On-Chip Optical Stabilization of High-Speed Mode-locked Quantum Dot Lasers for Next Generation Optical Networks

Monolithic passively mode-locked colliding pulse semiconductor lasers generating pico- to sub-picosecond terahertz optical pulse trains are promising sources for future applications in ultra-high speed data transmission systems and optical measurements. However, in the absence of external synchronization, these passively mode-locked lasers suffer from large amplitude and timing jitter instabilities resulting in broad comb linewidths, which precludes many applications in the field of coherent communications and signal processing where a much narrower frequency line set is needed. In this dissertation, a novel quantum dot based coupled cavity laser is presented, where for the first time, four-wave mixing (FWM) in the monolithically integrated saturable absorber is used to injection lock a monolithic colliding pulse mode-locked (CPM) laser with a mode-locked high-Q ring laser. Starting with a passively mode-locked master ring laser, a stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3-times reduction in the average optical linewidth of the injection locked CPM slave laser. The FWM process is subsequently verified experimentally and conclusively shown to be the primary mechanism responsible for the observed injection locking. Other linear scattering effects are found to be negligible, as predicted in the orthogonal waveguide configuration. The novel injection locking technique is further exploited by employing optical hybrid mode-locking and increasing the Q of the master ring cavity, to realize an improved stabilization architecture. Dramatic reduction is shown with more than 14-times reduction in the photodetected beat linewidth and almost 5-times reduction in the optical linewidth of the injection locked slave laser with generation of close to transform limited pulses at ~ 30 GHz. These results demonstrate the effectiveness of the novel injection locking technique for an all-on-chip stability transfer and provides a new way of stabilizing monolithic optical pulse sources for applications in future high speed optical networks

A Novel Intensity Modulator For Photonic Adcs Using An Injection-Locked Mode-Locked Laser

A novel intensity modulator for pulsed light is proposed and demonstrated here for the first time. This has been realized by introducing an injection-locked AlGaInAs mode-locked laser into one arm of a Mach-Zehnder interferometer. © 2014 OSA

A Novel Intensity Modulator For Photonic Adcs Using An Injection-Locked Mode-Locked Laser

A novel intensity modulator for pulsed light is proposed and demonstrated here for the first time. This has been realized by introducing an injection-locked AlGaInAs mode-locked laser into one arm of a Mach-Zehnder interferometer

Direct Rf Synchronization Of A 22 Ghz Monolithic Alingaas Quantum Well Laser With Sub-Picosecond Pulse Generation

A 22 GHz AlInGaAs two-section mode-locked laser is presented here. 860 fs optical pulses with timing jitter of 280 fs (1 Hz-100 MHz) are generated by direct RF modulation of the saturable absorber. © 2012 IEEE

A Linearized Intensity Modulator For Photonic Analog-To-Digital Conversion Using An Injection-Locked Mode-Locked Laser

A linearized intensity modulator for pulsed light based on an injection-locked mode-locked laser (MLL) is presented here. This has been realized by introducing a monolithic Fabry-Pérot MLL into one of the arms of a conventional Mach-Zehnder interferometer (MZI) and injection-locking it to a MLL which is the input to the interferometer. By modulating the current on the gain section or the voltage of the saturable absorber (SA) section of the injection-locked laser, one can introduce an arcsine phase response on each of the injected longitudinal modes. By combining the modulated optical comb with its unmodulated counterpart one can produce a linearized intensity modulator. The linearity of this modulator is inherent in its design and no pre- or postdistortion linearization scheme is utilized. The results of the two-tone intermodulation experiment are presented here for this modulator and a spur-free dynamic range (SFDR) of ∼70 dB·Hz2/3is achieved by modulating the voltage of the SA. The reported SFDR is limited by the noise of the MLLs. The dynamic range could be further improved by decoupling the phase modulation and amplitude modulation. The proposed and demonstrated configuration as an analog optical link with improved linearity has the potential to increase the performance and resolution of photonic analog-to-digital converters (ADCs)

Semiconductor-Based Linear Intensity Modulator With Spur Free Dynamic Range Of 105 Db.Hz\u3csup\u3e2/3\u3c/sup\u3e

A 105 dB.Hz2/3 spur free dynamic range (SFDR) is achieved from a semiconductorbased intensity modulator. This has been realized by introducing an injection-locked passively mode-locked laser into one of the arms of a Mach-Zehnder interferometer

A True Linear Intensity Modulator For Pulsed Light

A linear interferometric intensity modulator for pulsed light is demonstrated using an injection-locked mode-locked laser (MLL). A spur free dynamic range (SFDR) of 105 dB.Hz2/3 is obtained by modulating the voltage of the saturable absorber

High-Q Transfer In Nonlinearly Coupled Mode-Locked Semiconductor Lasers

A novel four-wave mixing-based injection locking method was demonstrated earlier, whereby the optical and RF stability of a mode-locked high-Q ring laser is successfully transferred to an orthogonally coupled colliding pulse mode-locked (CPM) laser. Four-wave mixing in the common monolithically integrated saturable absorber is used to couple the crossed laser cavities, which is confirmed by the reduction in RF noise level and by the optical linewidth reduction of the lasing modes of the slave CPM laser. The four-wave mixing process was then further investigated and experimentally shown to be the primary mechanism responsible for the locking and stabilization of the slave laser. This paper discusses the above four-wave mixing technique in detail and presents an improved design by employing optical subharmonic hybrid mode-locking and by decreasing the losses inside the master ring cavity. The resulting higher stability of the master laser translates into further improvement in the RF and optical linewidths of the injection locked slave CPM laser. These results demonstrate the effectiveness of the novel method for all on-chip stability transfer in the forthcoming all monolithic optical pulse source systems

All Optical Stabilization Of A Monolithic Quantum Dot Based Cpm Laser Via Four-Wave Mixing

We investigate and confirm a four-wave mixing (FWM) process as the primary mechanism responsible for locking and stabilization of a previously reported novel quantum dot based monolithically coupled colliding pulse mode-locked (CPM) laser. In the previous letter, a high-Q passively mode-locked ring laser is used to injection lock an orthogonally coupled passively mode-locked CPM slave laser via FWM in the common saturable absorber. In this letter, we setup an experiment to verify the FWM process, whereby the external ring laser is operated unidirectionally while simultaneously analyzing the amplified spontaneous emission from the other facet of the ring laser. The emission is found to contain CPM light only in the presence of injection locking proving the FWM process. Other linear scattering effects are also investigated and shown to be negligible in the orthogonal waveguide configuration. © 1989-2012 IEEE

Four-Wave Mixing Mediated Stabilization Of An Orthogonally Coupled Monolithic Cpm Laser

We experimentally confirm four-wave mixing process as the dominant mechanism responsible for injection locking in case of a novel monolithically integrated orthogonally coupled colliding pulse mode-locked (CPM) laser. © 2013 The Optical Society