A fiber-optic liquid-level sensor based on the bending of a fiber Bragg grating (FBG) is proposed. The FBG embedded in a cantilever rod such that the elongation and contraction of the Bragg grating indicate a liquid-level change. The shift in the Bragg wavelength has a good linear response to the bending of the cantilever. An optical bandpass filter is used to determine the Bragg wavelength by converting the wavelength shift to an intensity demodulation. The relative power measured by a photo-detector is also linearly proportional to the liquid-level variation. The sensitivity is approximately 0.1 dB/cm. To eliminate the temperature dependence of the FBG sensor, we suggest that the tuning of the optical bandpass filter should take into account the temperature variation. The operating principle is described in detail.

Liquid-level monitoring sensor systems using fiber Bragg grating embedded in cantilever

An optically pumped mid-infrared solid-state laser with high pulse repetition rate is described for use in laser surgery. The laser produces a wavelength between 1.7 and 4.0 microns, and is optically pumped. The rise and fall times of the pump pulses are sufficiently short to avoid thermal lensing induced instability. The laser provides an increased rate of tissue cutting without necessitating an increase in the pulse energy.

High repetition rate mid-infrared laser

Efficient pulsed room-temperature laser emission at 946 nm is obtained from a Nd:YAG rod pumped by a Ti-doped sapphire laser in the free-running mode Three bonded YAG rods of 3-mm diameter with different Nd concentrations and active lengths were tested A maximum output energy of 835 mJ at 3 Hz was obtained with a slope efficiency of 323% in an end-pumping configuration

Efficient pulsed 946-nm laser emission from Nd:YAG pumped by a titanium-doped sapphire laser

A narrow-linewidth, Q-switched, tunable Ti:Al2O3 laser, which is pumped by short-pulse flashlamps is developed using self-injection locking. By electro-optically switching the light from a second resonator consisting of a grazing incidence grating and a tuning mirror, which generates a narrow-linewidth seed pulse, to a conventional main resonator with a large volume, output energies of up to ~57 mJ/pulse were obtained with a linewidth of ~10 pm and a pulsewidth of ~20 ns. The laser was tunable within a range of 760 nm to 830 nm with high spectral purity.

Self-injection-locked, narrow-linewidth, flashlamp-pumped Ti: Al2O3 laser

Artificial neural network-based modeling of flashlamp characteristics

In this work, we attempted to optimize the flashlamp pumping of a titanium-doped sapphire rod. The dimensions of this rod are 8 mm diameter by 152.4 mm (6 inches) length. First, we realized a fast discharge circuit (2 μs FWHM) with six flashlamps. Afterwards, we used a four-flashlamp system with an enlarged discharge being shaped by a PFN (Pulse Forming Network). The first set-up yielded 530 mJ of output energy with an electrical-to-optical efficiency of 0.265%, whereas the second set-up yielded 3 J with an efficiency of 0.8% in the relaxed mode centred at 782 nm.

Y. Lutz

Papers

Optimization of the excitation characteristics of a flashlamp-pumped titanium sapphire laser