Ultrafast Semiconductor-Based Fiber Laser Sources

Abstract

Abstract-In this paper, a novel ring laser platform is presented that uses a single active element, a semiconductor optical amplifier (SOA), to provide both gain and gain modulation in the optical cavity. Gain modulation is achieved by an externally introduced optical pulsed signal. This signal periodically saturates the amplifier gain and forces the ring laser to mode lock. Using this laser platform, we demonstrate picosecond pulsetrain generation at repetition rates up to 40 GHz, either in single or multiwavelength operation mode. In particular, using rational harmonic mode locking, 2.5-ps pulses were obtained up to a 40-GHz repetition rate, while output pulses and output power were constant over a 20-nm tuning range. In addition, a multiwavelength optical signal was obtained using the same laser platform with the addition of a Fabry-Pérot filter for comb generation. Multiwavelength oscillation is possible due to the broad gain spectrum of the SOA used and its inhomogeneous line broadening. To this end, 48 oscillating wavelengths were obtained at the laser output, with 50-GHz line spacing. Combining both modes of operation, it was possible to mode lock the oscillating multiwavelength signal and to obtain at the output ten wavelength channels, simultaneously mode locked at a 30-GHz repetition rate. The mode-locked channels are temporarily synchronized and exhibit almost identical spectral and time characteristics.

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

“…When increasing the gain level in the laser cavity, such as increasing the injection current of a SOA up to 200 mA, the optical-pulse trains with twice or triple of external-injection optical-pulse frequency are observed with 10 GHz external-injection pulse sequence. This characteristic could be used to develop high-repetition-rate pulses [24]. However, the obtained optical-pulse trains show an obvious amplitude variation, which is caused by the different positions of the phase shifted pulses [25].…”

Triple-wavelength fiber ring laser based on a hybrid gain medium actively mode-locked at 10 GHz

“…By using a polarization independent filter, such as a Fabry-Perot filter [1], to force multiwavelength operation of the laser one could expect a significant reduction in the polarization sensitivity of the MWFRL cavity. The MZM may also be replaced with a polarization insensitive modulator such as an electroabsorption modulator (EAM) or removed entirely with the SOA being used as a modulator.…”

“…By actively mode-locking the MWFRL cavity a high repetition rate multiwavelength short optical pulse source may be realized [1]. This multiwavelength pulse source can be combined with time division multiplexing (TDM) techniques to increase the transmission capacity of optical fiber thereby highlighting applications in high speed optical communications systems.…”

Repetition rate and wavelength-tunable all-optical actively mode-locked fibre ring laser based on a reflective semi-conductor optical amplifier

“…Harmonic mode-locking of a fiber ring laser is an attractive method of producing a high repetition rate, wavelength tunable picosecond optical pulse source [1]. Such sources are of paramount importance in high speed optical communications systems.…”

“…Such modulators are characterized by high insertion loss and in the case of the MZM exhibit a high degree of polarization sensitivity. The use of a semiconductor optical amplifier (SOA) as both the gain medium and mode-locking element in a HMLFRL has been investigated previously [1,4,5]. An external optical pulse source is injected into the laser cavity and serves to periodically modulate the SOA carrier density via cross gain modulation (XGM).…”