Marco Trotta

A Switchable Liquid-Crystal Optical Channel Waveguide on Silicon

An integrated optical switch based on liquid crystal on silicon is reported. The switch consists of an optical waveguide, whose core is made of nematic liquid crystal E7 infiltrated in a SiO2/Si V-groove. The electrooptic effect allows us to control the waveguide propagation condition by means of ITO and Si electrodes. A voltage as low as 2 V applied to the driving electrodes turns the waveguide on. Since the output intensity increases with voltage, the waveguide behaves also as a variable optical attenuator. A maximum ON-OFF extinction ratio in excess of 44 dB was measured.

All-optical intensity modulation of near infrared light in a liquid crystal channel waveguide

We demonstrate a nonlinear optical channel waveguide made of E7 nematic liquid crystal infiltrated in a silica on silicon groove. Near infrared light at the wavelength of 1560 nm fiber coupled to the core of the liquid crystal waveguide was optically modulated by an optical beam with power below 25 mW by exploiting the optical Freedericks transition. By modeling the optical molecular reorientation in the nematic liquid crystal confined in a waveguiding geometry we are able to reproduce the experimental results.

Realization of a Liquid Crystal Electrically Controlled Optical Waveguide on Micromachined Silicon

In this paper we report the major fabrication steps and preliminary electro-optical characterization of a novel integrated liquid crystal optical waveguide on silicon substrate. The optical waveguide is made of a SiO2/Si V-groove with a triangular cross-section filled with nematic liquid crystal E7. The optical propagation in the channel waveguide is controlled by an external voltage which induces a refractive index variation by means of molecular director reorientation. For TM polarized light at a wavelength of 1.55 μm, a threshold voltage of only about 2 V and an extinction ratio higher than 35 dB were measured with 6.5 V applied.

All Optical Tunable Nematic Liquid Crystal Waveguide

All-optical control of a rectangular waveguide with liquid crystal is theoretically investigated. Light propagation is established with low input power control, that excites optical nonlinearity due to optically induced reorientational effect.

All-optical liquid crystal waveguide on silicon

In this paper we demonstrate nonlinear optical properties of a channel waveguide made of E7 nematic liquid crystal infiltrated in a SiO2/Si V-groove. Light in C-Band (1530-1565 nm), fiber coupled to the core of the liquid crystal waveguide, was optically modulated by the optical beam itself, with a power below 25 mW. A bias voltage was applied to induce a liquid crystal orientation over the Freedericksz threshold and a further director reorientation was obtained by increasing the optical beam. The effect of optical modulation for different applied voltages obtained experimentally was modelled including both opto and electro-optical effects.

All optical tunable nematic liquid crystal waveguide

All-optical control of a rectangular waveguide with liquid crystal is theoretically investigated. Light propagation is established with low input power control, that excites optical nonlinearity due to optically induced reorientational effect.

Nonlinear switching of near infrared light in liquid crystal on silicon channel waveguides

This paper reports on linear and nonlinear optical properties of channel waveguides made of micromachined SiO2/Si Vgrooves filled with nematic liquid crystal E7. Experiments demonstrate operation of the waveguides in the C-band (1530 - 1565 nm). Molecular reorientation of the NLC, induced either by an applied low frequency electric field or by the electric field of the light itself, changes the LC refractive index distribution then allowing the control of guided light. Design criteria and techniques of channel waveguides for both electro-optical and all-optical switching and modulation will be discussed. Experiments are presented where it is showed that light at 1550 nm, fiber-coupled to the LC waveguide is optically modulated by an optical beam with an input power below 25 mW. All-optical switching of a signal at 1510 nm with a contrast over 10 dB is also demonstrated by using a copropagating control signal at 1560 nm. A model of the waveguide is also presented able to explain linear and nonlinear experimental results.

Liquid crystal waveguide devices

In this paper low driving power linear and nonlinear optical waveguide devices using nematic liquid crystals as core are reported. Experiments and simulations show their behavior either as variable optical attenuators or as optical switches with extinction ratio in excess of 40 dB. All-optical modulation and switching is also shown using mW range optical power.