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Ultrafast vortex beams have significant scientific and practical value because of their unique phase properties in both the longitudinal and transverse modes, enabling multi‐dimensional quantum control of light fields. Directly generating watt‐level ultrafast vortex beams with large angular momentum has remained a major challenge due to the limitations of mode‐locked materials and existing spatiotemporal mode‐locking generation methods. In this study, quasi‐2D PEA2(CsPbBr3)n‐1PbBr4 perovskite films are prepared by an anti‐solvent method and employed for the first time in a mode‐locked resonator operating in free space. Utilizing the angle‐based non‐collinear pumping and frequency doubling techniques, the second‐order ultrafast green vortex beams with a power of up to 1.05 W and a duration of 373 ps are generated. Experimental findings demonstrate the strong nonlinear saturable absorption properties of quasi‐2D PEA2(CsPbBr3)n‐1PbBr4 perovskite films at high power levels, highlighting their considerable potential in ultrafast laser technology and nonlinear optics. [ABSTRACT FROM AUTHOR]

This work report the generation of high‐order Laguerre–Gaussian (LG) modes from a nanosecond, optical vortex pumped diamond Raman laser. This system is capable of generating first‐Stokes (λ1st = 1240 nm) LG modes with topological charge (ℓ) of up to 26 and second‐Stokes (λ2nd = 1485 nm) LG modes with topological charge of up to 22, when pumped using a first‐order vortex beam. The maximum first‐ and second‐Stokes LG mode energies are measured to be 0.5 and 1 mJ, respectively, when pumping with energy of 19.8 mJ. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) is an effective method for compensating wavefront aberrations in high-energy lasers due to its phase conjugation property. However, SBS phase conjugate mirrors (SBS-PCMs) under high-power pumping often suffer from significant spatial aberrations and decreased energy reflectivity, indicating instability in the nonlinear gain. Here, a nonlinear gain modulation method is proposed to realize the stable output. Experiments show that the energy reflectivity of SBS decreased due to the thermal effect in high-repetition-rate pumped SBS-PCMs. The nonlinear gain modulation was accomplished with simultaneous adaptation of radial and axial focusing parameters resulting in a higher SBS gain under short-focus conditions. The feasibility of the method was experimentally confirmed by obtaining SBS energy reflectivity stabilized at 60%, while the root mean squares of steady-state Stokes energy and pulse time delay enhanced to 1.97% and 1.81%, respectively, in an HT-230 medium. This scheme ensures stable and efficient SBS output under high-power pumping, which is of great significance for expanding the application of SBS-PCMs in high-repetition-rate laser systems. [ABSTRACT FROM AUTHOR]

The lead halide perovskite material shows its unique photoelectric properties, the resulting conversion efficiency of perovskite solar cells. However, the efficiency comes to a bottleneck owing to that mechanism research fall behind the device research. Multiple excitons dynamics play an important role, especially in the lifetime and binding energy of multiple excitons. A long multiexciton lifetime is beneficial to the application for light-emitting devices and photovoltaic devices. Large multiexciton binding energy means a large Stokes shift in exciton absorption, thus avoiding the loss of linear absorption. To conclude, discussions are presented regarding views of current multiple excitons research in terms of the biexciton lifetime and biexciton binding energy that should be considered for further advances in materials and devices.

Raman amplification is a highly efficient means by which amplification of laser radiation and beam clean-up can be achieved. Although this process has been described in the literature, little attention has been given to the investigation of pulse characteristics of the laser fields involved in the process. In this work, we analyze the evolution of the fundamental and Stokes fields involved in the Raman amplification process, with a focus on Stokes extraction efficiency within a diamond Raman amplifier. This work offers insight into the means by which the Raman amplification process can be optimized/maximized for a given set of laser fields. Experimental observations show that depletion of the fundamental field occurs during the amplification process, causing an initially Gaussian pulse shape to become increasingly concave. The rate at which the pulse peak diminishes and the overall shape becomes concave is correlated with the rate of amplification of the Stokes field pulse intensity. This experimental observation is supported by theoretical modeling using rate equations wherein Raman amplification under different initial conditions is numerically simulated, and the energy extraction efficiency and pulse shapes under different intensities are analyzed. Experimentally, the amplified laser output of the Stokes field from this system is 4.2 mJ (equivalent to a peak power of up to 37.5 kW), and an amplification efficiency of 18% is achieved. [ABSTRACT FROM AUTHOR]

High-order vortex beams carrying orbital angular momentum in the visible wavelength range are of tremendous interest for a diversity of applications, including super-resolution imaging, microfabrication, and underwater communications. Such beams can be generated directly from compact solid-state lasers; however, they generally have low topological charge number. In this work, we demonstrate the generation of high-order Laguerre–Gaussian (LG) modes from a simple Pr:YLF laser cavity and demonstrate its application in the measurement of angular velocity. We utilize enhanced intracavity spherical aberration to generate LG0,±m modes with m selectable up to 34, directly from a Pr:YLF laser operating at 640 nm. We utilize this laser beam in an off-axis illumination geometry in conjunction with the rotational Doppler effect, to measure the angular velocity of a spinning object. The demonstration highlights a potential application for these types of vortex laser. [ABSTRACT FROM AUTHOR]