Dual-wavelength Fiber Laser Research Articles

Sideband-free tunable and switchable dual-wavelength mode-locked fiber laser based on the Lyot filter and spontaneous radiation peaks.

We demonstrate a compact tunable and switchable dual-wavelength fiber laser based on the Lyot filtering effect and the spontaneous radiation peaks of gain fiber. By introducing a period of polarization-maintain Er-doped fiber (PM-EDF), stable dual-wavelength pulses can operate in both the anomalous dispersion region and the normal dispersion region. The corresponding repetition frequency difference of the dual wavelengths has excellent stability while the relative center wavelength can be adjusted in the range of 5 nm to 13 nm. There is no existence of significant sidebands in the optical spectrum during the whole tuning process. This dual-wavelength laser based on two spontaneous radiation peaks in the shorter wavelength direction has great application potential. Our work provides a new design solution for dual-comb sources (DCSs).

Acoustic Wave Coupling in Dual-Wavelength Orthogonal Polarized Brillouin Random Fiber Laser Using Polarization-Maintaining Fiber

Acoustic wave coupling in dual-wavelength orthogonal polarized Brillouin random fiber laser (BRFL) based on polarization-maintaining (PM) fiber is characterized experimentally for the first time. Dual-wavelength BRFL is generated when the pump light is injected to the Brillouin gain PM fiber at 45 degrees from the slow axis. The dynamics of intensity and frequency of dual-wavelength and single-wavelength BRFLs are investigated. The spectrum of Pearson’s correlation coefficient between different frequencies of the dual-wavelength BRFL shows several correlation peaks due to gain competition of two spatially overlapped coupled modes induced by acoustic wave coupling. The dual-wavelength BRFL presents a lower laser frequency drift with a standard deviation of 2.55 MHz and a larger relative intensity fluctuation with a standard deviation of 0.54 compared with that of single-wavelength BRFL (3.68 MHz and 0.32), which is attributed by increased photon-phonon coupling over the Brillouin gain fiber resulting from the coupling of acoustic waves in fast and slow axis due to 45 degrees pumping. In addition, replica symmetry breaking (RSB) is observed in dual-wavelength BRFL due to the increased gain competition of more random modes from acoustic wave coupling, which leads to correlated intensity fluctuations from trace to trace. The exploration of the internal spectral correlation, intensity fluctuation, RSB and frequency drift exposes the acoustic wave coupling in the dual-wavelength Brillouin random lasing process.

Dual-wavelength harmonic mode-locked dissipative soliton resonance of Yb fiber laser

Dissipative soliton resonance (DSR) mode-locked fiber lasers have stimulated great interest recent years due to their unique pulse-breaking-free advantage for scaling soliton pulse energy. However, the mechanism accounting for pulse breaking to generate multipulses in DSR fiber lasers has not reached a consensus. Here, we show that harmonic mode-locked DSR 1-μm Yb-doped fiber laser in the dual-wavelength regime can be realized with a semiconductor saturable absorber mirror (SESAM). In the fundamental frequency (3.5 MHz) mode-locked state, the pulse width continuously broadens from 2 to 8.9 ns as the output power increases from 1.26 to 5.1 mW (pulse energy being from 0.36 to 1.46 nJ), while the pulse peak power is clamped at 0.17 W, highlighting the typical characteristics of DSR mode-locking operation. Through simply adjusting the SESAM’s feedback conditions, the DSR fiber laser can transits from the fundamental-frequency mode locking to harmonic mode-locked states. Harmonic states from the 2nd to 9th order have been observed, with pulse repetition rate enhanced from 7 to 31.5 MHz. Under fixed pump power, increasing harmonic orders leads to reduction of the pulse width and pulse energy but does not change the unique quantization feature of the peak power. The status of the SESAM also guarantees the generation of dual wavelengths centered at 1072.5 and 1079.5 nm with spectral widths of 2.7 and 1.9 nm, respectively. This dual-wavelength harmonic mode-locked DSR Yb fiber laser can find applications in various areas.

Mechanisms of dual-wavelength dissipative soliton mode-locking in net-normal dispersion fiber lasers

Dual-wavelength mode-locked fiber lasers have attracted great attention due to their enormous potential in facilitating dual-comb spectroscopy. However, mechanism for dual-wavelength dissipative soliton mode-locking and the intracavity dynamics are still elusive. In this paper, we construct a simple and universal model to numerically investigate the intracavity buildup dynamics of dual-wavelength mode-locking in an all-normal dispersion fiber laser. By resolving the pulses evolution and their interactions, we find that the chromatic dispersion induced pulse collision plays an important role in dual-wavelength pulses formation and propagation. At the chaotic stage, the collision-induced energy upheaval results in drastic nonlinear coupling effects, which contribute to the dual-wavelength mode-locking and formation of dual-wavelength soliton molecules. While at the stable dual-wavelength mode-locking stage, the two asynchronous pulses periodically collide, accompanying extremely intense wave generation and spectral explosion. Moreover, cavity energy and gain competition are modeled and optimized to realize the self-started pulse-splitting-free dual-wavelength mode-locking.

Switchable and compact dual-wavelength random fiber laser based on random Bragg grating array

A switchable dual-wavelength random fiber laser (DW-RFL) with compact structure and a low-threshold is demonstrated. A Fabry-Perot interferometer which consists of a pair of fiber Bragg gratings is used in the DW-RFL as a filter to select two lasing wavelengths. The random Bragg grating array (RBGA), instead of long-distance single mode fiber, is used to introduce random distributed feedback. The threshold is reduced and the stability is improved due to the RBGA with high random feedback efficiency and a section of high gain of the erbium-doped fiber. Wavelength selecting and switching can be realized by tuning the pump power. The principle of RBGA and FBG-based F-P interferometer in the DW-RFL is analyzed and simulated. The experimental results show that the lasing threshold is about 18 mW and the optical signal noise ratio is about 40 dB. The stable dual-wavelength oscillation with uniform amplitude is realized. The wavelength spacing of the two lasing lines is within 0.095 nm and the maximum peak-power fluctuation is less than 1 dB. The proposed switchable and stable DW-RFL can be employed in microwave or terahertz generation systems, optical sensing, coherent communication and high resolution measurements.

Dual-wavelength mode-locked fiber laser based on graphene materials

Dual-wavelength mode-locked fiber laser based on graphene materials

Dual-wavelength mode-locked laser based on optimization of erbium-doped fiber length

The length of an erbium-doped fiber laser is optimized to develop a dual-wavelength nonlinear polarization rotation mode-locked erbium-doped fiber laser. The mode-locked laser can emit two stable wavelengths of 1530 nm and 1558 nm with a fiber length of 570 cm. With the absorbed pump power of 150 mW, the maximum average output power of 19.2 mW with the repetition frequency of 11.95 MHz and pulse width of 389 fs is obtained.

Tunable Spacing Dual-Wavelength Q-Switched Fiber Laser Based on Tunable FBG Device

A tunable spacing dual-wavelength Q-switched fiber laser is experimentally demonstrated based on a fiber Bragg grating tunable device incorporated in an erbium-doped fiber laser (EDFL). The system utilizes two identical fiber Bragg gratings (FBGs) at 1547.1 nm origin to enable two laser lines operation. The wavelength separations between two laser lines are controlled by fixing one of the FBGs while applying mechanical stretch and compression to the other one, using a fiber Bragg grating tunable device. The seven steps of wavelength spacing could be tuned from 0.3344 to 0.0469 nm spacing. Pulse characteristics for both close and wide spacing of dual-wavelength Q-switched fiber laser are successfully being recorded. The findings demonstrate the latest idea of dual-wavelength fiber laser based on FBG tunable device, which offers a wide range of future applications.

Harmonic dual-wavelength and multi-soliton pattern fiber laser based on GO-Sb2Se3 saturable absorbers

As new two-dimensional materials, antimony selenide (Sb2Se3) and graphene oxide (GO) are ideal photoelectric materials due to their appropriate band gap structure and strong light-matter interaction, which can be used in optical modulators, broadband ultrafast optical switches, and other photoelectric fields. The GO and Sb2Se3/GO measurements show excellent nonlinear characteristics with the modulation depth of 3.18% and 4.78%, respectively. This work proposes a harmonic dual-wavelength (HDW) fiber laser based on GO. This provides new possibilities for the research of ultrashort pulse sources with both high repetition frequency and multiple wavelengths. Furthermore, the conventional soliton mode-locking with 984 fs pulse width and soliton bundles mode-locking is obtained. The Sb2Se3/GO SA is coupled into the laser cavity for the first time to achieve higher performance mode-locked pulse. The results show that Sb2Se3/GO SA can shorten the pulse width and increase the output power more effectively than GO, such as the pulse width is shortened from 984 fs to 511 fs and the slope efficiency increased from 11.9% to 16.18%, which confirms its potential application in nonlinear optical material and ultrafast pulse generation. The results provide a new opportunity to apply traditional broadband nonlinear optical materials in ultrafast photonics and make a fundamental contribution to the development of advanced nanophotonic devices.

Simultaneous dual-wavelength Q-switched fiber laser utilizing tungsten sulfide as saturable absorber

Dual-wavelength Q-switched Erbium-doped fiber laser (EDFL) was shown by using tungsten disulfide (WS2), which was deposited onto a micro-sphere resonator (MSR) as a saturable absorber (SA). WS2 functions to modulate the cavity loss for Q-switching while the dual-wavelength operation was realized due to MSR, which allows only two wavelengths to oscillate in the resonator. MSR with the sphere diameter of 200 μm was fabricated at the tip of a standard single mode-fiber by employing a fiber fusion splicer machine. The SA was obtained by repeatedly dropping and drying of WS2 solution onto the MSR structure to form an active thin layer. The SA was incorporated into an EDFL cavity to realize a dual-wavelength Q-switched laser operating at 1554.0 nm and 1560.7 nm. The repetition rate of the pulse train is tunable from 72.4 kHz to 85.1 kHz as the pump power is increased from 104.6 mW to 145.8 mW. At 145.8 mW pump, the minimum pulse width and maximum pulse energy were obtained at 3.47 µs and 131.4 nJ, respectively. The dual-wavelength Q-switched laser was stable and thus it is suitable for use in airborne Lidar, environmental sensing, and terahertz applications.

Tunable Dual-Wavelength Bismuth Fiber Laser With 37.8-GHz Frequency Spacing

A tunable dual-wavelength Brillouin-bismuth fiber laser with a triple-Brillouin frequency spacing of ∼37.8 GHz was demonstrated by employing modular structures. The modular designs can be divided into two main cavities, whereby cavity 1 consisted of a 2-km single-mode fiber (SMF) and a loop mirror that was able to generate a single-spaced Brillouin shift, while cavity 2 comprised of 10-km dispersion compensating fiber (DCF) that was able to produce a double-spaced Brillouin shift. Based on this design, a stable dual-wavelength lasing was established with a low peak power fluctuation of 0.13 dB and 0.6 dB for the Brillouin pump (BP) and third Brillouin Stokes line (BS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ), respectively. By varying the center wavelength of the Brillouin pump, the dual-wavelength laser can be tuned across a 40 nm span, ranging from 1300 nm to 1340 nm. The frequency spacing of the Brillouin-bismuth fiber laser can also be easily switched between ∼12.6 GHz, ∼25.2 GHz, and ∼37.8 GHz by utilizing these modular structures. The proposed dual-wavelength laser has a promising potential for application as a low phase noise source for microwave generation.

Phase-noise suppression for the optical-heterodyne-generated microwave based on the amplitude-to-phase conversion

By reducing the noise component induced by the amplitude-to-phase conversion, a broadband phase-noise suppression of a 20.5 GHz photonic microwave, generated from an optical heterodyne of a dual-wavelength single-frequency fiber laser (DW-SFFL) is experimentally demonstrated. This is done by suppressing the intensity noise of the DW-SFFL through optoelectronic feedback, the microwave shows phase-noise suppression around the frequency range 100 Hz to 100 kHz. The phase-noise suppression of 6.1 dB at 1 kHz offset frequency and a linewidth of 2.15 kHz are obtained from this microwave system. The successful improvement indicates the feasibility of our strategy in obtaining a low phase-noise microwave.

Single- and dual-wavelength fiber laser with multi-transverse modes.

A single- and dual-wavelength fiber laser with multi-transverse modes is proposed. Mode interference is realized in the core of an optical fiber by writing a long period fiber grating on a few-mode fiber to obtain the LP01 mode and the LP11 mode simultaneously. A mode interferometer based on a few-mode long period fiber grating (FM-LPFG) is used as a comb filter in the ring-cavity fiber laser. Single- and dual-wavelength outputs can be achieved in the fiber laser by adjusting a polarization controller (PC). A mode-selective photonic lantern is used to realize mode conversion, and six LP modes, LP01, LP11a, LP11b, LP21a, LP21b, and LP02, can be generated. A single- and dual-wavelength fiber laser with multi-transverse modes can be achieved by combining a mode interferometer with a mode-selective photonic lantern. This work has potential applications in mode division multiplexing (MDM) systems to enlarge the capacity of optical communications.

Dual-wavelength mode-locked Er-doped fiber laser in a spectral filter free cavity

We present the experimental investigation of a dual-wavelength passively mode-locked Er-doped fiber laser with strict polarization control. The configuration includes a double-pass amplifier with a Faraday mirror and twisted fiber. We observe that including double-twist fiber cancels circular and linear birefringence and allows obtaining dual-wavelength emission varying the losses in the cavity. In contrast, results including single-twist fiber which only emits single-wavelength due to large circular birefringence.

Widely tunable single-/dual-wavelength fiber lasers with ultra-narrow linewidth and high OSNR using high quality passive subring cavity and novel tuning method: erratum.

We provide a corrected equation of our previous publication [Opt. Express24, 19760 (2016)10.1364/OE.24.019760].

Self-Started Dual-Wavelength Mode-Locking With Well-Controlled Repetition Rate Difference

Dual-wavelength mode-locked fiber lasers are considered as ideal solutions for fast, precise, and sensitive dual-comb spectroscopy. In this study, we present a self-started dual-wavelength fiber laser by combining a nonlinear amplifying loop mirror and a Lyot filter. Nonlinear phase accumulation, dual-wavelength competition, and crosstalk between the mode-locking mechanism and filtering effect are well addressed to realize the self-started dual-wavelength mode-locking. Furthermore, by temperature controlling the specific polarization-maintaining fiber, our dual-wavelength laser can be continuously tuned in a wavelength range of ~6 nm, corresponding to a well-controlled repetition rates change of 80 Hz and their difference change of 30 Hz. Mutual coherence of the dual-wavelength pulses is demonstrated by detecting the multi-heterodyne beat notes and measuring the fluctuation of the repetition rate difference. Within 10 hours of measurement, the dual-wavelength repetition rates difference remains stable at 1180 Hz with an Allan deviation of ~9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> Hz @ 1s. By virtue of the all polarization-maintaining structure, our dual-wavelength laser shows improved long-term stability and repeatability, which will facilitate the turn-key, robust, and reproducible dual-comb spectroscopy for high-power or field applications.

Tunable and dual-wavelength mode-locked Yb-doped fiber laser based on graded-index multimode fiber device

We have implemented wavelength-tunable and dual-wavelength in an ytterbium-doped passively mode-locked fiber laser using a single mode-graded index multimode-single mode fiber (SMF-GIMF-SMF) device as the saturable absorber (SA) without additional components. Such an all-fiber SA device exhibits fantastic properties with a large modulation depth of 22.9%, a small saturation fluence of 8.3 μJ/cm2, and the transmission curve with a capacity of gain-flattening, which are suitable for the tunable mode-locking generation. Benefiting from the intracavity birefringence-induced filtering effect of the laser cavity, tuning and dual-wavelength operations are obtained. For the tuning operation, the central wavelength of the dissipative solitons (DSs) can be tuned from 1028.5 to 1074.4 nm, with the pulse duration of tens of picoseconds. For the dual-wavelength mode-locking operation, the central wavelengths of dual-wavelength can be switched from 1032.3/1054.1 nm to 1049.3/1072.6 nm. Our results indicate that the SMF-GIMF-SMF device provides a novel platform for wavelength-tunable and dual-wavelength mode-locking in Yb-doped fiber lasers.

Simulation of dual-wavelength self-similar pulse based on two dimensional material fiber laser

Multi-wavelength self-similar fiber laser has many advantages that other lasers do not have. It has many applications in industry, sensing, medical, military, communication and other fields. Two dimensional material devices can be used as saturable absorbers to construct dual-wavelength self-similar pulse mode-locked fiber lasers. In this paper, the evolution characteristics of dual-wavelength self-similar pulse based on two dimensional material mode-locked fiber lasers are analysed.

Dual-comb Spectroscopy for Laminar Premixed Flames with a Free-running Fiber Laser

ABSTRACT Dual-comb spectroscopy (DCS) has emerged as an important new technique for high-resolution molecular spectroscopy. However, this powerful tool has not been widely utilized in combustion diagnostics due to the difficulty of maintaining the mutual coherence between the two comb sources. In this work, we demonstrated a free-running fiber-laser-based DCS for in situ and non-intrusive H2O and C2H2 measurements in laminar premixed flames. This picometer-resolution dual-comb spectroscopic system was developed by using a single erbium-doped fiber laser at 1.5 μm along with a multipass optical configuration for the enhanced absorption measurement. Because of the mutual coherence of the two comb pulse trains emitted from the same laser cavity, DCS could be performed without using any phase-locking systems. Absorption spectra of CH4/O2/air flames over the spectral range 6503 cm−1 – 6535 cm−1 were measured at different reactant flow rates and heights above the burner, showing a good agreement with the spectral simulation of high-temperature H2O using the HITEMP database. A noise equivalent (1σ) absorption coefficient of 9.5 × 10−5 cm−1 was achieved using the current DCS system. Besides, the dual-comb measurement of a C2H4/air sooting flame was also performed at the equivalence ratio Ф = 2.94 and compared with the spectral simulation of high-temperature H2O and C2H2. All the spectral data were retrieved by 1500 averages of interferograms to increase the spectral signal-to-noise ratio (SNR), but a single interferogram could be acquired at 0.83 ms using the current free-running dual-wavelength fiber laser.

Switchable single- and dual-wavelength femtosecond mode-locked Er-doped fiber laser based on carboxyl-functionalized graphene oxide saturable absorber

In this Letter, we demonstrated the switchable single- and dual-wavelength femtosecond soliton generation in single-mode Er-doped fiber lasers with the usage of carboxyl-functionalized graphene oxide (GO-COOH) saturable absorbers (SAs) for the first time, to the best of our knowledge. The fiber laser generated a stable single-wavelength conventional soliton at 1560.1 nm with a pulse duration of 548.1 fs. The dual-wavelength solitons centered at 1531.9 nm and 1555.2 nm with a spacing of approximately 23 nm can be obtained by adjusting the pump power of the cavity. Our experimental results indicated the GO-COOH has great potential to be used in ultrafast fiber lasers as broadband SAs.