The paper briefly presents an original method for design of inhomogeneous thin films which takes into consideration from the beginning the finite character of the optical thickness. At the beginning, the best solution is obtained in terms of the value of a complex function on a certain spectral grid. At the second step, the design is converted in terms of refractive index profile. Special care is taken to minimize the variations of this profile. Then, a program using this method, written as Windows application, is described together with a design example providing a spectral dependence of the reflectance having the shape of Romanian Athenaeum building.
{"title":"Interferential filter design with continuously variable refractive index","authors":"A. Trache, V. Lupei, M. Dinca","doi":"10.1117/12.312733","DOIUrl":"https://doi.org/10.1117/12.312733","url":null,"abstract":"The paper briefly presents an original method for design of inhomogeneous thin films which takes into consideration from the beginning the finite character of the optical thickness. At the beginning, the best solution is obtained in terms of the value of a complex function on a certain spectral grid. At the second step, the design is converted in terms of refractive index profile. Special care is taken to minimize the variations of this profile. Then, a program using this method, written as Windows application, is described together with a design example providing a spectral dependence of the reflectance having the shape of Romanian Athenaeum building.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121602536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigate theoretically a process of coherent Raman scattering in a medium where the coherence between two low- energetic levels is presented by adiabatic population transfer. In the present case the light induced moving optical grating can be formed by a periodical sequence of solitary-type waves (adiabatons). The parameters of this grating (propagation velocity, coefficients of spatial Fourier decomposition) are controlled completely by the amplitudes and phases of the two coupling fields at the medium entrance.
{"title":"Coherent Raman scattering on light-induced optical gratings prepared by adiabatic population transfer","authors":"N. Leinfellner, L. Windholz, I. Mazets","doi":"10.1117/12.312812","DOIUrl":"https://doi.org/10.1117/12.312812","url":null,"abstract":"We investigate theoretically a process of coherent Raman scattering in a medium where the coherence between two low- energetic levels is presented by adiabatic population transfer. In the present case the light induced moving optical grating can be formed by a periodical sequence of solitary-type waves (adiabatons). The parameters of this grating (propagation velocity, coefficients of spatial Fourier decomposition) are controlled completely by the amplitudes and phases of the two coupling fields at the medium entrance.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124970546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Ghica, N. Mincu, C. Stanciu, G. Dinescu, E. Aldea, V. Sandu, A. Andrei, M. Dinescu, A. Ferrari, M. Balucani, G. Lamedica
Amorphous and hydrogenated (a-SiC:H) as well as crystalline silicon carbide are widespread materials for optoelectronic applications. In this paper, we studied the effect of laser/RF plasma jet treatment of a-SiC:H thin films deposited by Plasma Enhanced Chemical Vapor Deposition, on Si wafers. A Nd:YAG laser ((lambda) equals 1.06 micrometers , tFWHM equals 14 ns, E0 equals 0.015 J/pulse) was used with a fluence of 4 mJ/cm2 incident on the sample, the number of pulses being varied. Plasma treatments were performed in a plasma jet generated by a capacity coupled RF discharge in N2. Different analysis techniques were used to investigate the films, before and after the irradiation: X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. We followed the modification of their structure and composition as an effect of the laser/plasma treatment. A comparison with the excimer and also with the RF treatments was performed.
{"title":"Laser treatment of a-SiC:H thin films for optoelectronic applications","authors":"D. Ghica, N. Mincu, C. Stanciu, G. Dinescu, E. Aldea, V. Sandu, A. Andrei, M. Dinescu, A. Ferrari, M. Balucani, G. Lamedica","doi":"10.1117/12.312672","DOIUrl":"https://doi.org/10.1117/12.312672","url":null,"abstract":"Amorphous and hydrogenated (a-SiC:H) as well as crystalline silicon carbide are widespread materials for optoelectronic applications. In this paper, we studied the effect of laser/RF plasma jet treatment of a-SiC:H thin films deposited by Plasma Enhanced Chemical Vapor Deposition, on Si wafers. A Nd:YAG laser ((lambda) equals 1.06 micrometers , tFWHM equals 14 ns, E0 equals 0.015 J/pulse) was used with a fluence of 4 mJ/cm2 incident on the sample, the number of pulses being varied. Plasma treatments were performed in a plasma jet generated by a capacity coupled RF discharge in N2. Different analysis techniques were used to investigate the films, before and after the irradiation: X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. We followed the modification of their structure and composition as an effect of the laser/plasma treatment. A comparison with the excimer and also with the RF treatments was performed.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"3405 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130359179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In fiber optic communications the technique of wavelength division multiplexing (WDM) constitutes a means of increasing the information capacity of fiber optics in communication systems and allows the optimal usage of the capacity of optic fiber. This paper presents the concepts of WDM and high density WDM from the point of view of developing a unitary theoretical analysis of necessary parameters for the design of optic integrated circuits with functions for optic signals multiplexing and demultiplexing, with planar diffraction gratings.
{"title":"Concept of WDM-HD: WDM for increasing the information capacity of fiber optic communication systems","authors":"P. Schiopu, L. Dragnea","doi":"10.1117/12.312687","DOIUrl":"https://doi.org/10.1117/12.312687","url":null,"abstract":"In fiber optic communications the technique of wavelength division multiplexing (WDM) constitutes a means of increasing the information capacity of fiber optics in communication systems and allows the optimal usage of the capacity of optic fiber. This paper presents the concepts of WDM and high density WDM from the point of view of developing a unitary theoretical analysis of necessary parameters for the design of optic integrated circuits with functions for optic signals multiplexing and demultiplexing, with planar diffraction gratings.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115069091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Mănăilă-Maximean, C. Roșu, R. Bena, Alexandru I. Albu, I. Popescu
We present the experimental results concerning hybrid optical bistable devices without resonant cavity using as electro-optic modulators a nematic liquid crystal cell and a polymer dispersed liquid crystal film. Bistable operation was studied for different control voltages and multistable behavior was studied for the polymer dispersed liquid crystal film as a function of the control voltage frequency.
{"title":"Optical bistability using nematic liquid crystals and polymer-dispersed liquid crystals","authors":"D. Mănăilă-Maximean, C. Roșu, R. Bena, Alexandru I. Albu, I. Popescu","doi":"10.1117/12.312695","DOIUrl":"https://doi.org/10.1117/12.312695","url":null,"abstract":"We present the experimental results concerning hybrid optical bistable devices without resonant cavity using as electro-optic modulators a nematic liquid crystal cell and a polymer dispersed liquid crystal film. Bistable operation was studied for different control voltages and multistable behavior was studied for the polymer dispersed liquid crystal film as a function of the control voltage frequency.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"136 42","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120850888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A digital powermeter was developed for measuring the power of laser beams using an electrically calibrated thermopile. This choice allows metrological quality measurements in a broad spectral range and an accurate calibration, but the electronic readout must meet some severe specifications concerning internal fluctuation (generally, most of commercially available radiometers, even advanced, do not). The reported powermeter has very low internal fluctuation (both drift and noise, in respect with its resolution). Original, yet simple circuitry was developed for low noise and for an accurate zero setting (even with a high background). The most important of these internal circuits is described. Statistical noise tests are also presented and some comparisons with advanced commercial powermeters. A large number of tests, each of them containing 500 - 900 measurements (values), revealed for the reported powermeter that `0' reading is the most probable noise value (i.e. the most often found), its probability being in all cases larger than 99% on the most sensitive range and equal to 100% on all other ranges.
{"title":"Digital laser powermeter","authors":"E. Smeu, N. Puscas, I. Popescu","doi":"10.1117/12.312715","DOIUrl":"https://doi.org/10.1117/12.312715","url":null,"abstract":"A digital powermeter was developed for measuring the power of laser beams using an electrically calibrated thermopile. This choice allows metrological quality measurements in a broad spectral range and an accurate calibration, but the electronic readout must meet some severe specifications concerning internal fluctuation (generally, most of commercially available radiometers, even advanced, do not). The reported powermeter has very low internal fluctuation (both drift and noise, in respect with its resolution). Original, yet simple circuitry was developed for low noise and for an accurate zero setting (even with a high background). The most important of these internal circuits is described. Statistical noise tests are also presented and some comparisons with advanced commercial powermeters. A large number of tests, each of them containing 500 - 900 measurements (values), revealed for the reported powermeter that `0' reading is the most probable noise value (i.e. the most often found), its probability being in all cases larger than 99% on the most sensitive range and equal to 100% on all other ranges.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129959447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Because the spatial beam structure is the most critical element of a laser, measurement of this beam structure is indispensable in laser design, development, and manufacture. Since measurement of the beam structure inside the cavity is impractical, if not impossible, the beam profile structure outside the laser provides the only real insight into cavity structure. It is critical that profile measurements outside the cavity be as precise and illuminating as possible. Electronic measurement of the output beam profile is the only method that gives sufficiently accurate and illuminating beam structure analysis.
{"title":"Electronic laser beam profile measurement","authors":"C. Roundy","doi":"10.1117/12.312661","DOIUrl":"https://doi.org/10.1117/12.312661","url":null,"abstract":"Because the spatial beam structure is the most critical element of a laser, measurement of this beam structure is indispensable in laser design, development, and manufacture. Since measurement of the beam structure inside the cavity is impractical, if not impossible, the beam profile structure outside the laser provides the only real insight into cavity structure. It is critical that profile measurements outside the cavity be as precise and illuminating as possible. Electronic measurement of the output beam profile is the only method that gives sufficiently accurate and illuminating beam structure analysis.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132090030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Windows 3.1 application is shown for editing, analyzing, optimizing, designing technologies and determining the optical constants out of the (R,T) measurements. A dynamic arborescent structure of data (optical coatings) has been used, allowing a great flexibility in describing the optical coatings. The optical coatings of the arborescent structure are defined on the same thin films (defined in root), the change of a layer being detected by all the optical coatings of the arborescent structure, containing that layer. The layers are seen by coatings by mean of some groups (structures) of layers and some scale factors, the groups being the elements that describe the coating. So, one can study an optical coating or parts of coating (e.g. optical monitoring) under different conditions.
{"title":"Software for optical coating design","authors":"Gheorghe Honciuc, G. Singurel","doi":"10.1117/12.312735","DOIUrl":"https://doi.org/10.1117/12.312735","url":null,"abstract":"A Windows 3.1 application is shown for editing, analyzing, optimizing, designing technologies and determining the optical constants out of the (R,T) measurements. A dynamic arborescent structure of data (optical coatings) has been used, allowing a great flexibility in describing the optical coatings. The optical coatings of the arborescent structure are defined on the same thin films (defined in root), the change of a layer being detected by all the optical coatings of the arborescent structure, containing that layer. The layers are seen by coatings by mean of some groups (structures) of layers and some scale factors, the groups being the elements that describe the coating. So, one can study an optical coating or parts of coating (e.g. optical monitoring) under different conditions.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130069874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An extensive comparison between two modeling methods: Method of Lines and Time Domain Method in analyzing the large signal responses of Fabry-Perot semiconductor lasers is presented. The methods are implemented in two numerical codes written in FORTRAN and using DIGITAL ALPHA workstations under VAX/VMS and UNIX operating systems. The comparison shows good agreement between the simulation results under specific conditions. A special accent is placed on the advantages and drawbacks of both methods by taking into account their numerical problems and the computational effort implied by simulations.
{"title":"Comparison between method of lines and time domain method in evaluating the large signal responses of Fabry-Perot semiconductor lasers","authors":"A. L. Braverman","doi":"10.1117/12.312725","DOIUrl":"https://doi.org/10.1117/12.312725","url":null,"abstract":"An extensive comparison between two modeling methods: Method of Lines and Time Domain Method in analyzing the large signal responses of Fabry-Perot semiconductor lasers is presented. The methods are implemented in two numerical codes written in FORTRAN and using DIGITAL ALPHA workstations under VAX/VMS and UNIX operating systems. The comparison shows good agreement between the simulation results under specific conditions. A special accent is placed on the advantages and drawbacks of both methods by taking into account their numerical problems and the computational effort implied by simulations.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128690102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper presents a numerical implementation of the Effective Index Method (EIM) for the determination of the propagation constants and field distributions in dielectric or semiconductor guiding structures that are uniform on the direction of propagation. The implementation proved to be applicable to a wide range of guiding structures (ridge, buried and diffused guides) and was tested against analytical solutions and against other methods' results proving good accuracy. The advantages and limitations of the EIM are discussed and a common waveguide problem result is presented as an example. From the practical applications of the method, the optical analysis of the ridge geometry and QW positioning of a 3W continuous wave GRIN SCH SQW laser diode in the 670 nm band is briefly discussed and the measured performances of the devices are presented.
{"title":"Effective index method for the computation of the propagation constant and electromagnetic field distribution in z-uniform dielectric or semiconductor waveguides","authors":"M. Dumitrescu, M. Guina","doi":"10.1117/12.312689","DOIUrl":"https://doi.org/10.1117/12.312689","url":null,"abstract":"The paper presents a numerical implementation of the Effective Index Method (EIM) for the determination of the propagation constants and field distributions in dielectric or semiconductor guiding structures that are uniform on the direction of propagation. The implementation proved to be applicable to a wide range of guiding structures (ridge, buried and diffused guides) and was tested against analytical solutions and against other methods' results proving good accuracy. The advantages and limitations of the EIM are discussed and a common waveguide problem result is presented as an example. From the practical applications of the method, the optical analysis of the ridge geometry and QW positioning of a 3W continuous wave GRIN SCH SQW laser diode in the 670 nm band is briefly discussed and the measured performances of the devices are presented.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133683360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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