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Antti V. Räisänen - One of the best experts on this subject based on the ideXlab platform.
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Monostatic Reflectivity and Transmittance of Radar Absorbing Materials at 650 GHz
IEEE Transactions on Microwave Theory and Techniques, 2008Co-Authors: Aleksi Tamminen, Anne Lönnqvist, Juha Mallat, Antti V. RäisänenAbstract:Transmittance and monostatic Reflectivity of different radar absorbing materials at 650 GHz are presented. The Reflectivity was measured in plane-wave conditions in a radar cross-section (RCS) range with vertical polarization. The lowest Reflectivity level (-70 dB) was achieved with commercial absorbers TK THz RAM and Firam-500 with oblique incidence angles. Floor carpets were also studied, and the Reflectivity level of those was found to be sufficiently low (from -50 to -60 dB) for use in antenna test ranges. Results agree with earlier studies and indicate the applicability of the RCS method in Reflectivity measurements also at 650 GHz.
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Monostatic Reflectivity Measurement of Radar Absorbing Materials at 310 GHz
IEEE Transactions on Microwave Theory and Techniques, 2006Co-Authors: Anne Lönnqvist, Aleksi Tamminen, Juha Mallat, Antti V. RäisänenAbstract:This paper presents monostatic Reflectivity measurements of radar absorbing materials at 310 GHz in a phase-hologram-based compact range. The radar cross-section method was used and the backscattered reflection was measured with horizontal and vertical polarizations in plane-wave conditions. Transmission was also studied. The Reflectivity was measured over an incidence angle of 0deg-45deg. The Reflectivity of Thomas Keating Terahertz RAM at normal incidence was found to be -56 dB-the smallest of the studied materials. The Reflectivity of carpet material measured was also below -40 dB and it was found to be suitable for use as an absorber. The results are in line with those available from previous studies of Reflectivity and complement them with new materials, frequency, and angle information
Srinivas R. Sadda - One of the best experts on this subject based on the ideXlab platform.
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Choroidal Imaging with Swept-Source Optical Coherence Tomography in Patients with Birdshot Chorioretinopathy: Choroidal Reflectivity and Thickness
Ophthalmology, 2017Co-Authors: Anna Dastiridou, Elodie Bousquet, Laura Kuehlewein, Tudor Tepelus, Dominique Monnet, Sawsen Salah, Antoine P. Brézin, Srinivas R. SaddaAbstract:Purpose To characterize choroidal thickness and choroidal Reflectivity in the eyes of patients with birdshot chorioretinopathy (BSCR). Design Cross-sectional observational study. Participants Two hundred twenty BSCR patients and 59 healthy controls. Methods Patients with BSCR and healthy controls underwent imaging of the macula in both eyes with a swept-source optical coherence tomography device (DRI-OCT1 Atlantis; Topcon). Images were exported from the device, and analysis was performed by 2 graders in the Doheny Image Reading Center using Image J software. The choroidal thickness at the foveal center was measured. In addition, the inner and outer boundaries of the choroid and retinal pigment epithelium (RPE) as well as the inner retinal surface all were segmented to allow the brightness and Reflectivity of the pixels in the choroid, RPE band, and overlying vitreous to be quantified. An adjusted or normalized choroidal Reflectivity, with the RPE as the bright reference standard and the vitreous as the dark reference standard, was computed using the formula: normalized choroidal Reflectivity = (choroidal Reflectivity−vitreous Reflectivity)/RPE Reflectivity. Main Outcome Measures Choroidal Reflectivity and choroidal thickness. Results Three hundred eighty-six eyes in the BSCR group and 59 eyes in the control group were included in this analysis. Higher choroidal Reflectivity and lower choroidal thickness were documented in inactive BSCR patients compared with active BSCR and controls ( P P r = −0.793; P P Conclusions Choroidal Reflectivity and choroidal thickness changes are evident in active and inactive BSCR patients. Novel choroidal parameters such as choroidal Reflectivity may warrant further study in the setting of BSCR.
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relationship between subretinal hyperreflective material Reflectivity and volume in patients with neovascular age related macular degeneration following anti vascular endothelial growth factor treatment
Ophthalmic Surgery and Lasers, 2015Co-Authors: Wissam Charafeddin, Muneeswar Gupta Nittala, Aldo Oregon, Srinivas R. SaddaAbstract:BACKGROUND AND OBJECTIVE To assess the relationship between subretinal hyperreflective material (SRHM) Reflectivity and volume in patients treated with anti-vascular endothelial growth factor (VEGF) therapy for choroidal neovascularization secondary to exudative age-related macular degeneration (AMD). PATIENTS AND METHODS Data from 17 eyes of 16 patients with neovascular AMD undergoing anti-VEGF therapy were collected retrospectively. Optical coherence tomography (OCT) data were obtained using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) 512 × 128 macular cube protocol. Detailed manual segmentation was performed for each case using customized grading software. RESULTS The mean macular volume declined from 10.4 mm(3) at baseline to 9.6 mm(3) at 12 months. SRHM volume declined from 0.33 mm(3) to 0.12 mm(3), whereas Reflectivity increased from 0.48 to 0.64 units (P = .012). SRHM Reflectivity correlated positively with logarithm of the minimum angle of resolution (logMAR) acuity (r = .49, P = .04) but correlated with SRHM volume (r = -0.50, P = .04) only at baseline. CONCLUSION SRHM Reflectivity, which correlated partially with SRHM volume, appears to carry independent information regarding disease activity. SRHM Reflectivity may be useful for monitoring disease activity and response to therapy.
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relationship between subretinal hyperreflective material Reflectivity and volume in patients with neovascular age related macular degeneration following anti vascular endothelial growth factor treatment
Ophthalmic Surgery and Lasers, 2015Co-Authors: Wissam Charafeddin, Muneeswar Gupta Nittala, Aldo Oregon, Srinivas R. SaddaAbstract:Abstract To assess the relationship between subretinal hyperreflective material (SRHM) Reflectivity and volume in patients treated with anti-vascular endothelial growth factor (VEGF) therapy for choroidal neovascularization secondary to exudative age-related macular degeneration (AMD). Data from 17 eyes of 16 patients with neovascular AMD undergoing anti-VEGF therapy were collected retrospectively. Optical coherence tomography (OCT) data were obtained using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) 512 × 128 macular cube protocol. Detailed manual segmentation was performed for each case using customized grading software. The mean macular volume declined from 10.4 mm(3) at baseline to 9.6 mm(3) at 12 months. SRHM volume declined from 0.33 mm(3) to 0.12 mm(3), whereas Reflectivity increased from 0.48 to 0.64 units (P = .012). SRHM Reflectivity correlated positively with logarithm of the minimum angle of resolution (logMAR) acuity (r = .49, P = .04) but correlated with SRHM volume (r = -0.50, P = .04) only at baseline. SRHM Reflectivity, which correlated partially with SRHM volume, appears to carry independent information regarding disease activity. SRHM Reflectivity may be useful for monitoring disease activity and response to therapy.
Argishti Melikyan - One of the best experts on this subject based on the ideXlab platform.
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directly Reflectivity modulated laser
Journal of Lightwave Technology, 2018Co-Authors: Po Dong, Anaelle Maho, R Brenot, Y K Chen, Argishti MelikyanAbstract:Directly modulated lasers (DMLs) have been widely employed in data centers and other short-reach interconnect applications, thanks to their low cost and low power consumption. Nevertheless, these lasers have small wavelength tuning ranges and are limited to produce only intensity-encoded optical signals through modulating the gain in the active region. Therefore, it is difficult to use them in metro/long-haul applications, where tunable lasers and coherent modulation formats are preferred. In this paper, we propose and demonstrate a novel directly Reflectivity modulated laser (DRML), which overcomes these limitations by modulating the Reflectivity of the cavity mirror of a wavelength tunable laser. The DRML can offer wide wavelength tunability, low-chirp, and high-speed operation, and allows pure phase modulation. More importantly, the DRML still keeps the key benefit of traditional DMLs by requiring low RF drive powers. We experimentally demonstrate a DRML based on a hybrid silicon/III–V platform. About 25/40 Gb/s on–off-keying and 25 Gb/s binary phase-shift keying signals are generated and the wavelength tunability is >20 nm. This device shows a great potential for both short-reach and long-reach optical communications.
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directly Reflectivity modulated laser
European Conference on Optical Communication, 2017Co-Authors: Po Dong, Anaelle Maho, R Brenot, Y K Chen, Argishti MelikyanAbstract:We report a novel directly Reflectivity modulated laser (DRML) allowing for phase and intensity modulation through a Michelson interferometric mirror. On-off keying at 25/40 Gb/s and binary phase-shift keying at 25 Gb/s are demonstrated. The wavelength tunability is >20 nm.
Anne Lönnqvist - One of the best experts on this subject based on the ideXlab platform.
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Monostatic Reflectivity and Transmittance of Radar Absorbing Materials at 650 GHz
IEEE Transactions on Microwave Theory and Techniques, 2008Co-Authors: Aleksi Tamminen, Anne Lönnqvist, Juha Mallat, Antti V. RäisänenAbstract:Transmittance and monostatic Reflectivity of different radar absorbing materials at 650 GHz are presented. The Reflectivity was measured in plane-wave conditions in a radar cross-section (RCS) range with vertical polarization. The lowest Reflectivity level (-70 dB) was achieved with commercial absorbers TK THz RAM and Firam-500 with oblique incidence angles. Floor carpets were also studied, and the Reflectivity level of those was found to be sufficiently low (from -50 to -60 dB) for use in antenna test ranges. Results agree with earlier studies and indicate the applicability of the RCS method in Reflectivity measurements also at 650 GHz.
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Monostatic Reflectivity Measurement of Radar Absorbing Materials at 310 GHz
IEEE Transactions on Microwave Theory and Techniques, 2006Co-Authors: Anne Lönnqvist, Aleksi Tamminen, Juha Mallat, Antti V. RäisänenAbstract:This paper presents monostatic Reflectivity measurements of radar absorbing materials at 310 GHz in a phase-hologram-based compact range. The radar cross-section method was used and the backscattered reflection was measured with horizontal and vertical polarizations in plane-wave conditions. Transmission was also studied. The Reflectivity was measured over an incidence angle of 0deg-45deg. The Reflectivity of Thomas Keating Terahertz RAM at normal incidence was found to be -56 dB-the smallest of the studied materials. The Reflectivity of carpet material measured was also below -40 dB and it was found to be suitable for use as an absorber. The results are in line with those available from previous studies of Reflectivity and complement them with new materials, frequency, and angle information
Aleksi Tamminen - One of the best experts on this subject based on the ideXlab platform.
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Monostatic Reflectivity and Transmittance of Radar Absorbing Materials at 650 GHz
IEEE Transactions on Microwave Theory and Techniques, 2008Co-Authors: Aleksi Tamminen, Anne Lönnqvist, Juha Mallat, Antti V. RäisänenAbstract:Transmittance and monostatic Reflectivity of different radar absorbing materials at 650 GHz are presented. The Reflectivity was measured in plane-wave conditions in a radar cross-section (RCS) range with vertical polarization. The lowest Reflectivity level (-70 dB) was achieved with commercial absorbers TK THz RAM and Firam-500 with oblique incidence angles. Floor carpets were also studied, and the Reflectivity level of those was found to be sufficiently low (from -50 to -60 dB) for use in antenna test ranges. Results agree with earlier studies and indicate the applicability of the RCS method in Reflectivity measurements also at 650 GHz.
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Monostatic Reflectivity Measurement of Radar Absorbing Materials at 310 GHz
IEEE Transactions on Microwave Theory and Techniques, 2006Co-Authors: Anne Lönnqvist, Aleksi Tamminen, Juha Mallat, Antti V. RäisänenAbstract:This paper presents monostatic Reflectivity measurements of radar absorbing materials at 310 GHz in a phase-hologram-based compact range. The radar cross-section method was used and the backscattered reflection was measured with horizontal and vertical polarizations in plane-wave conditions. Transmission was also studied. The Reflectivity was measured over an incidence angle of 0deg-45deg. The Reflectivity of Thomas Keating Terahertz RAM at normal incidence was found to be -56 dB-the smallest of the studied materials. The Reflectivity of carpet material measured was also below -40 dB and it was found to be suitable for use as an absorber. The results are in line with those available from previous studies of Reflectivity and complement them with new materials, frequency, and angle information
