ABSTRACT
Laser sources which produce GHz bursts of ultrashort pulses attract a lot of attention by demonstrating superior performance in material processing. Flexibility of the laser source in a selection of parameters for custom application is highly preferable. In this work, we demonstrate a very versatile method for burst formation using the active fiber loop (AFL). It allows forming GHz bursts containing from 2 up to approximately 2200 pulses in a burst (1000 ns burst width) with identical pulse separation and any predefined intra-burst pulse repetition rate (PRR). The burst pre-shaping by the amplification conditions in the AFL and by the modulation of transmission of the acousto-optic modulator was demonstrated. Industrial-grade ultrafast laser system was able to operate in the single-pulse and GHz-burst regimes. The laser system delivered high-quality 368 fs duration (FWHM) pulses of 15.3 µJ pulse energy and 30.6 W average output power at 2 MHz PRR in the single-pulse regime. In the GHz-burst operation regime, bursts of 2.2 GHz intra-burst repetition rate were formed and amplified to more than 30 W average output power with a burst energy up to 135 µJ at a burst repetition rate of 200 kHz. The sub-picosecond duration of pulses was obtained in the GHz-burst regime at different burst widths.
ABSTRACT
In this work, we present the development of a femtosecond tunable middle infrared (mid-IR) radiation source for the realization of a hybrid concept compact broadband high-resolution sum-frequency generation (SFG) spectroscopy system. For the realization of the new concept, we used a two-channel picosecond fiber laser as a seed for narrowband (â¼1.5 cm-1) and broadband ultrafast radiation sources operating at 1 kHz repetition rate. In order to achieve >500â cm-1 bandwidth widely tunable microjoule level pulses in the mid-IR spectral region (2-10â µm), broadband femtosecond source optimization was performed. Numerical simulations with different nonlinear crystals and optical parametric amplification layouts at given fixed initial conditions paved a way to experimentally realize an optimal scheme for a femtosecond mid-IR channel. Fully operating SFG spectrometer setup was assembled and tested. The developed SFG spectrometer demonstrates a unique combination of parameters: excellent spectral resolution (<3â cm-1) similar to a narrowband scanning picosecond spectrometers and fast simultaneous acquisition of broadband spectra up to more than 850â cm-1.
ABSTRACT
We demonstrate a method to synthesize ultra-high repetition rate bursts of ultrashort laser pulses containing any number of pulses within a burst with identical pulse separation and adjustable amplitude. The key element to synthesize the GHz bursts of ultrashort laser pulses is an active fiber loop. The method was implemented in the fiber chirped pulse amplification system to obtain 72 nJ-energy bursts of 20 pulses with a 2.65â GHz intra-burst pulse repetition rate and a 500 kHz burst repetition rate. The dispersion compensation mechanism ensured a mean pulse duration of 570 fs within the bursts.
ABSTRACT
In this work we presented a compact femtosecond laser system based on Yb doped fiber seed laser and efficient Yb:YAG crystal rod power amplifier. Matched pair of chirped fiber Bragg grating stretcher and chirped volume Bragg grating compressor were used to obtain high fidelity - Strehl ratio 76%, pulses of 764 fs duration, 104 µJ energy at 200 kHz repetition rate at the output of the laser system.
