An innovative integrated spatial filter array (iSFA) was developed for the nulling interferometer for the detection of earth-like planets and life beyond our solar system. The coherent iSFA comprised a 2D planar lightwave circuit (PLC) array coupled with a pair of 2D lenslet arrays in a hexagonal grid to achieve the optimum fill factor and throughput. The silica-on-silicon waveguide mode field diameter and numerical aperture (NA) were designed to match with the Airy disc and NA of the microlens for optimum coupling. The lenslet array was coated with a chromium pinhole array at the focal plane to pass the single-mode waveguide but attenuate the higher modes. We assembled a 32 by 30 array by stacking 32 chips that were produced by photolithography from a 6-in. silicon wafer. Each chip has 30 planar waveguides. The PLC array is inherently polarization-maintaining (PM) and requires much less alignment in contrast to a fiber array, where each PM fiber must be placed individually and oriented correctly. The PLC array offers better scalability than the fiber bundle array for large arrays of over 1,000 waveguides.
This paper surveys the need for oxygen A-band spectroscopy to improve our understanding of clouds and their key role in the climate system. We then report on a novel holographic A-band substrate-guided spectrometer device recently developed at Luminit. This A-band spectrometer prototype is based on an innovative structure of two thick reflection substrate-guided wave-based holograms (SGWHs) that act as dispersive and/or imaging elements to enable a sufficient spectral resolution. The technology is made very attractive by its significantly lower cost compared to currently available systems/devices with similar A-band capability, while providing higher light throughput, a better out-of-band rejection ratio, higher resolution at a smaller size, and better stability and reliability.
We demonstrate a novel hybrid solar photovoltaic electrical and thermal energy cogeneration system with high
efficiency, at potentially reduced overall weight and size compared with current solar energy systems. The new system is
based on highly efficient photovoltaic solar cells and tubular water thermal receivers, incorporating holographic spectral
beam light guide concentrators resulting in a more cost-effective solution. Details of fabrication and preliminary
experimental testing results are presented.
We demonstrate a novel spectral imaging device based on an imaging Fourier transform spectrometer (FTS) with phase
delays electro-optically controlled by fast tuning liquid crystal (LC) elements. The electro-optic (EO) tunable
multispectral/hyperspectral imaging give the spectral imager significant advantages, including reduction in size and mass
for simultaneous 2D spectral imaging, with a high spatial and spectral resolution. The technology is made very attractive
for its potential military, medical and remote sensing applications where hyperspectral imaging plays a significant role in
We demonstrate a new material composed of isotropic liquid crystal (ILC) blended with semiconductor nanoparticles,
which could result in a novel high-speed, multiple-notch broadband passive optical switch to selectively discriminate
bands of electromagnetic radiation in intelligence, surveillance, or reconnaissance systems. The new material has been
demonstrated high nonlinear 3rd order optical Kerr coefficients (light-induced refractive index change, n2) exceeding 100
times of classic nonlinear material CS2 with n2 = 1.2E-11 esu. Details of fabrication and experimental results are
Image intensifier tubes, as part of night vision devices, have been the primary devices for the detection and amplification
of near infrared light for night vision operations. In this paper, we demonstrate a novel all-optical night vision amplifier
device with a potential to replace the image intensifier tube in night vision goggles. This image amplifier is based on a
novel structure of semiconductor and spectrally tunable liquid crystal (LC) materials within a thin cell. The LC reacts to
near-infrared (NIR) radiation but is unaffected by visible light, allowing see-through capability including visible-wavelength
cockpit light. The technology is made very attractive by its high sensitivity, spatial resolution, and contrast
without expensive, bulky, and heavy optics or high-voltage components.
JPL and BNS Inc. are jointly developing a compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications . The spectral region of this spectrometer is in the near IR spectral band of 1 - 2.5 μm (1000 - 4000 cm-1) to allow high-resolution, high-speed hyperspectral imaging applications. The specific applications for NASA’s missions will focus on the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders (YVO4) and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent technical progress will be presented.
In recent years, optical CDMA systems have been proposed for multiple accesses to utilize the vast bandwidth available in optical fiber. Optical CDMA systems are believed to provide asynchronous access for each user in the system, which is especially suitable for usage in LAN. In this paper, we demonstrate a novel optical CDMA scheme in a fiber-based testbed. Using the liquid crystal spatial light modulator (SLM), we are able to construct a reconfigurable optical CDMA system suitable for fiber-optic networks. We address the code for each user in the spectrum domain by using a standard 4-f pulse shaping apparatus. Because of the low coherency of the light source we used in the system, we are able to modulate it in time domain without changing its frequency distribution significantly. We can reconfigure the network connection while keep the information bits un-influenced. Another merit of using analog liquid crystal device is that the transmissions of the different frequency components are analog controllable, we can get a uniform intensity distribution in frequency domain when the spectrum of the light source is not flat. Using the liquid crystal as a programmable optical modulator, the high polarization sensitivity of the components used in the system enables low crosstalk between different codes assigned to different users.
JPL and BNS Inc. are jointly developing a compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications. The spectral region of this spectrometer will be 1 - 2.5 μm (1000 - 4000 cm-1) to allow high-resolution, high-speed hyperspectral imaging applications. The specific applications for NASA's missions will focus on the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent experimental progress will be presented.
Optical CDMA technology has shown promise in optical communications, particularly in local-area optical fiber networks. We present a novel O-CDMA scheme with programmable and reconfigurable bipolar code capability using liquid crystal (LC) Spatial Light Modulators (SLMs). The key to our system performance depends on constructing a decoder that implements a true bipolar correlation using only unipolar signals and intensity detection. This has been accomplished using two unipolar correlations that can be performed optically, followed by a subtraction. In our coding system, the power spectrum of a broadband light source is encoded and decoded by programming the SLMs. The high polarization selectivity of these components coupled with the polarization rotation ability of liquid crystal elements makes switching possible with high extinction ratio and low crosstalk. Experimental results including the correlation measurements are presented. Good contrast between the autocorrelation and cross correlation values shows that a binary information symbol can be recovered by an appropriate threshold operation.
Improvements in silicon foundry processes have made possible high-resolution, light-efficient backplanes capable of driving electro-optic modulators with higher voltage signals. The higher voltage provides the excitation to achieve sub-millisecond response times with a wave of phase modulation when used with dual-frequency nematic liquid crystals. By combining dual-frequency phase modulators with high-voltage silicon backplanes, compact spatial light modulators become available for applications that need fast, high-throughput modulators such as optical signal processing, adaptive wavefront correction, optical signal routing or beamsteering, and active diffractive optics.
Liquid crystal tunable filters are gaining wide acceptance in such diverse areas as optical fiber communications, astronomy, remote sensing, pollution monitoring, color generation for display and medical diagnostics. The large aperture and imaging capability of liquid crystal tunable filters represent a distinct advantage over conventional dispersive spectral analysis techniques. Furthermore, benefits of liquid crystal tunable filters over acousto-optic tunable filters include low power consumption, low addressing voltage, excellent image quality and large clear aperture. We discuss polarization interference filters based on liquid crystal tuning elements. While liquid crystal tunable filters based nematic liquid crystal, using Fabry-Perot and polarization interference effects are commercially developed, only recently has the emphasis been on liquid crystal tunable filters to include current novel developments in high-speed, analog ferroelectric-liquid crystals (FLCs). Compared to nematic liquid crystal, FLC-based tunable optical filters offer fast response time and increased field-of-view.