Single-longitudinal-mode fiber ring lasers with a saturation-level-controlled saturable absorber

An Erbium Fiber Laser With Single-Frequency Oscillation and Wavelength-Upconverted Output

“…The SLM operation of the proposed EDF laser is produced by applying the 5.5 m unpumped EDF based SA. The EDF SA would create standing wave effect to suppress the dense MLM [8]. When we use the FBG2 and remove the EDF SA in the proposed fiber laser scheme, the observed side-mode could not be suppressed over the bandwidth of 0 to 1 GHz, as illustrated in Fig.…”

“…Furthermore, the homogeneous broadening gain medium of EDF and longer fiber loop in the fiber laser would bring the unstable multi-longitudinal-mode (MLM) and mode-hopping output [6,7]. Hence, in order to attain the single-longitudinal-mode (SLM) oscillation in the EDF based lasers, a number of techniques have been proposed and demonstrated, such as exploiting a unpumped EDF or graphene based saturable absorbers (SAs) [8,9], using the multiple-ring architectures [10,11], employing optical-injection loop design [12,13], applying Mach-Zehnder interferometer (MZI) structure [14,15], and utilizing the Rayleigh backscattering (RB) method [16,17]. To accomplish the wavelength tunability in EDF lasers, different optical filters have been utilized inside the fiber cavity for selecting, such as the optical tunable bandpass filter (OTBPF), ultra-narrow filter, Fabry-Perot tunable filter (FP-TF), Silicon-micro-ring resonator (SMRR) and fiber Bragg grating (FBG) [18][19][20].…”

Stable Single-Longitudinal-Mode Fiber Laser With Ultra-Narrow Linewidth Based on Convex-Shaped Fiber Ring and Sagnac Loop

“…1. The selfwritten dynamic Bragg grating (DBG) can be established in the EDF2 by the standing-wave saturation effect [8], [12]. As the FWHM of the DBG is very small and the center frequency of DBG tracks the lasing mode [20], the unpumped EDF2 can serve as the ultra-narrowband auto-tracking filter.…”

“…The associate editor coordinating the review of this manuscript and approving it for publication was Zinan Wang . stable SLM behavior is difficult to achieve mainly due to the long lasing cavity and the unstable multi-longitudinal-mode (MLM) oscillation caused by the homogenous broadening of the EDF. To obtain a stable SLM EDF ring fiber laser with superior performance, many approaches have been applied in the laser cavity, such as using the expensive ultra-narrow passband optical filter [9], employing the complicated optical injection method [10], applying the Mach-Zehnder interferometer (MZI) structure [11], utilizing unpumped EDF-based saturable absorber (SA) [12], applying Rayleigh backscattering in tapered fiber [13], employing phase-shifted FBG filter [8], using FBG Fabry-Pérot filter [14] and designing the compound-ring structure [15]- [17].…”

A Selectable Single-Mode Erbium Fiber Laser With Mach-Zehnder Interferometer and Rayleigh Injection Scheme

“…However, the EDF ring lasers with stable single-longitudinal-mode (SLM) operation will be hard to accomplish principally because of the long fiber cavity and the dense multi-longitudinal-mode (MLM) oscillation induced by the homogenous broadening effect of EDF [6], [7]. To ensure and reach the SLM action in the EDF ring fiber laser with advantageous output performance, numerous methods have been operated in the fiber ring cavity, such as using the Mach-Zehnder interferometer (MZI) scheme [8], saturable absorber (SA) based filter [9], [10], Rayleigh backscattering (RB) injection [11], compound fiber ring configuration [12], [13], and narrower optical filter [14], [15]. Chien-Hung Yeh, Li-Hung Liu, Han-Shin Ko, and Yi-Ting Lai are with the Department of Photonics, Feng Chia University, Taichung 407802, Taiwan (e-mail: yeh1974@gmail.com; jk1992581@gmail.com; xzbc699@gmail.com; laietn@gmail.com).…”