High-Precision Alignment Method for Electro-Optic Modulators via Combined Twyman-Green and Conoscopic Interferometry

Microwave wireless and optical fiber technologies are widely used for several applications in communication, sensing, imaging, and so on. We propose an electro-optic (EO) modulator with a planar stripline feed to a gap-embedded patch-antenna for hybrid uplinks to an optical fiber and microwave wireless networks. The proposed device is designed on an EO crystal with simple and compact structure. The gap-embedded patch-antenna on the EO modulator can be operated for optical modulation to the optical fiber network. The proposed device can be also operated for microwave transmission to the air or wireless networks. Characteristic and analysis of the designed device for optical modulation and wireless microwave transmission are reported and discussed.

It is known that when the incident power is large, the extinction ratio of electrooptic light modulators declines due to the thermally induced birefringence accompanying the absorption of light in the electrooptical crystals. The decline of the extinction ratio is analyzed. The important characteristics of the decline of the extinction ratio are the following. 1) It is independent of the beam radius or the surrounding temperature. 2) The decline can be reduced by simple methods such as thermal compensation. The results obtained by the analysis agree well with the experiment. From these results, it can be concluded that electrooptical light modulators constructed with materials like KDP, ADP, etc., can handle considerably high input power. This effect places an upper limit on the amount of power that can be handled by electrooptic modulators using naturally birefringent crystals.

Optimizing low half-wave voltage electro-optic polymer modulator for optical waveguide sensor

In the space laser communications, Information transmission by atmospheric turbulence and background light and other atmospheric interference of the random channel. Resulting in the optical axis alignment accuracy decreased. In order to improve the alignment accuracy of the optical axis, Proposing the Gaussian fitting matching algorithm. Outdoor experiments confirmed the Gaussian fitting matching algorithm to ensure a stable spot image.

This paper presents a vision system designed for an underwater robot to facilitate measuring the distance to an inspected surface and its orientation with respect to the robot. The system uses a set of laser modules to project a rectangular dot pattern on the inspected surface. The vision system is used to measure the dots’ locations in the 3D space and calculate the distance to the surface, together with the pitch angle and the yaw angle of the camera. A novel calibration procedure is presented, which allows for constructing high resolution camera-laser systems, without requiring a perfect alignment of laser beams and camera optical axis. An underwater vision system simulation environment, based on open-source software, is also introduced and extensively used to test the developed algorithms. The experimental results, obtained in a laboratory tank and a pool, confirm high performance of the system.

Abstract. Overlap between two convergent images for close-range terrestrial photogrammetry is a pre-requisite for view planning of building corners. Available tools determine overlap of images that are acquired by normal geometry at a constant distance. However, for the convergent images lengths of image footprints vary according to camera position. The paper proposes a field-based method that requires to measures only geometric dimensions of image footprints in field for assessing overlap fractions for convergent images. The paper first derives the overlap fraction of convergent images as a function of image footprints, which depend upon the camera position, object geometry, and camera FOV. Experiments are conducted in field for two building corner sites. The proposed method provides conservative estimates of overlap fractions compared to that provided by image-based methods. The errors in the overlap fractions are contributed by three sources, namely, the approximations of the proposed method, uncertainty in camera positions and alignment of camera optical axis, and placement of markers in field. Experimental results suggest that the proposed method can be used confidently in field for overlap estimation for convergent images for the view planning. Images acquired for the view planning of the two corners successfully generated 3D models.

A flextensional microactuator has been designed and fabricated for the amplification of the small strain of the piezoelectric materials to achieve large displacements. Bulk PZT material available in the form of 500 µm thick polished substrate has been integrated with a precision micromachined silicon beam structure to achieve the clamped–clamped flextensional microactuator. A high strength, high precision (alignment) and low temperature (∼200 °C) In/Sn solder bonding process has been developed and used for the fabrication of the flextensional microactuators. Actuators with physical dimensions of the flextensional structure ranging from 350 to 600 µm in length, 50 to 100 µm in width and 5 to 6 µm in thickness were fabricated. The measured static deflection characteristics of the silicon micromachined beam show a flextensional gain factor of 20 with a large amplitude stroke of ∼8 µm when actuated using −100 V to 100 V. The bandwidth of the actuator was experimentally measured to be 265 kHz. The fabricated devices show good repeatability with a hysteresis pattern arising from the PZT characteristics. The bonding technique described here can be used for the precision integration of heterogeneous materials for MEMS device fabrication and their packaging.

Recent efforts in our group towards the fabrication of sensors capable of detecting passive levels of millimeter-wave radiation have led to the development of an optically-based detector with sub-picowatt noise equivalent powers. This sensor is based on upconverting the received radiation into sidebands on an optical carrier using electro-optic modulation techniques and, subsequently, suppressing the remaining carrier energy. The noise equivalent power of such detectors is critically dependent on the ability of the electro-optic modulator to efficiently convert frequencies up to and exceeding 95 GHz onto the optical carrier while suppressing potential noise sources. In this paper, we discuss the specific device requirements generated by this unique potential application of high-frequency optical modulators. The effects of various modulator properties, such as half-wave voltage, frequency response, and maximum optical power density are discussed in the context of millimeter-wave detection capability. In addition, we present experimental efforts towards fabricating a passive millimeter-wave detector based on this approach, including efforts to develop an optimized optical modulator technology.

A variational method coupled to spectral domain technique is used for the analysis of multilayered anisotropic microwave structures for various applications including MICs and electro-optic modulators. The most useful parameters of a variety of planar transmission lines in isolated and coupled configurations, with anisotropic substrates having aligned or tilted optical axis, are computed. Using the variational method in conjunction with the transverse transmission-line technique, the analysis reduces to the determination of a single admittance parameter. This parameter can be obtained from the transmission-line equivalent circuit of the structure almost by inspection.

Thin-film lithium niobate (TFLN) electro-optic modulators (EOMs) offer distinct advantages, including high speed, broad bandwidth, and low power consumption. However, their large size hinders the density of integration, which trades off with the half-wave voltage. Photonic crystal (PC) structures can effectively reduce the device footprint via the slow-light effect; however, they experience significant losses due to fabrication defects and sharp corners. Here, we theoretically demonstrate an ultracompact Mach–Zehnder interferometer (MZI) EOM based on a TFLN valley photonic crystal (VPC) structure. The design can achieve a high forward transmittance (>0.8) due to defect-immune unidirectional propagation in the VPC, enabled by the unique spin-valley locking effect. The EOM, with a small footprint of 21 μm × 17 μm, achieves an extinction ratio of 16.13 dB and a modulation depth of 80%. The design can be experimentally fabricated using current nanofabrication techniques, making it suitable for broad applications in optical communications.

Electro-optic (EO) modulators encode electrical signals onto fiber optic transmissions. High drive voltages limit gain and noise levels. Typical polymeric and lithium niobate modulators operate with halfwave voltages of 5 volts. Sterically modified organic chromophores have been used to reduce the attenuation of electric field poling-induced electro-optic activity caused by strong intermolecular electrostatic interactions. Such modified chromophores, incorporated into polymer hosts, were used to fabricate EO modulators with halfwave voltages of 0.8 volts (at a telecommunications wavelength of 1318 nanometers) and to achieve a halfwave voltage-interaction length product of 2.2 volt-centimeters. Optical push-pull poling and driving were also used to reduce halfwave voltage. This study, together with recent demonstrations of exceptional bandwidths (more than 110 gigahertz) and ease of integration (with very large scale integration semiconductor circuitry and ultra-low-loss passive optical circuitry) demonstrates the potential of polymeric materials for next generation telecommunications, information processing, and radio frequency distribution.

In this framework, our interest has been focused to the thermo-optic behaviour of an EO modulator crystal as it is expressed by the influence of temperature T on crystal’s optical or electro-optical parameters such as the refractive indices, n 0 and n e , the effective EO coefficient r, the spontaneous birefringence !n(0), the half-wave voltage V , the optical phase retardation #, and the intensity-modulation (IM) depth m of the entire EO-modulation system. After a brief presentation of typical configurations of IM systems, we define the principal thermo-optic and temperature coefficients and we derive useful general equations connecting these parameters in the entire system. Then we present investigations of these equations as regards the above parameters along with calculations of the uncertaintities in the determination of temperature coefficients for the effective EO coefficient r, the half-wave voltage V , and the IM depth m. It is of note that in this publication, the theoretical analysis of the thermo-optic effects in an electro-optic modulation system is only presented. In the experimental field, a determination of various TO coefficients of LiTaO 3 made by the authors, in the case of a transverse EO configuration, has been already published elsewhere [3].

For some electro-optic (EO) modulators, lowering the driving voltage is necessary to reduce the power consumption of the modulators. There are four significant factors influencing the driving voltage of the EO modulators: geometrical parameters of wafer and electrodes, surface and embedded electrodes, material properties of wafer, and structure of modulators. Using the superposition method and surface charge technique, the electric fields, halfwave voltages, switching times and optical transmissions of EO modulators with two-layer, three-layer, and four-layer electrodes are calculated, respectively. It is found that the halfwave voltage decreases while the switching time increase slightly as the number of layers increases. Such study demonstrates that using multilayer electrodes is an effective technique of lowering the halfwave voltage, which may have implication of EO modulator design.

In this paper, the development of a new optical chip in board (CiB) package adapting Fan-out technology that offers thermal, electrical and thin structure benefit was reported. Optical CiB package contain 4 optical die and is made smaller and thinner than market with the redistribution layer technology of FO-WLP. The key advantages such as high production yield, low cost and simple process steps surpass the conventional optical packages that depends on high precision alignment but always difficult to achieve good performance. Through finally demonstrated that communication is possible at the target speed of 10Gbps/Ch through actual measurement. In this paper describes the structural features of Embedded optical CiB package with integration of nepes'Fan-out technology.

There has been many ways of finding out the focal plane of laser projection imaging system. However we use a new aligning way to get the optimum figure of the developed substrates through a microscope. In this paper, it is demonstrated that the range of depth of focus (DOF) changes together with the feature size in a way of positive correlation. This result can be used to figure out the shortest path to the focal plane. Thus a new way of aligning the focal plane for the LPI system is presented. We also test this system. It is found that the alignment precision is 2µm, adjustable range 2mm in the optical axis. Simultaneously the focal plane and the DOF can basically meet the demands in technical specification.