Diploma thesis

Figure 3.35: Unfiltered JSA, JSA + filter function, filtered JSA
of heavy photon loss.
In order to quantify the performance of this method we choose a common KTP
waveguide chip. In KTP most of the nonlinear indices dij are vanishing [22], with
the exception of:
❏ d15 = 3.7 pm/V
❏ d24 = 1.9 pm/V
❏ d31 = 3.7 pm/V
❏ d32 = 2.2 pm/V
❏ d33 = 14.6 pm/V
. Only a few processes remain:
⎛
⎝
Px
Py
Pz
⎞ ⎛
0
⎠ = ɛ0 ⎝ 0
3.7
0
0
2.2
0
0
14.6
0
1.9
0
3.7
0
0
⎞
0
0⎠
·
0
pm
V ·
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜
⎜2EyEz
⎟
⎝2EzEx
⎠
2ExEy
⎛
(Ex) 2
(Ey) 2
(Ez) 2
Five different processes are available in KTP, the strongest is a type-I downconversion
process with z-polarized pump, signal and idler fields. However we have
to separate the signal and idler photons after they leave the crystal and therefore
must excite a type-II downconversion process, despite the smaller nonlinearities as
opposed to type-I downconversion.
We choose a waveguide chip with parameters depicted in Table 3.3. The chip is
periodically poled in such a way that it fulfills phasematching conditions at λs,i =
800 nm. KTP as a material is very common and crystals with these parameters are
often applied in experiments investigating entanglement properties.
⎞
27