According to a study published in the latest issue of the journal Optics, scientists at the Swiss Federal Institute of Technology in Zurich have developed a new laser oscillator that produces a laser that sets a new record for such laser pulses in terms of average power and intensity. The average power was 550 watts, exceeding the previous record by more than 50 percent.
The laser pulses lasted less than a picosecond and came out of the laser in an orderly fashion at a very high rate of 5 million pulses per second. These ultra-powerful laser pulses with ultra-short "lifetimes" can be used in many fields, such as materials processing, eye surgery, precision measurements, etc., and are also expected to give rise to more accurate atomic clocks.
Wei Zhiyi, a researcher and doctoral supervisor at the Institute of Physics of the Chinese Academy of Sciences, explained to the Science and Technology Daily reporter that in order to create these ultra-short strong laser pulses, the team used a "disk" laser oscillator. The core component of the oscillator is a thin disk just 100 micrometers thick, made up of crystals doped with ytterbium atoms.
The latest research is based on two technological innovations: the first is the use of a unique arrangement of mirrors to amplify the oscillating light inside the laser cavity. To do this, the team cleverly designed a special array of mirrors that amplify the light as it travels back and forth through the laser cavity. Then, in order to convert this amplified light into high-intensity ultrashort pulses, the team used "semiconductor saturable absorber mirrors (SESAM)". Unlike ordinary mirrors, the reflectivity of a SESAM varies with the intensity of the light. When the intensity of light exceeds a certain threshold, the SESAM reflects the light efficiently, switching the laser from continuous mode to pulsed mode.
The team expects to be able to further compress that pulse into the less-cycle range, which is crucial for generating attosecond pulses. The attosecond pulses could help scientists take a deeper look at ultrafast physical phenomena within matter, further revealing the hidden mysteries of the microscopic world.
