Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resona...Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of the grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared with each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, et al., on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained.展开更多
Spectroscopic properties of Ce-doped yttrium orthoaluminate （Ce：YA1O3 or Ce：YAP） crystals gown by temperature gradient technique （TGT） were investigated, and the effects of the growth conditions on the propertie...Spectroscopic properties of Ce-doped yttrium orthoaluminate （Ce：YA1O3 or Ce：YAP） crystals gown by temperature gradient technique （TGT） were investigated, and the effects of the growth conditions on the properties were analyzed. Methods of optical absorption （OA）, photoluminescence （PL）, photoluminescence decay （PLD）, X-my excited luminescence （XL） and cathodeluminescence （CL） were used in these investigations. The results showed that the absorption band peak at 202,394 and 532 nm originated from F and F^＋ color center induced by the weak reducing growth atmosphere, green emission band near 500 nm derived from Ce3^＋ -Ce^3＋ pairs and band at 650 - 850 nm from some unintentional impurity in crystals.展开更多
A methodology for the fabrication of composite （Nb205）l-x（SiO2）~ thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating dep...A methodology for the fabrication of composite （Nb205）l-x（SiO2）~ thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technol- ogy. The optical properties of the composite films varying with the composition of the material are studied in detail, Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a re- flection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra axe in good agreement with each other, The causes of the slight differences between them are also analysed.展开更多
We suggest a design method of graded-refractive-index （GRIN） antireflection （AR） coating for s-polarized or p- polarized light at off-normal incidence. The spectrum characteristic of the designed antireflection co...We suggest a design method of graded-refractive-index （GRIN） antireflection （AR） coating for s-polarized or p- polarized light at off-normal incidence. The spectrum characteristic of the designed antireflection coating with a quintic effective refractive-index profile for a given state of polarization has been discussed. In addition, the genetic algorithm was used to optimize the refractive index profile of the GRIN antireflection for reducing the mean reflectance of s- and p-polarizations. The average reflectance loss was reduced to only 0.04% by applying optimized GRIN AR coatings onto BK7 glass over the wavelength range from 400 to 800 nm at the incident angle of θo = 70°.展开更多
The design and the deposition of a rugate filter for broadband applications are discussed.The bandwidth is extended by increasing the rugate period continuously with depth.The width and the smoothness of the reflectio...The design and the deposition of a rugate filter for broadband applications are discussed.The bandwidth is extended by increasing the rugate period continuously with depth.The width and the smoothness of the reflection band with the distribution of the periods are investigated.The improvement of the steepness of the stopband edges and the suppression of the side lobes in the transmission zone are realized by adding two apodized rugate structures with fixed periods at the external broadband rugate filter interfaces.The rapidly alternating deposition technology is used to fabricate a rugate filter sample.The measured transmission spectrum with a reflection bandwidth of approximately 505 nm is close to that of the designed broadband rugate filter except a transmittance peak in the stopband.Based on the analysis of the cross-sectional scanning electron microscopic image of the sample,it is found that the transmission peak is most likely to be caused by the instability of the deposition rate.展开更多
Ta2O5/SiO2 and ZrO2/SiO2 high reflecting （HR） coatings are prepared by ion beam sputtering and electron beam evaporation, respectively. The laser-induced damage thresholds （LIDTs） of these samples are investigated...Ta2O5/SiO2 and ZrO2/SiO2 high reflecting （HR） coatings are prepared by ion beam sputtering and electron beam evaporation, respectively. The laser-induced damage thresholds （LIDTs） of these samples are investigated with 2μm femtosecond pulse lasers （80fs, 1kHz）. It is found that the Ta2O5/SiO2 HR coating has a higher capability of laser damage resistance than the ZrO2/SiO2 HR coating in the 2μm femtosecond regime. The scanning electron microscope results show that the damage sites of the ZrO2//SiO2 FIR coating have a relatively porous structure, the loose structure of coatings will provide more sites for water molecules, and the LIDTs of HR coatings will be reduced as a result of the strong water absorption at the wavelength of 2 μm.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704079)
文摘Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of the grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared with each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, et al., on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained.
基金Project supported by the National Natural Science Foundation of China (60607015)
文摘Spectroscopic properties of Ce-doped yttrium orthoaluminate （Ce：YA1O3 or Ce：YAP） crystals gown by temperature gradient technique （TGT） were investigated, and the effects of the growth conditions on the properties were analyzed. Methods of optical absorption （OA）, photoluminescence （PL）, photoluminescence decay （PLD）, X-my excited luminescence （XL） and cathodeluminescence （CL） were used in these investigations. The results showed that the absorption band peak at 202,394 and 532 nm originated from F and F^＋ color center induced by the weak reducing growth atmosphere, green emission band near 500 nm derived from Ce3^＋ -Ce^3＋ pairs and band at 650 - 850 nm from some unintentional impurity in crystals.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10704079 and 10976030)
文摘A methodology for the fabrication of composite （Nb205）l-x（SiO2）~ thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technol- ogy. The optical properties of the composite films varying with the composition of the material are studied in detail, Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a re- flection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra axe in good agreement with each other, The causes of the slight differences between them are also analysed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10704079 and 10976030)
文摘We suggest a design method of graded-refractive-index （GRIN） antireflection （AR） coating for s-polarized or p- polarized light at off-normal incidence. The spectrum characteristic of the designed antireflection coating with a quintic effective refractive-index profile for a given state of polarization has been discussed. In addition, the genetic algorithm was used to optimize the refractive index profile of the GRIN antireflection for reducing the mean reflectance of s- and p-polarizations. The average reflectance loss was reduced to only 0.04% by applying optimized GRIN AR coatings onto BK7 glass over the wavelength range from 400 to 800 nm at the incident angle of θo = 70°.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704079)the NSAF Joint Fund,China(Grant No. 10976030)
文摘The design and the deposition of a rugate filter for broadband applications are discussed.The bandwidth is extended by increasing the rugate period continuously with depth.The width and the smoothness of the reflection band with the distribution of the periods are investigated.The improvement of the steepness of the stopband edges and the suppression of the side lobes in the transmission zone are realized by adding two apodized rugate structures with fixed periods at the external broadband rugate filter interfaces.The rapidly alternating deposition technology is used to fabricate a rugate filter sample.The measured transmission spectrum with a reflection bandwidth of approximately 505 nm is close to that of the designed broadband rugate filter except a transmittance peak in the stopband.Based on the analysis of the cross-sectional scanning electron microscopic image of the sample,it is found that the transmission peak is most likely to be caused by the instability of the deposition rate.
文摘Ta2O5/SiO2 and ZrO2/SiO2 high reflecting （HR） coatings are prepared by ion beam sputtering and electron beam evaporation, respectively. The laser-induced damage thresholds （LIDTs） of these samples are investigated with 2μm femtosecond pulse lasers （80fs, 1kHz）. It is found that the Ta2O5/SiO2 HR coating has a higher capability of laser damage resistance than the ZrO2/SiO2 HR coating in the 2μm femtosecond regime. The scanning electron microscope results show that the damage sites of the ZrO2//SiO2 FIR coating have a relatively porous structure, the loose structure of coatings will provide more sites for water molecules, and the LIDTs of HR coatings will be reduced as a result of the strong water absorption at the wavelength of 2 μm.
