Pulse profile registration using self-mixing in a diode laser

An arterial pulse profile was registered using an optical self-mixing in a diode laser. This system was able to detect pulsation profiles of major arteries with potentially useful information including pulse wave velocity and profile of pulse pressure. The basis of the registration was the self-mixing that occurred in the diode laser cavity when the radiation scattered back by the skin into the laser interfered with the field inside it and caused a change of laser pump current. The self-mixing signal was extracted by two different ways simultaneously: with using a photodiode accommodated in the rear facet of the diode laser package and normally used for monitoring of the laser power and with a help of small resistance resistor from the laser pump current. The described self-mixing method has the same sensitivity but the significant advantages of simplicity, compactness, and robustness as well as the self-aligning and self-detecting abilities when compared with the use of conventional interference methods.