Fiber Laser Generation Research Articles

Wavelength-tunable high-repetition-rate pulse generation in a SOA-based fiber laser with gain instability

Abstract Introducing negative optical feedback into a semiconductor optical amplifier-based laser presents a straightforward and effective approach for generating high-repetition-rate pulses through the mechanism of self-sustaining cross-gain modulation. In this work, we demonstrate, for the first time, the tunability of high-frequency pulse generation over a wide wavelength range by adjusting the central transmission wavelength of a tunable filter. Our laser system achieved a full tuning range from 1480 nm to 1556 nm (76 nm) while maintaining pulsed lasing. Remarkably, the laser exhibited a maximum pulse contrast exceeding 85% over a tuning range of 43 nm, from 1505.7 nm to 1548.7 nm. At any wavelength within this range, stable, self-starting pulse generation was consistently achieved, with a pulse repetition rate of 1.3 GHz.

Large-mode-area Nd-doped anti-resonant phosphate fiber for high-power single-mode 900 nm laser generation

In this work, we propose an Nd-doped double-layer anti-resonant phosphate fiber with a core diameter of 50 µm for high-power single-mode 900 nm laser generation. Double-layer interlaced anti-resonant elements were designed here to enhance the fundamental mode confinement capability of the large-mode-area Nd-doped fiber core. Moreover, a double-layer F-P etalon formed between the anti-resonant elements and the inner cladding was analyzed for the first time for fiber loss manipulation. Single-mode operation in the 890–907 nm band with confinement loss lower than 0.1 dB/m can be achieved from the designed fiber. More importantly, high confinement loss larger than 100 dB/m is achieved for all the fiber modes around 1060 nm for four-level gain competition suppression in 900 nm Nd-doped fiber laser generation. A 900 nm fiber amplifier simulation based on the designed Nd-doped phosphate fiber shows that the parasitic lasing or even amplified spontaneous emission around 1060 nm can be effectively suppressed and a high-efficiency hundred-watt laser at 900 nm can be anticipated.

Cerium oxide for L-band Q-switched pulse laser generation

Cerium oxide (CeO2), a rare earth metal oxide belonging to the lanthanide group is a mature engineered nanoparticle that has been developed for various industry applications. The nanoparticle features defects in its lattice structure, which is highly advantageous for bandgap tuning, and is acclaimed for its least cytotoxicity among other metal oxides. In this work, CeO2 is employed as a saturable absorber (CeO2-SA) in the generation of an L-band Q-switched erbium-doped fiber laser. Q-switching was attained at 33.33 mW pump power threshold with a central wavelength of 1600.512 nm. Within 33.33 mW to 153.20 mW pump power range, the Q-switched laser obtained pulse repetition rates between 11.00 to 34.48 kHz, and pulse widths between 39.0 to 12.0 µs, with a high maximum pulse energy of 410 nJ. The Q-switched fiber laser remained stable over a 45-minute observation time at 153.20 mW pump power. The room temperature and direct mechanical deposition fabrication technique of the CeO2-SA in this work demonstrates the extreme simplicity and low cost of the device, which would reduce the overall cost and facilitate a wider technology adoption of pulse laser systems.

15.5 W, pulsed 630 nm generation based on Raman fiber laser and second-harmonic generation

We present a high-power, nanosecond 630 nm beam generation based on Raman conversion and second-harmonic generation (SHG). 116.2 W, single-mode 1080 nm fiber laser based on 10/125 µm optical fiber is used as a pump source for Raman conversion and the 1260 nm seed laser diode helps the amplification of third-order Raman conversion, which results in 63.7 W at 1260 nm with 54.8% Raman conversion efficiency. SHG to 630 nm is based on type-I noncritical phase-matching conditions with bismuth triborate (BIBO) nonlinear crystal. The average power of 630 nm is 15.5 W at a repetition rate of 9.26 MHz, a pulse width of 16.0 ns, and a SHG efficiency of 24.4%. This result can facilitate the generation of a high-power visible light source with good beam quality at a specific wavelength.

Passively harmonic dissipative soliton generation in normal dispersion erbium-doped fiber laser using SMS fiber as artificial saturable absorber

Passively harmonic mode-locking has been experimentally demonstrated in an erbium-doped fiber laser with large normal dispersion using single-multi-single mode structure as artificial saturable absorber. By increasing the pump power under the same polarization setting, the mode-locking operation can switch from fundamental mode-locked to 5th order harmonic mode-locked. Highest repetition rate of 4.26 MHz (5th order harmonic) is observed, with pulse width and pulse energy ascertained at 290 fs and 3.0 nJ, respectively. Excellent signal-to-noise ratio (SNR) of above 50 dB is observed for all harmonic orders. The findings validated that SMS structure can be used to generate stable and switchable high order of harmonic mode-locked. The low-cost SMS fiber for harmonic mode-locked generation technique could lay the groundwork for future sustainable industrial growth.

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 %.

Molybdenum gallium carbide coated D-shape fiber for nanosecond dark pulse generation in erbium-doped fiber laser

Molybdenum gallium carbide (Mo2Ga2C), a material belongs to MAX phase group, has garnered significant interest in a wide range of scientific field, including material science, engineering, and laser physics. It is chemically and structurally promising since it exhibits a low shear modulus, superconducting behaviour, and high mechanical stability. Here, we prepared a saturable absorber (SA) based on Mo2Ga2C coated D-shape fiber using solution casting technique. It exhibits outstanding saturable absorption of 7.2%, allowing it to generate dark pulse laser in an erbium-doped fiber laser cavity. We analyzed the laser’s performance and obtained a dark pulse with a pulse energy, peak power, and average output power of 3.9 nJ, 27.5 mW, and 7.3 mW, respectively. This foundational work may introduce a new material as an alternative SA device in fiber laser cavity.

Cerium oxide/polydimethylsiloxane polymer deposited onto tapered fiber for 1.97 µm mode-locked thulium-doped fiber laser

This work presents the use of cerium oxide (CeO2) as saturable absorber (SA) in the mode-locked pulse fiber laser generation. The CeO2 materials were prepared through sonication which then incorporated into a polydimethylsiloxane (PDMS) polymer to be coated on a tapered fiber. The CeO2/PDMS-SA exhibited saturation intensity of 44 MW/cm2 and modulation depth of 3.4%, confirming its nonlinear intensity-dependent transmission characteristics. Integrated into a thulium-doped fiber laser cavity, the CeO2/PDMS-SA enabled mode-locking at a pump power of 420 mW, leading to a fundamental mode-locking operation up to 1484 mW within the net anomalous dispersion regime. The laser emitted pulses at wavelength of 1973 nm with signal-to-noise ratio of 54 dB, repetition rate of 9.04 MHz and pulse width of 1.49 ps. The CeO2/PDMS-SA mode-locked fiber laser demonstrated stability of an average 3 dB bandwidth of 2.89 ± 0.08 nm, average central wavelength of 1973.05 ± 0.14 nm and average pulse width of 1.5 ± 0.01 ps for the duration of 120 min. Notably, the CeO2/PDMS-SA demonstrated a high pulse energy of 10.62 nJ and average output power of 96 mW. This investigation suggests their viability for use in future studies. The results also demonstrated the potential of CeO2 for use in various photonics applications in the “eye-safe” region.

Spider silk biological material for Q-switched temperature sensor

Abstract A temperature sensor using compact design and highly sensitivity of side polished fiber and fiber Bragg grating as the sensing elements, Q-switched pulse fiber laser source with spider silk as a saturable absorber is proposed and demonstrated. Spider silk sample was gently collected from a live spider, specifically, the jumping spider of Plexippus sp. which then incorporated within the laser cavity by deposited the silk onto the surface of the fiber ferrule to facilitate the generation of Q-switched pulse fiber laser. The temperature variations were detected by monitoring the pulse train and radio frequency shift from the oscilloscope. The performance of the side polished fiber sensor probe shows a sensitivity of 0.1522 kHz/°C, with 0.9479 coefficient of determination value as the temperature increased from -0.5 °C to +3.1 °C. Besides, a linear temperature re-sponse in the range of 25 °C – 55 °C with a sensitivity of 0.0423 kHz/°C, and a linear correlation coefficient of 0.951 was experimentally achieved for a fiber Bragg grating device. The spider silk as a saturable absorber material is compatible with fiber optic interconnection and the temperature sensing characteristics were successfully demonstrated. The sensor's straight-forward design further enhances its desirability as a sensor for temperature monitoring, including in the field of biological treatments, consumer electronics, detection of chemical analytes, and medical diagnosis.

High-efficiency radiation-balanced Yb-doped silica fiber laser with 200-mW output.

The focus of this study was the development of a second generation of fiber lasers internally cooled by anti-Stokes fluorescence. The laser consisted of a length of a single-mode fiber spliced to fiber Bragg gratings to form the optical resonator. The fiber was single-moded at the pump (1040 nm) and signal (1064 nm) wavelengths. Its core was heavily doped with Yb, in the initial form of CaF2 nanoparticles, and co-doped with Al to reduce quenching and improve the cooling efficiency. After optimizing the fiber length (4.1 m) and output-coupler reflectivity (3.3%), the fiber laser exhibited a threshold of 160 mW, an optical efficiency of 56.8%, and a radiation-balanced output power (no net heat generation) of 192 mW. On all three metrics, this performance is significantly better than the only previously reported radiation-balanced fiber laser, which is even more meaningful given that the small size of the single-mode fiber core (7.8-µm diameter). At the maximum output power (∼2 W), the average fiber temperature was still barely above room temperature (428 mK). This work demonstrates that with anti-Stokes pumping, it is possible to induce significant gain and energy storage in a small-core Yb-doped fiber while keeping the fiber cool.

Generation of vector soliton mode-locked Er-doped fiber laser using ZrTe2 as saturable absorber

We demonstrate a passively mode-locked fiber laser employing zirconium telluride (ZrTe2) as saturable absorber and illustrate its application for vector soliton generation in erbium-doped fiber lasers. By tuning the pump power and polarization controller, stable mode-locked operations in different operations are obtained with different cavity lengths. In addition, we also further research on characteristics of the vector solitons formed in fiber laser. The vector features of the obtained solitons are experimentally explored, and these solitons are proved to be group velocity locked vector solitons. Our research results indicate that ZrTe2 nanosheets could be available saturable absorber for ultrashort pulse fiber lasers, especially for generating vector soliton pulses in fiber lasers.

Raman-scattering-assisted noise-like pulse generation in an all-PM NOLM-based mode-locked fiber laser core-pumped by a 978 nm fiber laser

Stable Raman-scattering-assisted noise-like pulse is experimentally demonstrated in an all polarization-maintaining ytterbium-doped ‘nine-shaped’ mode-locked fiber laser based on nonlinear optical loop mirror. The pump source is a self-made single mode 978 nm fiber laser with a maximum output power of 8.45 W. Different pulse states are investigated through dispersive Fourier transform technology. First and second order Raman pulses are generated effectively with only 7.2 m length large-mode-area fiber. Numerical simulation is conducted to investigate the effect of gain fiber length on output laser wavelength. The output spectrum ranges from 980 nm to 1175 nm, the short-wavelength edge almost extends to the 978 nm pump wavelength, which is benefitted from the core-pumping scheme providing extremely high population inversion for gain fiber, as well as the short length YDF of 0.2 m suppressing reabsorption of radiation laser. The polarization extinction ratio is experimentally measured by a spectral subtraction method to be larger than 28 dB at each wavelength between 1010 nm and 1120 nm.

Violet phosphorene as a saturable absorber for controllable soliton molecule generation in a mode-locked fiber laser

Controllable soliton molecules were generated in a Er-doped mode-locked fiber laser with a few-layered violet phosphorene saturable absorber.

CW and Pulsed Generation of Short Cavity Yb-doped Phosphosilicate Fiber Laser

CW and Pulsed Generation of Short Cavity Yb-doped Phosphosilicate Fiber Laser

Q-switched Erbium Doped Fiber Laser Generation Using the Kerr Effect of Multimode Interference

This work demonstrates a single mode fibre-step index multimode fibre-single mode fibre (SMS) structure as saturable absorber (SA) to generate Q-switched laser based on the Kerr-effect of multimode interference (MMI) in an Erbium-doped fibre laser (EDFL) cavity. A 156 mm length of step index multimode fibre (SIMF) was spliced directly into a ring cavity to modulate the cavity loss. By bending and applying proper pressure on the SIMF, steady Q-switched pulse was generated without strict length restriction of the SIMF. The Q-switched laser had a high repetition rate from 87 to 158 kHz, while the corresponding pulse width was low, ranging from 4.2 μs to 2.5 μs as the pump power increased from 115 to 342 mW. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was about 67 dB at a central wavelength of 1530 nm. The experiment demonstrated that SMS structure can be used as stable SA to generate Q-switched laser for high power applications. It also indicated that even with large core diameter step index multimode fiber, SMS structure can be utilized to generate stable Q-switched pulsed laser with very simple cavity settings.

Q-switched fiber laser generation utilizing metal oxide-based saturable absorber in the region of 1.0 µm and 1.5 µm

In this study, we explored a saturable absorber (SA) using a metal oxide-biopolymer film, resulting in the generation of Q-switched fiber lasers at 1.0 µm and 1.5 µm wavelengths. A straightforward sonochemical technique was employed to synthesize a nickel oxide (NiO) film in cooperation with Chitosan as a host polymer. The fabricated NiO-Chitosan film exhibits nonlinear absorption properties with modulation depth of 32.20%, saturation intensity of 0.43 kW/cm2, and non-saturable loss of 7.80%. Upon integrating the NiO-Chitosan film into the cavities of Erbium-Doped Fiber Laser (EDFL) and Ytterbium-Doped Fiber Laser (YDFL), the emergence of stable self-starting Q-switched pulsed lasers were observed at 1040.86 nm and 1557.60 nm central wavelength, respectively. Notably, the shortest pulse widths of 0.73 µs and 2.44 µs were achieved, along with maximum repetition rates of 111.61 kHz and 61.73 kHz, respectively, at these wavelengths. Our investigation identifies an effective SA material with good nonlinear absorption properties for inducing Q-switching in the 1.0 µm and 1.5 µm regions. Significantly, the Chitosan properties, encompassing biocompatibility, non-toxicity, and high thermal resistance, combined with the uncomplicated NiO fabrication process and cost-effectiveness, hold promise for diverse applications.

All-fiber Q-switched erbium-doped fiber laser generation with SMF-SIMF-SMF structure as artificial saturable absorber

A passively Q-switched Erbium-doped fiber laser (EDFL) was successfully demonstrated using SMF (single-mode fiber)-SIMF (step-index multimode fiber)-SMF or SMS structure as a saturable absorber (SA). The SMS structure operates on the Kerr-effect of multimode interference (MMI). To modulate the cavity loss, a 158 mm length of SIMF was fusion spliced into a ring cavity. By properly adjusting the in-line polarization controller (PC) that holds the SIMF, we were able to generate steady Q-switched pulses. As the input pump power increased from 115 to 343 mW, the repetition rate of the Q-switched laser increased from 87 to 158 kHz, while the corresponding pulse width decreased from 4.2 µs to 2.5 µs. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was around 72 dB at a central wavelength of 1530 nm. Our results indicate that the SMS structure can be used as an SA to generate stable Q-switched EDFL with very simple cavity settings.

Effective Kerr lens mode locking in Er3+:ZBLAN fiber laser with phase mismatched periodically poled lithium niobate

We theoretically introduce an effective Kerr lens mode locking concept to a polarization maintaining (PM) Er3+:ZBLAN fiber laser and generate a stable femtosecond pulse train at 2.76 µm. Phase-mismatched periodically poled lithium niobate (PPLN) is utilized to implement cascaded second order nonlinearities (CSN) for the effective Kerr lens mode locking. Furthermore, the CSN in the PPLN can be tuned to balance the huge fiber anomalous dispersion for femtosecond soliton formation in the mid-infrared regime. High coupling efficiency of light into fiber, shorter effective focal length of PPLN and larger effective nonlinear refractive index areessential for enhancing intracavity peak power and shortening pulse duration. The pulse could be compressed down to 311 fs with output pulse energy of 1.36 nJ and peak power of 3.6 kW. This mode locking method provides deep insight into direct generation of femtosecond fiber laser in mid-infrared regime.

Single-shot dynamics of dual-comb generation in a polarization-multiplexing fiber laser

Dual optical frequency combs have been a recurrent case of study over the last decade due to their wide use in a variety of metrology applications. Utilizing a single cavity laser to generate a dual comb reduces system complexity and facilitates suppression of common noise. However, a dual-comb regime in single cavity lasers tends to be more unstable and difficult to achieve. Therefore, having a better understanding about the way they are generated could improve and automate their generation and control. In this paper, we investigate the build-up dynamics and collision of dual comb in a polarization-multiplexing ring-cavity fiber laser using DFT (Dispersive Fourier Transform) method. We observe a bunch of meta-stable short-lived mode-locking states before the laser entered the dual-comb mode-locking state. The energy level of this short-lived initial pulses determines its evolution. If it decreases too much, the pulse will eventually collapse while if it stays above certain level, it will be successfully generated. The results presented in this paper increase the understanding of dual-comb generation inside a single cavity laser and may contribute in future attempts to increase the stabilization of this regime.

Highly stable pulsed fiber laser generation modulated by chromium iodide film

Abstract Highly stable pulsed fiber lasers are key optical components in optical communication, optical sensing, and precision micromachining systems due to the high beam quality, high peak power, and compact configurations. However, the available optical modulators in the fiber laser suffer from the operation bandwidth limitations and poor long-term physicochemical stability. Here, we have investigated the broadband nonlinear optical absorption behavior of the chromium iodide (CrI3) film, which exhibits broadband saturable absorption towards the mid-infrared regime and excellent long-term stability. The conventional soliton fiber laser operating at telecom wavelength has been obtained from an Er3+-doped fiber laser (EDFL) utilizing CrI3 film with a signal-to-noise ratio (SNR) of 92.4 dB and a pulse width of 492 fs. In addition, a passively Q-switched operation around 2.8 μm has also been obtained from an Er3+-doped ZBLAN fiber laser (EDZFL) modulated by the CrI3 film with a SNR of 46.8 dB and a pulse width of 766 ns. The demonstration shows that the CrI3 film exhibits robust broadband optical modulation, and may make inroads for developing highly stable ultrafast optoelectronic devices.