Single-mode SOA-based 1kHz-linewidth dual-wavelength random fiber laser

Random laser emission at 1064 and 1550 nm in a Er/Yb co-doped fiber-based dual-wavelength random fiber laser

Dual-wavelength fiber lasers operating with a wide spectral separation are of considerable importance for many applications. In this study, we propose and experimentally explore an all-fiberized dual-wavelength random fiber laser with bi-directional laser output operating at 1064 and 1550 nm, respectively. A specially designed Er/Yb co-doped fiber, by optimizing the concentrations of the co-doped Er, Yb, Al and P, was developed for simultaneously providing Er ions gain and Yb ions gain for RFL. Two spans of single mode passive fibers are employed to providing random feedback for 1064 and 1550 nm random lasing, respectively. The RFL generates 5.35 W at 1064 nm and 6.61 W at 1550 nm random lasers. Two power amplifiers (PA) enhance the seed laser to 50 W at 1064 nm with a 3 dB bandwidth of 0.31 nm and 20 W at 1550 nm with a 3 dB bandwidth of 1.18 nm. Both the short- and long-term time domain stabilities are crucial for practical applications. The output lasers of 1064 and 1550 nm PAs are in the single transverse mode operating with a nearly Gaussian profile. To the best of our knowledge, this is the first demonstration of a dual-wavelength RFL, with a spectral separation as far as about 500 nm in an all-fiber configuration.

Mode-modulation-induced high power dual-wavelength generation in a random distributed feedback Raman fiber laser

An all-fiberized random distributed feedback Raman fiber laser (RRFL) with mode-modulation-induced wavelength manipulation and dual-wavelength generation has been demonstrated, where an electrically controlled intra-cavity acoustically-induced fiber grating (AIFG) is employed to adjust the input modal content at the signal wavelength. The wavelength agility of both the Raman effect and the Rayleigh backscattering in RRFL benefits on broadband laser output in case of broadband pumping. The feedback modal content at different wavelengths can be adjusted by AIFG, and then the output spectral manipulation can be ultimately manifested through the mode competition in RRFL. Under the efficient mode modulation, the output spectrum can be continuously tuned from 1124.3 nm to 1133.8 nm with single wavelength, while ulteriorly the dual-wavelength spectrum can be formed at 1124.1 nm and 1134.7 nm with a signal-noise-ratio of 45 dB. Throughout, the power is beyond 47 W with good stability and repeatability. To the best of our knowledge, this is the first dual-wavelength fiber laser based on mode modulation and the highest output power ever reported for an all-fiberized continuous wave dual-wavelength fiber laser.

Multi-wavelength random fiber laser based on a tilted parallel inscribed apodized fiber Bragg grating array

We propose and demonstrate a multi-wavelength random fiber laser (RFL) based on a novel, to the best of our knowledge, compact apodized fiber Bragg grating array (AFBGA). The AFBGA is fabricated by a femtosecond laser with the point-by-point tilted parallel inscription method. The characteristics of the AFBGA can be flexibly controlled in the inscription process. Hybrid erbium-Raman gain is used in the RFL and reduces the lasing threshold to sub-watt level. Stable emissions at two to six wavelengths are achieved with the corresponding AFBGAs, and more wavelengths are expected with higher pump power and AFBGAs containing more channels. A thermo-electric cooler is employed to improve the stability of the RFL, and the maximum wavelength and power fluctuations of a three-wavelength RFL are 64 pm and 0.35 dB, respectively. With flexible AFBGA fabrication and simple structure, the proposed RFL enriches the choice of multi-wavelength devices and has significant potential in practical applications.

Tunable and switchable multi-wavelength random distributed feedback fiber laser based on SMF and a cascaded Sagnac ring filter

A tunable and switchable multi-wavelength random distributed feedback fiber laser based on cascaded Sagnac loops is proposed and experimentally demonstrated. The random distribution feedback of the laser is provided by the Rayleigh scattering generated by the single-mode fiber (SMF). The cascaded Sagnac loops act as a filter and a reflector in the half-open cavity laser. The single-, dual-, three-, and four-wavelength channels can be realized by adjusting the angle of the polarization controller at the pump power of 300 mW. In the single-, dual-, and three-wavelength channels, the wavelength spacing can be maintained, and the laser wavelength position can be changed at the same time. The maximum wavelength tuning ranges of single-, dual-, and three-wavelength outputs are about 4.5 nm, 2.6 nm, and 1 nm, respectively. The proposed multi-wavelength random fiber laser has the advantages of simple structure and low threshold, and it has good application prospects in remote sensing and imaging systems.

Evaluation of Pearson correlation coefficient and Parisi parameter of replica symmetry breaking in a hybrid electronically addressable random fiber laser

The hybrid electronically addressable random (HEAR) laser is a novel type of random fiber laser that presents the remarkable property of selection of the fiber section with lasing emission. Here we present a joint analysis of the correlations between intensity fluctuations at distinct wavelengths and replica symmetry breaking (RSB) behavior of the HEAR laser. We introduce a modified Pearson coefficient that simultaneously comprises both the Parisi overlap parameter and standard Pearson correlation coefficient. Our results highlight the contrast between the correlations and presence or not of RSB phenomenon in the spontaneous emission behavior well below threshold, replica-symmetric ASE regime slightly below threshold, and RSB phase with random lasing emission above threshold. In particular, in the latter we find that the onset of RSB behavior is accompanied by a stochastic dynamics of the lasing modes, leading to competition for gain intertwined with correlation and anti-correlation between modes in this complex photonic phase.

Advances in Random Fiber Lasers and Their Sensing Application

Compared with conventional laser, random laser (RL) has no resonant cavity, reducing the requirement of cavity design. In recent years, the random fiber laser (RFL), a novel kind of RL, has made great progress in theories and experiments. The RFL has a simpler structure, a more flexible design, and higher reliability. It has valuable applications for earth sciences, biological life sciences, and national defense security, due to these unique properties. This paper reviews the development of RFLs in the last decade, including their configurations based on various optical fibers and their output properties, especially the method of control. Moreover, we also introduce their applications in the optical fiber sensing system, which is a very important and practical orientation to study. Finally, this paper presents the prospects of RFLs.

Hybrid electronically addressable random fiber laser

We report here a novel architecture for a random fiber laser exploiting the combination of a semiconductor optical amplifier (SOA) and an erbium doped fiber (EDF). The EDF was optically biased by a continuous wave pump laser, whereas the SOA was arranged in a fiber loop-mirror and driven by nanosecond duration current pulses. Laser pulses were obtained by synchronizing the SOA driver to the returning amplified Rayleigh back-scattered light from a selected short section of the EDF. By tuning the SOA pulse rate, random lasing was achieved by addressing selected meter-long sections of the 81-m long EDF, which was open-ended. Laser oscillation can be potentially obtained with SOA modulation frequencies from several kHz to the MHz regime. We discuss the mechanism leading to the hybrid random laser emission, connecting with phase sensitive optical time domain reflectometry and envision potential applications of this electronically addressable random laser.

Dual-wavelength random distributed feedback fiber laser with wavelength, linewidth, and power ratio tunability

Owing to the special power distribution property, a random distributed feedback Raman fiber laser can achieve a high power spectrally flexible output with a low power spectrally tuning device. Here, an all-fiberized linearly polarized dual-wavelength random distributed feedback Raman laser with wavelength, linewidth, and power ratio tunability is demonstrated. By adopting two watt-level bandwidth adjustable optical filters, a spectrum-manipulable dual-wavelength output with nearly a 10 W output power is achieved. The wavelength separation can be tuned from 2.5 to 13 nm, and the 3 dB linewidth of the output can be doubled by increasing the bandwidth of the optical filter. The power ratio of each laser line can be tuned from 0 to nearly 100% with the help of two variable optical attenuators. A maximum output power of 9.46 W is realized, with a polarization extinction ratio up to 20.5 dB. The proposed dual-wavelength fiber laser can be employed as a pump source in frequency tunable, bandwidth adjustable terahertz microwave generation, and mid-infrared optical parametric oscillators.

Longitudinal mode dynamics in SOA-based random feedback fiber lasers

We experimentally demonstrate that single-mode operation of an SOA-based random fiber laser is only possible in pulsed regime at driving currents close to the threshold, whereas multimode regime dominates under higher SOA currents. Theoretical simulations support random frequency spacing of the laser modes to be due to residual stress on the optical fiber. Pulsed regime is shown to be due to randomly driven Q-switching induced by a scintillation effect in the Rayleigh backscattered light, which effectively translates as a time-varying cavity loss. Mode lifetimes of ∼1 ms and narrow linewidths ranging from 4 to 7 kHz were experimentally observed.

Pump distribution effect in dual-wavelength Raman-erbium random distributed feedback fiber laser

This work demonstrates a simple dual-wavelength random distributed feedback fiber laser via excitation of the Raman-erbium hybrid gain by a single pump source. Lasing wavelengths at 1568 nm and 1595 nm with 48.48 dBm maximum OSNR were generated without the need for physical reflectors. Enhancements were performed using pump power distribution and a seeded feedback to reduce the peak disparity to only 0.16 dB. The long cavity hybrid random laser with its balanced and broadly spaced dual-wavelength output offers immense potential for long distance dual laser applications.