Ultrastable fiber amplifier delivering 145-fs pulses with 6-μJ energy at 10-MHz repetition rate

CPA-ready femtosecond pulses at 1 MHz from a custom recycled output Mamyshev oscillator

A cost-effective fiber laser architecture is introduced in which the output seed pulse is stretched and then returned in the oscillator for an additional single-pass amplification without spectral broadening. It is implemented in an all-PM-fiber configuration based on a Mamyshev oscillator with a low repetition rate of 1 MHz. It features a linear oscillator bounded by two offset chirped fiber Bragg gratings accompanied by a third one acting as a pulse recycling filter. The latter tailors the pulse profile in amplitude and phase to seed femtosecond chirped-pulse amplification systems without additional pre-amplification nor pulse stretching. A single-pump prototype generating 200-nJ, 100-ps pulses compressible to 290 fs at 1030 nm and at 960 kHz is demonstrated. Furthermore, simulations show how this new oscillator architecture can provide tailored seed pulses with high enough spectral energy density and low enough nonlinear phase to generate sub-200 fs, 40 µJ, > 180 MW pulses from an all-fiber setup involving a single tapered-fiber power amplifier, without pulse picking.

High-repetition-rate, 50-µJ-level, 1064-nm, CPA laser system based on a single-stage double-pass Yb-doped rod-type fiber amplifier

A 1064-nm femtosecond fiber chirped pulse amplification (FCPA) laser system based on a single-stage double-pass Yb-doped rod-type photonic crystal fiber (PCF) amplifier was demonstrated with a pulse repetition rate of 500 kHz, which was specially designed for expected conversion efficiency enhancement of a 10.8 eV source. With a series of Yb:fiber power amplifiers, the average output power was boosted to approximately 35 W. Further, using a transmission gratings-based pulse compressor, an average output power of 27.5 W was achieved, corresponding to a pulse energy of 55 µJ and a compression efficiency of 78.6%. The shortest pulse duration was optimized to be 204 fs, which was also accompanied by obvious pedestal. A pulse duration of 336 fs was also obtained when the pulse quality was at a top priority. To the best of our knowledge, this is the first demonstration of high-repetition-rate high-pulse-energy 1064-nm, instead of 1035-nm, femtosecond laser, based on commercially available Yb-doped rod-type PCF amplifier.

All-optical fiber optic coherent amplifier

A fiber optic-based all-optical amplifier is designed by using the coherent perfect absorption phenomenon. For this purpose, we use a deposited chromium thin layer as an absorbent material on the cross-section of a PM fiber. By placing another fiber in front of the deposited one, we show that by controlling the relative phase between the two counter-propagating beams, total absorbance can be controlled. In the interaction of two beams with unequal intensities, absorption control can be associated with amplification for the weaker beam. By using this mechanism, the effect of an external phase-shifting parameter can be amplified. Furthermore, it is possible to amplify a small signal riding on a CW background through this all-optical procedure.

All-solid-state multipass spectral broadening to sub-20 fs

In this work, we present a nonlinear spectral broadening and compression scheme based on self-phase modulation in bulk media inside a Herriott-type multipass cell. With this reliable approach, we achieved a spectral broadening factor of 22 while maintaining an efficiency of over 60% at an average input power of 100 W, and an excellent output beam quality with M²=1.2. The output pulses were compressed to 18 fs, with the broadest spectrum supporting a Fourier-transform limit of 10 fs. The high efficiency and approximately four-optical-cycle pulse duration mark an important milestone towards the realization of a compact, high power oscillator-based driver for XUV frequency combs and other nonlinear processes.

High-energy few-cycle Yb-doped fiber amplifier source based on a single nonlinear compression stage

A simple, compact, and efficient few-cycle laser source at a central wavelength of 1 µm is presented. The system is based on a high-energy femtosecond ytterbium-doped fiber amplifier delivering 130 fs, 250 µJ pulses at 200 kHz, corresponding to 1.5 GW of peak power and an average power of 50 W. The unprecedented short pulse duration at the output of this system is obtained by use of spectral intensity and phase shaping, allowing for both gain narrowing mitigation and the compensation of the nonlinear accumulated spectral phase. This laser source is followed by a single-stage of nonlinear compression in a xenon-filled capillary, allowing for the generation of 14 fs, 120 µJ pulses at 200 kHz resulting in 24 W of average power. High-harmonic generation driven by this type of source will trigger numerous new applications in the XUV range and attosecond science.

High-power all-fiber femtosecond chirped pulse amplification based on dispersive wave and chirped-volume Bragg grating

We report a high-power all-fiber-integrated femtosecond chirped pulse amplification system operating at 1064 nm, which consists of a dispersive wave source, a fiber stretcher, a series of ytterbium-doped amplifiers and a chirped volume Bragg grating (CVBG) compressor. The dispersive wave is generated by an erbium-doped mode-locked fiber laser with frequency shifted to the 1 μm region in a highly nonlinear fiber. With three stages of ytterbium-doped amplification, the average output power is scaled up to 125 W. Through CVBG, the pulse duration is compressed from 525 ps to 566 fs, the average output power of 107 W with a high compression efficiency of 86% is achieved, and the measured repetition rate is 17.57 MHz, corresponding to the peak power of 10.8 MW.

High-power ultrafast Yb:fiber laser frequency combs using commercially available components and basic fiber tools

We present a detailed description of the design, construction, and performance of high-power ultrafast Yb:fiber laser frequency combs in operation in our laboratory. We discuss two such laser systems: an 87 MHz, 9 W, 85 fs laser operating at 1060 nm and an 87 MHz, 80 W, 155 fs laser operating at 1035 nm. Both are constructed using low-cost, commercially available components, and can be assembled using only basic tools for cleaving and splicing single-mode fibers. We describe practical methods for achieving and characterizing low-noise single-pulse operation and long-term stability from Yb:fiber oscillators based on nonlinear polarization evolution. Stabilization of the combs using a variety of transducers, including a new method for tuning the carrier-envelope offset frequency, is discussed. High average power is achieved through chirped-pulse amplification in simple fiber amplifiers based on double-clad photonic crystal fibers. We describe the use of these combs in several applications, including ultrasensitive femtosecond time-resolved spectroscopy and cavity-enhanced high-order harmonic generation.

615 fs pulses with 17 mJ energy generated by an Yb:thin-disk amplifier at 3 kHz repetition rate

A combination of Er/Yb:fiber and Yb:thin-disk technology produces 615 fs pulses at 1030 nm with an average output power of 72 W. The regenerative amplifier allows variation of the repetition rate between 3 and 5 kHz with pulse energies from 13 to 17 mJ. A broadband and intense seed provided by the compact and versatile fiber front-end minimizes gain narrowing. The resulting sub-ps performance is ideal for nonlinear frequency conversion and pulse compression. Operating in the upper branch of a bifurcated pulse train, the system exhibits exceptional noise performance and stability.