fabrication process for the annular phase groove mask...

Ernesto Vargas, Caltech, 2016-08-15

Fabrication process for the annular phase groove mask

(AGPM)

Ernesto Vargas Catalán, Mikael Karlsson Uppsala University, Sweden


Content

• The AGPM

• Nano-replication

• Diamond etching

• Optical evaluation

• Tuning

• Fabricated/installed components

2


The AGPM

3 Polycrystalline chemically vapor deposited diamond 300 µm thick and 1 cm in diameter

A circular sub-wavelength grating


Nano-replication

4

Mask pattern transfer


Nano-replication

5

Metal mask pattern transfer

Metal mask prior to diamond etching Anisotropic etching


Diamond etching

6

The hard part


Optical evaluation

7

Re-measured grating parameters vs RCWA simulations and Rejection ratio using YACADIRE

Colorbar represents Rejection ratio (1/null depth)


Optical evaluation

8

Re-measured grating parameters vs RCWA simulations and Rejection ratio using YACADIRE

L9 estimate: d = 5.10±0.05 µm & w = 750±10 nm


Tuning

9

Optimizing depth to reach better performance


Tuning the AGPM

10

Facetting Higher angle Original

Deeper or shallower


RCWA and measurements (L+M filters)

11

Pinpointing probable parameters using experimental data

Improvement due to tuning Towards better perfomance


Finished components

• We have successfully manufactured AGPMs for N-, L- and K-band.

• 4 N-band

• 11 L-band

• 1 K-band

• We have successfully tuned L- and K-band AGPMs by etching deeper and shallower.

• 4 L-band

• 1 K-band 12


Finished components

VVC Rejection ratio Location

AGPM-N4 VLT(VISIR)

AGPM-L3 VLT(NACO)

AGPM-L4 630 LBTI(MIRC)

AGPM-L6 150 KECK(NIRC2)

AGPM-L7 550 KECK(NIRC2)

AGPM-L9r2 400 Ulg

AGPM-L11r 910 Ulg

AGPM-L12r 465 Ulg

AGPM-L14 370 LBTI(MIRC)

AGPM-K1r 200 Ulg 13

fabrication process for the annular phase groove mask...

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