On the possible ultrasonic inspection of micro-bubbles generated by the optical fiber tip

Abstract

We demonstrate the possibility of detection and monitoring of bubbles emerging near the tip of an optical fiber by means of ultrasonic method. The excitation of bubbles at their resonant frequencies is performed using short ultrasonic pulses having a wide frequency range simultaneously with their modulation by means of a long pulse of a monochromatic frequency. This method allows detection of bubbles of various sizes. Used signal processing method, which allows increased bubble detection accuracy, is proposed for research in environments of biological-like medium which show continuous variations in structure and properties when exposed to optical emission. The method has been demonstrated on model objects: in a liquid and in a biological tissue phantom using various methods of bubble generation (hydrolysis and optical emission). We studied bubble formation by the tip of a fiber of the surgical laser LSP-007/10 “IRE Polus” with a wavelength of 0.97μm coated with a highly absorbing graphite layer.

Keywords

• Bubble generation
• ultrasonic inspection of bubbles
• subharmonic ultrasound modulation
• laser surgery