Principle and Application of a Sensitive Handy Electrooptic Probe for Sub-100-MHz Frequency Range Signal Measurements

We have developed a new handy electrooptic (EO) probe to measure signals whose frequency is lower than 100 MHz. A distinct feature of the new EO probe is a long metal rod attached to an EO modulator. Measurement sensitivity does not depend on geometrical structures of devices under test (DUTs) with our new EO probe, whereas it does depend on geometrical structures of DUTs with a conventional handy EO probe. The sensitivity is at least 18 dB higher than that of the conventional one. In this paper, we qualitatively explain the effects of the rod on sensitivity and show experimental results, which agree well with the explanation. The advantages of signal measurements with an EO probe are also discussed, and two applications, where an EO probe plays important and essential roles, are proposed.     

A compact self-shielding prober for accurate measurement ofon-wafer electron devices

A compact self-shielding prober is proposed for measuring low-current-voltage characteristics of on-wafer electron devices. In the prober, a wafer and a wafer stage are set in a very small shielded region mostly enclosed by a plane top-board, a wafer-stage shield, and a sidewall shielding ring. A current of less than a picoampere can easily be measured without any shielding box. A prober designed to observe all devices on 4-in wafers can be as small as 27 cm×27 cm×12 cm. High-speed input/output waveforms of on-wafer large scale integrated circuits (LSIs) observed with this prober are as clear as those of packaged LSIs observed directly     

All-Dielectric Electrooptic Sensor Based on a Polymer Microresonator Coupled Side-Polished Optical Fiber

A novel electrooptic (EO) electric field (E-field) sensor based on side-polished fiber coupled with an EO polymer microring resonator is proposed and demonstrated. An EO polymer waveguide with a ring shape is fabricated on the polished flat of an optical fiber. Light in the fiber evanescently couples into the resonator and forms resonant modes for certain wavelengths and produces notches in the output intensity of the fiber. External electric fields change the index of refraction of the ring waveguide and therefore dither its resonant wavelengths. For light of wavelength on the slope of a resonance notch, a change in the output intensity can be detected. The sensor is all dielectric without metal layers to distort the measured E-field. The resonant structure allows the sensor to potentially have much higher sensitivity than other electrooptic sensors based on Mach-Zehnder or polarization modulation. Since electrooptic polymers have higher electrooptic coefficients, lower dielectric constants and faster electrooptic responses than inorganic crystals, higher sensitivity, lower invasiveness, and higher bandwidth of E-field sensing can be expected. This sensor eliminates unreliable fiber-to-waveguide butt coupling as well as the high propagation loss encountered in the long straight EO polymer waveguides of sensors based on Mach-Zehnder structures. By using the fiber itself as the supporting substrate of the ring waveguide, the sensor can have small size and low disturbance to the measured electric field. The concept is demonstrated using AJLS103 EO polymer. A sensitivity of 100 mV/m has been achieved at frequencies up to 550 MHz (limited by the measurement system)     

Sampling and real-time methods in electro-optic probing system [LSItesting]

Sampling and real-time methods in electro-optic (EO) probing systems using a laser diode (LD) for measuring the voltage waveform at internal nodes of the high-speed LSI are described, comparing performance to other electric instruments. The voltage sensitivity was improved by using an external ZnTe E-O probe and a low-noise LD. A sampling system using a pulsed LD has a frequency bandwidth of 10 GHz and a minimum detectable voltage of 430 μV/√Hz. The corresponding values for a real-time system using a CW LD and a high-speed photodetector are 480 MHz and 23 mV with 700 accumulations. Each system is based on a mechanical prober and a microscope. The advantages of a high temporal resolution, noncontact and noninvasive method are demonstrated during various measurements in several different areas: standing waves on a stripline, ring resonator and voltage waveform characteristics in a high-speed MMIC by the sampling method, long logic pattern signal, voltage waveforms at internal nodes in an ECL IC and those of a transport electrode in CCD by the real-time method     

A real-time electro-optic handy probe using a continuous-wave laser

This paper describes a real-time electro-optic (EO) probe system that can be directly connected to digital oscilloscopes, spectrum analyzers, and other widely used instruments. The probe incorporates a balanced optical receiver with two high-speed InGaAs p-i-n photodetectors (PDs) to reduce noise, and optical isolators to decrease the light reflected from the optics back to the laser diode (LD). To increase sensitivity, we employ cadmium telluride (CdTe), which has a large EO coefficient, and a high-power 1.3-μm distributed-feedback (DFB) LD as a continuous-wave (CW) laser source. We used it to measure eye diagrams at 1 Gb/s that were displayed on a digital oscilloscope. In addition, when connected to a spectrum analyzer, the probe significantly simplifies frequency-domain analysis. We demonstrate the measurement of electric nearfield distribution radiating from a two-layer printed circuit board (PCB) and a cellular phone. The result shows that the probe system is a potential candidate for electromagnetic interference (EMI) instruments     

Efficiency of electrooptic spin-to-orbital angular momentum conversion in crystals

We introduce a figure of merit for the photon spin-to-orbital angular momentum conversion via electrooptic (EO) Pockels effect in single crystals. Relations for the effective EO coefficients are derived for different symmetry groups. We show that Bi₁₂TiO₂₀ crystals reveal the highest figure of merit among well studied crystalline EO materials. The efficiency of the spin-to-orbital angular momentum conversion is measured experimentally for a number of single crystals.     

Electric Field Sensing Scheme Based on Matched $ hbox{LiNbO}_{3}$ Electro-Optic Retarders

In this paper, a wideband-electric-field-sensing scheme that uses optically matched integrated optics electrooptic devices and coherence modulation of light is described. In a coherence modulation scheme, the integrated optics sensor detects the electric field and imprints it around an optical delay. The optical delay is generated by a birefringent optical waveguide in a lithium niobate (LiNbO₃) integrated optics two-wave interferometer. The modulated optical delay, acting as an information carrier, is transmitted through an optical fiber channel. At the receiver, light is demodulated by a second integrated optics two-wave interferometer, which also introduces a second optical delay. The optical delays on the sensor and demodulator are matched at the same value. The integrated optics demodulator measures the autocorrelation of light around the optical delay value, and the imprinted electric field is recuperated as a linear variation of the received optical power. The matching of the sensor and demodulator allows a direct detection of the electric field, giving a unique feature to this fiber-integrated optics scheme. The experimental setup described here uses two pigtailed LiNbO₃ electrooptic crystals: one acting as the electric field sensor and the other acting as the optical demodulator. The wideband sensing range on the experimental setup corresponds to frequencies between 0 and 20 kHz.     

A high-voltage electrooptic drive amplifier using a power MOSFETpair

A transformless high-voltage low-current push-pull amplifier using a DMOS (TMOS) power FET pair and capable of driving usual electrooptic (EO) loads with good linearity and sufficient bandwidth is presented. The implemented system provides a low-offset floating output up to 780 V point-to-point (p-p) maximum amplitude (1% distortion limit) for a differential input up to 7.0 V p-p. The maximum, open-circuit gain-bandwidth product for the stage exceeds 1.5 GHz, and its bandwidth decreases from 3.2 MHz to 200 KHz when the load capacitance C _L increases throughput the range of usual EO loads (4-100 pF). The noise contamination is sufficiently low, the maximum output SNR (signal-to-noise ratio) exceeding 70 dB     

Comparison of parallel-plate and in-plane poled polymer films for terahertz sensing

We have performed calculations and measurements of the efficacy of two poling geometries of poled electro-optic (EO) polymer films for use in sensing terahertz (THz) radiation via EO sampling. Taking reflective and absorptive losses into consideration, we find that a parallel-plate (PP) poled film has a sensitivity maximum when oriented at 55 degrees to the incident probe and THz beams. In addition, we show that our in-plane (IP) poled polymer films are comparable in sensitivity to PP-poled films and discuss the potential for improving IP-poled polymer devices.     

Modeling of scattering and depolarizing electro-optic devices. I. Characterization of lanthanum-modified lead zirconate titanate

We describe a new method of modeling electro-optic (EO) devices, such as lanthanum-modified lead zirconate titanate polarization modulators, that resolves two deficiencies of current methods: (i) the inclusion of depolarization effects resulting from scattering and (ii) saturation of the EO response at strong electric-field strengths. Our approach to modeling depolarization is based on describing the transmitted optical field by superposition of a deterministic polarized wave and a scattered, randomly polarized, stochastic wave. Corresponding Jones matrices are used to derive a Mueller matrix to describe the wave propagation in scattering and depolarizing EO media accurately. A few simple optical measurements can be used to find the nonlinear behavior of the EO phase function, which is shown to describe accurately the material's EO behavior for weak and strong applied electric fields.     

Proposal and testing for a fiber-optic-based measurement of flow vorticity

A fiber-optic arrangement is devised to measure the velocity difference, deltav(l), down to small separation l. With two sets of optical fibers and couplers the new technique becomes capable of measuring one component of the time- and space-resolved vorticity vector omega(r, t). The technique is tested in a steady laminar flow, in which the velocity gradient (or flow vorticity) is known. The experiment verifies the working principle of the technique and demonstrates its applications. It is found that the new technique measures the velocity difference (and hence the velocity gradient when l is known) with the same high accuracy and high sampling rate as laser Doppler velocimetry does for the local velocity measurement. It is nonintrusive and capable of measuring the velocity gradient with a spatial resolution as low as ~50 mum. The successful test of the fiber-optic technique in the laminar flow with one optical channel is an important first step for the development of a two-channel fiber-optic vorticity probe, which has wide use in the general area of fluid dynamics, especially in the study of turbulent flows.     

Responsivity optimization and stabilization in electro-optic field sensors

Electro-optic (EO) modulation devices, which utilize an external electric field to modulate a beam of optical radiation, are strongly affected by parasitic effects, which change the polarization state of the optical beam. As a result, very small changes in the birefringence or optical path length within the EO material can result in very large fluctuations of the amplitude and phase of the optical modulation signal. A method of actively analyzing the modulated beam is described and demonstrated, which eliminates these fluctuations and keeps the modulation device stably operating at its peak responsivity. Applications to electric field detection and measurements are discussed.     

Lensed fiber probes designed as an alternative to bulk probes in optical coherence tomography

We demonstrate a compact all-fiber sampling probe for an optical coherence tomography (OCT) system. By forming a focusing lens directly on the tip of an optical fiber, a compact sampling probe could be implemented. To simultaneously achieve a sufficiently long working distance and a good lateral resolution, we employed a large-mode area photonic crystal fiber (PCF) and a coreless silica fiber (CSF) of the same diameters. A working distance of up to 1270 microm, a 3 dB distance range of 2210 microm, and a transverse resolution of 14.2 microm were achieved with the implemented PCF lensed fiber; these values are comparable to those obtainable with a conventional objective lens having an NA of 0.25 (10 x). The performance of the OCT system equipped with the proposed PCF lensed fiber is presented by showing the OCT images of a rat finger as a biological sample and a pearl as an in-depth sample.     

Electro-optic multimode interference device using organic materials

We present experimental results verifying the optical robustness of a 1 x 1 multimode interference (MMI) device that is directly butt coupled with optical fibers at 70 degrees C for 1050 h and discuss the gradual increase of polarization dependent loss. Based on this structure, an electro-optic (EO) MMI waveguide device that can control the output optical power by using an electrode structure located directly on top of the multimode is presented. As a proof of principle, we demonstrate the switching operation of the EO-MMI device using commercially available chromophore as the active EO material.     

多摄动因素对火星探测器地-火轨道设计的影响

主要围绕火星探测器在地球上空200 km处飞离地球开始一直到火星入轨点的转移轨道段轨道设计所做的轨道任务分析、摄动因素分析及近地轨道火星探测器姿态所受干扰力矩进行理论与仿真研究.一般情况下,火星探测器受到的摄动力与中心天体引力相比是很小的,但摄动力的长期累积作用不可忽视.轨道摄动研究已经成为轨道确定、观测预报、轨道改进...     

Electric field sensing system using coherence modulation of light

This paper describes an experimental setup for detecting electric fields using electrooptic lithium niobate (LiNbO/sub 3/) sensors and coherence modulation of light. In this detection scheme, the sensed electric fields modulate optical delays, which are introduced by LiNbO/sub 3/ coherence modulators when associated to low-coherence optical sources. The optical delays act as coherence-multiplexed carriers of the sensed electric fields and are transmitted through an optical fiber channel. At the receiver, the electric fields are detected by measuring the auto-correlation of the received light by using two-wave interferometers, which are matched to the introduced optical delays on the sensing devices.     

Modeling of scattering and depolarizing electro-optic devices. II. Device simulation

We describe a simple method for performing accurate computer simulation and modeling of arbitrary-geometry electro-optic (EO) devices. We use a material EO model that includes the effects of scattering and depolarization as well as the change in the index of refraction. Finite-element analysis is used to determine the electrostatic field distribution for EO device designs. Attenuation of the transmitted light intensity as a result of scattering is modeled as an exponential function, and the intensity of transmitted depolarized light is shown to be a function of the scattering intensity. The total optical transmittance is determined by integration of these values over all the elements in the path of the propagating light. Lanthanum-modified lead zirconate titanate-based surface-electrode and transverse-electrode EO devices are designed and fabricated. Their experimentally measured performance is found to be in excellent agreement with our computer-simulation results.     

Optical imaging applied to microelectronic chip-to-chip interconnections

An imaging system is proposed as an alternative to metallized connections between integrated circuits. Power requirements for metallized interconnects and electrooptic links are compared. A holographic optical element is considered as the imaging device. Several experimental systems have been constructed which have visible LEDs as the transmitters and PIN photodiodes as the receivers. Signals are evaluated at different source-detector separations. Multiple exposure holograms are used as a means of optical fan out allowing one source to simultaneously address several receiver locations. Limitations of this technique are also discussed.     

Simultaneous absolute measurements of principal angle and phase retardation with a new common-path heterodyne interferometer

This study demonstrates a new method for simultaneously measuring both the angle of the principal axis and the phase retardation of the linear birefringence in optical materials. We used a circular common-path interferometer (polariscope) as the basic structure modulated by an electro-optic (EO) modulator. An algorithm was developed to simultaneously measure the principal axis and the phase retardation of a lambda/4 or lambda/8 plate as a sample. In the case of a lambda/4 plate, the average absolute error of the principal axis is approximately 3.77 degrees, and that of the phase retardation is approximately 1.03 degrees (1.09%). The retardation error is within the 5% uncertainty range of a commercial wave plate. Fortunately, the nonlinear error caused by the reflection phase retardation of the beam splitter dose not appear in the new system. Therefore the error could be attributed to misalignment and defects in the EO modulator or the other optical components. As for the repeatability of this new common-path heterodyne interferometer, the average deviation for the principal axis is 0.186 degrees and the phase retardation is 0.356 degrees. For the stability, the average deviation for the principal axis is 0.405 degrees and the phase retardation is 0.635 degrees. The resolution of this new system is estimated to be approximately 0.5 degrees, and the principal axis and phase retardation could be measured up to pi and 2pi, respectively, without ambiguity.     

A model for incorporating the effects of nonzero switching-timeconstants in electrooptic masks used in Hadamard-transform spectrometry

Hadamard-transform (HT) spectrometers offer a multiplex advantage over conventional monochromators, making them very useful in situations in which the signal-to-noise ratio is low. HT spectrometers having no moving parts can be implemented by substituting an electrooptic mask for the moving mask in the optical path. However, the physical properties of an electrooptic mask introduce two types of nonidealities-static and dynamic-into the measurement system. These nonidealities can cause distortions in the acquired spectra if their effects are neglected in the signal-recovery process. We have developed two complete system models that incorporate the effects of both static and dynamic nonidealities. In addition, we have devised recovery schemes applicable for each system model and have designed computationally efficient implementations of the recovery schemes