When it comes to the outstanding performance of 308nm excimer lasers in dermatological treatments—such as vitiligo and psoriasis—or in high‑precision industrial machining, we often focus on their precise energy delivery and remarkable efficacy. But what is the “heart” that powers this sophisticated device to emit that specific ultraviolet light?

The answer lies in its core consumable—specialized mixed gases.

Xenon chloride (XeCl) excimer lasers are continuous pulsed gas lasers with wavelengths in the UVB range, typically featuring pulse durations of around 10–30 ns. Clinically used laser emitters include the Xtrac (PhotoMedex, USA) [4–6], the Lambda Physics LPX105E [2, 3, 7, 8], and other types of emitters [9]. These systems often incorporate an XeCl gas discharge tube. Since the XeCl dimer is composed of the inert gas xenon—whose outermost shell contains 8 electrons—and the halogen chlorine—whose outermost shell contains 7 electrons—it exists in a bound state when energized by an electric current, emitting pulsed laser radiation. While the parameters of different laser emitters vary slightly, take the Xtrac AL7000 as an example: it emits a 308 nm laser with a pulse width of 30 ns, a repetition rate of 154 Hz, and a single-pulse energy density of 2–3 mJ/cm². The laser is transmitted via a liquid light guide fiber, producing a square spot measuring 2 cm × 2 cm. During treatment, the spot size can be adjusted as needed, or an appropriate dose can be selected to achieve optimal therapeutic outcomes.

1. Why Are Mixed Gases Necessary? — The Principle Behind Laser Generation

The 308nm excimer laser gets its name because its active medium is an “excimer,” which specifically refers to unstable molecules that briefly bond in an excited state and rapidly dissociate in the ground state.

For a wavelength of 308 nm, the key excimer is XeCl (xenon chloride), which is formed when a xenon atom and a chlorine atom temporarily bond under the excitation of a high‑voltage electrical discharge. This “excited” XeCl* molecule is extremely unstable; it rapidly transitions back to its ground state and releases a quantum of energy—in other words, a photon with a wavelength of 308 nanometers.

However, xenon and chlorine cannot directly and efficiently carry out this process. This is where a third gas—typically neon as a buffer gas—comes into play. Consequently, the working gas of a 308 nm excimer laser is a “cocktail” composed of these three gases mixed in precise proportions.

2. As a “consumable,” its lifespan is tied to replacement.

Why is this gas considered a “consumable”?

During laser operation, each discharge consumes an extremely small amount of xenon and chlorine gas. More critically, the gas composition undergoes subtle physicochemical reactions with the electrodes and the inner walls of the cavity, leading to gas contamination and imbalances in the gas mixture ratios. This gradual “degradation” process causes the laser’s output energy to decline steadily, its wavelength to become unstable, and ultimately renders it unable to meet the requirements of medical or industrial applications.

Therefore, just as a car needs regular refueling and maintenance, a 308nm excimer laser also requires periodic replacement of gas cylinders (also known as “gas tanks”) to ensure that laser performance remains at its optimal level at all times. The gas lifetime of modern lasers typically reaches tens of millions of pulses, but the specific replacement interval should be determined based on actual usage frequency and performance monitoring results.

Important Note: Due to the corrosive and toxic nature of chlorine gas, the filling, replacement, and disposal of used cylinders must be carried out strictly in accordance with safety procedures by professionally trained personnel to ensure the safety of both personnel and equipment.

3. Summary: The Importance of Choosing High‑Quality Mixed Gases

A high‑performance 308 nm excimer laser relies not only on precise optical and circuit design, but also on stable, pure mixed gases with exact proportions. High‑quality mixed gases can deliver to you:

• Stable output power: Ensures consistent and reliable treatment or processing results.

• Long service life: Reduces replacement frequency, lowering long‑term operating costs and downtime.

• Equipment Protection: High‑purity gases can effectively reduce corrosion of the laser’s internal cavity and electrodes, thereby extending the service life of core equipment.

Therefore, choosing a mixed gas supplier with stringent quality control, extensive experience, and comprehensive services is a crucial step in ensuring the efficient and stable operation of your laser equipment.

Friendly Reminder: The information above is for educational purposes only. For specific gas specifications, replacement cycles, and safe operating procedures, be sure to follow the official guidelines and recommendations provided by the manufacturer of the laser you are using.