Visible continuum pulses based on enhanced dispersive wave generation for endogenous fluorescence imaging

Soliton and dispersive wave generation with third-order dispersion and temporal boundary

We investigate the pulse evolution and energy conservation condition at the temporal boundary under third-order dispersion. When the fundamental soliton crosses the temporal boundary and forms two reflected pulses and one transmitted pulse, the power of the transmitted pulse first increases and then decreases as the incident spectrum shifts toward the blue side. If the transmitted spectrum lies in the anomalous group-velocity dispersion region, second-order soliton is formed and dispersive wave is radiated. We present a modified phase-matching condition to predict the resonance frequencies. The predicted results are in good agreement with the results obtained by numerically solving the nonlinear Schrödinger equation.

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.

Modified genetic algorithm for high-efficiency dispersive waves emission at 3 µm

Mid-infrared dispersive waves generated from supercontinuum generation are of great significance for gas sensing, environmental monitoring, and molecular spectroscopy. But the conversion efficiency of mid-infrared dispersive waves is degraded at longer wavelengths, which limits the application of mid-infrared dispersive waves. Here, we present a genetic algorithm (GA) which is modified by using a simulated binary crossover method and non-uniform mutation process. The modified genetic algorithm (MGA) optimizes the central wavelength, peak power and time duration of the pump to generate high-efficiency dispersive waves at around 3 µm. The conversion efficiency of mid-infrared dispersive waves is increased from 1.5% to 2.29%. These results are useful for gas sensing and environmental monitoring.

Multiplex-multiphoton microscopy and computational strategy for biomedical imaging

We demonstrate the benefit of a novel laser strategy in multiphoton microscopy (MPM). The cheap, simple, and turn-key supercontinuum laser system with its spectral shaping module, constitutes an ideal approach for the one-shot microscopic imaging of many fluorophores without modification of the excitation parameters: central wavelength, spectral bandwidth, and average power. The polyvalence of the resulting multiplex-multiphoton microscopy (M-MPM) device is illustrated by images of many biomedical models from several origins (biological, medical, or vegetal), generated while keeping constant the spectral parameters of excitation. The resolution of the M-MPM device is quantified by a procedure of point-spread-function (PSF) assessment led by an original, robust, and reliable computational approach FIGARO. The estimated values for the PSF width for our M-MPM system are shown to be comparable to standard values found in optical microscopy. The simplification of the excitation system constitutes a significant instrumental progress in biomedical MPM, paving the way to the imaging of many fluorophores with a single shot of excitation without any modification of the lighting device. RESEARCH HIGHLIGHTS: A new solution of multiplex-multiphoton microscopy device is shown, resting on a supercontinuum laser. The one-shot excitation device has imaged biomedical and vegetal models. Our original computational strategy measures usual microscopy resolution.