Twisted Light in a Single‐Crystal Fiber: Toward Undistorted Femtosecond Vortex Amplification

Abstract

Intense femtosecond optical vortices with spatially structured amplitude and spiral phase front give rise to novel phenomena in light-matter interactions and strong-field physics. However, current femtosecond vortex sources exhibit a poor power handling capability and amplification remains an open challenge due to a number of inherent technical difficulties. Here, it is demonstrated that a single-crystal fiber laser amplifier is particularly well-suited to directly amplify a femtosecond optical vortex without pulse stretching and compression in the time domain, while still maintaining the spatial properties associated with a clear central singularity and a spiral phase front, i.e., a well-defined amount of orbital angular momentum (OAM).The optical nonlinearity experienced by such twisted light is verified to be substantially weaker compared to a fundamental mode beam where supercontinuum generation and spatial distortion are observed. The simple design and straightforward power scaling capability pave the way toward ultrahigh-intensity femtosecond singular laser sources with an arbitrary topological charge. Such ultrafast OAM light sources are expected to help reveal complex physical phenomena in light-matter interactions and expand the applications to attoscience with X-ray vortices, laser plasma acceleration, and micromachining.

Controlled Generation of High‐Purity Scalar Orbital Angular Momentum States from a High‐Power Single‐Crystal Fiber Laser

“…This contrasts with conventional bulk crystals, in which this part of the active element typically causes reabsorption. [36] This was further confirmed by comparing the on-axis intensity dependence along the SCF with the unguided case. As shown in Figure 2c, although there is no significant difference in the initial free-space propagation part before the bifurcation point at Z = 15 mm, beyond this point, the intensity ratio (I/I max ) in the guided case increases noticeably and fluctuates between 0.15 and 0.37.…”

“…Our demonstrated power-scalable, high-purity scalar OAM laser with a compact structure and controllable states can open new avenues for practical applications, such as optical manipulation, [8,9] optical communication, [3,4] and the study of the linear spin-orbital coupling of light. [62] The high gain of the SCF laser, [36] along with the robust architecture featuring a collimated beam segment in the cavity, allows the spatial structures and temporal characteristics of the light beam to be easily controlled or modulated at the source. For example, further power scaling of the optical vortices to hundreds of watts can be achieved using dual-end pump configurations or multi-stage SCFs with longer and thinner geometries.…”

High-efficiency tandem Ho:YAG single-crystal fiber laser delivering more than 100 W output power

“…Note that, the concept of SCF is somewhat misleading but already established, referring to fiber-like thin-crystal rods with a large surface-to-volume-ratio and characterized by a diameter of less than 1 mm and a length of few centimeters. Some reports in the 1-μm spectral region, e.g., 250 W CW laser from a compact resonant cavity [33] and an average power of 290 W with 829 fs pulses in a two-stage amplifier [34] based on Yb-doped YAG SCFs and so on [35][36], all these demonstrations indicate that SCFs are ideal gain media for high average/peak power laser oscillators/amplifiers. However, there have been relatively few studies on high-power SCF lasers in the 2-μm spectral range to date.…”

Efficient Direct Laser Generation by Three‐Phonon‐Assisted Transition with Yb:YCOB Crystal

“…Laser wavelength is an important parameter for the laser applications, and it is usually determined by the electronic transition among the inherent Stark levels of active ions. [1][2][3] Generally, the Stark splitting values of electronic levels depend on the crystal field intensity, as well as the microscopic symmetry of active doped ions and surrounding lattices. When lattice vibrations are involved, electron-phonon-coupling effect can homogeneously broaden the emission spectrum and greatly extend the laser wavelengths around fluorescence sidebands, even beyond.…”