Fiber Saturable Absorber Research Articles

High-Peak Power, All-Fiber Passively Q-Switched Laser Using a Sm-Doped Fiber Saturable Absorber

An all-fiber passively Q-switched Yb-doped fiber laser with fiber saturable absorber (SA) based on a piece of Sm-doped fiber is presented. For the first time, we observe the fast stimulated Brillouin scattering Q-switched process in an Yb/Sm all-fiber laser and obtain 41 ns pulses and 1.7 kW maximum peak power. Compared with the reported traditional SA Q-switched process, the pulse energy and peak power are both improved an order of magnitude. Furthermore, a traditional SA Q-switched process with 450 ns pulsewidth and 7.5 W peak power is also obtained in the same structure by increasing the feedback of cavity's output end.

Polarization-locked vector solitons in a mode-locked fiber laser using polarization-sensitive few-layer graphene deposited D-shaped fiber saturable absorber

We have experimentally demonstrated polarization-locked vector soliton generation in a passively mode-locked erbium-doped fiber laser by using a few-layer graphene deposited D-shaped fiber to act as a saturable absorber (SA). Due to the long light/graphene interaction length and the asymmetric structure, the SA used in this work has large polarization-dependent loss, and as a result, the stationary polarization-locked vector solitons can be generated, being different from the scalar solitons produced by the nonlinear polarization rotation technique. The formation mechanism of such solitons is studied and it is found that they are elliptically polarized solitons.

Theoretical modeling and analysis of a passively Q-switched Er-doped fiber laser with Tm-doped fiber saturable absorber

A theoretical model concerning the 3H6→3F4 transition of Tm ions for passive Q-switching of an Er-doped fiber laser is built. Related population transitions of the passive Q-switching mechanism are simulated and described. Effects of pump power, output reflectivity and cavity length on the laser performance are investigated and analyzed. Numerical results indicate that pump power and output reflectivity are major factors affecting the laser output, while the cavity length mainly determines the pulse duration. Besides, high repetition rate operation is achievable with 3H6→3F4 transition of Tm ions at the expense of the output pulse energy.

-switching of a thulium-doped fibre laser using a holmium-doped fibre saturable absorber

We have proposed and demonstrated a new passively -switched thulium-doped fibre laser configuration. A distinctive feature of this configuration is the use of a heavily holmium-doped fibre for -switching. Lasing was obtained at , with a pulse energy of and pulse duration of . The highest pulse repetition rate was .

Tm–Ho co-doped fiber-based high repetition rate passive Q-switching of an Er-doped fiber laser

An all-fiber Q-switched Er-doped laser is built with a ring cavity. Stable Q-switching is demonstrated with a Tm–Ho co-doped fiber saturable absorber. The maximum repetition rate of the laser system reaches 42 kHz, which is much larger than that with Tm singly doped fiber saturable absorbers. Analysis shows that interaction between thulium and holmium ions is the main reason for this high repetition rate operation.

Analysis of transient response and instability in fiber ring resonators containing an erbium-doped fiber amplifier and quantum dot-doped fiber saturable absorber

In this paper, the transient response of a double coupler fiber ring resonator containing an erbium-doped fiber amplifier (EDFA) in half part of the fiber ring resonator and a quantum dot-doped fiber (QDF) saturable absorber in the other half, is investigated. It is demonstrated that, depending on the device parameters and the input power of the signal and pump, various types of dynamic behaviors (such as bistability, monostability, and regenerative pulsation) can be observed in this intrinsic, optical bistable device. The proposed device can be exploited by optical communication networks to realize all-optical functionalities.

Experimental demonstration of an Er-doped fiber ring laser mode-locked with a Tm–Ho co-doped fiber saturable absorber

Mode-locking operation of an Er-doped fiber laser with a Tm–Ho co-doped fiber saturable absorber is demonstrated for the first time. Q-switching, Q-switched mode-locking and CW mode-locking operation modes are observed sequentially with increase of the pump power. In the mode-locking operation mode, a repetition rate at the fundamental cavity frequency of 9.05 MHz is obtained with a pulse duration of 46.3 ns. By rotating the polarization controller, a repetition rate up to 887 MHz is achieved, and the pulse duration is shortened to 0.548 ns.

A stable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser with superimposed FBG and an in-line two-taper MZI filter

A simple approach to fabricate a stable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser with one superimposed fiber Bragg grating (FBG) is proposed and demonstrated. The superimposed FBG is fabricated by the dual-exposure method for wavelength selection. A home-made in-line two-taper Mach–Zehnder interferometer is incorporated to balance the intra-cavity loss for the wavelengths. The SLM operation is guaranteed by a feedback fiber loop and saturable absorber. A stable dual-wavelength SLM fiber ring laser with a wavelength spacing of approximately 8.53 nm is experimentally realized. The optical signal-to-noise ratio of the laser output is over 50 dB and the linewidth of each wavelength measured by the delayed self-heterodyne method is 9.67 kHz and 9.07 kHz, respectively. The proposed scheme offers the possibility for difference frequency generation of terahertz radiation.

Optical bistability in fiber ring resonator containing an erbium doped fiber amplifier and quantum dot doped fiber saturable absorber

In this paper we study the optical bistability in a double coupler fiber ring resonator which consists of an erbium doped fiber amplifier (EDFA) in half part of the fiber ring and a quantum dot doped fiber (QDF) saturable absorber in the other half. The bistability is provided by the QDF section of the ring resonator. The EDFA is employed to reduce the switching power. The transmitted and reflected bistability characteristics are investigated. It is shown that the switching power for this new bistable device is less than 10 mW.

400 µJ 79 ns amplified pulses from a Q-switched fiber laser using an Yb^3+-doped fiber saturable absorber

We report a passively Q-switched all-fiber laser using a large mode area (LMA) Yb(3+)-doped fiber cladding-pumped at 915 nm and an unpumped single-mode Yb(3+)-doped fiber as the saturable absorber (SA). The saturable absorber fiber and gain fiber were coupled with a free-space telescope to optimize the coupling efficiency between the disparate fibers, preferentially bleaching the SA fiber before gain depletion in the pumped fiber. Using this scheme we first demonstrate a Q-switched oscillator with 40 μJ 79 ns pulses at 1026 nm, and show that pulses can be generated from 1020 nm to 1040 nm. The associated peak power of the oscillator alone is more than two orders of magnitude larger than that reported in previous experimental studies using an Yb(3+)-doped fiber as a saturable absorber. We further demonstrate an amplified pulse energy of 0.4 mJ using an Yb(3+)-doped cladding pumped fiber amplifier. Experimental studies in which the saturable absorber length, pump times, and wavelengths are independently varied reveal the impact of these parameters on laser performance.

Passively Q-switched ytterbium- and chromium-doped all-fiber laser

A chromium-doped saturable absorber fiber stabilizes an otherwise spontaneously chaotically self-pulsing ytterbium-doped fiber laser. This original passively Q-switched all-fiber laser produces sustained and relatively stable trains of smooth pulses at a high repetition rate.

Stable mode-locked fiber laser using 49 cm long bismuth oxide based erbium doped fiber and slow saturable absorber

A stable mode-locked fiber laser employing a 49 cm long bismuth oxide based erbium doped fiber (Bi-EDF) by using a slow saturable absorber is demonstrated. Near transform limited short pulses with a repetition rate of 8.27 MHz are obtained at a wavelength of 1560 nm with a maximum spectral width of 15 nm. Results indicate that pulse characteristics are strongly dependent on pump power rather than spectral width. Moreover the Time-Bandwidth products (TBWP), pulse duration, the energy fluctuation and timing jitter decrease with increasing pump power. The pulse width is continuously varied from 1.2 ps to less than 300 fs. It produces stable mode locking with a maximum spectral width of 15 nm, minimum timing jitter of 4 ps and energy fluctuations of 2.5%. The pulse train was amplified using a two-stage amplifier up to 447 mW average power corresponding to peak powers of 177.3 kW.

Stable and widely tunable wavelength-spacing single longitudinal mode dual-wavelength erbium-doped fiber laser

In this paper, a novel and simple widely tunable wavelength-spacing single longitudinal mode (SLM) dual-wavelength erbium-doped fiber laser (EDFL) based on the tunable filter group, a passive feedback fiber ring (FFR) and saturable absorber (SA), is proposed and demonstrated experimentally. Experiment results show that the wavelength spacing can tune from 0.8 nm up to 17 nm, which has potential to generate terahertz (THz) waves by photo-mixing the lasing wavelengths in a high-speed photo-detector, and the maximum fluctuation of peak power of EDFL is less than 0.37 dB within 75 min and the optical signal-to-noise ratio is more than 30 dB at room temperature. In the absence of high-speed photo-detector, THz beat-note is also successively observed with the help of an autocorrelator. Moreover, dual-wavelength fiber laser can selectively realize one wavelength lasing by simply tuning filters.

Numerical analysis of mode locking in multi-core photonic crystal fiber

With linearly coupled nonlinear Schrodinger equations, numerical analysis has been performed on the mode locking forming procedure of a fiber laser in the linear cavity configuration. The fiber is Yb-doped multi-core photonic crystal fiber and semiconductor saturable absorber mirror (SESAM) is adopted as the nonlinear transmission element to start mode locking. Because of the noise randomness, initial pulse would be picked out by SESAM in one or more cores which makes the multi-core mode locking quite different from single-core one. The two situations are compared and fully discussed. Mode locking in multi-core photonic crystal fiber laser can be realized only if the couple coefficient between the cores and the temporal overlap between the pulses in different cores are large enough.

Stable single-longitudinal-mode fiber laser using PM FBG F-P etalon and PM fiber saturable absorber

we present a stable and high efficiency single-longitudinal-mode (SLM) fiber ring laser by using polarization-maintaining fiber Bragg grating Fabry-Perot (PM FBG F-P) etalon combining PM fiber saturable absorber. The PM FBG F-P etalon, which is directly fabricated in hydrogen-loaded PM fiber, is used as reflector and mode-selecting component to reduce the longitudinal-mode density greatly. Meanwhile, a segment un-pumped PM Er3+-doped fiber (EDF) serves as saturable absorber to suppress mode hopping and ensure the stable SLM operation. Stable SLM laser output at 1550.4 nm with linewidth of 2.0 kHz is observed. Laser output power is 43.7 mW for a pump power of 148 mW, optical-optical efficiency is 29.5% and signal-to-noise ratio (SNR) is larger than 55 dB.

A saturable absorber Q-switched all-fiber ring laser

We propose a simple design of a saturable absorber Q-switched all-fiber ring laser. By locating a saturable absorber fiber in the intensity-enhanced section of a ring resonator, the laser is passively Q-switched. A set of location-dependent rate equations is established for Q-switching modeling. The design has been numerically and experimentally demonstrated using Er(3+)-doped fiber at the emission wavelength of 1550 nm. A single-mode Q-switched pulse with pulse energy of 0.37 microJ and pulse duration of 218 ns was achieved with 980-nm pump power near 7 mW.