MOGlabs DLC202, Руководство пользователя, Страница: 57 / 82

C. Modulation coils
The
MOG
labs
DLC
is designed to lock to an atomic transition, par-
ticularly using
AC
locking. The frequency of the laser light can
be modulated (e.g. using internal current modulation or an external
modulator), or the reference can be modulated. In the latter case,
an atomic reference can be modulated at low cost using a solenoid
coil wrapped around an atomic vapour cell, as shown below.
Figure C.1: Vapour cell, Zeeman coil, and primary excitation coil, mounted
on
PCB
(available from MOGlabs).
C.1 Field requirements
Ideally the Zeeman dither coil should produce a frequency shift of
about half the peak width, typically a few MHz. Atomic “stretched”
state transitions will be Zeeman shifted by
µ
B
=
e ¯ h
2 m
e
= 1 . 4 MHz / Gauss (C.1.1)
so we need fields of around one Gauss (10
− 4
Tesla). The magnetic
field inside a long solenoid is
B = µ
0
ni (C.1.2)
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