Solc Filter Research Articles

Polarized optical filtering from general linearly twisted structures

It is shown that a stack of linearly twisted birefringent plates with arbitrary successive twist angle acts as a spectral filter assuming the total twist equals an odd integer of π/2, and each plate acts as a full wave plate. The classical fan Solc filter is shown to be a very special case of the present concept. Based on this finding, spontaneously twisted structures analogous to the twisted liquid crystals and helical sculptured thin films can basically act as polarization filters if their molecular or nano-rod thickness and the local birefringence satisfy the full waveplate condition. Giving a certain number of full wave plates it is shown that there are many ways to arrange their successive twist and get the same transfer function.

Photovoltaic effect in a periodically poled lithium niobate Solc-type wavelength filter

We report a non-field-applied Solc-type filter constructed by a periodically poled lithium niobate (PPLN). By comparing two types of PPLN Solc filter setup, both theoretically and experimentally, we have proved that without external field applied, it is the photovoltaic effect that introduces pass peak in the PPLN band filter.

Duty cycle dependence of a periodically poled LiNbO_3-based electro-optic Solc filter

We demonstrate that the performance of a periodically poled LiNbO3- (PPLN-) based electro-optic Solc filter is dependent on the duty cycle of the crystal. This may limit the performance of the device for applications such as add-drop filtering and switching, owing to the deterioration of the extinction ratio. It is shown that by adding a retarder to the Solc filter it is possible to improve the extinction ratio; thus the dependence of the filter on the duty cycle can be reduced. Using Jones calculus, we analyzed the effect of a variable retarder that can also be rotated on the extinction ratio. We experimentally observed a 6 dB increase in the extinction ratio when we used a half-wavelength retarder.

Nearly-off-axis transmissivity of Solc birefringent filters.

The characteristics of light propagating near the axis of a birefringent filter are studied. A generalized formulation to describe the nearly-off-axis transmissivity of a Solc birefringent filter is derived. On this basis, the polarization conoscopic figures of Solc filters with different numbers of birefringent plates are simulated. Furthermore the variation of spectral transmission with angle of incidence is analyzed, and the field-of-view transmissivity and the spectral transmissivity averaged with respect to the spread of incident light are given. Primary experiments for verification are also demonstrated.

Tunable birefringent filters - optimal iterative design

More than 50 years ago, B. Lyot and later on I. Solc introduced new types of optical filters called birefringent filters. Such filters take advantage of the phase shifts between orthogonal polarization to obtain narrow band filters. It requires birefringent wave plates for introducing phase retardation between the two orthogonal components of a linearly polarized light that correspond to the fast and slow axes of the birefringent material. In this paper we present new methods and architectures that generalize the Lyot-Ohman and Solc filters for optimally synthesizing an arbitrary all-optical filter by defining an error metric and minimizing it with simulated annealing. We also suggest the use of the electro-optic effect for controlling the retardation of individual elements that make up the tunable filter. Such a filter could be used for instance for realizing a dynamically tunable optical add/drop multiplexer in a telecommunication system.

A Method of Generating Full Color in a Liquid Crystal Display Using Birefringent Filters

Color generation in a typical liquid crystal device (LCD) is usually done via an array of absorptive color filters placed over the LC subpixels. These filters offer at best 33% transmission resulting in dark displays and the need for high intensity backlights. In this paper we clearly explain a new method of color generation based on a polarization interference filter (PIF) scheme called the Solc filter. The design offers high throughput and chromaticity due to its non-absorptive nature. The design is based on work done by ColorLink Inc. and is extended to show possible use in a display device.

P‐73: A Method of Generating Full Color LCD Using Birefringent Filters in a Stacked Design

AbstractWe discuss the design and performance of a full color transmissive display based on the folded Solc filter design. Sharp et. al. suggested the use of a modified Solc filter as a colorswitch and for use as a display device. Del Pico suggested its use as a direct view device using plastic substrates and LCP's to solve some parallax issues. However no details of its operation were given. The design incorporates three individual stacks each responsible for producing RGB without the use of color filters, this offer high color purity and brightness along with the promise of low power consumption. In this paper the design of such a system is considered in detail.

Omnidirectional reflection from anisotropic periodic dielectric stack

It is shown that Solc filter structure under certain conditions of the alternating anisotropic layers acts as a perfect reflector at all angles, any polarization and over a wide spectral range thus can act as a photonic band gap structure. Near this behavior a total 90° polarization rotation is obtained upon reflection over a large range of angles or wavelengths.

Sculptured thin film Solc filters for optical sensing of gas concentration

The viability of sculptured thin film (STF) implementations of Solc fan and folded filters for optical detection and determination of gas concentration is established. A nanoscopic–to–continuum model is devised for predicting the electromagnetic (optical) response of a STF Solc filter whose void regions are filled with a chemically non–reacting gas. Ultra–narrow band–pass features in the transmission spectrum are shown to shift with the gas concentration.

Linear periodic and quasiperiodic anisotropic layered media with arbitrary orientation of optic axis—A numerical study

We study numerically the linear properties of periodic and quasiperiodic anisotropic layered media. Each anisotropic slab can have arbitrary orientation of optic axis. We apply the general numerical code to recover the known results for solc filters. We propose novel periodic structures where the location and width of the gaps can be controlled easily. We also study the transmission properties of a Fibonacci sequence of anisotropic layers and show the interesting features like self-similarity and scaling.

A narrow-band interference filter with photorefractive LiNbO3

A narrow-bandwidth interference filter has been developed using volume holography in photorefractive LiNbO3 crystals. The device works as a Bragg reflector using a volume hologram recorded, fixed and developed in a LiNbO3 sample. With a 2 mm thick LiNbO3 plate the following performances have been achieved: a peak reflectivity above 32%, a full-width at half-maximum bandwidth below 0.05 nm, an angular field of view of about 3 degrees and a peak wavelength of 518.45 nm (for green Ar laser writing wavelength). These performances compare well with that exhibited by the conventional Lyot-Ohman and Solc filters. A complete explanation of the fabrication procedure is given, including practical details needed for producing such an efficiency with fixed holograms in LiNbO3.

The Poincare sphere: isolated and real trajectories describing the state of polarization

For a given crystal optics device with polarization properties there are two kinds of trajectories that can be drawn on the Poincare sphere, namely the isolated and real trajectories. Using Stokes vectors and Mueller matrices, the parametric equations that represent the evolution of the state of polarization due to the passage of light through polarizers and optical components exhibiting linear or circular birefringence are given. The geometrical trajectories given by these equations, are useful for analyzing or designing optical birefringent networks and they are easy to obtain with today's computer software. An example of their application in the analysis of a Solc filter is given.

Single mode fiber tunable filter based on Faraday effect

The tunable Solc filter can be realized with a single mode fiber coil between two orthogonal polarizers and a uniform magnetic field. The filter the authors built has a band pass centered at 492 nm and a band width equal to 13 nm. The spectral transmittance of this filter is tunable through the intensity of the magnetic field.

Fabry–Perot/Šolc filter with distributed Bragg reflectors: a narrow-band electro-optically tunable spectral filter

A new narrow-band (typically 0.01-nm) spectral filter called the Fabry–Perot/Solc filter, which combines the characteristics of the Fabry–Perot etalon and the folded Solc filter, was introduced recently [ J. Opt. Soc. Am. A4, 1720 ( 1987)]. The design of the Fabry–Perot/Solc filter is extended to include narrow-band end reflectors to produce high-finesse spectral filters. The narrow-band end reflectors can be implemented as distributed Bragg reflectors (DBR’s), thus permitting tailoring of the spectral characteristics of the Fabry–Perot/Solc filter. Sample designs are presented, including one filter with an effective finesse of 5420. Possible uses for the Fabry–Perot/Solc filter with DBR’s are discussed, and it is compared with the narrow-band electro-optically tunable notch filter proposed by Lytel Lipscomb [ Appl. Opt.25, 3889 ( 1986)].

Practical design and manufacture of equivalent SOLC filters in single-mode fiber

The significant intrinsic birefringence Bi (deg./m) is taken into consideration when the design procedures for fiber equivalent Solc filters are devised. The filter designed has a full-width 9.5 nm at half maximum at a center wavelength of 570 nm, with a principal band shift of only 15 nm from the scheduled value. The equivalent Solc filter now proves to be tunable with temperature, which is experimentally demonstrated.

Transmission characteristics of the birefringent filter system, where a retarder-rotator combination is used at each stage

Polarizers and retarders have long been known as the basic building blocks of Lyot and Solc filters. Recently the use of an optically active medium along with polarizers and retarders has been found to be useful for modifying the transmission characteristics of the birefringent filter system. In this paper, the effect of using an optically active medium as the interstage element of a Solc filter has been studied. The idea of a birefringent band suppression filter has been found and the tuning procedures of these fixed-type filters have also been discussed.

Fibre-optic Solc filter for use in Raman amplification of light

Fibre-optic Solc filters, in which five consecutive fibre coils are tilted with respect to each other, have been fabricated. The wavelength of maximum transmittance is designed to coincide with 1.24 μm wavelength, and the half-power bandwidth is 61 nm. To show the feasibility of the fibre-optic Solc filter in Raman amplification of light, the third Stokes line (λ=1.24 μm) of 1.06 μm Nd:YAG laser light from a silica fibre was successfully extracted, while the pump light and other Stokes lines were suppressed below −13 dB.

Harmonic response of a tunable Solc filter

The spectral evolution and transitional behavior of the odd harmonic windows in a broadly tuned electrooptic Solc filter are described theoretically and demonstrated experimentally. We show how the fundamental and all the odd harmonic passbands split and eventually merge in pairs with nearest neighbors to become even harmonics of the fundamental λf as the principal pass wavelength λp is tuned from λp = λf to λp ≫λf.

A Mixed Solc Birefringent Filter

In this article, the transmission characteristics of new mixed birefringent filter have been studied. The term ‘mixed’ is used because in this filter both linear and circular birefringence are utilized for shaping its transmission function. The filter has a so called ‘lossless core’, consisting of alternate rotators and retarders, and two linear polarisers at the two ends. Because of the similarity of the proposed mixed birefringent filter with the fan type Solc filter, it has been given the name ‘Mixed Solc Birefringent Filter’ (MSBF).

Tunable Birefringent Filters

This article reviews the types and capabilities of birefringent filters. The general operating principles of Lyot (perfect polarizers), partial polarizing, and Solc (no internal polarizers) filters are introduced. Appropriate techniques for tuning each filter type are presented. Field of view of birefringent filters is discussed and is compared to Fabry-Perot and interference filters. The transmission and throughput advantages of birefringent filters are shown. Finally, the current state of the art in practical filters is reviewed.