In this work, a technique for precise position control of individual transmission channels in a triple-cavity resonator
device is proposed. The resonator design is based on Si photonic crystal (PhC) and liquid crystal technologies. By filling
of the particular air grooves in one-dimensional, Si-Air PhC with nematic liquid crystal, an efficient coupled Fabry-
Pérot resonator can be realized in which a wide stop band is used for broad frequency channel separation and high out-of-
band reflection. By random tuning of the refractive index in all coupled cavities, a continuous individual tuning of the
central channel (or edge channels) up to 25% of the total channel spacing is demonstrated. Additionally, an approach
for precise controllable improvement of transmission up to 100% is demonstrated for the edge channels with decrease of
the channel spacing 1%. Based on the proposed design, a prototype triple-channel filter was fabricated on Silicon-On-Insulator platform and optimized to the desired operational mode.
Two-dimensional (2D) photonic crystal (PC) bars with 6 and 21 periods were fabricated by simultaneous photoelectrochemical
etching of macropores and trenches in a pre-patterned silicon wafer. The structures had square
lattice of cylindrical pores and were terminated by nonmodulated silicon pre-layers. The infrared reflection
spectra of the PC bars have been simulated using scattering matrix method. In order to take into account the
roughness of pore inner surface an additional silicon layer around the pores was introduced with a fitted complex
refractive index. A comparison between the simulated refection spectra and those obtained experimentally
demonstrates a satisfactory agreement in the region of secondary photonic band gaps.
The model of transformation of one-dimensional, high-contrast silicon photonic crystal (PC) into a Fabry-Pérot resonator
is considered. This transformation is achieved either by decreasing the number of periods up to 1.5 or the introduction of
optical defect in the ordinary multi-period PC while retaining a high modulation of the resonance peaks up to ~0.95. The
simultaneous use of maps of photonic band gaps (PBG) and transmission bands can predict the appearance or
disappearance of PBGs in the optical spectra as well as to determine their position and width depending on the order of
the band-gap (or stop-band) and the value of the filling fraction. The variation of the refractive index by 0.2 results in
significant shift of the resonance peaks of high order up to 10% of the frequency corresponding to the center of the peak.
This paper reports on investigation and possible applications of the optical elements based on one-dimensional (1D)
multi-component photonic crystal (PCs). The gap map approach and the transfer matrix method were used in order to
mathematically describe multi-component 1D PC structures. We have found that the introduction of the additional
regular layer into PC affects the properties of high-order PBGs, resulting in their vanishing in the certain range of the
wavelengths and the formation of wide regions of total transparency instead. Tuning the number, position and width of
these regions of total transparency in Si PCs has been demonstrated using the map of transmission bands. By analogy
with multilayer dielectric coatings the additional component in multi-component Si PCs can be considered as an
antireflection layer. The experimental results for the high-contrast multi-component PCs based on SiO2-Si-SiO2-Air
structure with wide transmission bands are demonstrated in this study. The suggested approach can also be applied to the
design of any micro- and nano- structured semiconductor or dielectric materials for application across wide
electromagnetic spectrum.
The results of a simulation of the optical properties of a silicon Fabry-Pérot resonator (with liquid crystal filler in the
cavity), operated on the shift of the interference bands in the infrared range are presented. The possibility of tuning the
reflection coefficient from 0 to 0.95 (or transmission coefficient from 1 to 0.05) by changing the refractive index by 0.1
in the cavity and using the stop-bands and resonance peaks of high order is demonstrated. The prototype Fabry-Pérot
resonators were fabricated by dry and wet etching of (100)Si and (110)Si. Some of the resonators were fabricated on a
silicon-on-insulator platform. A superposition of transmission peaks with reflection maxima, predicted from calculations,
was confirmed experimentally, using infrared microspectroscopy, with a temperature variation from 20 oC to 65 oC and
an applied electric field from 0V to 10V.
In this study, three-component One-Dimensional (1D) Photonic Crystal (PC) structures were investigated by modeling
them as two-component PCs with an additional regular layer. The Gap Map approach and the Transfer Matrix Method
were used in order to mathematically describe these structures. The introduction of a third component to a 1D PC allows
manipulation of the optical contrast to a high degree of precision by varying the thickness and refractive index of the
additional layer. It also partially reduces the area of the photonic band gaps (PBGs) on the gap map, leaving the
remainder of the PBG area unchanged from that of the gap map for the original, two-component, PC. Using this
approach to decrease the optical contrast in photonic crystals allows omni-directional bands to be obtained in highcontrast
periodic structures constructed from, for example, an array of silicon and air.
In this paper, the forbidden Photonic Band Gaps (PBGs) of a
one-dimensional Photonic Crystal (1D PC) with additional
regular layer, t for the constant value of the lattice constant A and at normal incident of light beam were investigated.
The additional regular layer was formed from both sides of the
high-refractive index layer H. The gap map approach and
the Transfer Matrix Method were used for numerical analysis of this structure. The limitation of filling fraction values
caused by the presence of t-layer was taking into account during calculations of the Stop-Band (SB) regions for threecomponent
PC. The red shift of SBs was observed at the introduction of t-layer to conventional two-component 1D PC
with optical contrast of N=3.42/1. The blue edge of the first PBG occupied the intermediate position between the blue
edges of SBs regions of conventional PCs with different optical contrast N. This gives the opportunity of tuning the
optical contrast of PC by introduction of the additional layer, rather than using the filler, as well as fine tuning of the SB
edge. The influence of the number of periods m and the optical contrast N on the properties of SBs was also
investigated. The effect of the PBG disappearance in the gap map and in the regions of the PBGs of high order was
revealed at certain parameters of the additional layer.
One dimensional periodic and non-periodic silicon photonic structures have been designed and fabricated on silicon-on-insulator
substrate for the investigation of the electro-tuning effect in composite system Photonic Crystal - Liquid
Crystal. The reflection spectra registered for non-periodic structures demonstrate the phase polarisation shift for bands
of high reflection, while for the periodic structure the shift of the photonic band gap edge was observed. Under an
applied electric field in the range from 2V to 10V, the shift of the polarised reflection spectra, caused by reorientation of
the LC director from planar to homeotropic alignment, has been obtained. A significant change in the refractive index
close to Δn=0.2, which is a characteristic feature for LC E7, has been achieved due to LC reorientation in all structures
just after LC infiltration. It was found that after switching-off the applied electric field the initial planar orientation of LC
molecules is not restored. This effect is related to weak anchoring of LC molecules to the silicon side-walls which
results in the transition of LC to the pseudo-isotropic alignment after the applied voltage is off. A relatively smaller (with
Δn=0.07), but highly reproducible electro-tuning effect was revealed during the LC reorientation from pseudo-isotropic
to homeotropic alignment. The shift of the edge of PBG by Δλ=0.16 or by Δλ/λ=1.6% in relative shift units was
observed in this case. The response time estimated under applied square shaped ac pulses of various frequencies was
found to be around 30 ms.
This paper is focused on the design, fabrication and characterization of the conventional and tunable photonic devices
based on grooved silicon, serving as one-dimensional (1D) photonic crystal. The advantages of these photonic structures
are as follows: the large refractive index contrast, in-plane moulding of the light flow, the possibility to fabricate a
composite photonic structures by filling the grooves with a different compounds and compatibility with current
semiconductor processing techniques. The optical properties of grooved Si structures were simulated using a transfer
matrix method and gap map method and have been verified experimentally using FTIR microscopy. The air spaces in
the basic silicon-air matrices were infiltrated with nematic liquid crystal E7. It is shown that the optical properties of the
obtained composite 1D photonic crystals can be tuned by means of electro- and thermo-optical effects. Such a structures
suit well for the various elements of the integrated optics and can serve as a building blocks for optical interconnects.
In this paper we describe a novel technique for the fabrication of aluminosilicate microfibres and microtubes which are
shown to act as optical cylindrical microresonators. The alumosilicate microfibres and microtubes were fabricated by
using vacuum-assisted wetting and filtration of silica gel through a microchannel glass matrix. The microfibres and
microtubes were studied using Scanning Electron Microscopy (SEM), micro-photoluminescence spectroscopy and
fluorescence lifetime imaging confocal microscopy. In the emission spectra of the micro-resonators we find very narrow
periodic peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors up to
3200. A strong enhancement in photoluminescence decay rates at high excitation power demonstrates the occurrence of
amplified spontaneous emission from a single microtube. These microtubes show a large evanescent field extending
many microns beyond the tube radius. Potential applications for these novel microresonators will be in the area of optical
microsensors for a single molecule detection of biological and chemical species, including anti-terrorism and defense
sectors.
We present a detailed study of the photonic modes in microtube cavity of ~ 7-8 μm outer diameter that can act as micron-scale optical cylindrical resonator. We demonstrate a new route to the fabrication of individual microtubes with the maximum length of 200 &mgr;m, using a vacuum assisted wetting and filtration through a microchannel glass matrix. The microtubes were studied using micro-photoluminescence spectroscopy and luminescence lifetime imaging confocal microscopy. In the emission spectra of the microresonators we find periodic very narrow peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors upto 3200 at room temperature. In order to identify the peaks in the observed mode structure, we have adopted the boundary-value solution to the problem of scattering of electromagnetic waves by a dielectric micro-cylinder. A strong enhancement in photoluminescence decay rates at high excitation power suggest the occurrence of amplified spontaneous emission from a single microtube. The evanescent field in these photonic structures extends a couple of micrometers into the surroundings providing the possibility for efficient coupling to an external photonic device.
We present the results of studies on small photonic microtube structures of less than 10 microns diameter. A new
technique based on vacuum assisted filtration is used to produce the microtube resonantors. Whispering gallery modes
are probed through the photoluminescence emission from the glass material forming the cavity. We observe resonances
with polarized emission having quality factors up to 3000. These microresonator structures exhibit a large evanescent
field which makes them interesting for potential photonic applications.
The orientation of nematic liquid crystal (LC) E7 on the surface of (111) silicon wafers and in the channels of grooved silicon structure has been investigated. Grooved Si is a periodical structure obtained by wet anisotropic etching of deep and narrow grooves in (110) Si using an alkaline solution. This structure can serve as a one-dimensional (1D) photonic crystal. Composite structures obtained from grooved Si infiltrated by LC are promising candidates for electro-optic application. LC E7 was infiltrated into the channels of grooved Si and into the bulk Si cells. IR spectroscopy and capacitance-voltage characteristics under DC electric field were applied to investigate LC orientation. It is shown that the E7 liquid crystal in grooved silicon exhibits a weak planar orientation with respect to the silicon walls.
Based on the relationship between spectrum of Einstein coefficient B(v) and optical response ε2meso for nanostructural materials with different types of size confinement (nanospheres, nanowires and nanowalls) we perform the numerical calculation and analysis of ε2meso and B(v) functions using dispersive effective field approach for a number of harmonic oscillators with different dispersive parameters (oscillator strength, decay factor and peak frequency). It has been shown that the spectral properties (peak position, peak intensity and half width) of ε2meso strongly depend upon the type of size confinement. In contrast, the spectrum B(v) is the same for all cases of composite media and therefore has a fundamental meaning. Differences in dielectric functions observed for all studied cases arise as a result of the variation in the local field factor for 3D, 2D and 1D size confinements.
Reflection spectra and photonic band gaps (PBGs) for periodic structures consisting of grooved Si infiltrated with nematic liquid crystals (LCs) E7 have been obtained experimentally and by simulation. Periodically grooved Si matrixes, with lattice periods ranging from 2 to 6 μm, were fabricated using wet anisotropic etching of (110) Si in an alkaline solution. It is shown theoretically that a substantial shift of PBGs can be obtained when there is a homogeneous alignment of the liquid crystal molecules with respect to the Si walls and, therefore, a change in the LC's refractive index from no to ne during elctro-tuning can be expected. This effect is smaller during thermo-tuning effect when refractive index changed from no to, ni (isotropic LC phase). The simulated reflection spectra are in good agreement with experimental data obtained with a Digilab FTS 6000 FTIR spectrometer in conjunction with a UMA 500 infrared microscope. A shift of the PBG's edges by a factor Δλ/λ=7% was predicted as a result of a thermo-tuning effect and ~10% as a results of electro-tuning effect.
Porous materials in general have received great attention from the last century. The development of new porous materials and the preparation of new composites based on porous materials is a subject of interest. The development of porous silicon based optical composite materials opened up new ways of incorporating optically active sol-gel materials into porous silicon. High purity silica optical fibres allow the most rapid and efficient data transmission. The objective of this work is to develop micro-channel glass / porous silicon-rare earth doped xerogel and glass composites, which would serve as compact optical amplifiers and delay line devices. Micro-channel glass / porous silicon-xerogel composites have been prepared by incorporation of sol-gel prepared from tetraethoxysilane, aluminium iso-propoxide and europium chloride into the porous matrix. Both xerogel and glass composites have been studied by various techniques such as FTIR, micro-Raman, photoluminescence spectroscopy, EDX and Scanning Electron Microscopy (SEM).
Grooved silicon (gr-Si) structures with a period of few micrometers, which were formed by anisotropic etching of (110) Si wafers, have been investigated by means of broad band infrared (IR) and submillimeter transmission spectroscopy. In the spectral region of 50-1000 μm the results are well explained by an effective medium model, which predicts a strong birefringence with a difference between refractive indices for ordinary and extraordinary beams to be about 0.73-0.77. The IR transmission of gr-Si in the range from 1 to 30 μm is strongly influenced by light scattering. The experimental results measured in the region 1-5 μm can be understood in the terms of the geometric optics.
The importance of sensitive monitoring of changes in Raman spectra in particular for microelectronic applications is discussed here. We explore the practicality of using a data-scattering method to analyse Raman spectra, and to establish the dependence of changes observed in all the spectral function characteristics on the parameters of data-scatter such as scatter closeness and scatter radii using "Trace Miner" software. In addition to the analysis performed on model data, analysis on experimental Raman data is also discussed. The sensitivity of the approach is fully appreciated.
Transparent polycrystalline diamond films with grain size ranging from a few tens to hundreds of nanometres were prepared on fused silica substrate by Microwave Chemical Plasma Vapour Deposition method (MPCVD). The new technique, called alternating nanodiamonds injection, was applied for substrate pretreatment. It was demonstrated that nanodiamonds injected on fused silica substrate serve as nucleation centres and make possible an increase in nucleation density to 1010 cm-2. The influence of MPCVD parameters such as methane concentration, total pressure and substrate temperature on the crystalline structure and optical properties of diamond films were investigated by using micro-Raman spectroscopy and scanning electron microscopy, transmittance and reflectance measurements in the wavelength range of 400-1000 nm. Under appropriate MPCVD parameters, diamond films with optical transmission ~70% from 650 to 1000 nm and high content of diamond phase were fabricated.
In this study, Strained silicon Quantum Wells (QW) were characterised using a variety of micro-scopical techniques. Among the techniques used were Transmission Electron Microscopy (TEM), Elemental Electron Loss Spectroscopy (EELS), and micro-Raman spectroscopy. A combination of these methods facilitates investigation of the structure, the strain, and the dislocations present in such materials. Both conventional and High Resolution Transmission Electron Microscopy (HRTEM) are used to analyse strained silicon quantum wells (QW). These techniques allow for structure analysis at the atomic level. Elemental Electron Loss Spectroscopy (EELS) is used in tandem with other analytical techniques in order to give a quantitative analysis of the structures. The presence of various layers is independently verified using EELS, while layer depth and concentration profiles are also established. Relaxation levels in the virtual substrate as well as the strain in Si quantum wells are calculated using Raman spectroscopy.
The paper investigates from the perspective of computer science the phase coherence theory (PCT) and phase coherent data-scatter (PCD-S). These techniques were originally developed for the area of optical tensiographic data mining and analysis but have a more general appplication in data mining. These develoments have recently been augmented with the engineering of a software toolkit called TraceMiner. Although the toolkit was originally devised for tensiography it was developed to perform as a generic data mining and analysis application with PCT, PCD-S and a range of other data mining algorithms implemented. To date the toolkit has been utilised in its main application area, tensiography, but has also been applied to UV-visible spectroscopy. This work presents a critical investigation of the general utility of PCT, PCD-S and the toolkit for data mining and analysis. A new application of PCT and the TraceMiner software toolkit to Raman spectroscopy is presented with discussion of the relevant measures and the information provided by the toolkit. This provides more insight into the generic potential of the techniques for data mining. The analysis performed on theoretical Raman data is augmented with a study of experimental Raman data. Raman spectroscopy is used for composition and fault detecton analysis in semiconductor surfaces. Finally, the utility of the PCT technique in comparison with traditional Raman spectroscopy methods is considered together with some more general applications in the field of imaging and machine vision.
Periodic structures of grooved Si with lattice constants A = 2 - 4 µm, having the horizontal modulation of the refractive index, n, and acting as the 1D Photonic Crystal (PC) in the middle and far IR range (5-50 µm), have been fabricated by means of wet anisotropic etching of (110) oriented single crystalline silicon. The “gap maps” for both the empty matrices of periodically grooved Si and the composites infiltrated with liquid crystal (LC) of the average refractive index n=1.6 have been calculated. These maps display the frequency regions of photonic band gaps (PBGs) as a function of the filling factor Dsi/A and simplify the design of 1D PC structures for user-specified wavelength range. FTIR measurement revealed wide stop bands in the reflection and transmission spectra. Infiltration of the periodically grooved Si with the nematic liquid crystal E7 results in a shift of the main band gap to the higher wavelengths and in the consequent changes in the secondary stop bands. It is shown that polarized spectra of grooved Si infiltrated with LC allows determination the refractive index of the LC and the orientation of its molecules.
The reflection spectra of composite materials on the base of grooved silicon and grooved silicon infiltrated with nematic liquid crystal (LC) have been calculated using the optimal parameters of a grooved silicon matrix suitable for the infrared range. The grooved silicon structures with different lattice constants (A=16, 12, 8 and 4 mm) have been designed and prepared. An important parameter of these structures is the thickness of the silicon walls (DSi). This has
been obtained using simulations of the spectra. This parameter was used for further analysis of the spectra of composite material grooved Si-LC. The experimental reflection is reaching of 65% in maximum (with signal modulation from maximum to minimum up to 55%) for the composite structures with a small number of lattice periods that makes these structures very perspective with a potential applications. The analysis of the polarised infrared spectra of Si structures infiltrated with LC allows one to determine the orientation and the refractive index (NLC) of the liquid crystal. For the samples with a distance between Si walls of 6-10 mm, it was found that the refractive index was NLC=~ 1.5 for polarised light and NLC 1.5 for s-polarised light. This leads to the conclusion on the planar orientation of liquid crystal molecules with respect to the Si walls. For the samples with distance between Si walls less than 3 mm, a homeotropic alignment of liquid crystal molecules has been found. Micro-Raman spectroscopy has been applied for analysis of stress in such Si structures. The maximum stress of about 2 GPa was obtained on the top of Si walls (under Si dioxide layer).
The discovery of room temperature photoluminescence in porous silicon has opened up a range of applications for this material in new areas such as optical, photodetector, photovoltaic, micromachine and sensors. For this reason there have been significant efforts in recent years directed at modification of silicon surfaces via formation of Si-C and Si-O-E (E = H, C, N) bonds on the silicon surfaces. However, research on bonding of metallorganic fragments to the silicon surface is scant. The main objectives of our work are to develop and investigate new ways of specific chemical bonding of selected metallorganic compounds to the Si surface and to prepare new types of silicon-based materials. New metallorganic composites have been developed on macro- and micro- porous silicon surfaces. The silicon surfaces have been effectively modified using inorganic and organometallic chemistry approaches. The work includes: (i) preparation and investigation of Cl-, HO-, and Cp- modified porous Si-surfaces; (ii) preparation and characterisation of iron oxide layers
on porous silicon; (iii) characterization of metallorganic layers on porous silicon by FTIR, EDX and Scanning Electronic Microscopy (SEM). There are strong possibilities that those composite materials will have a wide range of applications in nano-technology and optoelectronics.
In this work, SiO2 and fluorine and phosphorous doped SiO2 thin films are investigated using FTIR and Raman
techniques. FTIR spectroscopy was performed at normal and oblique incidence of the probe beam in transmission and reflection modes. The effect of polarisation and angle of incidence of the probe beam is examined for the case of reflection mode. Infrared spectra taken from doped oxides show that the structure changes with the passage of time.
Alternate methods to calculate the thickness of the doped film are therefore discussed. Infrared spectra of electron beam evaporated oxides give valuable information on their structure and water content. The porosity is calculated for these samples. Finally, micro-Raman spectroscopy is used to measure the fluorine content in a device structure.
A number of thin dielectric films deposited onto aluminated glass substrates and onto the materials transparent in the IR
range (silicon, KRS-5 and CsI) were investigated using infrared transmission and reflection-absorption techniques. The
application of these techniques to thin dielectric films at normal and oblique incidence of light allows the observation of
both the longitudinal and transverse optical phonons. The longitudinal (LO)-transverse (TO) optical phonons splitting is
analysed in terms of a dispersive local field effect. It has been shown that the results of LO-TO splitting obtained from
dispersive local field effect are in a good agreement with the results obtained from the dynamical theory of crystalline
lattices.
Micro-Raman spectroscopy was used in this study for the analysis of the influence of process conditions on the strain and stress in macro-porous silicon (ma-PS) layers. As expected, it was found that oxidation results in significant wafer bending, depending on the layer porosity. The magnitude of stress of about 0.33 Gpa was found for ma-PS sample with lattice constant of 4 mm while for sample with the lattice constant of 12μm it was only 0.175 GPa. Dissolution of the oxide layer restores the flatness of the samples after the first oxidation. Repetition of the oxidation cycles leads to a 'memory effect', as the residual deformation increases. The results are consistent with results obtained for similar samples using X-ray diffractometry and topography and curvature measurements.
In this work, pyrolytical carbon and C-SixCy-SiC coatings were deposited by chemical vapour deposition (CVD) in a 'Cold Wall' reactor. The C/C samples from 'Schunk Kohlenstofftechnik GmbH', Germany were used as substrates. The pyrolytical carbon coatings were obtained by CH4 cracking at 1200-1300°C. SixCy and SiC coatings were deposited
from SiCl4/H2 mixtures by varying the H2/SiCl4 ratio (a). Micro-Raman spectroscopy and X-ray diffraction have been used to determine the order grade for pyrolytical carbon coatings and to investigate the structure and composition of SiC coatings depending on the deposition conditions. In particular, the analysis of Raman spectra of carbon films in the
region of 1200-1800 cm-1 allowed the determination of crystal size in a film, which varied from 2.6 to 8.5 nm
depending on a. The presence of a strong narrow band at 2712 cm-1 in the second order Raman spectra region (2300-
3400 cm-1) indicated a high degree of perfection of the crystalline lattice and an onion like structure in some of the
carbon films. XRD investigation of the SiC-peak showed a shift in frequency and a reduction in intensity when compared to the substrate. The peak shift corresponds to a crystal-geometric grading of the coating.
A detailed study of the dependence of the vibrational modes in rapid thermal chemical vapour deposited Si1-x-yGexCy on substitutional carbon concentration has been undertaken. The difficulty in incorporating substitutional carbon in these alloys with concentration higher than a few tenths of an atomic percent is well known. It is shown that simultaneous analysis of X-ray diffraction, infrared absorption and Raman scattering measurements can be used to determine the
fraction of substitutional carbon from the total carbon content. The frequency shifts of the carbon local modes and the Si-Si modes have been studied in addition to the intensity dependence of the former. The evolution of the carbon satellite peaks and their dependence on total carbon concentration has also been studied. Good numerical agreement with other previously published results has been obtained.
The application of precision grinding for the formation of a silicon diaphragm is investigated. The test structures involved 2-6 mm diam diaphragms with thicknesses in the range of 25-150 μm. When grinding is performed without supporting the diaphragm, bending occurs due to nonuniform removal of the silicon material over the diaphragm region. The magnitude of bending depends on the final thickness of the diaphragm. The results demonstrate that the use of a porous silicon support can significantly reduce the amount of bending, by a factor of up to 300 in the case of 50 μm thick diaphragms. The use of silicon on insulator (SOI) technology can also suppress or eliminate bending although this may be a less economical process. Stress measurements in the diaphragms were performed using x-ray and Raman spectroscopies. The results show stress of the order of 1×107-1×108 Pa in unsupported and supported by porous silicon diaphragms while SOI technology provides stress-free diaphragms. Results obtained from finite element method analysis to determine deterioration in the performance of a 6 mm diaphragm due to bending are presented. These results show a 10% reduction in performance for a 75 μm thick diaphragm with bending amplitude of 30 μm, but negligible reduction if the bending is reduced to <10 μm.
Fourier transform infrared spectroscopy of a ferroelectric liquid-crystalline material: 4-(3)-(S)- methyl-2-(S)-chloropentanoyloxy-4'-octyloxy-biphenyl has been investigated in the wavenumber range 450 - 4000 cm-1 for various temperatures and as a function of direct bias voltage in its SmC* phase. Samples prepared in both homeotropic and homogeneous alignments have been studied. The order parameter was calculated for several isolated IR vibrations which are characteristic of different parts and orientations of molecules. The dependence of the molecular tilt angle on direct bias voltage and temperature has similar characteristics to those obtained from electro-optic measurements.
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