Preface

The laser has become more and more important in scientific research and industrial applica‐ tions with the merits of excellent monochromaticity, coherence, and directivity. Now, the laser wavelength can cover the range from ultraviolet to terahertz and output laser perform‐ ance has significantly progressed in recent years. Therefore, due to the characteristics of non-invasiveness and high-power intensity, applications based on laser techniques have be‐ come more extensive. The aim of this book is to introduce and present the latest advance‐ ments in the field of laser techniques and their applications.

In this book, two chapters are focused on the advanced diode laser and fiber laser. A highpower tunable GaN diode laser using external-cavity configuration with emission in the visible spectral range is shown first. Subsequently, a thulium–ytterbium short pulse fiber laser by cladding pumping is reported. In the application section, there are four chapters on laser ablation, laser-introduced fluorescence, laser treatment, and nonlinear optical response of nanoparticles.

> **Yufei Ma** Harbin Institute of Technology China

**Section 1**

**Laser Technology**

**Section 1**

**Laser Technology**

**Chapter 1**

**Provisional chapter**

**Tunable High-Power External-Cavity GaN Diode Laser**

**Tunable High-Power External-Cavity GaN Diode Laser** 

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 knowl-

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.79703

**Systems in the Visible Spectral Range**

**Systems in the Visible Spectral Range**

Anders Kragh Hansen and Paul Michael Petersen

edge, in a BAL with an external-cavity grating feedback.

**Keywords:** diode lasers, GaN, external cavity, tunable, instabilities and chaos

Since the first demonstration of a room temperature continuous wave (CW) GaN violet diode laser by Nakamura et al. [1], great progress has been achieved on the GaN-based diode lasers in the violet to green spectral range. Nowadays, high-power GaN diode lasers with CW output power of a few watts are commercially available in the blue to green spectral range [2].

Anders Kragh Hansen and Paul Michael Petersen

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Mingjun Chi, Ole Bjarlin Jensen,

Mingjun Chi, Ole Bjarlin Jensen,

http://dx.doi.org/10.5772/intechopen.79703

**Abstract**

**1. Introduction**

#### **Tunable High-Power External-Cavity GaN Diode Laser Systems in the Visible Spectral Range Tunable High-Power External-Cavity GaN Diode Laser Systems in the Visible Spectral Range**

DOI: 10.5772/intechopen.79703

Mingjun Chi, Ole Bjarlin Jensen, Anders Kragh Hansen and Paul Michael Petersen Mingjun Chi, Ole Bjarlin Jensen, Anders Kragh Hansen and Paul Michael Petersen

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.79703

#### **Abstract**

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.

**Keywords:** diode lasers, GaN, external cavity, tunable, instabilities and chaos
