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External cavity semiconductor mode-locked lasers can produce pulses of a few picoseconds. The pulses from these lasers are inherently chirped with a predominant linear chirp component that can be compensated resulting in sub-picosecond pulses. External cavity semiconductor mode-locked lasers can be configured as multiwavelength pulse sources and are good candidates for time and wavelength division multiplexing applications. The gain medium in external cavity semiconductor mode-locked lasers is a semiconductor optical amplifier (SOA), and passive and hybrid mode-locked operation are achieved by the introduction of a saturable absorber (SA) in the laser cavity. Pump-probe techniques were used to measure the intracavity absorption dynamics of a SA in an external cavity semiconductor mode-locked laser and the gain dynamics of a SOA for the amplification of diverse pulses. The SOA gain dynamics measurements include the amplification of 750 fs pulses, 6.5 ps pulses, multiwavelength pulses and the intracavity gain dynamics of an external cavity multiwavelength semiconductor mode-locked laser. The experimental results show how the inherent chirp on pulses from external cavity semiconductor mode-locked lasers results in a slow gain depletion without significant fast gain dynamics. In the multiwavelength operation regime of these lasers, the chirp broadens the temporal pulse profile and decreases the temporal beating resulting from the phase correlation among wavelength channels. This results in a slow gain depletion mitigating nonlinearities and gain competition among wavelength channels in the SOA supporting the multiwavelength operation of the laser. Numerical simulations support the experimental results.
Covering high-energy ultrafast amplifiers and solid-state, fiber, and diode lasers, this reference examines recent developments in high-speed laser technology. It presents a comprehensive survey of ultrafast laser technology, its applications, and future trends in various scientific and industrial areas. Topics include: micromachining applications for metals, dielectrics, and biological tissue; advanced electronics and semiconductor processing; optical coherence tomography; multiphoton microscopy; optical sampling and scanning; THz generation and imaging; optical communication systems; absolute phase control of optical signals; and more.
Using a delay differential equation model with two time delays, we investigate the dynamics of a semiconductor laser with an active cavity coupled to an external passive cavity. Our numerical simulations indicate that when the coupling between the two cavities is strong enough and the round-trip time of the active cavity is an integer multiple of the round-trip time of the external passive cavity, a harmonic mode-locking regime can develop in the laser with the pulse repetition period close to the passive cavity round trip time. We also demonstrate that the output field intensity sensitively depends on the relative phase between the electric fields in the two cavities giving rise to a resonant behavior. The period and width of the resonances depend on the ratio of the round-trip times and the coupling between the two cavities. We show that the coupled cavity system under consideration can demonstrate a bistability between different regimes of generation.
Coherent sources emitting two optical frequencies with a widely tunable frequency difference lying in the radio-frequency range and having a high degree of correlation between their fluctuations can be useful for numerous applications such as microwave photonics, ultra-stable atomic clocks, atom manipulation and probing, metrology, etc. Dual-frequency lasers, which emit two orthogonal linearly polarized modes with a frequency difference lying in the radio-frequency range, have huge potentials for the above mentioned applications. We compare the characteristics of such dual-frequency oscillation in lasers based on either semiconductor (VECSEL: vertical-external-cavity surface-emitting laser) or solid-state active media (mainly Nd3+, or Er3+ doped crystalline host). Apart from the obvious difference between the gain mechanisms in semiconductor and solid-state laser media, the dual-frequency VECSEL and the dual-frequency Nd:YAG laser exhibit different dynamical behaviors. The dual-frequency VECSELs exhibit relaxation oscillation free class-A dynamics as the photon lifetime inside the cavity is longer than the population inversion lifetime. On the contrary, the dual-frequency Nd:YAG lasers obey class-B dynamics linked with the fact that the photon lifetime inside the cavity is shorter than the population inversion lifetime, leading to the existence of relaxation oscillations. In this thesis, we figure out how the laser dynamics, in addition to the nonlinear coupling between the two laser modes, governs different noise phenomena in dual-frequency lasers. In particular, we demonstrate, both experimentally and theoretically, the influence of the laser dynamics and the nonlinear coupling between the two modes on the laser noise, by analyzing the spectral properties of the different noises (intensity, phase) and their correlation in a class-A dual-frequency VECSEL (vertical-external-cavity surface emitting laser) and a class-B dual-frequency Nd:YAG laser. Moreover, the noise correlation results are interpreted in terms of the linear response of two coupled damped oscillators.
Ultrashort pulses in mode-locked lasers are receiving focused attention from researchers looking to apply them in a variety of fields, from optical clock technology to measurements of the fundamental constants of nature and ultrahigh-speed optical communications. Ultrashort pulses are especially important for the next generation of ultrahigh-speed optical systems and networks operating at 100 Gbps per carrier. Ultra Fast Fiber Lasers: Principles and Applications with MATLAB® Models is a self-contained reference for engineers and others in the fields of applied photonics and optical communications. Covering both fundamentals and advanced research, this book includes both theoretical and experimental results. MATLAB files are included to provide a basic grounding in the simulation of the generation of short pulses and the propagation or circulation around nonlinear fiber rings. With its unique and extensive content, this volume— Covers fundamental principles involved in the generation of ultrashort pulses employing fiber ring lasers, particularly those that incorporate active optical modulators of amplitude or phase types Presents experimental techniques for the generation, detection, and characterization of ultrashort pulse sequences derived from several current schemes Describes the multiplication of ultrashort pulse sequences using the Talbot diffraction effects in the time domain via the use of highly dispersive media Discusses developments of multiple short pulses in the form of solitons binding together by phase states Elucidates the generation of short pulse sequences and multiple wavelength channels from a single fiber laser The most practical short pulse sources are always found in the form of guided wave photonic structures. This minimizes problems with alignment and eases coupling into fiber transmission systems. In meeting these requirements, fiber ring lasers operating in active mode serve well as suitable ultrashort pulse sources. It is only a matter of time before scientists building on this research develop the practical and easy-to-use applications that will make ultrahigh-speed optical systems universally available.