01 Abstract

During operation, when electrical energy or other forms of energy are converted into light energy in a laser, a large amount of heat is inevitably generated. If such heat cannot be dissipated timely and effectively, the temperature of the laser will rise, which will adversely affect its output power, beam quality and wavelength stability. In severe cases, the laser chip and internal optical components may even be damaged. Therefore, efficient and reliable heat dissipation is one of the key technologies to ensure stable performance and extend the service life of lasers. With the continuous increase of laser power and the expansion of application fields, heat dissipation technologies are also undergoing continuous development and innovation. This paper introduces the main heat dissipation methods for lasers and their characteristics.

02 Research Background

Year 1960–1970

In the early stage of laser development, the output power was generally low (watt level or below). Natural convection and radiation heat dissipation were mainly adopted during this period, featuring a simple and reliable structure.As the power of continuous-wave (CW) gas lasers (such as CO₂ lasers) and early solid-state lasers increased to tens of watts, simple forced air cooling was gradually applied. Fans were installed on the laser shell to remove heat through forced air convection, marking the first step of heat dissipation technology from passive to active cooling.

Year 1980–1990

Circulating water cooling systems became the standard configuration for high-power lasers in this era. Research focused on optimizing the flow channel design of cold plates, improving water quality (e.g., deionized water) to prevent scaling and corrosion, and developing high-efficiency external heat exchangers (such as cooling towers and dry coolers). Meanwhile, precision temperature control systems with compressor refrigeration were applied to temperature-sensitive semiconductor pump sources and scientific-grade lasers requiring low noise.

Year 2000 to Present

The research frontier has shifted to more efficient phase-change cooling technologies:

Spray cooling: The cooling liquid is atomized and sprayed onto the heat source surface to remove massive heat through droplet impact and latent heat of phase change; a heat dissipation capacity exceeding 1000 W/cm² has been achieved in laboratories.

Microchannel boiling cooling: Controlled phase change (boiling) of the cooling liquid is induced inside microchannels, which greatly improves the heat dissipation limit by utilizing the latent heat of vaporization.

 Laser

03 Heat Dissipation Methods

l Natural Cooling

It is the simplest and most reliable heat dissipation method, relying on natural convection and thermal radiation between the laser shell and ambient air. It requires no external power device, produces no noise and needs minimal maintenance. However, its heat dissipation capacity is limited, and it is only applicable to low-power lasers with low heat generation.

l Air Cooling

Fans force air to flow through the cooling fins or heat sinks of the laser to greatly improve heat dissipation efficiency via forced convection. With a relatively simple structure and low cost, it is suitable for medium and high-power lasers. Its disadvantages include fan noise, dust accumulation and limited fan service life.

l Water Cooling

Circulating cooling liquid (usually deionized water or a mixture of water and ethylene glycol) flows through water channels or cold plates in close contact with heat sources to carry away heat. Water cooling systems feature ultra-high heat dissipation capacity and high temperature control accuracy, which can effectively maintain stable temperature of core laser components. They are widely used in high-power and high-energy laser systems. The drawbacks are complex system composition (requiring water pumps, water tanks, pipelines and external cooling equipment such as dry coolers or cooling towers), high maintenance costs and potential water leakage risks.

l Compressor Refrigeration

Adopting the same working principle as household air conditioners and refrigerators, compressors drive refrigerant circulation to absorb heat from the laser cooling circuit in evaporators and realize active refrigeration. This method can lower the laser operating temperature below ambient temperature and provide an extremely stable low-temperature cooling environment. It is especially suitable for temperature-sensitive semiconductor lasers and application scenarios with ultra-high stability requirements. It has the most complex structure, large volume, high energy consumption and the highest cost.

Advanced Heat Dissipation Technologies

To meet the heat dissipation challenges of higher heat flux density (such as high-power semiconductor laser bars), the industry keeps exploring more efficient cooling technologies:

· Microchannel Cooling: Fluid channels with a size of tens to hundreds of microns are fabricated inside heat sinks. The cooling liquid flows in these tiny channels, achieving an ultra-high heat exchange efficiency due to the huge specific surface area.

· Spray Cooling: The cooling liquid is atomized into tiny droplets and sprayed directly on the heat source surface. Massive heat is removed through droplet impact, spreading and evaporative phase change, with heat dissipation performance far exceeding traditional convection cooling.

· Thermoelectric Cooling (Semiconductor Refrigeration): Based on the Peltier effect, direct current makes one side of the semiconductor thermopile absorb heat and the other release heat, realizing precise local active temperature control. It is commonly used for point temperature control of small-power devices.

· Phase-change Cooling: Heat is dissipated by utilizing the characteristic that materials (certain metals or fluids) absorb a large amount of latent heat during phase transition.

These advanced technologies deliver higher heat dissipation performance and a more compact structure, yet they feature complex craftsmanship and relatively high costs.

Conclusion

In summary, lasers adopt a wide range of heat dissipation solutions, forming a complete technical system from simple natural cooling to sophisticated compressor refrigeration and various advanced high-efficiency cooling technologies. In practical applications, the optimal solution shall be selected based on comprehensive consideration of the laser's power rating, structural form, performance requirements, operating environment and budget. As laser technology develops towards higher power, higher brightness and smaller size, developing more efficient, compact and reliable heat dissipation solutions will remain an important research topic in the laser industry, and a core guarantee to promote the extensive application of lasers in various fields.