Kegui Xia

Efficient, high-power, and radially polarized fiber laser

We demonstrate an ytterbium-doped fiber laser that emits high-power radially polarized light efficiently. In this study, a photonic crystal grating (PCG) was used as a polarization-selective output coupler, and the power of the radially polarized laser reached 2.42 W with a slope efficiency of 45.9% and a polarization purity of 96%. The results reveal that the inclusion of the PCG mirror into the fiber laser are particularly promising for generating high-power radially polarized light efficiently in view of its many important applications.

Radially polarized and passively Q-switched fiber laser

We report, for the first time to our knowledge, a radially polarized and passively Q-switched Yb-doped fiber laser. By using a Cr(4+):YAG crystal as a saturable absorber and a photonic crystal grating as a polarization mirror, a radially polarized pulse is produced, which has 202 W of peak power, 75 ns duration, and ~92% polarization purity at a 56.6 kHz repetition rate. The Q-switched pulse with radial polarization from the fiber laser would facilitate numerous applications.

Radially Polarized and Passively Q-Switched Nd:YAG Laser Under Annular-Shaped Pumping

We reported, for the first time, a radially polarized and passively Q-switched Nd:YAG laser with annular-shaped pumping. The annular intensity profile of the pump light was originated from the mode conversion in a conventional multi-mode fiber under off-focus coupling. Radially polarized pulse from this laser had 3.3 kW peak power, 39 ns duration at 2.5-kHz repetition rate with ~90% degree of polarization. When the laser crystal was slightly tilted, the polarization state of laser beam was switched to azimuthal polarization at high pump power, while remained radial polarization at lower pump power.

Efficient Vortex Laser With Annular Pumping Formed by Circle Dammann Grating

We proposed and demonstrated an efficient vortex Nd:YVO4 laser under the utilization of a circle Dammann grating (CDG). As a simple binary-phase component, CDG was inserted into the pump unit of this laser-diode end-pumped solid-state laser and reshaped the pump radiation into annular profile with high efficiency. Moreover, such utilization of CDG avoided additional modification to laser cavity. As a result, the laser emitted vortex beam with a high slope efficiency of 51% and a maximum beam power of 554 mW at 1.75-W incident pump power.

Transverse mode transition and LG01-mode generation in an end-pumped Nd:YVO4 laser

A laser-diode end-pumped Nd:YVO4 crystal laser is demonstrated to emit the first-order Laguerre-Gaussian (LG01) mode with 502-mW laser power and 22% slope efficiency. The LG01-mode is lased only when the pumping area locates in the central part of the laser crystals front surface, and thereafter the symmetrical LG01-HG01-TEM00 mode transition happens when laser crystal is moved laterally inside several-tens-micron area. The possible mechanism responsible for the phenomenon of symmetrical mode transition is also discussed.

Efficient emission of Laguerre-Gaussian beam from Nd-doped Yttrium Vanadate laser

An laser-diode (LD) end-pumped Nd-doped Yttrium Vanadate (Nd:YVO₄) laser was demonstrated to emit the first order Laguerre-Gaussian (LG₀₁) mode. This LG₀₁-mode laser is compact and efficient.

Multiple-beam Nd:YVO 4 laser based on Dammann grating

An arrayed-output Nd:YVO4 laser is demonstrated in which the collimated pumping light is split into 2×2 array by a Dammann grating and thus forms four independent pumping areas in one single laser crystal.

Self-polarized ytterbium-doped f iber laser

We demonstrate a linearly-polarized, ytterbium-doped fiber laser that uses an uncoated, undoped ceramic YAG plate as the output coupler, and the corresponding polarization extinction ratio of laser beam increases with incident pump power and then saturates at larger pump power. For comparison, the output coupler of the fiber laser is replaced by 10% reflectivity plane mirror, while the feature of the polarization of laser output is kept unchanged. The results show that the origin of the pump-dependent and self-started polarization is associated with the intensity-dependent nonlinear birefringence in the gain fiber.