Cochlear stimulation was achieved with diode lasers (Lockheed Martin Aculight Corp., Bothell, WA) coupled to the optical fibers (P200-5-VIS-NIR, Ocean Optics Inc., Dunedin, FL) with core diameters of 200 μm (Fig. 1A,B ). The radiation wavelength was 1862 nm and the pulse duration was 50 or 100 μs. The radiant energy at the tip of the optical fiber was calibrated in air prior to the experiments and was between 0 and 127 μJ/pulse. Pulses were presented either as single events at 2–5 Hz, or at a 250 Hz repetition rate in pulse trains of 300 ms duration. For each data point 10 pulse trains were averaged.
The energy E at the modiolus was calculated with the following equation: E = Eo * e−μd, where E0 denotes the energy per pulse at the tip of the optical fiber, μ the extinction coefficient, and d the distance between the optical fiber and the modiolus that was determined from the microCT scans (see below). From the radiant energy the peak power was calculated by dividing the E by the pulse duration. The radiant exposure was calculated by dividing E by the spot size. The spot size was calculated by using the core diameter of the optical fiber dfiber, and the spread of the radiation in water as determined in previous experiments r = d × tan α13 (link), where α is the angle by which the radiation beams spreads. The radius R for the spot was calculated as .
The energy E at the modiolus was calculated with the following equation: E = Eo * e−μd, where E0 denotes the energy per pulse at the tip of the optical fiber, μ the extinction coefficient, and d the distance between the optical fiber and the modiolus that was determined from the microCT scans (see below). From the radiant energy the peak power was calculated by dividing the E by the pulse duration. The radiant exposure was calculated by dividing E by the spot size. The spot size was calculated by using the core diameter of the optical fiber dfiber, and the spread of the radiation in water as determined in previous experiments r = d × tan α13 (link), where α is the angle by which the radiation beams spreads. The radius R for the spot was calculated as .