Tunable Mode-locked Fiber Laser Research Articles

L-band of ∼ 1.6 μm tunable multi-wavelength mode-locked Er-doped fiber laser with an MMF- FMF based structure

1.6 μm tunable mode-locked fiber laser are mainly used in the biomedical field, laser processing, and other aspects, have excellent application prospects. We propose a novel MMF-FMF-based device, which acts both as a saturable absorber and a wavelength selection filter. The reduction of insertion loss caused by FMF affects the laser gain competition process, leading to changes in gain allocation and bandwidth allocation. The laser generated stable mode-locked pulses with a repetition frequency of 23.23 MHz at pump powers exceeding 51 mW. By adjusting the angle of the fiber optic squeezer with the PC, successfully achieved switchable single-, dual-, and triple-wavelength lasing outputs, as well as tunable single- and dual-wavelength lasing outputs. The wavelength-tuning ranges for the single- and dual-wavelength lasing outputs were 31 nm (1570 nm-1601 nm) and 24 nm, respectively. The accurately adjustable L-band novel mode-locked fiber laser exhibits enormous potential for application.

Optically tunable mode-locked fiber laser using long-period grating coated with multiwall carbon nanotubes

We demonstrate an optically tunable mode-locked fiber laser using long-period fiber grating (LPFG) coated with multi-walled carbon nanotubes (CNTs). The multi-walled CNTs can absorb light to convert it into thermal energy, and the resonance wavelength of the grating can be easily turned by varying the external modulated light power. This multi-walled CNT coated LPFG-based all-optical fast and efficient spectrum tunable filter enables continuous tuning of the central wavelength of the laser by manipulating the loss of the mode-locked laser, ensuring the stability of the mode-locking state. In the absence of modulated light on multi-walled CNTs, the soliton laser could generate 890 fs pulses at 1546.7 nm with a spectrum bandwidth of 3.26 nm and a signal-to-noise ratio of 73.1 dB. Through adjustment of the pump power of the modulation light on multi-walled CNTs, the mode-locked fiber laser can be continuously tuned from 1546.71 to 1563.15 nm. The response time of the optically tunable system was measured to be in the order of hundreds of milliseconds. The presented optical tuning filter shows great potential in the fiber laser system, offering a repeatable, straightforward, and rapidly responsive laser tuning technique.

C- and L-Bands Wavelength-Tunable Mode-Locked Fiber Laser

We report a single-wavelength tunable mode-locked fiber laser. The single wavelength can be tuned from 1537.49 nm to 1608.06 nm by introducing a Sagnac loop filter. As far as we know, this is the widest single-wavelength tuning range achieved in an erbium-doped mode-locked all-fiber laser based on nonlinear amplifying loop mirror (NALM). The laser’s pulse width changes from 549 fs to 808 fs throughout the tuning process, the maximum average output power is 5.72 mW, and the single-pulse energy is 0.34 nJ at a central wavelength of 1556.53 nm. This laser source can serve as an efficient tool for applications that require a broad tunability range. The combination of femtosecond pulses and extensive wavelength tuning capabilities makes this laser system highly valuable in fields such as fiber optic communications, spectroscopy, sensing, and other applications that benefit from ultrafast and tunable laser sources.

Electrically tunable mode-locked fiber laser using laser induced graphene assisted long-period fiber grating

We demonstrate an electrically tunable all-fiber mode-locked erbium-doped fiber laser using a long-period fiber grating (LPFG) assisted by laser induced graphene heaters (LIG-H). Wavelength tunability is achieved by the temperature-dependent transmission spectrum of the LPFG. The central wavelength can be continuously tuned from 1549.00 nm to 1563.63 nm with a spectral tuning range of 14.63 nm. The graphene on polyimide (PI) paper is fabricated using a 10.6 μm CO2 laser, which has a maximum operating temperature of around 500 °C. The proposed LPFG-based electrical tunability of mode-locked fiber laser provides a novel, repeatable, simple, and cost-effective laser tuning technique.

L-band filter-less wavelength tunable mode-locked fiber laser incorporating a long-period fiber grating

The influences on the tuning range of a wavelength-tunable L-band mode-locked fiber lasers incorporating a long-period fiber grating (LPFG) are investigated. Through controlling both resonance wavelength and bandwidth of the LPFG, the net gain of the laser can be designed appropriately, hence leading to an optimized tuning range of the L-band mode-locked lasers. A wide spectral tuning range of 23.98 nm is obtained when using the LPFG with 21.60 nm bandwidth. Benefiting from the narrow band optical attenuation characteristic of LPFG, the lowest power variation of the laser is merely 4.15 µW/nm. Moreover, theoretical gain analysis corresponds to the experimental observation well.

Tunable mode-locked fiber laser based on nonlinear multimode interference with double offset-splicing step-index few-mode fiber.

A tunable mode-locked all-fiber Yb-doped laser with a double offset-splicing step-index few-mode fiber (DOS-SIFMF) is demonstrated, to the best of our knowledge, for the first time. The structure of DOS-SIFMF, which constructs a micro Mach-Zehnder interferometer as a consequence of introducing offset splicing, has characteristics of both a saturable absorber and filter and is more accessible to obtain mode-locking operation in an all-normal dispersive region. The results of simulation show that interference with fewer modes is more reliable to acquire mode-locking operation of the fiber laser. The central wavelength, spectrum, and pulse widths are 1032 nm, 6.15 nm, and 28.8 ps, respectively. The output pulse in time and spectrum domains can be tuned in the range of 168.7 ps and 10.7 nm, respectively. This structure has effects of both mode-locking and filtering, showing potential application in communication and sensing. Furthermore, the influence on mode number to interference is generally discussed in the end.

Tunable mode-locked fiber laser to generate ultrashort cylindrical vector beams

In this work, we report a tunable mode-locked fiber laser that can produce ultrashort laser pulses with polarization vortex. Two vortex wave plates (VWPs) are employed in this laser to convert the intracavity beam states between the Gaussian mode and cylindrical vector mode. By adjusting the angle between a diffraction grating and the light beam in the cavity, the center wavelength of the mode-locked pulse can be tuned from 1015 nm to 1030 nm. Mode-locked pulses with full width at half maximum of 1.51 ps with the maximum single pulse energy of 2.2 nJ have been obtained. Through synchronously adjusting the orientations of the two VWPs, the output mode can be switched between radial polarization and azimuthal polarization states. The output vortex pulse from the tunable mode-locked fiber laser may find many applications such as optical manipulation, imaging and laser micro-machining.

C+L band wavelength and bandwidth tunable fiber laser incorporating carbon nanotubes

Spectral wavelength and bandwidth tunable mode-locking ultrafast fiber laser has widespread applications in the fields of optical telecommunication, spectroscopy, pump-probe measurements, and so on. Here, we report an single-wall carbon nanotube (SWCNT)-based wavelength and bandwidth tunable mode-locked fiber laser operation in the C[Formula: see text]L band. The output spectral wavelength and bandwidth can be continuously tuned by adjusting the intra-cavity tunable filter with a wavelength tuning range spanning [Formula: see text]70 nm (from 1539.8 nm to 1610.1 nm) and bandwidth from 0.5 nm to 4.5 nm, respectively. Our results provide a compact, mode-locked fiber laser wider in tuning range than the other systems for various applications requiring variable spectral wavelength or bandwidth.

All-fiber short-wavelength tunable mode-locked fiber laser using normal dispersion thulium-doped fiber.

We report an all-fiber high pulse energy ultrafast laser and amplifier operating at the short wavelength side of the thulium (Tm) emission band. An in-house W-type normal dispersion Tm-doped fiber (NDTDF) exhibits a bending-induced distributed short-pass filtering effect that efficiently suppresses the otherwise dominant long wavelength emission. By changing the bending diameter of the fiber, we demonstrated a tunable mode-locked Tm-doped fiber laser with a very wide tunable range of 152 nm spanning from 1740 nm to 1892 nm. Pulses at a central wavelength of 1755 nm were able to be amplified in an all-fiber configuration using the W-type NDTDF, without the use of any artificial short-pass filter or pulse stretcher. The all-fiber amplifier delivers 2.76 ps pulses with an energy of ∼32.7 nJ without pulse break-up, due to the normal dispersion nature of the gain fiber, which marks so far, the highest energy amongst fiber lasers in the 1700 nm-1800 nm region.

Demonstration of a microelectromechanical tunable Fabry-Pérot cavity based on graphene-bonded fiber devices.

Taking advantage of the high thermal conductivity of graphene, this Letter demonstrates a microelectromechanical (MEM) tunable Fabry-Pérot (F-P) cavity, based on a graphene-bonded fiber device (GFD), which acts as a microheater. By increasing the electric current from 0 to 8mA in the heater, the temperature of the GFD can rise and approach a value of 760K theoretically. This high temperature will cause a deformation of the fiber, allowing the graphene-bonded fiber end to form a gap-adjustable F-P cavity with a cleaved single-mode fiber. The gap in the cavity can be reduced by increasing the current applied, leading the transmittance of the cavity to change. In this work, a highly sensitive current sensor (5.9×105 nm/A2) and a tunable mode-locked fiber laser (1.2×104 nm/A2) are created based on the MEM tunable F-P cavity.

High-performance tunable, self-similar fiber laser.

We report a tunability study of a mode-locked Yb-doped self-similar fiber laser. The center wavelength is tunable from 1030 to 1100nm without losing mode locking by adjusting a narrow intracavity spectral filter. Undesirable amplified spontaneous emission is suppressed by heating up the gain fiber. As a tunable mode-locked fiber laser, the performance (∼100 fs and ∼4 nJ) is exceptional owing to a unique self-similar pulse evolution.

基于倾斜光纤光栅的连续可调谐锁模激光器

基于倾斜光纤光栅的连续可调谐锁模激光器

Influence of spectral filtering on mode-locking operation of figure-eight Er-doped fiber laser

Over the last decades, passive mode-locked fiber laser has received considerable attention because of ultrashort pulse, compactness, and low cost. As a saturable absorber, nonlinear optical loop mirror (NOLM) has shown the advantages of high damage threshold, possibility of all-PM fiber implementation, short response time and therefore potentially low intrinsic noise. Spectral filtering plays an important role in NOLM mode locked fiber laser, but the influence of filtering parameters on mode locking operation is rarely reported. In this paper, the influence of filtering bandwidth on mode locking operation and on output pulse characteristics are experimentally investigated. A 2 × 2 optical coupler with a splitting ratio of 10 : 90 is introduced at one end of fiber loop to form a loss-imbalanced NOLM, and extracts 90% of intracavity pulse energy as outputs. With this architecture, an all polarization-maintaining figure-8 Er-doped fiber ultrafast laser is achieved. A home-made bandwidth and wavelength tunable bandpass filter is utilized in the cavity, and the filtering bandwidth is defined by 10 dB bandwidth. The clockwise and counter-clockwise mode locked output power are 8.4 mW and 8.6 mW, respectively, with a repetition rate of 2.734 MHz. With a spectral bandwidth of 2.1 nm, the intracavity pulse is shaped by spectral filtering and soliton effect. The 3 dB bandwidth of the clockwise and counter-clockwise mode locked output pulse are 10.1 nm and 1.8 nm, and the values of corresponding full width at half maximum (FWHM) of the direct outputs are 583.7 fs and 2.94 ps, respectively. As the filtering bandwidth increases, the role of filter in spectral shaping weakens, and the parameters of two output pulses become close. When spectral bandwidth is larger than 7.3 nm, the intracavity pulse is shaped by gain spectrum and soliton effect. Both of the clockwise and counter-clockwise output pulses become the transform-limited pulses with almost the same FWHMs of 440 fs. Besides, the wavelength of the figure-8 fiber laser can be adjusted in a range larger than 30 nm by modulating the wavelength of the filter. The tunable mode-locked fiber laser has great potential applications in various application fields.

可调谐锁模光纤激光器泵浦的超连续谱光源

可调谐锁模光纤激光器泵浦的超连续谱光源

Optofluidic tunable mode-locked fiber laser using a long-period grating integrated microfluidic chip.

An optofluidic tunable mode-locked fiber laser using a microfluidic chip integrated with long-period grating (LPG) is presented. The microfluidic chip enables ultrafine adjustment of the liquid's refractive index and, thus, LPG's spectrum via tuning the mixing ratio of the microfluidic flows. With such an optofluidic spectrum-tunable filter, the central wavelength of the mode-locked laser can be tuned continuously, while the mode-locking state is steadily maintained. The mode-locked pulses are measured with a pulse duration of 0.9 ps and repetition rate of 12.14 MHz, respectively. Moreover, bound solitons with variable soliton separations are experimentally demonstrated.

Wavelength tunable ultrafast fiber laser via reflective mirror with taper structure.

Laser sources with a controllable flexible wavelength have found widespread applications in optical fiber communication, optical sensing, and microscopy. Here, we report a tunable mode-locked fiber laser using a graphene-based saturable absorber and a tapered mirror as an end mirror in the cavity. The phase layer in the mirror is precisely etched by focused ion beam (FIB) milling technology, and the resonant wavelength of the mirror shifts correspond to the different etch depths. By scanning the tapered mirror mechanically, the center wavelength of a mode-locked fiber laser can be continuously tuned from 1562 to 1532nm, with a pulse width in the sub-ps level and repetition rate of 27MHz.

Sub-nanometer tuning of mode-locked pulse by mechanical strain on tapered fiber

A tunable mode-locked fiber laser based on the non-linear polarization rotation (NPR) technique is proposed and demonstrated. A passively generated mode-locked output is obtained with a repetition rate of about 70ns and an average output power of 0.7mW, as well as a laser efficiency of 0.53%. The mode-locked pulses can be tuned over a span of 4.4nm, from 1560.6nm to 1556.2, corresponding to a stretching of the tapered fiber from 0 to 100µm in 10µm increments. The pulses have an average signal-to-noise ratio of about 41dB in the frequency domain, indicating a highly stable mode-locked output. The system can repeat and reverse the generation of these pulses, a crucial criterion of many communications and sensing applications.

Widely tunable mode-locked fiber laser using carbon nanotube and LPG W-shaped filter.

A widely tunable mode-locked fiber laser using a carbon nanotube absorber and a fiber-optic W-shaped spectral filter is presented. The W-shaped filter is constructed by sandwiching a phase-shifted long-period grating between two LPGs of different periods. By adjusting the temperature of the W-shaped filter from 23°C to 100°C, the central wavelength of the mode-locked fiber laser can be continuously tuned from 1597 to 1553 nm. The tuning range is further extended to 1531.6 nm when a shorter erbium-doped fiber is used in the fiber oscillator. The experimental results reveal that the large thermal tunability of the proposed LPG filter provides an effective approach to achieve compact widely tunable mode-locked fiber lasers covering both C and L bands.

1 μm波段宽带可调谐锁模光纤激光器

1 μm波段宽带可调谐锁模光纤激光器

Tunable mode-locked fiber laser and wavelength converter based on photonic crystal fiber

Tunable mode-locked fiber laser and wavelength converter based on photonic crystal fiber