Use this URL to cite or link to this record in EThOS:
Title: Enhancement of liquid crystal electro-optic effects using Fabry-Perot cavities
Author: Choi, W. K.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
Availability of Full Text:
Full text unavailable from EThOS.
Please contact the current institution’s library for further details.
This dissertation describes the investigation of three novel schemes for the enhancement of fast liquid-crystal (LC) electro-optic effects using Fabry-Perot (F-P) cavities. The objective is to develop low voltage and high speed electro-optic modulators for use in free-space optical interconnects in silicon Very-Large-Scale-Integrated (VLSI) electronic systems. These optical interconnects are under active development as a potential technology to overcome the limitations associated with electrical interconnects. The prime candidate as the LC electro-optic effect for this application is the electroclinic effect associated with Smectic A * LCs (SmA*LCs) due to its potentially very fast response time in the order of nanoseconds. However, this effect is often very small which leads to either low contrast ratios or low throughputs using the conventional structures with a LC between crossed polarisers. Hence it is proposed to enhance this effect using F-P cavities as has been done for other small electro-optic effects such as those used in Multiple Quantum Wells. Due to the lack of refractive index change experienced by the light at normal incidence under applied electric fields, SmA*LCs cannot be used in F-P cavities directly to give intensity modulation. Two indirect techniques have been developed during this research to overcome this obstacle. The first technique developed involves the use of a Compound-Variable-Retarder (CVR) consisting of two independent quarter-wave plates (one being a SmA*LC) inside an asymmetric F-P (or Gires-Tournois) cavity which is placed between crossed polarisers. The CVR is used in order to induce an analogue phase change at normal incidence. The second technique developed involves the use of oblique incidence in order to induce an analogue change of the effective extraordinary refractive index experienced by the incident light. The structure in this case consists simply of a SmA*LC layer inside a F-P cavity. Original proof-of-principle experiments have been developed and have verified both proposed schemes, which can offer high enhancement and have potential for free-space optical interconnects.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available