From arns@KOSI.com Tue Oct 16 19:12:58 2007 Date: Tue, 16 Oct 2007 13:13:17 -0400 From: J. Arns To: Vik Dhillon Subject: NSF66 Prisms Vic, I have been working on getting the prisms and in the process reviewed the Schott data sheet for NSF66 optical glass. See the attachments showing the proposed grism and the internal transmittance of the prism glass. As you can see for the wavelengths of coverage of the 1557 l/mm, blue grism the internal transmittance will cause significant losses from about 85% to about 63% from 516 to 434 nm respectively (if the prism material traversed was a uniform 25 mm thick). Additionally there will be a throughput gradient from the narrow side of the grism to the thick side of the grism simply due to the changing thickness. I had not taken this into consideration when calculating the grism performance as the materials I have used in the past have been sufficiently transparent as to be neglected. This is not the case for using NSF66 in this wavelength range. Perhaps you have considered this? Would you like me to proceed based on using NSF66 for both grisms or would you like to suggest an alternative? Regards, Jim Arns [ Part 2, Application/OCTET-STREAM (Name: "VPH-PP-1070-656 ] [ Drawing.pdf") 61KB. ] [ Unable to print this part. ] [ Part 3, Application/OCTET-STREAM (Name: "NSF66 ] [ Transmittance.pdf") 34KB. ] [ Unable to print this part. ]