Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Luneburg lens in silicon photonics   The Luneburg lens is an aberration-free lens that focuses light from all
directions equally well. We fabricated and tested a Luneburg lens in silicon
photonics. Our technique is sufficiently versatile for making perfect imaging
devices on silicon platforms.

5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th