YVO4 Picosecond Research Articles

Tunable Near and Mid-Infrared (1.3–5 µm) Picosecond Pulsed Optical Vortex Parametric Oscillator

In this paper, we present a picosecond pulsed, synchronously pumped optical parametric oscillator producing vortex beam output with tunable wavelengths in the near- to mid-infrared range. The system utilizes a Nd:YVO4 picosecond pulsed solid-state laser emitting at a wavelength of 1.064 µm to pump a Z-shaped, singly resonant OPO which contains a MgO:PPLN crystal with a fan-shaped grating. The wavelength tuning characteristics of the OPO output are examined both as a function of the MgO:PPLN grating period and crystal temperature. The orbital angular momentum of the pump field can be selectively transferred to either the signal or idler fields by appropriately adjusting the location of the MgO:PPLN crystal within the OPO cavity. The maximum output power of the signal and idler vortex fields are 5.12 W and 3.46 W, respectively, for an incident pump power of 19 W.

Near to Mid-Infrared (1.3–5 μm) Widely Tunable, High Power Picosecond Pulsed Laser

We present a high-power, widely tunable, synchronously pumped picosecond pulsed optical parametric oscillator (OPO) generating emissions in the near to mid-infrared wavelength ranges. The OPO is pumped using a Nd:YVO4 picosecond pulsed laser and utilizes a fan-shaped, multi-grating MgO doped PPLN crystal (MgO:PPLN). The system generates near to mid-infrared output across the wavelength range 1.3–5 µm, with a high overall conversion efficiency of 75.15%.

High Stability Industrial-Grade Nd: YVO4 Picosecond Laser Amplifier With High Average Output Power

We demonstrate a high-power Nd: YVO4 picosecond laser amplifier that is capable of generating 51.5 W of average output power at a wavelength of 1,064 nm, with a repetition rate of 70 MHz and a pulse duration of 8.5 ps. This system encompasses three stages of laser diode end-pumped Nd: YVO4 amplification including two double-pass amplifiers and a single-pass amplifier. Laser output with near-diffraction-limited beam quality (M2 < 1.1) was maintained throughout the entire power scaling range of the laser. The system exhibited very high output power stability with a root-mean-square amplitude fluctuation of less than 0.2% over a period of 15 h of continuous operation.

Fiber-solid hybrid end-pumped Nd:YVO4 picosecond amplifier with high beam quality

In recent years, high-brightness picosecond lasers have been widely used in high-end precision processing, spectroscopy and high harmonic generation. To obtain higher power and excellent beam quality, it is an ideal solution to add a high-gain amplifier to the back end of the high-stability picosecond fiber or solid seed. In this article, a fiber-solid hybrid end-pumped Nd:YVO4 picosecond laser system with high beam quality is demonstrated. The influence of the self-developed picosecond fiber seed output characteristics on solid amplifiers has been studied in detail, including the energy, repetition rate and spectrum. After two-stage traveling wave amplifiers, the maximum 155 μJ single pulse energy is obtained with 20 kHz repetition rate, and the corresponding peak power reaches 14.9 MW with 10.4 ps pulse duration. Meanwhile, the beam quality factors under the maximum 18.4 W average power are measured to be M x 2 = 1.27 and M y 2 = 1.25, respectively.

Generation of 172 fs pulse from a Nd: YVO4 picosecond laser by using multi-pass-cell technique

The device of multi-pass-cell (MPC) could broaden the spectra of ultrafast laser pulses based on the self-phase-modulation (SPM) effect, which is composed of two concave mirrors and nonlinear mediums. In this paper, the pulse duration of 172 fs is compressed from a 11.3 ps Nd: YVO4 regenerative amplifier at the repetition rate of 1 kHz by using two stages of MPC systems. The pulse duration is shortened by a factor of 66, and the pulse energy of 117 μJ is obtained with a total efficiency of 51%. With high average power Nd-doped laser systems at 10 ps level, this method has the potential to generate high power femtosecond lasers with high efficiency, compact configuration, and low cost.

Measuring and Optimizing MG-63 Osteosarcoma Osseointegration and Proliferation on Laser Ablated Medical-Grade Titanium

We will modify pieces of Ti64AlV medical-grade titanium, commonly used in dental and orthopedic industries, through laser ablation, to optimize osseointegration, the growth of bone that anchors a surgical implant. Such conditions would indicate that this modification of the titanium will lead to a shorter time for recovery and higher bone to implant contact rate for titanium implants. The MG-63 cell line, a type of osteosarcoma, was chosen to measure cell adhesion to a surface that is altered using the Nd:YVO4 picosecond pulsed laser.

Generation of 601 fs pulse from an 8 kHz Nd:YVO4 picosecond laser by multi-pass-cell spectral broadening

We demonstrate nonlinear pulse compression of an 8 kHz Nd:YVO4 picosecond laser using the multi-pass-cell (MPC) technique with fused silica as the nonlinear medium. The pulse duration is compressed from 12.5 ps to 601 fs, corresponding to a pulse shortening factor of 20.8. The output pulse energy is 154 μJ with an efficiency of 74.5%. To the best of our knowledge, this is the highest pulse compression ratio achieved in a single-stage MPC with bulk material as the nonlinear medium. The laser power stability and the beam quality (M2) before and after the MPC are also experimentally studied. Both the laser power stability and the beam quality are barely deteriorated by the MPC device.

The influence of picosecond laser generated periodic structures on bacterial behaviour

The formation of a biofilm is preceded by bacterial retention and proliferation on a surface. Biofilm development on surfaces can cause numerous issues in terms of fouling and bacterial transmission and contamination. The design and fabrication of surfaces that prevent bacterial retention and biofilm formation may provide a potential solution to reduce bacterial fouling of surfaces. An EdgeWave, Nd:YVO4 picosecond laser was used to generate two periodic surface topographies on 316L stainless steel surfaces with and without fluoroalkylsilane (FAS) treatment. These were characterised using Optical Laser Microscopy (OLM), Scanning Electron Microscopy (SEM), contact angle measurements, and Energy Dispersive X-ray Spectroscopy (EDX). The surface wettability and retention of Escherichia coli bacteria on the laser generated surfaces were analysed over one month. Without chemical treatment, and with increasing the time to one month, the results showed that the wettability of laser treated surfaces was decreased as was subsequent bacterial retention. However, the control surface recorded the lowest number of adhered bacteria. After reducing the surface tension, the number of bacteria retention was decreased on all surfaces and one of laser generated surfaces which presented higher contact angle and lower surface tension components (CA = 132°, ΔGiwi = −85.26, γs = 13.81, γsLW = 13.37, and γs− = 0.13) recorded the minimal number of bacteria retention. The results showed that reducing the surface tension played an important role which reduced bacterial fouling.

High gain fiber-solid hybrid double-passing end-pumped Nd:YVO4 picosecond amplifier with high beam quality**Project supported by the National Natural Science Foundation of China (Grant Nos. 61675009 and 61325021) and Key Program of Beijing Municipal Natural Science Foundation, China (Grant No. KZ201910005006).

We propose a fiber-solid hybrid system which consists of a semiconductor saturable absorber mirror (SESAM) mode-locked fiber seed with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz, a two-level fiber pre-amplifier and a double-passing end-pumped Nd:YVO4 amplifier. In the solid-state amplifier, to enhance the gain and the extraction efficiency, a specially designed structure in which the seed light passes through the gain medium four times and makes full use of population inversion is used as the double-passing amplifier. Besides, the beam filling factor (the ratio of the seed light diameter to the pump light diameter) and the thermal lens effect of the double-passing amplifier are considered and its optical-to-optical conversion efficiency is further improved. To preserve the beam quality of the double-passing amplifier, a new method of spherical-aberration self-compensation based on the principles of geometrical optics is used and discussed. Our system achieves a maximum average power of 9.5 W at the pump power of 28 W, corresponding to an optical-to-optical efficiency of 27%. And the beam quality factor M2 reaches 1.3 at the maximum output power.

500-kHz Level High Energy Double-Pass Nd:YVO4 Picosecond Amplifier with Optic–Optic Efficiency of 51%

We have demonstrated a high pulse energy and high optic–optic efficiency double-pass picosecond (ps) master oscillator power amplifier system of 1064 nm at a pulse repetition rate of 500 kHz. A 500 kHz, 7.68 μJ picosecond laser is used as the seed laser. Through one stage double-pass traveling-wave amplifier, a maximum output power of 16.19 W at a pump power of 31.7 W is generated with the optic–optic efficiency of 51.07%. The output pulse duration is 17.6 ps, corresponding to the pulse energy of 32.38 μJ. The beam quality factor M 2 were measured to be 1.28 and 1.17 along the x, y axis direction, respectively.

A high-energy 1064-nm picosecond master oscillator laser with an optic-optic efficiency of 38%

A high-energy high optic-optic efficiency 808-nm diode-end-pumped 1064-nm Nd:YVO4 picosecond master oscillator laser was demonstrated, and a 3×3×7 mm Nd:YVO4 crystal with a doped concentration of 0.5% was adopted. A maximum output power of 3.39 W was obtained with a pulse width of 16.3 ps and a repetition rate of 29.36 MHz under a pump power of 8.92 W, corresponding to an optic-optic efficiency of 38.0%. Compared to the previously reported picosecond master oscillator solid-state lasers, the optic-optic conversion efficiency of 38% is in the leading level among the reported lasers.

Cavity design peculiarities and influence of SESAM characteristics on output performances of a Nd:YVO4 mode locked laser oscillator

In this work we report on the output performances of a Nd:YVO4 picosecond (ps) laser oscillator that was passively modulated by different semiconductor saturable absorber mirrors (SESAMs). The laser emission characteristics are given for SESAM used in Z-type and W-type cavities under similar pumping conditions. Q-switch mode-locking (QML) regime was obtained in the Z-type resonator whereas the W-type oscillator enabled stable mode-locking (ML) operation. For the W-type cavity ML performances are reported for two SESAMs with distinct parameters. Thus the use of a SESAM with 10 ps long recovery time allowed ML operation with pulses of 11.1 nJ energy and 15 ps duration (0.74 kW peak power) at 158 MHz repetition rate; the average power at 1.06 μm was 1.75 W for 5.17 W pump power at 809 nm. Employing a second SESAM with 0.5 ps short recovery time, the Nd:YVO4 laser yielded pulses with increased 13.4 nJ pulse energy and shorter, 12.5 ps, duration (1.1 kW peak power) at 158 MHz repetition rate, corresponding to 2.11 W average power; the pump power was 5.09 W. The results highlight the significant role of the SESAM parameters as well as of the implemented cavity design for the construction of a ps laser source of high performance.

Experimental study on the picosecond pulsed laser cutting of carbon fiber-reinforced plastics

An experimental investigation of carbon fiber-reinforced plastics cutting with an Nd:YVO4 picosecond pulsed system was presented. One-factor experimental design was used in order to explain the influence of cutting parameters including laser power, hatch distance and cutting speed on the pulsed laser–material interaction. The process parameters were optimized by using central composite design of response surface methodology. The results in kerf width, taper angle, material removal rate, and heat-affected zones were discussed through the micrographs observed with optical microscope. Specimens were cut with three different tools: picosecond pulsed laser, nanosecond pulsed laser, and conventional cutting, and the tensile strength and bending strength tests were conducted. Furthermore, the effect of the heat-affected zones on the static strength was also analyzed.

Investigation of Carbon Fiber Reinforced Plastics Machining Using 355 nm Picosecond Pulsed Laser

Carbon fiber reinforced plastics (CFRP) has been widely used in the aircraft industry and automobile industry owing to its superior properties. In this paper, a Nd:YVO4 picosecond pulsed system emitting at 355 nm has been used for CFRP machining experiments to determine optimum milling conditions. Milling parameters including laser power, milling speed and hatch distance were optimized by using box-behnken design of response surface methodology (RSM). Material removal rate was influenced by laser beam overlap ratio which affects mechanical denudation. The results in heat affected zones (HAZ) and milling quality were discussed through the machined surface observed with scanning electron microscope. A re-focusing technique based on the experiment with different focal planes was proposed and milling mechanism was also analyzed in details.

Non-Pulse-Leakage 100-kHz Level, High Beam Quality Industrial Grade Nd:YVO4 Picosecond Amplifier

A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2O4 (BBO) crystal Pockels cells in both the pulse picker and regenerative amplifier, the seed pulse leakage of the output is suppressed effectively with an adjustable repetition rate from 200 to 500 kHz. Through one stage traveling-wave amplifier, a maximum output power of 24.5 W is generated corresponding to the injected regenerative amplified power of 9.73 W at 500 kHz. The output pulse duration is 16.9 ps, and the beam quality factor M2 is measured to be 1.25 with near-field roundness higher than 99% at the full output power.

Generation of picosecond vortex beam in a self-mode-locked Nd:YVO4 laser

In this paper, a self-mode-locked Nd:YVO4 picosecond vortex laser is demonstrated, which can operate on the different Laguerre-Gaussian (LG) modes at 1 064 nm. A π/2 mode converter is utilized to realize the picosecond vortex laser with LG mode transformed from the high-order Hermite-Gaussian (HG) mode. For the proposed laser, the mode-locked pulse repetition rate is 1.81 GHz. The average output powers of LG12 mode and LG02 mode are 1.241 W and 1.27 W, respectively, and their slope efficiencies are 23.2% and 24%, respectively.

Tunable terahertz generation in the picosecond regime from the stimulated polariton scattering in a LiNbO3 crystal.

We demonstrate narrowband tunable terahertz generation from a picosecond LiNbO3 polariton laser, pumped by a CW mode-locked Nd:YVO4 picosecond laser. We generated up to 5.4 μW of terahertz output in untuned mode. We tuned the terahertz output, using etalons in the cavity, from 0.51 to 2.12 THz. Terahertz output powers of 3.7 μW and 2.4 μW were achieved at terahertz frequencies of 1.6 THz and 0.9 THz, respectively.

Optical Fiber Pumped High Repetition Rate and High Power Nd:YVO4 Picosecond Regenerative Amplifier

We report a stable optical fiber pumped Nd:YVO4 all solid state regenerative amplifier with all fiber picosecond laser as seed source. 888 nm Yb optical fiber lasers was chosen as pump source to reduce quantum defect for improved thermal performance. At the repetition rate of 99.6 kHz, maximum power of 19.63 W with 36 ps pulse duration were achieved when seeded by a 150 mW picosecond oscillator. The wavelength delivered was 1064.07 nm with spectral width of 0.14 nm.

Surface Texturing of Drill Bits for Adhesion Reduction and Tool Life Enhancement

Properly designed micro-scale surface textures can have positive impact on adhesion reduction and lubrication enhancement, which can lead to lower friction and improved performance of a contact interface. The present study aims to utilize this function of textures to reduce the adhesion between a drill and a workpiece. In this study, rectangular surface textures were generated on the margins of drill bits using a diode-pumped Nd:YVO4 picosecond laser with a wavelength of 532 nm. Two designs were created in which the textures covered approximately 10 and 20 % of the margin surface area. Textured drills were tested by drilling a series of holes in a titanium plate while recording cutting forces, and the results were compared with the performance of baseline samples. Thermographic heat profiles and visual inspections of the drills were taken at increments of 5 and 10–15 holes, respectively. The comparison demonstrated an encouraging improvement in drill bit life as judged by the number of holes drilled before failure. Textured drills were found to reduce adhesion of titanium chips on the drill margins. This work has demonstrated the potential of texturing to significantly improve the lifetime of drill bits and similar cutting tools.

Compact high-power mode-locked Nd:YVO4 picosecond laser using multiple-pass cavity

A stable self-starting mode-locked Nd:YVO4 laser with a Herriott-type multiple-pass cavity (MPC) operating at 1 064 nm is demonstrated. An in-band 880-nm laser diode is used as an end-pump and a semiconductor saturable absorber mirror (SESAM) is used for passive mode locking (ML) and providing pulse durations of 14 ps. At a pump power of 26.4 W, the maximum average output power is as high as 10.5 W at a repetition rate of 22 MHz, which corresponds to a single pulse energy of 0.48 \mu J. Optical-tooptical conversion efficiency is as high as 39.8% at the maximum output power with a slope efficiency of 55.2%.