Carrier-envelope phase on-chip scanner and control of laser beams.

The carrier-envelope phase (CEP) is an important property of few-cycle laser pulses, allowing for light field control of electronic processes during laser-matter interactions. Thus, the measurement and control of CEP is essential for applications of few-cycle lasers. Currently, there is no robust method for measuring the non-trivial spatial CEP distribution of few-cycle laser pulses. Here, we demonstrate a compact on-chip, ambient-air, CEP scanning probe with 0.1 µm3 resolution based on optical driving of CEP-sensitive ultrafast currents in a metal-dielectric heterostructure. We successfully apply the probe to obtain a 3D map of spatial changes of CEP in the vicinity of an oscillator beam focus with pulses as weak as 1 nJ. We also demonstrate CEP control in the focal volume with a spatial light modulator so that arbitrary spatial CEP sculpting could be realized.

Ultrafast multipulse damage threshold of femtosecond high reflectors.

Laser-induced damage threshold is a fundamental figure of merit of femtosecond optical components used in large-scale laser systems. We tested a series of ultrafast mirrors featuring high band-gap dielectric materials as well as improved design and coating techniques. In a broad range of the damage test pulse train involving between 10 and 100,000 pulses (40 fs, 800 nm), pure dielectric high reflectors exhibit around 1.5 J/cm2 and hybrid Ag-multilayer mirrors can exhibit well above 1.2 J/cm2 damage threshold. In addition, a reference antireflection coating exceeded 2 J/cm2. Damage threshold dependence on the number of pulses was similar for all optics involved.

Femtosecond damage resistance of femtosecond multilayer and hybrid mirrors.

Improving the laser-induced damage threshold of optical components is a basic endeavor in femtosecond technology. By testing more than 30 different femtosecond mirrors with 42 fs laser pulses at 1 kHz repetition rate, we found that a combination of high-bandgap dielectric materials and improved design and coating techniques enable femtosecond multilayer damage thresholds exceeding 2 J/cm2 in some cases. A significant ×2.5 improvement in damage resistance can also be achieved for hybrid Ag-multilayer mirrors exhibiting more than 1 J/cm2 threshold with a clear anticorrelation between damage resistance and peak field strength in the stack. Slight dependence on femtosecond pulse length and substantial decrease for high (megahertz) repetition rates are also observed.