Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/005
P. Gerard, A. Morand, P. Lemaître-Auger
When an integrated optical component is asymmetrically excited, a radiated field is generated. Most of the time, the energy carried by the radiated field is lost. However, with high-level integration structures, this field can couple back into another waveguide and then disturb the operating conditions of the whole component. An original waveguide geometry that rapidly removes this radiated field is thus proposed here. The study of a specific Y-junction shows that it is possible to reduce by a factor of at least 30 the length of the Y-junction's straight waveguide. Computer modelling was performed with the radiation spectrum method (RSM), a new beam propagation method, perfectly suited to dealing with the field coming from guided and radiation modes. It gives us a good physical understanding of the light propagation.
{"title":"A new solution to waveguide excitation suppressing the effects of the radiated field. Application to the Y-junction","authors":"P. Gerard, A. Morand, P. Lemaître-Auger","doi":"10.1088/0963-9659/7/4/005","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/005","url":null,"abstract":"When an integrated optical component is asymmetrically excited, a radiated field is generated. Most of the time, the energy carried by the radiated field is lost. However, with high-level integration structures, this field can couple back into another waveguide and then disturb the operating conditions of the whole component. An original waveguide geometry that rapidly removes this radiated field is thus proposed here. The study of a specific Y-junction shows that it is possible to reduce by a factor of at least 30 the length of the Y-junction's straight waveguide. Computer modelling was performed with the radiation spectrum method (RSM), a new beam propagation method, perfectly suited to dealing with the field coming from guided and radiation modes. It gives us a good physical understanding of the light propagation.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74493170","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/011
R. Reinisch, G. Vitrant
We show that in Cerenkov second harmonic generation the phase-matching condition is not automatically satisfied. The new concept of a Cerenkov phase-matching surface is introduced and the expression of the Cerenkov phase-matching condition is derived. We also show that the Cerenkov scheme includes second harmonic generation at distributed couplers. For example, use of grating couplers leads to grating-assisted Cerenkov second harmonic generation. These are important results which modify the understanding of the physics underlying Cerenkov frequency doubling.
{"title":"CERENKOV SECOND HARMONIC GENERATION REVISITED : EXISTENCE OF PHASE MATCHING","authors":"R. Reinisch, G. Vitrant","doi":"10.1088/0963-9659/7/4/011","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/011","url":null,"abstract":"We show that in Cerenkov second harmonic generation the phase-matching condition is not automatically satisfied. The new concept of a Cerenkov phase-matching surface is introduced and the expression of the Cerenkov phase-matching condition is derived. We also show that the Cerenkov scheme includes second harmonic generation at distributed couplers. For example, use of grating couplers leads to grating-assisted Cerenkov second harmonic generation. These are important results which modify the understanding of the physics underlying Cerenkov frequency doubling.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80258875","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/023
J. Thériault, L. Bissonnette, G. Roy
In this paper a method for the evaluation of cloud temperature and transmittance from ground-based measurements of the downwelling spectral radiance is proposed. The method uses the strong emission band of ozone at , which constitutes a natural source of IR radiation for probing clouds. Temperature and transmittance are derived from the cloudy-sky radiance measured in two narrow spectral channels: the first one is approximately at the centre of the ozone band at and the second one is off the band at . The cloud parameters are found by solving a system of equations requiring, as input, an estimate of the cloud height and thickness obtained from lidar returns, and of atmospheric temperature and humidity profiles. The validation tests performed on experimental spectra demonstrate the accuracy of the method with typical temperature errors smaller than 2 K for the spectral measurements coincident in time with the lidar measurements. Finally, the main sources of limitations to the method are identified and analysed.
{"title":"Remote monitoring of cloud parameters from ground-based FTIR measurements","authors":"J. Thériault, L. Bissonnette, G. Roy","doi":"10.1088/0963-9659/7/4/023","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/023","url":null,"abstract":"In this paper a method for the evaluation of cloud temperature and transmittance from ground-based measurements of the downwelling spectral radiance is proposed. The method uses the strong emission band of ozone at , which constitutes a natural source of IR radiation for probing clouds. Temperature and transmittance are derived from the cloudy-sky radiance measured in two narrow spectral channels: the first one is approximately at the centre of the ozone band at and the second one is off the band at . The cloud parameters are found by solving a system of equations requiring, as input, an estimate of the cloud height and thickness obtained from lidar returns, and of atmospheric temperature and humidity profiles. The validation tests performed on experimental spectra demonstrate the accuracy of the method with typical temperature errors smaller than 2 K for the spectral measurements coincident in time with the lidar measurements. Finally, the main sources of limitations to the method are identified and analysed.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77446616","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/009
I. Naydenova, T. Petrova, N. Tomova, V. Dragostinova, L. Nikolova, T. Todorov
Two types of high-efficiency amorphous methacrylic azobenzene polymer for reversible holographic storage are synthesized. It is shown that their efficiency is due to both photoinduced linear birefringence and surface relief. The contributions of these two effects on the diffraction efficiency of the holographic gratings are separated using the methods of polarization holography and it is found that they are strongly influenced by the differences in the chemical structure of the polymers. It is shown that higher relief corresponds to stronger coupling between the azobenzene side chains and the main chains of the polymer molecules.
{"title":"Polarization holographic gratings with surface relief in amorphous azobenzene containing methacrylic copolymers","authors":"I. Naydenova, T. Petrova, N. Tomova, V. Dragostinova, L. Nikolova, T. Todorov","doi":"10.1088/0963-9659/7/4/009","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/009","url":null,"abstract":"Two types of high-efficiency amorphous methacrylic azobenzene polymer for reversible holographic storage are synthesized. It is shown that their efficiency is due to both photoinduced linear birefringence and surface relief. The contributions of these two effects on the diffraction efficiency of the holographic gratings are separated using the methods of polarization holography and it is found that they are strongly influenced by the differences in the chemical structure of the polymers. It is shown that higher relief corresponds to stronger coupling between the azobenzene side chains and the main chains of the polymer molecules.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75204561","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/013
V. Torchigin, A. Torchigin
Ultrasonic light interaction in a slightly modified Bragg cell in the form of a truncated pyramid is considered theoretically. It is shown that the duration of the interaction can be increased by a factor of . The ultrasonic wave not only modulates the light wave in space but can also significantly increase its frequency and energy. Properties of moving optical resonators formed by the ultrasonic wave in the cell in relation to its taper and the intensity of the ultrasonic wave, optimal regimes of the interaction, maximally possible frequency shift, physical mechanisms responsible for the frequency shift, and possible generalization of the cell are considered.
{"title":"Enlarged shift of light frequency in a modified Bragg cell","authors":"V. Torchigin, A. Torchigin","doi":"10.1088/0963-9659/7/4/013","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/013","url":null,"abstract":"Ultrasonic light interaction in a slightly modified Bragg cell in the form of a truncated pyramid is considered theoretically. It is shown that the duration of the interaction can be increased by a factor of . The ultrasonic wave not only modulates the light wave in space but can also significantly increase its frequency and energy. Properties of moving optical resonators formed by the ultrasonic wave in the cell in relation to its taper and the intensity of the ultrasonic wave, optimal regimes of the interaction, maximally possible frequency shift, physical mechanisms responsible for the frequency shift, and possible generalization of the cell are considered.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85527639","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/014
Q. Zou
We present our theoretical investigations into the formalism of the transient effects during photorefractive two-wave mixing. An analytical model has been developed based on Kukhtarev's band-transport equations and on the linearization approximation. The physical phenomena involved during transients have been predicted for both drift and diffusion mechanisms. Good agreement is found when our model is compared with previous works, especially with the experimental measurements performed with BSO crystals by Heaton and Solymar.
{"title":"Theoretical model for the temporal dynamics in photorefractive two-wave mixing","authors":"Q. Zou","doi":"10.1088/0963-9659/7/4/014","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/014","url":null,"abstract":"We present our theoretical investigations into the formalism of the transient effects during photorefractive two-wave mixing. An analytical model has been developed based on Kukhtarev's band-transport equations and on the linearization approximation. The physical phenomena involved during transients have been predicted for both drift and diffusion mechanisms. Good agreement is found when our model is compared with previous works, especially with the experimental measurements performed with BSO crystals by Heaton and Solymar.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73238742","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/012
K. Siebert, E. Frins, W. Dultz
A Michelson interferometer is presented which enables a direct measurement of Berry's geometric phase (spin-redirection phase) resulting from light propagating through a helically wound optical single-mode fibre. The operation of the interferometer is interpreted in terms of Pancharatnam's theorem. In addition, we put the spin-redirection phase into the context of Pancharatnam's phase.
{"title":"Measurement of the spin-redirection phase using Pancharatnam's theorem","authors":"K. Siebert, E. Frins, W. Dultz","doi":"10.1088/0963-9659/7/4/012","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/012","url":null,"abstract":"A Michelson interferometer is presented which enables a direct measurement of Berry's geometric phase (spin-redirection phase) resulting from light propagating through a helically wound optical single-mode fibre. The operation of the interferometer is interpreted in terms of Pancharatnam's theorem. In addition, we put the spin-redirection phase into the context of Pancharatnam's phase.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72870782","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/002
D. Carroll, X. Zheng
The standard Green function method is used to model the spatial and angular distributions of THG scattering by micro-droplets. These distributions are found to depend critically on the size of the droplets. However, the THG peaks around and are of comparable magnitudes and stable. These results are compared with experimental observations and the prediction of the surface charge model.
{"title":"Modelling third harmonic generation from micro-droplets","authors":"D. Carroll, X. Zheng","doi":"10.1088/0963-9659/7/4/002","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/002","url":null,"abstract":"The standard Green function method is used to model the spatial and angular distributions of THG scattering by micro-droplets. These distributions are found to depend critically on the size of the droplets. However, the THG peaks around and are of comparable magnitudes and stable. These results are compared with experimental observations and the prediction of the surface charge model.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77456768","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/007
O. Lubin, O. Heuzé
Stress-induced birefringence arising from vacuum loading in the spatial filter lenses of high-energy laser systems is responsible for laser beam depolarization which may decrease the frequency conversion efficiency significantly. In order to predict these effects, we have carried out coupled mechanical-optical calculations. At first, we validated our predictions with experimental results. Then a parametric study allowed us to explain the influence of the geometrical characteristics of the lenses. Our main result is that symmetric lenses lead to minimum birefringence.
{"title":"MODELLING OF STRESS-INDUCED BIREFRINGENCE IN VACUUM BARRIER LENSES","authors":"O. Lubin, O. Heuzé","doi":"10.1088/0963-9659/7/4/007","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/007","url":null,"abstract":"Stress-induced birefringence arising from vacuum loading in the spatial filter lenses of high-energy laser systems is responsible for laser beam depolarization which may decrease the frequency conversion efficiency significantly. In order to predict these effects, we have carried out coupled mechanical-optical calculations. At first, we validated our predictions with experimental results. Then a parametric study allowed us to explain the influence of the geometrical characteristics of the lenses. Our main result is that symmetric lenses lead to minimum birefringence.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77968672","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}
Pub Date : 1998-07-01DOI: 10.1088/0963-9659/7/4/022
J. P. Lenney, W. Hirst, M. Padgett, B. Patterson, N. K. Hedges, D. Strachan, W. Sibbett
New legislation requiring the monitoring and reduction of polluting gases in both Europe and the USA has increased the demand for reliable and affordable open-path monitoring systems, suitable for hazardous area operation. We report on the research and development of a UV Fourier-transform spectrometer-based system for open-path monitoring of both hazardous and environmental gases. The device has no moving parts and is designed for unattended operation. Laboratory tests have successfully detected the presence of and differentiated between and present in a 1 m test cell down to 1.0 ppm.m levels. The real-time response of the system allows for the use of maximum entropy modelling to predict the size and location of a gas leak. Initial field tests with open-air gas releases of and have verified this. The multiple-gas feature of the instrument allows for additional possible applications with regards to environmental monitoring.
{"title":"Open-path UV Fourier-transform gas monitor with no moving parts","authors":"J. P. Lenney, W. Hirst, M. Padgett, B. Patterson, N. K. Hedges, D. Strachan, W. Sibbett","doi":"10.1088/0963-9659/7/4/022","DOIUrl":"https://doi.org/10.1088/0963-9659/7/4/022","url":null,"abstract":"New legislation requiring the monitoring and reduction of polluting gases in both Europe and the USA has increased the demand for reliable and affordable open-path monitoring systems, suitable for hazardous area operation. We report on the research and development of a UV Fourier-transform spectrometer-based system for open-path monitoring of both hazardous and environmental gases. The device has no moving parts and is designed for unattended operation. Laboratory tests have successfully detected the presence of and differentiated between and present in a 1 m test cell down to 1.0 ppm.m levels. The real-time response of the system allows for the use of maximum entropy modelling to predict the size and location of a gas leak. Initial field tests with open-air gas releases of and have verified this. The multiple-gas feature of the instrument allows for additional possible applications with regards to environmental monitoring.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87928782","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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