Fuzeng Niu

1 GHz repetition rate femtosecond Yb:fiber laser for direct generation of carrier-envelope offset frequency.

We report a mode-locked fiber laser working at a 1 GHz fundamental repetition rate. The laser delivers a 600 mW average power at a pump power of 1800 mW. The pulse spectrum bandwidth was 23 nm to support 64 fs near-transform-limited pulses. An octave-spanning supercontinuum from 590 to 1350 nm was generated in a tapered photonic crystal fiber solely with the mode-locked fiber-laser output, without amplifiers. A 30 dB f(ceo) beat signal was detected via f-to-2f interferometer.

Tapered photonic crystal fiber for simplified Yb:fiber laser frequency comb with low pulse energy and robust f ceo singals

A tapered silica photonic crystal fiber was designed and fabricated to generate more than one octave spanning supercontinuum (from 550 nm to 1400 nm at -30 dB level), by an input pulse of 40 fs 200 pJ directly from an Yb:fiber ring laser. The low pulse energy spectrum broadening are favorable to generate the high contrast f ceo signals with low noise. The f ceo signal with 40 dB signal-to-noise ratio was detected, which helps to build a compact real-world frequency comb.

464 MHz repetition rate erbium doped soliton fiber laser

We demonstrate an Er:fiber ring laser operated at the fundamental repetition rate of 464MHz. The output power is 115mW under the pump power of 1.65W. The pulse width is 123fs.

Transition profile control for broadband visible supercontinuum generation in tapered PCF

Tapered photonic crystal fibers with different transition profiles were designed and fabricated to control the visible dispersive wave generation process, and broadband visible supercontinuum (350-700 nm) was achieved.

In vivo Imaging β-cell Function Reveals Two Waves of β-cell Maturation

The insulin-secreting cells generated from stem cells in vitro are less glucose responsive than primary β-cells. To search for the missing ingredients that are needed for β-cell maturation, we have longitudinally monitored function of every β-cell in Tg (ins:Rcamp1.07) zebrafish embryos with a newly-invented two-photon light-sheet microscope. We have shown that β-cell maturation begins from the islet mantle and propagates to the islet core during the hatching period, coordinated by the islet vascularization. Lower concentration of glucose is optimal to initiate β-cell maturation, while increased glucose delivery to every cell through microcirculation is required for functional boosting of the β-cells. Both the initiation and the boosting of β-cell maturation demands activation of calcineurin/NFAT by glucose. Calcineurin activator combined with glucose promotes mouse neonatal β-cells cultured in vitro to mature to a functional state similar to adult β-cells, suggesting a new strategy for improving stem cell-derived β-like cell function in vitro.

Compressed 6 ps pulse in nonlinear amplification of a Q-switched microchip laser

We present a passively Q-switched Nd:YVO4 crystal microchip laser with a 6 ps pulse width, which is based on SPM-induced spectral broadening and pulse compression. The passive Q-switching is obtained by a semiconductor saturable absorber mirror. The lasers seed source centered at 1064 nm pulses with a duration of 80 ps, at a repetition rate of 600 kHz corresponding to an average output power of 10 mW. After amplification and compression, the pulses were compressed to 6 ps with a maximum pulse energy of 0.5 µJ.

Imaging functional maturation of pancreatic beta-cells and neuronal circuit activity in Zebrafish in vivo using two-photon three-axis digital scanned lightsheet microscopy

Here we have developed a novel large-field high-resolution two-photon digital scanned light-sheet microscopy (2P3A-DSLM) based on ultrafast axial scanning of illumination focal spot with a tunable acoustic gradient (TAG) index device. This new technique provides a sub-micron axial resolution with a large field of view in deep tissues. In vivo imaging with 2P3A-DSLM resolves functional maturation of pancreatic beta cells and neuron circuit activities in live Zebrafish embryos.

4.4 nJ, 114 fs Nd-doped fiber laser pulses at 920nm for in vivo two-photon microscopic imaging

We optimized pre-chirp in an Nd-doped fiber amplifier to achieve high-quality femtosecond 920 nm pulses. The in vivo zebrafish imaging proves the laser amplifier an ideal source in two-photon microscopic imaging.

Green-enhanced super-continuum generation in a tapered photonic crystal fiber for efficient fceo detection

We report the green-enhanced (530 nm) super-continuum generation in a tapered photonic crystal fiber by 280 pJ pulses from a mode-locked Yb:fiber laser. This system offers a technique for efficient fceo beating signal detection.

Integrated Yb:fiber laser frequency comb with three photonic crystal fibers

We demonstrated a near all-fiber femtosecond Yb:laser frequency comb incorporated with three different photonic crystal fibers. The comb removes most of free-space components so that it is more compact and stable.