Phase-matching-free pulse retrieval based on transient absorption in solids

Abstract

In this paper, we introduce a pulse characterization technique that is free of phasematching constraints, exploiting transient absorption in solids as an ultrafast optical switch. Based on a pump-probe setup, this technique uses pump pulses of sufficient intensity to induce the switch, while the pulses to characterize are probing the transmissivity drop of the photoexcited material. This enables the characterization of low-intensity ultra-broadband pulses at the detection limit of the spectrometer, and within the transparency range of the solid. For example, by using zinc selenide (ZnSe), pulses with wavelengths from 0.5 to 20 µm can be characterized, denoting five octaves of spectral range. Using ptychography, we retrieve the temporal profiles of both the probe pulse and the switch. To demonstrate this approach, we measure ultrashort pulses from a titanium-sapphire (Ti-Sa) amplifier which are compressed using a hollow core fiber setup, as well as infrared to mid-infrared pulses generated from an optical parametric amplifier (OPA). The characterized pulses are centered at wavelengths of 0.77, 1.53, 1.75, 4, and 10 µm, down to sub-two optical cycles duration, exceeding an octave of bandwidth, and with energy as low as a few nanojoules.

Characterizing the carrier-envelope phase stability of mid-infrared laser pulses by high harmonic generation in solids

“…2). [49]. To perform this FROSt measurement, a few-J of energy of the mid-IR beam is focused with a 5mm off-axis parabola onto a 300 m thick germanium (Ge) plate.…”

“…The experimental and reconstructed (with a phase retrieval algorithm, see ref. [49]) spectrograms for the three relative CEP are shown in Fig. 1d.…”

Single-shot phase-matching free ultrashort pulse characterization based on transient absorption in solids

“…At this position, the pump fluence is sufficient to create a transient absorption switch that changes rapidly the transmission properties of the material. This mechanism, at the core of the FROSt characterization technique, was reported previously [14,18]. The optical beam path of the pump is adjusted with a translation stage to t 0 (y 2 ) ∼ 0, so that the switch transition coincides with the center of the probe beam ( Fig.…”

“…Nevertheless, there is still a need for reliable diagnostics specifically adapted to low repetition rate and broadband laser systems, potentially operating under vacuum [10][11][12][13]. Here, we report on the basic implementation of the single-shot frequency resolved optical switching (FROSt) technique, previously developed in our group [14], in a configuration enabling the complete characterization of ultrashort pulses in a single shot. FROSt is a phase-matching free pulse characterization technique associating transient absorption to ptychographic reconstruction for pulse retrieval.…”

High-field mid-infrared pulses derived from frequency domain optical parametric amplification

“…3d. The pulses are temporally characterized with the Frequency Resolved Optical Switching (FROSt) technique 28 . To perform this measurement, a few-µJ of energy of the mid-IR beam is focused with a 5mm off-axis parabola onto a 300 µm thick germanium (Ge) plate.…”