CO2-laser-ablation-assisted fabrication of signal-pump combiners with chirally coupled core fibers for co- and counter-pumped all-fiber amplifiers.

We report on the development of a side-fused signal-pump combiner with an integrated feed-through 34/250-µm chirally coupled core fiber. The manufacturing process involves a novel rotationally symmetrical cladding restructuring using a CO2-laser beam. The signal-pump combiner exhibits the pump-to-signal fiber coupling efficiency of 90%, signal-to-pump isolation of 30 dB, and is high-power tested at a pump input power of >500 W. Additionally, a signal feed-through loss of 0.23 dB is measured and the S2-method is used to confirm non-degradation of the spatial modes. The side-fused combiner technique has the advantage of an uninterrupted signal core and can be used in co- and counter-pumped configurations.

On the measurement of fundamental mode bend loss in large-mode-area optical fibers.

The measurement of fundamental mode bend loss is thoroughly studied in large-mode-area few-mode optical fibers. The influencing factors, including spectral properties of the light source, modal power content and cladding light, are experimentally investigated. Monte Carlo simulations are performed to help in understanding and illustrating the distribution of the variations. Practical guidelines and an example setup are provided for precise and accurate measurements.

Multi-gigahertz picosecond optical parametric oscillator pumped by 80-MHz Yb-fiber laser.

We report a multi-gigahertz (GHz) repetition-rate picosecond optical parametric oscillator (OPO) based on MgO:PPLN, synchronously pumped by a Yb-fiber laser operating at 80 MHz, where the multiplication of repetition frequency is achieved using fractional increment in the OPO cavity length. Using this simple technique, we achieve OPO operation up to the 88th harmonic of the pump laser frequency, corresponding to a repetition rate as high as 7 GHz. Deploying a 5% output coupler, we are able to extract up to 960 mW of average signal power at the fundamental with 600 mW at the 88th harmonic (7 GHz), using a pump power of 5.6 W. The measured relative standard deviations of the fundamental and fifth harmonic signal power are recorded to be 1.6% and 3.5%, respectively, while the fundamental signal pulse duration is measured to be 18.4 ps.

Thermal tuning of laser pulse parameters in passively Q-switched Nd:YAG lasers.

Modifying the output pulses of a passively Q-switched Nd:YAG laser, operating at 1064 nm, was realized by heating the laser crystal. With the demonstrated laser setups, a 100 K temperature rise led to a more than 50% increase in the pulse energy and a more than 10% decrease in the pulse length. This method offers an effective way to tune the output of the laser without mechanical adjustment or a change of components.