An electronically tuneable light source includes a source (10) of white light, an acousto-optic modulator (16) which includes a transparent medium and means (17) for generating an acoustical wave in the medium, and means for directing the collimated beam of the white light onto the medium at a preselected angle θ/2 to a line which is perpendicular to the direction of travel of the acoustical wave. Interaction of the light beam with the acoustical wave causes diffraction of the light beam. Means (22) are provided for selecting a visible band of the diffracted beam at an angle to the incident collimated beam of light equal to approximately 8.

Electronically tuneable light source

An acousto-optic tunable filter ("AOTF") with a pair of electrodes on opposite sides of the waveguide. A voltage source applies a potential across the electrodes, thereby creating an electric field through the waveguide. The electric field controls an optical property of the waveguide by altering the birefringence of the waveguide. Suitably adjusting the potential applied by the voltage source results in suppression of sidelobes, correction of asymmetric sidelobes, and compensation for physical variations in the waveguide. The AOTF can be tuned very rapidly by a tuning voltage applied to the electrodes. In combination with a thermistor, the control voltage can compensate for changes in temperature. A spatially-varying electric field is generated by using a set of electrodes at different potentials, or by using a resistive element as an electrode, or by shaping the electrodes according to the desired field. A rapidly-varying control voltage can modulate a light beam in the filter. The AOTF finds an application as the tuning element of an external-cavity tunable laser.

Controllable-birefringence, acousto-optic tunable filter and a laser tuned by the same

There is provided a chip for use in a combination microbalance and optical monitor sensor, the chip comprising a piezoelectric element and electrodes formed on a first surface thereof. At least a portion of the piezoelectric element is translucent. There is also provided a chip comprising a piezoelectric element and electrodes in contact with the piezoelectric element, at least a portion of at least the first electrode being translucent, and at least a portion of the piezoelectric element being translucent. Current can be applied through the electrodes to cause a region of the piezoelectric element to undergo vibration, and light can be passed through a portion of the region of the piezoelectric element which is undergoing the vibration. There is also provided a combination microbalance and optical monitor sensor, comprising a chip as described herein, and a method of simultaneously piezoelectric crystal vibration monitoring and optically monitoring a layer.

Method and apparatus for measuring and monitoring coatings

A method for increasing the tunable range of a single acousto-optic tunable filter includes the steps of generating an active steering beam on a piezoelectric transducer and configuring the electrodes of the piezoelectric transducer to reduce the tuning frequency at short wavelengths and increasing the tuning frequency at long wavelengths. The piezoelectric transducer is mounted in relation with an optically transparent crystal at an angle such that the fixed launch angle in combination with the driving frequency provides a greater that one octave spectra to be filtered in a single AOTF.

Octave spectra acousto-optic tuneable filter

A microwave oscillator circuit having a voltage controlled oscillator for producing a controllable frequency microwave signal and a high overtone bulk acoustic resonator coupled to receive the signal is provided with a light source for directing a light beam onto the resonator such that the light is diffracted in response to the presence of acoustic waves produced in the resonator by the microwave signal. Diffracted and undiffracted portions of the light beam are measured and compared to provide an indication of resonance phenomena within the high overtone bulk acoustic resonator. This technique is particularly applicable to frequency agile stable local oscillators in radar equipment. Optical data extraction is completely non-invasive with respect to the microwave circuit functions, resulting in unimpaired stable local oscillator operation.

Microwave oscillator with optical readout of resonance phenomena

An acousto-optic light filter is disclosed wherein a radio frequency electric field is employed to excite an acoustic wave in a piezoelectric optically anisotropic medium. The light to be filtered is collinearly diffracted on the acoustic wave to shift light of a first polarization and of a frequency related to the frequency of the acoustic wave, into light of a second polarization. The diffracted light is polarization analyzed to separate light of the second polarization from light of the first polarization. Piezoelectric birefringent crystals are employed for the optically anisotropic medium. Arrays of acoustic resonators are formed by energy trapping in crystalline slabs, such resonators being selectively addressed by applying electric fields to the crystalline slab at the resonant frequency of the selected acoustic resonator. Different overtone resonances of the acoustic resonators are excited to permit the filter to pass light of different frequencies either in time displaced intervals or simultaneously.

Hammond Donald L

Papers

Resonant piezoelectric acousto-optic light filter and apparatus using same