In recent years laser technology has increasingly developed with the use of fiber lasers and this has provided the possibility to implement different techniques in the defense industry. LADAR is at the forefront of these techniques. Fiber lasers constitute a perfect source for LADAR systems due to their excellent robustness, compact size and high-power generation capability. In this study we will explore the development of a pulsed fiber laser source for a LADAR system that can obtain high resolution 3D images in eye-safe region. A high power, all fiber integrated erbium system with strictly single mode operation in eye-safe region based on MOPA (master oscillator power amplifier) configuration with seed source and amplifier part was developed. Both the use of an actively mode locked laser with erbium doped fiber and fiber coupled modulated distributed feedback diode laser were investigated as seed sources for the amplifier part. Both erbium doped single clad fiber and erbium-ytterbium doped double clad gain fiber were used in this amplifier system. After amplification of the actively mode locked laser, 12 W of average optical power was obtained through single mode fiber with 1ns pulse duration at 10 MHz which corresponds to 1.2 kW peak power. For the fiber coupled DFB diode laser, 9.5W average power was obtained with around 8 ns duration pulses at 100 kHz and about 9.2 W average power was also obtained with around 700 ps duration pulses at 1 MHz through strictly single mode fiber at the output of the same amplifier system as was used in the actively mode locked seed source. In both cases calculated peak power was around 10 kW v which is estimated as the highest peak power for an all fiber integrated system with single mode operation. The development of such a fiber system with high power capability, compact size and free of misalignment is expected to be useful for LADAR application as well as other areas such as eye surgery, 3D silicon processing or any other material processing applications.

Master of Science / Department of Physics / Brian R. Washburn / This thesis reports our attempt towards achieving a phase stabilized free-space nonlinear polarization rotation (NPR) mode locked erbium doped fiber laser frequency comb system. Optical frequency combs generated by mode-locked femtosecond fiber lasers are vital tools for ultra-precision frequency metrology and molecular spectroscopy. However, the comb bandwidth and average output power become the two main limiting elements in the application of femtosecond optical frequency combs. We have specifically investigated the free-space mode locking dynamics of erbium-doped fiber (EDF) mode-locked ultrafast lasers via nonlinear polarization rotation (NPR) in the normal dispersion regime. To do so, we built a passively mode-locked fiber laser based on NPR with a repetition rate of 89 MHz producing an octave-spanning spectrum due to supercontinuum (SC) generation in highly nonlinear fiber (HNLF). Most significantly, we have achieved highly stable self-starting NPR mode-locked femtosecond fiber laser based frequency comb which has been running mode locked for the past one year without any need to redo the mode locking. By using the free-space NPR comb scheme, we have not only shortened the cavity length, but also have obtained 5 to 10 times higher output power (more than 30 mW at central wavelength of 1570 nm) and much broader spectral comb bandwidth (about 54 nm) compared to conventional all-fiber cavity structure with less than 1 mW average output power and only 10 nm spectral bandwidth. The pulse output from the NPR comb is amplified through a 1 m long EDF, then compressed by a length of anomalous dispersion fiber to a near transform limited pulse duration. The amplified transform limited pulse, with an average power of 180 mW and pulse duration of 70 fs, is used to generate a supercontinuum of 140 mW. SC generation via propagation in HNLF is optimized for specific polling period and heating temperature of PPLN crystal for SHG around 1030 nm. At last, we will also discuss the attempt of second harmonic generation (SHG) by quasi phase matching in the periodically polled lithium niobate (PPLN) crystal due to nonlinear effect corresponding to different polling period and heating temperature.

Made available in DSpace on 2016-03-15T19:37:34Z (GMT). No. of bitstreams: 1 Claudia Barros dos Santos.pdf: 3294972 bytes, checksum: b848d69d9c6a8c824e5142a4e3659d37 (MD5) Previous issue date: 2011-01-21 / In this work, we inserted two Arrayed Waveguide Gratings (AWGs), in an Erbium doped fiber ring cavity laser, where a single gain medium at room temperature can emit laser in multiples wavelengths, simultaneous and individualy controlled. The setup allowed us to check different functions in the ring cavity. Here we show emission in CW regime, Passive Mode-Locking, using Carbon Nanotubes as saturable absorbers and finally Active mode-locking at 7GHz, simultaneously. / Neste trabalho, fez-se a inserção de duas grades de difração matriciais com guias de onda, ou AWGs (Arrayed Waveguide Gratings) em uma cavidade laser de fibra dopada com Érbio, onde um único meio de ganho em temperatura ambiente pode gerar ação laser em múltiplos comprimentos de onda, com emissões simultâneas e controladas individualmente. A configuração utilizada permitiu o teste com diferentes regimes de operação simultâneos dentro da cavidade. Mostramos a possibilidade de emissão laser em regime CW, em regime de mode-locking passivo, com o uso de nanotubos de carbono como absorvedor saturável e, por último, em regime de modelocking ativo com uma freqüência de modulação de 7 GHz.

Made available in DSpace on 2016-03-15T19:37:35Z (GMT). No. of bitstreams: 1 Claudia Barros dos Santos.pdf: 3294972 bytes, checksum: b848d69d9c6a8c824e5142a4e3659d37 (MD5) Previous issue date: 2011-01-21 / In this work, we inserted two Arrayed Waveguide Gratings (AWGs), in an Erbium doped fiber ring cavity laser, where a single gain medium at room temperature can emit laser in multiples wavelengths, simultaneous and individualy controlled. The setup allowed us to check different functions in the ring cavity. Here we show emission in CW regime, Passive Mode-Locking, using Carbon Nanotubes as saturable absorbers and finally Active mode-locking at 7GHz, simultaneously. / Neste trabalho, fez-se a inserção de duas grades de difração matriciais com guias de onda, ou AWGs (Arrayed Waveguide Gratings) em uma cavidade laser de fibra dopada com Érbio, onde um único meio de ganho em temperatura ambiente pode gerar ação laser em múltiplos comprimentos de onda, com emissões simultâneas e controladas individualmente. A configuração utilizada permitiu o teste com diferentes regimes de operação simultâneos dentro da cavidade. Mostramos a possibilidade de emissão laser em regime CW, em regime de mode-locking passivo, com o uso de nanotubos de carbono como absorvedor saturável e, por último, em regime de modelocking ativo com uma freqüência de modulação de 7 GHz.

Made available in DSpace on 2016-03-15T19:37:45Z (GMT). No. of bitstreams: 1 Heidi Kaori Sato Pertile.pdf: 2322047 bytes, checksum: aaee9a054b94e9557394faaf3251bec9 (MD5) Previous issue date: 2013-01-24 / In this work we present a study on the generation of pulse train in an Erbium doped fiber laser in the hybrid mode-locking regime operating with short pulses at high repetition rates. The short pulses are generated by passive mode-locking technique using carbon nanotubes as saturable absorbers. High repetition rates are generated by active mode-locking technique using a phase modulator. We built cavities with three different mode-locking regimes: active, passive and, finally, hybrid, to compare results. In active and hybrid cavities we used an electro-optical modulator. In passive and hybrid cavities we used a homemade film of a polymer containing carbon nanotubes with diameter of 1 nm. With the cavity operating in the hybrid regime we obtained pulse durations of 1.77 ps with repetition rate of 10 GHz. / Neste trabalho apresentamos um estudo sobre a geração de trem de pulsos em laser à fibra dopada com Érbio operando em regime de acoplamento híbrido de modos, com pulsos curtos a altas taxas de repetição. Os pulsos curtos são obtidos pela técnica de acoplamento passivo de modos utilizando absorvedores saturáveis de carbono. As altas taxas de repetição são obtidas pela técnica de acoplamento ativo de modos através de um modulador. Construímos três cavidades distintas: ativa, passiva e finalmente a híbrida para comparação de resultados. Nas cavidades ativa e híbrida foi utilizado um modulador eletro-óptico de fase e, nas cavidades passiva e híbrida foi utilizado um filme de um polímero (NOA 73TM) contendo nanotubos de carbono com diâmetro de 1 nm por nós fabricado. Com a cavidade em regime híbrido de modos, foi obtida uma duração de pulso de 1,77 ps com uma taxa de repetição de 10 GHz.

Made available in DSpace on 2016-03-15T19:38:55Z (GMT). No. of bitstreams: 1 CLAUDIA BARROS DOS SANTOS DEMORI.pdf: 3640553 bytes, checksum: 13700107293ec12ced27c0e70d6fb334 (MD5) Previous issue date: 2015-08-25 / This work shows an Erbium doped-fiber Laser with many frequencies and many operation regimes based on integration of two paired arrayed waveguide gratings (AWGs) into a ring cavity. The AWGs are highlighted, since 2000, as key technology for multifrequencies lasers for optical communications, spectroscopy, image, astronomy and others applications. Fundamentally, gratings work splitting waveguide signal and since insertion in the cavity they allow simultaneous operating of tens of wavelength. We explore each one of these wavelength withing Erbium gain region, doing channels in different regimes of operation. These regimes may be continuous or pulsed. The advantage is that each channel may be modulated independently. Simultaneous operation with high repetition rates at 10 and 40 GHz were demonstrated, as continuous wave. The laser is stable, versatile and multifunctional. It is possible that more operating regimes, as passive mode-locking, be explored. We showed by this work efficient way to passive mode-locking by carbon nanotubes as saturable absorbers. Soon, the passive mode-locking is a potential regime for the demonstrated laser. As the new bi-dimensional materials, that look efficient for passive mode-locking and in the future, hybrid mode-locking, as graphene and black phosphor. / Esta tese trata de demonstrar um Laser de fibra dopada com Érbio com múltiplas frequências e múltiplos regimes de operação simultâneos baseados na integração de duas grades de difração pareadas (Arrayed Waveguide Gratings, AWGs) dentro de uma cavidade de laser de fibra. As AWGs são apontadas, desde o ano 2000, como tecnologia fundamental em lasers de múltiplas frequencias para as comunicações ópticas, para espectroscopia, imageamento, astronomia, e outras aplicações. Fundamentalmente, as grades funcionam como divisores do sinal óptico e quando inseridas dentro da cavidade de um laser de fibra permitem a operação simultânea de dezenas de comprimentos de onda. Neste trabalho, exploramos cada comprimento de onda, dentro da região de ganho do Érbio, com um regime de operação diferente. Esse regime pode ser pulsado ou contínuo. A vantagem do laser apresentado é que cada comprimento de onda é um canal que pode ser modulado de forma independente. Pôde-se demonstrar operação simultânea com regimes a altas taxas de repetição como 10 GHz e 40 GHz, assim como CW. O laser é estável, versátil e multifuncional. É possível que mais regimes de operação, como o regime de acoplamento de modos passivo sejam explorados. Mostramos ao longo deste trabalho maneiras eficientes de acoplar modos passivamente, utilizando nanotubos de carbono como absorvedores saturáveis, logo a técnica de acoplamento de modos passivo é um dos regimes em potencial para este laser. Assim como, o uso de novos materiais bidimensionais, que se mostram eficientes para o acoplamento de modos passivo e futuramente híbrido, como o grafeno e o fósforo negro.

Made available in DSpace on 2016-03-15T19:38:52Z (GMT). No. of bitstreams: 1 Henrique Guimaraes Rosa.pdf: 6486656 bytes, checksum: 6fc9fe7875ed2cceb89c9f5179b9f028 (MD5) Previous issue date: 2015-02-25 / Fundo Mackenzie de Pesquisa / In this thesis, we present results on the fabrication, transfer and characterization of chemical vapor deposition (CVD) graphene and exfoliated graphene over glass and optical fiber substrates, to study optical properties of graphene and its application as a saturable absorber for Erbium-doped fiber laser (EDFL). Monolayer CVD graphene and stacked CVD graphene samples were fabricated and characterized, transferred to the transverse face of optical fibers, and a study on the relation between the optical properties of graphene samples and the properties of ultrashort laser pulses generated in (EDFL) was performed. Furthermore, we have developed a technique for transferring exfoliated nanomaterials which allowed us to transfer exfoliated graphene onto optical fiber s faces and align the graphene flake to the fiber core. With this transfer technique it is possible to fabricate samples with controlled number of graphene layers onto optical fiber faces. As application, we demonstrate ultrashort pulse generation in Erbium-doped fiber laser with exfoliated monolayer graphene samples as saturable absorber. This is the first time that ultrashort laser pulses are generated with a single exfoliated monolayer graphene sample. / Nesta tese, apresentamos resultados sobre a fabricação, transferência e caracterização de grafeno CVD (grafeno fabricado por deposição química de vapor chemical vapour deposition) e de grafeno esfoliado em substratos de vidro e em fibras ópticas, para o estudo das propriedades ópticas do grafeno e sua aplicação como absorvedor saturável em laser à fibra dopada com Érbio (EDFL). Foram fabricadas e caracterizadas amostras de grafeno CVD monocamada e de grafeno CVD empilhado, transferidas para a face transversal de fibras ópticas, e com estas amostras foram feitos estudos sobre a relação entre as propriedades ópticas do grafeno e as propriedades de pulsos ultracurtos gerados em EDFL. Além disto, desenvolvemos uma técnica para a transferência de nanomateriais esfoliados que permitiu a transferência de grafeno esfoliado para fibras ópticas e seu alinhamento com o núcleo da fibra. Com esta técnica de transferência é possível fabricar amostras com controlado número de camadas de grafeno em fibra óptica. Como aplicação, demonstramos a geração de pulsos em EDFL com uma amostra de grafeno esfoliado monocamada como absorvedor saturável. Esta é a primeira vez que pulsos ultracurtos são gerados em lasers à fibra com amostra de grafeno esfoliado de uma única camada sobre a face transversal da fibra óptica.