By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser be...By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.展开更多
A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given ...A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given in detail.A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment.The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested.The test results show that the focal length is in the range of 11.81-12 mm,which is close to the designed focal length of 15 mm.The reflectivity is almost above 0.56 within a bandwidth of 50 nm.At a distance of 11.86 mm,the light is focused to a round spot with the highest concentration,which is much smaller than the size of the incident beam.The FWHM of the reflected light beam decreases to 120 nm,and the intensity increases to 1.18.展开更多
We propose a 10-Gb/s Wavelength- Division-Multiplexed Passive Optical Network （WDM-PON） scheme with upstream transmi- ssion employing Reflective Semiconductor Op- tical Amplifier （RSOA） and Fibre Bragg Gra- ting ...We propose a 10-Gb/s Wavelength- Division-Multiplexed Passive Optical Network （WDM-PON） scheme with upstream transmi- ssion employing Reflective Semiconductor Op- tical Amplifier （RSOA） and Fibre Bragg Gra- ting （FBG） optical equaliser. Transmissions of 10-Gb/s non return-to-zero signals using a 1.2- GHz RSOA and FBG optical equaliser with different setups are demonstrated. Significant performance improvement and 40-kin standard single mode fibre transmission are achieved using FBG optical equaliser and Remotely Pum- ped Erbium-Doped Fibre Amplifier （RP-EDFA）, where they are used to equalise the output of the band-limited RSOA and amplify the seed light and upstream signal, respectively.展开更多
In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mo...In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mode resonance phe- nomenon are studied in detail. The reflection characteristics of high-reflectivity mirror in zeroth and -lst transmitted diffraction orders are quantitatively evaluated. It is found that the reflection bandwidth of high-reflectivity mirror in -lst transmitted diffraction order, which determines the final diffraction bandwidth of multilayer dielectric grating, is evidently compressed. Furthermore, it is demonstrated that the reducing of grating period is an effective approach to the elimination of guided mode resonance over a required broad band range both spectrally and angularly. In addition, the expressions for calculating the maximum period ensuring no guided mode resonance in the required bandwidth are derived. Finally, two high-efficiency pulse-compression gratings with broad-band are presented.展开更多
The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive...The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive single-mode telecommunication grade fibre. The fibre section with TFBG is then coupled to the evaluation fibre circuit with the cladding-core mode conversion element that provides the core re-coupling of the optical power injected by TFBG to the fibre cladding. The cladding-core mode conversion efficiency is sensitive to the acceleration generated fibre bending. It is shown that the sensitivity of the device depends on the rate of the main core reflection versus cladding ghost reflection induced by the grating. The analysis of the core reflection power coupling on the angle of the grating tilt and the analysis of the cladding ghost reflection power coupling on the angle of the grating tilt is presented and the optimal parameters of the tilt and refractive index modulation are derived. The presentation gives the experimental results of the TFBG sensor prepared according to the optimization process.展开更多
The large-aperture pulse compression grating(PCG) is a critical component in generating an ultra-high-intensity, ultra-short-pulse laser;however, the size of the PCG manufactured by transmission holographic exposure i...The large-aperture pulse compression grating(PCG) is a critical component in generating an ultra-high-intensity, ultra-short-pulse laser;however, the size of the PCG manufactured by transmission holographic exposure is limited to large-scale high-quality materials. The reflective method is a potential way for solving the size limitation, but there is still no successful precedent due to the lack of scientific specifications and advanced processing technology of exposure mirrors. In this paper, an analytical model is developed to clarify the specifications of components, and advanced processing technology is adopted to control the spatial frequency errors. Hereafter, we have successfully fabricated a multilayer dielectric grating of 200 mm × 150 mm by using an off-axis reflective exposure system with Φ300 mm. This demonstration proves that PCGs can be manufactured by using the reflection holographic exposure method and shows the potential for manufacturing the meter-level gratings used in 100 petawatt class high-power lasers.展开更多
High Q reflection filter using a gradient-index(GI) membrane with a grating surface is proposed. The thickness of GI membrane is very small comparing with the traditional multilayer reflection filter or the GI reflect...High Q reflection filter using a gradient-index(GI) membrane with a grating surface is proposed. The thickness of GI membrane is very small comparing with the traditional multilayer reflection filter or the GI reflection filter, and the GI membrane can also break the restriction of the resonant excitation condition of the conventional guided-mode resonance(GMR) filter. High Q filtering features can be maintained even on the high-index substrate. The grating thickness of the GI membrane filter can be used to select the resonance wavelength with different quality factors(QFs), the reflection peak is blue-shifted, and the QF is decreased from 554.4 to 207.8 as the grating thickness is increased from 50 nm to 150 nm. The gradient coefficient of the GI membrane filter can be used to tailor the number of the reflection channels. The resonant excitations of high order waveguide modes confined in the GI membrane are responsible for the high Q filtering properties with multiple channels.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474257 and 61605183
文摘By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274044,61574019 and 61020106007)the National Basic Research Program of China(Grant No.2010CB327600)+4 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130005130001)the Natural Science Foundation of Beijing,China(Grant No.4132069)the Key International Science and Technology Cooperation Project of China(Grant No.2011RR000100)the 111 Project of China(Grant No.B07005)the Program for Changjiang Scholars and Innovative Research Team in Universities of China(Grant No.IRT0609)
文摘A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given in detail.A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment.The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested.The test results show that the focal length is in the range of 11.81-12 mm,which is close to the designed focal length of 15 mm.The reflectivity is almost above 0.56 within a bandwidth of 50 nm.At a distance of 11.86 mm,the light is focused to a round spot with the highest concentration,which is much smaller than the size of the incident beam.The FWHM of the reflected light beam decreases to 120 nm,and the intensity increases to 1.18.
基金ACKNOWLEDGEMENT This work was supported by the National High Technology Research and Development Pro- gram of China under Grant No. 2011AA01A- 104 the National Natural Science Foundation of China under Grant No. 61302079 and the Fund of State Key Laboratory of Information Photonics and Optical Communications, Bei- jing University of Posts and Telecommunica- tions, China.
文摘We propose a 10-Gb/s Wavelength- Division-Multiplexed Passive Optical Network （WDM-PON） scheme with upstream transmi- ssion employing Reflective Semiconductor Op- tical Amplifier （RSOA） and Fibre Bragg Gra- ting （FBG） optical equaliser. Transmissions of 10-Gb/s non return-to-zero signals using a 1.2- GHz RSOA and FBG optical equaliser with different setups are demonstrated. Significant performance improvement and 40-kin standard single mode fibre transmission are achieved using FBG optical equaliser and Remotely Pum- ped Erbium-Doped Fibre Amplifier （RP-EDFA）, where they are used to equalise the output of the band-limited RSOA and amplify the seed light and upstream signal, respectively.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704079)the Natural Science Foundation of Shanghai Committee of Science and Technology, China (Grant No. 10ZR1433500)
文摘In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mode resonance phe- nomenon are studied in detail. The reflection characteristics of high-reflectivity mirror in zeroth and -lst transmitted diffraction orders are quantitatively evaluated. It is found that the reflection bandwidth of high-reflectivity mirror in -lst transmitted diffraction order, which determines the final diffraction bandwidth of multilayer dielectric grating, is evidently compressed. Furthermore, it is demonstrated that the reducing of grating period is an effective approach to the elimination of guided mode resonance over a required broad band range both spectrally and angularly. In addition, the expressions for calculating the maximum period ensuring no guided mode resonance in the required bandwidth are derived. Finally, two high-efficiency pulse-compression gratings with broad-band are presented.
文摘The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive single-mode telecommunication grade fibre. The fibre section with TFBG is then coupled to the evaluation fibre circuit with the cladding-core mode conversion element that provides the core re-coupling of the optical power injected by TFBG to the fibre cladding. The cladding-core mode conversion efficiency is sensitive to the acceleration generated fibre bending. It is shown that the sensitivity of the device depends on the rate of the main core reflection versus cladding ghost reflection induced by the grating. The analysis of the core reflection power coupling on the angle of the grating tilt and the analysis of the cladding ghost reflection power coupling on the angle of the grating tilt is presented and the optimal parameters of the tilt and refractive index modulation are derived. The presentation gives the experimental results of the TFBG sensor prepared according to the optimization process.
基金supported by the National Key R&D Program of China(2020YFA0714500)the National Natural Science Youth Foundation of China(62205352)+5 种基金the Member of Youth Innovation Promotion Association of the Chinese Academy of Sciencesthe International Partnership Program of the Chinese Academy of Sciences(181231KYSB20200040)the Chinese Academy of Sciences President’s International Fellowship Initiative(2023VMB0008)the Shanghai Sailing Program(20YF1454800)the Natural Science Foundation of Shanghai(21ZR1472000)the Shanghai Strategic Emerging Industry Development Special Fund(31011442501217020191D3101001)。
文摘The large-aperture pulse compression grating(PCG) is a critical component in generating an ultra-high-intensity, ultra-short-pulse laser;however, the size of the PCG manufactured by transmission holographic exposure is limited to large-scale high-quality materials. The reflective method is a potential way for solving the size limitation, but there is still no successful precedent due to the lack of scientific specifications and advanced processing technology of exposure mirrors. In this paper, an analytical model is developed to clarify the specifications of components, and advanced processing technology is adopted to control the spatial frequency errors. Hereafter, we have successfully fabricated a multilayer dielectric grating of 200 mm × 150 mm by using an off-axis reflective exposure system with Φ300 mm. This demonstration proves that PCGs can be manufactured by using the reflection holographic exposure method and shows the potential for manufacturing the meter-level gratings used in 100 petawatt class high-power lasers.
基金supported by the National Natural Science Foundation of China(No.11404143)the Fundamental Research Funds for the Central Universities(No.JUSRP115A15)the Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology(No.BM2014402)
文摘High Q reflection filter using a gradient-index(GI) membrane with a grating surface is proposed. The thickness of GI membrane is very small comparing with the traditional multilayer reflection filter or the GI reflection filter, and the GI membrane can also break the restriction of the resonant excitation condition of the conventional guided-mode resonance(GMR) filter. High Q filtering features can be maintained even on the high-index substrate. The grating thickness of the GI membrane filter can be used to select the resonance wavelength with different quality factors(QFs), the reflection peak is blue-shifted, and the QF is decreased from 554.4 to 207.8 as the grating thickness is increased from 50 nm to 150 nm. The gradient coefficient of the GI membrane filter can be used to tailor the number of the reflection channels. The resonant excitations of high order waveguide modes confined in the GI membrane are responsible for the high Q filtering properties with multiple channels.
