[Yuhang, Eleonora, Matteo]
In order to match the green beam transmitted from the green MC into the OPO we have characterized the green beam produced by OPO when it is locked with s-pol beam. Its paramenters will be the target ones for the mode matching telescope we have to design.
Since the beam is very weak (about 0.2 uW) we couldn't use the beam profile and we used a blade to do the characterization, instead.
Procedure: we attached a cutter blade to a traslation stage (See Fig.1) in order to be able to progressively cut the beam, by small and known steps. For each step we recorded the power of the beam with a PD placed after the blade. Since the beam in gaussian the shape of this function is expected to be a error function (erf):
P (x) = a*erf(sqrt(2)*(x-x0)/w)+o
By fitting the data with this function we could extract the beam radius w for each position z at which the measurement was performed.
The beam size and the corresponding waist (in meter) are reported below and plotted in Fig 2. The zero of the z-axis is taken at the incoupling mirror side of the OPO.
0.00098238 0.00115781 0.00142657 0.00143289 0.00290379 0.00266076
0.00338225 0.00324448 0.00390693
0.00098238 0.00115781 0.00142657 0.00143289 0.00290379 0.00266076
0.00338225 0.00324448 0.00390693
z = [0.125, 0.15, 0.175, 0.20, 0.37, 0.395, 0.42, 0.47, 0.52];
w = [0.982, 1.158, 1.426, 1.433, 2.904, 2.661, 3.382, 3.245, 3.907]*10^-3;
We fitted these data with the usual function, describing the evolution of the beam size as a function of the position z [w(z) = w0*sqrt(1+((x-z0)/(pi*w0**2/l))**2)]
and we could extract the size and the position of the waist: z = 1.97 +/- 2.2 cm. w0 = 24 +/- 1.5 um
These parameters are in agreement with what we expected from simulation (see entry
#1013) but the error on the waist position is quite large.
[Note that w0_532 = w0_1064/ sqrt(2)]
Conclusion: the parameters of green beam produced by OPO are how we expected and can be used to design the telescope for matching the green beam from SHG into OPO.
0.00338225 0.00324448 0.00390693
0.00098238 0.00115781 0.00142657 0.00143289 0.00290379 0.00266076
0.00338225 0.00324448 0.00390693
0.00338225 0.00324448 0.00390693
