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
Effects of facet reflectivity of a laser diode on the performance of fiber Bragg grating semiconductor lasers are studied experimentally. Facet reflectivity of less than 10-4 is necessary to obtain stable oscillation ...Effects of facet reflectivity of a laser diode on the performance of fiber Bragg grating semiconductor lasers are studied experimentally. Facet reflectivity of less than 10-4 is necessary to obtain stable oscillation wavelength.展开更多
Modal analysis of the 1×3 highly efficient reflective triangular grating operating in the 800 nm wavelength under normal incidence for TE polarization is presented in this Letter.The rigorous coupled wave analysi...Modal analysis of the 1×3 highly efficient reflective triangular grating operating in the 800 nm wavelength under normal incidence for TE polarization is presented in this Letter.The rigorous coupled wave analysis and simulated annealing algorithm are used to design this beam splitter.The reflective grating consists of a highly reflective mirror and a transmission grating on the top.The mechanism of the reflective triangular grating is clarified by the simplified modal method.Then,gratings are fabricated by direct laser writing lithography.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
We report holographic fabrication of nanoporous distributed Bragg reflector(DBR) films with periodic nanoscale porosity via a single-prism conuration. The nanoporous DBR films result from the phase separation in a mat...We report holographic fabrication of nanoporous distributed Bragg reflector(DBR) films with periodic nanoscale porosity via a single-prism conuration. The nanoporous DBR films result from the phase separation in a material recipe, which consists of a polymerizable acrylate monomer and nonreactive volatile solvent. By changing the interfering angle of two laser beams, we achieve the nanoporous DBR films with highly reflective red,green, and blue colors. The reflection band of the nanoporous DBR films can be tuned by further filling different liquids into the pores inside the films, resulting in the color change accordingly. Experimental results show that such kinds of nanoporous DBR films could be potentially useful for many applications, such as color filters and refractive index sensors.展开更多
We demonstrated a 202 W Tm:YLF slab laser using a reflecting volume Bragg grating(VBG)as an output coupler at room temperature.Two kinds of active heat dissipation methods were used for the VBG to suppress the shift o...We demonstrated a 202 W Tm:YLF slab laser using a reflecting volume Bragg grating(VBG)as an output coupler at room temperature.Two kinds of active heat dissipation methods were used for the VBG to suppress the shift of wavelength caused by its increasing temperature.The maximum continuous wave(CW)output power of 202 W using the microchannel cooling was obtained under the total incident pump power of 553 W,the corresponding slope efficiency and optical-to-optical conversion efficiency were 39.7%and 36.5%,respectively.The central wavelength was 1908.5 nm with the linewidth(full width at half maximum)of 0.57 nm.Meanwhile,with the laser output increasing from 30 to 202 W,the total shift was about 1.0 nm,and the wavelength was limited to two water absorption lines near 1908 nm.The beam quality factors M;were measured to be 2.3 and 4.0 in x and y directions at 202 W.展开更多
We demonstrate a diode-pump Tm^（3＋）t-doped all-fiber laser operating at 1908 nm based on a master oscillator power amplifier（MOPA） configuration. In our work, 152 W of laser output power is generated by a total i...We demonstrate a diode-pump Tm^（3＋）t-doped all-fiber laser operating at 1908 nm based on a master oscillator power amplifier（MOPA） configuration. In our work, 152 W of laser output power is generated by a total incident pump power of 434 W at 790 nm, corresponding to the total optical efficiency of 35%. The laser wavelength is1908.29 nm. To the best of our knowledge, it is the highest output power reached around 1908 nm with such a narrow linewidth of 0.18 nm based on a MOPA configuration.展开更多
This Letter presents a method of an optical sensor for measuring wavelength shifts. The system consists of a diffraction grating and a total internal reflection heterodyne interferometer. As a heterodyne light beam st...This Letter presents a method of an optical sensor for measuring wavelength shifts. The system consists of a diffraction grating and a total internal reflection heterodyne interferometer. As a heterodyne light beam strikes a grating, the first-order diffraction beam is generated. The light penetrates into a total internal reflection prism at an angle larger than the critical angle. A wavelength variation will affect the diffractive angle of the first-order beam, thus inducing a phase difference variation of the light beam emerging from the total internal reflections inside the trapezoid prism. Both the experimental and theoretical results reveal that, for the first-order diffractive beam, the sensitivity and resolution levels are superior to 5°/nm and 0.006 nm, respectively, in the range of wavelength from 632 to 634 nm, and are superior to 3.1°/nm and 0.0095 nm in the range from 632 to 637 nm. For the theoretical simulation of the fourth-order diffractive beam, they are superior to 6.4 deg ∕nm and 0.0047 nm in the range from 632 to 637 nm.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.
文摘Effects of facet reflectivity of a laser diode on the performance of fiber Bragg grating semiconductor lasers are studied experimentally. Facet reflectivity of less than 10-4 is necessary to obtain stable oscillation wavelength.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61307064 and 61405214)the Ministry of Science and Technology of China(MOST)(No.2012YQ170004)
文摘Modal analysis of the 1×3 highly efficient reflective triangular grating operating in the 800 nm wavelength under normal incidence for TE polarization is presented in this Letter.The rigorous coupled wave analysis and simulated annealing algorithm are used to design this beam splitter.The reflective grating consists of a highly reflective mirror and a transmission grating on the top.The mechanism of the reflective triangular grating is clarified by the simplified modal method.Then,gratings are fabricated by direct laser writing lithography.
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.
基金supported in part by the National Natural Science Foundation of China (No. 61805113)Natural Science Foundation of Guangdong Province(Nos. 2017A030313034 and 2018A030310224)+4 种基金Shenzhen Science and Technology Innovation Commission (Nos.JCYJ20180305180635082JCYJ20170817111349280GJHZ20180928155207206)Open Fund of State Key Laboratory of Applied Optics (No. SKLAO-201904)Guangdong Innovative and Entrepreneurial Research Team Program (No. 2017ZT07C071)。
文摘We report holographic fabrication of nanoporous distributed Bragg reflector(DBR) films with periodic nanoscale porosity via a single-prism conuration. The nanoporous DBR films result from the phase separation in a material recipe, which consists of a polymerizable acrylate monomer and nonreactive volatile solvent. By changing the interfering angle of two laser beams, we achieve the nanoporous DBR films with highly reflective red,green, and blue colors. The reflection band of the nanoporous DBR films can be tuned by further filling different liquids into the pores inside the films, resulting in the color change accordingly. Experimental results show that such kinds of nanoporous DBR films could be potentially useful for many applications, such as color filters and refractive index sensors.
基金supported by the National Natural Science Foundation of China(No.U20A20214)。
文摘We demonstrated a 202 W Tm:YLF slab laser using a reflecting volume Bragg grating(VBG)as an output coupler at room temperature.Two kinds of active heat dissipation methods were used for the VBG to suppress the shift of wavelength caused by its increasing temperature.The maximum continuous wave(CW)output power of 202 W using the microchannel cooling was obtained under the total incident pump power of 553 W,the corresponding slope efficiency and optical-to-optical conversion efficiency were 39.7%and 36.5%,respectively.The central wavelength was 1908.5 nm with the linewidth(full width at half maximum)of 0.57 nm.Meanwhile,with the laser output increasing from 30 to 202 W,the total shift was about 1.0 nm,and the wavelength was limited to two water absorption lines near 1908 nm.The beam quality factors M;were measured to be 2.3 and 4.0 in x and y directions at 202 W.
基金supported by the National Natural Science Foundation of China(Nos.61308009 and61405047)the China Postdoctoral Science Foundation Funded Projects(Nos.2013M540288 and 2015M570290)+2 种基金the Fundamental Research Funds for the Central Universities Grant(Nos.HIT.NSRIF.2014044 and HIT.NSRIF.2015042)the Science Fund for Outstanding Youths of Heilongjiang Province(No.JQ201310)the Heilongjiang Postdoctoral Science Foundation Funded Projects(No.LBH-Z14085)
文摘We demonstrate a diode-pump Tm^（3＋）t-doped all-fiber laser operating at 1908 nm based on a master oscillator power amplifier（MOPA） configuration. In our work, 152 W of laser output power is generated by a total incident pump power of 434 W at 790 nm, corresponding to the total optical efficiency of 35%. The laser wavelength is1908.29 nm. To the best of our knowledge, it is the highest output power reached around 1908 nm with such a narrow linewidth of 0.18 nm based on a MOPA configuration.
文摘This Letter presents a method of an optical sensor for measuring wavelength shifts. The system consists of a diffraction grating and a total internal reflection heterodyne interferometer. As a heterodyne light beam strikes a grating, the first-order diffraction beam is generated. The light penetrates into a total internal reflection prism at an angle larger than the critical angle. A wavelength variation will affect the diffractive angle of the first-order beam, thus inducing a phase difference variation of the light beam emerging from the total internal reflections inside the trapezoid prism. Both the experimental and theoretical results reveal that, for the first-order diffractive beam, the sensitivity and resolution levels are superior to 5°/nm and 0.006 nm, respectively, in the range of wavelength from 632 to 634 nm, and are superior to 3.1°/nm and 0.0095 nm in the range from 632 to 637 nm. For the theoretical simulation of the fourth-order diffractive beam, they are superior to 6.4 deg ∕nm and 0.0047 nm in the range from 632 to 637 nm.
