Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Black phosphorus Q-switched and mode-locked Er:ZBLAN fiber lasers at 3.5
  um   With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber
lasers at 3.5 um have become a fascinating area of research. However, limited
by the absence of suitable saturable absorber, passively Q-switched and
mode-locked fiber lasers have not been realized in this spectral region. Based
on the layer-dependent bandgap and excellent photoelectric characteristics of
black phosphorus (BP), BP is a promising candidate for saturable absorber near
3.5 um. Here, we fabricated a 3.5-um saturable absorber mirror (SAM) by
transferring liquid-phase exfoliated BP flakes onto a gold-coated mirror. With
the as-prepared BP SAM, we realized stable Q-switching and continuous-wave
mode-locking operations in the DWP Er:ZBLAN fiber lasers at 3.5 um. To the best
of our knowledge, it is the first time to achieve passively Q-switched and
mode-locked pulses in 3.5 um spectral region. The research results will not
only promote the development of 3.5-um pulsed fiber lasers but also open the
photonic application of two-dimensional materials in this spectral region

30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn