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Greatly improving the energy of a single mode-locked pulse while ensuring the acquisition of the width of short pulses will contribute to the application of mode-locked pulse in basic research, such as precision machining. This report has investigated a Q-switched and mode-locked (QML) erbium doped ring fiber laser based on the nonlinear polarization rotation (NPR) technology and a mechanical Q-switched device. Without the working of the mechanical Q-switched device, the fiber laser exported the continuous-wave mode-locked (CWML) pulse, with a width of 212.5 ps, and a repetition frequency of 81.97 MHz. For the CWML operation, the maximum output average power is 25.7 mW, and the energy is only 0.31 nJ. For the QML operation, 18.03 mW average power is achieved at the Q-switching frequency of 100 Hz. The energy of the QML pulse is increased by over 1100 times to 360.6 nJ. The width of the QML pulse is 203.1 ps measured by an autocorrelation curve, with the time-band product (TBP) being 0.598. The power instability is 0.5% (RMS) and 0.7% (RMS), respectively, for CWML and QML operation within 120 min. Furthermore, the spectral signal-to-noise ratio is about 60 dB. For the QML operation, the power instability is 0.48% (RMS) within 60 s and 0.37% (RMS) within 10 s. After frequency stabilization, the frequency fluctuation is ±100 Hz in the long-term of 1200 s, with the frequency stability (FS) calculated to be 2.44 × 10−6. It indicates that the QML fiber laser has good power stability and frequency stability.

To study the characteristics of material removal with high power ultra-short pulsed lasers, a 300 W picosecond laser was used to make microgrooves in cooper and steel. The effects of laser power, laser frequency, scanning layers, and scanning velocity on the width and depth of the grooves were analyzed. The material removal rate of picosecond laser was compared with that of a 10 W nanosecond laser. The results showed that high power high frequency ultra-short pulsed lasers have good potential in high speed micromachining. Evidence showed that ps laser machining could be more efficient than nanosecond machining. There are issues to be solved to make high power ultra-short pulsed lasers the dominating process for high speed micromachining.

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The so-called organic Rankine cycle (ORC) is an effective technology allowing heat recovery from lower temperature sources. In the present study, to improve its thermal efficiency, a preheated ejector using exhaust steam coming from the expander is integrated in the cycle (EPORC). Considering net power output, pump power, and thermal efficiency, the proposed system is compared with the basic ORC. The influence of the ejector ratio (ER) of the preheated ejector on the system performances is also investigated. Results show that the net power output of the EPORC is higher than that of the basic ORC due to the decreasing pump power. Under given working conditions, the average thermal efficiency of EPORC is 29% higher than that of ORC. The ER has a great impact on the performance of EPORC by adjusting the working fluid fed to the pump, leading to significant variations of the pump work Moreover, the ER has a remarkable effect on the working fluid temperature lift (TL) at the evaporator inlet, thus reducing the evaporator heat load. According to the results, the thermal efficiency of EPORC increases by 30%, when the ER increases from 0.05 to 0.4.