There are literally more than 10,000 types of lasers developed to date. Most of them are developed only in a laboratory, but some have found very broad applications.
Table of Contents
Fiber Lasers and Pumping Technologies
Fiber lasers are an interesting class of solid-state lasers. Active media are the core of rare-earth (Er, Yb, etc.) doped fiber. Pump light can be in the core or the cladding. Fiber lasers can be very compact and rugged. They are becoming very popular with the advent of suitable diode pumps. Since the fiber core is very small, the threshold pump power is a few orders of magnitude less as compared to the bulk case. Since core-pumping requires high spatial quality lasers, diode bars and arrays cannot be used. This limits the pump power. To resolve this problem, high-power fiber lasers use pumping from the cladding of the fiber. Cladding pumped Nd and Yb doped fiber can yield ~10 W output power.
Single-Frequency Lasers for Precision Applications
Single-frequency sources are also attractive because they can be used for driving resonant enhancement cavities, e.g., for nonlinear frequency conversion, and for coherent beam combining. Typical applications of single-frequency lasers occur in the areas of optical metrology and interferometry, optical data storage, high-resolution spectroscopy (e.g., LIDAR), and optical fiber communications. In some cases, such as spectroscopy, the narrow spectral width of the output is directly important. In other cases, such as optical data storage, a low-intensity noise is required, thus the absence of any mode beating noise.
Ultrafast Lasers in Advanced Materials Processing
The unique characteristics of ultrafast lasers, such as picosecond and femtosecond lasers, have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities. Thus, ultrafast lasers are currently used widely for both fundamental research and practical applications. Surface processing includes micromachining, micro- and nanostructuring, and nano-ablation, while volume processing includes two-photon polymerization and three-dimensional (3D) processing within transparent materials.
Tunable wavelength laser arrays find wide applications in fiber-optic networks, broadband sensors, biotechnology, and medical diagnostics due to their wide tuning range and stable lasing operation.
CO₂ Lasers for High-Power Industrial Use
CO2 laser is one of the most powerful. It is used very commonly for «hardcore» materials processing, like cutting and welding. Lasing action results from transitions between vibrational levels of CO2. These lasers are typically RF discharge-pumped. They can operate pulsed or CW. They are mostly used in industry and medicine, where high powers are needed.
Gas lasers, laser diodes, and solid-state lasers can be manufactured to emit ultraviolet rays, and lasers are available that cover the entire UV range. The strongest ultraviolet lines are at 337.1 nm and 357.6 nm, wavelength. Ultraviolet lasers have applications in industry (laser engraving), medicine (dermatology and keratectomy), chemistry (MALDI), free air secure communications, computing (optical storage), and the manufacture of integrated circuits.
Tunable Solid-State and Dye Lasers
Ti:Sapphire is the most widely used tunable and mode-locked solid-state laser. It has a bandwidth of about 400 nm, centered at 800 nm. Emissions result from 3d transitions. No diodes are available at this wavelength. This is the main drawback of Ti:Sapphire. Dye lasers use solutions of organic dyes as active media. Solvents can be alcohol, glycerol, or water. Due to the large wavelength range, dye lasers are used in many scientific spectroscopic applications. They are also used in medicine for retinopathy and curing dermatological diseases.