Update README.md

README.md

@@ -30,12 +30,24 @@ Increase the arm cavity Finesse, will change the DARM linewidth, but not the CAR
 
 Pros:
  * Allows for increasing the SRC Finesse, while keeping the overall DARM pole frequency ~400 Hz.
- * 
+ * smaller beam size at the BS & ITM
 
 Cons:
  * Increased coating thermal noise from the ITMs (very small effect)
  * harder to lock the single arms during testing
 
+
+### Arm Cavity g-factor
+Make the cavity stable.
+
+Pros:
+ * change the Sidles-Sigg effect
+ * change the PI situation
+
+Cons:
+ * Increased coating thermal noise from the TMs
+ * mode-matching to the SRC ?
+
 ### DRMi locking (limited by Arm and SRC finesse)
 The SRC is tricky to lock because it has a low finesse (mode hopping, …). The choice of SRC finesse resulted from the (somewhat arbitrary, see <a href="https://dcc.ligo.org/LIGO-T070303">T070303</a>) choice of a relatively low finesse for the arm cavities, which was designed to aid lock acquisition but may have been overkill.