Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multiple quantum wells for passive ultra short laser pulse generation   Solid state lasers are demanding independent control in the gain media and
cavity loss to achieve ultra short laser pulses using passive mode-locking.
Recently, laser mode-locking is achieved with a MBE structure with multiple
quantum wells, designed to achieve two functions; Bragg mirror and changes in
absorption to control the cavity dynamics. The use of an AlGaAs/AlAs Bragg
mirror with a 15 nm GaAs saturable absorber used in a Cr:LiSAF tuneable laser
proved to be effective to produce femtosecond pulses. The use of saturable
absorbers thus far is a trial and error procedure that is changing due to the
correlation with more predictive procedures.

15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
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The categories of this paper are: eess
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg