Subwavelength size of nanophotonic devices in use with laser pulses at the few-cycle limit raises new questions about the spatial distribution of the carrier-envelope phase (CEP). It has been shown that the complexity of the CEP distribution for few-cycle laser pulses can go far beyond the axial phase flip, known as the Gouy phase. Moreover, the phase landscape is governed by various laser parameters, some of which can be deliberately changed in order to control the CEP distribution. To be able to fully grasp the control over CEP an accessible and reliable way to measure the distribution is needed. The measurement of CEP distribution of few-cycle laser pulses is challenging and the method so far relies on vacuum apparatus. Recently discovered light-driven CEP sensitive currents in dielectrics, which can be detected with microsized on-chip electrodes, offer a new perspective for the phase detection. In this work, we present a proof-of-principle method for measuring the CEP spatial distribution. With on-chip scanning the focal volume of tightly focused oscillator laser pulses we obtain the three-dimensional map of the phase with resolution down to 500 nm.
Our work demonstrates nonadiabatic tunneling of photoelectrons in the near-field of gold nanostructures, which occurs in the transition region between the multi-photon-induced photoemission and tunneling emission regimes. Measured kinetic energy spectra at higher laser intensities indicates strong-field electron accelaration and recollision, characteristic for the tunneling emission regime. At the same time, constant scaling of the photoelectron current with the intensity has been measured, a trait of the multi-photon-induced photoemission regime. The Keldysh value of γ ≈ 2 for the transition was determined by analyzing the measured photoemission spectra. This value is in good agreement with the results acquired by the numerical solution of the Time-Dependent Schrödinger Equation.
Results of a comparative study on single-shot surface ablation of commercial optical glasses together with the transient reflectivity enhancement during the process are reported. Three types of optical glasses: Schott’s BOROFLOAT®, BK7 and B270 are ablated by single pulses of 34 fs duration at 800 nm central wavelength of the TeWaTi laser systems at University of Szeged, varying systematically both the pulse energy and the beam diameter on the surface, while recording the reflected signal. The depth and diameter of the ablated holes are characterized ex-situ by a DEKTAK profilometer. Very similar ablation characteristics have been determined: Above the ablation thresholds at 5.84±0.21 Jcm-2 (1.72±0.06*1014 Wcm-2), 6.43±0.56 Jcm-2 (1.89±0.16*1014 Wcm-2) and 5.86±0.31 Jcm-2 (1.75±0.09*1014 Wcm-2) for BOROFLOAT®, BK7 and B270, respectively, both the diameter and the depth of the holes produced show logarithmic increase as a function of pulse energy/fluence until saturating above ~18 Jcm-2. On the contrary, significant differences have been obtained in the time integrated transient reflectivities, with the highest absolute values measured for the BOROFLOAT® glass. Strong spot size dependence has been revealed: The reflectivity increases monotonously with increasing pulse energy for all spot sizes, with decreasing absolute values/slopes with decreasing spot areas. Different reflectivities belong to the same fluence/intensity depending on the actual spot size, consequently the fluence/intensity alone does not define unambigously the characteristics of the plasma. The correct description of the changes in reflectivity requires the specification of the spot size together with the pulse energy/fluence/intensity.
The conceptual design and proof of principle experimental results of a polarization rotator based on mirrors are
presented. The device is suitable for any-angle, online rotation of the plane of polarization of high peak intensity ultrashort
laser pulses. Controllable rotation of the polarization vector of short laser pulses with a broad bandwidth requires
achromatic retarding plates which have a limited scalability and the substantial plate thickness can lead to pulse
broadening and inaccurate polarization rotation. Polarization rotators based on reflective optical elements are preferable
alternatives to wave plates especially when used in high average power or high peak intensity ultra-short laser systems.
The control of the polarization state is desirable in many laser-matter interaction experiments e.g., high harmonic and
attosecond pulse generation, electron, proton and ion acceleration, electron-positron pair creating, vacuum nonlinear
polarization effect. The device can also serve as a beam attenuator, in combination with a linear polarizer.
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