Machining metre-sized gratings with nanometre accuracy
David Buscher + optical instrumentation group
The echelle spectrograph is the workhorse of optical/infrared astronomy
The size of the diffraction grating is constrained by fundamental physics
Uncertainty principle:
Conservation of étendue:
For a seeing-limited spectrograph:
\Delta \nu\Delta x = \text{constant}
\Delta \Omega \Delta S = \text{constant}
\text{grating size}\propto R \times D
For E-ELT HIRES the grating may need to be as big as 1.6m
The error in the groove positions need to be as small as 1nm
Conventional grating ruling engines are not scaleable to large sizes
Mosaiced gratings are difficult to make stable
A promising new grating technology is silicon wet-etching
This produces nanometre-smooth structures
Lithography on large scales is challenging
Interferometric delay lines achieve nanometre precision over large distances
The MROI delay line
Overall concept
"Lithography engine" concept
Measuring grating performance
Current project (2021-2024)
- £900k grant from EPSRC for precision manufacturing
- Develop "lithography engine" for patterning a 150mm wafer
- Measure performance
- Make and test gratings based on single wafers
Coffee mini-seminar Manufacturing metre-sized gratings
By dbuscher
Coffee mini-seminar Manufacturing metre-sized gratings
Coffee-time mini-seminar
