Polarization-maintaining Erbium-doped Fiber Research Articles

The impact of saturable absorber recovery time on hybrid mode-locked fiber lasers with near zero net dispersion

The hybrid mode-locking scheme holds great potential in obtaining high power ultrashort laser source since it overcomes low damage threshold, self-starting difficulty in single real saturable absorber (SA) or artificial SA mode-locking scheme. Here we numerically studied the effect of SA’s recovery time on the stability of laser output in an all polarization-maintaining (PM) Erbium-doped fiber laser with hybrid mode-locking scheme, operating at the near zero net dispersion. The mapping relationship between fiber fused angles of nonlinear polarization rotation (NPR) section and different mode-locking states is demonstrated. The proportion of stable single pulse operating points increased from 7 % to more than 77 %, as the recovery time of the SA was reduced from 10 ps to 0.1 ps. The results indicate that the laser output states with hybrid mode-locking scheme could be highly affected by the SA recovery time, when the cavity net dispersion is in near zero regime.

Passively Q-switching an all polarization-maintaining erbium-doped fiber laser with a rhenium disulfide (ReS2) saturable absorber

This study demonstrates a linearly polarized Er-doped fiber laser system featuring an all-polarization-maintaining (all-PM) architecture. Short pulses were generated by Q-switching operation based on drop-casting rhenium disulfide (ReS2) saturable absorber (SA) onto a fiber connector placed inside the laser cavity. The Q-switching operation of the laser was able to self-start at a low (23 mW) threshold power of the pump and without the need to use a polarization controller. The proposed laser was able to produce stable pulses with a center wavelength and 3-dB bandwidth of 1558.4 nm and 0.13 nm, respectively. The shortest pulse duration measured (2.8 μs) was achieved at a repetition rate of 37.6 kHz while the highest average output power and pulse energy were 2.2 mW and 76.5 nJ, respectively. Furthermore, as the cavity of the laser was designed to be all-PM the laser that it produced was linearly polarized and had a degree of polarization (DOP) at the level of 94.5 % and 40 dB polarization extinction ratio (PER). Therefore, the proposed laser is a suitable light source for optical applications in environments that are complex.

Passively Q-switched mode-locking Er-doped fiber laser with tunable wavelength and pulsating soliton

A passively Q-switched mode-locking erbium-doped fiber laser with tunable wavelength and pulsating soliton is demonstrated. The polarization-maintaining erbium-doped fiber, working as the gain medium, combines with nonlinear polarization rotation to form a Lyot filter in the cavity. A tapered fiber is placed between two polarization controllers to cause a significant insertion loss in the optical path, which makes it easy to generate Q-switched mode-locking (QML) pulses. The wavelength tunable QML laser is implemented simply and easily, and the tunable wavelength ranged from 1528.05 nm to 1569.55 nm, as large as 41.5 nm. In addition, a new type of QML pulse involving pulsating soliton has been discovered in the laser, which was called Q-switched harmonic mode-locking pulsating soliton (QHML-PS). We find that the harmonic order and repetition frequency increases with the rising of the pump power. Our work has tremendous significance for expanding the research and application of emerging QML fiber lasers.

All polarization maintaining single-longitudinal-mode Brillouin/Erbium fiber laser with ultra-narrow linewidth and high stability

A high-performance all polarization maintaining (PM) single-longitudinal-mode (SLM) ring cavity Brillouin/Erbium fiber laser with an ultra-narrow linewidth, an ultra-high OSNR and high stability is investigated and experimentally demonstrated. The all-PM structure design and a stable distributed feedback fiber laser as the Brillouin pump (BP) can improve the output stability of the Brillouin/Erbium fiber laser. A short commercial PM erbium-doped fiber (EDF) serving as both the Brillouin and the linear gain media, together with the ring cavity structure of the Brillouin/Erbium fiber laser, facilitates exciting stimulated Brillouin scattering in the EDF. At the BP power of 10 mW and at the pump power of 150 mW, we obtain an SLM Brillouin/Erbium fiber laser with a linewidth as narrow as 476 Hz and an optical signal-to-noise ratio as high as 76 dB. Meanwhile, during the observation of 40 min, the lasing wavelength stability of the proposed fiber laser is 0.004 nm.

Over 10 W linearly polarized supercontinuum directly produced in an erbium-doped fiber MOPA seeded with stretched soliton.

We experimentally achieve over 10 W linearly polarized supercontinuum (SC) generation in a polarization-maintaining (PM) erbium-doped fiber (EDF) master oscillator power-amplifier (MOPA). The house-built PM seeding EDF laser can deliver ∼209fs soliton around ∼1563.7nm, which is then stretched to >15ps using a long piece of normal-dispersion fiber. The wideband spectrum of the ultrashort seeding soliton facilitates the further spectral broadening with nonlinear effects. The soliton stretching decelerates the peak power increase, thus facilitating higher amplified average power. After several stages of pre-amplification, the stretched soliton is fed into the main amplifier constructed with PM large mode area fibers. The output average power is finally amplified to ∼11.51W. The corresponding spectrum spans from ∼1450 to ∼2200nm, indicating that SC is formed due to the induced strong nonlinear effects. The polarization extinction ratio at the output reaches over 18 dB. The PM characteristic potentially enhances the system's resistance to environmental disturbances and eliminates instabilities relating to polarization-mode coupling. Our result represents, so far, the highest SC power directly produced in an EDF MOPA, to the best of our knowledge, especially in a linearly polarized manner. This also suggests a scheme for powerful SC generation that employs direct laser diode pumping and duration-managed pulse seeding.

Stable dual-wavelength laser incorporating polarization-maintaining erbium-doped fiber

A stable dual-wavelength erbium-doped fiber laser is proposed and experimentally demonstrated. The mode competition in the gain medium was suppressed by enhancing the polarization hole burning mechanism through incorporation of polarization maintaining erbium-doped fiber and nonlinear polarization rotation. The fiber laser displayed high stability with lasing side-mode suppression ratios of 60.69 and 60.57 dB. Additionally, the negligible peak power fluctuation of 0.01 dB was achieved at 1557.17 and 1560.19 nm with both peak powers of 0.23 mW and 3-dB bandwidth of 0.028 and 0.025 nm, respectively. These findings provide insights for an enhanced seed laser source design for remote dual-wavelength fiber laser applications.

全保偏掺铒光纤光梳

全保偏掺铒光纤光梳

Wavelength-spacing-controllable multi-wavelength fiber laser based on a Lyot-Sagnac filter.

A wavelength-spacing-controllable multi-wavelength polarization-maintaining erbium-doped fiber laser (MW-PM-EDFL) in a linear cavity configuration is presented based on a Lyot-Sagnac filter and a nonlinear optical loop mirror (NOLM). Using a Lyot-Sagnac filter as the wavelength selective filter makes the wavelength spacing controllable by adjusting the effective length of polarization-maintained fiber (PMF) segments. An NOLM inducing wavelength-dependent cavity loss can be used as an amplitude equalizer, which is employed to suppress the mode competition resulting from the homogeneous line broadening effect of the erbium-doped fiber in the cavity. Thus, a stable wavelength-spacing-controllable MW-PM-EDFL is realized. In this experiment, 20 stable lasing wavelengths are obtained with a pump power of 170mW at 980nm when the length of the PMF is 13m. When the length of the PMF is 8m, 10 stable lasing wavelengths are obtained at 185mW pump power. The power fluctuations and wavelength shifts are less than 2dB and 0.02nm in 1h at room temperature. The demonstrated multi-wavelength fiber laser has great potential for applications in optical communications and optical sensing systems.

All-fiber polarization-maintaining erbium-doped dispersion-managed fiber laser based on a nonlinear amplifying loop mirror

In this paper, we build a mode-locked all-polarization-maintaining figure-of-8 erbium-doped fiber oscillator based on a nonlinear amplifying loop mirror. The fiber oscillator can generate 1.6ps chirped pulses that can be de-chirped to 500fs at 1550nm with a pulse energy of 0.8nJ and a repetition rate of 12MHz. It can be further amplified up to 10nJ and compressed down to 100fs with a pre-chirp managed nonlinear amplification setup. Such an oscillator and amplifier configuration has the advantages of self-starting and long-term operation, and it is highly suitable for subsequent frequency conversion, which is desirable for many applications in ultrafast microscopy and precision spectroscopy.

Mapping Mode-Locking Regimes in a Polarization-Maintaining Er-Doped Fiber Laser

We present the performance of an all polarization-maintaining Erbium-doped fiber laser mode-locked by a multilayer graphene based saturable absorber. The cavity incorporates a Martinez-type compressor, based on a transmission grating, which allows for continuous tuning of the net cavity dispersion as well as spectral filtering. By adjusting the dispersion and the spectral bandwidth, we could operate the laser in the soliton, the dispersion managed soliton and the absorber-limited pulse regimes. The pulse durations from the laser ranged between 338 fs to 2.1 ps and the laser could be operated at nearly constant output powers in the anomalous and the normal dispersion regimes. We also conducted stability analyses based on dispersive Fourier transform measurements in the different operating regimes. Comparison of the collected spectra reveals that the soliton regime had the best overall stability.

1.7 μm band narrow-linewidth tunable Raman fiber lasers pumped by spectrum-sliced amplified spontaneous emission.

A 1.7μm band tunable narrow-linewidth Raman fiber laser based on spectrally sliced amplified spontaneous emission (SS-ASE) and multiple filter structures is proposed and experimentally demonstrated. In this scheme, an SS-ASE source is employed as a pump source in order to avoid stimulated Brillouin scattering. The ring configuration includes a 500m long high nonlinear optical fiber and a 10km long dispersion shifted fiber as the gain medium. A segment of un-pumped polarization-maintaining erbium-doped fiber is used to modify the shape of the spectrum. Furthermore, a nonlinear polarization rotation scheme is applied as the wavelength selector to generate lasers. A high-finesse ring filter and a ring filter are used to narrow the linewidth of the laser, respectively. We demonstrate tuning capabilities of a single laser over 28nm between 1652nm and 1680nm by adjusting the polarization controller (PC) and tunable filter. The tunable laser has a 0.023nm effective linewidth with the high-finesse ring filter. The stable multi-wavelength laser operation of up to four wavelengths can be obtained by adjusting the PC carefully when the pump power increases.

A Gas Cell Based on Hollow-Core Photonic Crystal Fiber (PCF) and Its Application for the Detection of Greenhouse Gas (GHG): Nitrous Oxide (N2O)

The authors report the detection of nitrous oxide gas using intracavity fiber laser absorption spectroscopy. A gas cell based on a hollow-core photonic crystal fiber was constructed and used inside a fiber ring laser cavity as an intracavity gas cell. The fiber laser in the 1.55 μm band was developed using a polarization-maintaining erbium-doped fiber as the gain medium. The wavelength of the laser was selected by a fiber Bragg grating (FBG), and it matches one of the absorption lines of the gas under investigation. The laser wavelength contained multilongitudinal modes, which increases the sensitivity of the detection system. N2O gas has overtones of the fundamental absorption bands and rovibrational transitions in the 1.55 μm band. The system was operated at room temperature and was capable of detecting nitrous oxide gas at sub-ppmv concentration level.

Stable multi-wavelength fiber laser based on a compounded nonlinear polarization rotation effect

A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) laser with high signal-to-noise ratio (SNR) based on a compounded nonlinear polarization rotation effect (CNPRE) is proposed and demonstrated. In order to effectively reduce homogeneous broadening of EDF and then to the alleviate mode competition, two sandwich configurations formed by a polarization dependent isolator (PDI) or a segment of single-mode fiber sandwiched between two polarization controllers (PC), are introduced into the ring cavity to generate the CNPRE. A home-made asymmetry twin-core fiber (ATCF) is also incorporated in the ring cavity as a comb filter. With only 150 mW pump power, there are up to 45-wavelengths lasing with the approximate amplitude in a 3 dB bandwidth generated at room temperature. The wavelength spacing between the adjacent peaks is 0.29 nm and the highest SNRs reach 41.5 dB by optimizing the state of polarization of PCs. The power fluctuation and wavelength shift for each lasing wavelength are less than 0.05 dB and 0.02 nm, respectively. This indicates that the proposed multi-wavelength fiber laser can be stably operated at room temperature.

Tunable ultra-narrow linewidth microwave generation from a double-loop Brillouin fiber laser

A simple photonic approach to generate an ultra-narrow linewidth microwave signal is proposed and experimentally demonstrated. In this scheme, a multi-wavelength Brillouin fiber laser (BFL) with a double-loop and un-pumped polarization maintaining erbium doped fiber (PM-EDF) is used. The double-loop configuration includes a 50 m long single-mode fiber (SMF) and a 10 m long SMF as Brillouin gain. The threshold and linewidth of the microwave source can be improved by using a double loop, while a 4 m long un-pumped PM-EDF is used to suppress unwanted side-modes. A dual-wavelength optical signal is heterodyned at the high-speed photo detector to produce a microwave signal by adjusting the polarization controller and the wavelength of the Brillouin pump. As a result, a tunable microwave signal from 10.605 to 10.887 GHz can be obtained. The linewidth of the microwave signal is about 14.4 kHz, and the side-mode suppression ratio is about 30 dB.

Stable, uniform, approximately linearly polarized dual-wavelength PM-EDF laser with tunable wide wavelength spacing using a compound filter

A stable uniformity approximately linearly polarized dual-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) laser obtained by using a compound filter is proposed and experimentally demonstrated. By adjusting the polarization controllers (PCs), the output laser can not only be switched between single-wavelength and dual-wavelength operation, but is also tunable. Dual-wavelength lasing has the performance characteristics of uniformity, tunable wavelength spacing, tunable wavelength position, and the same approximately linear polarization. Besides, the peak power fluctuation and wavelength shift are monitored to be less than 0.2 dB and 0.02 nm during an hour, respectively. The characteristics of the two compound filters measured in the experiment are in accord with those of a theoretical analysis.

A stable multi-wavelength PM-EDF laser based on a nonlinear amplifying loop mirror and a TCF comb filter

A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) ring cavity laser employing a twin-core fiber (TCF) comb filter and a nonlinear amplifying loop mirror (NALM) is proposed and demonstrated. By appropriately adjusting the polarization controllers, the NALM as an amplitude equalizer can effectively reduce the mode competition caused by the homogeneous broadening gain medium in the PM-EDF. Under 150 mW pump power, up to 26 wavelength outputs within a 3 dB bandwidth are achieved and their signal-to-noise ratio (SNR) is 39.5 dB. Besides, the TCF comb filter is experimentally fabricated using a length of 0.78 m TCF spliced between two segments of the single-mode fiber. The transmission spectra of the filter in experimental measurements are in accord with the results of theoretical analysis, and its wavelength spacing is 0.29 nm. Meanwhile, the power fluctuation and wavelength shift are within 0.1 dB and 0.02 nm, respectively. The experimental results indicate that the proposed multi-wavelength fiber laser performs with high stability at room temperature. In addition, the multi-wavelength laser with the TCF comb filter can offer more wavelengths in a 3 dB spectral range and higher SNR than one using a Sagnac loop filter, and the length of the filter is also reduced by more than six times.

Stable multi-wavelength PM-EDF linear cavity laser employing a TCF fiber comb filter and an SNOLM

We propose and demonstrate a stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) linear cavity laser by using a twin-core fiber (TCF) comb filter and a symmetric nonlinear optical loop mirror (SNOLM). Using a homemade TCF, we fabricate a TCF comb filter with a channel spacing of 0.29 nm. By adjusting the polarization controllers (PCs) carefully, the polarization hole-burning effect in the PM-EDF is enhanced and intensity-dependent loss is produced by a nonlinear polarization rotation effect in the SNOLM. As a result, the homogeneous broadening gain medium is effectively reduced, and the mode competition of the EDF is distinctly suppressed. With only 100 mW pump power, up to 52-wavelength stable outputs with channel spacing of 0.29 nm have been achieved at room temperature. The power fluctuation and wavelength shift for each lasing wavelength are less than 0.1 dB and 0.02 nm in an hour, respectively. Experimental results illustrate that the proposed structure of a fiber laser can realize multi-wavelength outputs with high stability at lower pump power.

Low-noise, single-frequency, single-polarization Brillouin/erbium fiber laser

We demonstrate a low-noise Brillouin/erbium fiber laser (BEFL), which uses only 1.5 m polarization-maintaining erbium-doped fiber as both the Brillouin and erbium gain media. This BEFL presents a phase noise of -125 dB/Hz(1/2) at 1 kHz frequency, at 2 mW Brillouin pump (~3 MHz linewidth) power and 200 mW 980 nm pump power. The polarization extinction ratio of the laser output light is 31 dB. Stable (~2 h) single-mode operation is observed. This BEFL presents potential applications in distributed Brillouin fiber sensors, inteferometric fiber sensors, and optical communications.

Switchable Dual-Wavelength PM-EDF Ring Laser Based on a Novel Filter

A stable and switchable dual-wavelength polarization-maintaining erbium-doped fiber ring laser is proposed and demonstrated experimentally by using a novel filter, which is formed from dual-pass Mach-Zehnder interferometer incorporating a sagnac loop. By adjusting the polarization controllers, the output laser can be switched between single- and dual-wavelength. The wavelength spacing of the dual-wavelength can be tuned from 0.084 to 4.26 nm. Its 3-dB bandwidth and side mode suppression ratio are less than 0.015 nm and higher than 64 dB, respectively. In addition, the peak power fluctuation and wavelength shift are monitored to be less than 0.5 dB and 0.01 nm during an hour, respectively. The characteristics of the novel filter in experimental measurement accord with the result of theoretical analysis.

A dual-reflected-structure switchable multi-wavelength erbium-doped fiber laser using the multi-mode fiber as the wavelength selector

A simple and effective dual-reflected-structure switchable multi-wavelength polarization-maintaining erbium-doped fiber laser is proposed and demonstrated. Using the structure of single-mode fiber (SMF)-multi-mode fiber (MMF)-SMF as the wavelength selective filter and reflector simultaneously the polarization-maintaining erbium-doped fiber as the gain medium and an optical circulator as the all-reflecting mirror, the laser realizes stable single-wavelength, dual-wavelength and triple-wavelength oscillations based on polarization hole burning of a multi-mode fiber by means of adjusting the polarization controller. The 3 dB bandwidth is about 0.01 nm. The side-mode suppression ratios (SMSRs) are over 50 dB. The power fluctuation and wavelength shifts are measured to be less than 1.5 dB and 0.01 nm over an hour at room temperature.