Experimental characterization towards an in-fibre integrated silicon slab based all-optical modulator

Abstract

Background: Due to the industrially increasing interest in optics communication the field of all-optical modulation is becoming more and more popular. However, no in-fibre integrated miniaturized devices which provide current solutions were suggested as all-optical modulators with sufficient modulation depth and with low power consumption. Methods: In this paper, an all-optical silicon modulator with improved modulation depth is presented. The modulator will be developed as an in-fibre device for optics communication applications. The modulator is a silicon slab, 50 and 470 μm thick which is coated on both sides to get an improved Fabry-Perot resonator for laser beam at wavelength of 1550 nm. The modulator operation is based on the plasma dispersion effect which is induced by a pulsed visible laser beam acting as the pump for the creation of free charge carriers. Results: We have proved the coating withstands high energy fluency of the laser pulse. The different recombination and heat processes are examined. Our silicon based Fabry-Perot resonator increases the intrinsic c-Si finesse to 30. The improved finesse is shown to have significant effect on the modulation depth up to 12 dB. Conclusions: To the best of our knowledge this is the first experimental feasibility study of an all-optical modulator with sufficient modulation depth and with low power consumption which is also an in-fibre integrated miniaturized device based upon Si slab. Extensive experimental and numerical studies presented in this paper examine the influence of thermal effects and the sample parameters on the response time and on the modulation depth and the power consumption of the in-fibre integrated device. Apart from being a modulator, the proposed device can also act as tunable spectral filter.

Design of fiber-integrated tunable thermo-optic C-band filter based on coated silicon slab

“…The narrow transmission window is often measured as the bandwidth which in this paper is shown to be 0.07 nm or almost 9GHz. Furthermore, the bandwidth can be decreased below 3GHz by improving the finesse of the device: As shown in previous work [29], a finesse of 30 can be achieved which can yield the aforementioned narrow bandwidth. However, there is a tradeoff between greater channels separation in a 50 μm thick slab to better resolution in a 470 μm thick slab.…”

“…The transmission spectrum is shifted with the change in temperature which is controlled by a thermo-electric cooler (TEC) derived by "Wavelength Electronics" temperature controller (model "LFI-3751") with temperature control of 0.01 K. The tuning time is few seconds but can be decreased to few micro-seconds with resistive heating and even shorter with optical heating [29,34]. Even though optical heating can induce absorption, the real refractive index effect on a resonator transmission is usually larger than the increase in absorption [35].…”

“…The bandwidth is shown to be 0.07 nm or almost 9GHz. The coated Si slab improves the transmission performance over a bare Si, as was discussed and detailed in our previous work [29]. This paper is a follow-up work in which the slab improved performance is utilized in an in-fiber application i.e.…”