Cylindrical Vector Beams With Topological Charges up to 6 Generated in a Raman Microchip Laser

Cylindrical vector beams (CVB) with large topological charges extend their potential applications on high security optics communications, microparticle manipulation and high-resolution imaging, which are sensitive to laser wavelength. CVBs operating at new laser wavelengths converted with stimulated Raman scattering effect in Raman solid-state lasers fulfill requirements of these potential applications. Here, CVBs in form of Laguerre-Gaussian (LG
_0,
l
) with tunable topological charges have been generated directly in an annular pumped Raman microchip laser constructed with Yb
³⁺
:Y
₃
Al
₅
O
₁₂
crystal and vanadate crystal. The topological charge is tuned from 3 to 6 by changing applied pump power. Stable LG
_0,6
CVB is obtained in Raman microchip laser when pump power is in the range from 4 to 6.1 W. Maximum output power of 420 mW is obtained for LG
_0,6
vortex Raman laser at input pump power of 6.1 W, the optical conversion efficiency is 6.8%. The state of polarization of generated CVBs with topological charge
l
is
E
_0,
l
(
φ
,
r
) =
E_φ
× sin[(
l
-1)
φ
]+
E_r
× cos[(
l
-1)
φ
],
E_φ
,
E_r
are unit vectors along azimuthal and radial directions. LG
_0,3
vortex laser oscillates in multi-longitudinal-mode around 1050 nm. LG
_0,4
and LG
_0,5
vortex lasers oscillate in 1050 nm and 1076 nm two-wavelengths. LG
_0,6
vortex laser oscillates in multi-longitudinal-mode. Polarization purity is over 95% for LG
_0,
l
(
l
= 3, 4, 5, 6) CVBs generated in the Raman microchip laser. High beam quality is achieved for CVBs with measured M
²
nearly equal to
l
+1.