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Improvement Of The Beam Quality Of High Power Broad Area Semiconductor Diode Lasers By Means Of An External Resonator
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Book Synopsis Improvement of the beam quality of high-power broad area semiconductor diode lasers by means of an external resonator by : Ahmad Ibrahim Bawamia
Download or read book Improvement of the beam quality of high-power broad area semiconductor diode lasers by means of an external resonator written by Ahmad Ibrahim Bawamia and published by Cuvillier Verlag. This book was released on 2012-04-03 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: The operation of high-power broad area laser diodes in an external resonator is studied with respect to the improvement of their lateral beam quality. A simple setup with a broad area laser diode as gain medium, two lenses and an external mirror is considered. The concept relies on the ability of the active region of the laser diode to act as a spatial filter for higher order modes oscillating inside the resonator. The geometries of the external cavity laser that favor fundamental mode operation in the lateral direction are inferred with the help of a theoretical model based on the ABCDmatrix treatment of Gaussian beams in a passive stable resonator. Thermal lensing that arises in the broad area laser diode is included in the model. The simulation results show that, for a given strength of the thermal lens arising inside the broad area laser diode, there exists one geometry of the external resonator that produces single mode operation as well as a high overlap between the optical mode and the gain medium of the laser diode. A novel experimental procedure that quantifies the thermal lens arising in the broad area laser diode to be used inside the external resonator is developed. The thermal lens coefficient is determined for different injection currents and pulse widths. The reliability of the method is validated by the comparison of the obtained results with values of the thermal lens coefficient derived from independent measurements and from the simulation of the temperature distribution inside the laser diode. Furthermore, the latter simulation at different pulse widths enables to explain the observed saturation of the thermal lens coefficient as injection current and pulse width are increased. The external cavity laser comprising a test broad area laser diode that emits at a wavelength in the region of 1.06μm, two lenses, and an external mirror is implemented. Additionally, an adjustable intra-cavity slit that serves as a supplementary spatial filter is inserted in the setup. The evolution of the output power and of the beam quality of the device as a function of the length of the resonator and of the width of the slit is studied at injection currents of 1A (close to laser threshold) and 5A (high power operation). It is observed that at both injection currents, the beam quality of the emission is significantly improved when the length of the resonator and the width of the slit are adjusted to their optimal values. In the case of the experiments at an injection current of 1A, the optimal conditions for the operation of the external resonator correspond to the theoretical predictions, but, at an injection current of 5A, they have to be determined experimentally since the behavior of the laser cannot be explained by the model of the passive resonator anymore. The criterion used to assess the performance of the external cavity laser, as compared to a similar free running laser, is the maximum output power weighted by the M2 value. In that respect, at an injection current of 1A, the M2 value is improved from 9.0 to 3.5, with an output power of 0.35W. At the injection current of 5A, the M2 value is improved from 18.7 to 5.6, with a corresponding output power of 2.5W. The latter result compares with the best values reported in the literature for the operation of broad area laser diodes in an external resonator.
Book Synopsis Development and analysis of diode laser ns-MOPA systems for high peak power application by : Thi Nghiem Vu
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.
Book Synopsis Analysis of Spatio-Temporal Phenomena in High-Brightness Diode Lasers using Numerical Simulations by : Anissa Zeghuzi
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.
Book Synopsis A compact mode-locked diode laser system for high precision frequency comparison experiments (Band 64) by : Heike Christopher
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.
Book Synopsis A deep ultraviolet laser light source by frequency doubling of GaN based external cavity diode laser radiation by : Norman Ruhnke
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.
Book Synopsis Spectroscopic Applications of Terahertz Quantum-Cascade Lasers by : Tasmim Alam
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.
Book Synopsis Design, simulation and analysis of laterally-longitudinally non-uniform edge-emitting GaAs-based diode lasers (Band 73) by : Jan-Philipp Koester
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.
Book Synopsis Two-step MOVPE, in-situ etching and buried implantation: applications to the realization of GaAs laser diodes by : Pietro della Casa
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.
Book Synopsis AlN base layers for UV LEDs by : Sebastian Walde
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.
Book Synopsis Advanced High-power Lasers by : Marek Osiński
Download or read book Advanced High-power Lasers written by Marek Osiński and published by SPIE-International Society for Optical Engineering. This book was released on 2000 with total page 906 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work brings together a series of papers dealing with various aspects of advanced high-power laser technology.
Book Synopsis Semiconductor Laser Diode by : Dnyaneshwar Patil
Download or read book Semiconductor Laser Diode written by Dnyaneshwar Patil and published by BoD – Books on Demand. This book was released on 2012-04-25 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book represents a unique collection of the latest developments in the rapidly developing world of semiconductor laser diode technology and applications. An international group of distinguished contributors have covered particular aspects and the book includes optimization of semiconductor laser diode parameters for fascinating applications. This collection of chapters will be of considerable interest to engineers, scientists, technologists and physicists working in research and development in the field of semiconductor laser diode, as well as to young researchers who are at the beginning of their career.
Book Synopsis Laser Resonators and Beam Control by :
Download or read book Laser Resonators and Beam Control written by and published by . This book was released on 2002 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis High-Power Diode Lasers by : Roland Diehl
Download or read book High-Power Diode Lasers written by Roland Diehl and published by Springer Science & Business Media. This book was released on 2003-07-01 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting from the basics of semiconductor lasers with emphasis on the generation of high optical output power the reader is introduced in a tutorial way to all key technologies required to fabricate high-power diode-laser sources. Various applications are exemplified.
Download or read book Optics Letters written by and published by . This book was released on 2008 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :Conference on Lasers and Electro-optics Europe Publisher :IEEE Standards Office ISBN 13 :9780780377349 Total Pages :808 pages Book Rating :4.3/5 (773 download)
Book Synopsis 2003 Conference on Lasers and Electro-Optics Europe by : Conference on Lasers and Electro-optics Europe
Download or read book 2003 Conference on Lasers and Electro-Optics Europe written by Conference on Lasers and Electro-optics Europe and published by IEEE Standards Office. This book was released on 2003 with total page 808 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Conference on Lasers and Electro-optics Europe by :
Download or read book Conference on Lasers and Electro-optics Europe written by and published by . This book was released on 2003 with total page 816 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Novel In-plane Semiconductor Lasers III by : Claire F. Gmachl
Download or read book Novel In-plane Semiconductor Lasers III written by Claire F. Gmachl and published by SPIE-International Society for Optical Engineering. This book was released on 2004 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of SPIE present the original research papers presented at SPIE conferences and other high-quality conferences in the broad-ranging fields of optics and photonics. These books provide prompt access to the latest innovations in research and technology in their respective fields. Proceedings of SPIE are among the most cited references in patent literature.
