Off-axis pumped Nd:YAG/Cr4+:YAG lasers under degenerate cavity conditions are explored to achieve high-pulseenergy geometric modes for beam transformation. The employment of Nd:YAG crystal promises efficient passively Qswitched (PQS) operation with a flexible cavity length to ensure various PQS geometric modes with stable structures can be generated. It is experimentally confirmed that the output energy and peak power of the PQS geometric modes can easily reach up to over 100 μJ and 10 kW with fairly stable pulse trains in pure linear polarization. Various high-energy vortex beams carrying large angular momentum and diverse phase structures are achieved by converting the planar geometric modes into the circular ones to offer promising light sources for potential applications.
Theoretical wave functions are analytically derived to formulate the propagation evolution of the Hermite-Gaussian (HG) beams transformed by single lens astigmatic mode converter with arbitrary angle. The derived wave functions are associated with the combination of the rotation transform and the antisymmetric fractional Fourier transform. The derived formula are validated by the mode conversions of high-order HG beams generated by an off-axis diode-pumped solidstate laser. In addition to validation, the creation and evolution of vortex structures in the transformed HG beams are numerically manifested. The present theoretical model can be applied not only to characterize the evolution of the transformed beams but to design the optical vortex beams with various forms.
We originally perform an analytical form to explore the influence of the astigmatism on the degenerate effect in nearly
hemispherical cavities. The frequency spectrum near hemispherical cavities clearly reveals that not only the difference of
cavity lengths between each degeneracies but also frequency gaps have significant difference from non-hemispherical
cavities. We further thoroughly demonstrate the laser experiment under the condition of nearly hemispherical cavities to
confirm the theoretical exploration that the transverse topology of three-dimensional (3D) structured light in the
degenerate cavities is well localized on the Lissajous curves.
We employ an intracavity self-mode-locked laser to systematically measure the group refractive indices and the thermo-optic coefficients for Nd:GdVO4, Nd:YVO4 and Nd:LuVO4 crystals at 1064 nm. We further make a detailed comparison between the present results and those currently reported in the literature. All the experimental results can be found to be fairly consistent with the recent reported data
We report a low-temperature 1.3μm AlGaInAs quantum-well laser pumped by a 1.06μm active
Q-switched laser quenched by a low-temperature vacuum system. An average power of 330mW is
achieved at temperature as low as 233K compared to the average power of 50mW obtained at
room-temperature without cooling device both at pumping repetition rate of 30 kHz. And the average
rate of gain peak shift was found to be 0.47 nm/K between 293-133 K.
We report the use of AlGaInAs quantum wells (QWs) as a saturable absorber in the
Q-switching of a high-power diode-pumped Nd-doped 1064nm laser. The barrier layers are
designed to locate the QW groups in the region of the nodes of the lasing standing wave for
avoiding damage. With an incident pump power of 22 W at 878nm, an average output power of
6.8 W with a Q-switched pulse width of 0.85 ns at a pulse repetition rate of 105kHz was obtained.
We demonstrate an AlGaInAs saturable absorber with a periodic quantum wells (QWs)/barrier structure that can be
used to achieve an efficient high-peak-power and high-pulse-energy passively flashlamp-pumped Q-switched Nd:YAG
laser at 1.06 um. The barrier layers are designed to locate the QW groups in the region of the nodes of the lasing standing
wave to avoid damage. With an incident pump voltage of 14.5 J, a single pulse was generated with a pulse energy of 14
mJ and a Q-switched pulse width of 13 ns. The maximum peak power was greater than 1.08 MW.
The efficient stimulated Raman scattering conversion in a diode-pumped actively Q-switched Nd:YAG laser was
achieved with an undoped YVO4 crystal as a Raman shifter. With an incident pump power of 16.2 W, 1176-nm first
Stokes average output power of 2.97 W was generated at a pulse repetition rate of 50 kHz. The maximum pulse energy
is higher than 83 μJ at both 20 kHz and 30 kHz. With mode-locked modulation, the effective pulse width far above
threshold is usually below 5 ns. With an incident pump power of 7.62 W, the peak-power of 43.5 kW was demonstrated
at 20 kHz.
An analytical model has been developed to minimize the effective mode area in a saturable absorber for an
external-cavity passively Q-switched fiber laser. Under the condition of minimum effective mode size inside the
saturable absorber, the analytical expressions for two key parameters of an optimum system have been derived. One
parameter is the optimum focal position that is analytically derived to be a function of the thickness and initial
transmission of the saturable absorber. The other parameter is the optimum magnification of the re-imaging optics that
is analytically derived to be in terms of the numerical aperture and core radius of the laser fiber as well as the thickness
and initial transmission of the saturable absorber. The present model provides a straightforward procedure to adopt a
focusing system for the output performance. A diode-pumped ytterbium-doped fiber lasers with a Cr:YAG crystal as a
saturable absorber is considered to illustrate the utility of the present model
We report a high-peak-power AlGaInAs 1.36-μm vertical-external-cavity surface-emitting laser (VECSEL)
optically pumped by a diode-pumped actively Q-switched Nd:GdVO4 1.06-µm laser under room-temperature operation.
The gain medium is an AlGaInAs quantum wells (QWs)/barrier structure grown on a Fe-doped InP substrate by
metalorganic chemical-vapor deposition. With an average pump power of 1.9 W, an average output power of 340 mW
was obtained at a pulse repetition rate of 40 kHz, corresponding to an optical-to-optical conversion efficiency of 18.76%.
With a peak pump power of 7.9 kW, the highest peak output power was 1.3 kW at a pulse repetition rate of 10 kHz.
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