Hybrid Integration Between Long Focus Microlens Array and IR Detector Array

A special method, named step simulation method, is proposed for fabricating Si microlens array to improve the performance of infrared focal plane array (IR FPA). The focus length of rectangle-based multistep microlens array with element dimension of 40 µm×30 µm is 885.4 µm by the method, which is much longer than the focus length of microlens array fabricated by conventional Fresnel binary optics technique., The large-scale 256×256 element microlens array is hybridintegrated with the PtSi Schottky-barrier IR FPA by optical adhesive. The test results show that diffractive spot size of the microlens is 17 µm×15 µm and the average optical response of the IR FPA is increased by a factor of 2.4.     

Inkjet-printed resistors with a wide resistance range for printed read-only memory applications

Inkjet-printed resistors with resistance values varying over five orders of magnitude were demonstrated on a flexible substrate. The resistivity of printed lines of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was altered by using different ink formulations and by employing an over-print technique, while the length of the printed resistor line remained unchanged. This technique was then applied to fabricate a printed read-only memory device that consisted of an array of resistors. The concept of printing reliable, visually identical resistors with controlled resistance values provides an important building block for low cost, printed electronic circuit applications.     

Joint striping noise removal and background clutter cancellation inIR naval surveillance systems

The clutter removal procedure for infrared (IR) naval surveillance systems presented is designed to manage a typical maritime scenario and is insensitive to the sharp transition between sea and sky across the horizon line. It is also effective for the removal of striping noise which arises as a consequence of the nonuniform calibration of the detector array. The low computational cost of this technique makes it well suited for real-time implementation. The effectiveness of the clutter removal procedure is illustrated on a set of experimental IR data     

X‐Band Phased Array Antenna Using Ferroelectric (Ba,Sr)TiO3 Coplanar Waveguide Phase Shifter

A phased array antenna was fabricated using four‐element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a Ba0.6Sr0.4TiO3(BST)/MgO structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance‐matching‐part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this technique‐adapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X‐band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by 15° in either direction.     

固体浸没式红外超表面透镜设计

红外焦平面阵列在各类红外成像系统中发挥着巨大的作用。为提升红外焦平面的工作温度、量子效率和灵敏度,通常使用微透镜阵列作为红外焦平面的聚光器。当前微透镜阵列的制作材料通常与红外探测器材料不同,因此在集成装配时需要额外的工艺手段,工艺难度较大且效率较低。利用微纳光学超表面技术体系,可以在红外探测器衬底材料上直接制作平面式的固体浸没型微透镜阵列,实现前置微透镜与红外焦平面的单片集成。文中以红外探测领域最有潜力的锑化物Ⅱ类超晶格红外探测器为应用目标,设计了一种基于GaSb衬底的固体浸没式红外超表面透镜。设计的超表面透镜在中波红外波段工作,能适用于所有入射偏振。器件设计焦距为100 μm,理论上在目标波长下的最高聚焦效率达到70.7%,数值孔径(NA)达到1.15。该设计可以推动微透镜阵列向扁平、超薄、轻量的方向发展,简化微透镜阵列与红外焦平面阵列的集成工艺,有望提升红外焦平面的探测效率,并降低制造成本。     

Optical tap array using distributed-index planar microlens

The letter describes a novel optical tap array by using a two-dimensional array of planar microlenses. The present device is used to monitor a part of light which is transmitted through optical fibres. Planar microlenses to focus the light have been monolithically fabricated by the use of the electromigration technique; the focal length is 3 mm and NA is 0.15. The coupling efficiency of the initial device was 52% for coupling multimode graded-index fibres.     

Microstrip antenna array with series-fed `through-element? coupled patches

A new microstrip antenna array with series-fed patches is proposed. To reduce the length of feeding lines the `through-element' feeding technique has been developed. A microstrip patch in which the input feeding line is directly connected and the output line is coupled to a patch is investigated. By adjusting the length of the coupling region an appropriate coupling level is achieved. A 4times1 antenna array operating within the 24 GHz frequency band for radar sensor applications is designed using the proposed feeding technique     

Full Schottky high density 2-D infrared charge coupled detector array

Conventional silicon based infrared (IR) detector arrays consist of separate Schottky barrier detectors connected via transfer gates to MOS type charge coupled device (CCD) read-out shift registers. A novel IR imaging array is described where Scottky silicide elements are used exclusively both as IR detectors as well as the silicide gates of Schottky CCD read-out shift registers. Advantages of the novel structure are a high packing density of IR detectors with high fill factor, simplicity of the device layout and possible high fabrication yield.     

High-selectivity single-chip spectrometer in silicon for operationin visible part of the spectrum

A microspectrometer has been realized based on an array of Fabry-Perot optical thin-film filters. The 16-channel microspectrometer is compatible with IC fabrication methods and operates in the visible spectral range with an interchannel shift of 6 nm. Each of the channels is sensitive in a single peak with full-width-half-maximum (FWHM) of 16 nm. Also a FWHM below 2 nm and finesse of 40 for narrow band operation is demonstrated. The device can easily be tuned during fabrication to cover a different spectral band only by adjusting the etching times without affecting the device layout. Such a device is extremely suitable for applications in microsystems because of its small size, high spectral selectivity, and low cost. Microspectrometers for the UV and IR regions are also feasible using this technique     

双材料微梁阵列非制冷红外成像系统——微梁阵列的设计与制作

给出了一种用于非制冷光学读出红外探测器的核心器件--双材料微悬臂梁阵列的设计和制作.微梁阵列是无硅基底的SiNx/Au双材料单层膜结构,其制作工艺简单、可以直接放在空气中成像.实验使用了设计制作的140×98微梁阵列和高信噪比的12-bit CCD,得到120℃以上的物体热像,噪声等效温度差(NETD)为7K左右,实验结果与热机械模型预测结果一致.     

A new technique for in-fixture calibration using standards ofconstant length

This paper presents a new technique for in-fixture calibration using standards of constant length. The technique uses a through line, reflective load, symmetric two-port at a reference position, and the same two-port at a different position, all produced on substrates of the same electrical properties and physical length. When compared with the through-reflect line (TRL) technique, this one eliminates the need for a length change during calibration and device measurements while retaining comparable accuracy. Moreover, in contrast with the line-network network (LNN) technique, it provides easy resolution of all error coefficients without ambiguities and does not require physical movement of a reference two-port, but reproduction of a reference two-port on microwave integrated circuit (MIC) substrates, which is easy to realize. All these features make the new technique useful for in-fixture measurements requiring a constant distance between input and output connections. The validity of the proposed technique is illustrated by experimental results     

Linear High-Tc YBa2Cu3O7−δ Superconducting Thin Film Infrared Detectors Coupled with a Cylindrical Microlens Array in Quartz Glass Substrate

Monolithic linear cylindrical microlens array in a quartz glass substrate is fabricated using photolithography and ion beam etching technique, the high-Tc YBa₂Cu₃O_7?δ superconducting thin films are deposited through excimer laser scanning ablation, the superconducting thin films are patterned by photolithographic method and ion beam etching technique, and the hybrid structure of the microlens array component and the superconducting IR detectors has been obtained using an IR glue to cement the microlens component onto the superconducting device. We also investigate the optical response characteristics of the hybrid device in the optical spectral region of 1 ~ 5 μm, as follows. The average optical responsivity $(\overline R )$ of the hybrid device is 1.6×10⁴ V/W, average noise equivalent power $(\overline {NEP} \;)$ is 2.3×10^?12 WHz^?1/2, average detectvity $(\overline {D^ * } )$ is 3.2×10⁹ cmHz^1/2W^?1, and the non-uniformity of detectvity (D*) is not more than 14%. The experimental results show that the performance of the superconducting device is improved notably using a quartz glass refractive microlens array as the incident IR radiation concentrators.     

Highly Efficient Top-Emitting Infrared-to-Visible Up-Conversion Device Enabled by Microcavity Effect

Infrared (IR)-to-visible up-conversion device allows a low-cost, pixel-free IR imaging over the conventional expensive compound semiconductor-based IR image sensors. However, the external quantum efficiency has been low due to the integration of an IR photodetector and a light-emitting diode (LED). Herein, by inducing a strong micro-cavity effect, a highly efficient top-emitting IR-to-visible up-conversion device is demonstrated where PbS quantum dots IR-absorbing layer is integrated with a phosphorescent organic LED. By optimizing the optical cavity length between indium tin oxide (ITO)/thin Ag/ITO anode and semi-transparent Mg:Ag top cathode, the up-conversion device yields 15.7% of photon-to-photon conversion efficiency from the top-emission. The high efficiency can be achieved under a low IR transmission through the semi-reflective anode. Finally, pixel-free IR imaging is demonstrated using the up-conversion device, boosting the effect of micro-cavity on the brightness and the contrast of an IR image.     

Gate-modulation imaging of organic thin-film transistor arrays: Visualization of distributed mobility and dead pixels

We report on the application of the gate-modulation (GM) imaging technique in rapid and collective inspection of organic thin-film transistor (OTFT) array operations. The method allows visualizing charge carriers accumulated in the OTFT array by time-translational differential image sensing with the use of a charge coupled device (CCD) sensor. The feature makes it possible to visualize the dead pixels, broken channels, or distributed device performance in the OTFT array. We discuss how to correlate the spectroscopic information of GM signal with the device performance and how to use this technique in the collective inspection of OTFT arrays.     

On-die diffractive alignment structures for packaging of microlens arrays with 2-D optoelectronic device arrays

A novel technique for aligning a microlens array to an electrically packaged optoelectronic device array is presented: reflective Fresnel zone plates (FZP's) are fabricated on the device die to provide registration spots during alignment. A proof-of-concept experiment in which an MSM array was aligned to a microlens array with an accuracy of better than 9 microns is described.     

Correlation of laser-beam-induced current with current-voltage measurements in HgCdTe photodiodes

Laser-beam-induced current (LBIC) is being investigated as an alternative to electrical measurements of individual photodiodes in a two-dimensional array. This is possible because LBIC only requires two electrical contacts to an array and the two-dimensional scanning of a focused laser beam across the array to image the entire array. The measured LBIC profiles, obtained from linear arrays of HgCdTe photodiodes, will be used to study the uniformity of photodiodes in the array and to extract the R₀A of the photodiodes. It will be shown that the shape of the LBIC signal is correlated to the electrical performance of the photodiode, with R₀A related to the spreading length of the photodiodes. Linear arrays of n-on-p, mid-wavelength infrared (MWIR) and long wave-length infrared (LWIR) devices were formed in liquid-phase epitaxy HgCdTe epilayers using a plasma junction-formation technique. The LBIC profiles were measured on each of the devices at various temperatures. For the MWIR devices, the extracted spreading length shows no correlation with R₀A. However, the LBIC signal does detect nonuniform devices within the array. For the case of the LWIR devices, the spreading length is extracted as a function of temperature, with the R₀A subsequently calculated from the spreading length. The calculated R₀A, obtained without requiring contact to each photodiode in the array, agrees well with electrical measurements. Asymmetry of the LBIC signals for certain devices in the arrays is shown to be a result of localized leakage at the photodiode junction or from the contact pads through the passivation layers. These results are confirmed by numerical modeling of the device structures.     

Design and Fabrication of Silcon Microlens with Low SAG for 528(H) × 528(V) Infrared Charge-Coupled Device Application

Microlens array is an important optical element to improve the photosensitivity of charge-coupled device (CCD). In this paper, a monolithic integration technology between microlens and 528 × 528 element PtSi Schottky-barrier infrared charge-coupled device (IRCCD) with a pixel size of 30μm × 30μm has been developed. The microlens array with low sag and long focal length is designed based on geometrical optics theory. It is directly formed on the back side of the substrate in IRCCD chip using successive photolithography and A⁺ ion beam etching (IBE) technology. The microlens array is characterized by both surface stylus and point spread function (PSF). The experiment results of integration device between IRCCD and microlens array indicate that the optical signal response is improved obviously and a responsivity increase by a factor of 1.8 in the operation band.     

InSb charge-injection device imaging array

InSb CID arrays, in both 1 × 32 line and 16 × 24 two-dimensional format, have been successfully fabricated via a multilayer MIS processing technique. With the 1 × 32 line arrays, two-dimensional images were generated using a scanning mirror and a computer signal-conditioning technique. In this experiment the small temperature difference of a man's face was revealed. Two-dimensional, 16 × 24 area arrays have also been demonstrated in a staring mode by displaying real time raster-scanned IR images directly on a X-Y CRT monitor. The unprocessed IR video signal produced a sharp, clearly recognizable display with no sign of blooming, and exhibited excellent operating characteristics. Theoretical analysis showed that, at low sample rates, background limited performance (BLIP) can be obtained at background photon flux levels of as low as mid-10¹²photons/s . cm². The dominant noise source, in this case, is the integrated dark current shot noise. For operation at high sample rates, however, the bandwidth-dependent noise sources limit the array performance and, thus, BLIP occurs at higher background levels. The analysis has been confirmed by measured data on line arrays, resulting in good agreement between the theoretical curve and the experimental data.     

InSb Charge-Injection Device Imaging Array

InSb CID arrays, in both 1 X 32 line and 16 X 24 two-dimensional format, have been successfully fabricated via a multilayer MIS processing technique. With the 1 X 32 line arrays, two-dimensional images were generated using a scanning mirror and a computer signal-conditioning technique. In this experiment the small temperature difference of a man's face was revealed. Two-dimensional, 16 X 24 area arrays have also been demonstrated in a staring mode by displaying real time raster-scanned IR images directly on a X - Y CRT monitor. The unprocessed IR video signal produced a sharp, clearly recognizable display with no sign of blooming, and exhibited excellent operating characteristics. Theoretical analysis showed that, at low sample rates, back-ground limited performance (BLIP) can be obtained at background photon flux levels of as low as mid-10/sup 12/ photons/s /spl dot/ cm/sup 2/. The dominant noise source, in this case, is the integrated dark current shot noise. For operation at high sample rates, however, the bandwidth dependent noise sources limit the array performance and, thus, BLIP occurs at higher background levels. The analysis has been confirmed by measured data on line arrays, resulting in good agreement between the theoretical curve and the experimental data.     

Theory and performance of perpendicular diffraction delay lines

The perpendicular diffraction delay line was introduced recently as a new method for obtaining a linear variation of delay time with frequency. Basically, it consists of a transmitting array and a receiving array having elements with suitable nonuniform spacings, arranged perpendicular to each other. The dispersion arises because the effective path length of an ultrasonic beam between the input and output arrays changes with frequency. This paper presents a quantiative analysis of the perpendicular diffraction delay line together with experimental results obtained from a 2.2 Mc/s model. Also included is a complete design procedure based on interference theory. The theoretical analysis indicates that the device is capable of performing satisfactorily in any frequency range with fractional bandwidths up to 50 per cent. Measurements made on the experimental model are in good agreement with the theory.