Efficiency of a deep grating

A transmission grating comprising:

• a substrate comprising a first surface and a second surface;
• a grating region fixedly connected to said first surface and comprising a groove period that is less than the wavelength of a desired beam incident on said grating region, wherein said first surface is about parallel with said second surface;
• and
• a second substrate comprising an entrance surface and an exit surface, wherein said entrance surface is fixedly connected to said second surface, wherein said exit surface is angled relative to said entrance surface.

A transmission grating, comprising:

• a substrate comprising a first surface and a second surface;
• a grating region fixedly connected to said first surface and comprising a groove period that is less than the wavelength of a desired beam incident on said grating region, wherein said first surface is about parallel with said second surface;
• and
• a second substrate comprising an entrance surface and an exit surface, wherein said entrance surface is fixedly connected to said second surface, wherein said exit surface is curved.