Download or read book Flexible Generation of Picosecond Laser Pulses in the Infrared and Green Spectral Range by Gain Switching of Semiconductor Lasers written by Sina Riecke and published by Cuvillier Verlag. This book was released on 2011-03-15 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Picosecond laser pulses find diverse applications for example in material processing as well as in analysis and sensing. Fluorescence lifetime spectroscopy in particular requires pulses with variable repetition rate and moderate pulse energy. While suitable pulses in the red and blue spectral range can be provided by gain-switched laser diodes, the generation of green laser pulses requires a more elaborate setup based on second harmonic generation. The starting point is a gain-switched infrared distributed-feedback laser diode. The optimization of the laser design and the operating conditions allows to generate spectrally narrow picosecond pulses with a peak power above 1 W. Different gain media are compared for further amplification of these pulses, and options for the miniaturization of the master-oscillator power-amplifier system are explored. The resulting intense infrared pulses are then used for second harmonic generation of green picoseconds pulses. Their peak power of above 5 W exceeds all previous green pulse sources with variable repetition rate. In terms of pulse energy and background suppression, the reported green pulses are thus ideally suited for fluorescence lifetime spectroscopy

Download or read book Two step MOVPE in situ etching and buried implantation applications to the realization of GaAs laser diodes written by Pietro della Casa and published by Cuvillier Verlag. This book was released on 2021-03-25 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work is about two-step epitaxial growth using metalorganic vapor-phase epitaxy (MOVPE) for the realization of edge-emitting near-infrared laser diodes. The fabricated gallium arsenide-based devices fall into two categories: high-power lasers (watt range, multimodal) and tunable lasers (milliwatt range, monomodal). Common to both cases is that surface contamination – particularly that due to oxygen – needs to be removed before regrowth. Thus, in-situ etching with carbon tetrabromide (CBr4) is first studied. The experimental results include kinetic data, the effects of different etching conditions as well as substrate characteristics, and the effectiveness in reducing surface contamination. These investigations pave the way to devices based on 2-step epitaxy combined with in-situ etching. Correspondingly, thermally-tuned SG-DBR lasers operating around 975 nm have been successfully realized, obtaining a tuning range of 21 nm. In addition, the possibility of using electronic tuning in similar devices has been explored. High-power broad-area lasers have also been realized, using two-step epitaxy combined with ex-situ and in-situ etching, to create a buried, shallow “mesa” containing the active zone. This approach allows introducing lateral electrical and optical confinement, and – simultaneously – non-absorbing mirrors at the laser facets. Additionally, a different strategy to create a buried current aperture is presented, which is based on ion implantation followed by epitaxial regrowth. This enables to improve device performance and simultaneously introduce non-absorbing mirrors at the facets with correspondingly increased reliability.

Download or read book Development and analysis of diode laser ns MOPA systems for high peak power application written by Thi Nghiem Vu and published by Cuvillier Verlag. This book was released on 2017-02-14 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work aims at designing and characterizing diode laser based master oscillator power amplifier (MOPA) systems, which are targeted to be implemented into micro light detection and ranging (LIDAR) or differential absorption LIDAR (DIAL) systems for water vapor and aerosol detections. These light sources operate in the ns-pulse regime at a repetition rate of 25 kHz, leading to a resolution in the meter range in an altitude of 6 km. The monolithic MOPA, where Master Oscillator (MO) and Power Amplifier (PA) are integrated on one single chip, operates at 1064 nm wavelength. A peak power of 16.3 W with a pulse width of 3 ns was obtained. A spectral linewidth of about 150 pm and a side mode suppression ratio (SMSR) of 30 dB was observed. A ratio of 9% between the amplified spontaneous emission (ASE) and the laser was estimated. These spectral properties fulfill the requirements for aerosol detection. The hybrid MOPA systems have separate chips for MO and PA. Different hybrid MOPA systems provide a stabilized wavelength at 1064 nm, a tunable wavelength around 975 nm and a dual wavelength around 964 nm. They therefore enable to detect a well-defined absorption line, scan over absorption line and switch between on/off line in DIAL applications, respectively. Their spectral linewidth is below 10 pm, limited by the resolution of the spectrum analyzer. An SMSR of more than 50 dB for the MO and of more than 37 dB for the whole MOPA was reached. A ratio between ASE and laser below 1% was estimated. These spectral properties meet the requirements for water vapor absorption lines detection at atmospheric condition. Diode laser based MOPA systems were therefore proven to be potential light sources for micro-pulse-LIDAR systems – the basis for a new generation of ultra-compact, low-cost systems.

Download or read book Design simulation and analysis of laterally longitudinally non uniform edge emitting GaAs based diode lasers Band 73 written by Jan-Philipp Koester and published by Cuvillier Verlag. This book was released on 2023-09-19 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edge-emitting quantum-well diode lasers based on GaAs combine a high conversion efficiency, a wide range of emission wavelengths covering a span from 630 nm to 1180 nm, and the ability to achieve high output powers. The often used longitudinal-invariant Fabry-Pérot-type resonators are easy to design but often lead to functionality or performance limitations. In this work, the application of laterally-longitudinally non-uniform resonator configurations is explored as a way to reduce unwanted and performance-limiting effects. The investigations are carried out on existing and entirely newly developed laser designs using dedicated simulation tools. These include a sophisticated time-dependent laser simulator based on a traveling-wave model of the optical fields in the lateral-longitudinal plane and a Maxwell solver based on the eigenmode expansion method for the simulation of passive waveguides. Whenever possible, the simulation results are compared with experimental data. Based on this approach, three fundamentally different laser types are investigated: • Dual-wavelength lasers emitting two slightly detuned wavelengths around 784 nm out of a single aperture • Ridge-waveguide lasers with tapered waveguide and contact layouts that emit light of a wavelength of around 970 nm • Broad-area lasers with slightly tapered contact layouts emitting at 910 nm The results of this thesis underline the potential of lateral-longitudinal non-uniform laser designs to increase selected aspects of device performance, including beam quality, spectral stability, and output power.

Download or read book Spectroscopic Applications of Terahertz Quantum Cascade Lasers written by Tasmim Alam and published by Cuvillier Verlag. This book was released on 2020-10-29 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers (QCLs) are attractive for high-resolution spectroscopy because they can provide high power and a narrow linewidth. They are particularly promising in the terahertz (THz) range since they can be used as local oscillators for heterodyne detection as well as transmitters for direct detection. However, THz QCL-based technologies are still under development and are limited by the lack of frequency tunability as well as the frequency and output power stability for free-running operation. In this dissertation, frequency tuning and linewidth of THz QCLs are studied in detail by using rotational spectroscopic features of molecular species. In molecular spectroscopy, the Doppler eff ect broadens the spectral lines of molecules in the gas phase at thermal equilibrium. Saturated absorption spectroscopy has been performed that allows for sub-Doppler resolution of the spectral features. One possible application is QCL frequency stabilization based on the Lamb dip. Since the tunability of the emission frequency is an essential requirement to use THz QCL for high-resolution spectroscopy, a new method has been developed that relies on near-infrared (NIR) optical excitation of the QCL rear-facet. A wide tuning range has been achieved by using this approach. The scheme is straightforward to implement, and the approach can be readily applied to a large class of THz QCLs. The frequency and output stability of the local oscillator has a direct impact on the performance and consistency of the heterodyne spectroscopy. A technique has been developed for a simultaneous stabilization of the frequency and output power by taking advantage of the frequency and power regulation by NIR excitation. The results presented in this thesis will enable the routine use of THz QCLs for spectroscopic applications in the near future.

Download or read book A deep ultraviolet laser light source by frequency doubling of GaN based external cavity diode laser radiation written by Norman Ruhnke and published by Cuvillier Verlag. This book was released on 2022-05-13 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: A compact and portable laser light source emitting in the wavelength range between 210 nm and 230 nm would enable numerous applications outside of laboratory environments, such as sterilization and disinfection of medical equipment, water purification or gas and air analysis using absorption spectroscopy. Such a source is also highly attractive for the identification and quantification of proteins and biomolecules by means of laser-induced fluorescence or Raman spectroscopy. In this thesis, a novel concept to realize such a compact and portable laser light source with low power consumption and an emission around 222 nm is investigated. The developed concept is based on single-pass frequency doubling of a commercially available high-power GaN laser diode emitting in the blue spectral range. Due to the low frequency doubling conversion efficiencies in this wavelength range of about 10-4 W-1, a laser diode with high optical output power above 1 W is required as pump source. Moreover, it has to exhibit narrowband emission in the range of the acceptance bandwidth of the applied nonlinear BBO crystal. Since GaN-based high-power laser diodes typically show broad emission spectra of Δλ = 1…2 nm, stabilizing and narrowing their wavelength by using external wavelength-selective elements is investigated and presented for the first time. With the understanding for the novel concept gained in this work, a compact ultraviolet laser light source was realized. It has a power consumption of less than 10 W and is exceptionally robust due to its immoveable components. The demonstrated output power of 160 μW enables numerous industrial and everyday applications for which previous laser systems have been too complex and overly cost- and energy-intensive.

Download or read book Analysis of Spatio Temporal Phenomena in High Brightness Diode Lasers using Numerical Simulations written by Anissa Zeghuzi and published by Cuvillier Verlag. This book was released on 2020-10-22 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: Broad-area lasers are edge-emitting semiconductor lasers with a wide lateral emission aperture. This feature enables high output powers but also diminishes the lateral beam quality and results in their inherently non-stationary behavior. Research in the area is driven by application, and the main objective is to increase the brightness, which includes both output power and lateral beam quality. To understand the underlying spatio-temporal phenomena and to apply this knowledge in order to reduce costs for brightness optimization, a self-consistent simulation tool taking all essential processes into account is vital. Firstly, in this work a quasi-three-dimensional opto-electronic and thermal model is presented that describes essential qualitative characteristics of real devices well. Time-dependent traveling-wave equations are utilized to characterize the inherently non-stationary optical fields, which are coupled to dynamic rate equations for the excess carriers in the active region. This model is extended by an injection-current-density model to accurately include lateral current spreading and spatial hole burning. Furthermore, a temperature model is presented that includes short-time local heating near the active region as well as the formation of a stationary temperature profile. Secondly, the reasons of brightness degradation, i.e. the origins of power saturation and the spatially modulated field profile, are investigated. And lastly, designs that mitigate those effects limiting the lateral brightness under pulsed and continuous-wave operation are discussed. Amongst those designs a novel “chessboard laser” is presented that utilizes longitudinal-lateral gain-loss modulation and an additional phase tailoring to obtain a very low far-field divergence.

Download or read book AlN base layers for UV LEDs written by Sebastian Walde and published by Cuvillier Verlag. This book was released on 2021-06-22 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: To enable the fabrication of high performance ultraviolet (UV) light-emitting diodes (LEDs) this work aims at improving the quality of AlN base layers on sapphire substrates. The main issues for UV LEDs are still a limited internal quantum efficiency due to a high amount of threading dislocations along with a limited light extraction efficiency due to total internal reflection at the AlN/sapphire interface. Therefore, high-temperature annealing of AlN/sapphire layers and growth on nanopatterned sapphire substrates were comprehensively investigated. High-temperature annealing was applied to AlN layers of different strain and thickness grown by metalorganic vapour phase epitaxy (MOVPE). The threading dislocation density could be successfully reduced by more than one order of magnitude down to 6 × 108 cm-2. Wave optical simulations of UV LEDs on nanopatterned sapphire substrates (NPSS) were conducted and showed a potential increase in light extraction efficiency compared to a planar substrate. The optimized MOVPE growth process on sapphire nanopillars and sapphire nanoholes resulted in a fully coalesced and atomically smooth AlN surface. The threading dislocation density was reduced to 1 ×109 cm-2 for AlN on both nanopillars and nanoholes. UVC LEDs emitting at 265 nm wavelength were grown on top of the developed templates. Increased internal efficiency was obtained by reduced dislocation density and more efficient light extraction was achieved on NPSS in case of a transparent heterostructure and reflective contacts. Thus, the developed templates yield considerable improvement in light output compared to conventional templates.

Download or read book A compact mode locked diode laser system for high precision frequency comparison experiments Band 64 written by Heike Christopher and published by Cuvillier Verlag. This book was released on 2021-04-09 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical frequency combs (OFC) have revolutionized various applications in applied and fundamental sciences that rely on the determination of absolute optical frequencies and frequency differences. The latter requires only stabilization of the spectral distance between the individual comb lines of the OFC, allowing to tailor and reduce system complexity of the OFC generator (OFCG). One such application is the quantum test of the universality of free fall within the QUANTUS experimental series. Within the test, the rate of free fall of two atomic species, Rb and K, in micro-gravity will be compared. The aim of this thesis was the development of a highly compact, robust, and space-suitable diode laser-based OFCG with a mode-locked optical spectrum in the wavelength range around 780 nm. A diode laser-based OFCG was developed, which exceeds the requirements with a spectral bandwidth > 16 nm at 20 dBc, a comb line optical power > 650 nW (at 20 dBc), a pulse repetition rate of 3.4 GHz, and an RF linewidth of the free-running pulse repetition rate < 10 kHz. To realize a proof-of-concept demonstrator module, the diode laser-based OFCG was hybrid-integrated into a space-suitable technology platform that has been developed for future QUANTUS experiments. Proof of sufficient RF stability of the OFCG was provided by stabilizing the pulse repetition rate to an external RF reference. This resulted in a stabilized pulse repetition rate with an RF linewidth smaller than 1.4 Hz (resolution limited), thus exceeding the requirement. The developed diode laser-based OFCG represents an important step towards an improved comparison of the rate of free fall of Rb and K quantum gases within the QUANTUS experiments in micro-gravity.

Download or read book Ultrashort Light Pulses written by S.L. Shapiro and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soon after the invention of the laser, a brand-new area of endeavour emerged after the discovery that powerful ultrashort (picosecond) light pulses could be extracted from some lasers. Chemists, physicists, and engineers quickly recognized that such pulses would allow direct temporal studies of extremely rapid phenomena requiring, however, development of revolutionary ultrafast optical and electronic devices. For basic research the development of picosecond pulses was highly important because experimentalists were now able to measure directly the motions of atoms and molecules in liquids and solids: by disrupting a material from equilibrium with an intense picosecond pulse and then recording the time of return to the equilibrium state by picosecond techniques. Studies of picosecond laser pulses-their generation and diagnostic tech niques-are still undergoing a fairly rapid expansion, but a critical review of the state of the art by experienced workers in the field may be a timely help to new experimentalists. We shall review the sophisticated tools developed in the last ten years, including the modelocked picosecond-pulse-emitting lasers, the picosecond detection techniques, and picosecond devices. Moreover, we shall outline the basic foundations for the study of rapid events in chemistry and physics, which have emerged after many interesting experiments and which are now being applied in biology. An in-depth coverage of various aspects of the picosecond field should be helpful to scientists and engineers alike.

Download or read book Generating Picosecond Pulses from Q switched Microchip Lasers written by Alexander Craig Butler and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their first demonstration in the 1960s, picosecond laser pulses have initiated and defined the area of ultrafast laser physics. Their ability to generate a burst of high-intensity, coherent light has opened up areas of science and enabled the observation of events that would otherwise remain out of the realm of human understanding. -- The particular mechanism commonly associated with picosecond pulse generation is mode-locking. These systems are typically complex, bulky and correspondingly expensive. A compact, cheap and robust option that produces comparable pulses would be of great value to the scientific and engineering communities. To this end, we examine the growing area of Q-switched microchip lasers: simple and compact devices that generate sub-nanosecond pulses by virtue of extremely reduced resonator cavity lengths. Incorporation of a passive Q-switch device, a semiconductor saturable absorber mirror or SESAM, enables truly minimal cavity lengths, and therefore minimal pulse durations, to be accessed. -- In this thesis we explore the limits of generating the shortest pulses from such microchip lasers. We develop a comprehensive numerical simulation model, based on the laser rate equations, to effectively model SESAM Q-switched microchip lasers. We incorporate additional phenomena such as two-photon absorption (TPA) in the Q-switch and SESAM etalons to derive a complete picture of the abilities of these micro-lasers. We show that TPA will increasingly affect the performance of these lasers, as shorter pulses are generated, and suspect that our model underestimates its effect on our experimental results. We examine the switching dynamics of the SESAM and describe the role of relaxation oscillations in the switching process, as well as demonstrating controlled partial switching. Scaling dependencies between laser component parameters and laser performance are drawn, providing guidelines for development of these lasers. We examine these relationships in experiment and verify the key relationship between short cavities and short pulses. We demonstrate a laser with record short pulses of 22 ps duration by extending the scaling of these lasers to the shortest demonstrated cavity length of 110 μm. -- To alleviate the low efficiency associated with lasers using thin gain media, we propose, model and develop an energy-scavenging amplification scheme. We demonstrate that a complete, amplified Q-switched microchip laser system has the potential to rival amplified mode-locked systems in generating few-picosecond, microjoule pulses, although practical validation of this will approach require careful laser engineering.

Download or read book Mode locked Lasers Introduction To Ultrafast Semiconductor And Fiber Lasers written by Niloy K Dutta and published by World Scientific. This book was released on 2024-05-21 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: This invaluable book provides a comprehensive treatment of the design and application of Mode Locked Lasers and Short Pulse Generation. With the advances in semiconductor laser and fiber laser technologies in the 1980s to now, these devices have been made compact, refined, and developed for a wide range of applications including further scientific studies.Semiconductor mode-locked lasers are stable pulse sources and can be made over a range of wavelengths where laser operation is feasible. Rare earth doped fiber lasers or planar waveguides extend this range further and can provide compact pulsed sources. The principles of operation, analysis, design and fabrication of these sources are described. Recent results on high repetition rate and high-power pulse generation from these compacts sources are also described, together with current and future directions of application of these types of laser sources.Mode-Locked Lasers: Introduction to Ultrafast Semiconductor and Fiber Lasers is self-contained and unified in presentation. It can be used as an advanced text by graduate students and by practicing engineers. It is also suitable for non-experts who wish to have an overview of mode-locked lasers and pulse generation. The explanations in the book are detailed enough to capture the interest of the curious reader and complete enough to provide the necessary background to explore the subject further.

Download or read book An investigation on semiconductor lasers in a picosecond regime written by and published by . This book was released on 1911 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Este trabalho apresenta alguns estudos experimentais sobre a geração de pulsos óticos curtos com lasers semicondutores e a deteção desses pulsos. Descreve-se inicialmente a geração de pulsos elétricos curtos com geradores a transistor avalanche e chaves fotocondutivas. Foi desenvolvido um modelo de circuito equivalente para lasers multi-modos, que permite simular com precisão a resposta ótica do dispositivo para diferentes condições de alimentação. Foram também desenvolvidos transformadores de impedância de larga banda passante. Linhas de transmissão de diversos tipos e substratos de diferentes constantes dielétricas foram empregados. Comprovou-se experimentalmente a melhoria da resposta ótica do laser a pulsos curtos de corrente com o uso desses transformadores, comparada com os arranjos convencionais. Mostrou-se também experimentalmente que os transformadores aqui desenvolvidos proporcionam um aumento significativo na largura de banda de sistemas de fotodetetores rápidos. São apresentados resultados experimentais de geração de pulsos óticos curtos com lasers semicondutores, usando-se as técnicas de mode-locking e chaveamento de ganho. Finalmente são sugeridas algumas técnicas alternativas para a medição indireta dos pulsos gerados pelo processo de mode-locking, e são mostrados alguns resultados preliminares.

Download or read book Short Pulse Generation and Semiconductor Laser Dynamics written by Homayoon Ansari and published by . This book was released on 1988 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Field Guide to Laser Pulse Generation written by Rüdiger Paschotta and published by SPIE-International Society for Optical Engineering. This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This guide provides information on laser pulse generation, including Q switching, gain switching, mode locking, and the amplification of ultrashort pulses to high energies. Pulse characterisation is also covered, along with the physical aspects and various technical limitations.

Download or read book Femtosecond Laser Pulses written by Claude Rulliere and published by Springer Science & Business Media. This book was released on 2005 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the second edition of this advanced textbook written for scientists who require further training in femtosecond science. Four years after pub- cation of the ?rst edition, femtosecond science has overcome new challenges and new application ?elds have become mature. It is necessary to take into account these new developments. Two main topics merged during this period that support important scienti?c activities: attosecond pulses are now gen- ated in the X-UV spectral domain, and coherent control of chemical events is now possible by tailoring the shape of femtosecond pulses. To update this advanced textbook, it was necessary to introduce these ?elds; two new ch- ters are in this second edition: “Coherent Control in Atoms, Molecules, and Solids”(Chap.11)and“AttosecondPulses”(Chap.12)withwell-documented references. Some changes, addenda, and new references are introduced in the ?rst edition’s ten original chapters to take into account new developments and updatethisadvancedtextbookwhichistheresultofascienti?cadventurethat started in 1991. At that time, the French Ministry of Education decided that, in view of the growing importance of ultrashort laser pulses for the national scienti?c community, a Femtosecond Centre should be created in France and devoted to the further education of scientists who use femtosecond pulses as a research tool and who are not specialists in lasers or even in optics.

Download or read book Few Cycle Laser Pulse Generation and Its Applications written by Franz X. Kärtner and published by Springer Science & Business Media. This book was released on 2004-09-14 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the physics, technology and applications of short pulse laser sources that generate pulses with durations of only a few optical cycles. The basic design considerations for the different systems such as lasers, parametric amplifiers and external compression techniques which have emerged over the last decade are discussed to give researchers and graduate students a thorough introduction to this field. The existence of these sources has opened many new fields of research that were not possible before. These are UV and EUV generation from table-top systems using high-harmonic generation, frequency metrology enabling optical frequency counting, high-resolution optical coherence tomography, strong-field ultrafast solid-state processes and ultrafast spectroscopy, to mention only a few. Many new applications will follow. The book attempts to give a comprehensive, while not excessive, introduction to this exciting new field that serves both experienced researchers and graduate students entering the field. The first half of the book covers the current physical principles, processes and design guidelines to generate pulses in the optical range comprising only a few cycles of light. Such as the generation of relatively low energy pulses at high repetition rates directly from the laser, parametric generation of medium energy pulses and high-energy pulses at low repetition rates using external compression in hollow fibers. The applications cover the revolution in frequency metrology and high-resolution laser spectroscopy to electric field synthesis in the optical range as well as the emerging field of high-harmonic generation and attosecond science, high-resolution optical imaging and novel ultrafast dynamics in semiconductors. These fields benefit from the strong electric fields accompanying these pulses in solids and gases during events comprising only a few cycles of light.