scholarly journals Passive Q-Switching by Cr4+:YAG Saturable Absorber of Buried Depressed-Cladding Waveguides Obtained in Nd-Doped Media by Femtosecond Laser Beam Writing

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1689 ◽  
Author(s):  
Gabriela (Salamu) ◽  
Nicolaie Pavel
Keyword(s):  
Femtosecond Laser ◽  
Laser Beam ◽  
Repetition Rate ◽  
Peak Power ◽  
Continuous Wave ◽  
Average Power ◽  
Laser Pulses ◽  
Direct Writing ◽  
Optical Efficiency ◽  
Femtosecond Laser Beam

We report on laser performances obtained in Q-switch mode operation from buried depressed-cladding waveguides of circular shape (100 μm diameter) that were inscribed in Nd:YAG and Nd:YVO4 media by direct writing with a femtosecond laser beam. The Q-switch operation was realized with a Cr4+:YAG saturable absorber, aiming to obtain laser pulses of moderate (few μJ) energy at high (tens to hundreds kHz) repetition rate. An average power of 0.52 W at 1.06 μm consisting of a train of pulses of 7.79 μJ energy at 67 kHz repetition rate, was obtained from a waveguide realized in a 4.8 mm long, 1.1-at % Nd:YAG ceramics; the pulse peak power reached 1.95 kW. A similar waveguide that was inscribed in a 3.4 mm long, 1.0-at % Nd:YVO4 crystal yielded laser pulses with 9.4 μJ energy at 83 kHz repetition rate (at 0.77 W average power) and 1.36 kW peak power. The laser performances obtained in continuous-wave operation were discussed for each waveguide used in the experiments. Thus, a continuous-wave output power of 1.45 W was obtained from the circular buried depressed-cladding waveguide inscribed in the 1.1-at %, 4.8 mm long Nd:YAG; the overall optical-to-optical efficiency, with respect to the absorbed pump power, was 0.21. The waveguide inscribed in the 1.0-at %, 3.4 mm long Nd:YVO4 crystal yielded 1.85 W power at 0.26 overall optical efficiency. This work shows the possibility to build compact laser systems with average-to-high peak power pulses based on waveguides realized by a femtosecond (fs) laser beam direct writing technique and that are pumped by a fiber-coupled diode laser.

The diffraction-ray model of single filamentation of femtosecond laser pulses for estimating characteristics of the multiple filamentation domain in air

2021 ◽  
Vol 64 (1) ◽  
pp. 154-164
Author(s):  
A.A. Zemlyanov ◽  
◽  
Y.E. Geints ◽  
O.V. Minina ◽  
◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Beam ◽  
Peak Power ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Small Scale ◽  
Beam Forming ◽  
Physical Processes ◽  
Multiple Filamentation ◽  
Number Increase

The characteristics of the domain of multiple filamentation of femtosecond laser pulses in air were estimated based on the single filamentation model. As the single filamentation model, the diffraction-ray model is considered. It is based on the representation of a laser beam as a set of diffraction-ray tubes nested in each other that do not intersect in space and do not exchange energy with each other. In this situation changes in tubes shape and cross section during propagation demonstrate the effect of physical processes that occur with radiation in the medium. It is shown that the use of this model for interpreting experimental results and predicting effects is effective. In particular, it was demonstrated that the radius of small-scale intensity inhomogeneities in the profile of a centimeter laser beam, forming the domain of multiple filamentation of subterawatt femtosecond laser pulses, is several millimeters. The power in these inhomogeneities varies from several units to several tens of gigawatts. Telescoping the initial laser beam, leading to an increase in its radius, also expands the sizes of the initial small-scale intensity inhomogeneities and reduces the power contained in them. As a result of this, the coordinate of the filamentation beginning shifts along the path from the source of laser pulses. As the peak power in the beam increases, the length of the filaments and their number increase.

High-power thin-disk lasers emitting beams with axially-symmetric polarizations

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Marwan Abdou Ahmed ◽  
Frieder Beirow ◽  
André Loescher ◽  
Tom Dietrich ◽  
Danish Bashir ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Average Power ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Thin Disk ◽  
Axially Symmetric ◽  
Radial Polarization ◽  
Average Output ◽  
Optical Efficiency ◽  
Circular Grating

Abstract We present the intracavity generation of beams with radial polarization at an average output power of 750 W and an optical efficiency of 43% from a continuous wave thin-disk laser. Circular grating waveguide output couplers (GWOC) were used to select the radial polarization. The sensitivity of the polarizing function of the GWOC with regards to the fabrication tolerances is also analysed in details with a particular emphasis on the effect of the duty cycle and the geometrical profile of the gratings. Furthermore, we present the conversion of femtosecond laser pulses from linear to azimuthal polarization using a nanograting-based polarization converter. Azimuthally polarized beams with an average power of up to 850 W, a pulse duration of 400 fs and a pulse repetition rate of 1 MHz were generated in this way with a conversion efficiency of >90%.

Laser emission from diode-pumped Nd:YAG cladding waveguides obtained by direct writing with a femtosecond-laser beam

2014 ◽  
Author(s):  
Gabriela Salamu ◽  
Flavius Voicu ◽  
Florin Jipa ◽  
Marian Zamfirescu ◽  
Traian Dascalu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Beam ◽  
Laser Emission ◽  
Direct Writing ◽  
Femtosecond Laser Beam ◽  
Diode Pumped

scholarly journals Polystyrene Thin Films Nanostructuring by UV Femtosecond Laser Beam: From One Spot to Large Surface

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1060
Author(s):  
Olga Shavdina ◽  
Hervé Rabat ◽  
Marylène Vayer ◽  
Agnès Petit ◽  
Christophe Sinturel ◽  
...  
Keyword(s):  
Thin Films ◽  
Femtosecond Laser ◽  
Laser Beam ◽  
Repetition Rate ◽  
Irradiation Time ◽  
Large Area ◽  
Periodic Nanostructures ◽  
Femtosecond Laser Beam ◽  
Scanning Irradiation ◽  
Laser Beam Scanning

In this work, direct irradiation by a Ti:Sapphire (100 fs) femtosecond laser beam at third harmonic (266 nm), with a moderate repetition rate (50 and 1000 Hz), was used to create regular periodic nanostructures upon polystyrene (PS) thin films. Typical Low Spatial Frequency LIPSSs (LSFLs) were obtained for 50 Hz, as well as for 1 kHz, in cases of one spot zone, and also using a line scanning irradiation. Laser beam fluence, repetition rate, number of pulses (or irradiation time), and scan velocity were optimized to lead to the formation of various periodic nanostructures. It was found that the surface morphology of PS strongly depends on the accumulation of a high number of pulses (103 to 107 pulses) at low energy (1 to 20 µJ/pulse). Additionally, heating the substrate from room temperature up to 97 °C during the laser irradiation modified the ripples’ morphology, particularly their amplitude enhancement from 12 nm (RT) to 20 nm. Scanning electron microscopy and atomic force microscopy were used to image the morphological features of the surface structures. Laser-beam scanning at a chosen speed allowed for the generation of well-resolved ripples on the polymer film and homogeneity over a large area.

scholarly journals Biomimetic surface structures in steel fabricated with femtosecond laser pulses: influence of laser rescanning on morphology and wettability

2018 ◽  
Vol 9 ◽  
pp. 2802-2812 ◽  
Author(s):  
Camilo Florian Baron ◽  
Alexandros Mimidis ◽  
Daniel Puerto ◽  
Evangelos Skoulas ◽  
Emmanuel Stratakis ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Repetition Rate ◽  
Laser Processing ◽  
Laser Pulses ◽  
High Repetition Rate ◽  
Femtosecond Laser Pulses ◽  
Surface Structures ◽  
Complex Structures ◽  
Direct Writing ◽  
Wide Range

The replication of complex structures found in nature represents an enormous challenge even for advanced fabrication techniques, such as laser processing. For certain applications, not only the surface topography needs to be mimicked, but often also a specific function of the structure. An alternative approach to laser direct writing of complex structures is the generation of laser-induced periodic surface structures (LIPSS), which is based on directed self-organization of the material and allows fabrication of specific micro- and nanostructures over extended areas. In this work, we exploit this approach to fabricate complex biomimetic structures on the surface of steel 1.7131 formed upon irradiation with high repetition rate femtosecond laser pulses. In particular, the fabricated structures show similarities to the skin of certain reptiles and integument of insects. Different irradiation parameters are investigated to produce the desired structures, including laser repetition rate and laser fluence, paying special attention to the influence of the number of times the same area is rescanned with the laser. The latter parameter is identified to be crucial for controlling the morphology and size of specific structures. As an example for the functionality of the structures, we have chosen the surface wettability and studied its dependence on the laser processing parameters. Contact angle measurements of water drops placed on the surface reveal that a wide range of angles can be accessed by selecting the appropriate irradiation parameters, highlighting also here the prominent role of the number of scans.

scholarly journals An Eye-Safe, SBS-Free Coherent Fiber Laser LIDAR Transmitter with Millijoule Energy and High Average Power

Photonics ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 15
Author(s):  
Mehmetcan Akbulut ◽  
Leonid Kotov ◽  
Kort Wiersma ◽  
Jie Zong ◽  
Maohe Li ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Repetition Rate ◽  
Peak Power ◽  
Figure Of Merit ◽  
Current System ◽  
Glass Fibers ◽  
Average Power ◽  
High Gain ◽  
Short Length ◽  
High Average Power

We report on an eye-safe, transform-limited, millijoule energy, and high average power fiber laser. The high gain and short length of the NP phosphate-glass fibers enable the SBS-free operation with kW level peak power. The output energy is up to 1.3 mJ, and the average power is up to 23 W at an 18 kHz repetition rate with 600 ns pulses (peak power > 2.1 kW). The PER is ≈16 dB and the M2 of the beam is 1.33 × 1.18. The coherent LIDAR Figure Of Merit (FOM) is 174 mJ*sqrt(Hz), which to our knowledge is the highest reported for a fiber laser. We also report 0.75 mJ energy and >3.7 kW peak power with down to 200 ns pulses and up to 1.21 mJ energy with a 3–5 kHz repetition rate operation of the current system.

Fabrication and Characterization of Si Nano-Columns by Femtosecond Laser

2012 ◽  
Vol 16 ◽  
pp. 15-20 ◽  
Author(s):  
Omid Tayefeh Ghalehbeygi ◽  
Vural Kara ◽  
Levent Trabzon ◽  
Selcuk Akturk ◽  
Huseyin Kizil
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Beam ◽  
Chemical Etching ◽  
Silicon Surface ◽  
Laser Pulses ◽  
Laser Beam Profile ◽  
Fs Laser ◽  
Fabrication And Characterization

We fabricated Si Nano-columns by a femtosecond laser with various wavelengths and process parameters, whilst the specimen was submerged in water. The experiments were carried out by three types of wavelengths i.e. 1030 nm, 515nm, 343nm, with 500 fs laser pulses. The scales of these spikes are much smaller than micro spikes that are constructed by laser irradiation of silicon surface in vacuum or gases like SF6, Cl2. The Si nano-columns of 300 nm or less in width were characterized by SEM measurements. The formation of these Si Nano-columns that were revealed by SEM observation, indicates chemical etching with laser ablation occurred when surface exposed by laser beam. We observed 200 nm spikes height at the center of laser beam profile and the ones uniform in height at lateral incident area.

Self-organized microvoid array perpendicular to the femtosecond laser beam in CaF2crystals

2008 ◽  
Vol 5 (5) ◽  
pp. 394-397 ◽  
Author(s):  
X Hu ◽  
B Qian ◽  
P Zhang ◽  
X Wang ◽  
L Su ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Beam ◽  
Self Organized ◽  
Femtosecond Laser Beam
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