Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Intracavity Optical Trapping   Standard optical tweezers rely on optical forces that arise when a focused
laser beam interacts with a microscopic particle: scattering forces, which push
the particle along the beam direction, and gradient forces, which attract it
towards the high-intensity focal spot. Importantly, the incoming laser beam is
not affected by the particle position because the particle is \emph{outside}
the laser cavity. Here, we demonstrate that \emph{intracavity nonlinear
feedback forces} emerge when the particle is placed \emph{inside} the optical
cavity, resulting in orders-of-magnitude higher confinement along the three
axes per unit laser intensity on the sample. We present a toy model that
intuitively explains how the microparticle position and the laser power become
nonlinearly coupled: The loss of the laser cavity depends on the particle
position due to scattering, so the laser intensity grows whenever the particle
tries to escape. This scheme allows trapping at very low numerical apertures
and reduces the laser intensity to which the particle is exposed by two orders
of magnitude compared to a standard 3D optical tweezers. We experimentally
realize this concept by optically trapping microscopic polystyrene and silica
particles inside the ring cavity of a fiber laser. These results are highly
relevant for many applications requiring manipulation of samples that are
subject to photodamage, such as in biological systems and nanosciences.

17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph