S120vc photodiode power sensor

Nine Pentero 900 and one Kinevo 900 (Carl Zeiss AG, Oberkochen, Germany) clinical grade operating microscopes routinely used in the hospital operating rooms were assessed. Remaining bulb life time, focus distance, and light intensity settings were recorded from data displayed on the microscope work screen. Experiments were performed in darkened operating rooms. Microscopes were set up at constant distances from the target and incident light intensities were measured using a PM 200 power meter, and S120VC photodiode power sensor (ThorLabs GmbH, Dachau, Germany) calibrated for 405 nm. Optical power measurements were taken at various locations by moving the power meter probe across the round field of view of the microscope. A small aperture (6-mm diameter) was set in front of the power meter sensor to provide better granularity of the optical beam measurements. We recorded the optical power of the standard white light and the blue light in BLUE 400 mode. The zero point of the power meter was adjusted in each operating room before taking measurements to compensate for variations in ambient light.

We employed local and global illumination to stimulate the heart, whereby only global illumination was used for cardioversion. Local illumination was achieved by positioning the tip of an optical fiber of ⌀ = 400 μm in contact with the left ventricle. On the other hand, in order to achieve a consistent optogenetic stimulation of the whole heart surface and therewith global illumination, the hearts were vertically arranged surrounded by three blue-light emitting diodes (blue-LED, Thorlabs) with their wavelengths centered at 460 nm and limited by a 470 ± 20 nm bandpass filter (ET470/40x, Chroma) (see Figure 1). Synchronous millisecond control of LED at different intensities was conducted via a function generator (Arbitrary Function Generator A2230, Agilent Instruments). Intensity measurements were done using the PM100D optical power meter and the S120VC photodiode power sensor (Thorlabs). Since the experimental setup consists of three blue-LED spaced at 120°, the intensity was measured directly facing each LED from the heart position and the calculated mean was considered the overall light intensity during global illumination.
To minimize effects of potential edema as well as metabolic changes during repeated arrhythmia periods on the defibrillation success rate, we limited the experimental time to 2 h and a maximum number of defibrillation attempts of 50.