Efficient single-cycle pulse compression of an ytterbium fiber laser at 10 MHz repetition rate

Abstract

Over the past years, ultrafast lasers with average powers in the 100 W range have become a mature technology, with a multitude of applications in science and technology. Nonlinear temporal compression of these lasers to few-or even single-cycle duration is often essential, yet still hard to achieve, in particular at high repetition rates. Here we report a two-stage system for compressing pulses from a 1030 nm ytterbium fiber laser to single-cycle durations with 5 μJ output pulse energy at 9.6 MHz repetition rate. In the first stage, the laser pulses are compressed from 340 to 25 fs by spectral broadening in a krypton-filled single-ring photonic crystal fiber (SR-PCF), subsequent phase compensation being achieved with chirped mirrors. In the second stage, the pulses are further compressed to singlecycle duration by soliton-effect self-compression in a neon-filled SR-PCF. We estimate a pulse duration of ~3.4 fs at the fiber output by numerically back-propagating the measured pulses. Finally, we directly measured a pulse duration of 3.8 fs (1.25 optical cycles) after compensating (using chirped mirrors) the dispersion introduced by the optical elements after the fiber, more than 50% of the total pulse energy being in the main peak. The system can produce compressed pulses with peak powers >0.6 GW and a total transmission exceeding 70%.

Low-noise tunable deep-ultraviolet supercontinuum laser

“…There has been little focus on the noise properties, except for a recent work reporting good long-term stability, but high pulse-to-pulse RIN values of 33.3% of a 275 nm RDW, attributed to the large RIN of 5.5% of the 2.45 µm pump 25 . The technology is now maturing to a level ready for applications, such as imaging and spectroscopy, which has seen a recent push towards table-top ytterbium-based lasers with MHz repetition rates as pump lasers, giving few-hundred fs pulses at center wavelengths of 1030 nm 21 , 22 . To get the necessary short pump pulses external pulse compression with chirped mirrors and a second gas-filled HC fiber is used the generate < 30 fs pump pulses 21 , 22 .…”

“…The technology is now maturing to a level ready for applications, such as imaging and spectroscopy, which has seen a recent push towards table-top ytterbium-based lasers with MHz repetition rates as pump lasers, giving few-hundred fs pulses at center wavelengths of 1030 nm 21 , 22 . To get the necessary short pump pulses external pulse compression with chirped mirrors and a second gas-filled HC fiber is used the generate < 30 fs pump pulses 21 , 22 . With the push towards MHz and applications it has become even more important to assure low levels of RIN of the source and one could fear that the external pulse compression module could significantly add to the RIN of an otherwise low-noise seed laser.…”

“…This concept has been employed using a range of gas species to generate UV radiation with broadband guiding HC PCFs 16 – 22 . The majority of these experiments relied on a titanium-sapphire laser to provide the pump pulses, resulting in an inherently large footprint and low repetition rate of 1 kHz to achieve the required pulse energy.…”

“…The majority of these experiments relied on a titanium-sapphire laser to provide the pump pulses, resulting in an inherently large footprint and low repetition rate of 1 kHz to achieve the required pulse energy. However, a few experiments have utilized the nonlinearly compressed output of ytterbium-based lasers, which significantly increases the repetition rate to MHz regime 21 , 22 , an important consideration for maximizing signal-to-noise ratio and average power in certain applications. Furthermore, the use of an ytterbium-doped gain medium paves the way to a more compact and rugged design, owing to the outstanding performance of these lasers at high repetition rates 23 , 24 .…”

“…This high RIN value for the pump was a result of wavelength conversion from a low-noise titanium-sapphire laser (0.5% RIN) using an optical parametric amplifier. Another study quotes a RIN value of 0.4% measured in the frequency domain, for 1030 nm pulses compressed to the single-cycle regime using a two-stage AR HC fiber compression scheme 22 . However, this study did not involve RDW generation and the UV component of the spectrum is not specifically isolated and measured.…”