  We develop an optical tweezers system using a single dual-mode optical fiber
where mesoscopic absorbing particles can be trapped in three dimensions and
manipulated employing photophoretic forces. We generate a superposition of
fundamental and first order Hermite-Gaussian beam modes by the simple
innovation of coupling a laser into a commercial optical fiber designed to be
single mode for a wavelength higher than that of the laser. We achieve robust
trapping of the absorbing particles for hours using both the pure fundamental
and superposition mode beams and attain large manipulation velocities of ~5
mm/s in the axial direction and ~0.75 mm/s in the radial direction. We then
demonstrate that the superposition mode is more effective in trapping and
manipulation compared to the fundamental mode by around 80%, which may be
increased several times by the use of a pure first order Hermite-Gaussian mode.
The work has promising implications for trapping and spectroscopy of aerosols
in air using simple optical fiber-based traps.
