Erbium-doped Fiber Ring Cavity Research Articles

Passively mode-locked erbium-doped fiber laser by a Mo2TiC2 MXene saturable absorber

Mono- and few-layer MXenes have gained widespread use as a nonlinear material platform for saturable absorbers (SAs) when generating ultrafast mode-locked pulses. However, the manufacturing processes associated with these materials are intricate and require considerable expertise. Consequently, it would be intriguing to investigate whether bulk and/or nanoscale-layered MXenes can be used as a nonlinear optical material platform. In this study, we experimentally demonstrated a Mo2TiC2 MXene-based SA by depositing nanoscale-layered Mo2TiC2 MXene particles and a polyvinyl alcohol composite film onto a side-polished fiber device. The fabricated SA exhibited a modulation depth of 5.67% and a saturation intensity of 0.135 MW/cm2. By integrating the Mo2TiC2 MXene-based SA within an erbium-doped fiber ring cavity, we generated mode-locked pulses featuring a pulse width of 1.74 ps at a wavelength of 1557.9 nm. This investigation highlights the potential of nanoscale-layered Mo2TiC2 MXene to function as an efficient material platform for nonlinear photonics applications.

The fiber ring laser intra-cavity gas sensor for C2H2 and CO2 detection based on photoacoustic spectroscopy

In this paper, a two-component gas sensing system in the resonant cavity of the fiber ring laser based on photoacoustic spectroscopy (PAS) is designed by embedding the PAS cell into the laser resonant cavity. A ring cavity erbium-doped fiber (EDF) laser is built in this system, combined with a longitudinal resonant PAS cell to detect the PAS signal, and a custom-designed wavelength modulator uses the fiber bragg grating (FBG) to paste the piezoelectric transducer (PZT) for scanning and modulating the gas absorption wavelength. The gas concentration is calculated by the second harmonic (2f) PAS signal. Based on time division multiplexing (TDM) technology, the acetylene (C2H2) and carbon dioxide (CO2) is detected respectively by the time-sharing operation of C-band and L-band EDFs for different wavelengths output. The time-sharing operation of the two wavelength laser is realized through optical switches, which effectively avoids the laser power loss and the instability of each wavelength caused by the mode competition phenomenon of multiple wavelengths. The detection performance of C2H2 and CO2 is implemented under normal temperature and pressure. The PAS signal intensity is further improved by optimizing the wavelength modulation amplitude and incident laser power. The linear fit (R2) and minimum detection limit (MDL) of C2H2 and CO2 are 0.99821, 728 ppbv, 0.9994 and 503 ppmv respectively. It shows that the two-component gas sensing system designed in this paper has a good linear response and high sensitivity, and plays an important role on the multi-component gas detection.

Measurement of Paracetamol Concentration Using an Erbium-Doped Fiber Ring Cavity

Process Analytical Technology (PAT) has been increasingly used in the pharmaceutical industry to monitor essential parameters in real-time during pharmaceutical processes. The concentration of Active Pharmaceutical Ingredients (APIs), such as paracetamol, is one of these parameters, and controlling its variations allows for optimization of the production process. In this study, a refractometric sensor, implemented by an interrogation system based on an Erbium-Doped Fiber Ring Cavity (EDFRC), was presented and experimentally demonstrated. The Cavity Ring proposed included a 1 × 3 coupler. One port of the coupler was used to increase the optical power of the system through a Fiber Bragg Grating (FBG), and the other two ports were used as sensing head and reference. The sensor detected variations of paracetamol concentration with a sensitivity of [(−1.00 ± 0.05) × 10−3] nW/(g/kg) and a resolution of 5.53 g/kg. The results demonstrate the potential of this technology as a possible non-invasive PAT tool.

Erbium-doped fiber ring cavity assisted by an FBG and PS-FBG reflector for refractive-index measurements - INVITED

This work presents an interrogator system based on an erbium-doped fiber ring cavity for refractive-index measurements. This fiber ring cavity is assisted by a fiber Bragg grating and a phase-shift fiber Bragg grating, both with a similar central emission wavelength to increase the output power levels.

Revealing the Evolution from Q-Switching to Mode-Locking in an Erbium-Doped Fiber Laser Using Tungsten Trioxide Saturable Absorber

Passively Q-switching and mode-locking technologies can generate short pulses with durations that differ by several orders of magnitude widely used in different applications. Recently, Q-switching and mode-locking realized in an identical laser cavity with saturable absorbers was reported. The analysis of pulse conversion is helpful for us to further understand the pulse dynamics of a laser. In this paper, the pulse evolution from Q-switching, Q-switched mode-locking to mode-locking, is demonstrated by using a tungsten trioxide saturable absorber in a ring-cavity erbium-doped fiber laser. Firstly, self-started Q-switching at 1563 nm is observed, the repetition rate continuously increases, and the duration decreases when the pump power increased. Then, with an adjusting intra-cavity state of polarization under a high pump power level, stable Q-switched mode-locking pulses evolved from Q-switching, are observed. The amplitude of the emerged pulse sequence with a period of 36.8 ns, determined by cavity length, is modulated by the Q-switched envelope with the period of 10.3 μs. By optimizing the intracavity polarization carefully, stable continuous wave mode-locking operation is achieved eventually. To the best of our knowledge, this is the first experimental demonstration of Q-switching and mode-locking, respectively, in an identical transition-metal-oxides-based pulsed fiber laser without modification of cavity structure.

Ring Cavity Erbium-Doped Fiber for Refractive Index Measurements

In this study, an interrogation system based on an erbium-doped fiber ring cavity for refractive index measurements is presented and experimentally demonstrated. This cavity ring includes a 1 × 3 coupler wherein one of the fiber output ports is used to increase the optical power of the system by means of an FBG used as a reflector. The other two output ports are used as a refractive index sensing head and reference port, respectively. An experimental demonstration of this proposed sensor system for the measurement of a distinct refractive index is presented.

A kind of multiwavelength erbium-doped fiber laser based on Lyot filter

A multiwavelength tunable ring-cavity erbium-doped fiber laser (EDFL) based on a Lyot filter was presented. For the proposed Lyot filter, a comb filter consisting of an EDF-polarization-maintaining fiber (EDF-PMF), a polarization controller (PC), and a circulator with four ports was used to suppress the mode competition. The light transmission direction was guaranteed by the circulator. For the proposed fiber laser, tunable single, dual, triple, quadruple, quintuple, sextuple, and septuple wavelengths were realized. A single-wavelength laser output with an optical signal-to-noise ratio (SNR) of up to 30.56 dB was realized, and a tuning range of 1590.54 nm to 1599.54 nm was achieved by tuning the PC. The stability of the single, dual, triple, and quadruple-wavelength center power fluctuations was less than 0.05 dB, 0.98 dB, 5.07 dB, and 7.71 dB respectively. When the laser was operated in the multiwavelength condition, the SNR was more than 20.97 dB. The proposed erbium-doped fiber laser is suitable for fiber-sensing system applications.

Generation of Breathing Pulses in Erbium-Doped Fiber Ring Cavity

Generation of Breathing Pulses in Erbium-Doped Fiber Ring Cavity

Q-Switched and Mode-Locked Er-doped fiber laser based on MAX phase Ti2AlC saturable absorber

MAX phase materials, exhibiting excellent antioxidation, corrosion resistance and high electrical and optical conductivity, attract much attention. The nonlinear optical properties of the MAX phase Ti2AlC was demonstrated by measuring the saturable absorption of Ti2AlC- polyvinyl (PVA) film. The modulation depth of the Ti2AlC-PVA film is calculated to be 2.21%. Stable Q-switched and mode-locked pulses train were achieved in Erbium-doped fiber ring cavity by using Ti2AlC-PVA film as a saturable absorber. The maximum single pulse energy of the Q-switched laser was 92.8 nJ, and the pulse width of the mode-locked laser was 680 fs. This study shows the great potential of MAX phase materials for ultrashort laser pulses generation and provides some valuable design guidelines for the preparation of SAs based on MAX phase materials.

Investigation of nonlinear optical properties of rhenium diselenide and its application as a femtosecond mode-locker

We investigated the nonlinear optical properties of ReSe2. First, we measured the nonlinear absorption coefficient and the nonlinear refractive index of a ReSe2 thin film using open-aperture (OA) and closed-aperture (CA) Z-scan techniques. ReSe2 was shown to possess both saturable absorption and self-defocusing properties. The nonlinear absorption coefficient of ReSe2 was measured to be −(5.67±0.35)×103 cm/GW, and its nonlinear refractive index was −(2.81±0.13)×10−2 cm2/GW at 1560 nm. Next, a fiberized saturable absorber (SA) based on ReSe2 was fabricated with a side-polished fiber platform and was tested as an ultrafast mode-locker capable of producing femtosecond pulses operating at a wavelength of 1560 nm. The estimated modulation depth and saturation power are ∼3.9% and ∼42 W, respectively, for the transverse electric mode, while they are ∼2.4% and ∼53 W for the transverse magnetic mode. Using the prepared SA, stable soliton pulses with a temporal width of ∼862 fs were produced from an erbium-doped fiber ring cavity. To the best of the authors’ knowledge, this is the first demonstration of using a ReSe2-based SA for femtosecond mode-locked pulse generation.

Manipulation of Gaussian derivative pulses and vector solitons in fiber lasers with analytic modeling by the coupled complex Ginzburg–Landau equations

Both positive- and negative-polarity Gaussian monocycle and doublet pulses, for which the pulse shapes are the first and second derivatives of Gaussian functions plus some continuous-wave backgrounds respectively, are generated in a ring-cavity erbium-doped fiber laser from polarization-locked vector solitons by using passive optical technology. The pulse states are switchable and are found to be the superposition of bright and dark solitons with different widths, amplitudes, time delays, polarizations, and wavelengths. Qualitative analysis of the properties of vector solitons are performed by solving coupled complex Ginzburg–Landau equations, and analytic modeling of the fiber laser is presented. By representing the envelopes of bright soliton by sech- and dark soliton by tanh-based functions, the incoherent superposition of these two soliton components have simulated the experimental observations, and the underlying mechanisms for the formation of monocycle and doublet pulses are attributed to the polarization locking of bright and dark solitons. The theoretical modeling is used to calculate the pulse parameters of the fiber laser, and the intracavity birefringence can be estimated. The results of tunable optical vector solitons are compared with atomic solitons in the system of Bose–Einstein condensation. Since the governing equations for soliton generation in fiber lasers and Bose–Einstein condensation have many properties in common, thus the simulation and propagation of pulsating waves may open a new route to explore the classical solitary dynamics in nonlinear optics and its quantum analogy in ultracold fields.

Erbium Ring Fiber Laser Cavity Based on Tip Modal Interferometer and Its Tunable Multi-Wavelength Response for Refractive Index and Temperature

A tunable multi-wavelength fiber laser is proposed and demonstrated based on two main elements: an erbium-doped fiber ring cavity and compact intermodal fiber structure. The modal fiber interferometer is fabricated using the cost-effective arc splice technique between conventional single-mode fiber and microfiber. This optical fiber structure acts as a wavelength filter, operated in reflection mode. When the refractive index and temperature variations are applied over the fiber filter, the ring laser cavity provides several quad-wavelength laser spectra. The multi-wavelength spectra are tuned into the C-band with a resolution of 0.05 nm. In addition, the spectra are symmetric with minimal power difference between the lasing modes involved, and the average of the side mode suppression ratio is close to 37 dB. This laser offers low-cost implementation, low wavelength drift, and high power stability, as well as an effect of easy controllability regarding tuned multi-wavelength.

Erbium-doped fiber ring laser based on few-mode-singlemode-few-mode fiber structure for refractive index measurement

A novel Erbium-doped fiber ring cavity laser sensor for refractive index (RI) measurement based on a special designed few-mode-singlemode-few-mode structure is proposed and experimentally demonstrated. The few-mode fiber is a home-made concentric ring core fiber (CRCF) which can only support two scalar modes. Thus a stable mode interference occurs which functions as a sensing head and band-pass filter to select the lasing wavelength simultaneously. A sensitivity of −45.429nm/RIU is obtained in the range of 1.333–1.363. High optical signal to noise ratio (OSNR) of ∼45dB and narrow 3-dB bandwidth of ∼0.1nm indicate that the fiber ring laser sensing system has a high resolution and accuracy RI measurement.

A fiber ring cavity laser sensor for refractive index and temperature measurement with core-offset modal interferometer as tunable filter

In this paper, a fiber ring cavity laser refractive index (RI) and temperature sensor is presented. A core-offset Mach-Zehnder (MZ) interferometer is utilized as a sensing element as well as a filter. The core-offset distances of these two joints fabricated by a common fusion splicer are about 3.7μm, which well ensure the robustness and tensile strength. The directions of these two offsets are unnecessary to be controlled since low fringe visibility is acceptable in this sensor. The Erbium doped fiber (EDF) ring cavity laser setup is helpful to improve the spectral quality factor Q and the detection limit (DL). The Q value of this laser sensor can be higher than that of ordinary core-offset sensing structures by two magnitudes. By combining the core-offset MZ interferometer with EDF ring cavity laser, the final calculated detection limits for temperature and RI measurement are 0.35°C and 4.54×10−4, which are 10 times higher than those of the individual MZ interferometer. The proposed sensor possesses the advantages of low cost, simple operation and easy fabrication process.

Diaphragm based long cavity Fabry–Perot fiber acoustic sensor using phase generated carrier

A diaphragm based long cavity Fabry–Perot interferometric fiber acoustic sensor is proposed. The Fabry–Perot cavity is formed by a flat fiber facet and an ultra-thin silver diaphragm with a 6-meter long fiber inserted in the cavity. A narrow-linewidth ring-cavity erbium-doped fiber laser is applied to demodulate the sensing signal in the phase generated carrier algorithm. Experimental results have demonstrated that the phase sensitivity is about −140dB re 1rad/μPa at 2kHz. The noise equivalent acoustic signal level is 60.6μPa/Hz1/2 and the dynamic range is 65.1dB-SPL at 2kHz. The sensor is suitable for sensing of weak acoustic signals.

Chemical Wet Etching of an Optical Fiber Using a Hydrogen Fluoride-Free Solution for a Saturable Absorber Based on the Evanescent Field Interaction

We propose a chemical wet etching technique that does not make use of toxic Hydrofluoric solution to produce cladding-etched optical fiber intended for use as a platform for a fiberized saturable absorber. The wet etching technique is based on the use of a mixed solution of NH4F and (NH4)2SO4, which is not toxic, and a small, specially-devised etching cradle to achieve precise control of the etched fiber length. A fiberized saturable absorber was implemented by depositing the graphene oxide particles on top of the residual cladding for our cladding-etched fiber by using the drop & dry method. The saturable absorber was incorporated into an erbium-doped fiber ring cavity to test its suitability as a mode-locker with a modulation depth larger than 4.3%. Femtosecond pulses with a temporal width of ∼615 fs were readily obtained at a repetition rate of ∼17.09 MHz. The saturable absorption and laser performance of our saturable absorber were compared to those of an absorber on a core-etched fiber platform prepared through the formation of microdroplets of HF and surface tension-driven flow, as in [57] .

Q-switched Erbium-doped fiber laser at 1600 nm for photoacoustic imaging application.

We present a nanosecond Q-switched Erbium-doped fiber (EDF) laser system operating at 1600 nm with a tunable repetition rate from 100 kHz to 1 MHz. A compact fiber coupled, acousto-optic modulator-based EDF ring cavity was used to generate a nanosecond seed laser at 1600 nm, and a double-cladding EDF based power amplifier was applied to achieve the maximum average power of 250 mW. In addition, 12 ns laser pulses with the maximum pulse energy of 2.4 μJ were obtained at 100 kHz. Furthermore, the Stokes shift by Raman scattering over a 25 km long fiber was measured, indicating that the laser can be potentially used to generate the high repetition rate pulses at the 1.7 μm region. Finally, we detected the photoacoustic signal from a human hair at 200 kHz repetition rate with a pulse energy of 1.2 μJ, which demonstrates that a Q-switched Er-doped fiber laser can be a promising light source for the high speed functional photoacoustic imaging.

Fiber-integrated tungsten disulfide saturable absorber (mirror) for pulsed fiber lasers

We propose two schemes for achieving tungsten disulfide (WS2)-based saturable absorber (SA) and saturable absorber mirror (SAM). By utilizing the pulsed laser deposition method, we grow the WS2 film on microfiber to form an evanescent field interaction SA device. Incorporating this SA device into a common ring-cavity erbium-doped fiber (EDF) laser, stably passive mode-locking can be achieved with pulse duration of 395 fs and signal-to-noise ratio of 64 dB. We also produce a fiber tip integrated WS2-SAM by utilizing the magnetron sputtering technique (MST). This new type of SAM combines the WS2 layer as SA and gold mirror as high reflective mirror. By employing the WS2-SAM, we construct the linear-cavity EDF lasers, and achieve passive mode-locking operation with pulse duration of ∼1 ns and SNR of ∼61 dB. We further achieve stably passive Q-switching operation with pulse duration of ∼160 ns and pulse energy of 54.4 nJ. These fiber-integrated SAs and SAMs have merits of compactness and reliability, paving the way for the development of new photonic devices such as SAs for pulsed laser technology.

A pulse-width-tunable, mode-locked fiber laser based on dissipative soliton resonance using a bulk-structured Bi2Te3topological insulator

We experimentally demonstrate that a bulk-structured Bi2Te3 topological-insulator (TI)-based saturable absorber can be used with a dissipative soliton resonance based, nanosecond-pulse fiber laser. Our results show that temporal width-tunable, mode-locked pulses can readily be produced through the dissipative soliton resonance effect from an erbium-doped fiber ring cavity into which a bulk-structured Bi2Te3 TI-deposited, side-polished fiber has been incorporated. The temporal width of the output pulses was changeable from 2.7 to 12.8 ns with an increasing pump power, and the corresponding pulse energy increased linearly from 4.7 to 22.4 nJ. This paper reaffirms that a bulk-structured Bi2Te3 TI can be used as an effective material for saturable absorption, and that the material is readily applicable for different types of mode-locked fiber lasers.

Tungsten diselenide Q-switched erbium-doped fiber laser

We report a tungsten diselenide (WSe2) polyvinyl alcohol (PVA)-based, saturable absorber and related experiment results of a Q-switched fiber laser. WSe2-PVA film is synthesized by liquid phase exfoliation method, and its saturable absorption is measured via a nonlinear transmission experiment. The result shows that WSe2-PVA saturable absorber has a modulation depth of 3.5%, which means it has potential for generating an ultrafast pulse laser. We apply this absorber into a ring-cavity erbium-doped fiber laser and obtain Q-switched pulses under appropriate pump power. Our work demonstrates the reliable nonlinear optical characteristics of WSe2 and the feasibility for this two-dimensional material to be applied in the field of nonlinear optics.