A broadband power amplifier is required to cover the full range of cellular frequency band—from 700 MHz to 2600 MHz—in a base station that supports multiple frequency bands simultaneously. Conventional laterally dif...A broadband power amplifier is required to cover the full range of cellular frequency band—from 700 MHz to 2600 MHz—in a base station that supports multiple frequency bands simultaneously. Conventional laterally diffused metal oxide semiconductor (LDMOS) transistors support narrow band applications up to 3 GHz. However, they cannot operate beyond 1 GHz in broadband applications. GaN transistors have much higher power density and operational frequency compared with LDMOS. Therefore, they are ideal for broadband amplifiers that support multiple bands. Theories for designing broadband amplifiers are introduced in this article, and a 500-2500 MHz 60 W GaN amplifier is discussed.展开更多
A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was bas...A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3+ and Yb^3+ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3+ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3+/Yb^3+ co-doped tellurite glass as amplifier material were concluded.展开更多
To obtain a stable amplified spontaneous emission(ASE) source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperature...To obtain a stable amplified spontaneous emission(ASE) source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperatures.We optimize the structure of the ASE source to flatten the ASE spectrum, and study the output characteristics in terms of output power and optical spectrum under different pump powers. Then the performance of the ASE source is investigated in the temperature range from-18.9°C to 50°C. A stable-power and flat-spectrum ASE source can be obtained by structural optimization and pump control.展开更多
Some intra-4/-configurational transitions of lanthanide, of which radiative emissions cover in wavelengths the optical communication window of the currently available OH-free silica-based line fibers, are discussed in...Some intra-4/-configurational transitions of lanthanide, of which radiative emissions cover in wavelengths the optical communication window of the currently available OH-free silica-based line fibers, are discussed in terms of relationship between their emission properties and host fiber materials.展开更多
Rhodamine 6G-doped step-index polymer optical fiber is fabricated. The characteristics of the amplification of rhodamine 6G-doped step-index polymer optical fiber amplifier have been studied. The high-gain optical amp...Rhodamine 6G-doped step-index polymer optical fiber is fabricated. The characteristics of the amplification of rhodamine 6G-doped step-index polymer optical fiber amplifier have been studied. The high-gain optical amplification with a tunable wavelength range from 585 to 613 nm is obtained in a step-index polymer optical fiber doped with rhodamine 6G at 10-ppm level, which can be used for broadband amplifiers and tunable lasers.展开更多
We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier.The large mode area of the PCF and the ...We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier.The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient.Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz.A strong saturation effect is observed,which is attributed to pump pulse absorption;a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm.A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy.展开更多
A novel broadband power amplifier fabricated in 0.13 m SiGe HBT technology is realized.The pseudo-differential structure is proposed to avoid the influence of the bonding wire due to the AC virtual ground created at t...A novel broadband power amplifier fabricated in 0.13 m SiGe HBT technology is realized.The pseudo-differential structure is proposed to avoid the influence of the bonding wire due to the AC virtual ground created at the common emitter node.A compensated matching technique is adopted in interstage matching to expand bandwidth.A multi-stage broadband matching technique is used in an input/output matching network to offer broadband impedance matching,which ensures maximum power transfer.An adaptive bias circuit could improve linearity and efficiency in wide output power level.With 2.5 V power supply,the measured results achieve 96% 3-dB bandwidth(517-1470 MHz),27.2 dB power gain,26.9 dBm maximum output power,19.7 dBm output 1 dB compression point,and 26.7% power added efficiency.展开更多
A novel design of high-efficiency broadband power amplifier (BPA) with the low-pass bias networkto enhance the efficiency and output power is presented in this paper. Compared with other bias networks, the proposed ...A novel design of high-efficiency broadband power amplifier (BPA) with the low-pass bias networkto enhance the efficiency and output power is presented in this paper. Compared with other bias networks, the proposed low-pass bias network shows a smaller baseband impedance, which can reduce the electrical memory effect. While it provides a larger radio frequency (RF) impedance, which can prevent the leakage of the output power from bias network. A BPA with the proposed bias network is designed using commercial GaN device Cree40025F. The designed BPA shows a fractional bandwidth of 40%, from 1.8 GHz to 2.7 GHz. The measured results exhibit 73.9 % drain efficiency (DE) value with output power of 43.5 dBm at 2.7 GHz, which appears an enhancement of 9.5% and 2.5 dBm comparing with that adopts LC bias network.展开更多
We propose a broadband fiber optic parametric amplifier(FOPA) based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength(ZDW) by using a selective liquid infiltration technique.The...We propose a broadband fiber optic parametric amplifier(FOPA) based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength(ZDW) by using a selective liquid infiltration technique.The amplifier gain and bandwidth is investigated for a variety of fiber lengths, pump power, and operating wavelengths. It is observed that sufficient peak gains and broader bandwidths can be achieved with a small negative anomalous dispersion(β2≤ 0) and a positive value of the 4th-order dispersion parameter(t β4)around the pump. We can optimize an FOPA with a bandwidth of more than 220 nm around the communications wavelength.展开更多
Emission spectra and fluorescence lifetime of Er3+ in Yb3+/Er3+-codoped tungsten-tellurite glasses were measured. Effects of Yb3+concentration on 1.5μm emission intensity and bandwidth of Er3+ were investigated and a...Emission spectra and fluorescence lifetime of Er3+ in Yb3+/Er3+-codoped tungsten-tellurite glasses were measured. Effects of Yb3+concentration on 1.5μm emission intensity and bandwidth of Er3+ were investigated and a FWHM of 81 nm was demonstrated.展开更多
WO_3 oxides with relatively high phonon energy and different concentrations were introduced into the Nd^(3+)-doped tellurite-based glasses of Te O_2-Zn O-Na_2 O to improve the 1.32 μm band fluorescence emission. The ...WO_3 oxides with relatively high phonon energy and different concentrations were introduced into the Nd^(3+)-doped tellurite-based glasses of Te O_2-Zn O-Na_2 O to improve the 1.32 μm band fluorescence emission. The absorption spectra,Raman spectra,1.32 μm band fluorescence spectra and differential scanning calorimeter(DSC) curves were measured,together with the Judd-Ofelt intensity parameters,stimulated emission and gain parameters were calculated to evaluate the effects of WO_3 amount on the glass structure and spectroscopic properties of 1.32 μm band fluorescence. It is shown that the introduction of an appropriate amount of WO_3 oxide can effectively improve the 1.32 μm band fluorescence intensity through the enhanced multi-phonon relaxation(MPR) processes between the excited levels of Nd^(3+). The results indicate that the prepared Nd^(3+)-doped tellurite glass with an appropriate amount of WO_3 oxide is a potential gain medium applied for the O-band broad and high-gain fiber amplifier.展开更多
We report on hundred watts range ytterbium-doped all-fiber laser assembly based on the master oscillator power amplifier structure. It consisted of an oscillator and an amplifier with all-fiber components. And fiber f...We report on hundred watts range ytterbium-doped all-fiber laser assembly based on the master oscillator power amplifier structure. It consisted of an oscillator and an amplifier with all-fiber components. And fiber fusion splice made the laser be an integrated fiber system. It generated up to 175.5 W of continuous- wave (CW) output power at 1085 nm with more than 75% extraction efficiency in the amplifier when the total coupled pump power into the double clad fiber was 270 W.展开更多
A scheme for photonic generation of ultra-wideband (UWB) pulses using a semiconductor optical amplifier (SOA) and an electro-absorber (EA) in parallel is proposed and numerically demonstrated. By adjusting the t...A scheme for photonic generation of ultra-wideband (UWB) pulses using a semiconductor optical amplifier (SOA) and an electro-absorber (EA) in parallel is proposed and numerically demonstrated. By adjusting the time delay between two pump signals incident into the SOA and the EA, we can obtain monocycle pulses with reversed polarities and different bandwidths. The proposed method is flexible in pulse shaping and easy in practical optimization.展开更多
Bi-doped SiO2-Al2O3-GeO2 fiber preforms are prepared by modified chemical vapor deposition (MCVD) and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investigated, a...Bi-doped SiO2-Al2O3-GeO2 fiber preforms are prepared by modified chemical vapor deposition (MCVD) and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investigated, and a distinct difference in emission between the two is observed. Under 808-nm excitation, an ultra-broad near-infrared (NIR) emission with full-width at half-maximum (FWHM) of 495 nm is observed in the Bi-doped fiber. This observation, to our knowledge, is the first in this field. The NIR emission consists of two bands, which may be ascribed to the Bi0 and Bi+ species, respectively. This Bi-doDed fiber is promising for broadband or)tical amolification and widely tunable laser.展开更多
We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier (OPA) source. The generation of h...We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier (OPA) source. The generation of high-order harmonic continuum with the cut-off photon energy up to 110 eV is observed by tuning the chirp of the 800-nm laser pulse which pumps OPA source. The generation of harmonic continuum is understood in terms of the two-hump structure of the OPA output spectrum and the optimal relative phase of the two humps. The demonstrated scheme is of importance for the generation of extreme ultraviolet (XUV) continuum at higher photon energy region.展开更多
文摘A broadband power amplifier is required to cover the full range of cellular frequency band—from 700 MHz to 2600 MHz—in a base station that supports multiple frequency bands simultaneously. Conventional laterally diffused metal oxide semiconductor (LDMOS) transistors support narrow band applications up to 3 GHz. However, they cannot operate beyond 1 GHz in broadband applications. GaN transistors have much higher power density and operational frequency compared with LDMOS. Therefore, they are ideal for broadband amplifiers that support multiple bands. Theories for designing broadband amplifiers are introduced in this article, and a 500-2500 MHz 60 W GaN amplifier is discussed.
基金supported by the Natural Science Foundation of Zhejiang Provience, China (2006C21082)National Natural Science Foundation of China (60677015)+1 种基金Foundation of Ningbo University (XR0710018)sponsored by KC Wong Magna Fund in NingBo University
文摘A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3+ and Yb^3+ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3+ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3+/Yb^3+ co-doped tellurite glass as amplifier material were concluded.
基金Supported by the National Natural Science Foundation of China under Grant No 11504320
文摘To obtain a stable amplified spontaneous emission(ASE) source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperatures.We optimize the structure of the ASE source to flatten the ASE spectrum, and study the output characteristics in terms of output power and optical spectrum under different pump powers. Then the performance of the ASE source is investigated in the temperature range from-18.9°C to 50°C. A stable-power and flat-spectrum ASE source can be obtained by structural optimization and pump control.
文摘Some intra-4/-configurational transitions of lanthanide, of which radiative emissions cover in wavelengths the optical communication window of the currently available OH-free silica-based line fibers, are discussed in terms of relationship between their emission properties and host fiber materials.
基金This work was supported by the National Natural Science Foundation of China (No.90201013and90201016),the Fujian Natural Science Foundation of China (No.A0110012),and the Fyjian Educational Department Foundation of China (NoJA02169).
文摘Rhodamine 6G-doped step-index polymer optical fiber is fabricated. The characteristics of the amplification of rhodamine 6G-doped step-index polymer optical fiber amplifier have been studied. The high-gain optical amplification with a tunable wavelength range from 585 to 613 nm is obtained in a step-index polymer optical fiber doped with rhodamine 6G at 10-ppm level, which can be used for broadband amplifiers and tunable lasers.
基金supported partly by the National Natural Science Foundation of China (Nos. 61077083, 61027013,61078028,and 60838004)the National Basic Research Program of China (Nos. 2007CB310408, 2010CB327604,and 2011CB808101)+3 种基金the Research Fund for the Doctoral Program of Higher Education (No. 200800560026)the Foundation for the Author of National Excellent Doctoral Dissertation of China (No. 2007B34)the 111 Project (No. B07014)the Program for New Century Talents in University (No. NCET-07-0597)
文摘We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier.The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient.Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz.A strong saturation effect is observed,which is attributed to pump pulse absorption;a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm.A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy.
文摘A novel broadband power amplifier fabricated in 0.13 m SiGe HBT technology is realized.The pseudo-differential structure is proposed to avoid the influence of the bonding wire due to the AC virtual ground created at the common emitter node.A compensated matching technique is adopted in interstage matching to expand bandwidth.A multi-stage broadband matching technique is used in an input/output matching network to offer broadband impedance matching,which ensures maximum power transfer.An adaptive bias circuit could improve linearity and efficiency in wide output power level.With 2.5 V power supply,the measured results achieve 96% 3-dB bandwidth(517-1470 MHz),27.2 dB power gain,26.9 dBm maximum output power,19.7 dBm output 1 dB compression point,and 26.7% power added efficiency.
基金supported by National Basic Research Program of China(973 Program)(2014CB339900)National Natural Science Foundation of China(61201025)National Natural Science Foundation of China for the Major Equipment Development(61327806)
文摘A novel design of high-efficiency broadband power amplifier (BPA) with the low-pass bias networkto enhance the efficiency and output power is presented in this paper. Compared with other bias networks, the proposed low-pass bias network shows a smaller baseband impedance, which can reduce the electrical memory effect. While it provides a larger radio frequency (RF) impedance, which can prevent the leakage of the output power from bias network. A BPA with the proposed bias network is designed using commercial GaN device Cree40025F. The designed BPA shows a fractional bandwidth of 40%, from 1.8 GHz to 2.7 GHz. The measured results exhibit 73.9 % drain efficiency (DE) value with output power of 43.5 dBm at 2.7 GHz, which appears an enhancement of 9.5% and 2.5 dBm comparing with that adopts LC bias network.
基金the Science&Engineering ResearchBoard(SERB),New Delhi,India,for the NPDF fellowship(File No.PDF/2016/001827)support received from NationalInstitute of Science Education and Research(NISER),Department of Atomic Energy(DAE),Government of India
文摘We propose a broadband fiber optic parametric amplifier(FOPA) based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength(ZDW) by using a selective liquid infiltration technique.The amplifier gain and bandwidth is investigated for a variety of fiber lengths, pump power, and operating wavelengths. It is observed that sufficient peak gains and broader bandwidths can be achieved with a small negative anomalous dispersion(β2≤ 0) and a positive value of the 4th-order dispersion parameter(t β4)around the pump. We can optimize an FOPA with a bandwidth of more than 220 nm around the communications wavelength.
文摘Emission spectra and fluorescence lifetime of Er3+ in Yb3+/Er3+-codoped tungsten-tellurite glasses were measured. Effects of Yb3+concentration on 1.5μm emission intensity and bandwidth of Er3+ were investigated and a FWHM of 81 nm was demonstrated.
基金supported by the National Natural Science Foundation of China(No.61178063)the Natural Science Foundation of Ningbo City(No.2016A610061)+1 种基金the K.C.Wong Magna FundHu Lan Outstanding Doctoral Fund in Ningbo University
文摘WO_3 oxides with relatively high phonon energy and different concentrations were introduced into the Nd^(3+)-doped tellurite-based glasses of Te O_2-Zn O-Na_2 O to improve the 1.32 μm band fluorescence emission. The absorption spectra,Raman spectra,1.32 μm band fluorescence spectra and differential scanning calorimeter(DSC) curves were measured,together with the Judd-Ofelt intensity parameters,stimulated emission and gain parameters were calculated to evaluate the effects of WO_3 amount on the glass structure and spectroscopic properties of 1.32 μm band fluorescence. It is shown that the introduction of an appropriate amount of WO_3 oxide can effectively improve the 1.32 μm band fluorescence intensity through the enhanced multi-phonon relaxation(MPR) processes between the excited levels of Nd^(3+). The results indicate that the prepared Nd^(3+)-doped tellurite glass with an appropriate amount of WO_3 oxide is a potential gain medium applied for the O-band broad and high-gain fiber amplifier.
文摘We report on hundred watts range ytterbium-doped all-fiber laser assembly based on the master oscillator power amplifier structure. It consisted of an oscillator and an amplifier with all-fiber components. And fiber fusion splice made the laser be an integrated fiber system. It generated up to 175.5 W of continuous- wave (CW) output power at 1085 nm with more than 75% extraction efficiency in the amplifier when the total coupled pump power into the double clad fiber was 270 W.
基金supported by the National "863"program of China (Nos. 2009AA01Z256, 2009AA01Z253,and 2008AA01A331)the National Natural Science Foundation of China (Nos. 60736036, 60702006, 60837004,60736002, and 60932004)+3 种基金the MOST program (No.2008DFA11670)the Project Funded by the State Key Lab of AOCSN, China, the Excellent Doctoral Innovation Project funded by Beijing University of Posts and Telecommunications (No. CX201012)the Special-ized Research Fund for the Doctoral Program of Higher Education (No. 200800131007)the Fundamental Research Funds for the Central Universities
文摘A scheme for photonic generation of ultra-wideband (UWB) pulses using a semiconductor optical amplifier (SOA) and an electro-absorber (EA) in parallel is proposed and numerically demonstrated. By adjusting the time delay between two pump signals incident into the SOA and the EA, we can obtain monocycle pulses with reversed polarities and different bandwidths. The proposed method is flexible in pulse shaping and easy in practical optimization.
文摘Bi-doped SiO2-Al2O3-GeO2 fiber preforms are prepared by modified chemical vapor deposition (MCVD) and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investigated, and a distinct difference in emission between the two is observed. Under 808-nm excitation, an ultra-broad near-infrared (NIR) emission with full-width at half-maximum (FWHM) of 495 nm is observed in the Bi-doped fiber. This observation, to our knowledge, is the first in this field. The NIR emission consists of two bands, which may be ascribed to the Bi0 and Bi+ species, respectively. This Bi-doDed fiber is promising for broadband or)tical amolification and widely tunable laser.
基金supported by the National Natural Science Foundation of China(Nos.11127901,60921004,11134010,11222439,and 61108012)the National"973"Program of China(No.2011CB808103)+1 种基金the Postdoctoral Science Foundation of China(Nos.2012T50420and 2012M520941)the Postdoctoral Scientific Research Program of Shanghai(No.12R21416600)
文摘We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier (OPA) source. The generation of high-order harmonic continuum with the cut-off photon energy up to 110 eV is observed by tuning the chirp of the 800-nm laser pulse which pumps OPA source. The generation of harmonic continuum is understood in terms of the two-hump structure of the OPA output spectrum and the optimal relative phase of the two humps. The demonstrated scheme is of importance for the generation of extreme ultraviolet (XUV) continuum at higher photon energy region.