Superresolved far-field microscopy has emerged as a powerful tool for investigating the structure of objects with resolution well below the diffraction limit of light. Nearly all superresolution imaging techniques reported to date rely on real energy states of fluorescent molecules to circumvent the diffraction limit, preventing superresolved imaging with contrast mechanisms that occur via virtual energy states, including harmonic generation (HG). We report a superresolution technique based on spatial frequencymodulated imaging (SPIFI) that permits superresolved nonlinear microscopy with any contrast mechanism and with single-pixel detection. We show multimodal superresolved images with twophoton excited fluorescence (TPEF) and second-harmonic generation (SHG) from biological and inorganic media. Multiphoton SPIFI (MP-SPIFI) provides spatial resolution up to 2η below the diffraction limit, where η is the highest power of the nonlinear intensity response. MP-SPIFI can be used to provide enhanced resolution in optically thin media and may provide a solution for superresolved imaging deep in scattering media.superresolution | harmonic generation | multiphoton microscopy
We demonstrate the operation of a gain-saturated table-top soft x-ray laser at 100 Hz repetition rate. The laser generates an average power of 0.15 mW at λ=18.9 nm, the highest laser power reported to date from a sub-20-nm wavelength compact source. Picosecond laser pulses of 1.5 μJ energy were produced at λ=18.9 nm by amplification in a Mo plasma created by tailoring the temporal intensity profile of single pump pulses with 1 J energy produced by a diode-pumped chirped pulse amplification Yb:YAG laser. Lasing was also obtained in the 13.9 nm line of Ni-like Ag. These results increase by an order of magnitude the repetition rate of plasma-based soft x-ray lasers opening the path to milliwatt average power table-top lasers at sub-20 nm wavelengths.
Efficient excitation of dense plasma columns at 100-Hz repetition rate using a tailored pump pulse profile produced a tabletop soft-x-ray laser average power of 0.1 mW at λ = 13.9 nm and 20 μW at λ = 11.9 nm from transitions of Ni-like Ag and Ni-like Sn, respectively. Lasing on several other transitions with wavelengths between 10.9 and 14.7 nm was also obtained using 0.9-J pump pulses of 5-ps duration from a compact diode-pumped chirped pulse amplification Yb:YAG laser. Hydrodynamic and atomic plasma simulations show that the pump pulse profile, consisting of a nanosecond ramp followed by two peaks of picosecond duration, creates a plasma with an increased density of Ni-like ions at the time of peak temperature that results in a larger gain coefficient over a temporally and spatially enlarged space leading to a threefold increase in the soft-x-ray laser output pulse energy. The high average power of these compact soft-x-ray lasers will enable applications requiring high photon flux. These results open the path to milliwatt-average-power tabletop soft-x-ray lasers.
SOLID STATE DIODE-PUMPED SHORT PULSE LASERIn this work I present an all laser diode pumped chirped pulse amplification laser system that is capable of producing 100 mJ laser pulses at 100 Hz repetition rate with durations of under 5 ps. The primary focus of this work consists of the development of two amplification stages that boost the temporally stretched pulses from a few hundred picoJoules to more than 100 mJ. The first amplifier is a Yb:YAG based regenerative amplifier operated at room temperature, which amplifies the pulses by a factor of about 10 6 . The second stage is a multi-pass, Yb:YAG based amplifier, which is operated at cryogenic temperatures, and further amplifies the pulses by a factor of about 100. This is the first time a combination of room temperature and cryogenically cooled Yb:YAG amplifiers has been demonstrated. The room temperature pre-amplifier maintains more bandwidth than in the cryogenic case for increased compressibility. The cryogenic cooling of the power amplifier allows for increased heat dissipation and decreased saturation intensity for efficient operation. The optical efficiency of this amplifier is higher than that of other diode-pumped systems of comparable energy.ii
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