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.

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.

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.

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.

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.

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.

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.

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.

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%.

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.

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.

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

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

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.

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.

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.

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.

Abstract: A continuously tunable microwave fractional Hilbert transformer (FHT) implemented based on a nonuniformly spaced photonic microwave delay-line filter is proposed and demonstrated. An FHT has a frequency response with a unity magnitude response and a phase response having a phase shift between 0 and π at the center frequency. A seven-tap photonic microwave delay-line filter with nonuniformly spaced taps is designed to provide such a frequency response. The advantage of using nonuniform spacing is that an equivalent negative coefficient can be achieved by introducing an additional time delay leading to a π phase shift, corresponding to a negative coefficient. An FHT operating at a center frequency around 8.165 GHz with a tunable order between 0.24 and 1 is implemented. A classical HT operating at a center frequency of 7.573 GHz with a bandwidth greater than 4.5 GHz is also implemented. The use of the classical HT to perform temporal Hilbert transform of a Gaussian-like electrical pulse is demonstrated.

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.

Abstract: In this paper, we present a wide range displacement sensor system using the fiber Bragg grating (FBG), spring, and a twin-core fiber. The quantitative analysis of the theory of the cascaded FBG-spring system for displacement measurement is introduced together with the basic working principle of a twin-core fiber filter. The feasibility of the method is demonstrated in experiments which shows the output optical intensity linear relation with the displacement. The characteristics of the wide range, high resolution, low cost, and compact scheme would make this method more applicable.

Abstract: An integrated mode filter in the form of a shallow surface relief was used to reduce the spectral width of a high-speed 850 nm vertical-cavity surface-emitting laser (VCSEL). The mode filter reduced the RMS spectral width from 0.9 to 0.3 nm for a VCSEL with an oxide aperture as large as 5 mu m. Because of reduced effects of chromatic and modal fibre dispersion, the mode filter significantly increases the maximum error-free (bit error rate < 10(-12)) transmission distance, enabling transmission at 25 Gbit/s over 500 m of multimode OM3+ fibre.

Abstract: Nyquist pulse shaping can be used to increase the spectral efficiency (SE) by narrowing the signal spectrum without introducing intersymbol interference in a wavelength-division-multiplexed (WDM) system In this paper, we investigate the complexity and performance of pulse shaping at the transmitter side using digital finite-impulse-response (FIR) or frequency-domain-equalization (FDE) filters to increase the SE in a polarization-division-multiplexed quadrature-phase-shift-keyed WDM system Simulation results show that FIR filters with 17 taps allow for a reduction in channel spacing to 11 times the symbol rate within a 1 dB penalty The root-raised-cosine spectrum shape has better performances than the raised-cosine spectrum shape with that channel spacing An FDE filter with a fast Fourier transform size of 64 and an overlap length of 8 points performs slightly better than a 17-tap FIR filter

Abstract: We present results for a broad bandwidth continuously tunable optical delay line based on the balanced side-coupled integrated space sequence of resonators scheme. A tunable delay of up to 345 ps is obtained without distortion of the optical signal. Fast thermal switching speed under 10 μs is achieved without any measurable long-term transient by utilizing a novel balanced thermal tuning scheme.

Abstract: A tunable optoelectronic oscillator implemented employing a high-Q-factor spectrum-sliced photonic microwave transversal filter without using any electronic microwave filters is proposed and experimentally demonstrated for the first time to our knowledge The high-Q-factor photonic microwave transversal filter is implemented using a sliced broadband optical source and a dispersive element, to perform frequency-tunable microwave frequency selection The central frequency of the microwave filter is a function of the wavelength spacing of the sliced optical source and the chromatic dispersion of the dispersive element Therefore, the oscillation frequency can be tuned by changing either the channel spacing of the sliced broadband optical source or the chromatic dispersion of the dispersive element A proof-of-concept experiment is performed An optoelectronic oscillator with a tunable frequency range of 97 GHz is achieved The generated microwave signal exhibited a good phase noise performance with a phase noise of -120 dBc/Hz at an offset of 10 kHz

Abstract: An optically tunable frequency-multiplying optoelectronic oscillator (OEO) incorporating a tunable microwave photonic bandpass filter is proposed and experimentally demonstrated. The microwave photonic filter is implemented employing a phase-shifted fiber Bragg grating, a polarization modulator, and a phase modulator. The frequency tuning is realized by changing the wavelength of the light wave to the OEO loop. The frequency-doubling and frequency-quadrupling operations with large frequency tunability are experimentally demonstrated. The phase noise performance of the generated microwave signals is also investigated.

Abstract: We demonstrate a Cs FADOF (Faraday anomalous dispersion optical filter) with a single transmission peak resonant with the 6S1/2, F = 4 → 7P3/2, F′ = 3, 4, 5 transition at 455 nm. The filter achieves a single peak transmission of 86%. With the technique of saturated absorption spectra, we obtain the bandwidth of the single peak, which is 1.5 GHz. While most of other FADOFs operate at frequencies far from absorption, the filter we have realized can provide light exactly resonant with atomic transitions with a high transmission. We also find that, at a particular temperature, we can achieve a single transmission peak rather than many peaks far from absorption by changing the strength of magnetic field. This technique can also be applied to other alkali atoms.

Abstract: Plasmonic metamaterials based on metal-dielectric nanostructures exhibit unique optical properties such as high near-field enhancement, negative refractive indexing, and optical cloaking. In this paper, we present a plasmonic multiband metamaterial based on UT shaped nanoparticles. In order to understand the multispectral response, we analyze the near-field distributions at the corresponding resonance frequencies. In addition, we both numerically and experimentally, show the dependence of the spectral response on the geometrical parameters of the structure. By embedding the system in a dielectric cladding medium, we show strong sensitivities of the resonant behavior to the refractive index and thickness of the dielectric load. Due to its tunable multiband spectral characteristics, the proposed metamaterial antenna can be used for wide range of applications, such as wavelength-tunable active filters, optical modulators, ultrafast switching devices, and biosensing.

Abstract: Coherent and compact supercontinuum light sources for the mid IR spectral regime are disclosed and exemplary applications thereof. The supercontinuum generation is based on the use of highly nonlinear fibers or waveguides. In at least one embodiment the coherence of the supercontinuum sources is increased using low noise mode locked short pulse sources. Compact supercontinuum light sources can be constructed with the use of passively mode locked fiber or diode lasers. Wavelength tunable sources can be constructed using appropriate optical filters or frequency conversion sections. Highly coherent supercontinuum sources further facilitate coherent detection schemes and can improve the signal/noise ratio in lock in detection schemes.

Abstract: The present invention addresses the problem of providing an optical filter having exceptional transmittance characteristics in which the drawbacks of conventional near-infrared-cutting filters and other optical filters are overcome, and light scattering is minimal even during light absorption. This optical filter is characterized by containing a squarylium compound and a compound for absorbing or quenching fluorescence. This optical filter preferably contains a near-infrared absorbing dye that contains a squarylium compound (A), and at least one compound (B) selected from the group consisting of a phthalocyanine compound (B-1), and a cyanine compound (B-2).