Polarization-multiplexed, dual-comb all-fiber
mode-locked laser
XIN ZHAO,
1
TING LI,
1
YA LIU,
1,2
QIAN LI,
1
AND ZHENG ZHENG
1,3,4,
*
1
School of Electronic and Information Engineering, Beihang University, Beijing 100083, China
2
Yunnan Key Laboratory of Opto-Electronic Information Technology, School of Physics and Electronic Information Technology,
Yunnan Normal University, Kunming 650500, China
3
Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beihang University, Beijing 100083, China
4
Collaborative Innovation Center of Geospatial Technology, Wuhan 430079, China
*Corresponding author: zhengzheng@buaa.edu.cn
Received 13 April 2018; revised 26 June 2018; accepted 8 July 2018; posted 11 July 2018 (Doc. ID 328118); published 8 August 2018
Mode-locked fiber lasers that can simultaneously generate two asynchronous ultrashort pulse trains could play an
attractive role as the alternative light sources for low-complexity dual-comb metrology applications. Although a
few multiplexing schemes to realize such lasers have been proposed and demonstrated, here we investigate the
lasing characteristics of a passively mode-locked fiber laser with a finite amount of intracavity birefringence. By
introducing a section of polarization-maintaining (PM) fiber into the otherwise-non-PM-single-mode cavity, dual
asynchronous pulses with nearly orthogonal states of polarization are generated. With a repetition rate difference
of hundreds of hertz, the pulses have well-overlapped spectra and show typical features of polarization-locked
vector solitons. It is demonstrated that under an anomalous or net normal dispersion regime, either dual vector
solitons or dual dissipative vector solitons can be generated, respectively. Such polarizati on-multiplexed single
single-cavity dual-comb lasers could find further uses in various applications in need of simple dual-comb system
solutions.
© 2018 Chinese Laser Press
OCIS codes: (140.4050) Mode-locked lasers; (140.7090) Ultrafast lasers; (060.3510) Lasers, fiber.
https://doi.org/10.1364/PRJ.6.000853
1. INTRODUCTION
Two optical frequency combs with slightly different comb-
tooth spacing can enable a number of dual-comb metrology
applications [1], such as high-resolution spectroscopy and rang-
ing. Because the traditional implementations based on two
frequency-stabilized ultrafast lasers [2] are considered by many
as overly complicated or technically challenging, the efforts to
simplify such systems have intensified in the past few years.
Using two free-running mode-locked lasers, digital phase
correction algorithms or adaptive-sampling data acquisition
systems can compensate their repetition rate drifts [3,4]. It was
also found that sharing one common optical parametric oscil-
lator cavity for wavelength-conversion of the pulses from two
free-running seed lasers could improve the dual-comb spectros-
copy measurement performance [5] by reducing the random
drifts in two cavities. The outputs from two mode-locked wave-
guide lasers [6] or nonlinear microresonators [7] fabricated and
operated on the same chip had been shown to possess sufficient
mutual coherence for certain dual-comb applications with large
comb-tooth spacing. Two electro-optic combs seeded by one
continuous-wave (CW) laser followed by nonlinear spectral
broadening had been applied to spectroscopic measurement
by setting slightly different modulation frequencies [8]. While
having flexible choices of the center wavelength and comb-
tooth spacing, a compromise between their comb-tooth spacing
and spectral bandwidth could exist.
Generating dual-comb pulses directly from one seed cavity
instead of two, however, seems to be an attractive and prom-
ising approach because of the possible higher degree of mutual
coherence between the pulses. There had been increasingly
strong interest in realizing such a single-cavity dual-comb
source (SCDCS) on various laser platforms. Several schemes
of generating asynchronous ultrashort pulses from a mode-
locked fiber laser have been demonstrated by leveraging dual-
wavelength [9], bidirectional [10–12] lasing, or nonlinear
pulse-shaping mechanisms [13]. Dual-comb pulse generation
had also been realized in a bidirectionally oscillating Ti:sapphire
laser [14] as well as a bidirectionally pumped microresonator
[15]. Orthogonally polarized dual-comb generation was also
achieved in a semiconductor disk laser by spatially separating
the beam paths in the cavity with a birefring ent crystal [16].
Such SCDCSs with asynchronous pulse emissions had demon-
strated their potential in several dual-comb applications as
simple, alternative dual-comb sources [17–21]. Among them,
Research Article
Vol. 6, No. 9 / September 2018 / Photonics Research 853
2327-9125/18/090853-05 Journal © 2018 Chinese Laser Press