Dual-wavelength Mode-locked Laser Research Articles

Internal motion within ultrafast asynchronous dual wavelength mode-locked lasers.

Realtime spectroscopy access to ultrafast fiber lasers provides new opportunities for exploring complex soliton interaction dynamics. In this study, we employ a time-stretch technique that enables real-time access to both spectral and temporal dynamics, revealing rich nonlinear processes in asynchronous dual wavelength mode-locked pulses in an ultrafast fiber laser. Due to the different group velocities of the two wavelengths, the mode-locked solitons centered at different wavelengths periodically collide with each other. We recorded the entire process of soliton establishment, stabilization, and disappearance, shedding light on the mystery of stable transmission of dual-wavelength mode-locked pulses. These processes were observed for the first time in an ultrafast fiber laser, and the experimental evidence provides important insights into the understanding of nonlinear dynamics in fiber lasers, as well as the potential for improving laser performance for application in dual-comb spectroscopy.

Dual-wavelength dispersion-managed soliton all-fiber mode-locked laser based on birefringence-filtered nonlinear polarization evolution

Single-cavity dual-comb mode-locked lasers, an emerging dual-comb technology, can generate two sets of pulse sequences with excellent mutual coherence, thus eliminating the need for complex active noise reduction systems. We report the generation of dual-wavelength dispersion-managed solitons in a near-zero anomalous-dispersion Er-doped mode-locked fiber laser. Transmissive dual channels are provided by birefringence filtering effect. The dual-wavelength mode-locking centers at 1539.1 and 1578.8 nm with the repetition-rate difference of 420 Hz. Furthermore, 2-hour spectral stability is measured in an open environment, and we analyze the intra-cavity dynamics that influences the long-term stability of the dual-wavelength mode-locked laser operating in the free-running state.

Dual-wavelength self-mode-locked semiconductor disk laser

Dual-wavelength mode-locked lasers can be widely used in optical communication, pump-probe experiment, nonlinear frequency conversion, etc. In this paper, a dual-wavelength self-mode-locked semiconductor disk laser is reported for the first time, to the best of our knowledge. A simple linear resonator is formed by using a high reflectivity distributed Bragg reflector at the bottom of the gain chip, and an external output mirror; the cavity length is about 135 mm, with no need of additional inserted elements. Based on the Kerr effect of the gain medium and the soft aperture formed by the pump spot on the gain chip, along with the fine adjustment of cavity length and pump intensity, the mode-locking process can be started from the free running and the stable self-mode-locking can be realized. The mode-locked pulse width is 4.3 ps, the repetition rate is 1.1 GHz, and the maximum output power is 323.9 mW, which corresponds to a peak power of 68 W. After the laser is mode locked, a readily available blade, which can introduce a wavelength-dependent loss for different laser modes, resulting in a lager cavity loss for a longer-wavelength mode and a smaller cavity loss for a shorter-wavelength mode, is used as a wavelength tuning element, and is inserted into the cavity in the direction perpendicular to the optical axis of the resonator. By changing the depth of the blade inserted into the cavity, the laser wavelength can be continuously tuned from the initial oscillating wavelength (longer-wavelength) to a shorter wavelength, a stable dual-wavelength output with equal intensity can be obtained at a specific position, and the stable continuous-wave mode-locking can be maintained simultaneously. The steady dual-wavelengths in the experiment are 951 and 961 nm, and the corresponding output power is 32 mW. The above dual-wavelength outputs have good coherence since they are stimulated radiations from the same gain chip. Meanwhile, they have relatively high peak power and strictly meet the coaxial conditions, and these are all advantages for the difference frequency generation (DFG). The frequency of the DFG in the experiment is approximately 3.3 THz, which can be widely used in laser radar, remote sensing, homeland security, counter-terrorism, atmospheric and environmental monitoring and otherareas.

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.

Switchable dual-wavelength mode-locked fiber laser using Saganc loop mirror

We report an all-fiber switchable dual-wavelength mode-locked laser using a Sagnac loop mirror. In this laser, the Sagnac loop mirror acts as a tunable periodic filter, in which the wavelength spacing is determined by the length of the polarization maintaining fiber. With appropriate pump power, the mode-locked fiber laser can operate in both the tunable single-wavelength mode locking regime and the dual-wavelength mode locking regime by properly setting the states of the polarization controllers. In the single-wavelength mode locking regime, the laser achieves continuously tunable wavelength range from ∼1551 nm to ∼1562 nm. In the dual-wavelength mode locking regime, the laser can emit two stable asynchronous pulse trains with the central wavelengths of 1561.4 nm and 1551.1 nm, respectively. Due to the net negative dispersion of the laser cavity, the mode-locked pulse trains with different central wavelengths have different group velocities leading to a repetition rate difference of ∼530 Hz.

Dual-wavelength self-starting mode-locking Er-doped fiber laser with MnPS<sub>3</sub> saturable absorber

As a member of the metal phosphorus trichalcogenide family, MPS<sub>3</sub> is widely used in nonlinear optics and devices, which can be regarded as a significant benefit for the excellent photonic and optoelectronic properties. In this work, the MnPS<sub>3</sub> nanosheet is prepared by the chemical vapor transport method and the MnPS<sub>3</sub> saturable absorber is demonstrated by modifying mechanical exfoliation. To the best of our knowledge, the dual-wavelength self-starting mode-locking erbium-doped fiber laser with MnPS<sub>3</sub> saturable absorber is demonstrated for the first time. The dual wavelength mode-locked laser with a pulse repetition rate of 5.102 MHz at 1565.19 nm and 1565.63 nm is proposed. Its maximum output power at the dual-wavelength is 27.2 MW. The mode-locked laser can self-start and stably run for more than 280 h.

All-Fiber Dual-Wavelength Mode-Locked Laser Using a Bend-Induced-Birefringence Lyot-Filter as Gain-Tilt Equalizer

Multi-wavelength fiber lasers have emerged as a promising light source for the application in wavelength division multiplexing communication, terahertz wave generation and optical sensing due to high efficiency and robustness. Lyot-filter emerges as a potential device for multi-wavelength generation application. However, because of the high birefringence of polarization maintaining fiber in Lyot-filter, it is difficult to generate broadband dual-wavelength or multi-wavelength mode-locked fiber laser by using common Lyot-filter. In this paper, for the first time, we propose an idea of using the low birefringence induced by bending the single-mode fiber to form a Lyot-filter for dual-wavelength mode-locked fiber laser generation. The dual-wavelength output centers at 1532 and 1556 nm and it may simplify the set-up for dual-wavelength mode-locked laser.

L-Band Tunable and Dual-Wavelength Mode-Locked Fiber Laser With NCF-GIMF-Based SA

A hybrid structure of no-core fiber and graded-index multimode fiber (NCF-GIMF) is demonstrated, which can be used as both the saturable absorber (SA) and the wavelength selective element. By employing such a device, an L-band wavelength tunable Er-doped mode-locked laser is realized and stable single solitons of ~1.7 ps, with continuously tunable wavelengths from 1574 to 1601.1 nm, are generated. Moreover, dual-wavelength mode-locked laser operation at 1575.4 and 1603 nm is achieved, with a pulse duration of 1.2 and 1.7 ps, respectively. The proposed device is simple and compact and represents an effective approach for tunable and dual-wavelength mode-locked fiber laser operation.

基于钕钆双掺氟化钙晶体的调谐和双波长锁模激光器

基于钕钆双掺氟化钙晶体的调谐和双波长锁模激光器

Ultrafast mode-locked dual-wavelength thulium-doped fiber laser using a Mach-Zehnder interferometric filter

A simple and robust method to generate a dual-wavelength mode-locked laser using a tunable Mach-Zehnder filter (TMZF) and a single-wall carbon nanotube (SWCNT) based saturable absorber (SA) is proposed and demonstrated. The proposed laser uses a thulium-doped fiber for lasing in the two-micron region and exploits the interferometric spectrum of the TMZF to produce dual peaks with nearly equal magnitude. SWCNT based SA enables mode-locking at a threshold value of 150.4 mW with distinct dual-wavelength peaks at 1919.2 nm and 1963.7 nm. The peaks have a calculated pulse width of 1.8 ps and 1.6 ps, respectively with a repetition rate of 9.1 MHz with a relatively high optical-signal-to-noise ratio value of 59.1 dB. The output is also observed to remain unchanged over time, indicating high stability. The proposed laser has a promising application, particularly in ultrafast gas molecular spectroscopy and sensing.

Dual-wavelength mode-locked fiber laser based on tungsten disulfide saturable absorber

We report on the generation of dual-wavelength mode-locked laser pulse in an Er-doped ring-shaped fiber cavity with WS2 nanosheets based saturable absorber (SA), emitting at wavelength of 1531.8 nm and 1556.7 nm. The WS2 nanosheets were precipitated on the head face of fiber patch cord via light precipitation method. By adjusting the polarization of lasing mode, the gain of the Er-doped fiber laser was effectively controlled and the stable dual-wavelength mode-locking operation was achieved. Our investigation revealed WS2’s extraordinary nonlinear properties, which make it an excellent material for saturable absorber for passively mode-locked fiber lasers.

Widely tunable 2 μm continuous-wave and mode-locked fiber laser.

We propose and experimentally demonstrate a widely tunable mode-locked thulium-doped fiber laser. The laser can operate at both continuous-wave and mode-locked states at different pump power levels. A classic nonlinear polarization rotation structure is employed to obtain the passive mode-locked laser. A birefringence Lyot filter as a fiber comb filter is used to expand the tuning range. Thanks to the filtering component, the tuning range of the continuous-wave laser can reach 127nm (1823-1950nm). The tuning ranges of the single-wavelength and dual-wavelength mode-locked lasers are 94nm (1835-1929nm) and 87nm (1831-1918nm), respectively, with a 3.085MHz repetition rate and 75ps pulse width.

Effect of spatial hole burning on a dual-wavelength mode-locked laser based on compactly combined dual gain media

The effect of spatial hole burning (SHB) on dual-wavelength self-mode-locked lasers based on physically combined Nd:YVO4/Nd:LuVO4 and Nd:YVO4/Nd:KGW composite active medium is comparatively investigated. The length of the first Nd:YVO4 crystal is optimized to realize a highly compact and efficient TEM00-mode picosecond laser at 1.06 μm with optical conversion efficiency greater than 20%. When the SHB effect is enhanced by decreasing the separation between the input end mirror and the composite gain medium, it is experimentally found that not only the pulse duration monotonically decreases, but also the temporal behavior gradually displays a narrow-peak-on-a-pedestal shape for the Nd:YVO4/Nd:LuVO4 scheme, while the multipulse operation can be obtained for the Nd:YVO4/Nd:KGW configuration. These phenomena are further explored by numerically simulating mode-locked pulses from the experimentally measured optical spectra.

Dual-wavelength passively mode-locked Nd:LuYSiO_5 laser with SESAM

A diode-end-pumped dual-wavelength mode-locked laser based on Nd:LuYSiO5 crystal is demonstrated. With a SESAM, simultaneous mode locking at the 1075.8 nm and 1078.1 nm is achieved and the dual-wavelength mode locked pulses have a pulse width of 8.9 ps. Due to frequency beating, ultrahigh repetition rate ultrafast pulses with 997 fs pulse width and 0.59 THz repetition rate are further formed. Under 12.7 W absorbed pump power 1.7 W mode-locked output power was obtained, the slope efficiency of the mode locked laser was 24.3%.

A novel tunable dual-wavelength external-cavity laser diode array and its applications

We review the principles and characteristics of a novel tunable external-cavity laser diode source. It can operate as either a continuous wave (CW) single-wavelength, a CW dual-wavelength, a single-wavelength mode-locked, or a tunable dual-wavelength mode-locked laser. The gain medium is a commercial laser diode array. The telescopic external cavity consists of a grazing-incidence grating, a lens and a stripe-mirror. The external cavity provides functions of wavelength selection, dispersion compensation and spatial mode control. The characteristics of the laser under CW or mode-locked operation are described. The dual-wavelength laser output exhibits beat note beyond 7 THz. The tunable multi-terahertz beat frequency is characterized by a non-collinear intensity autocorrelation technique. A dual-wavelength interferometer that uses a tunable dual-wavelength laser as the light source is demonstrated. Finally, theoretical analysis is presented, which demonstrates that the dual-wavelength output of the laser is stable if the modes at the two wavelengths correspond to different array lateral modes.