Inline-delay Fourier transform imaging spectrometer for mid-IR ultrashort pulses.

An inline-delay Fourier transform imaging spectrometer (iFTIS) is used to measure spatiospectral coupling in a mid-infrared (mid-IR) optical parametric amplifier (OPA). The method employs a compact inline delay line using a birefringent wedge pair and a microbolometer array as an imaging sensor, providing continuous spectral coverage from ∼0.4 to 4.

Orbital perspective on high-harmonic generation from solids.

High-harmonic generation in solids allows probing and controlling electron dynamics in crystals on few femtosecond timescales, paving the way to lightwave electronics. In the spatial domain, recent advances in the real-space interpretation of high-harmonic emission in solids allows imaging the field-free, static, potential of the valence electrons with picometer resolution. The combination of such extreme spatial and temporal resolutions to measure and control strong-field dynamics in solids at the atomic scale is poised to unlock a new frontier of lightwave electronics.

Generation of structured coherent extreme ultraviolet beams from an MgO crystal.

Short wavelength high-harmonic sources are undergoing intense development for applications in spectroscopy and microscopy. Despite recent progress in peak and average power, spatial control over coherent extreme ultraviolet (XUV) beams remains a formidable challenge due to the lack of suitable optical elements for beam shaping and control. Here we demonstrate a robust and precise approach that structures XUV high-order harmonics in space as they are emitted from a nanostructured MgO crystal.

Characterization of high-harmonic emission from ZnO up to 11 eV pumped with a Cr:ZnS high-repetition-rate source.

We report the measurement of high-order harmonics from a ZnO crystal with photon energies up to 11 eV generated by a high-repetition-rate femtosecond Cr:ZnS laser operating in the mid-infrared at 2-3 μm, delivering few-cycle pulses with multi-watt average power and multi-megawatt peak power. High-focus intensity is achieved in a single pass through the crystal without a buildup cavity or nanostructued pattern for field enhancement. We measure in excess of 10 high-harmonic photons/second.

Observation of backward high-harmonic emission from solids.

We experimentally demonstrate backward emission of high-harmonics of a near-infrared laser from MgO and Si crystals in the direction of specular reflection. We show that the variation of the high-harmonic power with the angle of incidence can be predicted with nonlinear reflection coefficients derived originally for perturbative nonlinearities. A comparison of transmission and reflection geometries suggests that backward-propagating high-harmonics are an excellent reference to study nonlinear propagation of intense light in solids.