Full field characterization is an important issue for ultrafast optoelectronics. By suitable nonlinear constrain, several approaches, such as FROG, SPIDERS, MIIPS and so on, have been developed for providing detail information of optical pulses. However, phase matching bandwidth of nonlinear material limit the functionality for broadband signal. In this thesis, linear approach without limitation of phase matching bandwidth is proposed. Theoretically, we successfully demonstrated the feasibility of proposed method. We analyzed the limitation and discussed the pulse compression power with the proposed method. Besides, we also proposed experimental method for this method.

I developed a high power blue laser for use in scientific and technical applications (eg. precision spectroscopy, semiconductor inspection, flow cytometry, etc). It is linearly polarized, single longitudinal and single transverse mode, and a convenient fiber coupled continuous wave (cw) laser source. My technique employs external cavity frequency doubling and provides better power and beam quality than commercially available blue diode lasers. I use a fiber Bragg grating (FBG) stabilized infrared (IR) semiconductor laser source with a polarization maintaining (PM) fiber coupled output. Using a custom made optical and mechanical design this output is coupled with a mode matching efficiency of 96% into the doubling cavity. With this carefully designed and optimized cavity, measurements were carried out at various fundamental input powers. A net efficie ncy of 81 % with an output power of 680 mW at 486 nm was obtained using 840 mW of IR input. Also I report an 87.5 % net efficiency in coupling of blue light from servo locked cavity into a single mode PM fiber. Thus I have demonstrated a total fiber to fiber efficiency of 71% can be achieved in our approach using periodically poled potassium titanyl phosphate (PPKTP). To obtain these results, all losses in the system were carefully studied and minimized.

In many fields, scientific or industrial, optical devices that can be tailored in terms of spectral qualities and output power depending on the application in question are attractive. Nonlinear optics in combination with powerful laser sources provide a tool to achieve essentially any wavelength in the electromagnetic spectrum, and the advancement of material technology during the last decade has opened up new possibilities in terms of realising such devices. The main part of the thesis deals with the development of compact functional lasers based on nonlinear interaction utilising diode-pumped solid-state lasers and also laser diodes. Efficient frequency conversion into the visible and ultraviolet part of the electromagnetic spectrum has been achieved, using both Nd:YAG and Nd:YVO4 lasers as well as a semiconductor laser as the fundamental light sources. For the nonlinear conversion, periodically poled potassium titanyl phosphate (PPKTP), bismuth triborate (BiBO) and beta barium borate (BBO) have been employed. In the search for compact and reliable light sources emitting in the visible part of the spectrum, two different approaches have been explored. First, a scheme based on sum-frequency mixing of a diode-pumped solid-state laser and a laser diode of good beam quality. The idea of this approach is to take advantage of the individual strength of each device, which would be the flexibility in terms of wavelength for the laser diode and the possibility to reach high output power from the diode-pumped solid-state laser. Second, by mixing two different solid-state lasers substantially more output power could be generated albeit at a cost of less freedom in the choice of spectral output. As these two light sources had their central wavelength at 492 nm and 593 nm, respectively, they are highly interesting in biomedical applications since they correspond to the peak absorption of several popular fluorophores. In applications such as lithography, material synthesis and fibre grating fabrication, laser sources emitting in the deep-UV spectrum are desired. An all solid-state 236 nm laser source with 20 mW of average power have been designed and constructed, by frequency-quadrupling a passively Q-switched Nd:YAG laser lasing on a quasi-three level transition. Also, a novel concept for miniaturising solid-state lasers has been examined. Using a heat-conductive polymer carrier, a generic approach especially suited for mass-production of functional laser devices is presented. Finally, it has been proven that GRIN lenses can provide a very compact beam shaping solution to standard laser diodes based on the beam twisting approach. This method offers several advantages such as compactness of the beam shaping system, automated assembly in solid-state laser manufacturing due to the shape of these lenses and polarisation preservation of the laser diode output. / QC 20100903

Performance and reliability of solid state laser diodes in the IR region exceeds those in the visible and UV part of the light spectrum. Single frequency visible and UV laser diodes with higher than 500 mW power are not available commercially. However we successfully stabilized a multi-longitudinal mode IR laser to 860 mW single frequency. This means high efficiency harmonic generation using this laser can produce visible and UV laser light not available otherwise. In this study we examined three major leading nonlinear crystals: PPMgO:SLN, PPKTP and PPMgO:SLT to generate blue light by second harmonic generation. We achieved record high net conversion efficiencies 81.3% using PPMgO:SLT (~500 mW out), and 81.1% using PPKTP (~700 mW out). In both these cases an external resonance buildup cavity was used. We also studied a less complicated single pass waveguide configuration (guided waist size of ~ 5 um compared to ~60 um) to generate blue. With PPMgO:SLN we obtained net 40.4% and using PPKT net 6.8% (110mW and 10.1 mW respectively).

L'interaction d'une impulsion laser intense (~10¹⁴ W /cm²) et de courte durée (femtoseconde) avec un gaz rare induit une polarisation hautement non-linéaire dans le domaine spectral XUV; les harmoniques d'ordre élevés. En raison des propriétés spécifiques du rayonnement harmonique et de ses applications, cette thématique est particulièrement riche et fertile. La production efficace d'harmoniques d'ordres élevés repose à la fois sur la réponse non-linéaire de l'atome unique et un comportement collectif.Le fil directeur des études présentées dans cette thèse est la compréhension et le contrôle de l'accord de phase ou du quasi accord de phase en présence d'une ionisation substantielle du gaz générateur. Dans ce contexte, nous montrons l'importance de la longueur de cohérence sur l'accord de phase en génération d'harmoniques. Nous étudions sa dépendance en fonction de la focalisation du laser, de la pression mais aussi sa dépendance temporelle liée à l'ionisation, effet que nous avons mis en évidence lorsqu'on a cherché à optimiser une double impulsion harmonique. Le travail de développement, sur la station LASERIX, de la source à double impulsion harmonique générée à partir d'un même milieu gazeux et avec un délai picoseconde variable est présenté. Cette source possède un véritable potentiel d'applications scientifiques, injectée dans un milieu amplificateur plasma qu'on appelle laser X, la double impulsion permettra de sonder la réponse temporelle de ce type de milieu. Par ailleurs, des expériences et des simulations menées sur la génération d'harmoniques en propagation guidée visent ainsi à étendre les spectres harmoniques vers les courtes longueurs d'ondes, zone spectrale pour laquelle le laser X à plasmas est émis. Ceci donnera l'accès à une source offrant des caractéristiques complémentaires des lasers X, sources développées en parallèle sur la station LASERIX. / The interaction of an intense laser pulse of short duration with a rare gas induces a highly non-linear polarization in the XUV spectral range: the high order harmonics. Due to the specific properties of the harmonic radiation and its applications, this issue is particularly rich and fertile. The efficient production of high order harmonics is based both on the non-linear response of the single atom and on collective behavior.The principle of the research presented in this thesis is the understanding and control of phase matching or quasi-phase matching in the presence of substantial ionization in the generating gas. In this context, we show the importance of the coherence length on the phase matching in High harmonic generation. We study its dependence on laser focusing, pressure but also its time dependence related to ionization. Moreover, experiments and simulations aim at extending harmonic spectra towards shorter wavelengths, a spectral range for which the X Ray Laser is emitted. This will give access to a source with complementary characteristics as regards to X-ray lasers. This source shall be developed in parallel on the LASERIX station or injected in soft X-ray laser amplifiers.

This thesis describes various methods for producing photon pairs from waveguides. It covers relevant topics such as waveguide coupling and phase matching, along with the relevant measurement techniques used to infer photon pair production. A new proposal to solve the phase matching problem is described along with two conceptual methods for generating entangled photon pairs. Photon pairs are also experimentally demonstrated from a third novel structure called a Bragg Reflection Waveguide (BRW). The new proposal to solve the phase matching problem is called Directional Quasi-Phase Matching (DQPM). It is a technique that exploits the directional dependence of the non-linear susceptiblity ($\chi^{(2)}$) tensor. It is aimed at those materials that do not allow birefringent phase-matching or periodic poling. In particular, it focuses on waveguides in which the interplay between the propagation direction, electric field polarizations and the nonlinearity can change the strength and sign of the nonlinear interaction periodically to achieve quasi-phasematching. One of the new conceptual methods for generating entangled photon pairs involves a new technique that sandwiches two waveguides from two differently oriented but similar crystals together. The idea stems from the design of a Michelson interferometer which interferes the paths over which two unique photon pair processes can occur, thereby creating entanglement in any pair of photons created in the interferometer. By forcing or sandwiching the two waveguides together, the physical space that exists in the standard Micheleson type interferometer is made non-existent, and the interferometer is effectively squashed. The result is that the two unique photon pair processes actually occupy the same physical path. This benefits the stability of the interferometer in addition to miniaturizing it. The technical challenges involved in sandwiching the two waveguides are briefly discussed. The main result of this thesis is the observation of photon pairs from the BRW. By analyzing the time correlation between two single photon detection events, spontaneous parametric down conversion (SPDC) of a picosecond pulsed ti:sapph laser is demonstrated. The process is mediated by a ridge BRW. The results show evidence for type-0, type-I and type-II phase matching of pump light at 783nm, 786nm and 789nm to down converted light that is strongly degenerate at 1566nm, 1572nm, and 1578nm respectively. The inferred efficiency of the BRW was 9.8$\cdot$10$^{-9}$ photon pairs per pump photon. This contrasts with the predicted type-0 efficiency of 2.65$\cdot$10$^{-11}$. This data is presented for the first time in such waveguides, and represents significant advances towards the integration of sources of quantum information into the existing telecommunications infrastructure.

The synchronously pumped femtosecond optical parametric oscillator (OPO) based on was periodically poled 5-mol.% MgO-doped lithuium niobate was demonstrated by means of non-critical quasi phase matching. The femtosecond OPO is cable of operating at room temperature and shows no photorefractive damage. The spectrum can be tuned by varying the cavity length up to 70 £gm, the temperature of the nonlinear crystal from room temperature to 150¢J, and the grating periods. The cavity was designed to resonate at 1.33 £gm with bandwidth of 100 nm. The maximum output intensity of the signal is 43 mW with TEM00 mode. The signal slope efficiency is 11%. The spectrum range of the idler is tunable from 1.8 to 2.8 £gm.

This thesis describes various methods for producing photon pairs from waveguides. It covers relevant topics such as waveguide coupling and phase matching, along with the relevant measurement techniques used to infer photon pair production. A new proposal to solve the phase matching problem is described along with two conceptual methods for generating entangled photon pairs. Photon pairs are also experimentally demonstrated from a third novel structure called a Bragg Reflection Waveguide (BRW). The new proposal to solve the phase matching problem is called Directional Quasi-Phase Matching (DQPM). It is a technique that exploits the directional dependence of the non-linear susceptiblity ($\chi^{(2)}$) tensor. It is aimed at those materials that do not allow birefringent phase-matching or periodic poling. In particular, it focuses on waveguides in which the interplay between the propagation direction, electric field polarizations and the nonlinearity can change the strength and sign of the nonlinear interaction periodically to achieve quasi-phasematching. One of the new conceptual methods for generating entangled photon pairs involves a new technique that sandwiches two waveguides from two differently oriented but similar crystals together. The idea stems from the design of a Michelson interferometer which interferes the paths over which two unique photon pair processes can occur, thereby creating entanglement in any pair of photons created in the interferometer. By forcing or sandwiching the two waveguides together, the physical space that exists in the standard Micheleson type interferometer is made non-existent, and the interferometer is effectively squashed. The result is that the two unique photon pair processes actually occupy the same physical path. This benefits the stability of the interferometer in addition to miniaturizing it. The technical challenges involved in sandwiching the two waveguides are briefly discussed. The main result of this thesis is the observation of photon pairs from the BRW. By analyzing the time correlation between two single photon detection events, spontaneous parametric down conversion (SPDC) of a picosecond pulsed ti:sapph laser is demonstrated. The process is mediated by a ridge BRW. The results show evidence for type-0, type-I and type-II phase matching of pump light at 783nm, 786nm and 789nm to down converted light that is strongly degenerate at 1566nm, 1572nm, and 1578nm respectively. The inferred efficiency of the BRW was 9.8$\cdot$10$^{-9}$ photon pairs per pump photon. This contrasts with the predicted type-0 efficiency of 2.65$\cdot$10$^{-11}$. This data is presented for the first time in such waveguides, and represents significant advances towards the integration of sources of quantum information into the existing telecommunications infrastructure.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-04-01T12:13:47Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) dissertação - Gabriel da Cruz Borba de Andrade.pdf: 8890407 bytes, checksum: 2c4e4b4737788baa1ca937189ea8e250 (MD5) / Made available in DSpace on 2016-04-01T12:13:47Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) dissertação - Gabriel da Cruz Borba de Andrade.pdf: 8890407 bytes, checksum: 2c4e4b4737788baa1ca937189ea8e250 (MD5) Previous issue date: 2014-09-25 / CNPq / Nesta dissertação apresentamos uma investigação teórica e experimental do armazenamento e extração de diversas ordens de não linearidades na interação átomo-luz, utilizando grades de coerência de um ensemble de átomos frios de Césio aprisionados em uma armadilha magneto-ótica. As diversas ordens são exploradas na condição de casamento de fase, modificando apenas o ângulo do feixe leitura em relação ao eixo de definido por um dos feixes da escrita. Elaboramos um modelo teórico consistindo em um sistema atômico de quatro níveis interagindo com campos clássicos com polarizações lineares ortogonais. Ele nos fornece uma expressão analítica para o campo elétrico do feixe gerado na direção de deteção, nos permitindo comparar diversos aspectos experimentais e teóricos e fornecendo um entendimento mais claro acerca do problema. Abordamos particularmente as primeiras três ordens de não linearidade existentes no nosso sistema, a saber, χ(3), χ(5) e χ(7). Dentre os aspectos do sinal estudados estão as polarizações dos feixes gerados, que demonstram clara dependência com a ordem de não linearidade. Analisamos ainda formas de pulso e curvas de saturação com as intensidades dos feixes envolvidos, e os tempos de coerência do sistema, que determinariam até quando seria possível retirar a informação armazenada no meio. / In this dissertation we present a theoretical and experimental investigation of the storage and retrieval of several orders of non-linearity in the light-atom interaction, using coherence gratings of cold cesium atoms ensemble trapped with a magnetic-optical trap. The orders are explored in the phase match condition, modifying only the angle between the reading beam and the axis defined by one of the writing beams. We elaborated a theoretical model of four level system interacting with the classical fields with orthogonal linear polarizations. It provides us an analytical expression from the generated electrical field, allowing us to compare several theoretical and experimental features, clarifying the problem. Particularly, we investigated the first three orders of non-linearity existent in our system, namely χ(3), χ(5) and χ(7). We analyzed the pulses shapes, the saturation curves with the intensity of the beams involved, and the system coherence times which determine how long would be possible to recover the stored information in the atomic medium.

This thesis covers three different topics. The first part is a pedagogical review of the basic principles and recent advances in nonlinear optics. It was originally written as a chapter for the proceedings of the “International School of Physics (Enrico Fermi)” summer school on Photonics held in June, 2014. It is included to provide some background information about nonlinear optical processes in general, and is particularly relevant for the third part of this thesis which is based on the second-order nonlinear optical process of spontaneous parametric downconversion. The second part is based on original research, and deals with superradiance in plasmonic nanostructures. The process of superradiance, as introduced by Dicke in 1954, entails the shortening of the spontaneous emission lifetime of a collection of N quantum emitters as a consequence of the development of a macroscopic dipole moment. Specifically, the lifetime is shortened by a factor of 1/N, and the linewidth is broadened by a factor of N. Such a linewidth dependence has been previously observed in systems of several plasmonic ‘emitters’. However, a clear physical insight into this phenomenon and how it relates to Dicke superradiance has not been shown yet. In this part, we demonstrate by experiment, simulation, and a simple analytical model that Dicke’s superradiance can indeed be observed in a planar array of plasmonic nanoantennas, with a linewidth that scales linearly with the number of nanoantennas within a square wavelength. The third part is also based on original research, and is based on the scal- ing laws of spontaneous parametric downconversion (SPDC) for a type-I phase- matching configuration. The variation of bi-photon generation rate, heralding efficiency and radiance with parameters such as crystal length, pump focussing and collection waist sizes are examined for collinear and non-collinear emission. The results can be used to maximize the brightness of the SPDC source or increase the heralding efficiency depending on the application.