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We describe a non-interferometric ultrashort-pulse measurement technique based on frequency-resolved optical gating (FROG) with which pulses can be reconstructed directly, i.e. non-iteratively. Two different FROG spectrograms are measured, which represent the only information required to reconstruct the amplitudes and phases of two independent input pulses. The direct reconstruction method is demonstrated with a single-shot FROG setup used to obtain the spectrograms generated from two synchronized input pulses. To demonstrate and determine the reconstruction quality for complex pulses, a programmable pulse shaper is used to modify the pulses sourced from a Kerr-lens mode-locked Ti:sapphire oscillator.

Metal‐organic frameworks (MOFs) have emerged as candidate materials for nonlinear optics due to their enhanced optical and chemical stability in comparison with conventional organic crystals. However, producing large single crystals that support perfect phase matching conditions for frequency conversion is a long‐standing challenge due to the highly metastable conditions in which MOF crystals tend to self‐assemble in solution. By modulating the synthesis and growth conditions, this limitation is overcome to produce millimeter–sized Zn(3‐ptz)2 uniaxial MOF single crystals. Optimized MOF crystals with large birefringence in the visible Δn ≈ −0.3 and high transparency allow for the observation of strong second‐harmonic (SHG) and third‐harmonic generation (THG) signals for the first time, using femtosecond near‐infrared pump pulses. For conditions of type‐I SHG phase‐matching, the measured effective nonlinear coefficient of Zn(3‐ptz)2 is deff ≈ 0.10 pm V−1, the largest measured nonlinearity for MOF materials to date. The experiments quantitatively agree with first‐principles simulations based on the crystal lattice structure. The damage threshold is estimated on the order of 0.2 TW cm−2 for raw single crystals, which can be further increased with additional crystal engineering steps. The demonstration of efficient frequency up‐conversion of light with long‐range phase coherence establishes MOF single crystals as promising materials for nonlinear optical devices.

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We report a spectrographic technique for amplitude and phase measurements of ultrashort laser pulses (above 10 fs). Pulse information is obtained directly from two different spectrograms, using the mathematical relations between Wigner–Ville function projections. Pulses are reconstructed rapidly and unambiguously without stagnation. This non-interferometric method is demonstrated experimentally for the successful characterization of 100 fs pulses.