High-power ytterbium-doped fibre master-oscillator power-amplifier at 1018 nm

A high-power master-oscillator power-amplifier (MOPA) at 1018 nm employing ytterbium (Yb)-doped fibres as a gain medium is reported. Utilizing a diffraction grating as a reflector, we could successfully suppress the influence of the broadband amplified spontaneous emission on the master-oscillator or the power-amplifier, resulting in stable amplification of the laser signal at 1018 nm. Based on a simple theoretical simulation on gain spectra and experimental investigation on parasitic lasing thresholds, the Yb fibre MOPA constructed in-house yielded 220 W of output at 1018 nm with a beam propagation factor (M2) of 1.1. The prospects for further power scaling are considered.

16.3 W Peak-Power Pulsed All-Diode Laser Based Multi-Wavelength Master-Oscillator Power-Amplifier System at 964 nm

An all-diode laser-based master oscillator power amplifier (MOPA) configuration for the generation of ns-pulses with high peak power, stable wavelength and small spectral line width is presented. The MOPA emits alternating at two wavelengths in the spectral range between 964 nm and 968 nm, suitable for the detection of water vapor by absorption spectroscopy. The monolithic master oscillator (MO) consists of two slightly detuned distributed feedback laser branches, whose emission is combined in a Y-coupler. The two emission wavelengths can be adjusted by varying the current or temperature to an absorption line and to a non-absorbing region. The power amplifier (PA) consists of a ridge-waveguide (RW) section and a tapered section, monolithically integrated within one chip. The RW section of the PA acts as an optical gate and converts the continuous wave input beam emitted by the MO into a sequence of short optical pulses, which are subsequently amplified by the tapered section to boost the output power. For a pulse width of 8 ns, a peak power of 16.3 W and a side mode suppression ratio of more than 37 dB are achieved at a repetition rate of 25 kHz. The measured spectral width of 10 pm, i.e., 0.1 cm−1, is limited by the resolution of the optical spectrum analyzer. The generated pulses emitting alternating at two wavelengths can be utilized in a differential absorption light detection and ranging system.