Design

7.2 Design

Mid-IR to near-IR conversion based on parametric conversion is based on non-linear phenomena inside the optical waveguide hosting the interaction. Although the 3-5μm wavelength range (which is the spectral window of interest for chemical and biological sensing) is well covered in terms of losses, when it comes to strong non-linearities it is better to include Ge as well however at the expense of increased losses at the near-IR region. SiGe alloys have been proposed and used in order to best deliver light from the main optical source residing in the mid-IR the Quantum Cascade Laser (QCL) with Si-encapsulated waveguides.

However, in order to achieve parametric conversion in such distant wavelengths there are two main issues to be dealt with. The first is that the signals must be phase matched and a pump is necessary at an intermediate wavelength in order to carry on the parametric process. This means that the structure must present a zero dispersion wavelength close to the pump laser emission wavelength. Additionally, the modal confinement must be very good in order to enhance non-linear phenomena. So, a high-index contrast is needed which will provide both small effective mode areas and engineered waveguide dispersion.

Moreover, there are still some functions that need to be addressed in the multifunctional photonic integrated circuit used for chemical sensing. A combiner is needed in order to place the two spectrally distant signals inside the non-linear waveguide. This is accomplished through a dichroic-like coupler which takes advantage of the very different propagation constants of the two signals in order to introduce an 2-in-1 combiner. Finally, within the CLARITY project, all designs concerning mode conversion for efficient in- and out-coupling were produced through careful consideration of all parameters that affect the highly demanding process of low-insertion loss coupling.

Related projects:

CLARITY
COST MP1204: “TERA-MIR Radiation: Materials, Generation, Detection and Applications”

Significant publications:

M. A. Ettabib, K. Hammani, X. Feng, M. Belal, J. Shi, A. Bogris, A. Kapsalis, D. Syvridis, D. J. Richardson, and P. Petropoulos, “Highly nonlinear tellurite glass fiber for broadband applications,” in Optics InfoBase Conference Papers, 2014.
K. Hammani, M. A. Ettabib, A. Bogris, A. Kapsalis, D. Syvridis, M. Brun, P. Labeye, S. Nicoletti, and P. Petropoulos, “Towards nonlinear conversion from mid- to near-infrared wavelengths using Silicon Germanium waveguides.,” Opt. Express, vol. 22, no. 8, pp. 9667–74, May 2014.
K. Hammani, M. A. Ettabib, A. Bogris, A. Kapsalis, D. Syvridis, M. Brun, P. Labeye, S. Nicoletti, D. J. Richardson, and P. Petropoulos, “Optical properties of silicon germanium waveguides at telecommunication wavelengths.,” Opt. Express, vol. 21, no. 14, pp. 16690–701, Jul. 2013.
M. A. Ettabib, K. Hammani, F. Parmigiani, L. Jones, A. Kapsalis, A. Bogris, D. Syvridis, M. Brun, P. Labeye, S. Nicoletti, and P. Petropoulos, “FWM-based wavelength conversion of 40 Gbaud PSK signals in a silicon germanium waveguide.,” Opt. Express, vol. 21, no. 14, pp. 16683–9, Jul. 2013.
K. Hammani, M. A. Ettabib, A. Bogris, A. Kapsalis, D. Syvridis, M. Brun, P. abeye, S. Nicoletti, D. J. Richardson, and P. Petropoulos, “Linear and nonlinear properties of sige waveguides at telecommunication wavelengths,” in Optical Fiber Communication Conference, OFC 2013, 2013.