Reducing impact of cross-talk between modulators that drive a multi-channel aom

Abstract

The disclosed technology teaches a method of reducing the impact of cross-talk between transducers that drive an acousto-optic modulator. The method includes operating the transducers, which are mechanically coupled to an acousto-optic modulator medium, with different frequencies applied to adjoining transducers and producing a time-varying phase relationship between carriers on spatially adjoining modulation channels emanating from the adjoining transducers, with a frequency separation between carriers on the adjoining channels of 400 KHz to 20 MHz. The disclosed technology also includes operating 5 to 32 modulators, which are mechanically coupled to the acousto-optic modulator crystal, and varying the different frequencies applied to the modulators in a sawtooth pattern, varying the different frequencies over a range and then repeating variation over the range. Also included is varying the frequencies applied to the modulators in a rising or falling pattern applied progressively to the spatially adjoining transducers.

We claim as follows: 
     
         1 . A method of reducing impact of cross-talk between transducers that drive a multibeam acousto-optic modulator, abbreviated AOM, including:
 operating the transducers, which are coupled to an acousto-optic medium for driving separate modulation channels within the acousto-optic medium, with different single-frequency signals applied to adjoining transducers and thereby producing a time varying phase relationship between carriers on spatially adjoining modulation channels emanating from the adjoining transducers.   
     
     
         2 . The method of  claim 1 , further including operating the transducers with the single-frequency signals having differences between pairs of adjoining transducers of at least 100 KHz and a maximum difference of 20 MHz. 
     
     
         3 . The method of  claim 2 , wherein frequency differences between pairs of adjoining transducers is in a range of 400 KHz to 10 MHz. 
     
     
         4 . The method of  claim 1 , further including operating between 5 and 32 of the transducers to produce 5 to 32 modulation channels in the acousto-optic medium. 
     
     
         5 . The method of  claim 1 , wherein the different frequencies between the spatially adjoining modulation channels are arranged in a sawtooth pattern. 
     
     
         6 . The method of  claim 1 , wherein the different frequencies between the spatially adjoining modulation channels are arranged in a rising or falling pattern applied progressively to the adjoining transducers. 
     
     
         7 . The method of  claim 1 , wherein the different frequencies vary between pairs of adjoining transducers by an amount in a range of plus or minus three percent from an average frequency applied to the transducers. 
     
     
         8 . A multibeam acousto-optic modulator, abbreviated AOM, with reduced impact of cross-talk between transducers that are part of the AOM, including:
 an acousto-optic medium;   a plurality of transducers physically coupled to the acousto-optic medium, spaced apart to drive separate modulation channels within the acousto-optic medium; and   a signal synthesizer coupled to the transducers that drives the transducers at different single-frequency signals to produce a time varying phase relationship between spatially adjoining modulation channels.   
     
     
         9 . The multibeam AOM of  claim 8 , further including operating the transducers with the single-frequency signals having differences between pairs of adjoining transducers of at least 100 KHz and a maximum difference of 20 MHz. 
     
     
         10 . The multibeam AOM of  claim 9 , wherein frequency differences between pairs of adjoining transducers are in a range of 400 KHz to 10 MHz. 
     
     
         11 . The multibeam AOM of  claim 8 , further including operating between 5 and 32 of the transducers to produce 5 to 32 modulation channels in the acousto-optic medium. 
     
     
         12 . The multibeam AOM of  claim 8 , wherein the different frequencies between the spatially adjoining modulation channels are arranged in a sawtooth pattern. 
     
     
         13 . The multibeam AOM of  claim 8 , wherein the different frequencies between the spatially adjoining modulation channels are arranged in a rising or falling pattern applied progressively to the adjoining transducers. 
     
     
         14 . The multibeam AOM of  claim 8 , wherein the different frequencies vary between pairs of adjoining transducers in an amount in a range of plus or minus five percent from an average frequency applied to the transducers. 
     
     
         15 . A microlithographic laser writer comprising an AOM of  claim 8 . 
     
     
         16 . A microlithographic laser writer configured to perform the method of  claim 1 .