started subchapter "subsystems and components".

Also added katex preprocessor in book.toml for math eqs.

book/book.toml

@@ -4,3 +4,7 @@ language = "en"
 multilingual = false
 src = "src"
 title = "OPOSSUM Handbook"
+
+
+[preprocessor.katex]
+after = ["links"]

book/src/SUMMARY.md

@@ -4,10 +4,11 @@
   - [Goals](./goals.md)
   - [Project plan](./plan.md)
 - [Existing Software](./existing_software.md)
-- [Modelling optical systems](./optical_model.md)
+- [Modeling optical systems](./optical_model.md)
   - [Nodes](./nodes.md)
   - [Edges](./edges.md)
   - [Materials](./materials.md)
+  - [Physical processes, Subsystems and Components](./optical_components_effects.md)
 - [Model analysis](./model_analysis.md)
   - [Analyzers](./analyzers.md)
   - [Interfacing with external code](./interfacing.md)

book/src/optical_components_effects.md

+# Subsystems and Components
+
+Modern laser systems are composed of a large number of optical subsystems and individual optical components. For a holistic description of such a system, all these optical components and the structures that are built from these must be modeled. Furthermore, a numerous amount of physical effects/processes must be included to create a realistic view of the full system.
+
+In the following, a, probably not complete, list of relevant effects/processes, subsystems and components for high-intensity lasers will be compiled. 
+
+## Physical Effects/Processes
+### Second-order nonlinear effects
+Second-order nonlinear effects include all processes that result from the response of the second-order susceptibility $\chi^{(2)}$:
+* Second-Harmonic Generation (SHG)
+* Sum-Frequency Generation (SFG)
+* Difference-Frequency Generation (DFG)
+* Optical Rectification (OR)
+* Optical Parametric Amplification (OPA)
+