There has been an increasing interest in the research of diode laser pumped sol id state lasers in recent years because of the rapid development of high power d iode laser.This paper reports the crystal growth and the...There has been an increasing interest in the research of diode laser pumped sol id state lasers in recent years because of the rapid development of high power d iode laser.This paper reports the crystal growth and the spectral properties of low temperature phase Nd 3+ : β LaSc 3(BO 3) 4crystal.The low temp er ature phase β LaSc 3(BO 3) 4 crystal belongs to the rhombohedral with space group R 32 and cell parameters a =0.9819, c =0.7987mm, Z =3.The 5at.% Nd 3+ :β LaSc 3(BO 3) 4 crystal is only grown by the flux method.Nd 3+ :β LaSc 3(BO 3) 4 crystal with dimension of 43mm×32mm×15mm has been g rown by TSSG method.Its spectral properties have been investigated.The results show that the FWHM of absorption band at 808nm is 3.3nm,the fluorescence lifetime is 112μs,the emission cross section at 1063nm is 15.6×10 -20 cm 2.Based on J udd Ofelt theory,the spectral parameters were obtained:the parameters of line s trengths Ω λ are Ω 2=2.85×10 -20 cm 2, Ω 4=3.69×10 -20 cm 2, Ω 6=4.73×10 -20 cm 2,the ratiative lifetime is 226μs,thu s,the quantum efficiency is 49.4%.On the other hand ,the second harmonic genera tion (SHG) effect has been observed in Nd 3+ :β LaSc 3(BO 3) 4 crystal. In conclusion,Nd 3+ : β LaSc 3(BO 3) 4 crystal cae be regarded as a king of high efficiency self frequency laser material.展开更多
One of the advantages of laser speckle is detecting microvascular through image processing. This paper proposes a new image processing method for laser speckle, adaptive window method that adaptively processes laser s...One of the advantages of laser speckle is detecting microvascular through image processing. This paper proposes a new image processing method for laser speckle, adaptive window method that adaptively processes laser speckle images in the space. Disadvantage of conventional fixed window method is that it uses the same window size regardless of target areas. Inherently laser speckle contains undesired noise. Thus a large window is helpful for removing the noise, but it results in low resolution of image. Otherwise a small window may detect micro vascular but it has limits in noise removal. To overcome this trade-off, the concept of adaptive window method is newly introduced to conventional laser speckle image analysis. In addition, the modified adaptive window method applied to other selection images. We have compared conventional Laser Speckle Contrast Analysis （LASCA） and its variants with the proposed method in terms of image quality and processing complexity, Moreover compared the result of the accompamed changing sdection images have also been compared.展开更多
文摘There has been an increasing interest in the research of diode laser pumped sol id state lasers in recent years because of the rapid development of high power d iode laser.This paper reports the crystal growth and the spectral properties of low temperature phase Nd 3+ : β LaSc 3(BO 3) 4crystal.The low temp er ature phase β LaSc 3(BO 3) 4 crystal belongs to the rhombohedral with space group R 32 and cell parameters a =0.9819, c =0.7987mm, Z =3.The 5at.% Nd 3+ :β LaSc 3(BO 3) 4 crystal is only grown by the flux method.Nd 3+ :β LaSc 3(BO 3) 4 crystal with dimension of 43mm×32mm×15mm has been g rown by TSSG method.Its spectral properties have been investigated.The results show that the FWHM of absorption band at 808nm is 3.3nm,the fluorescence lifetime is 112μs,the emission cross section at 1063nm is 15.6×10 -20 cm 2.Based on J udd Ofelt theory,the spectral parameters were obtained:the parameters of line s trengths Ω λ are Ω 2=2.85×10 -20 cm 2, Ω 4=3.69×10 -20 cm 2, Ω 6=4.73×10 -20 cm 2,the ratiative lifetime is 226μs,thu s,the quantum efficiency is 49.4%.On the other hand ,the second harmonic genera tion (SHG) effect has been observed in Nd 3+ :β LaSc 3(BO 3) 4 crystal. In conclusion,Nd 3+ : β LaSc 3(BO 3) 4 crystal cae be regarded as a king of high efficiency self frequency laser material.
基金supported by the SEOUL R&BD NT070079,Korea,the ITRC(Information Technology Research Center)support program supervised by the ⅡTA(Institute for Information Technology Advancement)
文摘One of the advantages of laser speckle is detecting microvascular through image processing. This paper proposes a new image processing method for laser speckle, adaptive window method that adaptively processes laser speckle images in the space. Disadvantage of conventional fixed window method is that it uses the same window size regardless of target areas. Inherently laser speckle contains undesired noise. Thus a large window is helpful for removing the noise, but it results in low resolution of image. Otherwise a small window may detect micro vascular but it has limits in noise removal. To overcome this trade-off, the concept of adaptive window method is newly introduced to conventional laser speckle image analysis. In addition, the modified adaptive window method applied to other selection images. We have compared conventional Laser Speckle Contrast Analysis （LASCA） and its variants with the proposed method in terms of image quality and processing complexity, Moreover compared the result of the accompamed changing sdection images have also been compared.
