THORLABS HNLS008L, Руководство пользователя

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HNLS008R(L) Red HeNe Laser System Chapter 2: Description
Rev C, March 23, 2015 Page 9
HeNe Gain Curve Showing Cavity Modes
Figure 3
The laser process in a HeNe laser starts with the collision of electrons from the electrical discharge with the
helium atoms in the gas. This excites helium from the ground state to a long-lived, metastable excited state.
Collision of excited helium atoms with ground-state neon atoms results in excited neon electrons.
HeNe Energy Levels
Figure 4
The number of neon atoms entering the excited states builds up until population inversion is achieved.
Spontaneous and stimulated emission between the states results in emission of 632.82 nm light along with other
emission wavelengths. From these states, the electrons quickly decay to the ground state. The HeNe laser’s
power output is limited because the neon upper level saturates with higher current, while the lower level varies
linearly with current.
Neon Gain
Curve
FWHM ~1.5 GHz
Frequency
Gain/Output Power
Lasing
Cavity Modes
Lasing
Threshold
FSR ~1000 MHz
Short (0.2 m) Laser
FSR ~200 MHz
Long (1 m) Laser
Energy (Electron V
olts)
Ground States
Metastable Collision
Metastable Collision
e Impact
3S
2
1
S
3
S
2S
2
1S
2P
4
3P
4
(20.66 eV)
(20.30 eV)
(20.61 eV)
(19.78 eV)
(19.78 eV)
(18.70 eV)
1
2
5
10
21
20
19
18
17
16
(16.70 eV)
(3391.2 nm Laser)
(632.8 nm Laser)
(1152.3 nm Laser)
Diffusion
Helium
Neon