Showing papers on "Optical filter published in 2014"
TL;DR: The remarkable advantage of CASSI is that the entire data cube is sensed with just a few FPA measurements and, in some cases, with as little as a single FPA shot.
Abstract: Imaging spectroscopy involves the sensing of a large amount of spatial information across a multitude of wavelengths. Conventional approaches to hyperspectral sensing scan adjacent zones of the underlying spectral scene and merge the results to construct a spectral data cube. Push broom spectral imaging sensors, for instance, capture a spectral cube with one focal plane array (FPA) measurement per spatial line of the scene [1], [2]. Spectrometers based on optical bandpass filters sequentially scan the scene by tuning the bandpass filters in steps. The disadvantage of these techniques is that they require scanning a number of zones linearly in proportion to the desired spatial and spectral resolution. This article surveys compressive coded aperture spectral imagers, also known as coded aperture snapshot spectral imagers (CASSI) [1], [3], [4], which naturally embody the principles of compressive sensing (CS) [5], [6]. The remarkable advantage of CASSI is that the entire data cube is sensed with just a few FPA measurements and, in some cases, with as little as a single FPA shot.
487 citations
TL;DR: In this paper, the authors focus on the presentation and discussion of bandpass filters, such as selectivity, cost, miniaturization, sensitivity to environmental effects (temperature and humidity), and power handling, combined with predefined in-band and out-of-band performance metrics, are critical specifications of the design with respect to the RF and microwave front ends.
Abstract: The electromagnetic (EM) spectrum is becoming more crowded, and it is densely populated with various wireless signals and parasitic interferers in connection with communication and sensing services. Increasingly sophisticated radio-frequency (RF), microwave, and millimeter-wave filters are required to enable the selection and/or rejection of specific frequency channels. This will occur in future generations of the wireless system, such as the current hotly debated fifth-generation communication systems, where the spectral channelization of a heterostructured wide-band signals will be critical in support of a host of coexisting bandwidths or speeds and applications. Bandpass filters have been the most useful and popular types for such applications and are the most difficult to design and develop in practice. Other types of filters such as notch (stopband) and lowpass filters have also been widely used in many systems, and their design is generally perceived less critical with respect to band-pass filters. This article will focus on the presentation and discussion of bandpass filters. Design factors or parameters of filters, such as selectivity, cost, miniaturization, sensitivity to environmental effects (temperature and humidity, for example), and power handling, combined with predefined in-band and out-of-band performance metrics, are critical specifications of the design with respect to the development of RF and microwave front ends. This is indispensable for the efficient utilization of frequency spectrum resources and the cost-effective enhancement of wireless system performances.
176 citations
IMEC1
TL;DR: In this paper, a novel snapshot multispectral imager concept based on optical filters monolithically integrated on top of a standard CMOS image sensor is introduced, which overcomes the problems mentioned for scanning applications by snapshot acquisition, where an entire multi-spectral data cube is sensed at one discrete point in time.
Abstract: The adoption of spectral imaging by industry has so far been limited due to the lack of high speed, low cost and compact
spectral cameras. Moreover most state-of-the-art spectral cameras utilize some form of spatial or spectral scanning
during acquisition, making them ill-suited for analyzing dynamic scenes containing movement. This paper introduces a
novel snapshot multispectral imager concept based on optical filters monolithically integrated on top of a standard
CMOS image sensor. It overcomes the problems mentioned for scanning applications by snapshot acquisition, where an
entire multispectral data cube is sensed at one discrete point in time. This is enabled by depositing interference filters per
pixel directly on a CMOS image sensor, extending the traditional Bayer color imaging concept to multi- or hyperspectral
imaging without a need for dedicated fore-optics. The monolithic deposition leads to a high degree of design flexibility.
This enables systems ranging from application-specific, high spatial resolution cameras with 1 to 4 spectral filters, to
hyperspectral snapshot cameras at medium spatial resolutions and filters laid out in cells of 4x4 to 6x6 or more. Through
the use of monolithically integrated optical filters it further retains the qualities of compactness, low cost and high
acquisition speed, differentiating it from other snapshot spectral cameras.
141 citations
TL;DR: In this article, the authors demonstrate non-invasive light observation in silicon photonics devices by exploiting photon interaction with intra-gap energy states localized at the waveguide surface, where electric contacts are located at a suitable distance from the core, thus introducing no measurable extra-photon absorption.
Abstract: Photonic technologies lack non-invasive monitoring tools to inspect the light inside optical waveguides. This is one of the main barriers to large scale integration, even though photonic platforms are potentially ready to host thousands of elements on a single chip. Here, we demonstrate non-invasive light observation in silicon photonics devices by exploiting photon interaction with intra-gap energy states localized at the waveguide surface. Light intensity is monitored by measuring the electric conductance of the silicon core through a capacitive access to the waveguide. The electric contacts are located at suitable distance from the waveguide core, thus introducing no measurable extra-photon absorption and a phase perturbation as low as 0.2 mrad, comparable to thermal fluctuations below 3 mK. Light monitoring with a sensitivity of -30 dBm and a dynamic range of 40 dB is demonstrated in waveguides and high-Q resonators, and for the tuning of coupled-resonator optical filters. This approach realizes a ContactLess Integrated Photonic Probe (CLIPP), that is simple, inherently CMOS compatible, non-invasive and scalable to hundreds of probing points per chip. The CLIPP concept provides a viable route to real-time conditioning and feedback control of densely-integrated photonic systems.
137 citations
TL;DR: In this paper, the authors reported a significant enhancement in the selectivity of SBS-based microwave-photonic (MWP) filters with a single passband of 250 MHz-1 GHz bandwidth.
Abstract: Stimulated Brillouin scattering (SBS) in optical fibers has long been used in frequency-selective optical signal processing, including in the realization of microwave-photonic (MWP) filters. In this work, we report a significant enhancement in the selectivity of SBS-based MWP filters. Filters having a single passband of 250 MHz–1 GHz bandwidth are demonstrated, with selectivity of up to 44 dB. The selectivity of the filters is better than that of the corresponding previous arrangements by about 15 dB. The shape factor of the filters, defined as the ratio between their −20 dB bandwidth and their −3 dB bandwidth, is between 1.35 and 1.5. The central transmission frequency, bandwidth, and spectral shape of the passband are all independently adjusted. Performance enhancement is based on two advances, compared with previous demonstrations of tunable SBS-based MWP filters: (a) the polarization attributes of SBS in standard, weakly birefringent fibers are used to discriminate between in-band and out-of-band components and (b) a sharp and uniform power spectral density of the SBS pump waves is synthesized through external modulation of an optical carrier by broadband, frequency-swept waveforms. The signal-to-noise ratio of filtered radio-frequency waveforms and the linear dynamic range of the filters are estimated analytically and quantified experimentally. Lastly, a figure of merit for the performance of the filters is proposed and discussed. The filters are applicable to radio-over-fiber transmission systems.
100 citations
TL;DR: Results demonstrate the realization of a multiple-frequency measurement capability over a frequency range of 0.1-20 GHz that can be extended to 90 GHz, and with a measurement resolution of 250 MHz.
Abstract: A new microwave photonic instantaneous frequency measurement system that can simultaneously measure multiple-frequency signals while achieving very high resolution and wide frequency measurement range is presented. It is based on the frequency-to-time mapping technique implemented using a frequency shifting recirculating delay line loop and a narrowband optical filter realized by the in-fiber stimulated Brillouin scattering effect. Experimental results demonstrate the realization of a multiple-frequency measurement capability over a frequency range of 0.1–20 GHz that can be extended to 90 GHz, and with a measurement resolution of 250 MHz.
96 citations
TL;DR: Numerical simulations demonstrate through numerical simulations the feasibility of implementing SWG Bragg gratings in silicon-on-insulator (SOI) and SWG ring resonators in SOI and verify their operation using numerical simulations and experiments.
Abstract: We propose and simulate the characteristics of optical filters based on subwavelength gratings. In particular, we demonstrate through numerical simulations the feasibility of implementing SWG Bragg gratings in silicon-on-insulator (SOI). We also propose SWG ring resonators in SOI and verify their operation using numerical simulations and experiments. The fabricated devices exhibit an extinction ratio as large as 30 dB and a Q-factor as high as ~20,000. These fundamental SWG filters can serve as building blocks for more complex devices.
87 citations
TL;DR: It is shown that in the DMT VLC system, the blue optical filter may be unnecessary, and even degrade the transmission performance (by reducing the optical signal-to-noise ratio (SNR)).
Abstract: Optical blue filter is usually regarded as a critical optical component for high speed phosphor-based white light emitting diode (LED) visible-light-communication (VLC). However, the optical blue filter plays different roles in VLC when using modulations of on-off keying (OOK) or discrete multi-tone (DMT). We show that in the DMT VLC system, the blue optical filter may be unnecessary, and even degrade the transmission performance (by reducing the optical signal-to-noise ratio (SNR)). Analyses and verifications by experiments are performed. To the best of our knowledge, this is the first time the function of blue filters in VLC is explicitly analyzed.
80 citations
TL;DR: In this paper, the authors presented transmission visible wavelength filters based on strong interference behaviors in an ultrathin semiconductor material between two metal layers, which can have potential for diverse applications ranging from color display devices to image sensors.
Abstract: We present transmission visible wavelength filters based on strong interference behaviors in an ultrathin semiconductor material between two metal layers. The proposed devices were fabricated on 2 cm × 2 cm glass substrate, and the transmission characteristics show good agreement with the design. Due to a significantly reduced light propagation phase change associated with the ultrathin semiconductor layer and the compensation in phase shift of light reflecting from the metal surface, the filters show an angle insensitive performance up to ±70°, thus, addressing one of the key challenges facing the previously reported photonic and plasmonic color filters. This principle, described in this paper, can have potential for diverse applications ranging from color display devices to the image sensors.
79 citations
TL;DR: A 448 Gbit/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation (DP 16-QAM) signal is demonstrated using look-up table (LUT) correction and optical pulse shaping to enhance the spectral efficiency and reduce the requirements on the receiver bandwidth and analog-to-digital converter sampling rate.
Abstract: A 448 Gbit/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation (DP 16-QAM) signal and a 1.206 Tbit/s three-carrier DP 16-QAM signal are demonstrated using look-up table (LUT) correction and optical pulse shaping. The LUT correction is used to mitigate the effects of transmitter-based pattern-dependent distortion due to the high symbol rates. A programmable optical filter is employed to narrow the modulated signal spectrum and thereby enhance the spectral efficiency and reduce the requirements on the receiver bandwidth and analog-to-digital converter sampling rate. By combining these techniques, the back-to-back required optical signal-to-noise ratios are 26.6 dB and 27.2 dB for BER = 10(-3), and transmission over 1200 and 1500 km of standard single-mode fiber with EDFA amplification was achieved for the 448 Gbit/s signal (12% forward error correction (FEC) overhead) and 1.206 Tbit/s signal (20% FEC overhead), respectively.
78 citations
TL;DR: A rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution is proposed.
Abstract: We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution. The rectangular shape of the filter is precisely achieved utilizing digital feedback control of the comb-like pump spectral lines. The passband ripple is suppressed to ~1 dB by mitigating the nonlinearity influences of the comb-like pump lines generated in electrical and optical components and fibers. Moreover a fiber with a single Brillouin peak is employed to further reduce the in-band ripple and the out-of-band SBS gain at the same time. Finally, we analyze the noise performance of the filter at different bandwidth cases and demonstrate the system performance of the proposed filter with 2.1-GHz bandwidth and 19-dB gain by amplifying a 2-GHz orthogonal frequency-division-multiplexing (OFDM) signal with quadrature-phase-shift-keying (QPSK) and 16-quadrature-amplitude-modulation (16-QAM) on each subscriber.
TL;DR: In this paper, a method for obtaining good images of a sprayed speckle pattern on specimen surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) using plasma spray for specckle preparation in which a bandpass filter, neutral density filters, and a linear polarizing filter are used to reduce intensity and noise in images.
Abstract: A method is presented for obtaining good images of a sprayed speckle pattern on specimen surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) using plasma spray for speckle preparation in which a bandpass filter, neutral density filters, and a linear polarizing filter are used to reduce intensity and noise in images. This is accomplished by speckle preparation through the use of plasma spray and suppression of black-body radiation through the use of filters. By using plasma spray for speckle preparation and the filters for image acquisition, the method was demonstrated to be capable of providing accurate DIC measurements up to 2600°C. The full-field stretching deformation of the specimen was determined using the DIC technique. Experimental results indicate that the proposed high-temperature DIC method is easy to implement and can be applied to practical, full-field, high-temperature deformation measurements with high accuracy.
TL;DR: In this article, a multichannel filter is realized in plasmonic circuits directly, which consists of four plasmanic nanocavities coupled via a plasmoric waveguide etched in a gold film.
Abstract: Nanoscale multichannel filter is realized in plasmonic circuits directly, which consists of four plasmonic nanocavities coupled via a plasmonic waveguide etched in a gold film. The feature device size is only 1.35 μm, which is reduced by five orders of magnitude compared with previous reports. The optical channels are formed by transparency windows of plasmon-induced transparencies. A shift of 45 nm in the central wavelengths of optical channels is obtained when the plasmonic coupled-nanocavities are covered with a 100-nm-thick poly(methyl methacrylate) layer. This work opens up the possibility for the realization of solid quantum chips based on plasmonic circuits.
TL;DR: In this article, the authors deal with four kinds of wavelength-division-multiplexing filters: ring resonators, lattice-form filters, arrayed-waveguide gratings and planar Echelle gratings.
Abstract: Silicon photonics wavelength-division-multiplexing filters are important building blocks in >100 G transceivers and near future on-chip communications between many cores. This paper deals with four kinds of wavelength-division-multiplexing filters: they are, ring resonators, lattice-form filters, arrayed-waveguide gratings and planar Echelle gratings. Progress and technical challenges for these filter devices will be described.
TL;DR: An excitation-scanning hyperspectral imaging microscope is developed that overcomes limitations by providing high transmission with short acquisition times and demonstrates excitation scanning has utility in a wide range of time-dependent and photosensitive applications.
Abstract: Hyperspectral imaging is a versatile tool that has recently been applied to a variety of biomedical applications, notably live-cell and whole-tissue signaling. Traditional hyperspectral imaging approaches filter the fluorescence emission over a broad wavelength range while exciting at a single band. However, these emis- sion-scanning approaches have shown reduced sensitivity due to light attenuation from spectral filtering. Consequently, emission scanning has limited applicability for time-sensitive studies and photosensitive applications. In this work, we have developed an excitation-scanning hyperspectral imaging microscope that overcomes these limitations by providing high transmission with short acquisition times. This is achieved by filtering the fluorescence excitation rather than the emission. We tested the efficacy of the excitation-scanning microscope in a side-by-side comparison with emission scanning for detection of green fluorescent protein (GFP)-expressing endothelial cells in highly autofluorescent lung tissue. Excitation scanning provided higher signal-to-noise characteristics, as well as shorter acquisition times (300 ms∕wavelength band with excitation scanning versus 3 s∕wavelength band with emission scanning). Excitation scanning also provided higher delin- eation of nuclear and cell borders, and increased identification of GFP regions in highly autofluorescent tissue. These results demonstrate excitation scanning has utility in a wide range of time-dependent and photosensitive
TL;DR: In this article, the design and packaging of simple, small, and low cost sensor heads, used for continuous liquid level measurement using uniformly thinned (etched) optical fiber Bragg grating (FBG) are proposed.
Abstract: The design and packaging of simple, small, and low cost sensor heads, used for continuous liquid level measurement using uniformly thinned (etched) optical fiber Bragg grating (FBG) are proposed. The sensor system consists of only an FBG and a simple detection system. The sensitivity of sensor is found to be 23 pm/cm of water column pressure. A linear optical fiber edge filter is designed and developed for the conversion of Bragg wavelength shift to its equivalent intensity. The result shows that relative power measured by a photo detector is linearly proportional to the liquid level. The obtained sensitivity of the sensor is nearly −15 mV/cm .
TL;DR: The BDG-based optical spectrometry features ultrahigh resolution, large wavelength coverage, and a simple direction-detection scheme and can be readily extended to C+L bands with a commercial tunable laser.
Abstract: We propose and demonstrate an ultrahigh-resolution optical spectrometry based on Brillouin dynamic gratings (BDGs). Taking advantage of creating a long grating in an optical fiber, an ultra-narrow bandwidth optical filter is realized by operating a BDG in a long single-mode fiber (SMF), and the optical spectrometry is performed by sweeping the center wavelength of the BDG-based filter through a swept-tuned laser. The BDG-based optical spectrometry features ultrahigh resolution, large wavelength coverage, and a simple direction-detection scheme. In the experiment, a 4 fm (0.5 MHz) spectral resolution is achieved by operating a BDG in a 400 m SMF, and the wavelength coverage can be readily extended to C+L bands with a commercial tunable laser.
TL;DR: In this paper, a photonic approach to generate triangular-shaped microwave pulses using stimulated Brillouin scattering (SBS)-based optical carrier processing is proposed and experimentally demonstrated, where only odd-order optical sidebands are obtained by externally modulating the CW light wave using a Mach-Zehnder modulator biased at the minimum-transmission-point (MITP).
Abstract: A photonic approach to generate triangular-shaped microwave pulses using stimulated Brillouin scattering (SBS)-based optical carrier processing is proposed and experimentally demonstrated. In the proposed approach, only odd-order optical sidebands are obtained by externally modulating the CW light wave using a Mach–Zehnder modulator (MZM) biased at the minimum-transmission-point (MITP). Then the suppressed optical carrier is recovered by the amplification effect from the SBS gain. After that, all negative-order optical sidebands are removed by using an optical filter. Through opto-electronic conversion in a photodetector (PD), the amplitude of the 1st-order electrical harmonic can be tuned just to be nine times of that of the 3rd-order one when the modulation index is specified as 1.51. Therefore the target pulse is generated and its repetition rate can be flexibly tuned by adjusting the frequency of the radio frequency (RF) signal applied to the MZM. According to the principle above, triangular-shaped microwave pulses with repetition rates of 5, 8, and 10 GHz are generated in our experiments, respectively, showing desired waveforms and excellent tunability.
TL;DR: An indoor positioning system based on visible light communication technology with three-dimensional positioning capability with basic framed slotted ALOHA applied as the channel access method and particle filters used in order to realize target tracking are introduced.
Abstract: This paper introduces an indoor positioning system based on visible light communication technology with three-dimensional positioning capability. Light-emitting diodes are employed as transmitters, with photodiodes as receivers to obtain the received signal strength (RSS) information. Based on the trilateration technique, the proposed algorithm is able to calculate horizontal coordinates of the receiver with RSS information, after which the height of the receiver is estimated. The system does not require other measurements such as time-of-arrival or angle-of-arrival, thus system design and costs are simplified and minimized. Basic framed slotted ALOHA is applied as the channel access method to enable asynchronous transmissions. In addition, Kalman and particle filters are used in order to realize target tracking. Results show that both filters help to increase the positioning accuracy and the particle filter exhibits a better performance than the Kalman filter, with a higher computational complexity.
TL;DR: Although much thinner than conventional optical interference coatings, nanometer-thick films made of optically absorbing materials can display strong interference effects as discussed by the authors, which shows promise for coloring and labeling, optical filters, tunable absorbers and emitters, and energy harvesting.
Abstract: Although much thinner than conventional optical interference coatings, nanometer-thick films made of optically absorbing materials can display strong interference effects. This new class of coatings shows promise for coloring and labeling, optical filters, tunable absorbers and emitters, and energy harvesting.
TL;DR: In this article, the authors present a comprehensive design, fabrication, and characterization analysis of compact silicon-on-insulator bandpass filters with widely tunable bandwidth, based on an unbalanced Mach-Zehnder interferometer loaded with a pair of ring resonators.
Abstract: We present a comprehensive design, fabrication, and characterization analysis of compact silicon-on-insulator bandpass filters with widely tunable bandwidth. The filter architecture is based on an unbalanced Mach-Zehnder interferometer loaded with a pair of ring resonators. A wide bandwidth tunability (from 10% to 90% FSR) can be achieved by controlling the resonant frequency of the rings while preserving a good filter off-band rejection. Design rules are provided that take into account fabrication tolerances as well as losses. Furthermore, the use of tunable couplers allows a more flexible shaping of the spectral response of the filter. The sensitivity with respect to nonlinear effects is carefully investigated. Operation over a wavelength spectrum of 20 nm is demonstrated, making the device suitable for channel subset selection in WDM systems, reconfigurable filters for gridless networking and adaptive filtering of signals.
TL;DR: In this paper, the wavefronts of the reflected and transmitted light distributions are precisely manipulated by spatial parametric variation of a subwavelength thin-film Si grating, which inherently possesses polarization filtering properties.
Abstract: We propose a semiconductor metasurface that simultaneously performs two independent functions: focusing and polarization filtering. The wavefronts of the reflected and transmitted light distributions are precisely manipulated by spatial parametric variation of a subwavelength thin-film Si grating, which inherently possesses polarization filtering properties. We design a 12-μm-wide metasurface containing only nineteen Si grating ridges. Under a 10-μm-wide unpolarized Gaussian beam incidence at wavelength of 1.55 μm, the resulting device shows promising theoretical performance with high power efficiency exceeding 80% and polarization extinction ratio of ∼10 dB with focal spot diameters near 1–2 μm.
24 Nov 2014
TL;DR: In this article, an arrayed waveguide grating and free-space manipulation is used to achieve arbitrary filtering at record metrics of 0.8GHz resolution over 200GHz span.
Abstract: Spectral processor based on arrayed waveguide grating and free-space manipulation is capable of arbitrary filtering at record metrics of 0.8GHz resolution over 200GHz span. Narrowband coherent drop-demultiplexing and controlled optical shaping is demonstrated in unison with digital sub-banding.
TL;DR: In this paper, a dual-OPLL system, synchronised to an optical frequency comb generator without any prior filtering of the comb lines, allows generation of high spectral purity signals at any desired frequency from several GHz up to THz range.
Abstract: We present a review of the critical design aspects of monolithically integrated optical phase lock loops (OPLLs). OPLL design procedures and OPLL parameters are discussed. A technique to evaluate the gain of the closed loop operating system is introduced and experimentally validated for the first time. A dual-OPLL system, when synchronised to an optical frequency comb generator without any prior filtering of the comb lines, allows generation of high spectral purity signals at any desired frequency from several GHz up to THz range. Heterodyne phase locking was achieved at a continuously tuneable offset frequency between 2 and 6 GHz. Thanks to the photonic integration, small dimensions, and custom-made electronics, the propagation delay in the loop was less than 1.8 ns, allowing good phase noise performance with OPLLs based on lasers with linewidths less than a few MHz. The system demonstrates the potential for photonic integration to be applied in various microwave photonics applications where narrow-bandwidth tuneable optical filters with amplification functionality are required.
20 Nov 2014
TL;DR: In this article, a chirped dichroic mirror and a double-chirped mirror pair are used to avoid unwanted nonlinearity during beam propagation, with custom-tailored dispersion and reflectivity over more than two octaves of bandwidth ranging from 0.49 to 2.3μm.
Abstract: Two-octave-spanning precision dispersive mirror systems are demonstrated, providing a new enabling technology for pulse-energy and bandwidth scaling of sub-cycle optical waveform synthesizers. We propose and characterize new dispersion management schemes with advanced dielectric coating designs. Based on an analytic dual adiabatic matching structure, we implement a chirped dichroic mirror, to efficiently optimize the beam combining from different spectra, and a double-chirped mirror pair, to avoid unwanted nonlinearity during beam propagation, with custom-tailored dispersion and reflectivity over more than two octaves of bandwidth ranging from 0.49 to 2.3 μm, supporting 1.9-fs-short sub-optical-cycle pulses. The multilayer coating structures can also be applied to the design of chirped-fiber Bragg gratings and general optical filters. The proposed designs and schemes will benefit ultrabroadband applications requiring precise dispersion management, especially enabling the generation of intense sub-optical-cycle light transients.
TL;DR: SuperSpec as mentioned in this paper is an ultra-compact spectrometer-on-a-chip for mm and submm wavelength astronomy with planar, lithographed, superconducting transmission line resonator filters.
Abstract: SuperSpec is an ultra-compact spectrometer-on-a-chip for mm and submm wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed detector readout will enable construction of powerful multi-object spectrometers for observations of galaxies at high redshift. SuperSpec is a filter bank with planar, lithographed, superconducting transmission line resonator filters and lumped-element kinetic inductance detectors made from Titanium Nitride. We have built an 81 detector prototype that operates in the 195–310 GHz band. The prototype has a wide-band metal feed horn with a transition to microstrip that feeds the filter bank. The prototype has demonstrated optical filter bank channels with a range of resolving powers from 300 to 700, measured fractional frequency noise of 10^(−17)Hz^(−1) at 1 Hz.
TL;DR: This work investigates three different device architectures consisting of single, double, and triple layers based on all-transparent dielectric and semiconductor thin films with high-performance bandpass filter profiles with broad, flat low-transmission sidebands accommodating sharp transmission peaks.
Abstract: We study theoretically modal properties and parametric dependence of guided-mode resonance bandpass filters operating in the mid- and near-infrared spectral domains. We investigate three different device architectures consisting of single, double, and triple layers based on all-transparent dielectric and semiconductor thin films. The three device classes show high-performance bandpass filter profiles with broad, flat low-transmission sidebands accommodating sharp transmission peaks with their efficiencies approaching 100% with appropriate blending of multiple guided modes. We present three modal coupling configurations forming complex mixtures of two or three distinct leaky modes coupling at different evanescent diffraction orders. These modal compositions produce various widths of sidebands ranging from ~30 nm to ~2100 nm and transmission peak-linewidths ranging from ~1 pm to ~10 nm. Our modal analysis demonstrates key attributes of subwavelength periodic thin-film structures in multiple-modal blending to achieve desired transmission spectra. The design principle is applicable to various optical elements such as high-power optical filters, low-noise label-free biochemical sensor templates, and high-density display pixels.
TL;DR: In this paper, the authors reported a wide tuning range for a swept laser source using deep reactive ion etching on an SoI substrate using a Fabry-Perot filter with a free-spectral range and a tuning range wider than 94 nm.
Abstract: In this letter, we report a wide tuning range MEMS-based swept laser source using deep reactive ion etching on an SoI substrate. A MEMS Fabry-Perot filter with a free-spectral range and a tuning range wider than 94 nm is presented. The measured transmission loss of the filter is between -10.2 and -13.6 dB. This filter is used to construct a swept laser source with 85 nm tuning range. These results represent the widest tuning range reported in literature for an in-plane SoI-MEMS based swept laser source using deeply-etched free-standing distributed-Bragg-reflection mirrors. The recorded tuning range enables the use of the in-plane MEMS filter in optical coherence tomography applications.
TL;DR: In this paper, a detailed understanding of the processes at the target during reactive high power impulse magnetron sputtering (HiPIMS) is presented, based on which the deposition of both low and high-index films and their implementation in optical interference filters with enhanced performance are demonstrated.
Abstract: In this contribution, based on the detailed understanding of the processes at the target during reactive high power impulse magnetron sputtering (HiPIMS), we demonstrate the deposition of both low- and high-index films and their implementation in optical interference filters with enhanced performance. We first investigate strategies for stabilizing the arc-free HiPIMS discharges above Si and Ta targets in the presence of oxygen. We show that hysteresis can be suppressed for these two target materials by suitable pulse-management strategies, ensuring good process stability without having to rely on any feedback control. Afterwards, we discuss the room temperature deposition of optically transparent SiO2 and Ta2O5 single layers as well as the fabrication of SiO2/Ta2O5 stacks such as 7 layer Bragg reflectors and 11 layer Fabry-Perot interference filters. We also analyze the optical and mechanical characteristics of these various coatings and compare them with their counterparts obtained by radio-frequency ma...
09 Mar 2014
TL;DR: The two designs based on conventional common-bus architecture and a new “Mod-MUX” architecture for WDM transmitters are discussed and compared and their complementary merits are highlighted.
Abstract: We demonstrated 320Gb/s 8-channel and 160Gb/s 4-channel WDM transmitter using silicon microrings based on conventional common-bus architecture and a new “Mod-MUX” architecture respectively. We discuss and compare the two designs and highlight their complementary merits.