Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Free-form micro-optics enabling ultra-broadband low-loss fiber-to-chip
  coupling   Efficient fiber-to-chip coupling has been a major hurdle to cost-effective
packaging and scalable interconnections of photonic integrated circuits.
Conventional photonic packaging methods relying on edge or grating coupling are
constrained by high insertion losses, limited bandwidth density, narrow band
operation, and sensitivity to misalignment. Here we present a new fiber-to-chip
coupling scheme based on free-form reflective micro-optics. A design approach
which simplifies the high-dimensional free-form optimization problem to as few
as two full-wave simulations is implemented to empower computationally
efficient design of high-performance free-form reflectors while capitalizing on
the expanded geometric degrees of freedom. We demonstrated fiber array coupling
to waveguides taped out through a standard foundry shuttle run and backend
integrated with 3-D printed micro-optics. A low coupling loss down to 0.5 dB
was experimentally measured at 1550 nm wavelength with a record 1-dB bandwidth
of 300 nm spanning O to U bands. The coupling scheme further affords large
alignment tolerance, high bandwidth density and solder reflow compatibility,
qualifying it as a promising optical packaging solution for applications such
as wavelength division multiplexing communications, broadband spectroscopic
sensing, and nonlinear optical signal processing.

18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys