Helium cadmium (HeCd) lasers have long been a staple in various scientific and industrial applications, prized for their precise wavelengths and stable output. However, recent regulatory changes in the European Union (EU) have impacted their availability, prompting the need for alternatives.

What are Helium Cadmium lasers?

A helium cadmium (HeCd) laser utilises a gas mixture of helium and cadmium to produce laser light. These lasers typically have good beam characteristics with stable output and operate at distinct wavelengths, most commonly in the ultraviolet (325 nm) and blue (442 nm) regions.  They are an important light source in the ultraviolet and visible spectrum and are uniquely useful in many applications including holography, biomedical imaging and spectroscopy.

Despite these advantages, HeCd lasers (along with other gas lasers) have certain drawbacks. By being a gas laser, this means that the lasing medium is enclosed in a plasma tube and as a result the lifetime and efficiency are typically limited. In recent years safety concerns, as well as advancements in other types of laser technologies, have begun to impact their usage in the future.

The European Union bans Cadmium

The rise in the production and use of electrical and electronic products, such as mobile phones, computers and kitchen appliances, has resulted in an increasing volume of electrical and electronic waste. To address such challenges, in 2019 the European Commission passed a law to restrict the use of certain hazardous substances through the RoHS Directive (Restriction of Hazardous Substances).

Cadmium is one of six hazardous substances banned from use in Europe in electrical and electronic equipment by the RoHS directive, which was designed to protect human and environmental health. The six banned hazardous substances are the heavy metals lead, cadmium, mercury, and hexavalent chromium, as well as two groups of brominated flame retardants, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE).

Alternatives to Helium Cadmium lasers

Thankfully there are alternatives to HeCd lasers. The availability of lasers with wavelengths based on diode pumped laser (DPL) technology has expanded hugely in the past two decades, this includes in the UV regions covered by HeCd lasers (325 nm and 442nm). The advantages of diode pumped lasers is that they are based on solid state gain medium (crystal) instead of a gas. As a result, the lifetime and efficiency of solid state lasers far surpasses that of gas lasers.

At HÜBNER Photonics we specialize in diode-pumped solid-state (DPSS) lasers, or otherwise known as Diode-Pumped Lasers (DPL) as well as other types of solid state lasers such as diode lasers. Our DPLs are based on intra-cavity nonlinear frequency conversion and deliver high optical powers in a perfect TEM00 beam and are inherently single longitudinal mode (SLM) by design. The perfect replacement for the 325 nm HeCd is the Cobolt Zydeco 320 nm diode pumped laser. If you need a filter especially for 320 nm, we suggest Idex Semrock filters.

Exploring DPSS lasers

A typical diode pumped laser consists of a pump diode, a solid-state gain medium or laser crystal, and a non-linear optical element. Additionally, some DPSS lasers contain mode suppressing elements and beam shaping optics as seen in the figure below.

The broad wavelength coverage, long–coherence lengths, perfect beams, excellent spectral purity and wavelength stability, delivered with stable and reliable performance, make these lasers very suitable for demanding applications not only for advanced laboratory research but also for integration into analytical instrumentation in applications such as in Raman spectroscopy, bioimaging, interferometry, holography and quantum technology research.

Whether you’re a researcher pushing the boundaries of science or a business seeking to enhance your manufacturing processes, DPSS lasers can provide the performance and efficiency you need.

Conclusions

While Helium Cadmium lasers offer distinct advantages in terms of specific wavelength production, high beam quality, and stable output, they also come with significant drawbacks, including regulatory restrictions. As a result, many users are transitioning to alternative laser technologies that provide similar or improved performance without the associated health and environmental risks. Diode lasers, with their excellent spectral purity and wavelength stability are positioned to be the ideal alternative to HeCd lasers.