Technical Characterization of a High-Power Diode Laser at 445 nm for Medical Applications: From Continuous Wave Down to Pulse Durations in the µs-Range

The technical development of diode lasers with regard to wavelengths, output powers and pulse durations in the order of microseconds is expanding the range of medical applications. The 445 nm wavelength, in particular, offers a promising approach. Such a laser system is now available, and its technical and optical properties are introduced here. To characterize the diode laser with a wavelength of 445 nm, laser settings were recorded in both CW and pulse modes in the range µs to ms, with duty-cycles of 1% up to 40% (partially also up to 90%). At the same time, the temporal behaviour of the laser pulses was documented. In addition, the influence of different irradiation parameters for pulse durations of 10 µs, 100 µs and 1 ms at duty-cycles of 50%, 25% and 15% on porcine tissue was investigated. With regard to the cutting depth and thermal damage zones, cuts were carried out in the contact mode using an optical fiber with a core diameter of 375 µm and a cut speed of 3 mm/s. The average power was set between 2 W and 8 W. Output powers of up to 12.7 W in CW mode and peak powers > 30 W, with pulse durations of 5 and 10 µs, were achieved. Cuts with a depth of up to 1 mm could be created using 100 µs pulses with different duty-cycles and also in CW mode. The width of the thermal damage zone was between 200 and 350 µm for all settings. The 445 nm wavelength is characterized by a large number of possible advantages in surgical applications. Pulse durations down to the µs-range with peak power approximately three times higher than average power could open up new applications.