Kerr-lens mode-locked Cr:ZnS laser

Abstract

Received Month X, XXXX; revised Month X, XXXX; accepted Month X, XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX We report the soft-aperture Kerr-lens mode-locked Cr:ZnS laser, generating 550 mW of 69-fs nearly transform-limited pulses at 2.39 µm wavelength. The pulse energy reached 3.8 nJ at 145 MHz repetition rate, limited by the onset of doublepulsing. This corresponds to the shortest-pulse and highest-energy direct femtosecond laser source in the mid-IR. Dispersion compensation was achieved by a single chirped mirror and a thin sapphire plate, making the laser design simple, compact and very stable, operating at ambient air and room temperature. The superb thermal and mechanical properties of Cr:ZnS, exceeding those of Cr:ZnSe and many established femtosecond laser crystals should allow further scaling of output power.

Chaotic chirped-pulse oscillators

“…In this paper, we describe and characterize the observed chaotic regimes in the chirpedpulse Cr:ZnS and Cr:ZnSe lasers [10,11] and confirm our physical model with the numerical simulations. We demonstrate that the chaotic mode-locking in a solid-state oscillator results from a parametric resonance with dispersive waves, having different signature and mechanism than observed in the fiber lasers [5][6][7][8][9].…”

“…The Brewster-mounted diffusion-doped Cr:ZnS crystal was passively cooled by a copper heatsink. The laser was operated at average output powers of 35-70 mW resulting in the output pulse energies of 0.25-0.5 nJ (15-30 nJ intracavity energy), though much higher output power could be achieved in this cavity both in femtosecond regime [10] and in CPO regime [12]. A pair of Brewster-oriented YAG wedges provided continuous tuning of the second-order dispersion (GDD) with the constant TOD at +8200 fs 3 .…”

Chaotic regime in chirped-pulse mid-IR oscillators

“…In this paper, we describe and characterize the observed chaotic regime in the Cr:ZnS and Cr:ZnSe lasers [6,7] and confirm our physical model with the numerical simulations. We demonstrate that the origin of chaotic modelocking in a solid-state oscillator results from a parametric resonance with dispersive wave, having different signature and mechanism than observed in the fiber lasers [5].…”

Femtosecond Cr:ZnS laser at 2.35 μm mode-locked by carbon nanotubes

“…No active cooling was applied to the crystal. As Cr:ZnS exhibits quite high nonlinearity (8), the pulse energy of the femtosecond Cr:ZnS laser is usually limited by the nonlinearity of the active element (9)(10)(11)(12). In order to extract maximum average output power from the laser, and at the same time keep the pulse energy under the nonlinearity limit, the cavity length was kept around 120 cm, which corresponds to the pulse repetition frequency around 250 MHz.…”