Using sophisticated technology, the TETRA laser can switch from pulse to pulse between these four wavelengths with a very high pulse repetition frequency of 2kHz. The production-ready DPSS laser model, TETRA, uses the Raman effect and the light of a 532nm pump laser to also emit at 555nm, 579nm and 606nm. A tunable optical filter separates the four wavelengths and routes one wavelength at a time to the optical output of the unit at a switching frequency of up to 2kHz. This makes TETRA about ten times faster than tunable lasers based on OPOs (Optical Parametric Oscillators), claims the manufacturer. The laser consists of two separate units: one box contains the electronics for the entire power supply and incorporates the pump laser diode. The output of this laser diode is coupled via an optical fiber to the second case, which contains the actual laser head. This design means the thermal loss of the electronics and the pump diode is only dissipated in the power supply unit, which reduces thermal loading of the laser head. When used for multispectral photo-acoustic tomography, during a scan of biological tissue, the absorption of four different wavelengths can now be measured quasi-simultaneously at each individual pixel at a comparable frame rate of single wavelength alternatives. This avoids artifacts that can occur with multiple sequential complete scans with one wavelength each.
AMS Technologies – www.amstechnologies.com