The dependence of thickness and concentration product (TCP) of single-wall carbon nanotubes saturable absorber (SWCNTs SA) on stabilizing and shortening pulse width in passively mode-locked erbium-doped fiber ring laser (MLEDFL) was investigated and measured. The TCP represented the amounts of SWCNTs, which the optical beam encountered when passing through the SWCNTs SA. If the TCP was smaller than 8.25 (£gm x wt%), the spectral bandwidth was below 2 nm. The pulse shaping was dominated by its own self amplitude modulation (SAM) of SWCNTs SA. With further increasing TCP, the soliton-like ML operation was achieved and the spectral bandwidth was expanded to 6 nm. For soliton-like mode locking (ML) operation, the area theorem dominated the pulse shaping. Through area theorem analysis, the estimation of SPM increased as the TCP increased. The adequate enhanced SPM for balancing the slight negative GVD was provided to generate soliton-like ML pulses shorten the pulse width. However, as the TCP increased, the soliton pulse energy decreased. The decreasing soliton pulse energy restricted the further pulse shortening. The results showed that the dependence of the pulse energy and nonlinear self phase modulation (SPM) on TCP enabled to determine the shortest pulse width in MLEDFL based on the area theorem. At optimized TCP of 70.93 (£gm x wt%), it was found that the shortest pulse width of 418 fs. In addition, based on the estimated SPM from area theorem, the nonlinear refractive index n2 was calculated at the level of 0.4 - 1 x 10^-15 m^2/W that was close to the literature values of 10^-15 - 10^-16 m2/W. It provides another way to estimate the nonlinear refractive index except for the Z-scan measurement. We could also estimate the SPM if an active Z-scan measurement was taken to obtain the nonlinear refractive index of the sample. We realized the trend of pulse energy through few samples in MLEDFL, the behavior of pulse width could be theoretically simulated based on area theorem. Hence, with the area theorem analysis, the optimized TCP of SWCNTs SA could be simulated and estimated to generate the shortest pulse width from the trends of pulse energy and estimated SPM. The significant effect of TCP on pulse energy, SPM, pulse width, and spectral bandwidth of MLFLs suggests that the TCP represents the total amount of SWCNTs in SA, which can be used as one of key parameters for characterizing the passive MLFL pulse width. Through the study of the dependence of TCP on ML pulses in MLEDFL, it may provide a guideline to fabricate an effective SWCNTs SA to generate the shortest pulse width of the MLEDFL.

Coherent nonlinear effects such as Electromagnetically Induced Transparency (EIT), Coherent Population Trapping (CPT), and Slow light are studied in thermal Rb vapor by both continuous and pulsed laser fields. This work primarily includes three parts: (I) mode-locked rubidium laser and its applications (II) enhanced coupling between optical and sound waves in the forward direction via ultra-slow light (III) optical steering via ultra-slow light in rubidium vapor. In part(I), I describe the construction and study of a mode-locked rubidium laser operating at the Rb D1 line using an active mode-locking technique inside the laser cavity. The mode-locked laser field is used to observe coherent effects in a dense rubidium gas. In part(II), I experimentally demonstrate enhanced acoustic-optic coupling that occurs when the velocity of sound is close to the group velocity of light. Dragging of the light by effective motion of the gas in a Rb cell is the origin of enhanced coupling. Good agreement between theory and experiment is found. In part(III), I experimentally demonstrate optical beam deflection in coherently driven rubidium vapor due to the steep refraction index profile in the region of EIT.

Single-frequency and mode-locked silver film ion-exchanged glass waveguide lasers as well as all-optical clock recovery based on birefringent fiber resonators have been experimentally and theoretically studied. The theory, modeling and fabrication process of silver film ion-exchange techniques, have been discussed and presented.The UV-written gratings on both IOG-1 active and passive glass have been studied. For the first time, with a high quality narrowband grating UV-printed on the passive section of a hybrid glass, a DBR waveguide single-frequency laser is demonstrated with the linewidth less than 1 MHz and the output power of 9 mW.Novel saturable absorbers based on a fiber taper embedded in carbon nanotubes (CNTs)/polymer composite were demonstrated. The saturable absorbers were utilized to build mode-locked fiber lasers, which were studied experimentally. A mode-locked ring laser utilizing an Er-Yb-codoped glass waveguide as the gain medium was also demonstrated. In addition, short cavity mode-locked waveguide lasers with CNTs film on the top were theoretically investigated, which shows a short cavity mode-locked waveguide laser is very promising.A new concept to perform multi-channel multi-rate all-optical clock recovery based on birefringent fiber-optic waveguide resonators was discussed. The concept has been advanced to polarization-insensitive operation. The experimental results, obtained as a proof-of-concept, agree well with numerical simulations.

Yb-ion doped gain media have become the material of choice for reliable generation of ultrashort pulses at wavelength around 1 μm. At present, however, operation at high average power (>1 W) with sub-100 fs pulses still remains challenging. The efforts of developing an Yb-ion oscillator towards this goal, therefore, are the main focus of this thesis. In this work, the Yb:KGd(WO4)2 (Yb:KGW) crystals were chosen to serve as the gain media. To achieve high power operation, two fundamental issues have been carefully considered: 1) a new pumping scheme was proposed to alleviate the thermal issues in the Yb:KGW crystals; 2) a new method was introduced to characterize intracavity losses in the broadband Yb-ion oscillators. As a side effect observed during the optimization of the CW operation, simultaneous two-wavelength emission was also discussed. With the knowledge and experimental understanding of the fundamental issues in laser oscillators operated in the continuous-wave regime, the next step of this work demonstrated their operation in a pulsed regime. The dual action of the Kerr-lens and saturable absorber (KLAS) mode locking was proposed in this work and resulted in greatly enhanced laser performance. The laser delivered pulses with 67 fs duration at a repetition rate of 77 MHz. The average output power reached 3 W, which, to the best of our knowledge, is the highest average output power produced to date from the Yb-ion based bulk lasers with such a short pulse duration. The scalability of pulse energy and peak power was also demonstrated by reducing the repetition rate to either 36 MHz or 18 MHz. The cavity with the latter repetition rate produced 85 fs pulses with the pulse energy up to 83 nJ, which corresponds to a peak power as high as 1 MW. As required by many biomedical applications, the wavelength of the generated pulses (~1 μm) can be tuned in the near-infrared region by coupling them into an optical parametric oscillator (OPO). The feasibility of this approach was demonstrated in the last part of this thesis, through a thorough theoretical analysis of two OPO materials suitable for excitation at 1.04 μm.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 86-94). Also available in electronic format on the Internet.

Vertical external-cavity surface-emitting lasers are ideal testbeds for studying the influence of the non-equilibrium many-body dynamics on mode locking. As we will show in this thesis, ultra short pulse generation involves a marked departure from Fermi carrier distributions assumed in prior theoretical studies. A quantitative model of the mode locking dynamics is presented, where the semiconductor Bloch equations with Maxwell’s equation are coupled, in order to study the influences of quantum well carrier scattering on mode locking dynamics. This is the first work where the full model is solved without adiabatically eliminating the microscopic polarizations. In many instances we find that higher order correlation contributions (e.g. polarization dephasing, carrier scattering, and screening) can be represented by rate models, with the effective rates extracted at the level of second Born-Markov approximations. In other circumstances, such as continuous wave multi-wavelength lasing, we are forced to fully include these higher correlation terms. In this thesis we identify the key contributors that control mode locking dynamics, the stability of single pulse mode-locking, and the influence of higher order correlation in sustaining multi-wavelength continuous wave operation.

Le développement technologique dans le domaine des télécommunications, ainsi que des systèmes de détection, a accru ces dernières années la nécessité de signaux de référence présentant une très haute pureté spectrale. L'augmentation des débits, la saturation des bandes de fréquence ainsi que les performances imposées pour la détection radar ont ouvert la voie à la génération micro-onde par l'optique. Ces références de fréquence sont souvent issues d'oscillateurs optoélectroniques (OEO). Ces oscillateurs intègrent un élément de stockage de l'énergie au travers de résonateurs ou de longues lignes à retard fibrées afin d'augmenter leur facteur qualité et permettant ainsi d'atteindre des performances supérieures aux signaux multipliés à partir de sources basses fréquences ou directement à partir d'oscillateurs micro-ondes à résonateur diélectrique (DRO). Une topologie originale d'oscillateurs optoélectroniques a été proposée à la fin des années 1990 par une équipe américaine : il s'agit de remplacer le résonateur passif nécessitant un verrouillage du laser sur ce dernier par un résonateur actif, intégrant un amplificateur optique. Ce résonateur actif, un laser à blocage de modes, permet un couplage entre l'oscillation optique du laser et l'oscillation optoélectronique. On parle alors d'oscillateur optoélectronique couplé (COEO). Les performances du COEO sont étroitement liées à la pureté spectrale du signal issu du laser à blocage de modes. Ce travail de thèse traite de l'étude et de l'optimisation de ces systèmes. Une étude approfondie sur le bruit dans les amplificateurs optiques a tout d'abord été menée afin de déterminer quel type d'amplificateur choisir pour le COEO et sous quelles conditions l'amplification optique apporte un bruit de phase minimal. Ensuite, un COEO à 10 GHz a été réalisé, présentant un très faible bruit de phase atteignant - 132 dBc/Hz à 10 kHz de la porteuse. Un modèle a par ailleurs été implémenté, permettant de déterminer a posteriori l'efficacité du couplage et ainsi la bande de verrouillage entre l'oscillation optoélectronique et le laser à blocage de modes. Ce couplage interne dépend fortement de la dynamique du système. Cependant, les différents effets non linéaires qui ont lieu dans l'amplificateur à semiconducteur et les fibres ne permettent pas d'obtenir un modèle analytique. Un modèle itératif a alors été proposé afin d'obtenir les propriétés de l'enveloppe complexe lentement variable du peigne de fréquence généré en sortie du laser dont la photodétection conduit à la puissance RF générée par le COEO. Le COEO génère un peigne de fréquence suffisamment large pour produire des harmoniques RF supérieurs à la fréquence de répétition du laser à blocage de modes, si les modes longitudinaux espacés de plusieurs intervalles spectraux libres (ISL) sont en phase. Le modèle itératif développé permet, à partir des paramètres expérimentaux de déterminer le spectre optique ainsi que la distribution de phase à l'intérieur de celui-ci. Il est possible alors d'augmenter la puissance d'une harmonique en sortie de la photodiode par un ajout d'éléments dispersifs. Cette multiplication de fréquence permet la génération de signaux à haute pureté spectrale en bande millimétrique. Une démonstration expérimentale à 90 GHz a été proposée, basée sur un COEO fonctionnant à 30 GHz. Ces résultats sont prometteurs et une intégration du COEO dans un boîtier thermalisé ainsi qu'une gestion plus fine de la dispersion des fibres peut permettre des améliorations significatives sur le bruit de phase du système. / The important rise of telecommunication systems in the past decades, together with the sensitivity improvement of radar systems, has increased the necessity for high spectral purity frequency references at high frequencies. The saturation of classical microwave bandwidths motivated the search of frequency references at higher frequencies, such as K-band. Frequency multiplication from highly stable sources, such as quartz sources, is limited by the increase of the noise floor, which is often prohibitive at millimeter wave frequencies. On the contrary, microwave generation using optics becomes a very efficient technique in this frequency range. Indeed, passive optical resonators or delay lines feature a high Q factor which can be used to stabilize the microwave frequency. The best phase noise performance is today obtained with long delay line oscillators. However, a spurious mode suppression technique has to be implemented in this type of OEOs. The use of an active optical resonator is a third solution, which avoids any locking technique between the laser and the passive resonator. The first architecture of this type has been proposed at the end of the 1990's. In such a system, a mode-locked laser is coupled to a microwave oscillator (COEO). COEO phase noise performances are strongly dependent on the spectral purity of the mode locked laser signal. This thesis work focus on the study and the optimization of this system. Optical amplifiers noise is firstly investigated, in order to determine the optimal conditions to minimize their phase noise contribution to the COEO. A 10 GHz SOA based COEO has been realized and features a low phase noise level reaching - 132 dBc/Hz at 10 kHz from the carrier. An analytical model has also been developed to obtain the locking range of the coupled oscillations. This frequency range is strongly dependent on the coupling efficiency between optical oscillation and the optoelectronic oscillation. This parameter cannot be calculated analytically and an iterative model has been proposed to determine the amplitude and phase of the optical spectrum. Therefore, one can calculate the RF power on the photodiode, on which the coupling efficiency is depending. Since COEO features a large optical frequency comb where each tooth of the comb is phase locked thanks to the mode locked laser, harmonic generation from COEO is possible. Wide frequency comb from high frequency COEO allow millimeter wave generation. The iterative model developed in this work enable to determine the RF power of one specified harmonic from experimental parameters. Harmonic selection can also be performed through the management of the chromatic dispersion. Such frequency multiplication has been implemented to generate a high purity 90 GHz signal from a 30 GHz COEO.These results are promising and an integration of the system in a thermalized box is under process.

No description available.

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.

A true linearized interferometric intensity modulator for pulsed light has been proposed and experimentally presented in this thesis. This has been achieved by introducing a mode-locked laser into one of the arms of a Mach-Zehnder interferometer and injection-locking it to the input light (which is pulsed and periodic). By modulating the injection-locked laser, and combining its output light with the light from the other arm of interferometer in quadrature, one can achieve true linearized intensity modulator. This linearity comes from the arcsine phase response of the injection-locked mode-locked laser (as suggested by steady-state solution of Adler's equation) when it is being modulated. Mode-locked lasers are fabricated using a novel AlGaInAs-InP material system. By using the BCB for planarization and minimizing the metal pad size and directly modulating the laser, we have achieved very effective fundamental hybrid mode-locking at the repetition rate of ~ 23 GHz. This laser also provided the short pulses of 860 fs and 280 fs timing jitter integrated from 1 Hz- 100 MHz. The linearized intensity modulator has been built by using two identical two-section mode-locked lasers with the same length, one as the slave laser in one of the arms of the Mach-Zehnder interferometer injection-locked to the other one as the master which is the input light to the modulator. A low V? of 8.5 mV is achieved from this modulator. Also the current of the gain section or the voltage of the saturable absorber section of the slave laser has been used to apply the modulation signal. A spur free dynamic range of 70 dB.Hz2/3 is achieved when modulating the modulator through the saturable absorber. Modulating the saturable absorber provides a reduced third-order intermodulation tone with respect to modulating the gain. This is simply because of the unwanted amplitude modulation created when modulating the gain section current. Finally an improved design is proposed and demonstrated to improve the modulator performance. This is achieved by introducing a third section to the laser. Using the impurity free vacancy disordering technique the photoluminescence peak of this section is blue-shifted selectively and therefore there would not be any absorption in that passive section. By applying the modulation signal to this passive section rather than applying it to the gain section or saturable absorber section, the amplitude and phase modulation could be decoupled. The experimental results have presented here and an almost six-fold reduction in V? and 5 dB improvement in spur free dynamic range have been achieved. The proposed and demonstrated configuration as an analog optical link has the potential to increase the performance and resolution of photonic analog-to-digital converters.