Mode-locked Semiconductor Fiber Ring Laser Research Articles

Tunable 12×10 GHz mode-locked semiconductor fiber laser incorporating a Mach-Zehnder interferometer filter

A stable multiwavelength mode-locked semiconductor fiber ring laser incorporating a fiber Mach-Zehnder interferometer (MZI) filter was proposed and experimentally demonstrated. A semiconductor optical amplifier (SOA) serves as an optically controlled mode-locking element due to gain exhaustion caused by external injected optical pulses. Another SOA severs as a constant-gain medium. A fiber MZI filter with a temperature control is incorporated into the fiber ring cavity to acquire a stable and tunable multiwavelength oscillation. Twelve wavelengths are synchronously mode-locked at 10 GHz, pulse width of mode-locked pulse are about 30 ps. Proposed multiwavelength mode-locked semiconductor fiber ring laser has some distinct advantages, such as simple and compact structure, easy integration, convenient tuning, good stability, potential high repetition rate operating, which has potential application in the future WDM communication system.

Optical clock division based on dual-wavelength mode-locked semiconductor fiber ring laser

We have reported the optical clock division utilizing an injected mode-locked fiber ring laser incorporating semiconductor optical amplifiers (SOAs) and a dispersion compensation fiber (DCF). The clock division is mainly caused by the modulation competition between two wavelength components while both of them satisfy the harmonic mode-locking condition at the newly generated frequency. Stable second, third, and fourth clock divisions are obtained by properly adjusting the polarization controllers inside the ring cavity when a 10-GHz clock signal without any sub-harmonic frequency component is injected into the cavity. The radio-frequency spectra show good qualities of the obtained clock division trains.

Investigation of noise suppression, pulse intensity and chirp of an actively mode-locked semiconductor fiber ring laser

An actively mode-locked fiber ring laser that utilizes an EDFA and semiconductor optical amplifier (SOA) is presented. The SOA enhances noise suppression. Active mode-locking was demonstrated at repetition rates up to 20 GHz. The effects of intra-cavity power and SOA current on noise suppression are studied for two types of commercially available SOA. The frequency resolved optical gating technique is used to characterize the output pulse stream intensity and frequency chirp.

Optical pulse shaping by cross-phase modulation in a harmonic mode-locked semiconductor fiber ring laser under large cavity detuning

The authors experimentally investigate the phenomena of the pulse-shape distortion due to the drift of cavity length or modulation frequency in a harmonically mode-locked semiconductor fiber ring laser (SFRL). Also, it is experimentally demonstrated that the optical pulse shaping by cross-phase modulation (XPM) can be applied to enhance the robustness of a harmonic mode-locked semiconductor ring laser to the environmental factors, e.g., the modulation-frequency drift and/or the cavity-length drift. The mechanism of pulse-shape distortion due to the modulation-frequency drift or cavity-length drift is explained and experimentally verified. As the locking condition of the SFRL goes to the rational harmonic mode-locking (RHML) regime, the pulse-shape distortion becomes dominant. To validate the explanation, a simple equation for estimating and comparing the amount of cavity-length detuning in terms of frequency is proposed for comparison, which is called the equivalent frequency detuning (EFD). The distortion mostly appeared in the trailing edge of the pulse. By selectively filtering the XPM-induced red-chirped wavelength components in the rising edge of the pulse, the mode-locked pulse train with large pulse-shape distortion can be reshaped to regenerate a mode-locked pulse train with less pulse-shape distortion than the pulse train without the proposed scheme. This method can be used to reduce the pulse-shape distortion effectively, maintaining the pulse repetition rate under the large modulation-frequency detuning, or equivalently, large cavity-length detuning. The proposed scheme is able to generate the pulse-trains robust to the modulation-frequency drift and/or cavity-length drift of the mode-locked SFRL.

A self-consistent model for a SOA-based fiber ring laser including the mode-locked pulse properties

In this paper, we present a self-consistent model of an optically mode-locked semiconductor fiber ring laser. The fiber laser uses a semiconductor optical amplifier (SOA) as the gain medium, while mode-locking is achieved by its gain modulation, via an external optical pulsed signal. We solved the model analytically developing a novel technique, where we have assumed double saturation of the SOA by both the mode-locked and the externally introduced pulsed signal. The study revealed the locus of the laser parameters to achieve mode-locking. In particular, it was found that SOA gain and energy of the externally introduced signal are two critical parameters that must simultaneously set properly for exact mode-locking. Another outcome of our analysis is that the study of the chirp parameter should be carried out keeping the nonlinear terms of the SOA gain. We have also investigated a slightly detuning regime of operation that revealed a fast change of the mode-locking process.

Generation of 40‐GHz pulse trains from a 5‐GHz dual‐driving rational harmonic mode‐locked semiconductor fiber‐ring laser

AbstractWe present and demonstrate a simple method of generating 40‐GHz repetition‐rate pulse trains from a rational harmonic mode‐locked semiconductor fiber‐ring laser with 5‐GHz dual‐driving signal by using pulse‐amplitude equalization. By adjusting the voltages applied to both arms of the modulator pulse trains with an eight‐times repetition rate are equalized in their amplitudes. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 489–491, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20511

Relaxation-free harmonically mode-locked semiconductor-fiber ring laser

A 10-Gb/s semiconductor-fiber ring laser is proposed and demonstrated. The performance of a harmonically mode-locked semiconductor-fiber ring laser was described in detail. A long cavity length configuration in semiconductor optical amplifier is found to eliminate the relaxation oscillation, and improved short-term amplitude stability. The laser output has a pulsewidth of 18.4 ps and a spectral width of 0.3 nm.