I have also looked at c# 3.0 - Disable and then re-enable Symbol Barcode Scanner - Stack Overflow
But it turns off the listener. Not turn off the laser. Data Wedge API does that , but symbol.barcode.Reader seems to overrode that. I have a MC67. Symbol.barcode2.dll might have more controls? but I can't seem to get the sample project to read the list of supported devices on my MC67.
If you have a read triggered, you would probably need to do a flush on the reader (pasting in below from the help file).
// Flush (Cancel all pending reads)
Look at StopRead() in api.cs in the sample app.
Also, if you are using the EMDK, you need to disable Datawedge. Datawedge will conflict with your EMDK application. Either Datawedge or an EMDK app can access the scanner, but both cannot access it at the same time. You might actually be seeing DataWedge lighting up the scanner, not your app.