver the maximum output power of ∼30.6 W and a broadband spectrum (∼1.8-2.7 µm) with a compact single-stage fiber amplifier. By directly pumping only ∼6.5 cm-long GCF with a core diameter of ∼3.5 µm, a MIR-SC (spectral coverage of ∼1.5-3.3 µm) with a maximum power of ∼25.2 W and a power conversion efficiency ∼81.2% is obtained, which represent the highest power and efficiency in any single-mode GCF-based MIR-SCs, to the best of our knowledge. Our study contributes to the high-power MIR-SC laser source with compact all-fiber configuration, and will prompt its practical applications.

CW mode-locked fiber laser by improved all-polarization-maintaining figure-9 cavity at 1064 nm

In order to realize broadband continuous wave (CW) mode locking by figure-9 fiber laser at 1064 nm, we propose an improved all-polarization-maintaining figure-9 cavity structure by adding gain fiber to both the loop and the linear arm in the laser. When the two sections of gain fiber are pumped simultaneously, the CW mode locking regime can be obtained. In this work, noise-like mode-locked pulses are generated with a central wavelength of 1064 nm and a chirped fiber grating (CFBG) is used for dispersion management. The net dispersion of the cavity is about 0.01 ps2 and the output power is 234 mW. The noise-like pulses are validated by autocorrelator, the peak duration on the autocorrelation trace pedestal is about 261 fs, and the pedestal duration is about 103 ps. Numerical simulations are performed on the noise-like pulses, which agree with the experimental results. This study has inspiration for mode-locked lasers with a central wavelength of 1064 nm, and has potential application value in fields such as supercontinuum generation, fiber sensing, laser microfabrication, and laser ablation.

Enhancing conversion efficiency of MgO:PPLN and Rb:PPKTP crystal-based subnanosecond optical parametric generators by utilizing a supercontinuum seed

This paper presents an approach to enhance the conversion efficiency of subnanosecond pulse duration microlaser-pumped optical parametric generators (OPGs) tunable from near- to mid-infrared. The method involves generating a supercontinuum (SC) in the photonic crystal fiber (PCF) and using it to seed the subnanosecond OPG based on the fan-out grating design MgO:PPLN crystal. Since the SC spectrum covered the entire signal wave tuning range (1414–2128 nm), seeding and conversion efficiency improvement of 6%–11% was achieved for all OPG signal wavelengths, and the generation threshold was reduced up to 3 times. Such a method allows for improved energy stability, significantly increases the brightness of the OPG output radiation, and is pivotal in mitigating the risk of MgO:PPLN optical damage. The study also extended the method to successfully seed 532 nm pumped Rb-doped PPKTP crystal-based OPG with the same SC, demonstrating broad applicability and performance improvement across different parametric devices.

Full visible range two-dimensional electronic spectroscopy with high time resolution.

Two-dimensional electronic spectroscopy (2DES) is a powerful method to study coherent and incoherent interactions and dynamics in complex quantum systems by correlating excitation and detection energies in a nonlinear spectroscopy experiment. Such dynamics can be probed with a time resolution limited only by the duration of the employed laser pulses and in a spectral range defined by the pulse spectrum. In the blue spectral range (<500 nm), the generation of sufficiently broadband ultrashort pulses with pulse durations of 10 fs or less has been challenging so far. Here, we present a 2DES setup based on a hollow-core fiber supercontinuum covering the full visible range (400-700 nm). Pulse compression via custom-made chirped mirrors yields a time resolution of <10 fs. The broad spectral coverage, in particular the extension of the pulse spectra into the blue spectral range, unlocks new possibilities for coherent investigations of blue-light absorbing and multichromophoric compounds, as demonstrated by a 2DES measurement of chlorophyll a.

Nonlinear dynamics of relative intensity noise transfer at fiber amplification and supercontinuum generation

Supercontinuum sources via femtosecond pumping in highly nonlinear photonic crystal fibers considerably impact scientific research and industrial applications. Herein, we investigate the complex transfer function of relative intensity noise in a broadband fiber supercontinuum source generated using an ytterbium-doped mode-locked laser. A designed intensity noise was artificially added to the system through the introduction of weak sinusoidal intensity modulation to the seed pulses. Owing to the influence of nonlinear gain dynamics and soliton dynamics during power amplification and spectral broadening, the transfer functions exhibit unique frequency and wavelength dependencies. Systematic measurements indicate that the seed transfer functions exhibit the characteristics of damped high-pass filters and saturate at low Fourier frequencies within the fiber amplifier. Moreover, supercontinuum broadening induces a nonlinear transformation of fluctuations, resulting in considerable amplification and negative correlation within the dispersion wave and soliton self-frequency shift regions. Clarifying the mechanism and bandwidth of this system is imperative to achieving low-noise supercontinuum generation because they provide insights into the nonlinear laser dynamics associated with broadband spectral broadening and noise transformation.

Visible to Mid-IR Supercontinuum Generation in Cascaded PCF-Germanate Fiber Using Femtosecond Yb-Fiber Pump

Broadband supercontinuum (SC) fiber sources covering the mid-IR range have many significant applications, largely due to their compactness, reliability, and ease of use. However, most of the existing SC fiber sources cannot boast of either high reliability or a wide bandwidth. Thus, supercontinuum sources based on silica fibers are robust, but are not capable of generating SC in the mid-IR range. Sources based on soft glasses (tellurite, chalcogenide, etc.) generate broadband SC in the mid-IR range but are not used commercially, due to the poor mechanical and chemical characteristics of such fibers. In this work, we propose a new approach consisting of cascade generation of a supercontinuum sequentially in a silica photonic crystal fiber (PCF) and a germanate fiber. Using a standard ytterbium chirped-pulse amplification (CPA) laser system for pumping, we have demonstrated a supercontinuum in the range of 450–2950 nm in PCF and germanate fiber firmly connected by a standard fusion splicing technique. Further optimization of the cascade pump will make it possible to create a compact and reliable all-fiber SC source from the visible to mid-IR range.

Laser-interfered studies in HgCdTe infrared focal plane array detector by high-repetition-rate mid-infrared supercontinuum fiber laser

Laser-interfered studies in HgCdTe infrared focal plane array detector by high-repetition-rate mid-infrared supercontinuum fiber laser

Performance analysis of photonic crystal fiber structure based on different highly nonlinear materials

Generally, fiber with a large mode area is desired for fiber laser and beam delivery applications. But the use of these fiber types is restricted to linear optical applications due to the lower value of the nonlinear coefficient. This paper investigates a single material-based photonic crystal fiber (PCF) with improved optical characteristics, applicable for linear and nonlinear optics. The light propagation in the structure is explored by applying finite element solver-based COMSOL multiphysics software. Five nonlinear optical materials are utilized as background material to get the optimized material with high performance PCF. Using this PCF, the improved optical properties of PCF such as moderate effective mode area of 115.85 [Formula: see text], chromatic dispersion, confinement loss of 10[Formula: see text] dB/m, the nonlinear coefficient of 543W[Formula: see text]Km[Formula: see text], splicing loss of 2.013 dB, and numerical aperture are numerically analyzed. This single-mode PCF also shows the low bending loss for the bending radius of 7[Formula: see text]mm. The amended PCF structure is found to be suitable for high-power fiber laser, supercontinuum generation, wavelength conversion, and slow-light generation.

All-fiber 2–6 [formula omitted] coherent supercontinuum source based on chalcogenide fibers pumped by an amplified mid-IR soliton laser

We numerically and experimentally investigate an all-fiber configuration of coherent mid-infrared supercontinuum generation in the femtosecond pumping regime. In particular, we demonstrate the advantageous combination of various dispersion-engineered chalcogenide (Ge-Se-Te glass) fibers with a turn-key amplified femtosecond fiber laser delivering 175-fs soliton pulses around 3.4 μm and developed from the erbium-doped fluoride fiber technology. Our results show that compact and coherent octave-spanning fiber supercontinuum sources centered on the 2–5 μm infrared atmospheric window can be obtained with a maximum average power of 50 mW at 25 MHz repetition rate.

Ultra-high birefringence mid-infrared Ge20Sb15Se65 chalcogenide glass photonic crystal fiber with low confinement loss

This study introduces a Ge20Sb15Se65 chalcogenide-glass-based photonic crystal fiber (PCF) with high birefringence and nonlinearity and ultra-low confinement loss, in which two elliptical air holes are added in the core. The propagation properties of the proposed PCF are investigated in mid-infrared range (3.0–5.0 μm) using the finite element method (FEM). Simulation results indicate that optimizing structural parameters can increase the birefringence and nonlinear coefficient to a maximum of 3.16 × 10−1 and 5937 W−1km−1 (in y-polarization mode), respectively, a significantly low confinement loss reach 10−14 dB m−1 at 3.0 μm wavelength, there can obtain one zero dispersion wavelength in the study band, and the designed structure can be fabricated using available technology. The designed PCF will have promising application in mid-infrared fiber fields, optical communication, super-continuum generation, precision, and nonlinear optics.

Benefits of cascaded nonlinear dynamics in hybrid fibers for low-noise supercontinuum generation.

The recent development of fiber supercontinuum (SC) sources with ultra-low noise levels has been instrumental in advancing the state-of-the-art in a wide range of research topics. However, simultaneously satisfying the application demands of maximizing spectral bandwidth and minimizing noise is a major challenge that so far has been addressed with compromise, found by fine-tuning the characteristics of a single nonlinear fiber transforming the injected laser pulses into a broadband SC. In this work, we investigate a hybrid approach that splits the nonlinear dynamics into two discrete fibers optimized for nonlinear temporal compression and spectral broadening, respectively. This introduces new design degrees of freedom, making it possible to select the best fiber for each stage of the SC generation process. With experiments and simulations we study the benefits of this hybrid approach for three common and commercially available highly nonlinear fiber (HNLF) designs, focusing on flatness, bandwidth and relative intensity noise of the generated SC. In our results, hybrid all-normal dispersion (ANDi) HNLF stand out as they combine the broad spectral bandwidths associated with soliton dynamics with extremely low noise and smooth spectra known from normal dispersion nonlinearities. Hybrid ANDi HNLF are a simple and low-cost route for implementing ultra-low noise SC sources and scaling their repetition rate for various applications such as biophotonic imaging, coherent optical communications, or ultrafast photonics.

Two-photon fluorescence imaging using a tunable spectral window based on fiber supercontinuum.

Two-photon excitation fluorescence (TPEF) microscopy has evolved into a versatile tool in biological research. However, the multiplexing capability of TPEF microscopy is limited by the narrow spectral bandwidth of the light source. In this study, we apply a photonic crystal fiber in TPEF microscopy to broaden the excitation source bandwidth. We tuned the spectral window using a spatial light modulator as a programmable diffraction grating that was placed behind a prism pair. In addition, we combined a grating pair to compensate for dispersion to improve the two-photon excitation efficiency. The combination of a broad spectrum and a programmable grating enabled fast spectral window tuning rate on a time scale of tens of milliseconds. We demonstrate the performance of our method by imaging live B16 cells labeled with four emission spectrum overlapped fluorescent proteins.

143.4 W high power combined white supercontinuum source using a (7 × 1) supercontinuum fiber combiner

We demonstrate a 143.4 W high power combined white supercontinuum (SC) source using a (7 × 1) SC fiber combiner. Based on the criteria of adiabatic tapering and brightness conservation, a (7 × 1) SC fiber combiner is designed and theoretically investigated, and the simulated results of the transmission efficiencies of laser at different wavelengths of the combiner verify that the combiner has the ability of combining white SC sources efficiently. Then, the (7 × 1) SC fiber combiner is fabricated, and three white SC fiber laser sources with average power of about 50 W are set up for beam combining experiment. Finally, a 143.4 W high power combined white SC source is achieved with high combining efficiency of 97.4%. and the corresponding combined SC spectrum ranges from 450 nm to 1700 nm, which remains consistent with the overall spectral range of the three SC sources. The experiment result indicates that the (7 × 1) SC fiber combiner is greatly capable of combining high power white SC sources efficiently, thereby increasing the average power of the white SC source significantly. To the best of our knowledge, this is the first demonstration of a fiber combiner for high power white SC sources with such a high combining efficiency.

Kilowatt-Level Supercontinuum Generation in Random Raman Fiber Laser Oscillator With Full-Open Cavity

High-power supercontinuum (SC) sources are important for remote sensing, homeland defense, and scientific research. Despite recent advances in power scaling of the SC generation in optical fibers, the power record of SC fiber laser sources is still much lower than conventional high-power fiber lasers. Here we demonstrate a method for kilowatt-level SC generation based on the random Raman fiber laser (RRFL) with a full-open cavity. Theoretically, a model including cascaded Raman effect, modulation instability, and Rayleigh scattering is established to qualitatively highlight the dynamics of the kilowatt-level SC generation. Experimentally, injecting the amplified ytterbium-doped fiber laser and Raman fiber laser into the RRFL oscillator formed by a piece of long passive fiber, 3-kW-level SC spanning from 925 to 1862 nm is achieved. The experimental results suggest that the full-open-cavity RRFL is a promising approach for kilowatt-level SC generation and the theoretical model demonstrates the importance of Rayleigh backscattering during the SC generation.

A nonlinear ZBLAN-based photonic crystal fiber with ultra-high birefringence and flattened dispersion in short-wavelength infrared region

In this paper, a high nonlinear ZBLAN-based photonic crystal fiber (PCF) with ultra-high birefringence and flattened dispersion is numerically proposed in short-wavelength infrared region based on finite element method. Eight elliptical-hole arrays are arranged surrounding the fiber core to separate x-polarized and y-polarized fundamental modes. The birefringence can reach to an excellent level of 4.46 × 10−2 at wavelength 2.5 µm and interestingly shows a hopping phenomenon as the ellipticity increases from 2.2 to 3.1. In addition, the design also exhibits a single-mode propagation, short beat length (< 0.12 µm), high nonlinear coefficient 131 W−1·km−1, low confinement loss 10−9 dB/m and flattened dispersion with a maximum fluctuation 50 ps·km−1nm−1 in wavelength range from 1.5 µm to 2.5 µm. The effect of the structure parameters (air hole diameter, lattice constant and ellipticity of elliptical holes) on the optical properties is symmetrically investigated. This ZBLAN-based PCF has great potential in the nonlinear applications of fiber laser and supercontinuum generation in infrared region.

Supercontinuum fiber laser-based coherent anti-Stokes Raman scattering microscopy for label-free chemical imaging

Coherent anti-Stokes Raman scattering (CARS) microscopy can resolve the chemical components and distribution of living biological systems in a label-free manner and is favored in several disciplines. Current CARS microscopes typically use bulky, high-performance solid-state lasers, which are expensive and sensitive to environmental changes. With their relatively low cost and environmental sensitivity, supercontinuum fiber (SF) lasers with a small footprint have found increasing use in biomedical applications. Upon these features, in this paper, we homebuilt a low-cost CARS microscope based on a SF laser module (scCARS microscope). This SF laser module is specially customized by adding a time-synchronized seed source channel to the SF laser to form a dual-channel output laser. The performance of the scCARS microscope is evaluated with dimethyl sulfoxide, whose results confirm a spatial resolution of better than 500[Formula: see text]nm and a detection sensitivity of millimolar concentrations. The dual-color imaging capability is further demonstrated by imaging different species of mixed microspheres. We finally explore the potential of our scCARS microscope by mapping lipid droplets in different cancer cells and corneal stromal lenses.