Laser technology has made significant strides over the years, commonly associated with a steady beam of concentrated light. However, its applications extend beyond this simplistic perception. In both scientific research and industrial applications, there exists a growing demand for extremely short and powerful pulses of laser light. These pulses, lasting mere femtoseconds (one quadrillionth of a second), have transformative capabilities; they can manipulate materials at unprecedented speeds and generate X-rays that allow researchers to observe ultra-fast processes in real-time.
Recently, an innovative team at ETH Zurich, led by prominent physicist Ursula Keller, has made groundbreaking advancements in this realm, specifically focusing on the generation of exceptionally strong laser pulses. Their research culminated in a new record: an astounding average power of 550 watts, surpassing earlier achievements by over 50%. This extraordinary feat positions their laser pulses as the strongest produced by a laser oscillator to date, highlighting the potential for broader applications in both science and industry.
The crucial technological advancements responsible for this leap in laser pulse strength and efficiency stem from an ongoing commitment to innovation and problem-solving within Keller’s research group. The essence of their achievement lies in generating remarkably short pulses, lasting under a picosecond, and achieving a remarkable repetition rate of five million pulses per second. At peak performance, these pulses are said to reach powers equivalent to 100 megawatts—an astounding output capable of briefly powering an entire fleet of vacuum cleaners.
In the quest to refine short pulsed disk lasers, Keller and her team have dedicated 25 years to meticulously navigating the challenges and intricacies involved in this specialized field. The construction of these lasers employs a thin disk of crystal, merely 100 micrometers thick, infused with ytterbium atoms, which serves as the laser material. However, numerous obstacles have emerged throughout this research journey, often resulting in significant equipment failures and necessitating creative solutions to troubleshoot and enhance performance.
The key advancements leading to the recent breakthroughs can be attributed to two primary innovations. First, the researchers utilized an intricate arrangement of mirrors that recirculate light within the laser multiple times before it exits through an outcoupling mirror. This clever design not only amplifies the light significantly but also ensures that the laser remains stable throughout the process.
Second, the heart of their pulsed laser technology is rooted in the utilization of a semiconductor mirror known as SESAM (Semiconductor Saturable Absorber Mirror). Unlike traditional mirrors that maintain a consistent reflectivity, SESAM mirrors dynamically adjust their reflective qualities based on the intensity of light that confronts them. The incorporation of this technology enables the researchers to unleash short bursts of laser light, further concentrating energy and enhancing intensity.
As Dr. Moritz Seidel, a Ph.D. student and a key member of Keller’s laboratory, explains, the innovative design of SESAM facilitates the automatic transition of the laser into a pulsed mode under high light intensity conditions. This is a significant improvement over previous methods that required external amplifiers, which inherently introduced noise and reduced precision in applications requiring exact measurements.
The newfound capability to generate powerful, short laser pulses presents a wealth of potential applications. Keller’s research team anticipates not only enhancing existing technologies but also paving the way for emerging fields such as frequency combs that operate within the ultraviolet to X-ray spectrum. These developments could lead to the creation of highly precise atomic clocks, advancing our understanding of fundamental physical properties.
Keller also expressed optimism surrounding terahertz radiation generated from their advanced laser systems, suggesting applications in material testing across various scientific disciplines. This multifaceted utility of the new technology reinforces the idea that laser oscillators are an excellent alternative to traditional amplifier-based systems, providing heightened precision in both experimental and practical applications.
As the field of laser technology continues to grow in sophistication, the possibilities for future advancements seem limitless. Ursula Keller’s team at ETH Zurich not only sets a new benchmark in pulse generation but also embodies the spirit of inquiry that drives scientific progress. With aspirations that include exploring the constancy of natural constants and achieving groundbreaking insights in material science, the advancements in laser pulse technology serve as a catalyst for innovation and discovery in our understanding of the universe. The implications of this research resonate far beyond laboratory confines, hinting at transformative changes to come in technology and science alike.