Chirped Pulse Amplification Ti Research Articles

5-Hz, 150-TW Ti:sapphire Laser with High Spatiotemporal Quality

150-TW, 23-fs laser pulses with high spatial and temporal qualities have been generated at 5 Hz from a chirped-pulse amplification Ti:sapphire laser. The temporal and the spatial qualities of the laser pulse were optimized and characterized for high availability in the fields of high-field science and relativistic laser-matter interactions. The pulse duration was optimized by maximizing the spectral bandwidth and by minimizing the spectral phase error. A temporal contrast was enhanced using an ultrafast Pockels cell and a double plasma mirror, and wavefront aberrations were corrected using an adaptive optics system. Spatiotemporal couplings were characterized by measuring a frequency-resolved wavefront to estimate their effect on the peak intensity at the focus. Due to the high spatiotemporal quality resulting from this optimization and characterization of the laser beam, the 5-Hz 150-TW Ti:sapphire laser will be the workhorse for a variety of research on relativistic laser-matter interactions.

Conceptual Design of a Laser Driver for a Plasma Accelerator User Facility

The purpose of the European project EuPRAXIA is to realize a novel plasma accelerator user facility. The laser driven approach sets requirements for a very high performance level for the laser system: pulse peak power in the petawatt range, pulse repetition rate of several tens of Hz, very high beam quality and overall stability of the system parameters, along with 24/7 operation availability for experiments. Only a few years ago these performances were considered unrealistic, but recent advances in laser technologies, in particular in the chirped pulse amplification (CPA) of ultrashort pulses and in high energy, high repetition rate pump lasers have changed this scenario. This paper discusses the conceptual design and the overall architecture of a laser system operating as the driver of a plasma acceleration facility for different applications. The laser consists of a multi-stage amplification chain based CPA Ti:Sapphire, using frequency doubled, diode laser pumped Nd or Yb solid state lasers as pump sources. Specific aspects related to the cooling strategy of the main amplifiers, the operation of pulse compressors at high average power, and the beam pointing diagnostics are addressed in detail.

Contrast ratio enhancement by spectral matching of a seed laser pulse and ASE in a Ti:sapphire laser system.

The ASE (amplified spontaneous emission) level in a laser system consisting of an oscillator and a regenerative amplifier is very important, for example, in the interaction of an intense laser pulse and a thin foil, so a lower ASE level is always required. In this paper, we propose a new method to achieve a lower ASE level, which can be obtained by spectral matching of the seed laser beam and the ASE in a CPA (chirped-pulse amplification) Ti:sapphire laser system. In this method, two baffles are used to control the seed pulse spectrum by blocking a portion of the seed beam in a grating stretcher and it was found that the spectral matching method can reduce the temporal contrast ratio (after the regenerative amplifier) by a factor of 10 in a few hundred picosecond scale. This kind of spectral matching method is simple and it can be easily employed for other CPA laser systems to enhance the contrast ratio.

4.2 PW, 20 fs Ti:sapphire laser at 0.1 Hz.

We demonstrated the generation of 4.2PW laser pulses at 0.1Hz from a chirped-pulse amplification Ti:sapphire laser. The cross-polarized wave generation and the optical parametric chirped-pulse amplification stages were installed for the prevention of the gain narrowing and for the compensation of the spectral narrowing in the amplifiers, obtaining the spectral width of amplified laser pulses of 84nm (FWHM), and enhancing the temporal contrast. The amplified laser pulses of 112J after the final booster amplifier were compressed to the pulses with 83J at 19.4fs with a shot-to-shot energy stability of 1.5% (RMS). This 4.2PW laser will be a workhorse for exploring high field science.

Generation of high-contrast, 30 fs, 15 PW laser pulses from chirped-pulse amplification Ti:sapphire laser

High-contrast, 30 fs, 1.5 PW laser pulses are generated from a chirped-pulse amplification (CPA) Ti:sapphire laser system at 0.1 Hz repetition rate. The maximum output energy of 60.2 J is obtained, at a pump energy of 120 J, from a booster amplifier that is pumped by four frenquency-doubled Nd:glass laser systems. During amplification, parasitic lasing is suppressed by index matching fluid with absorption dye and the careful manipulation of the time delay between the seed and pump pulses. An amplified pulse passes through a pulse compressor consisting of four gold-coated gratings. After compression, the measured pulse duration is 30 fs, and the output energy is 44.5 J, yielding a peak power of about 1.5 PW. The output energy of 44.5 J and output power of 1.5-PW are the highest values ever achieved from the femtosecond CPA Ti:sapphire laser system. To maintain a sufficiently high temporal contrast, a saturable absorber is installed in the front-end system with two ultrafast Pockels cells in order to minimize the amplified spontaneous emission (ASE) and pre-pulse intensity. An adaptive optics system is implemented for PW laser pulses and a focused intensity of about 1 × 10(22) W/cm(2) can be obtained when an f/3 optic is used.

Study of femtosecond ablation on aluminum film with 3D two-temperature model and experimental verifications

In this paper, a 3D two-temperature model is introduced to investigate femtosecond ablation on aluminum film. 3D temperature evolutions for both electrons and lattice are obtained, which present us a vivid view of the energy transformation process during femtosecond ablation. Simulated 3D ablation craters irradiated by a single pulse with different energy are acquired, from which we can easily and precisely predict crater depth and radius before ablation takes place. In the experiment we measure the radii of the craters ablated by pulses with different energy and numbers delivered from a chirped pulse amplification Ti: sapphire system. The threshold fluence for both single and multi pulses are obtained. Comparisons are made between results of the experiment and relative simulated calculations show the reliability of our proposed calculation model.

Contrast ratio of femtosecond ultraintense Ti:sapphire laser with multi-pass amplifier

According to the theory of chirped pulse amplification (CPA), we analyze numerically the gain characteristic of laser pulses in multi-pass amplifier. A CPA Ti:sapphire laser with 10-pass scheme is designed and built. The experimental result shows that the contrast ratio of the femtosecond pulse is obviously enhanced by two orders from 10-5 to 10-7 under a pump flux of 1.6 J/cm2. This work demonstrates that the contrast ratio of the amplified femtosecond laser pulse could be effectively improved by multi-pass preamplifier.

01 Hz 10 PW Ti:sapphire laser

We report on the generation of 1.0 PW, 30 fs laser pulses at a 0.1 Hz repetition rate from a chirped-pulse amplification Ti:sapphire laser system. The energy of the laser pulses is amplified up to 47 J in a final three-pass booster amplifier having 96 J pump energy. To the best of our knowledge, this is the first petawatt Ti:sapphire laser system at a 0.1 Hz repetition rate. The shot-to-shot energy fluctuation of the laser pulses is as low as 0.53% in rms value, and the laser pulses have homogeneous flattop spatial beam profiles.

Design of a Femtosecond Ti:sapphire Laser for Generation and Temporal Optimization of 0.5-PW Laser Pulses at a 0.1-Hz Repetition Rate

A chirped-pulse amplification Ti:sapphire laser system has been designed using a 10-Hz 100-TW Ti:sapphire laser to generate 0.1-Hz 0.5-PW laser pulses and optimize their temporal qualities such as temporal contrast and pulse duration. A high-energy booster amplifier to be added is expected to produce an energy above 30 J through the parasitic lasing suppression and the efficient amplification. To improve the temporal contrast of the laser pulses, a high-contrast 1-kHz amplifier system is used as a front-end. A grating stretcher which makes the laser pulse have 1-ns duration is used to prevent optical damages due to high pulse energy during amplification. A grating compressor has been designed with group delay analysis to obtain the recompressed pulse duration close to the transform-limited pulse duration. The final laser pulses are expected to have energy above 20 J and duration below 40 fs.

Surface ablation of lithium tantalate by femtosecond laser

We report measurements of the laser induced breakdown threshold in lithium tantalate with different number of pulses delivered from a chirped pulse amplification Ti: sapphire system. The threshold fluences were determined from the relation between the diameter D 2 of the ablated area and the laser fluence F 0. The threshold of lithium tantalite under single-shot is found to be 1.84 J/cm 2, and the avalanche rate was determined to be 1.01 cm 2/J by calculation. We found that avalanche dominates the ablation process, while photoionization serves as a free electron provider.

Laser Machining for Fabrication of Hohlraums and Capsules

Laser machining technology has been used to demonstrate the ability to rapidly perform jobs on all aspects of ICF targets. Lasers are able to rapidly perform modifications and repairs to the gold metal parts on hohlraums, make cuts in the delicate polymer parts of the hohlraum, and drill holes in the capsules to enable them to be filled with fuel. Lasers investigated in this work include 193 nm ArF and 248 nm KrF excimers and 810 nm chirped-pulse amplification Ti:Sapphire lasers. The excimer lasers showed a definite advantage in drilling and machining of polymeric materials and the ultrashort infrared pulses of the Ti:Sapphire laser were far better for the gold structures.

Generation of 0.2-TW 5.5-fs optical pulses at 1 kHz using a differentially pumped hollow-fiber chirped-mirror compressor

Optical pulses with 1.1-mJ energy and 5.5-fs duration have been generated at 1-kHz repetition rate from a chirped pulse amplification Ti:Sapphire laser incorporating a differentially pumped hollow-fiber chirped-mirror compressor. The effects of self-focusing and multi-photon ionization during the beam propagation were minimized by differentially pumping the hollow fiber filled with neon. The spectral broadening at the hollow-fiber compressor was optimized by adjusting gas pressure, laser intensity, and laser chirp, covering from 540 nm to 950 nm.

Development and applications of a compact hybrid tabletop terawatt chirped-pulse amplification Ti:sapphire-Nd:glass laser for x-ray lasing and harmonic generation.

A hybrid tabletop (2 m x 3 m) terawatt chirped-pulse amplification Ti:sapphire-Nd:glass laser (1054 nm, 475 fs, 500 mJ, 9 x 10(17) W cm(-2)) has been developed for laser-matter experiments. An overall gain factor of 10(10) was achieved for the laser. The results of laser applications in the studies of soft-x-ray Ni-like Mo 18.9-nm lasing and of harmonic generation from solid surfaces are presented.

Continuously tunable high-order harmonics from atoms in an intense femtosecond laser field

Through the control of laser energy and chirp, continuous wavelength tuning of high-order harmonics was achieved without sacrificing spectral sharpness. This process was implemented after the amplification stage in a chirped-pulse amplification Ti:sapphire laser, without changing laser spectrum. It opens a new pathway for the realization of a continuously tunable, coherent, femtosecond x-ray source, i.e., a tabletop synchrotron.