Wavelength-tunable L-band mode-locked fiber laser using a long-period fiber grating

Abstract

We demonstrate an L-band wavelength-tunable passively mode-locked fiber laser using a single long-period fiber grating (LPFG) as a narrow-band optical attenuator (NBOA). Through bending the LPFG, the central wavelength can be continuously tuned from 1582.02 to 1597.29 nm, while the output power only varies from 1.465 to 1.057 mW, approximately a rate of 22 µW/nm variation. This is the first time that LPFG is functioned as a NBOA in mode-locked fiber lasers, showing the great advantage of less impact on output power variation reduction. Besides, the total cavity length is 5.08 m, which is the shortest length yet reported in wavelength-tunable mode-locked fiber lasers. The wavelength tuning could also be realized at harmonic mode locking with tuning range of 14.69 nm under 5th harmonic.

Methods of Radiation Wavelength Tuning in Short-Pulsed Fibre Lasers

“…The elements used for wavelength tuning of the radiation produced by short-pulsed fibre lasers include both those conventionally found in solid-state or other types of lasers (diffraction gratings [13][14][15], birefringent filters [16][17][18], prisms [19], acousto-optical filters [20], and so forth) and specifically fibre-optical elements (fibre Bragg gratings [21], specialty fibres [22,23], Sagnac filters [24], and so on) /Figure 1/. It should be noted that certain conventional spectral filters, such as birefringent, can be adapted to all-fibre configurations: plates are replaced by pieces of PM fibre and the role of polarisation-selective Brewster faces is played by polarisation sensitive isolators [18] inserted on either side of the PM fibre.…”

“…The problem with this method is the possibility of exceeding the threshold of plastic deformation in quartz, above which the modification of the grating period becomes irreversible. Restricted bending of the fibre allows reproducible tuning of the output radiation of mode-locked fibre lasers within a range of ~15 nm [22]. Sometimes, combined (simultaneous thermal and mechanical) action is applied to the fibre with a Bragg grating [39].…”

L-band wavelength-tunable fiber laser mode-locked by all polarization-maintaining nonlinear polarization rotation

“…A common method involves using a tunable bandpass filter for selecting the mode-locking wavelength. Devices like fiber Bragg Grating (FBG), long-period fiber grating (LPFG), and Sagnac loops have been extensively studied [5][6][7]. Moreover, research has focused on intracavity loss control using tunable-ratio optical couplers (TROC) or variable optical attenuators (VOA) [8,9].…”

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

“…Yet, such a mechanism of these filters has a great impact on the whole cavity gain, which can affect the stability of the passively mode-locked operation. In 2021, Jiang et al proposed a wavelength-tunable modelocked fiber laser ranging from 1582.02 to 1597.29 nm by mechanically bending the LPFG [23]. LPFG is preferable for use in fiber ring resonators to achieve tunable laser operation because it only suppresses the optical gain in the designed rejection band to allow lasing at unsuppressed wavelengths.…”