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We analyse the spectral properties of an optical frequency comb emitted by a III-V-on-silicon ring laser operated in the hybrid mode-locking regime. We demonstrate that the mode-locked laser has disparate responses to an external RF modulation depending on the saturable absorber bias and pump current. Firstly, we show that, when the mode-locking is fully achieved, the hybrid operation maintains the full mode-locking characteristics across the whole locking region. Secondly, starting from an incomplete passive mode-locking regime, and using the modulation frequency as a control parameter, we demonstrate the gradual improvement of the mode-locking characteristics within the locking tongue. This effect is maximized at the RF locking tongue boundary and manifests in an increase of the spectral width and a diminution of the modal linewidth dispersion. [ABSTRACT FROM AUTHOR]

An all-fiber frequency shifted feedback laser is developed to export mode-locked pulses with a narrow spectral bandwidth (238 MHz). A simple cavity structure is established by employing a fiber Bragg grating-based acousto-optic frequency shifter. An exotic reflection peak in a large spectral separation from the Bragg reflection peak is generated by applying flexural acoustic waves, and is utilized for narrow-band filtering and frequency shifting in the laser cavity. Stable mode-locked pulse output can be obtained with the cavity length as short as 16.5 m, whereas increasing the cavity length can reduce the pump power to 37 mW for mode-locked pulse output. A maximum power conversion efficiency of 17% with an average output power of 103 mW were obtained experimentally at a pump power of 600 mW, with corresponding pulse width, pulse energy and peak power of 2 ns, 88 nJ and 4.5 W, respectively. A time-bandwidth product of mode locked pulses of 0.476 denotes nearly Fourier-transform-limited performance. This work provides a new technique to implement efficient, compact and low-cost all-fiber FSFLs for narrow spectral bandwidth mode-locked pulse output. [ABSTRACT FROM AUTHOR]

In this paper, we report a nanosecond mode locked erbium doped fiber laser (EDFL) using zinc oxide (ZnO) nanoparticles as a saturable absorber (SA) for the first time. Due to its excellent optical properties, in particular a high nonlinear optical response and fast recovery time, ZnO nanoparticles can be used as a saturable absorber device for pulsed laser generation. For easy integration into the laser cavity, the ZnO nanoparticles were imbedded into a polymer film using a seeding solution technique. 400 ns mode locked pulse train was successfully obtained at a relatively low threshold pump power of 45.4 mW. The output laser operates at the fundamental frequency of 1 MHz with a center wavelength of 1558.34 nm. The highest pulse energy and peak power achieved by the laser are estimated at 11.6 nJ and 27.3 mW respectively at the maximum available pump power of 142 mW. The results show that the SA derived from ZnO nanoparticles is capable of producing nanosecond mode locked EDFL for possible applications that require high pulse energy and medium output power. [ABSTRACT FROM AUTHOR]

The single cavity all-dielectric thin film Fabry-Perot filter (s-AFPF) has been theoretically investigated in this paper as a means of tuning the wavelength in an external cavity diode laser (ECDL), and the means of limiting longitudinal mode hopping has been also theoretically investigated. When a TE or TM plane wave irradiates an s-AFPF, a quasi-linear relationship is found in a certain wavelength range between the optical intensity peak transmittance wavelength of s-AFPF and the cosine value of plane wave incident angle at s-AFPF. Based on this feature, we proposed and theoretically investigated an ECDL configuration based on an s-AFPF. By theoretical calculation, the actuator flat edge against the steel ball may be replaced by a bent edge to convert the mode-hop wavelength region into mode-hop-free wavelength region. The ECDL can be used in the application of environmental monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on. [ABSTRACT FROM AUTHOR]

We have proposed a carbon-nanotube-based passively mode-locked fiber laser, which consists of two fiber ring resonators, for the first time to author's best knowledge. The proposed laser in the main cavity is coupled with a fiber sub-loop, which is connected with a 2 × 2 optical coupler. Without the sub-loop, uniform-spaced conventional solitons are achieved in the fiber ring laser. With the sub-loop, the fiber laser generates a train of pulses modulated with a periodic envelop. The modulation period and pulse-pulse separation are ∼160 and ∼4.3 ns, which are determined by the lengths of the main cavity and the sub-loop, respectively. [ABSTRACT FROM AUTHOR]

An all-fiber ytterbium-doped laser widely tunable in duration and repetition rate is reported, which is actively mode locked based on a high speed in-cavity intensity modulator. The laser can generate a stable pulse train with a duration adjustable from 31 to 910 ps, and a repetition rate ranging from 13.12 MHz to 6.2 GHz (from the basic to the 475th-order harmonic) without changing the cavity construction. The cavity supermode suppression ratio is as good as 45 dB, and the signal-to-noise ratio is better than 48 dB at the 475th-harmonic mode locking. To the best of our knowledge, it is the highest order (475th) harmonic mode locking achieved in an all-normal-dispersion ytterbium-doped fiber laser, with the widest tuning range of repetition rate and pulsewidth. [ABSTRACT FROM PUBLISHER]