A team of researchers from the Chinese Academy of Science has developed a method for serial time-encoded amplified microscopy (STEAM), using multi-wavelength lasers to overcome the technology's main setback of requiring expensive pulsed lasers, Science China Press reports.
Conducted at the academy's Institute of Semiconductors and published in the Chinese Science Bulletin, the research describes a system that doesn't need a broadband coherent laser light source for real-time optical imaging. Instead, it uses mutually phase-uncorrelated lasing lines that help avoid the limitations of the measurement range and the imaging frame rate.
Because the multi-wavelength laser's output is controllable, the system's measurement range can be extended by simply increasing the number of wavelengths. While a frame-rate of 250 MHz was obtained in the experiment, this component is also subject to reconfiguration by electrically tuning the gating rate.
STEAM techniques for ultra-fast real-time optical imaging are based on a combination of space-frequency mapping combined and frequency-time mapping. Introduced relatively recently, they have been demonstrated as a completely new optical imaging modality.
Until the Chinese team's recent discovery, led by professor LI Ming, these methods required a large and high-cost pulsed laser, which imposed a number of limitations on the technology. For example, its measurement range was limited by the laser's spectral width of ten nanometers. The imaging frame rate was also limited to the same value as the laser's pulse repetition rate - usually, just dozens of MHz.
The new development with multi-wavelength lasers can greatly reduce the cost of STEAM systems, the researchers claim. The prospect of integrating such lasers into photonic chips could further contribute to that effect in the future, as well as reducing the systems' size.