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71	Estudo comparativo entre a ceratectomia fotorrefrativa (PRK) e a ceratectomia subepitelial borboleta assistida a laser (LASEK borboleta) / Comparative study between photorefractive keratectomy (PRK) and butterfly laser-assisted subepithelial keratectomy (BLASEK) Ghanem, Vinicius Coral 29 August 2007 (has links) OBJETIVO: Avaliar comparativamente os resultados de duas técnicas de cirurgia refrativa de superfície com excimer laser, ceratectomia fotorrefrativa (PRK) e ceratectomia subepitelial borboleta assistida à laser (LASEKb). LOCAL: Hospital de Olhos Sadalla Amin Ghanem, Joinville, Santa Catarina, Brasil. MÉTODOS: Realizou-se um estudo prospectivo, randomizado e duplo-cego envolvendo 102 olhos de 51 pacientes. Cada paciente teve aleatoriamente um dos olhos operado com a técnica do PRK e o outro com LASEKb. Os pacientes foram acompanhados por 1 ano. RESULTADOS: Não houveram diferenças significativas entre os dois grupos na acuidade visual (AV) para longe, sem correção, (P = 0,5593). No 12o mês pós-operatório (PO), 98,04% dos olhos no grupo do PRK e 96,08% no grupo do LASEKb atingiram AV sem correção de 20/20. A previsibilidade, eficácia, segurança e estabilidade não apresentaram diferença estatisticamente significativa entre os grupos. O índice de segurança foi de 1 no PRK e 0,996 no LASEKb. Um olho do grupo do LASEKb perdeu uma linha de visão. A porcentagem de olhos que apresentou EE aos 12 meses na faixa de ±0,50 D foi de 94,1% no grupo do PRK e de 86,3% no grupo do LASEKb (P = 0,1883). Enquanto que na faixa de ±1,0 D foi de 100% no grupo do PRK e 98% no grupo do LASEKb (P = 0,3125). Não houve necessidade de reoperações. O tempo médio de cirurgia na técnica PRK foi de 304,86 + 58,77 segundos (aproximadamente 5 minutos) e na técnica LASEKb de 608,35 + 76,88 segundos (aproximadamente 10 minutos) (P < 0,001). O tempo médio de reepitelização no grupo do PRK foi de 4,35 ± 0,48 dias (variação, 4 a 5 dias) e no grupo do BLASEK foi de 4,75 ± 0,72 dias (variação, 4 a 6 dias) (P < 0,002). Os níveis de dor e o desconforto ocular PO não foram estatisticamente diferentes entre os grupos, entretanto houve uma tendência para menor dor no PRK (3,31 ± 4,09 vs 4,43 ± 4,27; P = 0,18). Houve uma redução estatisticamente significativa nos valores do teste de Schirmer em todas as avaliação PO, tanto no PRK (23,6 ± 8,1 vs 19,4 ± 10,1; P < 0,002) quanto no LASEKb (22,4 ± 8,7 vs 18,9 ± 9,7; P = 0,01), entretanto não houve diferença entre os grupos. A opacificação corneana (OC) PO foi pequena nos dois grupos. Somente no 1o mês foi observado diferença estatística entre os grupos, com maior intensidade da OC no grupo do LASEKb (0,18 ± 0,3881) quando comparado ao PRK (0,08 ± 0,2109) (P = 0,039936). A maior intensidade foi observada no 3o mês, com redução gradativa até o 12o mês. CONCLUSÃO: Dentro das condições deste estudo, conclui-se que o PRK e o LASEKb mostraram resultados semelhantes, exceto que o PRK apresentou menor tempo cirúrgico, reepitelização corneana mais rápida e menor OC no 30o PO. / PURPOSE: Comparatively evaluate the results of two techniques of surface excimer laser refractive surgery, photorefractive keratectomy (PRK) and butterfly laser-assisted subepithelial keratectomy (BLASEK). SETTING: Sadalla Amin Ghanem Eye Hospital, Joinville, Santa Catarina, Brazil. METHODS: This is a prospective, randomized and double-masked study including 102 eyes from 51 patients. Each patient was randomized to have one eye operated on with PRK and the other with BLASEK. Patients were followed for 1 year. RESULTS: There were no significant differences between the groups regarding uncorrected distant visual acuity (VA) (p= 0.5593). On the 12th post-operative (PO) month, 98.04% of the eyes in the PRK group and 96.08% in the BLASEK group reached uncorrected VA of 20/20. The predictability, efficacy, safety and stability did not present statically significant difference between groups. The safety index was of 1 for PRK and 0.996 for BLASEK. One eye of the BLASEK group lost one line on the 12th PO month. The percentage of the eyes that presented spherical equivalent at 12 months in the range of ±0.50 D was 94.1% in the PRK group and 86.3% in the BLASEK group (p = 0.1883). While in the range of ±1.0 D it was 100% in the PRK group and 98% in the BLASEK group (p = 0.3125). There were no retreatments. The mean surgical time was 304.86 + 58.77 seconds (approximately 5 minutes) in PRK and 608.35 + 76.88 seconds in BLASEK (approximately 10 minutes) (P < 0,001). The mean reepithelization time in the PRK group was 4.35 ± 0.48 days (range, 4 to 5 days), and in the BLASEK group was 4.75 ± 0.72 days (range, 4 to 6 days) (P < 0.002). Pain scores and ocular discomfort were not statistically different between groups, although there was a trend towards a lower pain level with PRK (3.31 ± 4.09 vs. 4.43 ± 4.27; P = 0.18). Schirmer test values were significantly reduced from preoperative levels through 12 months with both PRK (23.6 ± 8.1 vs. 19.4 ± 10.1; P < 0.002) and BLASEK (22.4 ± 8.7 vs. 18.9 ± 9.7; P = 0.01), however there was no difference between groups in any time point. Haze incidence was slight in both groups. Only in the 1st PO month statistical difference between the groups was observed, with higher intensity in the BLASEK group (0.18 ± 0.3881) when compared to the PRK (0.08 ± 0.2109) (p = 0.039936). The highest intensity was observed on the 3rd month, with gradual reduction until the 12th month. CONCLUSION: In the conditions of this study, it can be concluded that PRK and BLASEK showed similar results, except that PRK presented shorter surgical time, faster corneal reepithelization and less haze at 30th PO days. Astigmatism Astigmatismo Double-blind method Estudos prospectivos Laser assisted subepithelial keratectomy Método duplo-cego Miopia Myopia Prospective studies
72	Avaliação multidimensional da dor no pós-operatório da ceratectomia fotorrefrativa e fatores preditivos de dor / Improved multidimensional pain evaluation and predictors of early postoperative pain after photorefractive keratectomy Garcia, Renato 11 November 2016 (has links) OBJETIVOS: Validar o uso de questionários multidimensionais, como o Inventário Resumido da Dor (BPI) e o Questionário de Dor de McGill (MPQ) no pós-operatório da ceratectomia fotorefrativa (PRK). Comparar o perfil da dor no pós-operatório da PRK entre os dois olhos operados sob as mesmas condições e verificar preditores de dor como sexo, estado de ansiedade, conhecimento prévio da cirurgia e equivalente esférico do erro refrativo (EEER). MÉTODOS: Oitenta e seis olhos de 43 pacientes submeteram-se à PRK com intervalo de 14 dias entre cada olho. Uma hora antes da cirurgia, os pacientes responderam ao Inventário de Estado de Ansiedade (IDEA). No pós-operatório os pacientes receberam tratamento usual para dor e responderam aos questionários Escala Visual Analógica (EVA), BPI e MPQ após uma, 24, 48, 72 e 96 horas. Estudaram-se a consistência interna e as correlações de cada questionário. Compararam-se as pontuações de dor e a ansiedade entre primeiros e segundos olhos operados usando o teste de Wald, pareados através do teste t de Student. Utilizou-se o teste de Wald para comparar o comportamento da dor de acordo com sexo e EEER. RESULTADOS: Os questionários MPQ e BPI demonstraram alta consistência interna. Os questionários apresentaram pontuações mais elevadas na primeira mensuração da EVA (4.93 ± 2.38), MPQ - Índice de Estimativa de Dor (PRI) (26.95 ± 10.58), BPI - Índice de Intensidade de Dor (IID) (14.53 ± 7.36) e o BPI - índice de Interferência Funcional de Dor (IIFD) (22.30 ± 15.13), reduzindo-se gradativamente a cada momento subseqüente de avaliação. O MPQ-PRI na subescala subjetiva, apresentou curva de dor com redução lentificada. Todas as escalas apresentaram redução média estatisticamente significativa de um momento para o outro (p < 0.05) no pósoperatório, exceto no MPQ-PRI Subjetivo. Observaram-se correlações positivas entre as subescalas BPI e MPQ com a EVA (p < 0.05). Não houve diferença estatisticamente significativa nas pontuações de dor da EVA, BPI e MPQ-PRI entre ambos os olhos para todos os momentos avaliados. Os pacientes estavam menos ansiosos antes da PRK do segundo olho (p < 0.001), mas isto não apresentou correlação com níveis de dor após a cirurgia. O sexo e o conhecimento prévio do procedimento cirúrgico não influenciou significativamente em qualquer das escalas de dor. O EEER entre -3D to -5D correlacionou-se (p=0.035) com o BPI. CONCLUSÃO: O BPI e o MPQ apresentaram boas propriedades psicométricas em relação a confiabilidade e validade. Questionários multidimensionais fornecem uma avaliação mais abrangente sobre o perfil de dor após a PRK, se comparados à EVA, principalmente nos aspectos afetivos e cognitivos. O perfil da dor pósoperatória da PRK apresentou-se similar em ambos os olhos sob as mesmas condições. O EEER entre -3D to -5D foi o único fator preditor deste estudo para elevado nível de dor pós-operatória / PURPOSE: to validate the use of multidimensional questionnaires, such as the Brief Pain Inventory (BPI) and the McGill Pain Questionnaire (MPQ) in the postoperative photorefractive keratectomy (PRK). To compare the profiles of postoperative PRK pain between both eyes operated under the same conditions and to verify the preoperative predictors of pain such as gender, anxiety, knowledge of the procedure, and spherical equivalent refractive error (SERE). METHODS: eighty-six eyes of 43 patients with myopia underwent PRK in both eyes at an interval of 14 days between the procedures. One hour before surgery, subjects answered the State Anxiety Inventory (SAI). After surgery, usual PRK pain treatment was given and subjects answered to the Visual Analogue Scale (VAS), BPI and MPQ pain questionnaires at one, 24, 48, 72 and 96 hours intervals. The internal consistency was evaluated and convergent validity of each questionnaire was assessed using correlation testing. Pain scores and anxiety were compared between each eye using the Wald test and paired Student t test. Wald test was also used to test gender and SERE for each eye separately. RESULTS: both BPI and MPQ questionnaires showed internal consistency higher than 0.70. Subjects reported higher postoperative pain scores at the first measurement of the VAS (4.93 ± 2.38), MPQ - Pain Rating Index (26.95 6 10.58), BPI - Pain Severity Index (14.53 ± 7.36), and BPI- Pain Interference Index (22.30 ± 15.13) with decreasing scores at each subsequent observation period in all scales. All scales showed statistically significant (p < 0.05) pain reduction from one measurement to the next postoperatively, except the MPQ-PRI Evaluative. The majority of the scales and subscales showed a statistically significant (p < 0.05) direct correlation with the VAS at all of the evaluation periods. There were no statistically significant differences between the two eyes at all examination intervals regarding the VAS, BPI, and MPQ scores. Subjects were less anxious on average before the second surgery compared to the first surgery (p < 0.001), but this finding was not related to pain ratings after surgery. Gender and knowledge of the procedure did not significantly interfere with any scale of pain. The SERE between -3 D (diopters) and -5 D (p=0.035) revealed interference on the BPI. CONCLUSION: the BPI and the MPQ showed good psychometric properties regarding reliability and validity. The multidimensional questionnaires expanded the assessment of the PRK postoperative pain profile, compared to VAS, mainly in cognitive and affective aspects. The profiles of postoperative pain after PRK were similar between both eyes under the same conditions. In this study, a high SERE was the only predictor for increased pain after PRK Ceratectomia fotorrefrativa Cirurgia da córnea a laser Cornea Córnea Corneal surgery laser Dor Inquéritos e questionários Medição da dor/métodos Pain measurement/methods Pain Período pós-operatório Photorefractive keratectomy Postoperative period Surveys and questionnaires
73	Avaliação multidimensional da dor no pós-operatório da ceratectomia fotorrefrativa e fatores preditivos de dor / Improved multidimensional pain evaluation and predictors of early postoperative pain after photorefractive keratectomy Renato Garcia 11 November 2016 (has links) OBJETIVOS: Validar o uso de questionários multidimensionais, como o Inventário Resumido da Dor (BPI) e o Questionário de Dor de McGill (MPQ) no pós-operatório da ceratectomia fotorefrativa (PRK). Comparar o perfil da dor no pós-operatório da PRK entre os dois olhos operados sob as mesmas condições e verificar preditores de dor como sexo, estado de ansiedade, conhecimento prévio da cirurgia e equivalente esférico do erro refrativo (EEER). MÉTODOS: Oitenta e seis olhos de 43 pacientes submeteram-se à PRK com intervalo de 14 dias entre cada olho. Uma hora antes da cirurgia, os pacientes responderam ao Inventário de Estado de Ansiedade (IDEA). No pós-operatório os pacientes receberam tratamento usual para dor e responderam aos questionários Escala Visual Analógica (EVA), BPI e MPQ após uma, 24, 48, 72 e 96 horas. Estudaram-se a consistência interna e as correlações de cada questionário. Compararam-se as pontuações de dor e a ansiedade entre primeiros e segundos olhos operados usando o teste de Wald, pareados através do teste t de Student. Utilizou-se o teste de Wald para comparar o comportamento da dor de acordo com sexo e EEER. RESULTADOS: Os questionários MPQ e BPI demonstraram alta consistência interna. Os questionários apresentaram pontuações mais elevadas na primeira mensuração da EVA (4.93 ± 2.38), MPQ - Índice de Estimativa de Dor (PRI) (26.95 ± 10.58), BPI - Índice de Intensidade de Dor (IID) (14.53 ± 7.36) e o BPI - índice de Interferência Funcional de Dor (IIFD) (22.30 ± 15.13), reduzindo-se gradativamente a cada momento subseqüente de avaliação. O MPQ-PRI na subescala subjetiva, apresentou curva de dor com redução lentificada. Todas as escalas apresentaram redução média estatisticamente significativa de um momento para o outro (p < 0.05) no pósoperatório, exceto no MPQ-PRI Subjetivo. Observaram-se correlações positivas entre as subescalas BPI e MPQ com a EVA (p < 0.05). Não houve diferença estatisticamente significativa nas pontuações de dor da EVA, BPI e MPQ-PRI entre ambos os olhos para todos os momentos avaliados. Os pacientes estavam menos ansiosos antes da PRK do segundo olho (p < 0.001), mas isto não apresentou correlação com níveis de dor após a cirurgia. O sexo e o conhecimento prévio do procedimento cirúrgico não influenciou significativamente em qualquer das escalas de dor. O EEER entre -3D to -5D correlacionou-se (p=0.035) com o BPI. CONCLUSÃO: O BPI e o MPQ apresentaram boas propriedades psicométricas em relação a confiabilidade e validade. Questionários multidimensionais fornecem uma avaliação mais abrangente sobre o perfil de dor após a PRK, se comparados à EVA, principalmente nos aspectos afetivos e cognitivos. O perfil da dor pósoperatória da PRK apresentou-se similar em ambos os olhos sob as mesmas condições. O EEER entre -3D to -5D foi o único fator preditor deste estudo para elevado nível de dor pós-operatória / PURPOSE: to validate the use of multidimensional questionnaires, such as the Brief Pain Inventory (BPI) and the McGill Pain Questionnaire (MPQ) in the postoperative photorefractive keratectomy (PRK). To compare the profiles of postoperative PRK pain between both eyes operated under the same conditions and to verify the preoperative predictors of pain such as gender, anxiety, knowledge of the procedure, and spherical equivalent refractive error (SERE). METHODS: eighty-six eyes of 43 patients with myopia underwent PRK in both eyes at an interval of 14 days between the procedures. One hour before surgery, subjects answered the State Anxiety Inventory (SAI). After surgery, usual PRK pain treatment was given and subjects answered to the Visual Analogue Scale (VAS), BPI and MPQ pain questionnaires at one, 24, 48, 72 and 96 hours intervals. The internal consistency was evaluated and convergent validity of each questionnaire was assessed using correlation testing. Pain scores and anxiety were compared between each eye using the Wald test and paired Student t test. Wald test was also used to test gender and SERE for each eye separately. RESULTS: both BPI and MPQ questionnaires showed internal consistency higher than 0.70. Subjects reported higher postoperative pain scores at the first measurement of the VAS (4.93 ± 2.38), MPQ - Pain Rating Index (26.95 6 10.58), BPI - Pain Severity Index (14.53 ± 7.36), and BPI- Pain Interference Index (22.30 ± 15.13) with decreasing scores at each subsequent observation period in all scales. All scales showed statistically significant (p < 0.05) pain reduction from one measurement to the next postoperatively, except the MPQ-PRI Evaluative. The majority of the scales and subscales showed a statistically significant (p < 0.05) direct correlation with the VAS at all of the evaluation periods. There were no statistically significant differences between the two eyes at all examination intervals regarding the VAS, BPI, and MPQ scores. Subjects were less anxious on average before the second surgery compared to the first surgery (p < 0.001), but this finding was not related to pain ratings after surgery. Gender and knowledge of the procedure did not significantly interfere with any scale of pain. The SERE between -3 D (diopters) and -5 D (p=0.035) revealed interference on the BPI. CONCLUSION: the BPI and the MPQ showed good psychometric properties regarding reliability and validity. The multidimensional questionnaires expanded the assessment of the PRK postoperative pain profile, compared to VAS, mainly in cognitive and affective aspects. The profiles of postoperative pain after PRK were similar between both eyes under the same conditions. In this study, a high SERE was the only predictor for increased pain after PRK Ceratectomia fotorrefrativa Cirurgia da córnea a laser Córnea Dor Inquéritos e questionários Medição da dor/métodos Período pós-operatório Cornea Corneal surgery laser Pain measurement/methods Pain Photorefractive keratectomy Postoperative period Surveys and questionnaires
74	Estudo comparativo entre a ceratectomia fotorrefrativa (PRK) e a ceratectomia subepitelial borboleta assistida a laser (LASEK borboleta) / Comparative study between photorefractive keratectomy (PRK) and butterfly laser-assisted subepithelial keratectomy (BLASEK) Vinicius Coral Ghanem 29 August 2007 (has links) OBJETIVO: Avaliar comparativamente os resultados de duas técnicas de cirurgia refrativa de superfície com excimer laser, ceratectomia fotorrefrativa (PRK) e ceratectomia subepitelial borboleta assistida à laser (LASEKb). LOCAL: Hospital de Olhos Sadalla Amin Ghanem, Joinville, Santa Catarina, Brasil. MÉTODOS: Realizou-se um estudo prospectivo, randomizado e duplo-cego envolvendo 102 olhos de 51 pacientes. Cada paciente teve aleatoriamente um dos olhos operado com a técnica do PRK e o outro com LASEKb. Os pacientes foram acompanhados por 1 ano. RESULTADOS: Não houveram diferenças significativas entre os dois grupos na acuidade visual (AV) para longe, sem correção, (P = 0,5593). No 12o mês pós-operatório (PO), 98,04% dos olhos no grupo do PRK e 96,08% no grupo do LASEKb atingiram AV sem correção de 20/20. A previsibilidade, eficácia, segurança e estabilidade não apresentaram diferença estatisticamente significativa entre os grupos. O índice de segurança foi de 1 no PRK e 0,996 no LASEKb. Um olho do grupo do LASEKb perdeu uma linha de visão. A porcentagem de olhos que apresentou EE aos 12 meses na faixa de ±0,50 D foi de 94,1% no grupo do PRK e de 86,3% no grupo do LASEKb (P = 0,1883). Enquanto que na faixa de ±1,0 D foi de 100% no grupo do PRK e 98% no grupo do LASEKb (P = 0,3125). Não houve necessidade de reoperações. O tempo médio de cirurgia na técnica PRK foi de 304,86 + 58,77 segundos (aproximadamente 5 minutos) e na técnica LASEKb de 608,35 + 76,88 segundos (aproximadamente 10 minutos) (P < 0,001). O tempo médio de reepitelização no grupo do PRK foi de 4,35 ± 0,48 dias (variação, 4 a 5 dias) e no grupo do BLASEK foi de 4,75 ± 0,72 dias (variação, 4 a 6 dias) (P < 0,002). Os níveis de dor e o desconforto ocular PO não foram estatisticamente diferentes entre os grupos, entretanto houve uma tendência para menor dor no PRK (3,31 ± 4,09 vs 4,43 ± 4,27; P = 0,18). Houve uma redução estatisticamente significativa nos valores do teste de Schirmer em todas as avaliação PO, tanto no PRK (23,6 ± 8,1 vs 19,4 ± 10,1; P < 0,002) quanto no LASEKb (22,4 ± 8,7 vs 18,9 ± 9,7; P = 0,01), entretanto não houve diferença entre os grupos. A opacificação corneana (OC) PO foi pequena nos dois grupos. Somente no 1o mês foi observado diferença estatística entre os grupos, com maior intensidade da OC no grupo do LASEKb (0,18 ± 0,3881) quando comparado ao PRK (0,08 ± 0,2109) (P = 0,039936). A maior intensidade foi observada no 3o mês, com redução gradativa até o 12o mês. CONCLUSÃO: Dentro das condições deste estudo, conclui-se que o PRK e o LASEKb mostraram resultados semelhantes, exceto que o PRK apresentou menor tempo cirúrgico, reepitelização corneana mais rápida e menor OC no 30o PO. / PURPOSE: Comparatively evaluate the results of two techniques of surface excimer laser refractive surgery, photorefractive keratectomy (PRK) and butterfly laser-assisted subepithelial keratectomy (BLASEK). SETTING: Sadalla Amin Ghanem Eye Hospital, Joinville, Santa Catarina, Brazil. METHODS: This is a prospective, randomized and double-masked study including 102 eyes from 51 patients. Each patient was randomized to have one eye operated on with PRK and the other with BLASEK. Patients were followed for 1 year. RESULTS: There were no significant differences between the groups regarding uncorrected distant visual acuity (VA) (p= 0.5593). On the 12th post-operative (PO) month, 98.04% of the eyes in the PRK group and 96.08% in the BLASEK group reached uncorrected VA of 20/20. The predictability, efficacy, safety and stability did not present statically significant difference between groups. The safety index was of 1 for PRK and 0.996 for BLASEK. One eye of the BLASEK group lost one line on the 12th PO month. The percentage of the eyes that presented spherical equivalent at 12 months in the range of ±0.50 D was 94.1% in the PRK group and 86.3% in the BLASEK group (p = 0.1883). While in the range of ±1.0 D it was 100% in the PRK group and 98% in the BLASEK group (p = 0.3125). There were no retreatments. The mean surgical time was 304.86 + 58.77 seconds (approximately 5 minutes) in PRK and 608.35 + 76.88 seconds in BLASEK (approximately 10 minutes) (P < 0,001). The mean reepithelization time in the PRK group was 4.35 ± 0.48 days (range, 4 to 5 days), and in the BLASEK group was 4.75 ± 0.72 days (range, 4 to 6 days) (P < 0.002). Pain scores and ocular discomfort were not statistically different between groups, although there was a trend towards a lower pain level with PRK (3.31 ± 4.09 vs. 4.43 ± 4.27; P = 0.18). Schirmer test values were significantly reduced from preoperative levels through 12 months with both PRK (23.6 ± 8.1 vs. 19.4 ± 10.1; P < 0.002) and BLASEK (22.4 ± 8.7 vs. 18.9 ± 9.7; P = 0.01), however there was no difference between groups in any time point. Haze incidence was slight in both groups. Only in the 1st PO month statistical difference between the groups was observed, with higher intensity in the BLASEK group (0.18 ± 0.3881) when compared to the PRK (0.08 ± 0.2109) (p = 0.039936). The highest intensity was observed on the 3rd month, with gradual reduction until the 12th month. CONCLUSION: In the conditions of this study, it can be concluded that PRK and BLASEK showed similar results, except that PRK presented shorter surgical time, faster corneal reepithelization and less haze at 30th PO days. Astigmatismo Estudos prospectivos Método duplo-cego Miopia Astigmatism Double-blind method Laser assisted subepithelial keratectomy Myopia Prospective studies
75	Relaxation Dynamics and Decoherence of Excitons in II-VI Semiconductor Nanostructures Bajracharya, Pradeep 05 October 2007 (has links) No description available. Physics, Condensed Matter CdSe quantum dots radiative decay rate nonradiative decay rate capture rate ZnSe quantum well four-wave mixing exciton dephasing phase coherent photorefractive effect exciton density grating electron density grating optical Bloch equation
76	Untersuchung photorefraktiver Materialien mittels optischer Ptychographie / Investigation of photorefractive materials using optical ptychography Bernert, Constantin 05 January 2017 (has links) (PDF) In der vorliegenden Arbeit wird die neuartige Mikroskopiemethode der Ptychographie für die Untersuchung photorefraktiver Materialien genutzt. Photorefraktive Materialien zeichnen sich durch die Generation lichtinduzierter Brechungsindexänderungen aus. Die Ptychographie bietet die Möglichkeit, neben der generierten Brechungsindexänderung im photorefraktiven Material auch die für die Generation genutzte Intensitätsverteilung des Laserstrahls zu bestimmen. Es wird sowohl die Abhängigkeit der Brechungsindexänderung von der Zeit der Generation als auch die Abhängigkeit von der Polarisation des Lasers gemessen. Durch den Vergleich der gewonnenen Werte mit einer numerischen Simulation des photorefraktiven Effekts werden mikroskopische Parameter der lichtinduzierten Ladungswanderung ermittelt. Zudem wird aus der polarisationsabhängigen ptychographischen Messung das Raumladungsfeld und die korrespondierende Ladungsdichte im Material berechnet. Die Ptychographie liefert damit einen neuen Zugang zum quantitativen Verständnis der Photorefraktivität. / In the present thesis the novel microscopy technique of ptychography is applied to the investigation of photorefractive materials. Photorefractive materials exhibit a change of the refractive index due to the exposure to light. The method of ptychography determines the refractive index change of the material together with the intensity distribution of the laser beam that was used for its generation. In one part of the experiment the time dependence of the refractive index change versus the generation time is investigated, in the other part of the experiment the dependence of the refractive index change to the polarisation of the laser beam is examined. Microscopic parameters of the photorefractive charge migration are determined with the utilisation of a numerical simulation of the photorefractive effect and its comparison with the measurement. Finally, the whole space charge field with the corresponding space charge density is calculated from a set of ptychographic measurements of one refractive index change with different polarisation directions of the laser. The presented experiments and their evaluation show, that the method of ptychography opens a new possibility for a quantitative understanding of the photorefractive effect. Photorefraktivität photorefraktiv Photorefraktiver Effekt photorefraktives photorefraktiver photorefraktive lichtinduziert lichtinduzierte lichtinduzierter lichtinduziertes Lithiumniobat LiNbO3 LiNbO3:Fe linbo3 linbo3:fe Ladungstransport Brechungsindexänderung Brechungsindexänderungen Raumladungsfeld elektrooptischer Effekt Pockels Effekt photovoltaischer Effekt photovoltaische Stromdichte photovoltaische photovoltaischer Photovoltaik photovoltaissches Ptychographie ptychographisch ptychographische ptychographisches Interferometrie interferometrisch interferometrische interferometrische Untersuchung interferometrisches Holographie holographisches holographische holographische Untersuchung digitale Holographie photorefractive effect photorefractive photo refractive light-induced lightinduced light induced Lithium niobate Lithiumniobate LiNbO3 LiNbO3:Fe linbo3 linbo3:fe charge transport chargetransport refractive index change refractive index changes space charge field electrooptic effect electrooptic Pockels effect photovoltaic effect photovoltaic current photovoltaic ptychography ptychographic interferometry interferometric holography holographic digital holography ddc:530 rvk:VG 8600 Photorefraktivität Photorefraktiver Effekt Lithiumniobat Ladungstransport Brechungsindexänderung elektrooptischer Effekt Pockels Effekt photovoltaischer Effekt photovoltaische Stromdichte Photovoltaik Ptychographie Interferometrie Holographie digitale Holographie Photorefractive Effect Lithium niobate charge transport charge migration refractive index change electrooptic effect Pockels effect photovoltaic effect photovoltaic current ptychography interferometry holography digital holography
77	Untersuchung photorefraktiver Materialien mittels optischer Ptychographie Bernert, Constantin 04 October 2016 (has links) In der vorliegenden Arbeit wird die neuartige Mikroskopiemethode der Ptychographie für die Untersuchung photorefraktiver Materialien genutzt. Photorefraktive Materialien zeichnen sich durch die Generation lichtinduzierter Brechungsindexänderungen aus. Die Ptychographie bietet die Möglichkeit, neben der generierten Brechungsindexänderung im photorefraktiven Material auch die für die Generation genutzte Intensitätsverteilung des Laserstrahls zu bestimmen. Es wird sowohl die Abhängigkeit der Brechungsindexänderung von der Zeit der Generation als auch die Abhängigkeit von der Polarisation des Lasers gemessen. Durch den Vergleich der gewonnenen Werte mit einer numerischen Simulation des photorefraktiven Effekts werden mikroskopische Parameter der lichtinduzierten Ladungswanderung ermittelt. Zudem wird aus der polarisationsabhängigen ptychographischen Messung das Raumladungsfeld und die korrespondierende Ladungsdichte im Material berechnet. Die Ptychographie liefert damit einen neuen Zugang zum quantitativen Verständnis der Photorefraktivität.:1 Einleitung 2 Theoretische Vorbetrachtungen 2.1 Ptychographie 2.1.1 Messung 2.1.2 Modell und Rekonstruktion 2.1.3 Ortsauflösung 2.2 Photorefraktiver Efekt 2.2.1 Lithiumniobat - Musterbeispiel für die Photorefraktivität 2.2.2 Ein-Zentrum-Modell 2.2.3 Brechungsindexänderung 2.2.4 Hohe Intensitäten 2.3 Raumladungsfeld 2.3.1 Ableitung des Feldes aus den Messgrößen 2.3.2 Raumladungsverteilung 2.3.3 Oberflächendeformation 2.3.4 Dynamik der Ladungen und des Feldes 3 Messungen 3.1 Proben 3.1.1 Ptychographische Teststruktur 3.1.2 LiNbO3:Fe 3.2 Versuchsanordnung 3.2.1 Experimenteller Aufbau 3.2.2 Grenze der Ortsauflösung 3.2.3 Charakterisierung des Laserstrahls 3.2.4 Experimentelle Überprüfung der Näherungen 3.3 Dynamik der Brechungsindexänderung 3.4 Polarisationsabhängigkeit der Brechungsindexänderung 4 Auswertung 4.1 Dynamik des Raumladungsfeldes und der Ladungen 4.1.1 Simulation 4.1.2 Vergleich zwischen Messung und Simulation 4.1.3 Dynamik der Ladungsverteilung 4.1.4 Fazit 4.2 Berechnung des Raumladungsfeldes 4.2.1 Raumladungsfeld und Ladungsverteilung 4.2.2 Simulation 4.2.3 Asymmetrie der Ladungsverteilung 4.2.4 Fazit 5 Zusammenfassung Appendizes A Physikalische Konstanten B Tensoren für LiNbO3 C Ungenäherte Herleitung der Brechungsindexänderung D Implementierung eines iterativen Verfahrens zur Bestimmung der Dynamik des Ein-Zentrum-Modells E Quelltext der Implementierung des iterativen Verfahrens Literaturverzeichnis / In the present thesis the novel microscopy technique of ptychography is applied to the investigation of photorefractive materials. Photorefractive materials exhibit a change of the refractive index due to the exposure to light. The method of ptychography determines the refractive index change of the material together with the intensity distribution of the laser beam that was used for its generation. In one part of the experiment the time dependence of the refractive index change versus the generation time is investigated, in the other part of the experiment the dependence of the refractive index change to the polarisation of the laser beam is examined. Microscopic parameters of the photorefractive charge migration are determined with the utilisation of a numerical simulation of the photorefractive effect and its comparison with the measurement. Finally, the whole space charge field with the corresponding space charge density is calculated from a set of ptychographic measurements of one refractive index change with different polarisation directions of the laser. The presented experiments and their evaluation show, that the method of ptychography opens a new possibility for a quantitative understanding of the photorefractive effect.:1 Einleitung 2 Theoretische Vorbetrachtungen 2.1 Ptychographie 2.1.1 Messung 2.1.2 Modell und Rekonstruktion 2.1.3 Ortsauflösung 2.2 Photorefraktiver Efekt 2.2.1 Lithiumniobat - Musterbeispiel für die Photorefraktivität 2.2.2 Ein-Zentrum-Modell 2.2.3 Brechungsindexänderung 2.2.4 Hohe Intensitäten 2.3 Raumladungsfeld 2.3.1 Ableitung des Feldes aus den Messgrößen 2.3.2 Raumladungsverteilung 2.3.3 Oberflächendeformation 2.3.4 Dynamik der Ladungen und des Feldes 3 Messungen 3.1 Proben 3.1.1 Ptychographische Teststruktur 3.1.2 LiNbO3:Fe 3.2 Versuchsanordnung 3.2.1 Experimenteller Aufbau 3.2.2 Grenze der Ortsauflösung 3.2.3 Charakterisierung des Laserstrahls 3.2.4 Experimentelle Überprüfung der Näherungen 3.3 Dynamik der Brechungsindexänderung 3.4 Polarisationsabhängigkeit der Brechungsindexänderung 4 Auswertung 4.1 Dynamik des Raumladungsfeldes und der Ladungen 4.1.1 Simulation 4.1.2 Vergleich zwischen Messung und Simulation 4.1.3 Dynamik der Ladungsverteilung 4.1.4 Fazit 4.2 Berechnung des Raumladungsfeldes 4.2.1 Raumladungsfeld und Ladungsverteilung 4.2.2 Simulation 4.2.3 Asymmetrie der Ladungsverteilung 4.2.4 Fazit 5 Zusammenfassung Appendizes A Physikalische Konstanten B Tensoren für LiNbO3 C Ungenäherte Herleitung der Brechungsindexänderung D Implementierung eines iterativen Verfahrens zur Bestimmung der Dynamik des Ein-Zentrum-Modells E Quelltext der Implementierung des iterativen Verfahrens Literaturverzeichnis info:eu-repo/classification/ddc/530 ddc:530
78	Nichtlineare Optik mit ultrakurzen Laserpulsen: Suszeptibilität dritter Ordnung und kleine Polaronen sowie Interferenz und Holographie verschiedenfarbiger Laserpulse Badorreck, Holger 13 June 2016 (has links) In der vorliegenden Arbeit werden die nichtlinearen optischen Eigenschaften der Materialien Lithiumniobat und Di-Zinn-Hexathiohypodiphosphat aufgrund der Suszeptibilität 3. Ordnung und kleiner Polaronen untersucht. Zudem wird gezeigt, dass die Interferenz verschiedenfarbiger Laserpulse die Aufzeichnung von statischen und dynamischen holographischen Gittern ermöglicht. Ein Teil dieser Arbeit ist in den im Anhang angegebenen 6 Publikationen bereits veröffentlicht. Lithiumniobat wird mit einer Erweiterung des Z-Scan Experiments untersucht, welches die Pulslängenabhängige Messung der nichtlinearen Absorption und der nichtlinearen Brechungsindexänderung ermöglicht. Dabei konnte festgestellt werden, dass bei sehr kurzen Pulslängen von 70 fs ein Effekt der Polaronen auf die nichtlineare Absorption vernachlässigbar ist und die Zwei-Photonen-Absorption die nichtlineare Absorption dominiert. Mit größerer Pulslänge gibt es allerdings Abweichungen zwischen der Theorie der Zwei-Photonen-Absorption und den Messergebnissen. Mit der Entwicklung eines Polaronen-Anregungs-Modells, welches eine polaronische Absorption aufgrund wiederholtem optisch induziertem Hopping annimmt, konnte dieser Effekt konsistent erklärt werden. Die Messungen der nichtlinearen Brechungsindexänderung lassen darauf schließen, dass sowohl freie Ladungsträger als auch kleine Polaronen neben der Suszeptibilität 3. Ordnung einen Einfluss auf die Brechungsindexänderung haben, da eine nichtlineare Abhängigkeit von der Intensität auch bei Pulslängen von 70 fs festgestellt werden konnte. Analog dazu konnte in Di-Zinn-Hexathiohypodiphosphat ein großer Zwei-Photonen-Absorptionskoeffizient festgestellt werden, welcher für Photonenenergien nahe der Bandkante Werte zeigt, die größer sind als theoretischen Überlegungen zeigen. Eine transiente Absorption nach optischer Anregung, gemessen durch ein Anreg-Abtast-Experiment, sowie Literatur legen nahe, dass in Di-Zinn-Hexathiohypodiphosphat gebundene Lochpolaronen durch optische Anregung entstehen können. Durch den hohen Zwei-Photonen-Absorptionskoeffizienten konnte das Aufzeichnen eines kontrastreichen, dynamischen Amplitudengitters mittels Femtosekundenpulsen gezeigt und nachgewiesen werden. Die Kürze der Femtosekundenpulse ermöglicht aber nicht nur das Aufzeichnen eines Zwei-Photonen-Absorptionsgitters aufgrund der hohen Intensitäten, sondern erlaubt zudem die Beobachtung von Interferenz zwischen verschiedenfarbigen Pulsen. In der Zeitspanne der Pulslänge beträgt die Bewegung der Interferenzstreifen, welche in der Größenordnung der Lichtgeschwindigkeit liegt, nur ein Bruchteil der Streifendistanz, sodass das Interferenzmuster eingefroren und beobachtbar erscheint. Somit lassen sich statische Hologramme in holographischen Filmen, wie auch dynamische Hologramme aufzeichnen. Über ein dynamisches holographisches Gitter mittels Zwei-Photonen-Absorption konnte so eine Frequenzkonversion durch Dopplerverschiebung in Lithiumniobat gezeigt werden. Lithiumniobat Nichtlineare Optik kleine Polaronen Interferenz Holographie Ultrakurze Laserpulse Z-Scan lithium niobate nonlinear optics small polarons interference holography ultrashort laser pulses z-scan 33.38 - Quantenoptik, nichtlineare Optik 33.61 - Festkörperphysik 42.70.Mp - Nonlinear optical crystals 78.20.Ci - Optical constants ddc:530
79	Étude du transport de charges dans le niobate de lithium massif et réalisation de fonctions électro-optiques dans le niobate de lithium périodiquement polarisé / Study of charge transport in bulk lithium niobate and realization of electro-optical functions in periodically poled lithium niobate Mhaouech, Imed 24 March 2017 (has links) Le premier volet de cette thèse est consacré à la modélisation des phénomènes de transport dans le LN. Partant d'une analyse critique des modèles de bande usuels, nous montrons leur inadéquation dans le cas du LN et nous proposons un modèle de saut basé sur la théorie des petits polarons. Nous étudions d'abord par simulation Monte-Carlo la décroissance d'une population de polarons liés NbLi4+ relaxant vers des pièges profonds FeLi3+. Nous montrons que les pièges FeLi3+ ont des rayons effectifs particulièrement grands, rayons qui augmentent encore à température décroissante, et limitent considérablement les longueurs de diffusion des polarons. Les résultats de simulations sont ensuite confrontés aux résultats expérimentaux obtenus par différentes techniques ; Absorption photo-induite, Raman, Enregistrement holographique et Pompe-sonde. Le deuxième volet de cette thèse est consacré aux applications électro-optiques dans le LN périodiquement polarisé (PPLN). Sous l’effet d’une tension électrique, l’indice de réfraction du PPLN est périodiquement diminué et augmenté, formant ainsi un réseau d’indice activable électriquement. Un premier composant utilisant l’effet électro-optique dans du PPLN a été développé et démontré expérimentalement. Dans ce composant, la lumière est défléchie sous l’effet de la tension électrique par le réseau d’indice. Ce déflecteur de Bragg atteint une efficacité de diffraction proche de 100% avec une faible tension de commande de l’ordre de 5 V. Un deuxième composant a également été proposé, où la lumière se propage perpendiculairement aux parois de domaines du PPLN. Dans cette configuration un réflecteur de Bragg électro-optique peut être réalisé / The first part of this thesis is devoted to the modeling of transport phenomena in the LN. From a critical analysis of the usual band models, we show their inadequacy in the case of LN and we propose a hopping model based on the theory of small polarons. We first study by Monte-Carlo simulation the population decay of bound polarons NbLi4+ in deep traps FeLi3+. We show that the traps (FeLi3+) have particularly large effective radii, which increase further at decreasing temperature, and considerably limit the diffusion lengths of the polarons. The results of simulations are then compared with experimental results obtained by different techniques; Light-induced absorption, Raman, Holographic storage and Pump-Probe. The second part of this thesis is devoted to electro-optical applications in the periodically poled LN (PPLN). Under the effect of an electrical voltage, the refractive index of the PPLN is periodically decreased and increased, thus forming an electrically activatable index grating. A first component using the electro-optical effect in PPLN has been developed and demonstrated experimentally. In this component, the light is deflected under the effect of the electrical voltage by the index grating. This Bragg deflector achieves a diffraction efficiency of close to 100% with a low drive voltage of the order of 5 V. A second component has also been proposed, where light propagates perpendicularly to the domain walls of the PPLN. In this configuration an electro-optic Bragg reflector can be realized Niobate de lithium Effet photoréfractif Transport de charge Polaron Absorption photo-induite Raman Enregistrement holographique Réseaux de diffraction Electro-optique Dispositif de commutation optique Filtre de Bragg Modulateur électro-optique Lithium niobate Photorefractive effect Charge transport Polaron Light-induced absorption Raman Holographic storage Periodically poled lithium niobate Diffraction gratings Electro-optic Optical switching devices Bragg filter Electro-optic modulator 620.112 95 620.112 97
80	Wellenlängenmultiplexing mit thermisch fixierten Volumenphasenhologrammen in photorefraktiven Lithiumniobat-Kristallen / Wavelength Division Multiplexing with Thermally Fixed Volume Phase Holograms in Photorefractive Lithium Niobate Crystals Breer, Stefan 08 September 2000 (has links) Wavelength division multiplexing (WDM) is essential for further enhancement of the transmission capacities of optical telecommunication systems. Key devices in WDM networks are multiplexing/demultiplexing components, which enable the combination/separation of several carrier waves with different wavelengths for the purpose of simultaneous transmission through one optical fibre. These components can be realized using Bragg diffraction from volume holographic gratings. Especially reflection holograms provide a pronounced wavelength selectivity which makes them attractive for free-space WDM applications. Holograms can be stored permanently in photorefractive lithium niobate crystals by the method of Thermal Fixing. Heating of the crystal during or after the recording process and subsequent development by homogeneous illumination at room temperature create nonvolatile holograms. The recording and development processes of Thermal Fixing in iron- and copper-doped lithium niobate crystals were investigated. Macroscopic Gaussian-shaped intensity patterns were used to analyse the origin of the fixing mechanism. Spatially resolved absorption measurements were performed to determine the concentration profiles of electron traps (Fe II/III) and protons. Results of computer simulations were compared with experimental results, which showed that protons can be found to work as compensators during hologram recording at temperatures around 180 degree C. Nevertheless thermal fixing without protons was possible, another compensation mechanism stood in. The obtained refractive-index changes were due to the electro-optic effect, other contributions could be neglected. With this detailed knowledge about thermal fixing, a two-channel demultiplexing unit was built by superposition of two thermally fixed reflection holograms in an iron-doped lithium niobate crystal. For this purpose a special two-beam interference setup with precisely adjustable writing angles was arranged in a vacuum chamber to eliminate thermally induced phase disturbances of the holographic recording procedure. Continuous development of the holograms by incoherent light was necessary. In the dark, the enhanced dark conductivity of the crystal used gave rise to a hologram degradation within about one day. Large diffraction efficiencies were attained (intensity losses between 2.3 and 5.2 dB only) uilizing crystals with high-quality polished surfaces. The crosstalk supression of the realized demultiplexer was > 25 dB, which is comparable with the performance of other multiplexing techniques like fibre Bragg gratings or arrayed-waveguide gratings. The low polarization dependence of the demultiplexer can be improved by superposition of two holograms for each channel. wavelength division multiplexing photorefractive media thermal fixing 29 - Physik, Astronomie 42.25.-p - Wave optics 42.40.Pa - Volume holograms 42.82.Fv - Hybrid systems ddc:530

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