Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sub-femtosecond synchronization of microwave oscillators with
  mode-locked Er-fiber lasers   We synchronize a 8.06-GHz microwave signal from a voltage-controlled
oscillator with an optical pulse train from a 77.5- MHz mode-locked Er-fiber
laser using a fiber-based optical-microwave phase detector. The residual phase
noise between the optical pulse train and the synchronized microwave signal is
-133 dBc/Hz (-154 dBc/Hz) at 1 Hz (5 kHz) offset frequency, which results in
838 as integrated rms timing jitter [1 Hz - 1 MHz]. The long-term residual
phase drift is 847 as (rms) measured over 2 hours, which reaches
4\times10^{-19} fractional frequency instability at 1800 s averaging time. This
method has a potential to provide both sub-fs-level short-term phase noise and
long-term phase stability in microwave extraction from mode-locked fiber
lasers.

8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg