Measurement Of Optical Pulses Research Articles

Harnessing disorder for photonic device applications

For photonic devices, structural disorder and light scattering have long been considered annoying and detrimental features that were best avoided or minimized. This review shows that disorder and complexity can be harnessed for photonic device applications. Compared to ordered systems, disordered systems provide much more possibilities and diverse optical responses. They have been used to create physical unclonable functions for secret key generation, and more recently for random projection, high-dimensional matrix multiplication, and reservoir computing. Incorporating structural disorder enables novel devices with unique functionalities as well as multi-functionality. A random system can function as an optical lens, a spectrometer, a polarimeter, and a radio frequency receiver. It is also employed for optical pulse measurement and full-field recovery. Multi-functional disordered photonic devices have been developed for hyperspectral imaging, spatial, and spectral polarimetry. In addition to passive devices, structural disorder has been incorporated to active devices. One prominent example is the random laser, which enables speckle-free imaging, super-resolution spectroscopy, broad tunability of high-power fiber laser, and suppression of lasing instabilities. Disordered devices have low fabrication costs, and their combination with advanced computational techniques may lead to a paradigm shift in photonics and optical engineering.

Multimode-fiber-based single-shot full-field measurement of optical pulses.

Multimode fibers are explored widely for optical communication, spectroscopy, imaging, and sensing applications. Here we demonstrate a single-shot full-field temporal measurement technique based on a multimode fiber. The complex spatiotemporal speckle field is created by a reference pulse propagating through the fiber, and it interferes with a signal pulse. From the time-integrated interference pattern, both the amplitude and the phase of the signal are retrieved. The simplicity and high sensitivity of our scheme illustrate the potential of multimode fibers as versatile and multi-functional sensors.

Technique for the measurement of picosecond optical pulses using a non-linear fiber loop mirror and an optical power meter.

A method for measuring picosecond pulse width by using only fiber components and optical power meters is presented. We have shown that the output power splitting ratio of a non-linear fiber loop mirror can be used to extract the full-width half maximum of the optical pulse, assuming a known slowly varying envelope shape and internal phase structure. Theoretical evaluation was carried out using both self-phase and cross-phase modulation approaches, with the latter showing a twofold sensitivity increase, as expected. In the experimental validation, pulses from an actively fiber mode-locked laser at the repetition rate of 10 GHz were incrementally temporally dispersed by using SMF-28 fiber, and then successfully measured over a pulse width range of 2-10 ps, with a resolution of 0.25 ps. This range can be easily extended from 0.25 to 40 ps by selecting different physical setup parameters.

Computer controlled multi‐shot frequency‐resolved optical gating diagnostic system for femtosecond optical pulse measurement

AbstractThe control and data acquisition of homemade, second harmonic generation (SHG) multi‐shot frequency‐resolved optical gating (FROG) diagnostic technique reported here. We have designed and developed the computer controlled multi‐shot FROG diagnostic system using reflecting optics to minimize the dispersion while LabVIEW software has employed to control and data acquisition. The femtosecond laser system at laboratory for intense lasers (L2I) optimized and characterized using LabVIEW‐based FROG system. We have measured and retrieved the oscillator and compressed amplified laser pulse profiles in temporal domains having full width half maximum (FWHM) of 150 and 270 fs, respectively, and relatively small temporal phase ∼1 radians peak to peak variations with FROG error ∼0.003. The grating detuning data acquired in the form of the single data file to observe the FROG trace pattern evaluation with the change of grating positions to confirm the reliability of the LabVIEW‐based FROG system.

무인차량용 3차원 영상처리를 위한 16-채널 CMOS 인버터 트랜스임피던스 증폭기 어레이

This paper presents a 16-channel transimpedance amplifier (TIA) array implemented in a standard CMOS technology for the applications of panoramic scan LADAR (PSL) systems. Since this array is the front-end circuits of the PSL systems to recover three dimensional image for unmanned vehicles, low-noise and high-gain characteristics are necessary. Thus, we propose a voltage-mode inverter TIA (I-TIA) array in this paper, of which measured results demonstrate that each channel of the array achieves transimpedance gain, 565-MHz bandwidth for 0.5-pF photodiode capacitance, 6.7-pA/sqrt(Hz) noise current spectral density, and 33.8-mW power dissipation from a single 1.8-V supply. The measured eye-diagrams of the array confirm wide and clear eye-openings up to 1.3-Gb/s operations. Also, the optical pulse measurements estimate that the proposed 16-channel TIA array chip can detect signals within 20 meters away from the laser source. The whole chip occupies the area of including I/O pads. For comparison, a current-mode 16-channel TIA array is also realized in the same CMOS technology, which exploits regulated-cascode (RGC) input configuration. Measurements reveal that the I-TIA array achieves superior performance in optical pulse measurements.

Spectral phase characterization of ultrashort pulse using fringe free interferometry

There are presented analytical and experimental results of a novel method which enables significant simplifications in spectral shearing interferometry as applied for ultrashort optical pulse measurements. The method attempts to improve the superiority in conventional Spectral Phase Interferometry for Direct Electric-field Reconstruction (SPIDER). It doesn’t split a test pulse into two parts, but compensates for the delay time between two quasi-monochromatic frequency components in a chirped pulse with spectral and temporal shear to produce an interferogram without fringe. Fringe free interferograms could simplify data processing procedures and reduce the restriction on resolution of spectrometers. The experimental setup avoids the influence of material dispersion with real-time and single-shot nature, and could be made up as a miniaturization measurement device. Although being short of the beauties in SPIDER, it still could be an optional femtosecond pulse measurement method in certain conditions.

Efficient scheme for realizing quantum dense coding with GHZ state in separated low-Q cavities

We propose an efficient scheme for realizing quantum dense coding with three-particle GHZ state in separated low-Q cavities. In this paper, the GHZ state is first prepared with three atoms trapped, respectively, in three spatial separated cavities. Meanwhile, with the assistance of a coherent optical pulse and X-quadrature homodyne measurement, we can implement quantum dense coding with three-particle GHZ state with a higher probability. Our scheme can also be generalized to realize N-particle quantum dense coding.

THE AMPLITUDE AND PHASE MEASUREMENTS OF FEMTOSECOND PULSE USING FRINGE FREE INTERFEROMETRY OF SPECTRAL HIGH-RESOLUTION METHOD

In this paper, we present analytical and experimental results of a novel method which enables significant simplifications in spectral shearing interferometry as applied for ultrashort optical pulse measurements. The method attempts to improve the superiority in conventional spectral phase interferometry for direct electric-field reconstruction (SPIDER). It does not split a test pulse into two parts, but compensate for the delay time between two quasi-monochromatic frequency components in a chirped pulse with spectral and temporal shear to produce an interferogram without fringe. Fringe free interferogram could simplify data processing procedure and reduce the restriction on resolution of spectrometer. The experimental setup avoids the influence of material dispersion with real-time and single-shot nature, and could be made up as a miniaturization measurement device. Although being short of the beauties in SPIDER, it still could be an optional femtosecond pulse measurement method in certain condition.

New CMOS-compatible platforms based on silicon nitride and Hydex for nonlinear optics

Nonlinear photonic chips have enabled the generation and processing of signals using only light, with performance far superior to that possible electronically - particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics, its high two-photon absorption at telecommunications wavelengths poses a fundamental limitation. We review recent progress in non-silicon CMOS-compatible platforms for nonlinear optics, with a focus on Si3N4 and Hydex. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. This review highlights their potential impact as well as the challenges to achieving practical solutions for many key applications.

Optimization of Photodiode Bandwidth Employing Peak Distortion Analysis

This paper addresses the systematic approach to optimize series inductance in the inductively peaked pin photodiode for high speed operation beyond 100 Gb/s. For this end, peak distortion analysis is introduced in addition to group delay dispersion technique. Through analytical analysis and comprehensive numerical simulations, inductance values are calculated to optimize vertical eye-opening and signal-to-noise ratio. For verification, an optical waveguide integrated pin photodiode with optimized inductance is fabricated and measured. Using the optical pulse measurement setup, its pulse response is measured, and a full-width at half maximum of 7.34 ps is obtained. The fabricated module is tested using 107 Gb/s return-to-zero signal and shows excellent eye-opening.

Effect of Deep N-Well Bias in an 850-nm Si Photodiode Fabricated Using the CMOS Process

In this letter, we present an 850-nm Si octagonal photodiode (PD) with deep n-well implantation formed using the CMOS process without process modifications. Two different bias schemes (normal bias and extra bias) on the deep n-well were used to analyze the effects of deep n-well bias on the bandwidth and gain-bandwidth performances of Si PDs. The avalanche gain, frequency response, and optical pulse measurements in this letter demonstrate that the extra bias on deep n-well improves the PD performance. To the best of our knowledge, this design achieves the highest bandwidth (8.7 GHz) and a large gain-bandwidth product of 542 GHz with a reverse bias of 11.45 V and an extra voltage of 11.45 V in standard CMOS technology.

Fourier fringe analysis and its application to metrology of extreme physical phenomena: a review [Invited

The paper reviews a technique for fringe analysis referred to as Fourier fringe analysis (FFA) or the Fourier transform method, with a particular focus on its application to metrology of extreme physical phenomena. Examples include the measurement of extremely small magnetic fields with subfluxon sensitivity by electron wave interferometry, subnanometer wavefront evaluation of projection optics for extreme UV lithography, the detection of sub-Ångstrom distortion of a crystal lattice, and the measurement of ultrashort optical pulses in the femotsecond to attosecond range, which show how the advantages of FFA are exploited in these cutting edge applications.

Motion Artifact Compensation for Wristwatch Type Photoplethysmography Sensor

Heart beat measurement is useful not just for medical use but also for daily healthcare monitoring and for sports. Photoplethysmography is an optical pulse measurement method that measures the variation of light absorption of the blood flow in capillary. Fingertip and earlobe, which are suitable places for this method, are not suitable for wearing sensors in daily life. Measurement at wrist will be more favorable. Technical difficulties of applying photoplethysmography measurement on wrist are: a) blood flow variation and change of sensor orientation caused by body motions, and b) low sensitivity compared to measurement at fingertips or earlobes because of the low capillary density in the tissue. We derived a transfer function that expresses the relationship between body acceleration and change in capillary blood flow based on a simple fluid dynamics model of artery and capillary. Preliminary experiments have shown that motion the artifacts can be reduced by subtracting the change of blood flow estimated from body acceleration. This method is different from conventional frequency filtering methods that do not consider the relationship between the body motion and the changes in the capillary blood flow. Furthermore, sensor head suspension mechanism has been employed in order to stabilize the sensor orientation with respect to the skin as well as the applied force on the skin.

Ultra-high speed photomultiplier tubes with nanosecond gating for fusion diagnostics

Fusion diagnostics can involve the measurement of ultra-fast optical pulses, often in close temporal proximity. We present a solution for the diagnostics of gamma reaction history and neutron time of flight by using microchannel plate based photomultiplier tubes (PMTs). The time response of the PMTs can be as fast as 100 ps FWHM and with a gain of up to 10(7). To observe small events in close temporal proximity to much larger signals such as the down-scattered fraction, the response of MCP-PMTs can be gated with an on∕off ratio of up to 10(13) in just 2 ns.

Unusual fault detection and loss analysis in optical fiber connections with refractive index matching material

We investigated and analyzed an unusual fault that occurs in optical access fiber networks, which is caused by a defective fiber connection. We developed a fault-detection system to locate such a fault by using both optical power level and optical pulse measurement methods. We investigated a defective mechanical splice in three laboratory tests: outward appearance, non-destructive, and dismantled. As a result, we confirmed that the defective mechanical splice had large gaps of more than 10μm. We also analyzed the unusual fault that occurs from such a defective mechanical splice in mechanically transferrable (MT) connector experiments. The experimental results revealed that the optical performance of fiber connections with a mixture of refractive index matching material and air-filled gaps was extremely unstable and varied widely. In the worst case, the insertion loss worsened to more than 30dB. The case of the fault caused by a mixture of refractive index matching material and air-filled gaps between the ends of optical fibers is thought to occur independently of the sorts or structures of optical fiber connectors and could be a characteristic peculiar to optical fiber connections using refractive index matching material. These findings can be applied to optical fiber connections that use refractive index matching material, such as MT connectors in outside underground facilities, mechanical splices, or field assembly connectors at aerial and home sites in optical access networks. These findings also support the practical construction and operation of optical network systems.

Toward On-Chip Phase-Sensitive Optical Temporal Waveform Measurements

This review summarizes the results obtained in 2011 toward the development of an "integrated optical oscilloscope," encompassing research on new technologies for the measurement of ultrafast optical pulses in both amplitude and phase through the use of integrated devices, some of which are compatible with electronic circuit technology (CMOS).

Accurate and automatic characterization of femtosecond optical pulses

We introduce a technique for the measurement of femtosecond optical pulses. This technique significantly reduces the uncertainty coming from the filter when used in the traditional technique, and an accurate spectral phase is retrieved. With the retrieved phase, the electric field, phase, waveform, as well as the duration of femtosecond optical pulses can be precisely reconstructed. The simulated autocorrelation traces deduced from the reconstructed pulsed electric field are in good agreement with the measured ones. This technique removes the manual procedure of selection and adjustment of the filter, an automatic measurement being realized.

复制脉冲对的时间延迟对光谱相位相干直接电场重建法测量飞秒脉冲的影响

复制脉冲对的时间延迟对光谱相位相干直接电场重建法测量飞秒脉冲的影响

A Novel Optical Instrument for Estimating Size Segregated Aerosol Mass Concentration in Real Time

A novel optical instrument has been developed that estimates size segregated aerosol mass concentration (i.e., PM 10 , PM 4 , PM 2.5 , and PM 1 ) over a wide concentration range (0.001–150 mg/m 3 ) in real time. This instrument combines photometric measurement of the particle cloud and optical sizing of single particles in a single optical system. The photometric signal is calibrated to approximate the PM 2.5 fraction of the particulate mass, the size range over which the photometric signal is most sensitive. The electrical pulse heights generated by light scattering from particles larger than 1 micron are calibrated to approximate the aerodynamic diameter of an aerosol of given physical properties, from which the aerosol mass distribution can be inferred. By combining the photometric and optical pulse measurements, this instrument can estimate aerosol mass concentrations higher than typical single particle counting instruments while providing size information and more accurate mass concentration information than traditional photometers. Experiments have shown that this instrument can be calibrated to measure aerosols with very different properties and yet achieve reasonable accuracy.

Synchronized Generation of Reconfigurable Microwave Sinusoidal Wave Packets From a Free-Running Pulsed Laser

Generation of customized microwave sinusoidal wave packets precisely synchronized with a free-running pulsed laser is required for many electrooptic modulation-based optical pulse processing and measurement applications. We propose and experimentally demonstrate a simple technique for this purpose. This technique is based on optical frequency-to-time conversion of a spectral interference in a fiber-optic two-arm interferometer with a wavelength-dithering feedback control. The same platform can be used to operate over a wide range of input repetition rates and can be optically reconfigured for tuning the frequency, amplitude, and phase of the generated microwave sinusoids.