Holographic grating - can we calculate efficiency for each order?

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Discussion Overview

The discussion focuses on the efficiency of holographic gratings and how the angle of incidence affects the power distribution among different diffraction orders. Participants explore theoretical aspects, practical implications, and specific cases related to grating efficiency.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant models diffraction angles for various orders and queries how the angle of incidence impacts the power in each order, suggesting that the n=+1 order may be the most efficient.
  • Another participant notes that grating efficiency is influenced by incident polarization and groove shape, indicating a lack of a universal analytic theory for efficiency calculations.
  • A later reply mentions that certain volume phase gratings may only allow one order to exist due to higher orders having diffraction angles exceeding 90 degrees.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the dependence of efficiency on the angle of incidence and the factors influencing grating efficiency. Multiple competing views on the topic remain, and the discussion is unresolved.

Contextual Notes

Participants reference specific literature and examples, indicating limitations in their understanding of the underlying principles governing grating efficiency and the conditions under which certain orders may not exist.

Turksen
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Hi,

I'm new to working with gratings. From using the basic grating eqn., I'm able to model the diffraction angles for each order with different angles of incidence upon the grating and I can calculate the dispersion given a broadband source with known minimum and maximum wavelength.

However, I'm unsure how the angle of incidence affects the power going into each order. I think the n=+1 order is usually the most efficient, although is there a dependence upon the incidence angle / diffraction angle for efficiency?

Thanks
 
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In the case of some volume phase gratings I've seen, the shape of the grating only allows one order to exist. The higher orders have a larger than 90 degree diffraction angle and therefore don't exist. You might check out: R.E. Bell. Exploring a transmission grating spectrometer. RSI 75 10 (2004)
 

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