Fiber Chirped Pulse Amplification System Research Articles

57 W, 27 fs pulses from a fiber laser system using nonlinear compression

We report on the generation of 27 fs pulses with an average output power of 57 W and a repetition rate of 78 MHz. The pulses are generated by combining a high average power fiber chirped pulse amplification (FCPA) system with a microstructured large-mode-area fiber for nonlinear compression. The FCPA system delivers 270 fs pulses in a linearly polarized beam with diffraction-limited quality. Nonlinear compression is achieved by launching the pulses into a short (few cm) piece of microstructured fiber and subsequent compression by a pair of chirped mirrors.

High energy femtosecond fiber chirped pulse amplification system with adaptive phase control

We demonstrate increased peak power from an Yb fiber CPA system operating with strong self-phase modulation by shaping the spectral-phase of the input pulses. An adaptive control loop used feedback from the output autocorrelation. We investigated pre-compensation of both SPM phase distortion at high energies, and residual dispersion from mismatched stretcher/compressor technologies at low energies. Phase shaping resulted in improved pulse quality. When using a bulk grating stretcher, shaping increased the autocorrelation peak by a factor of 2.9, and with a fiber stretcher, shaping increased the autocorrelation peak by a factor of 3.4. High-quality 800 fs, 65 microJ recompressed pulses were produced. This technique could benefit a wide variety of fiber amplifier systems and is self-optimising for operation at both low and high pulse energies.

Millijoule pulse energy high repetition rate femtosecond fiber chirped-pulse amplification system

We report on an ytterbium-doped fiber chirped-pulse amplification (CPA) system delivering millijoule level pulse energy at repetition rates above 100 kHz corresponding to an average power of more than 100 W. The compressed pulses are as short as 800 fs. As the main amplifier, an 80 microm core diameter short length photonic crystal fiber is employed, which allows the generation of pulse energies up to 1.45 mJ with a B-integral as low as 7 at a stretched pulse duration of 2 ns. A stretcher-compressor unit consisting of dielectric diffraction gratings is capable of handling the average power without beam and pulse quality distortions. To our knowledge, we present the highest pulse energy ever extracted from fiber based femtosecond laser systems, and a nearly 2 orders of magnitude higher repetition rate than in previously published millijoule-level fiber CPA systems.

90 W average power 100 μJ energy femtosecond fiber chirped-pulse amplification system

We report on an ytterbium-doped fiber based chirped-pulse amplification system delivering 100 microJ pulse energy at a repetition rate of 900 kHz, corresponding to an average power of 90 W. The emitted pulses are as short as 500 fs. To the best of our knowledge, this is the highest average power ever reported for high-energy femtosecond solid-state laser systems.

Chirped-pulse amplification near the gain-narrowing limit of Yb-doped fiber using a reflection grism compressor

We report a numerical and experimental study of chirped-pulse amplification of femtosecond pulses near the gain narrowing limit of Yb-doped fiber. We show that a strongly inhomogeneous lineshape provides a good description of pulse amplification in the linear regime (nonlinear phase shift ΦNL<1). Compensation of second- and third-order dispersion using a high-efficiency reflection grism compressor is demonstrated in a fiber chirped-pulse amplification system. A Fourier-transform-limited pulse duration of 120 fs is obtained for the highest achieved gain (23 dB).

Parametric amplification and compression to ultrashort pulse duration of resonant linear waves

We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser radiation. Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad bandwidth signal generation is a promising alternative to white light generation in bulky glass or sapphire plates. We demonstrate a novel and successful signal engineering implemented in a setup for parametric amplification and subsequent recompression of resonant linear waves resulting from soliton fission in a highly nonlinear photonic crystal fiber. The applied pump source is a high repetition rate ytterbium-doped fiber chirped pulse amplification system. The presented approach results in the generation of ~50 fs pulses at MHz repetition rate. The potential of generating even shorter pulse duration and higher pulse energies will be discussed.

Femtosecond mode-locked Yb fiber laser for single-mode fiber chirped pulse amplification system

High-peak-power laser systems are based on the chirped pulse amplification (CPA) technique. CPA laser system needs a mode-locked laser oscillator for stable ultrashort pulse laser generation. We report a single-mode fiber CPA system which consists of stable mode-locked Yb-doped fiber laser oscillator with a wide tuning range, chirped fiber Bragg grating stretcher, and two Yb-doped fiber amplifiers. The single-mode fibers can generate high-quality and single-mode beams which are stable for long time.

Large-aperture chirped volume Bragg grating based fiber CPA system

A fiber chirped pulse amplification system at 1558 nm was demonstrated using a large-aperture volume Bragg grating stretcher and compressor made of Photo-Thermal-Refractive (PTR) glass. Such PTR glass based gratings represent a new type of pulse stretching and compressing devices which are compact, monolithic and optically efficient. Furthermore, since PTR glass technology enables volume gratings with transverse apertures which are large, homogeneous and scalable, it also enables high pulse energies and powers far exceeding those achievable with other existing compact pulse-compression technologies. Additionally, reciprocity of chirped gratings with respect to stretching and compression also enables to address a long-standing problem in CPA system design of stretcher-compressor dispersion mismatch.

Nonlinear distortion free fiber-based chirped pulse amplification with self-phase modulation up to 2π

We demonstrate the removal of 2pi radians of self-phase modulation (SPM) in a fiber-based chirped pulse amplification (CPA) system. Compensation of SPM distortion is achieved in the time domain by using a LiNbO(3) electro-optic phase modulator to emulate a negative nonlinear index of refraction. By synthesizing the drive waveform to the phase modulators with two RF frequencies that are phase-locked to the repetition rate of the seed laser, we achieve large phase compensations using cost-effective narrow band electronics. Our technique is simple, robust and can be readily integrated into existing fiber CPA systems.

High Power Femtosecond Fiber Chirped Pulse Amplification System for High Speed Micromachining

The need for improved precision in a wide variety of micromachining applications has driven scientific interest in ultrashort pulse lasers. Despite numerous demonstrations of reduced heat effect and improved processing quality, the utility of such lasers has been limited by the heavy demands placed upon laser performance. In addition to high contrast laser pulses with minimal pulse-to-pulse fluctuation, an ultrashort pulse laser must provide near diffraction-limited beam quality and robust long-term laser operation with high repetition rate for high processing speeds. We report here on a research prototype, high power femtosecond fiber chirped pulse amplification system. The system produces compressed pulses with energies >50 µJ at >15 W with M 2 1000:1 temporal contrast despite significant self-phase modulation during amplification corresponding to a nonlinear phase delay of ~6π. As a demonstration of high speed femtosecond micromachining, we drill and cut 0.5-mm thick metal, semiconductor and dielectric targets.

Micromachining with a 50 W, 50 μJ, subpicosecond fiber laser system

A 50 W sub-picosecond fiber chirped pulse amplification system generating 50 muJ pulses at a repetition rate of 1 MHz is demonstrated. As required for precision high speed micro-machining, this system has a practical system configuration enabled by the fiber stretcher and 1780 l/mm dielectric diffraction grating compressor and is capable of ablation rates >0.17 mm3/s metal, ceramic, and glass.

High energy femtosecond Yb cubicon fiber amplifier

The generation of cubicon pulses from an Yb fiber chirped pulse amplification system at pulse energies up to 200 microJ is demonstrated. After pulse compression 650 fs pulses with a pulse energy of 100 microJ are obtained, where pulse compression relies on the compensation of third-order dispersion mismatch between the stretcher and compressor via self-phase modulation of the cubicon pulses in the fiber amplifier. Values of self-phase modulation well in excess of pi can be tolerated for cubicon pulses, allowing for the nonlinear compensation of very large levels of dispersion mismatch between pulse stretcher and compressor.

Chirped pulse amplification with a nonlinearly chirped fiber Bragg grating matched to the Treacy compressor.

We demonstrate a fiber chirped pulse amplification system that uses an engineered nonlinearly chirped fiber Bragg grating stretcher dispersion matched to the Treacy compressor. The seed pulses at 1558 nm are stretched to 720 ps, amplified by more than 50 dB to 6.5-microJ energy, and recompressed to 940 fs. After almost 1000 times compression the pulses are within 30% of the bandwidth limit and have a contrast ratio of better than 30 dB.

All fiber chirped-pulse amplification system based on compression in air-guiding photonic bandgap fiber

We report on the experimental demonstration of an all fiber CPA system based on a step-index fiber stretcher and an air-guiding photonic crystal fiber compressor. The ultrafast fiber laser system producing an average power of 6.0 W with 100-fs pulses at 73 MHz, what corresponds to a peak power out of the compressor fiber of 0.82 MW. This completely fiber integrated approach has the potential to be scaled to significantly higher peak powers.

Highly efficient transmission gratings in fused silica for chirped-pulse amplification systems

We report on highly efficient transmission gratings in fused silica with a grating period of 800 nm generated by electron-beam lithography. At a wavelength of 1060 nm, 95% diffraction efficiency is achieved under Littrow conditions. The damage threshold, extremely enhanced compared with conventional gold-coated diffraction gratings, makes these gratings the key elements in high average power (>100 W) femtosecond fiber chirped-pulse amplification systems.

High average power ultra-fast fiber chirped pulse amplification system

We report on a high-gain diode-pumped ytterbium-doped fiber-amplifier system delivering pulse energies in the 100-μJ range at high repetition rates (32 kHz) with nearly-diffraction-limited beam quality (M2∼1.7) at a 1060-nm center wavelength. Femtosecond seed-laser pulses are stretched in a commercially available single-mode fiber and compressed after amplification to subpicosecond pulse duration. In a multimode Yb-doped fiber amplifier we have demonstrated average powers of up to 22 W and single-pulse energies of up to 130 μJ.