In this chapter, both blue and green high-power tunable diode laser systems based on GaN broad-area diode laser (BAL) in Littrow external cavity are demonstrated. For blue diode laser system, for high-power application, an output power around 530 mW over a 1.4 nm tunable range is obtained; for wide tunable range application, an output power around 80 mW over a 6.0 nm tunable range is obtained. For the green diode laser system, for high-power application, an output power around 480 mW with a tunable range of 2.1 nm is achieved; for wide tunable range application, an output power of 50 mW with a tunable range of 9.2 nm is achieved. The tuning range and output power optimization of an external-cavity diode laser system is investigated based on the experimental results obtained in the blue and green external-cavity GaN diode laser systems. The obtained results can be used as a guide for selecting gratings for external-cavity diode lasers for different requirements. The temporal dynamics of the green diode laser system is studied experimentally, and pulse package oscillation is observed, for the first time to our knowledge, in a BAL with an external-cavity grating feedback.

This is the first book on tunable external cavity semiconductor diode lasers, providing an up-to-date survey on the physics, technology, and performance of widely applicable coherent radiation sources of tunable external cavity diode lasers. The purpose is to provide a thorough account of the state-of-the-art of tunable external cavity diode lasers which is achieved by combining this account with basic concepts of semiconductor diode lasers and its tunability with monolithic structures. The practical and accessible information in this volume will enable the reader to study external cavity diode laser, to build up the systems of external cavity diode laser as well as to develop advanced systems for their particular applications. This book will appeal to undergraduate and graduate students, scientists and engineers alike.

The laser has become more and more important in scientific research and industrial applications. Now, the laser wavelength can cover the range from ultraviolet to terahertz and output laser performance has significantly progressed in recent years. This book is focused on the advanced diode laser, fiber laser, and their applications in laser ablation, laser-introduced fluorescence, and laser treatment. The advantages of laser technology are shown comprehensively.

Diode lasers have many advantages such as small size, high efficiency and small angular dispersion of the collimated beam. However they also have some problems like lack of frequency stability. They can not be tuned in wavelength. An external cavity can solve these problems and decrease the laser linewidth. To obtain a tunable, narrow linewidth light source, antireflection coatings were applied to commercial diode lasers which were then tested in an external cavity. Laser characteristics, such as threshold current, spectral behavior, I-V-curves, tuning range, and bandwidth were measured for the original diode laser and then compared to the measurements in an external cavity with and without antireflection (AR) coatings. The tuning range approximately doubled after AR coating. The modal stability was found to be better by a factor of 7 in the external cavity. The power amplification through the external cavity was as high as 50. It was also attempted to process laser diodes from material fabricated at OSU, however the resulting diodes showed a high series resistance and were not usable for this project. Additional work needs to be done in this area. The result of this work is a stable external cavity diode laser tunable over an 18 nm bandwidth which can be used as a tunable source in many applications.

Broadly tunable lasers continue to have a tremendous impact in many and diverse fields of science and technology. From a renaissance in laser spectroscopy to Bose-Einstein condensation, the one nexus is the tunable laser. Tunable Laser Applications describes the physics and architectures of widely applied tunable laser sources. Fully updated and ex

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.

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.

An accessible yet rigorous introduction to nanophotonics, covering basic principles, technology, and applications in lighting, lasers, and photovoltaics. Providing a wealth of information on materials and devices, and over 150 color figures, it is the 'go-to' guide for students in electrical engineering taking courses in nanophotonics.

William Risk, Timothy Gosnell and Arto Nurmikko have brought together their diverse expertise from industry and academia to write the first fully comprehensive book on the generation and application of blue-green lasers. This volume describes the theory and practical implementation of three techniques for the generation of blue-green light: nonlinear frequency conversion of infrared lasers, upconversion lasers, and wide bandgap semiconductor diode lasers. In addition, it looks at the various applications that have driven the development of compact sources of blue-green light, and reflects on the recent application of these lasers in high-density data storage, color displays, reprographics, and biomedical technology. Compact Blue-Green Lasers is suitable for graduate-level courses or as a reference for academics and professionals in optics, applied physics, and electrical engineering.