Photorefractive Beam Fanning Optical Limiter

1997 ◽  
Vol 479 ◽  
Author(s):  
M. J. Miller ◽  
G. L. Wood ◽  
G. J. Salamo
Keyword(s):  
Response Time ◽  
Electric Fields ◽  
Optical Limiting ◽  
Major Obstacle ◽  
Speed Of Response ◽  
Optical Limiter

AbstractWe have investigated the potential for using photorefractive phenomena in optical limiting devices. The major obstacle preventing the photorefractive limiter from reaching this potential has been speed of response. In this paper we report on several techniques which are successful in enhancing the photorefractive beam fanning response time. In particular, we demonstrate and characterize the use of applied electric fields, gratings to seed the beam fan, and cylindrical focusing. We also report the first demonstration of a prototype beam fanning optical limiter encompassing many of the proposed improvements.

OPTICAL LIMITING STUDIES IN PHOTOREFRACTIVE PURE AND IRON-DOPED Bi12SiO20 CRYSTALS

2000 ◽  
Vol 09 (02) ◽  
pp. 217-225 ◽  
Author(s):  
P. SREERAMANA AITHAL ◽  
P. PREM KIRAN ◽  
D. NARAYANA RAO
Keyword(s):  
Excited State Absorption ◽  
Optical Limiting ◽  
Photon Absorption ◽  
Limiting Behavior ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Iron Incorporation ◽  
Optical Limiter ◽  
Level Model

Optical limiting characteristics of pure and 150 ppm Fe-doped Bi 12 SiO 20 (BSO:Fe) crystals are studied at high intensity nanosecond pulse regime. When the input light is at 532 nm and at 595 nm with 6 ns pulse duration, a good optical limiting behavior is observed due to simultaneous effect of trap assisted excited state absorption and two photon absorption. The precise role of the internal defects due to impurity centers present in the crystal lattice is explained on the basis of a four level model. This study reveal that the increased nonlinear absorption due to iron incorporation in BSO makes it an excellent passive optical limiter.

Optical Limiting in a Photorefractive Polymer

1997 ◽  
Vol 479 ◽  
Author(s):  
A. Grunnet-Jepsen ◽  
C. L. Thompson ◽  
W. E. Moerner
Keyword(s):  
Phase Conjugation ◽  
Optical Limiting ◽  
High Gain ◽  
Optical Beam ◽  
Device Application ◽  
Photorefractive Polymers ◽  
Optical Limiter ◽  
Photorefractive Polymer ◽  
Salient Features

AbstractOptical limiting has been suggested as a possible device application of high gain photorefractive (PR) polymers. The principle of operation relies on the existence of amplified scattering (beam fanning) to deplete the intensity of the incident coherent optical beam. The newest photorefractive polymers show a combination of high gain and reasonable speed, and we show how these materials behave as a beam fanning optical limiter and as a limiter based on self-pumped phase conjugation. A prototype cascaded beam fanning device is demonstrated and its salient features are discussed.

Enhancement of the Response time of a Reflective Type Sensor for Ozone Measurements

2014 ◽  
Vol 69 (8) ◽  
Author(s):  
Michael David ◽  
Tay Ching En Marcus ◽  
Maslina Yaacob ◽  
Mohd Rashidi Salim ◽  
Nabihah Hussin ◽  
...  
Keyword(s):  
Response Time ◽  
Path Length ◽  
Sensor Response ◽  
Sectional Area ◽  
Gas Cell ◽  
Cross Sectional ◽  
Simultaneous Reduction ◽  
Cylindrical Structure ◽  
Speed Of Response ◽  
Optical Reflectors

Sensor response time T (90) or speed of response is mathematically a function of the rate of diffusion of a gas sample in an absorption spectroscopic gas cell. Increasing the rate of diffusion increases the speed of response and vice versa. In this article, we present the design and analytical results on the response time of a reflective type ozone gas sensor. The variables of length and cross sectional area were interplayed to optimise the rate of diffusion. Two optical reflectors were employed in increasing the path length of the sensor; this resulted in the simultaneous reduction of the effective cell length and an increase in the diameter of the gas cell (cylindrical structure). Ozone diffusion in the 30 cm length of gas cell has been simulated to be 0.01713 ppm cm3/secs in comparison to 0.01023 ppm cm3/sec for a single reflector gas cell, which shows an enhancement of the sensor response time.

HIGH- AND LOW-MOLAR-MASS LIQUID CRYSTAL MIXTURES FOR PHOTOREFRACTIVE APPLICATIONS

1999 ◽  
Vol 08 (03) ◽  
pp. 329-340 ◽  
Author(s):  
HIROSHI ONO ◽  
NOBUHIRO KAWATSUKI
Keyword(s):  
Liquid Crystal ◽  
Response Time ◽  
Electric Fields ◽  
High Performance ◽  
Molar Mass ◽  
Gain Coefficient ◽  
Research Area ◽  
High Molar Mass ◽  
Bragg Regime ◽  
Photorefractive Material

We describe a highly efficient photorefractive material possessing high-molar-mass liquid crystal (H-LC), low-molar-mass liquid crystal (L-LC), and photoconductive agent. These photorefractive high- and low-molar-mass liquid crystal mixtures (HL-LCMs) show high-performance in a thick grating regime (Bragg regime) under low dc electric fields (< 1 V/μm). The photorefractive properties are strongly dependent on the concentration of the H-LC. The fastest response time of 70 ms is achieved with a gain coefficient of 213 cm-1 in the case of 10 wt% of the H-LC with 0.18 V/μm. The largest gain coefficient of over 600 cm-1 is achieved with the response time of 2.6 s in the case of 40 wt% of the H-LC with 0.7 V/μm. In addition, our future directions in this research area are also presented.

Nonlinear optical Properties of Pentaazadentate Expanded Porphyrins and Application in Optical Limiting

1997 ◽  
Vol 479 ◽  
Author(s):  
Duoyuan Wang ◽  
Wenfang Sun ◽  
Shiming Dong ◽  
Jinhai Si ◽  
Chunfei Li
Keyword(s):  
Optical Properties ◽  
Nonlinear Optical ◽  
Optical Limiting ◽  
Nonlinear Optical Properties ◽  
Saturable Absorption ◽  
Reverse Saturable Absorption ◽  
High Fluences ◽  
Expanded Porphyrins ◽  
Optical Limiter ◽  
Incident Laser Intensity

AbstractNonlinear optical properties of asymmetric pentaazadentate expanded porphyrin metal complexes are investigated. The transmittance dependence of the target compounds on the incident laser intensity generates different nonlinear optical effects in the excited states. The reverse saturable absorption at 532 nm in the ns pulses and the saturable absorption for the pspulses at high fluences are observed in solutions. The nonlinear refractive indices n2 aremeasured by the Z-scan technique. The optical limiting based on the RSA and transverse refraction are demonstrated for ns and continuous laser. An optical limiter based on the RSA and self-refraction is performed, in which the limitating threshold and amplitude of output energy are reduced.

THEORETICAL STUDIES ON LINEAR AND NONLINEAR OPTICAL CHARACTERIZATION AND OPTICAL LIMITING PROPERTY OF Pb(II), In(III) CHLORIDE, Ni(II) METALLATED 1,4,8,11,15,18,22,25-OCTAALKYLPHTHALOCYANINES

2007 ◽  
Vol 16 (02) ◽  
pp. 247-254 ◽  
Author(s):  
ASLI KARAKAS ◽  
AYHAN ELMALI
Keyword(s):  
Nonlinear Optical ◽  
Optical Limiting ◽  
Photon Absorption ◽  
Third Order ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Optical Limiter ◽  
Limiting Property ◽  
Insight Into ◽  
Good Agreement

To provide an insight into the optical limiting (OL) behavior of a series of 3 metallated 1,4,8,11,15,18,22,25-octaalkylphthalocyanines; the third-order nonlinear optical (NLO) properties, one-photon absorption (OPA) and two-photon absorption (TPA) characterizations have been theoretically investigated by means of AM1, ZINDO and configuration interaction (CI) methods. The highest values for the TPA cross-section (δ(ω)) are exhibited by derivatives metallated with indium and lead. It is also seen that the nickel-metallated compound might be a passive optical limiter of the series, indicating the weakest δ(ω) and second hyperpolarizability (γ). Our calculated results are in good agreement with the previous experimental observations on the examined molecules.

Modified carbon nanotubes as broadband optical limiting nanomaterials

2006 ◽  
Vol 21 (11) ◽  
pp. 2758-2766 ◽  
Author(s):  
Kok Chung Chin ◽  
Amarsinh Gohel ◽  
Hendry Izaac Elim ◽  
Weizhe Chen ◽  
Wei Ji ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Laser Pulses ◽  
Optical Limiting ◽  
Film Coating ◽  
Nanosecond Laser ◽  
Optical Limiters ◽  
Optical Limiter ◽  
Recent Developments ◽  
Device Applications ◽  
Modified Carbon Nanotubes

Carbon nanotubes have been shown to be effective broadband optical limiters for nanosecond laser pulses. In this paper, we review the recent developments of carbon nanotube-based optical limiters, in particular the effects of modifying carbon nanotubes for device applications. The techniques used to modify carbon nanotubes mainly include thin film coating, doping, and blending with optical absorbing dye. These modifications can greatly enhance the optical limiting performance of carbon nanotubes, with the goal of fabricating an optimal optical limiter system.

scholarly journals Assessment of UAV's Operator Cognitive State Based on Behavior Signals

2018 ◽  
Vol 36 (4) ◽  
pp. 715-721
Author(s):  
Songyun Xie ◽  
Yabing Li ◽  
Wei Wang ◽  
Ya Meng ◽  
Xinzhou Xie
Keyword(s):  
Response Time ◽  
Evaluation Method ◽  
Mental Workload ◽  
Time Lapse ◽  
Cognitive State ◽  
Speed Of Response ◽  
State Evaluation ◽  
Aerial Vehicle ◽  
Vigilance Test ◽  
The Relationship

For exploring the relationship between the mental or cognitive state and metric of vigilance test for unmanned aerial vehicle (UAV), a vigilance state evaluation method and sphere of application based on behavior signals is established. A classical vigilance test avoiding to crash is set. During the experiments, the subjective ratings as well as behavior signals (Response Time, Lapse) are recording. The dynamic changing of behavior signals is analyzed using statistical analysis. The results demonstrate that compared with continuous PVT test, the subject's mental workload in rest PVT test decreases dramatically. Compared other metrics, the speed of response time can reflect the dynamic changing of subject's mental state. The metric of Q-50 has a strong robustness for outlier of subject. Considering that the metrics have strong correlation with operator's cognitive state, they can effectively analyze the different workload.

OPTICAL LIMITING IN TeO2–ZnO GLASS FROM Z-SCAN TECHNIQUE

2011 ◽  
Vol 20 (03) ◽  
pp. 351-356 ◽  
Author(s):  
ROSE LEENA THOMAS ◽  
VASUJA ◽  
MISHA HARI ◽  
B. NITHYAJA ◽  
S. MATHEW ◽  
...  
Keyword(s):  
Optical Properties ◽  
Nonlinear Absorption ◽  
Optical Limiting ◽  
Nonlinear Material ◽  
Saturable Absorption ◽  
Reverse Saturable Absorption ◽  
Absorption Coefficients ◽  
Single Beam ◽  
Optical Limiter

TeO 2– ZnO glasses were prepared by conventional melting procedure, and their optical properties were determined. In the present work, we measured the optical non-linearity of the glass. The measurement was carried out using a single beam z-scan technique given by Sheike Bahe et al. We could observe that the material exhibits reverse saturable absorption, and the effective nonlinear absorption coefficients are numerically evaluated. This study is important in identifying the nonlinear material as a Reverse Saturable Absorption (RSA) based optical limiter.

Photorefractive Optical Limiters

1994 ◽  
Vol 374 ◽  
Author(s):  
Gregory J. Salamo ◽  
Galen C. Duree ◽  
Matthew Morin ◽  
Edward J. Sharp ◽  
Gary L. Wood ◽  
...  
Keyword(s):  
Electric Fields ◽  
Optical Density ◽  
Pulse Width ◽  
Optical Pulse ◽  
Laser Light ◽  
Photorefractive Crystal ◽  
Incident Laser ◽  
Optical Limiters ◽  
Optical Limiter

AbstractWe consider the application of photorefractive beam fanning as an optical limiter. Results indicate that by focusing the incident laser light into the photorefractive crystal and by applying electric fields that limiting is possible at the 10μJ range with an optical density or O. D. of 3. These results are independent of the incident optical pulse width.

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