No Arabic abstract
High-brightness sources of coherent and few-cycle-duration light waveforms with spectral coverage from the UV to the THz would offer unprecedented versatility and opportunities for a spectacular range of applications from bio-chemical sensing, to time-resolved and nonlinear spectroscopy, to attosecond light-wave electronics. Combinations of various sources with frequency conversion and supercontinuum generation can provide relatively large spectral coverage, but many applications require much broader spectral range and low-jitter synchronization for time-domain measurements. Here, we present a carrier-envelope-phase stable light source, seeded by a mid-IR frequency comb, with simultaneous spectral coverage across 7 optical octaves, from the UV (340 nm) into the THz (40,000 nm). Combining soliton self-compression and dispersive wave generation in an anti-resonant-reflection photonic crystal fibre with intra-pulse difference frequency generation in BaGa2GeSe6, the spectral brightness is 2-5 orders of magnitude above synchrotron sources. This enables high-dynamic-range spectroscopies and provides enticing prospects for attosecond physics and material sciences.
The ability to measure and control the carrier envelope phase (CEP) of few-cycle laser pulses is of paramount importance for both frequency metrology and attosecond science. Here, we present a phase meter relying on the CEP-dependent photocurrents induced by circularly polarized few-cycle pulses focused between electrodes in ambient air. The new device facilitates compact single-shot, CEP measurements under ambient conditions and promises CEP tagging at repetition rates orders of magnitude higher than most conventional CEP detection schemes as well as straightforward implementation at longer wavelengths.
Controlling the carrier envelope phase (CEP) in mode-locked lasers over practically long timescales is crucial for real-world applications in ultrafast optics and precision metrology. We present a hybrid solution that combines a feed-forward technique to stabilize the phase offset in fast timescales and a feedback technique that addresses slowly varying sources of interference and locking bandwidth limitations associated with gain media with long upper-state lifetimes. We experimentally realize the hybrid stabilization system in an Er:Yb:glass mode-locked laser and demonstrate 75 hours of stabilization with integrated phase noise of 14 mrad (1 Hz to 3 MHz), corresponding to around 11 as of carrier to envelope jitter. Additionally, we examine the impact of environmental factors, such as humidity and pressure, on the long-term stability and performance of the system.
We present a method to distinguish the high harmonics generated in individual half-cycle of the driving laser pulse by mixing a weak ultraviolet pulse, enabling one to observe the cutoff of each half-cycle harmonic. We show that the detail information of the driving laser pulse, including the laser intensity, pulse duration and carrier-envelope phase, can be {it in situ} retrieved from the harmonic spectrogram. In addition, our results show that this method also distinguishes the half-cycle high harmonics for a pulse longer than 10 fs, suggesting a potential to extend the CEP measurement to the multi-cycle regime.
Ultrafast control of electron dynamics in solid state systems has recently found particular attention. By increasing the electric field strength of laser pulses, the light-matter interaction in solids might turn from a perturbative into a novel non-perturbative regime, where interband transitions from the valence to the conduction band become strongly affected by intraband motion. We have demonstrated experimentally and numerically that this combined dynamics can be controlled in graphene with the electric field waveform of phase-stabilized few-cycle laser pulses. Here we show new experimental data and matching simulation results at comparably low optical fields, which allows us to focus on the highly interesting transition regime where the light-matter interaction turns from perturbative to non-perturbative. We find a 5th order power-law scaling of the laser induced waveform-dependent current at low optical fields, which breaks down for higher optical fields, indicating the transition.
A novel scheme for stabilizing the carrier-envelope phase (CEP) of low-repetition rate lasers was demonstrated using a 350 mJ, 14 fs Ti:Sapphire laser operating at 10 Hz. The influence of the CEP on the generation of a continuum in the extreme ultraviolet (XUV) was observed.