We report on a commercial laser system based on a Yb fiber oscillator with cross-filter mode lock (CFML) mechanism that is integrated with a programmable pulse shaper. The laser is self-starting and stable in a wide temperature range, 15- 50°C, resilient to vibrations and shock. It can serve as a seed for high-power femto- and pico- second systems or be implemented as a standalone unit, as illustrated in this paper. The master oscillator is outputting strongly chirped pulses, with the spectrum centered at 1030 nm and having the full bandwidth of up to 90 nm. It operates at 11 MHz repetition rate, with the pulse energy of at least 10 nJ at the output. When equipped with an additional power amplification module, the oscillator yields the same spectral output and repetition rate, but the pulse energy can be increased up to 400 nJ. The laser output is fully coherent, and pulses are compressible down to the transform limit (TL). For demanding femtosecond applications, the laser system is being configured with a static grating compressor and a compact spectral phase shaper. The pulse shaper utilizes a liquid-crystal spatial light modulator for active phase control which enables high-finesse pulse compression as well as arbitrary manipulation of the pulse waveform. With the use of the pulse shaper, the oscillator output is compressed down to 57 fs, which is within 7% from the TL pulse duration, 53 fs, calculated from the experimental laser spectrum.
We present an environmentally stable Yb ultrafast ring oscillator utilizing a new method of passive mode-locking. The laser is using all-fiber architecture which makes it insensitive to environmental factors, like temperature, humidity, vibrations, and shocks. The new method of mode-locking is utilizing crossed bandpass transmittance filters in ring architecture to discriminate against CW lasing. Broadband pulse evolves from cavity noise under amplification, after passing each filter, causing strong spectral broadening. The laser is self-starting. It generates transform limited spectrally flat pulses of 1 – 50 nm width at 6 – 15 MHz repetition rate and pulse energy 0.2 – 15 nJ at 1010 – 1080 nm CWL.
We report an industrial grade picosecond and femtosecond pulse Yb fiber lasers with >100 μJ pulse energy and hundreds of Watts of average power for improved laser machining speed of sapphire and glass. This highly efficient laser offers >25% wall plug efficiency within a compact 3U rack-mountable configuration plus a long >2m fiber delivery cable. Reconfigurable features such as controllable repetition rate, fine pulse duration control, burst mode operation and adjustable pulse energy permit the customer to tailor the laser to their application.
Vibrational Sum Frequency Generation (VSFG) on gold and silver nanoparticles capped with alkanethiols is studied.
Aggregation of nanoparticles is characterized using TEM and SEM methods. VSFG process is enhanced due to the
coupling of surface plasmon induced by the visible radiation in gold nanoparticle with vibrational transition of
chemisorbed alkanethiol excited by the infrared beam. VSFG spectra show methyl and methylene stretch transitions. The
ratio of their intensities varies with changing size of the particles and length of alkane chain. Dramatic change in
intensity ratio and overall enhancement of VSFG intensity is observed when aggregation of gold nanoparticles occurs.
For the first time we report the mode-specific SFG enhancement, namely, the methyl antisymmetric stretch gains the
highest intensity. One possible explanation is that enhancement is caused by the change in SFG selection rules due to the
effect of locally inhomogeneous electric field of plasmon. VSFG response from aggregates is significantly depolarized
in comparison with response from non-interacting particles. This can be due to the depolarization of plasmon induced in
aggregates of metallic nanoparticles. Divergence of VSFG beam from aggregates is stronger than that of the beam from non-interacting particles. This can be attributed to the incoherent nonlinear scattering in aggregates due to depolarization of surface plasmon. Potential applications of SFG nanoprobes for imaging, IR radiation conversion, and opto-electronic integrated circuits are discussed.