ld_drive: add a param for setting to cal pd pwr

- Conversion ratio between pd current and ld output power

src/laser_diode/ld_drive.rs

@@ -1,6 +1,6 @@
 use miniconf::Miniconf;
 use crate::laser_diode::current_sources::CurrentSource;
-use core::marker::PhantomData;
+use core::{marker::PhantomData, f64::NAN};
 
 use uom::si::{
     electric_current::{milliampere},
@@ -46,12 +46,14 @@ impl Settings{
 #[derive(Clone, Debug, Miniconf)]
 pub struct Settings {
     pub ld_drive_current: ElectricCurrent,
+    pub pd_i_to_out_pwr: i_to_power_unit,
 }
 
 impl Default for Settings {
     fn default() -> Self {
         Self {
             ld_drive_current: ElectricCurrent::new::<milliampere>(0.0),
+            pd_i_to_out_pwr: i_to_power_unit {dimension: PhantomData, units: PhantomData, value: NAN}
         }
     }
 }