YVO4 Picosecond Laser Research Articles

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.

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.

Simulation and experimental results of a high-gain two-stage and double-pass off-axis Nd:YVO4 picosecond laser amplifier.

A high-gain two-stage double-pass off-axis Nd:YVO4 picosecond laser amplifier has been developed. The comprehensive influence of crystal doping concentration and pump beam quality on the small-signal gain of the Nd:YVO4 amplifier is theoretically analyzed with a model developed by considering energy transfer upconversion and pump light absorption saturation effect. The thermal effect of Nd:YVO4 crystal with different doping concentrations, undoped end cap lengths, and pump beam quality is investigated as well. Based on the theoretical analysis, a high-gain two-stage and double-pass off-axis Nd:YVO4 amplifier based on picosecond fiber seed source is realized by choosing long-composite low-doping Nd:YVO4 crystal and with high brightness laser diode pumping, delivering a gain of 28 dB and an output pulse energy of 67.5 µJ at a repetition rate of 200 kHz.

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.

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.

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%.

Supercontinuum Generation with Output Power of 1.7 W Pumped by a Picosecond Laser Pulse

By using a photonic crystal fiber, a supercontinuum source with output power up to 1.7W, pumped by a passively mode-locked diode-pumped Nd:YVO4 picosecond laser is obtained. A spectral width of the supercontinuum is 1700 nm (500–2200 nm) with the 5 dB spectral width approximately 1000 nm (1200–2200 nm). This high power wide band supercontinuum source meets the demand of many applications such as optical coherence tomography, frequency metrology and wavelength-division-multiplexing systems. The evolution of the supercontinuum with the increasing pump power is presented and analyzed.

Single-passed passively mode-locked Nd:YVO4 picosecond laser with SESAM

We report on the LD-pumped passively mode-locked solid-state laser with SESAM (semiconductor saturable absorber mirror), in which the output beam is single passed through a flat mirror. The CW mode-locking pulse at 1064 nm, with an output power of 5 W, a pulse repetition rate of 98 MHz, and a pulse width of 25.3 ps. The beam quality is M2 < 1.12 and the optical-optical efficiency is 35.7%.

Active synchronization of two independent femtosecond and picosecond lasers and sum frequency generation of two laser pulses

The scheme for synchronizing Ti:sapphire femtosecond laser and Nd:YVO4 picosecond laser is discribed. Sub-ps jitter is obtained, based on which broad-band femtosecond blue-light laser of 460nm is generated through mixing two laser pulses in the BBO crystal. The technique not only shows a general way of synchronizing lasers of completely different wavelength and pulse width, but also demonstrates a new scheme for generating ultra-short laser with new wavelength through nonlinear frequency mixing.

Compact multi-Watt picosecond coherent white light sources using multiple-taper fibers

The combination of a diode-pumped Nd:YVO4 picosecond laser source with tapered fibers allows the realization of a compact white light source with an average output power of up to 5.65 W. We generated supercontinua with a throughput of ~50% over a spectral range of up to 1140 nm by using a series of tapered fibers that were spliced together.