Transcript No Slide Title

Simplest interrogation
scheme for the two-photons
transition
Two-photons Ramsey
spectroscopy
• Raby frequency:  
E
2
2

k
Re, k Rk ,g
dw
P
 3.310
w
4
E: electric field strength; Ri,j: ij transition probability;
dw: laser detuning; P: power in W; w: waist radius in m
• To have a π/2 pulse:
t 
P
4
 
 0.5 10
2
2
wv
t: interaction time; v: atomic velocity in m/s
• This is possible with v = 20 m/s and P = 50 W (laser
power: 0.5 W, cavity enhancement factor: 100) using
a waist radius of 0.5 mm
Measurement of the onephoton transition probability
• The transition rate Aki for the intercombination line
@ 657.3 nm is well known (2900 s-1)
• Simultaneous measurement of the integrated
absorption coefficient a(n) @ 457.5 nm and
657.3 nm
2
Pt n 
gk 
a  n  L
; an   N
gn Aki
• Cell transmission: P n   e
g 4
0
i
L: length of the absorbing vapor; N: atomic density;
g(n): normalized lineshape; gi: level degeneracy
Apparatus for measuring the
E2 transition rate
•
•
•
•
Ti:Sa laser: 400 mW CW @ 915 nm
SHG with a KNbO3 crystal: 300 mW @ 457.5 nm
ECDL: 10 mW CW @ 657.3 nm
Frequency calibration: two Fabry-Pérot resonators
FSR 300 MHz
• Absorption cell
length 0.6 m; diameter 2.5 cm; temperature 650÷700 °C
Data analysis
• Fit assuming a pure Doppler line broadening
Doppler linewidth ≈ 2 GHz
n Doppl er
3


10
buffer gas (Ar) pressure: 10÷20 Pa
 n hom ogeneous
broadening coefficient ≈ 100÷150 kHz/Pa
• Isotopic structure
most abundant isotopes: 40Ca (96.9%), 44Ca (2%), 42Ca (0.6%)
gn   0.969 Gn   0.02 Gn  n 4044   0.006 Gn  n 4044 
G(n) normalized Gaussian function
Experimental apparatus
for measuring the E2
transition rate