Doped Fiber Laser Research Articles

Combination dual-tapered fiber with band-pass filter in generating multi-wavelength Er3+-doped fiber laser

Combination dual-tapered fiber with band-pass filter in generating multi-wavelength Er3+-doped fiber laser

1010 nm Directly LD-Pumped 6kW Monolithic Fiber Laser Employing Long-Tapered Yb3+-Doped Fiber

Utilizing long-wavelength laser diodes (LDs) for pumping to achieve high-power fiber laser output is an effective method for attaining high quantum efficiency and excellent thermal management. In this work, we report on a Master Oscillator Power Amplifier (MOPA)-structured long-tapered Yb3+-doped fiber laser directly pumped by long-wavelength laser diodes. By shifting the center wavelength of the pump source to 1010 nm, the heat generation within the fiber laser is effectively controlled, thereby increasing the transverse mode instability (TMI) threshold. Additionally, the use of a long-tapered fiber enlarges the mode area and suppresses stimulated Raman scattering (SRS) effects that typically arise from increased fiber length. As a result, an output of 6030 W is achieved with an optical-to-optical (O–O) efficiency of 83.7%, a SRS suppression ratio exceeding 50 dB, and no occurrence of dynamic TMI. This approach provides a valuable reference for optimizing long-wavelength pumping to suppress nonlinear effects and also holds potential for wide-temperature operational applications.

All-fiber supercontinuum absorption spectroscopy for mid-infrared gas sensing

The development of compact fiber-based light sources emitting over a wide wavelength range in the mid-infrared and their application to the detection of greenhouse gases and volatile organic compounds still remain of critical interest. In the present work, we make use of several dedicated infrared fibers for implementing a mid-infrared optical device pumped by a thulium doped-fiber laser around 1.965 μm that simultaneously enables a first nonlinear stage of frequency conversion and supercontinuum generation and a second linear stage of gas absorption spectroscopy. As a proof-of-principle, we carry out mid-infrared supercontinuum absorption spectroscopy of methane around 7.7 μm by means of a hollow-core fiber-based gas cell combined to a commercial Fourier-transform infrared spectrometer. Our all-fiber configuration operating in the femtosecond regime at megahertz repetition rate allows the detection of methane concentrations as low as 20 ppm.

Green pulse regenerative amplification using a Pr3+:LiYF4 crystal pumped by GaN blue laser diodes.

Direct regenerative amplifications of green pulses (522 nm) were investigated using a Pr3+-doped LiYF4 crystal pumped by GaN blue laser diodes. Green pulses with two different temporal duration regimes, i.e. sub-picosecond (sub-ps) and sub-nanosecond (sub-ns), were prepared from the second harmonic generation of the mode-locked Yb3+-doped fiber laser at the repetition rate of 100.86 kHz and used as a seed for the comparison of the amplification processes. For the sub-ps (0.63 ps) and sub-ns (0.3-0.4 ns) seeds, the amplifications resulted in 1.25 µJ and 1.53 µJ in the pulse energies, 0.60 nm and 0.27 nm bandwidths, and the beam qualities of (M2x = 2.26, M2y = 1.25) and (M2x = 1.47, M2y = 1.23), respectively. A comparison of the B integrals confirmed that the wider bandwidth and the lower beam quality of the sub-ps seed amplification versus the sub-ns seed amplification were caused by the nonlinear effects in the sub-ps amplification.

Modeling of rare-earth-doped double-clad fiber laser based on rate equations with spatially averaged parameters

A mathematical model of a rare-earth doped double-clad fiber laser based on rate equations with spatially averaged parameters laser has been developed. Analytical expressions for the threshold absorbed pump power, slope efficiency and laser output power have been obtained for the CW regime. It has been shown that the results of output power calculations using the analytical model for CW double-clad ytterbium and neodymium doped lasers are in a good agreement with the results obtained using numerical models described in literature. A quantitative criterion for the applicability of the presented analytical model for calculating the parameters of double-clad fiber lasers has been proposed. The applicability of the proposed model to describe the transient stage of the operation of a fiber laser under continuous pumping has been demonstrated.

Kilowatt-Level High-Efficiency Narrow-Linewidth All-Fiber Tm3+-Doped Laser

In this study, a kilowatt-level high-efficiency narrow-linewidth all-fiber Tm3+-doped continuous-wave laser operating at 1.95 μm is demonstrated. Benefitting from an advanced boost design of a two-stage main amplifier, it not only effectively manages heat dissipation resulting from the high pump-induced quantum defect but also realizes the controlled extraction of optical gain and improves the optical conversion efficiency. Finally, this laser system has realized an output power of 1018 W, a linewidth of 3.8 GHz, and a slope efficiency of 60.0% simultaneously. Moreover, a high optical signal-to-noise ratio of over 45 dB and excellent beam quality of M2 factors 1.19 are obtained. To the best of our knowledge, this represents the narrowest linewidth and highest slope efficiency achieved in a kilowatt-level Tm³⁺-doped fiber laser. Such a high-performance laser is ideally suited for mid-infrared generation and remote sensing applications.

High-energy nanosecond pulse extraction from a Tm3+-doped photonic crystal fiber laser emitting at 2050 nm with narrow linewidth.

A nanosecond-pulsed diode-pumped Tm3+-doped fiber laser (TDFL) operating at 2050 nm is reported based on a flexible photonic crystal fiber (PCF) with a core diameter of 50 µm. Analytical evaluation of reabsorption effects and optimization of the fiber length allow enhanced pulse energy extraction at long wavelengths. This enables the generation of Gaussian-shaped pulses with pulse energies of 1.9 mJ, pulse widths of 116 ns, and peak powers of 15.4 kW from the TDFL. The measured output spectrum shows a single peak at 2050 nm with a 3-dB-linewidth of 130 pm and a 10-dB-linewidth of 370 pm. With a slope efficiency of 44 %, the average output power of the pulsed TDFL is scaled up to 114 W. To the best of our knowledge, this represents the first demonstration of a Tm3+-doped PCF at a long emission wavelength of 2050 nm and the highest pulse energies from a TDFL based on a flexible fiber.

Nanosecond-pulse fiber laser mode-locked with iron phthalocyanine

Abstract In this paper, we demonstrated a passively mode-locked erbium doped fiber laser (EDFL) using iron phthalocyanine (FePc) material as a saturable absorber (SA). The FePc-SA was prepared via a casting method, integrating FePc powder with polyvinyl alcohol to form FePc-PVA film. When implemented into the mode-locked EDFL cavity, the laser generated 356 ns pulses at a repetition rate of 969 kHz. Operating at a wavelength of 1559 nm, the laser achieved pulse energy of 6.04 nJ, output power of 5.85 mW, and peak power of 0.014 W under a maximum pump power of 128.92 mW. The laser exhibited remarkable stability, evidenced by a signal-to-noise ratio of 71.7 dB at the fundamental frequency. These results demonstrate that FePc material effectively serves as a mode-locker for generating nanosecond pulses.

Spacing mode multi-wavelength erbium doped fiber laser based on a symmetrical long-period fiber grating

We present a multiwavelength erbium-doped fiber laser based on a symmetrical long-period fiber grating (LPFG) with tunable spacing mode between single lasing mode and multiwavelength spectra. The LPFG was manufactured using a thermal expansion technique using an LZM-100 glass processing system equipped with a CO2 laser, and it was used as a wavelength-selective filter (WSF) in the laser ring cavity. The laser can emit single, double, triple, quadruple, quintuple, or sextuple lines in the range from 1546 to 1563 nm, which can be tunable by controlling the radius of curvature of the LPFG in the range 0–0.2662 m −1. A minimal spacing mode of 1.92 nm was observed in the multiwavelength region; meanwhile, the fiber laser offers an average spacing mode of 6.945 nm between the multiwavelength region and the single emission. This laser has a 3 dB linewidth of 0.11 nm and a side mode suppression ratio (SMSR) of 55.56 dB. Finally, according to experimental results, the laser has high wavelength stability at room temperature for 88 min.

Generation of h-shaped pulse rains in Er3+-doped fiber lasers utilizing TaTe2 as saturable absorber

This paper presents a study on generating h-shaped pulse rains phenomena in Er3+-doped fiber laser employing TaTe2 as saturable absorber. The spectrum of the h-shaped pulse rains has a central wavelength of 1561.63 nm and a repetition frequency of 3.353 MHz. The h-shaped pulse rains comprise a leading peak, a flat-top, and drifting pulses. The leading peak is attributed to incomplete saturation caused by significant gain losses and the incomplete effect of peak power clamping. The flattop is produced by the effect of peak power clamping, while the mechanism underlying the drifting pulses necessitates further exploration. During the investigation of the h-shaped pulse rains, it was discovered that adjusting the pump power allows control over the number of drifting pulses and the length of the flat-top. A distinctive drifting pulse is observed at pump power of 210 mW. Our experimental results show that TaTe2 saturable absorber have great potential for application in ultrafast photonics.

Kilohertz-linewidth and low-threshold single-frequency all-fiber laser utilizing self-developed Nd3+-doped fluoro-sulfo-phosphate fiber.

Compared to Nd: YAG lasers, Nd3+-doped fiber lasers offer superior beam quality, compactness, and heat dissipation, especially in generating single-frequency lasers, which holds great promise for applications in optical atomic clocks, quantum computing, and high-precision bio-photonic imaging. In this study, theoretical simulations of the local environment and experimental analyses on the luminescent characteristics of what we believe to be a novel Nd3+-doped fluoro-sulfo-phosphate (FSP) laser glass were performed to mitigate the concentration and hydroxyl quenching effects. Based on that, a highly Nd3+-doped (4 mol%) FSP fiber with a large emission cross-section (3.24 × 10-20 cm2), wide bandwidth (33.7 nm), long lifetime (354 µs), and high gain coefficient (4.24 dB/cm) was designed. Utilizing this fiber, a 1065 nm SFFL with a low pump threshold of 18 mW, a narrow linewidth of 6.5 kHz, and a 0.9 µm compact all-fiber laser were demonstrated, highlighting the potential of Nd3+-doped FSP fiber in high-performance fiber lasers.

Polarization Influence on Er3+-Doped Multi-Wavelength Brillouin Fiber Laser Based on Fiber Loop Mirror

Polarization influences on the performance of multi-wavelength Brillouin Er3+-doped fiber laser are investigated by adjusting the polarization controller (PC) in the fiber loop mirror (FLM), where the linear laser cavity is composed of a fiber-tailed mirror and an FLM, and the stimulated Brillouin scattering (SBS) and the Er3+-doped fiber amplification (EDFA) simultaneously serve as the cavity gain. We realized 1–7 Brillouin laser lines by increasing the 980 nm pump power. For the first-order Brillouin laser, the signal–noise ratio (SNR) and optical intensity present a sinusoidal envelope; the conversion efficiency changes significantly from 0.56465 dBm/mw to 0.44975 dBm/mw by adjusting the ring’s angle in the PC; the first-order SBS thresholds are 20.4 mw, 36.1 mw and 28.5 mw at different angles θ2 = 36°, 276° and 300°, respectively; flatness between the two Brillouin lasers change obviously from 2.863 dB to 41.801 dB with different ring angles; the second-order Brillouin laser is suppressed and disappears finally at Δθ2 = −64° to −84° and 106°~136° angle variation. For the fifth-order Brillouin laser, the highest-order Brillouin laser line is seriously suppressed until it disappears at some angle variations similarly. The powers and wavelength stabilities for one-, three- and seven-wavelength Brillouin fiber lasers were measured in 1 h, and the obtained Er3+-doped multi-wavelength Brillouin fiber laser (MWBFL) worked stably during that time, but the stabilities become worse with higher SBS orders.

Passive harmonic mode-locking in Tm–Ho doped fiber laser with MoS2–ZnO saturable absorber deposited on the arc-shaped fiber

This work reports a harmonic mode-locked Tm–Ho doped fiber laser (THDFL) using newly fabricated MoS2–ZnO as a saturable absorber (SA). It generates harmonic mode-locking (HML) operation with a center wavelength of 1911.4 nm and a 3-dB bandwidth of 3.02 nm. The fundamental repetition rate and pulse width were 14.1 MHz and 2.05 ps, respectively. Based on the radio frequency (RF) spectrum, the observed signal-to-noise (SNR) of the fundamental HML pulse was 67.22 dB. Increasing the pump power with fine-tuning of the polarisation controller (PC), higher order HML pulses were also observed using the MoS2–ZnO SA. The highest stable HML frequency was 300 MHz, observed at the 21st HML. The central wavelength and 3-dB bandwidth of the HML pulse were 1915.2 nm and 2.29 nm, respectively. The 21st HML pulses demonstrated a SNR of 40.09 dB. No supermode noise was observed in the RF spectrum, indicating that the 21st HML pulses were relatively stable. With industry demand, this high repetition rate HML with MoS2–ZnO SA opens new avenues for comprehension and manipulation of electronic phenomena, paving the way for future innovations in ultrafast lasers.

Microsecond and nanosecond pulse initiator by Mo2Ga2C DSF saturable absorber (SA) with EDFL ring cavity

This paper elaborated the generation of microsecond and nanosecond pulse fiber laser using Mo2Ga2C coating onto DSF. The microsecond pulse commenced at the pump power of 39.826 mW and increased to 81.37 mW with a pulse width of 7.02 µs–5.92 µs. Meanwhile, the repetition rate showed measurements between 42.63 kHz to 64.6 kHz corresponding to the maximum pulse energy of 150.15 nJ. Besides that, the nanosecond pulse was generated with an additional length of 200 m for the SMF. The dual wavelength nanosecond pulse began at the pump power of 95.22 mW with a pulse width of 273.7 ns corresponding to the repetition rate of 961.8 kHz. Maximum pulse energy and maximum peak power were 8.75 nJ and 28.15 mW, respectively. The Mo2Ga2C coated DSF acted as the SA and was integrated into an erbium doped fiber laser cavity. The modulation depth of the Mo2Ga2C DSF SA was approximately 7.2 %.

Ultra-narrow linewidth in continuous-wave external cavity diamond Raman laser

A continuous-wave narrow linewidth diamond Raman laser based on an intracavity frequency doubling structure was demonstrated. Linewidth narrowing and power enhancement were realized by tuning the phase matching in the second-harmonic generation element through temperature control. A maximum output power of 5 W at 592 nm with a linewidth of 72 MHz was obtained using a Yb doped fiber laser with a power of 40 W and a linewidth of >4 GHz, an enhancement of the linewidth by a factor of about 65. The results indicate that high-power and narrow linewidth lasers can be produced utilizing diamond Raman conversion combined with the phase matching in the second-harmonic generation element.

Nd3+-doped Fiber Laser at 1000-1100nm

Fiber optic amplifiers have revolutionized telecommunications by enabling efficient signal amplification over long distances. Their development stems from the increasing demand for high-speed data transmission and the limitations of traditional electronic amplifiers. Fiber amplifiers utilize rare-earth-doped fibers to boost optical signals, offering advantages in bandwidth, reliability, and cost-effectiveness. Nd3+-doped fiber laser is one of the focal topics of current research. Researchers have found advancements in the application of Nd3+-doped fiber laser at wide wavelengths. However, there still exist uncertainties in applying Nd3+-doped fiber laser at 1000-1100nm. Therefore, this paper aims to design a Nd3+-doped fiber laser at 1000-1100nm. The research methodology of this paper is as follows: using numerical simulation via Matlab. Research finds that Nd3+-doped fiber laser at 1000-1100nm is theoretically applicable. The results of this research will promote the development of optical fiber. Through an in-depth exploration of new materials and application technologies, it will bring breakthroughs in optical fiber communication, optical sensing, laser technology, and other fields. This will promote the improvement of laser performance and provide a more reliable and efficient basis for future scientific research and engineering applications.

Design of 1450-1500nm Bismuth-doped Fiber Laser

With the rapid development of information technology, people's demand for the transmission capacity of fiber optic communication networks is increasing. How to broaden the bandwidth of communication systems has become one of the key issues in the field of communication. Researchers have found that the operating bandwidth of amplifiers mainly limits the bandwidth of communication systems. Although multiple solutions have been proposed and implemented to address this issue, there are still many gaps in the design of full-band multi wavelength-related light sources. By studying the three-level system of bismuth ions, the rate equation and power transfer equation of a bismuth ion doped fiber laser are simulated, and the pump power threshold and output power are calculated. Using MATLAB for simulation experiments, the relationship between laser power and pump power, as well as their variation with propagation distance, were ultimately obtained. The simulation results show that under 830 pump lights, the pump light threshold power is 10W. After reaching the threshold power, the pump light power and laser power have a linear relationship, and as the propagation distance increases, the pump light power gradually decreases and the laser power gradually increases. The analysis shows that the power generated by the signal light in this band meets the theoretical standards, which verifies the correctness of the scheme.

All-PM Yb-doped mode-locked fiber laser with high single pulse energy and high repetition frequency

We demonstrate an all-polarization-maintaining (PM) ytterbium (Yb)-doped fiber laser with a figure-of-9 structure to generate mode-locked pulses with high single pulse energy and high repetition frequency. By exploiting the nonlinear amplifying loop mirror, a stably self-started mode-locking is achieved with a spectrum bandwidth of 13 nm and a pulse duration of 4.53 ps. The fundamental frequency is 97.966 MHz at the maximum output power of 143 mW in single pulse mode-locked operation, corresponding to the single pulse energy is 1.46 nJ. The output pulses maintain both high repetition frequency and high single-pulse energy. This laser oscillator can be an ideal seed source for applications such as high-energy amplifiers.

Mode-locking in holmium doped fiber laser operating at 2.06 µm using manganese violet

Mode-locking in holmium doped fiber laser operating at 2.06 µm using manganese violet

Broadband noise-like pulses in fiber laser based on a filter

We report on the generation of broadband noise-like pulses in an Er:Yb doped fiber laser with a tunable bandpass filter in the cavity. Benefit from the filter enhanced spectrum at shorter wavelengths and Raman effect assisted spectrum at longer wavelengths, an excellent flat spectrum with a 3 dB spectral width of 130.2 nm is obtained. This is different from previous traditional methods to achieve broadband noise-like pulses, and the results also represent the widest spectrum directly obtained in an erbium doped fiber laser without the use of any special fibers within the cavity.