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Lasers have transformed numerous industries with their unique capabilities and precise control of light. However, different types of lasers offer distinct advantages and disadvantages, making them suitable for specific applications. In this article, we will explore the advantages, disadvantages, and applications of various laser types, enabling a better understanding of their strengths and limitations.

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The authors acknowledge collaborations with colleagues at Princeton University and associated with the NSF Engineering Research Center MIRTHE. A.J.H. thanks S. Howard for valuable discussions. They also acknowledge partial support by MIRTHE (NSF-ERC) and DTRA.

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Limited Wavelength Versatility: Solid-state lasers have limitations in terms of available wavelengths compared to other laser types, which can restrict their applicability in certain applications.

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Each type of laser offers its own set of advantages, disadvantages, and applications, making it important to carefully consider the requirements of a specific application. Solid-state lasers provide high power and precise beam quality, gas lasers offer versatility in wavelength and high power, semiconductor lasers are compact and efficient, and fiber lasers combine high power scalability with excellent beam quality. Understanding the strengths and limitations of different laser types is key to selecting the most appropriate laser for a given application, ensuring optimal performance and successful outcomes.

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Cooling Requirements: Due to their high power output, solid-state lasers may require cooling systems to manage heat dissipation, increasing complexity and cost.

The design flexibility of quantum cascade lasers has enabled their expansion into mid-infrared wavelengths of 3–25 μm. This Review focuses on the two major areas of recent improvement: power and power efficiency, and spectral performance.

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Mid-infrared quantum cascade lasers are semiconductor injection lasers whose active core implements a multiple-quantum-well structure. Relying on a designed staircase of intersubband transitions allows free choice of emission wavelength and, in contrast with diode lasers, a low transparency point that is similar to a classical, atomic four-level laser system. In recent years, this design flexibility has expanded the achievable wavelength range of quantum cascade lasers to ∼3–25 μm and the terahertz regime, and provided exemplary improvements in overall performance. Quantum cascade lasers are rapidly becoming practical mid-infrared sources for a variety of applications such as trace-chemical sensing, health monitoring and infrared countermeasures. In this Review we focus on the two major areas of recent improvement: power and power efficiency, and spectral performance.

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Higher Cost: Solid-state lasers tend to have higher initial costs compared to some other laser types, making them less accessible for certain applications.

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