Mid-IR Laser Generating Ultrasound in a Polyetheretherketone Polymer

We demonstrate laser ultrasonic generation in polyetheretherketone(PEEK). A middle infrared ZnGeP2 optical parametric oscillator(ZGP-OPO) pumped by a Q-switched Ho:YAG laser is employed as the ultrasonic excitation source. The ZGP-OPO has a spectral range of 3.2–3.4 μm. At an output wavelength of 3.4 μm, the maximum average output power of ZGP-OPO is 3.05 W with a pulse width of 24.3 ns, corresponding to a peak power of approximately 127.5 kW. The ultrasound is generated by the laser converted from 3.2 to 3.4 μm in the PEEK composite. The maximum ultrasonic signal amplitude in PEEK is 33 mV under the condition of thermoelastic excitation at 3.4 μm. Ablation occurs in the CPRF sample when the energy fluence is over 122.45 m J/cm~2. PEEK has a stronger absorption at 3.4 μm and laser-ultrasound generation is influenced by the wavelength of the laser.     

A 52-mJ Ho：YAG Master Oscillator and Power Amplifier with Kilohertz Pulse Repetition Frequency

We report on a high energy, high repetition rate Ho：YAG master oscillator and power amplifier （MOPA）, res- onantly dual-end-pumped by Tm：YLF lasers at room temperature. At the pulse repetition frequency of i kHz, we demonstrate a maximum energy of 30mJ per pulse with a 28.2ns pulse width in a Ho：YAG oscillator system resonantly double-end-pumped by Tm：YLF lasers. A maximum energy of 52mJ per pulse with a 30.5ns pulse width is achieved in the Ho： YA G amplifier, corresponding to a peak power of approximately 1.7 MW. The output wavelength is at 2090.6nm and 2096.9nm, and a beam quality factor of M2-2.1 is achieved.