minor docs update (NanoComp#1181)

* minor docs update

* clarification

Co-authored-by: Steven G. Johnson <stevenj@mit.edu>

doc/docs/Acknowledgements.md

@@ -5,7 +5,7 @@
 Authors
 -------
 
-Meep originated as part of graduate research at [MIT](https://en.wikipedia.org/wiki/Massachusetts_Institute_of_Technology) with initial contributions by [Steven G. Johnson](http://math.mit.edu/~stevenj/), [Ardavan Oskooi](http://ab-initio.mit.edu/~oskooi/), [David Roundy](http://physics.oregonstate.edu/~roundyd/), [Mihai Ibanescu](https://www.linkedin.com/in/mihai-ibanescu-2b147825/), and [Peter Bermel](http://web.ics.purdue.edu/~pbermel/). Currently, the Meep project is maintained by [Simpetus](http://www.simpetus.com) and the developer community on [GitHub](https://github.com/NanoComp/meep). [Christopher Hogan](https://github.com/ChristopherHogan) and [M.T. Homer Reid](http://homerreid.dyndns.org/) lead the development of the [Python interface](Python_User_Interface.md), [mode-decomposition feature](Python_Tutorials/Mode_Decomposition.md), and [GDSII import routines](Python_Tutorials/GDSII_Import.md). M.T. Homer Reid developed the [adjoint solver](Python_Tutorials/AdjointSolver.md). [Alex Cerjan](http://www.alexcerjan.com/) assisted with adding support for saturable absorption via [multilevel atomic gain media](Materials.md#saturable-gain-and-absorption). [Alec Hammond](https://github.com/smartalecH/) developed the [visualization module](Python_User_Interface.md#data-visualization). [Yidong Chong](http://www1.spms.ntu.edu.sg/~ydchong/bio.html) and Alex Cerjan added support for [gyrotropic media](Materials.md#gyrotropic-media).
+Meep originated as part of graduate research at [MIT](https://en.wikipedia.org/wiki/Massachusetts_Institute_of_Technology) with initial contributions by [Steven G. Johnson](http://math.mit.edu/~stevenj/), [Ardavan Oskooi](http://ab-initio.mit.edu/~oskooi/), [David Roundy](http://physics.oregonstate.edu/~roundyd/), [Mihai Ibanescu](https://www.linkedin.com/in/mihai-ibanescu-2b147825/), and [Peter Bermel](http://web.ics.purdue.edu/~pbermel/). Currently, the Meep project is maintained by [Simpetus](http://www.simpetus.com) and the developer community on [GitHub](https://github.com/NanoComp/meep). [Christopher Hogan](https://github.com/ChristopherHogan) and [M.T. Homer Reid](http://homerreid.dyndns.org/) lead the development of the [Python interface](Python_User_Interface.md), [mode-decomposition feature](Python_Tutorials/Mode_Decomposition.md), and [GDSII import routines](Python_Tutorials/GDSII_Import.md). M.T. Homer Reid and [Alec Hammond](https://github.com/smartalecH/) developed the [adjoint solver](Python_Tutorials/AdjointSolver.md). [Alex Cerjan](http://www.alexcerjan.com/) assisted with adding support for saturable absorption via [multilevel atomic gain media](Materials.md#saturable-gain-and-absorption). Alec Hammond developed the [visualization module](Python_User_Interface.md#data-visualization). [Yidong Chong](http://www1.spms.ntu.edu.sg/~ydchong/bio.html) and Alex Cerjan added support for [gyrotropic media](Materials.md#gyrotropic-media).
 
 Referencing
 -----------

doc/docs/FAQ.md

@@ -334,7 +334,7 @@ There are five ways to define a structure: (1) the [`GeometricObject`](Python_Us
 
 ### Does Meep support importing GDSII files?
 
-Yes. The [`get_GDSII_prisms`](Python_User_Interface.md#gdsii-support) routine is used to import [GDSII](https://en.wikipedia.org/wiki/GDSII) files. See [Tutorial/GDSII Import](Python_Tutorials/GDSII_Import.md) for an example. This feature facilitates the simulation of 2d/planar structures which are fabricated using semiconductor foundries. Also, it enables Meep's plug-and-play capability with [electronic design automation](https://en.wikipedia.org/wiki/Electronic_design_automation) (EDA) circuit-layout editors (e.g., Cadence Virtuoso Layout, Silvaco Expert, KLayout, etc.). EDA is used for the synthesis and verification of large and complex integrated circuits. A useful tool for creating GDS files of simple geometries (e.g., curved waveguides, ring resonators, directional couplers, etc.) is [gdspy](https://gdspy.readthedocs.io/en/stable/).
+Yes. The [`get_GDSII_prisms`](Python_User_Interface.md#gdsii-support) routine is used to import [GDSII](https://en.wikipedia.org/wiki/GDSII) files. See [Tutorial/GDSII Import](Python_Tutorials/GDSII_Import.md) for examples. This feature facilitates the simulation of 2d/planar structures which are fabricated using semiconductor foundries. Also, it enables Meep's plug-and-play capability with [electronic design automation](https://en.wikipedia.org/wiki/Electronic_design_automation) (EDA) circuit-layout editors (e.g., Cadence Virtuoso Layout, Silvaco Expert, KLayout, etc.). EDA is used for the synthesis and verification of large and complex integrated circuits. A useful tool for creating GDS files of simple geometries (e.g., curved waveguides, ring resonators, directional couplers, etc.) is [gdspy](https://gdspy.readthedocs.io/en/stable/).
 
 ### Can Meep simulate time-varying structures?
 
@@ -507,4 +507,4 @@ The second approach is based on a full nonlinear simulation of the Raman process
 
 ### Does Meep support adjoint-based optimization?
 
-Yes. Meep contains an [adjoint solver](Python_Tutorials/AdjointSolver.md) which can be used for sensitivity analysis and automated design optimization.
+Yes. Meep contains an [adjoint solver](Python_Tutorials/AdjointSolver.md) which can be used for sensitivity analysis and automated design optimization with respect to a grid of ε values (also known as "density-based" topology optimization).  (Of course, you can always use finite differences or similar methods to compute sensitivities for other parameters, as well as derivative-free optimization methods. However, such methods become increasingly impractical for ≳ 10 parameters.)

doc/docs/Python_Tutorials/GDSII_Import.md

@@ -9,7 +9,7 @@ This tutorial demonstrates how to set up a simulation based on importing a [GDSI
 S-Parameters of a Directional Coupler
 -------------------------------------
 
-The directional coupler as well as the source and mode monitor geometries are described by the GDSII file [examples/coupler.gds](https://github.com/NanoComp/meep/blob/master/python/examples/coupler.gds). A snapshot of this file viewed using [KLayout](https://www.klayout.de/) is shown below. The figure labels have been added in post processing. The design consists of two identical [strip waveguides](http://www.simpetus.com/projects.html#mpb_waveguide) which are positioned close together via an adiabatic taper such that their modes couple evanescently. There is a source (labelled "Source") and four mode monitors (labelled "Port 1", "Port 2", etc.). The input pulse from Port 1 is split in two and exits through Ports 3 and 4. The design objective is to find the separation distance which maximizes the outgoing power in Port 4 at a wavelength of 1.55 μm. More generally, though not included in this example, it is possible to have two additional degrees of freedom: (1) the length of the straight waveguide section where the two waveguides are coupled and (2) the length of the tapered section (the taper profile is described by a hyperbolic tangent (tanh) function).
+The directional coupler as well as the source and mode monitor geometries are described by the GDSII file [`examples/coupler.gds`](https://github.com/NanoComp/meep/blob/master/python/examples/coupler.gds). A snapshot of this file viewed using [KLayout](https://www.klayout.de/) is shown below. The figure labels have been added in post processing. The design consists of two identical [strip waveguides](http://www.simpetus.com/projects.html#mpb_waveguide) which are positioned close together via an adiabatic taper such that their modes couple evanescently. There is a source (labelled "Source") and four mode monitors (labelled "Port 1", "Port 2", etc.). The input pulse from Port 1 is split in two and exits through Ports 3 and 4. The design objective is to find the separation distance which maximizes the outgoing power in Port 4 at a wavelength of 1.55 μm. More generally, though not included in this example, it is possible to have two additional degrees of freedom: (1) the length of the straight waveguide section where the two waveguides are coupled and (2) the length of the tapered section (the taper profile is described by a hyperbolic tangent (tanh) function).
 
 <center>
 ![](../images/klayout_schematic.png)
@@ -321,7 +321,7 @@ if __name__ == '__main__':
             print("mode:, {}, {}".format(w,Q))
 ```
 
-Note the omission of `symmetries` even though, in principle, the ring geometry and the two line sources satisfy two mirror symmetry planes through the $x$ (even) and $y$ (odd) axes. This omission is due to the fact that the ring geometry created using gdspy and imported from the GDSII file is actually a [`Prism`](../Python_User_Interface.md#prism) consisting of a discrete number of vertices (rather than two overlapping `Cylinder`s as in [Tutorial/Basics/Modes of a Ring Resonator](../Python_Tutorials/Basics.md#modes-of-a-ring-resonator)). Discretization artifacts of the `Prism`-based ring geometry slightly break its symmetry. (Attempting to use `symmetries` in this case would produce unpredictable results.)
+Note the absence of `symmetries` even though, in principle, the ring geometry and the two line sources satisfy two mirror symmetry planes through the $x$ (even) and $y$ (odd) axes. This omission is due to the fact that the ring geometry created using gdspy and imported from the GDSII file is actually a [`Prism`](../Python_User_Interface.md#prism) consisting of a discrete number of vertices (rather than two overlapping `Cylinder`s as in [Tutorial/Basics/Modes of a Ring Resonator](../Python_Tutorials/Basics.md#modes-of-a-ring-resonator)). Discretization artifacts of the ring geometry slightly break its mirror symmetry. (Attempting to use `symmetries` in this case yields unpredictable results.)
 
 For this ring geometry, `Harminv` finds a mode with wavelength `1.5490604` μm and $Q$ of `124691.308`. The $H_z$ field profile is shown below. As expected, due to the large $Q$ the mode is tightly confined to the ring and exhibits little radiative loss.
 

scheme/Makefile.am

@@ -56,7 +56,7 @@ meep-enums.scm: meep_enum_renames.i
 ##############################################################################
 
 # what is printed out when invoking your program with --version:
-VERSION_STRING = "Meep @VERSION@, Copyright (C) 2005-2019 Massachusetts Insitute of Technology."
+VERSION_STRING = "Meep @VERSION@, Copyright (C) 2005-2020 Massachusetts Insitute of Technology."
 
 MY_DEFS = -DHAVE_CTL_HOOKS=1 -DHAVE_CTL_EXPORT_HOOK=1