Kramers Kronig Dispersion Relations and MZ Modulator

Wavelength detuning in MZ modulator is important parameter as the change in Index of Refraction depend on absorption coefficient change alpha. The larger detuning leads to larger loss due to alpha change from Kramers Kronig Relation. If the absorption peak is situated further away from operating wavelength, the change of refractive index is small and hence need larger voltage for sufficient pi phase shift. We can use absorption measurements and Reflectance measurements to calculate the real part of refractive index and the phase. this will enable us to find optimum parameters for the devices.Refractive Index change is highly polarised due to its dependence on change in Alpha which is the transition between electron state E1 and heavy holes state HH1 tends to be TE polarised. The change in refractive index is due both QCSE and Pockels effect even though Pockels effect is in the order of magnitude smaller compared to QCSE effect nonetheless not negligible when the detuning is much larger than 160nm.

Electro-absorption vs Mach-Zehnder Modulators

Probably, i have already talked about modulators, as the speed and bandwidth drives the technology ever forward i will just introduce two types of modulators used in optic networks. Electro-absorption modulators exploit the properties of materials under the influence of electric field to modulate the light carrying signals by absorption.
This type of modulators have a drawback for having a limit to how fast you can modulate light due to material properties especially the incumbent InGaAsP where valence band offset limit the depletion of holes.
Mach-Zehnder modulators uses intensity modulation where by a pi phase change between the path length leads to modulation of light. We can also use the QCSE effect to improve the Mach-Zehnder by reducing Voltage needed to change phase to pi we can use Kramers-Kronig relation to calculate the effect of absorption coefficient change on refractive index.

Back to Uni with tales from Caswell

As i pack my belongings for my journey back to University after 3 Months of placement at work i feel overcomed by sheer joy of achieving my goals at Caswell.

I know I will miss cycling back and forth to work through beautiful countryside scenery, I believe the images of farms are vividly emblazoned in my mind. I bade good bye to my adopted team of beautiful people and head for the train station at Milton Keynes. The birds who without fail woke me up early in the morning with their sweetest songs will be servely missed and whiff of manure that permiated the air as i cycle through narrow roads on the hills will be remembered always.

the hope that experience gained at Oclaro is weighs heavily in my mind on how to translate my knowledge into sustainable means of income.

I am glad i saw the other side of real world application of my academic knowledge.

Now i am looking forward to wrap up and finish my studies (GW). Surrey here i come......