add brief challenge description

challenges/photon_extractor/README.md

@@ -1 +1 @@
-- `201218_chakravarthi` solution was extracted from Figure 1 of [Inverse-designed photon extractors for optically addressable defect qubits](https://opg.optica.org/optica/fulltext.cfm?uri=optica-7-12-1805&id=444947), by Chakravarti et al.
+- `201218_chakravarthi` solution was extracted from Figure 1 of "[Inverse-designed photon extractors for optically addressable defect qubits](https://opg.optica.org/optica/fulltext.cfm?uri=optica-7-12-1805&id=444947)", by Chakravarti et al.

docs/notebooks/ceviche_challenges.ipynb

@@ -5,7 +5,11 @@
    "id": "0f55fcc2",
    "metadata": {},
    "source": [
-    "# Ceviche challenges"
+    "# Ceviche challenges\n",
+    "\n",
+    "Visit the invrs-gym docs for the [ceviche challenges](https://invrs-io.github.io/gym/notebooks/ceviche_challenge.html).\n",
+    "\n",
+    "The ceviche challenges are based on \"[Inverse design of photonic devices with strict foundry fabrication constraints](https://doi.org/10.1021/acsphotonics.2c00313)\" by M. F. Schubert et al., and the associated [github repo](https://github.com/google/ceviche-challenges). They entail the design of integrated photonic components such as a beam splitter, mode converter, waveguide bend, and wavelength demultiplexer (wdm)."
    ]
   },
   {

docs/notebooks/diffractive_splitter.ipynb

@@ -5,7 +5,11 @@
    "id": "6dd24c9b",
    "metadata": {},
    "source": [
-    "# Diffractive splitter"
+    "# Diffractive splitter\n",
+    "\n",
+    "Visit the invrs-gym docs for the [diffractive splitter challenge](https://invrs-io.github.io/gym/notebooks/diffractive_splitter_challenge.html).\n",
+    "\n",
+    "The diffractive splitter challenge is based on the “[Design and rigorous analysis of a non-paraxial diffractive beamsplitter](https://www.lighttrans.com/fileadmin/shared/UseCases/Application_UC_Rigorous%20Analysis%20of%20Non-paraxial%20Diffractive%20Beam%20Splitter.pdf)” slide deck retrieved from the LightTrans web site, and entails the design of a metasurface that evenly splits a normally-incident plane wave into a 7x7 array of beams, with diffraction angles of ±15 degrees."
    ]
   },
   {

docs/notebooks/meta_atom_library.ipynb

@@ -5,7 +5,11 @@
    "id": "874f5463",
    "metadata": {},
    "source": [
-    "# Meta-atom library"
+    "# Meta-atom library\n",
+    "\n",
+    "Visit the invrs-gym docs for the [meta-atom library challenge](https://invrs-io.github.io/gym/notebooks/library_challenge.html).\n",
+    "\n",
+    "The meta-atom library challenge is based on “[Dispersion-engineered metasurfaces reaching broadband 90% relative diffraction efficiency](https://www.nature.com/articles/s41467-023-38185-2)” by Chen et al., and entails the design of eight meta-atoms for use in broadband, visible-wavelength metasurfaces."
    ]
   },
   {

docs/notebooks/metagrating.ipynb

@@ -5,7 +5,11 @@
    "id": "8aa852ee",
    "metadata": {},
    "source": [
-    "# Metagrating"
+    "# Metagrating\n",
+    "\n",
+    "Visit the invrs-gym docs for the [metagrating challenge](https://invrs-io.github.io/gym/notebooks/metagrating_challenge.html).\n",
+    "\n",
+    "The metagrating challenge is based on  “[Validation and characterization of algorithms and software for photonics inverse design](https://opg.optica.org/josab/ViewMedia.cfm?uri=josab-41-2-A161)” by Chen et al., and entails the design of a metasurface that deflects a normally-incident plane wave so that it propagates with a polar angle of 50 degrees."
    ]
   },
   {

docs/notebooks/metalens.ipynb

@@ -5,7 +5,11 @@
    "id": "871d2aea",
    "metadata": {},
    "source": [
-    "# Metalens"
+    "# Metalens\n",
+    "\n",
+    "Visit the invrs-gym docs for the [metalens challenge](https://invrs-io.github.io/gym/notebooks/metalens_challenge.html).\n",
+    "\n",
+    "The metalens challenge is based on  “[Validation and characterization of algorithms and software for photonics inverse design](https://opg.optica.org/josab/ViewMedia.cfm?uri=josab-41-2-A161)” by Chen et al., and entails the design of one-dimensional metalens that focuses normally-incident 450 nm, 550 nm, and 650 nm plane waves to a point 2.4 microns above the metalens surface."
    ]
   },
   {

docs/notebooks/photon_extractor.ipynb

@@ -3,13 +3,13 @@
   {
    "cell_type": "markdown",
    "id": "109455b4",
-   "metadata": {
-    "tags": [
-     "hide-cell"
-    ]
-   },
+   "metadata": {},
    "source": [
-    "# Photon extractor"
+    "# Photon extractor\n",
+    "\n",
+    "Visit the invrs-gym docs for the [photon extractor challenge](https://invrs-io.github.io/gym/notebooks/photon_extractor_challenge.html).\n",
+    "\n",
+    "The metalens challenge is based on  “[Inverse-designed photon extractors for optically addressable defect qubits](https://opg.optica.org/optica/fulltext.cfm?uri=optica-7-12-1805)” by Chakravarthi et al., and entails the design of a patterned GaP layer that enhances the power collected from a nitrogen vacancy defect buried at a depth of 100 nm within a diamond substrate."
    ]
   },
   {