1. Helium-Neon laser
Henrik Porte

2. High starting voltage
Operating voltage: 1000 V
Pressure ratio He:Ne = 5:1
Discharge-bore diameter: 1.5 mm

3. Energy level scheme Metastable states
Main operating transition:632.8 nm
Radiation trapping
Doppler broadening

4. Gain and saturation Small gain coefficient: 0.15 m-1
Stimulated emission cross section: m2
Saturation intensity: ^3 W/m2
Threshold:
- gthmL≈12
- minimum gain duration: µs
Isat=2 pi v^2 h v (Aui+Alj)/(c^2 Aul tu)
Pout=Isat ((go L/ a+t)-1) t A

5. Cavity and output parameters
- 1% transmitting flat mirror
- 99.9% reflecting spherical mirror
Pumping power: 1-10 W
Output power: mW
High quality TEM00 mode charistics
1-11 longitudinal modes

6. Spontaneous emission / stimulated emission
The behaviour of a typical single-crystal Si solar cell under high intensity of electric field
Spontaneous emission / stimulated emission
Influence of electric field
S. Erel et. al. Solar energy materials and solar cells, volume 90, 23 march 2006, ( )