Method and apparatus for the spectral range enlargement of acousto-optic tunable filters

Claim 3

The method for operating an acousto-optic device according to claim 1 including the step of alternately modifying said transducer structure between the first and second degree of capacity and the fundamental and third harmonic thereof respectively, wherein the spectral range is extended from the lowest frequency in the fundamental band to the highest frequency in the third harmonic band.

Claim 4

An acousto-optic device comprising: a crystal employed as a sonic medium; a transducer structure coupled to said crystal for launching acoustic waves into said crystal, said transducer structure having a plurality of individual transducer elements with a predetermined individual capacitance; and switching means for selectively establishing electrical communication among said transducer elements; wherein for a first selected position of said switching means, said transducer structure presents a first degree of total capacitance compatible with a predetermined RF frequency and for a second selected position of said switching means, said transducer structure presents a second degree of total capacitance compatible to a third harmonic of said predetermined frequency; wherein said first selected position of said switching means aligns said transducer elements such that pairs of elements are electrically connected in parallel groups and said parallel groups are electrically connected in series, and wherein said second selected position of said switching means aligns said transducer elements in a series electrical connection, whereby the total capacitance of said transducer structure is less when said switching means is in said second position than when said switching means is in said first position.

Claim 5

An acousto-optic device comprising: a crystal employed as a sonic medium; a transducer structure coupled to said crystal for launching acoustic waves into said crystal, said transducer structure having a plurality of individual transducer elements with a predetermined individual capacitance; and switching means for selectively establishing electrical communication among said transducer elements; wherein for a first selected position of said switching means, said transducer structure presents a first degree of total capacitance compatible with a predetermined RF frequency and for a second selected position of said switching means, said transducer structure presents a second degree of total capacitance compatible to a third harmonic of said predetermined frequency; wherein said first selected position of said switching means aligns said transducer elements such that pairs of elements are electrically connected in parallel groups and said parallel groups are electrically connected in series, and wherein said second selected position of said switching means aligns said transducer elements in a series electrical connection, whereby the total capacitance of said transducer structure is less when said switching means is in said second position than when said switching means is in said first position.

Claim 6

The acousto-optic device of claim 3 including an RF source coupled to the transducer structure, said RF source selectively providing the fundamental frequency and the third harmonic thereof to said transducer structure wherein the capacitance of the transducer structure is modified by the switching means to provide effective impedance matching between said RF source and said transducer structure.

Claim 7

The acoustic-optic device of claim 4 wherein the crystal employed as a sonic medium is a crystal with the formula Tl 3 AsSe 3 .

Claim 8

The acoustic-optic device of claim 4 wherein the capacitance of the transducer structure established by the switching means in the second selected position is one-fourth the capacitance of the transducer structure established by the switching means in the first selected position and wherein the capacitance in the first selected position provides effective impedance matching with the RF source generating the fundamental frequency, and the capacitance in the second selected position provides effective impedance matching with the RF source generating the third harmonic of the fundamental frequency.