Abstract
We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6 fs pulses with 9 μJ pulse energy. In krypton, we reach conversion efficiencies from the NIR to the extreme ultraviolet (XUV) radiation pulse energy on the order of ∼10−6 with less than 3 μJ driving pulse energy. This is achieved by optimizing the OPCPA for a spatially and temporally clean pulse and by a specially designed high-pressure gas target. In the future, the high efficiency of the HHG source will be beneficial for high-repetition rate two-colour (NIR-XUV) pump-probe experiments, where the available pulse energy from the laser has to be distributed economically between pump and probe pulses.
Highlights
Attosecond pulses in the extreme-ultraviolet (XUV) spectral range are generated via high-order harmonic generation (HHG), when intense ultrashort laser pulses are focused into a generation gas
We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6fs pulses with 9μJ pulse energy at 200kHz repetition rate
We demonstrated efficient high-order harmonic generation in neon, argon and krypton driven by a high-repetition rate, few-cycle, NIR, OPCPA laser
Summary
Attosecond pulses in the extreme-ultraviolet (XUV) spectral range are generated via high-order harmonic generation (HHG), when intense ultrashort laser pulses are focused into a generation gas. While there is no fundamental reason for the HHG conversion efficiency to drop with decreasing laser pulse energy and tighter focusing [11], efficient HHG with a pulse repetition rate of >100kHz and driving pulse energy in the μJ range still is experimentally challenging This is mostly attributed to the complexity of the generation gas delivery system, which must provide localized high pressure (up to some bars) in the interaction region, while not contaminating the vacuum in the chamber. Resulting from these challenges, to the best of our knowledge, no attosecond pump-probe experiments have so far been performed at repetition rates exceeding a few ten kHz. In this work, we present a high-repetition rate, HHG based, XUV, attosecond pulse source, driven by a few-cycle, carrier-envelope phase (CEP) stable, OPCPA laser. By using a λ/2-plate and a thin-film polarizer (TFP) the second harmonic is divided into two beams to pump two NOPAs
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