A carrier-envelope-phase-stable near-single-cycle mid-infrared laser based on optical parametric chirped pulse amplification and hollow-core fiber compression is demonstrated. A 4 μm laser pulse with 11.8 mJ energy is delivered from a KTA-based optical parametric chirped pulse amplification (OPCPA) with 100 Hz repetition rate, and compressed to 105 fs by a two-grating compressor with efficiency over 50%. Subsequently, the pulse spectrum is broadened by employing a krypton gas-filled hollow-core fiber. Then, the pulse duration is further compressed to 21.5 fs through a CaF bulk material with energy of 2.6 mJ and energy stability of 0.9% RMS, which is about 1.6 cycles for a 4 μm laser pulse. The carrier envelope phase of the near-single-cycle 4 μm laser pulse is passively stabilized with 370 mrad.

We demonstrate in this Letter the generation of carrier-envelope-phase (CEP)-stabilized laser pulses at 910 nm with simultaneously high-temporal-contrast, broad spectral bandwidths and few-cycle pulse durations. Through combining the techniques of cascaded optical parametric amplification (OPA) and second-harmonic generation (SHG) in the laser setup, a pulse temporal contrast as high as > 10 12 has been obtained at the laser output. During the OPA and SHG processes, both the pulse chirp and gain bandwidth are perfectly optimized, leading to the generation of 170 µJ pulses with > 200 n m bandwidth and ∼ 15 f s pulse duration. Moreover, the CEP of the laser is stabilized passively to a noise level of less than 340 mrad. This high-quality pulsed light source, as the seed laser of the deuterated potassium dihydrogen phosphate (DKDP)-based 100 PW system, will be integrated into the Station of Extreme Light facility in the near future.

Ultrafast all-optical switches based on epsilon-near-zero (ENZ)-enhanced nonlinear refraction in transparent conducting oxides have achieved exciting results in realizing large absolute modulations. However, broad-band, polarization-independent, and wide-angle ultrafast all-optical switches have been challenging to produce, due to the inherent narrow band, polarization-dependent, and angle-dependent characteristics of the ENZ effect. To this end, we propose an ultrafast all-optical switch based on the enhanced nonlinear absorption of corrugated indium tin oxide (ITO) thin films. Taking advantage of the perfect absorption and localized field enhancement of the ENZ and localized surface plasmon resonance modes, we significantly enhanced the nonlinear absorption of the corrugated ITO film in the 1450–1650 nm telecom band. The experimental results show that the nonlinear saturable absorption coefficient of the corrugated ITO film at 1450 nm was as high as −1.5 × 105 cm GW–1, enabling all-optical switching to obtain an extinction ratio of 14.32 dB and an ultrafast switching time of 350 fs at a pump fluence of 18.51 mJ cm–2. Furthermore, the all-optical switch achieved an extinction ratio of over 15 dB and an insertion loss of approximately 2.6 dB within the 200 nm absorption band and exhibited polarization-independent and wide-angle features. The ultrafast temporal response can be attributed to intraband transient bleaching of the corrugated ITO film. Our findings demonstrate that corrugated ENZ films can overcome the inherent narrow-band, polarization-dependent, and angle-dependent problems of natural ENZ materials without increasing the response time, making them a potential ENZ ultrafast all-optical switching material platform.

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Here, we report the recent progress on the front end developed for the 100 PW-class laser facility. Using 3 stages of optical parametric chirped-pulse amplification (OPCPA) based on lithium triborate (LBO) crystals, we realized a 5.26 J/0.1 Hz amplified output with a bandwidth over 200 nm near the center wavelength of 925 nm. After the compressor, we obtained a pulse duration of 13.4 fs. As the compression efficiency reached 67%, this OPCPA front end could potentially support a peak power of 263 TW at a repetition rate of 0.1 Hz. To the best of our knowledge, among all the 100 TW-level OPCPA systems, it shows the widest spectral width, the shortest pulse duration, and it is also the first OPCPA system working at a repetition-rate mode.

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