Showing papers on "Optical filter published in 2012"
Patent•
26 Jun 2012TL;DR: In this paper, an optical indicia reading terminal including a housing, a multiple pixel image sensor disposed within the housing, an imaging lens assembly configured to focus an image of decodable indicia on the image sensor, an optical bandpass filter disposed in an optical path of light incident on the sensor, and an analog-to-digital (A/D) converter configured to convert an analog signal read out of an image sensor into a digital signal representative of the analog signal.
Abstract: Methods for using an optical indicia reading terminal including a housing, a multiple pixel image sensor disposed within the housing, an imaging lens assembly configured to focus an image of decodable indicia on the image sensor, an optical bandpass filter disposed in an optical path of light incident on the image sensor, an analog-to-digital (A/D) converter configured to convert an analog signal read out of the image sensor into a digital signal representative of the analog signal, and processor configured to output a decoded message data corresponding to the decodable indicia by processing the digital signal.
341 citations
TL;DR: In this paper, a theoretical optimization process for designing nanofluid-based filters for hybrid solar photovoltaic/thermal (PV/T) applications is described.
Abstract: Optical filters are essential in a wide range of applications, including optical communications, electronics, lighting, optical sensors and photography. This article presents recent work which indicates that optical filters can be created from specialized nanoparticle suspensions. Specifically, this article describes a theoretical optimization process for designing nanofluid-based filters for hybrid solar photovoltaic/thermal (PV/T) applications. This particular application is suitable because nanofluids can be utilized as both volumetric solar absorbers and flowing heat transfer mediums. The nanofluid filters described in this work compare favorably with conventional optical filters for five photovoltaic (PV) cell alternatives: InGaP, CdTe, InGaAs, Si, and Ge. This study demonstrates that nanofluids make efficient, compact and potentially low-cost, spectrally selective optical filters.
333 citations
TL;DR: In multicomponent metallic glasses, it is demonstrated that diffusion and secondary (β) relaxation are closely related, and cooperative stringlike atomic motion plays an important role in both processes.
Abstract: We demonstrate the output characteristic of broadband parametric amplification of incoherent light pulses in a 355-nm pumped degenerate picosecond optical parametric amplification with either saturated or unsaturated amplification. The optical parametric amplifier is seeded by the fluorescence generated in a solution of pyridine-1 dye in ethanol. With the saturated amplification, we can obtain high energy incoherent light pulses, whose full width at half maximum bandwidth varies from 16 nm to 53 nm for the different phase matching angles near degeneracy. Moreover, the unsaturated bandwidth of the amplified pulses fits well to the calculated result at degeneracy. Selecting s-polarized fluorescence with a Glan-Taylor prism, the maximum bandwidth of the amplified fluorescence is found to be 59 nm for a purely s-polarized seed. The maximum output energy is 0.67 mJ for the optical parametric amplifier. By using an optical filter and compressor, the generated high energy incoherent light has great potential as the incoherent pump, signal or idler wave of a parametric down-conversion process, so that a wave with a high degree of coherence can be generated from an incoherent pump light.
182 citations
TL;DR: In this article, an optically tunable optoelectronic oscillator (OEO) with a wide frequency tunable range incorporating a tunable microwave photonic filter implemented based on phase-modulation to intensity modulation conversion using a phase-shifted fiber Bragg grating (PS-FBG) is proposed and experimentally demonstrated.
Abstract: An optically tunable optoelectronic oscillator (OEO) with a wide frequency tunable range incorporating a tunable microwave photonic filter implemented based on phase-modulation to intensity-modulation conversion using a phase-shifted fiber Bragg grating (PS-FBG) is proposed and experimentally demonstrated. The PS-FBG in conjunction with two optical phase modulators in the OEO loop form a high-Q, wideband and frequency-tunable microwave photonic bandpass filter, to achieve simultaneously single-frequency selection and frequency tuning. Since the tuning of the microwave filter is achieved by tuning the wavelength of the incident light wave, the tunability can be easily realized at a high speed. A theoretical analysis is performed, which is verified by an experiment. A microwave signal with a frequency tunable from 3 GHz to 28 GHz is generated. To the best of our knowledge, this is the widest frequency tunable range ever achieved by an OEO. The phase noise performance of the OEO is also investigated.
178 citations
TL;DR: In this article, a photonic assisted broadband and high-resolution radio-frequency (RF) channelization scheme based on dual coherent optical frequency combs (OFCs), regular optical de-muxes, and I/Q demodulators is analyzed and experimentally demonstrated.
Abstract: In this paper, a novel photonic-assisted broadband and high-resolution radio-frequency (RF) channelization scheme based on dual coherent optical frequency combs (OFCs), regular optical de-muxes, and I/Q demodulators is analyzed and experimentally demonstrated. The use of two coherent combs avoids precise optical alignment, and a numerical filter in digital signal processor (DSP) enables an ideal rectangular frequency response in each channel without any ultranarrow optical filters. Besides, due to the use of I/Q demodulators, ambiguous frequency estimate in direct detection is avoided. By using two coherent OFCs with the free spectrum range (FSR) of about 40 GHz, we experimentally demonstrate the channelization scheme with seven channels, 500-MHz channel spacing, and frequency coverage from 3.75 to 7.25 GHz. The input RF tones are accurately downconverted to an intermediate frequency (IF) with a maximum frequency error of 125 kHz. Meanwhile, the channel frequency response and crosstalk of the scheme are also evaluated experimentally.
126 citations
TL;DR: High-speed operation dominated by just optomechanical effects of reconfigurable optical filters is demonstrated, and independent control of mechanical and optical resonances of the authors' structures is demonstrated.
Abstract: Nanoscale optomechanical systems offer a route to using optical forces for a range of devices based on photonic structures. Deotare et al. present a reconfigurable optical filter based on coupled silicon photonic crystal nanobeam cavities that can overcome thermo-optic effects at high frequencies.
121 citations
TL;DR: It is shown that the main benefits of a LVOF-based microspectrometer are in case of implementation in a narrowband application.
Abstract: In this paper the concept of a microspectrometer based on a Linear Variable Optical Filter (LVOF) for operation in the visible spectrum is presented and used in two different designs: the first is for the narrow spectral band between 610 nm and 680 nm, whereas the other is for the wider spectral band between 570 nm and 740 nm. Design considerations, fabrication and measurement results of the LVOF are presented. An iterative signal processing algorithm based on an initial calibration has been implemented to enhance the spectral resolution. Experimental validation is based on the spectrum of a Neon lamp. The results of measurements have been used to analyze the operating limits of the concept and to explain the sources of error in the algorithm. It is shown that the main benefits of a LVOF-based microspectrometer are in case of implementation in a narrowband application. The realized LVOF microspectrometers show a spectral resolution of 2.2 nm in the wideband design and 0.7 nm in the narrowband design.
114 citations
TL;DR: A high resolution optical vector network analyzer (OVNA) implemented based on a wideband and wavelength-tunable optical single-sideband (OSSB) modulator is proposed and experimentally demonstrated.
Abstract: A high resolution optical vector network analyzer (OVNA) implemented based on a wideband and wavelength-tunable optical single-sideband (OSSB) modulator is proposed and experimentally demonstrated. The OSSB modulation is achieved using a phase modulator and a tunable optical filter with a passband having two steep edges and a flat top. Wideband and wavelength-tunable OSSB modulation is achieved. The incorporation of the OSSB modulator into the OVNA is experimentally evaluated. The measurement of the magnitude and phase response of an ultra-narrow-band fiber Bragg grating (FBG) and that of the stimulated Brillouin scattering (SBS) in a single-mode fiber is performed. A measurement resolution as high as 78 kHz is achieved.
112 citations
TL;DR: The XMM-Newton Serendipitous Ultraviolet Source Survey (XMM-SUSS) as mentioned in this paper is a catalogue of ultraviolet (UV) sources detected serendipitously by the optical monitor on board the XMM−Newton observatory.
Abstract: The XMM–Newton Serendipitous Ultraviolet Source Survey (XMM-SUSS) is a catalogue of ultraviolet (UV) sources detected serendipitously by the Optical Monitor (XMM-OM) on board the XMM–Newton observatory. The catalogue contains UV-detected sources collected from 2417 XMM-OM observations in one to six broad-band UV and optical filters, made between 2000 February 24 and 2007 March 29. The primary contents of the catalogue are source positions, magnitudes and fluxes in one to six passbands, and these are accompanied by profile diagnostics and variability statistics. XMM-SUSS is populated by 753 578 UV source detections above a 3σ signal-to-noise ratio threshold limit which relate to 624 049 unique objects. Taking account of substantial overlaps between observations, the net sky area covered is 29–54 deg2, depending on UV filter. The magnitude distributions peak at mAB = 20.2, 20.9 and 21.2 in UVW2 (λeff = 2120 A), UVM2 (λeff = 2310 A) and UVW1 (λeff = 2910 A), respectively. More than 10 per cent of the sources have been visited more than once using the same filter during XMM–Newton operation, and >20 per cent of sources are observed more than once per filter during an individual visit. Consequently, the scope for science based on temporal source variability on time-scales of hours to years is broad. By comparison with other astrophysical catalogues we test the accuracy of the source measurements and define the nature of the serendipitous UV XMM-OM source sample. The distributions of source colours in the UV and optical filters are shown together with the expected loci of stars and galaxies, and indicate that sources which are detected in multiple UV bands are predominantly star-forming galaxies and stars of type G or earlier.
106 citations
TL;DR: In this paper, an angle-tuned guided-mode resonance color filter is experimentally demonstrated, which exhibits blue, green, and red color responses at incident angles of 8 $^{circ}$, 20 $^{\circ}µ, and 35 $^µ$, respectively.
Abstract: A new angle-tuned guided-mode resonance color filter is experimentally demonstrated. The device is designed using numerical methods and patterned using laser interferometric lithography. It consists of a 55-nm-deep silicon nitride and air diffraction grating with a 270-nm grating period along with a 110-nm-thick silicon nitride waveguide layer deposited on a glass substrate. The fabricated filter exhibits blue, green, and red color responses at incident angles of 8 $^{\circ}$ , 20 $^{\circ}$ , and 35 $^{\circ}$ , respectively. It has a bandwidth of 10 nm with efficiency near 90%.
104 citations
Patent•
01 Jun 2012TL;DR: In this article, an optical filter, a solid-state imaging element and an imaging device lens which contain a specific near infrared ray absorbing dye dispersed in a transparent resin having a refractive index of 1.54 or more was presented.
Abstract: The present invention relates to an optical filter, a solid-state imaging element and an imaging device lens which contain a near infrared ray absorbing layer having a specific near infrared ray absorbing dye dispersed in a transparent resin having a refractive index of 1.54 or more, and also relates to an imaging device containing the solid-state imaging element or the imaging device lens. The near infrared ray absorbing layer has a transmittance of visible light of from 450 to 600 nm of 70% or more, a transmittance of light in a wavelength region of from 695 to 720 nm of not more than 10%, and an amount of change of transmittance of not more than −0.8.
TL;DR: In this article, the authors demonstrate metamaterial metal-based bolometers, which take advantage of resonant absorption in that a spectral and/or polarization filter can be built into the bolometer.
Abstract: We demonstrate metamaterial metal-based bolometers, which take advantage of resonant absorption in that a spectral and/or polarization filter can be built into the bolometer. Our proof-of-principle gold-nanostructure-based devices operate around 1.5 μm wavelength and exhibit room-temperature time constants of about 134 μs. The ultimate detectivity is limited by Johnson noise, enabling room-temperature detection of 1 nW light levels within 1 Hz bandwidth. Graded bolometer arrays might allow for integrated spectrometers with several octaves bandwidth without the need for gratings or prisms and for integrated polarization analysis without external polarization optics.
TL;DR: In this paper, a photonic channelization scheme for a wideband radio-frequency (RF) signal based on an optical frequency comb (OFC), a comb filter, and an optical de-mux is proposed and demonstrated.
Abstract: A novel photonic channelization scheme for a wideband radio-frequency (RF) signal based on an optical frequency comb (OFC), a comb filter, and an optical de-mux is proposed and demonstrated. In the proposed channelizer, the input broadband RF signal is multicast by the OFC, spectrally sliced by a Fabry-Perot filter (FPF) and then channelized by a regular optical de-mux. Compared to previous proposals, the OFC can provide uniform and low-noise channelization and simplify the spectral alignment to the FPF. We demonstrate our scheme experimentally based on a 39-GHz-spaced OFC. As an application, instantaneous multiple-frequency measurement is demonstrated by directly detecting the channelized RF signal.
TL;DR: In this article, a volume multiplexed ultra-narrow band VBG filters with high reflection at multiple wavelengths are presented, which are formed by overlapping of several high efficiency volume Bragg gratings in a single glass plate.
Abstract: High efficiency volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass provide unmatched optical filtering capabilities with optical densities as high as 50 dB and linewidths as narrow as 1 cm -1 . In this work we review recent advances in VBG technologies that enabled key improvements of high efficiency grating properties and led to development of unique VBG based optical filters for Raman spectroscopy and other applications. Such narrow band notch and bandpass filters make ultra-low frequency Raman measurements possible with single stage spectrometers, therefore, largely improving optical throughput of high end Raman instruments while reducing complexity of the measurements. In this work we also present novel volume multiplexed ultra-narrow band VBG filters with high reflection at multiple wavelengths. Such multiband holographic optical elements are formed by overlapping of several high efficiency VBGs in a single glass plate. Raman spectra obtained with multiband VBG filters and single stage spectrometers, show unmatched capability of the filters to provide simultaneous access to Stokes and anti-Stokes Raman modes with frequencies as low as 5 cm -1 at different wavelengths.
TL;DR: In this article, two fabrication-friendly apodization techniques that are compatible with deep UV lithography and can be used in mass-production of photonic-integrated circuits are presented.
Abstract: An accurate control of the apodization profile is still an issue for integrated Bragg grating filters fabricated in silicon-on-insulator because of the high modal confinement of these waveguides. In this letter, we present two fabrication-friendly apodization techniques that are compatible with deep UV lithography and can be used in mass-production of photonic-integrated circuits. These techniques are reliable even for weak effective index modulation amplitude, thus opening the door to the fabrication of long and elaborate grating structures.
TL;DR: In this article, the authors used active resonant cavity injection locking for optical frequency combs and achieved an effective signal processing bandwidth in excess of 1 THz for optical waveform synthesis and detection.
Abstract: This paper presents recent results in the development of novel ultrafast technologies based on the generation and application of stabilized optical frequency combs By using novel active resonant cavity injection locking techniques, filtering, modulation and detection can be performed directly on individual components of the frequency comb enabling new approaches to optical waveform synthesis, waveform detection and matched filtering, with effective signal processing bandwidths in excess of 1 THz
09 Jul 2012
TL;DR: In this article, an LED-based 2D indoor localization system is proposed, which can locate a target to within centimeters for a normal room size, using computer simulations results that show that the target can be tracked to within a few centimeters.
Abstract: An LED based 2-D indoor localization system is proposed. For evaluation purpose we also present computer simulations results that show for a normal room size, we can locate a target to within centimeters.
TL;DR: A technique of hyperspectral imaging in stimulated Raman scattering (SRS) microscopy using a tunable optical filter, whose transmission wavelength can be varied quickly by a galvanometer mirror, is demonstrated.
Abstract: We demonstrate a technique of hyperspectral imaging in stimulated Raman scattering (SRS) microscopy using a tunable optical filter, whose transmission wavelength can be varied quickly by a galvanometer mirror Experimentally, broadband Yb fiber laser pulses are synchronized with picosecond Ti:sapphire pulses, and then spectrally filtered out by the filter After amplification by fiber amplifiers, we obtain narrowband pulses with a spectral width of 225 cm(-1) By using these pulses, we accomplish SRS imaging of polymer beads with spectral information
TL;DR: In this paper, a theoretical and experimental study of the ultranarrow bandwidth Faraday anomalous dispersion optical filter operating at the rubidium D1 line (795 nm) is presented.
Abstract: We present a theoretical and experimental study of the ultranarrow bandwidth Faraday anomalous dispersion optical filter operating at the rubidium D1 line (795 nm). This atomic line gives better performance than other lines for key figures of merit, e.g., simultaneously 71% transmission, 445 MHz bandwidth, and 1.2 GHz equivalent-noise bandwidth.
Patent•
05 Mar 2012
TL;DR: In this article, optical filters that provide regulation and/or enhancement of chromatic and luminous aspects of the color appearance of light to human vision have been proposed, generally to applications of such optical filters, to therapeutic applications, to industrial and safety applications of optical filters when incorporated, for example, in radiation-protective eyewear, to methods of designing and manufacturing optical filters.
Abstract: The invention generally relates to optical filters that provide regulation and/or enhancement of chromatic and luminous aspects of the color appearance of light to human vision, generally to applications of such optical filters, to therapeutic applications of such optical filters, to industrial and safety applications of such optical filters when incorporated, for example, in radiation-protective eyewear, to methods of designing such optical filters, to methods of manufacturing such optical filters, and to designs and methods of incorporating such optical filters into apparatus including, for example, eyewear and illuminants.
TL;DR: In this paper, the authors designed and simulated VO2/metal multilayers to obtain a large tunability of the thermal emissivity of IR filters in the typical mid wave IR window of many infrared cameras.
Abstract: In this paper, we design and simulate VO2/metal multilayers to obtain a large tunability of the thermal emissivity of infrared (IR) filters in the typical mid wave IR window of many infrared cameras. The multilayer structure is optimized to realise a low emissivity filter at high temperatures useful for military purposes. The values of tunability found for VO2/metal multilayers are larger than the value for a single thick layer of VO2.
TL;DR: An experiment in which the intracavity broadened spectrum of a Raman fiber laser is sliced by using a narrow-bandwidth optical filter, and rare extreme events are found to be generated in the far wings of the spectrum.
Abstract: We present an experiment in which the intracavity broadened spectrum of a Raman fiber laser is sliced by using a narrow-bandwidth optical filter. High-contrast fast fluctuations of the Stokes power are observed at the output of the optical filter. The statistics of the power fluctuations strongly change with the central wavelength of the filter, and rare extreme events are found to be generated in the far wings of the spectrum.
TL;DR: In this article, a tunable frequency-quadrupling dual-loop optoelectronic oscillator (OEO) based on a polarization modulator is proposed and demonstrated.
Abstract: A tunable frequency-quadrupling dual-loop optoelectronic oscillator (OEO) based on a polarization modulator is proposed and demonstrated. The introduce of frequency quadrupling in the proposed OEO not only increases the maximal achievable frequency by four times, extends the tuning range by four times, but also enables powerful optical signal processing functions. By incorporating an electrical-tunable yttrium-iron-garnet bandpass filter in the proposed OEO and employing a fiber Bragg grating as a wavelength-fixed optical notch filter, a high-quality microwave signal with a frequency tunable from 32 to 42.7 GHz is generated. The phase noise of the generated frequency-quadrupling signal is also studied.
TL;DR: In this article, a thermally tunable third-order microring resonator filter based on silicon nanowire waveguides was designed and fabricated, and the insertion loss at the center of the passband is less than 0.9 dB.
Abstract: We design and fabricate a thermally tunable third-order microring resonator filter based on silicon nanowire waveguides. Box-like response with low intraband ripple (~0.65 dB) and high out-of-band rejection over 40 dB is demonstrated. The insertion loss at the center of the passband is less than 0.9 dB. The filter response is successfully tuned by one free spectral range through thermo-optic effect with a tuning efficiency of 48.4 mW/nm. The dynamic tuning measurement shows the 10%-90% rise and 90%-10% fall time of the filter are 12.63 and 6.31 μs, respectively.
TL;DR: In this article, the authors proposed a method to locate precisely faults in WDM-PON by using a wavelength tunable chaotic laser, which consists of a multiple-longitudinalmode Fabry-Perot (FP) laser diode whose modes match the channels of WDM PON, and an optical feedback loop including a filter.
Abstract: We propose a method to locate precisely faults in wavelength-division-multiplexing (WDM) passive optical network (PON) by using a wavelength tunable chaotic laser The chaotic laser consists of a multiple-longitudinal-mode Fabry-Perot (FP) laser diode whose modes match the channels of WDM-PON, and an optical feedback loop including a filter The loop feeds a proportion of light of one mode that passes through the filter back into laser cavity to generate chaotic light By adjusting the filter frequency, we can tune the wavelength of the chaotic light, and diagnose the corresponding branch of WDM-PON We demonstrate a proof-of-concept experiment for detection of three ITU channels Fault location is realized by correlating the back-reflected light with its time-delayed duplicate The results show that spatial resolution of 2 cm and dynamic range of about 208dB can be achieved In addition, we have experimentally studied the effects of the strength level and wavelength mismatching of the feedback light on the chaotic output of the FP laser
TL;DR: In this paper, the phase and amplitude relationship between RF driving signals of two cascaded phase modulators and the impact of EDFA gain were analyzed for a multi-terabit optical OFDM superchannel transmission.
Abstract: The generation of coherent and frequency-locked optical multi-carriers by using cascaded phase modulators and recirculating frequency shifter (RFS) based on an erbium doped fiber amplifier (EDFA) loop has been investigated theoretically and experimentally for a multi-terabit optical orthogonal frequency division multiplexing (OFDM) superchannel transmission. The phase and amplitude relationship between RF driving signals of two cascaded phase modulators and the impact of EDFA gain are analyzed. Experimental results are in good agreement with the theoretical analysis. The 112 coherent and frequency-locked subcarriers obtained after tilt filtering exhibit a tone-to-noise ratio of larger than 26 dB, a power fluctuation of less than 5 dB, and a frequency spacing of 25 GHz giving a 22.6 nm-wide optical OFDM signal spectrum. By using this method, we have successfully generated a 10-Tbit/s (112 × 100 Gbit/s) single optical OFDM polarization-division-multiplexing QPSK (PDM-QPSK) superchannel with an optical signal to noise ratio per OFDM subchannel greater than 20 dB at 0.1 nm bandwidth, and it has been transmitted over a 640-km SMF-28 and EDFA-only link with BER less than 2 × 10-3.
TL;DR: SuperSpec as discussed by the authors is an ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy, which consists of a horn-coupled microstrip feedline, a bank of narrow-band superconducting resonator filters that provide spectral selectivity, and kinetic inductance detectors (KIDs) that detect the power admitted by each filter resonator.
Abstract: SuperSpec is an ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed readout will enable construction of powerful multibeam spectrometers for high-redshift observations. The spectrometer consists of a horn-coupled microstrip feedline, a bank of narrow-band superconducting resonator filters that provide spectral selectivity, and kinetic inductance detectors (KIDs) that detect the power admitted by each filter resonator. The design is realized using thin-film lithographic structures on a silicon wafer. The mm-wave microstrip feedline and spectral filters of the first prototype are designed to operate in the band from 195-310 GHz and are fabricated from niobium with at T_c 9.2 K. The KIDs are designed to operate at hundreds of MHz and are fabricated from titanium nitride with a T_c of ~ 2 K. Radiation incident on the horn travels along the mm-wave microstrip, passes through the frequency-selective filter, and is finally absorbed by the corresponding KID where it causes a measurable shift in the resonant frequency. In this proceedings, we present the design of the KIDs employed in SuperSpec and the results of initial laboratory testing of a prototype device. We will also brie describe the ongoing development of a demonstration instrument that will consist of two 500-channel, R=700 spectrometers, one operating in the 1-mm atmospheric window and the other covering the 650 and 850 micron bands.
TL;DR: In this article, a waveguide-based quadruple optical ring resonator (QORR) with four asymmetric rings is introduced to obtain very wide free spectral range (FSR).
TL;DR: In this paper, an acousto-optic tunable filter (AOTF) operating in the long-wave infrared (LWIR) region has been developed based on the wide-angle regime of light diffraction in the YZ plane of the birefringent crystal operating from 8.4 to 13.6 µm.
Abstract: The acoustic, optic and acousto-optic properties of tellurium crystals have been examined in order to develop an acousto-optic tunable filter (AOTF) operating in the long-wave infrared (LWIR) region. The AOTF design is based on the wide-angle regime of light diffraction in the YZ plane of the birefringent crystal operating from 8.4 to 13.6 µm. Device characteristics were obtained from both theoretical and experimental investigations. Experiments were carried out using both a 10.6 µm pulsed CO2 laser as well as a tunable CO2 laser operating in a continuous wave mode from 9.2 to 10.7 µm. The AOTF was tuned over the acoustic frequency range of 81.5–94.7 MHz. The filtering performance in the tellurium device was provided by a pure shear elastic wave propagating at a 95.8° angle with respect to the positive direction of the optic axis, while an ordinary polarized optical beam was incident at the Bragg angle of 6.0° relative to the acoustic wavefront. At 10.6 µm, the measured spectral bandwidth of the filter was 127 nm and the optical transmission coefficient was around 8.8% with 2.0 W drive power. This paper presents detailed results from both the theoretical as well as experimental device characterization including the spectral images obtained with a 256 × 256 mercury cadmium telluride camera cooled to 77 K.
TL;DR: All-fiber polarization interference filters, known as Lyot and Lyot-Őhman filters, based on alternative concatenation of UV-inscribed fiber gratings with structure tilted at 45° and polarization maintaining (PM) fiber cavities are reported.
Abstract: We report all-fiber polarization interference filters, known as Lyot and Lyot-Ohman filters, based on alternative concatenation of UV-inscribed fiber gratings with structure tilted at 45° and polarization maintaining (PM) fiber cavities. Such filters generate comb-like transmission of linear polarization output. The free spectral range (FSR) of a single-stage (Lyot) filter is PM fiber cavity length dependent, as a 20 cm long cavity showed a 26.6 nm FSR while the 40 cm one exhibited a 14.8 nm FSR. Furthermore, we have theoretically and experimentally demonstrated all-fiber 2-stage and 3-stage Lyot-Ohman filters, giving more freedom in tailoring the transmission characteristics.