Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microf...Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane (PDMS) to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.展开更多
In this paper, the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber (TDF) laser is investigated. The analytical formulations of pump energy threshold, peak power extraction effi...In this paper, the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber (TDF) laser is investigated. The analytical formulations of pump energy threshold, peak power extraction efficiency, and pulse extraction efficiency are derived through analyzing the interaction process between the pump pulse and the laser pulse. They are useful for understanding, designing, and optimizing the in-band pumped TDF lasers in a 1.9 μm-2.1 μm wavelength region. The experiment with an all-fiber gain-switched TDF laser pumped by a 1.558-μm pulse amplifier is conducted, and our experimental results show good agreement with theoretical analysis.展开更多
The steady-state gain distribution in cladding pumped thulium-doped fiber laser(TDFL) is analytically and numerically solved based on the rate equations including loss coefficients and cross relaxation effect. With ...The steady-state gain distribution in cladding pumped thulium-doped fiber laser(TDFL) is analytically and numerically solved based on the rate equations including loss coefficients and cross relaxation effect. With the gain curve, a problem, which is named optical feedback inhibition(OFI) and always occurs in tandem TDFL-Ho:YAG laser system, is analyzed quantitatively. The actual characteristics of output spectra and power basically prove the conclusion of theoretical analysis. Then a simple mirror-deflected L-shaped cavity is employed to restrain the external feedback and simplify the structure of fiber-bulk Ho:YAG laser. Finally, 25 W of 2097-nm laser power and 51.2% of optical-to-optical conversion efficiency are obtained, and the beam quality factor is less than 1.43 obtained by knife-edge method.展开更多
In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficienc...In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.展开更多
A high-power all polarization-maintaining(PM) chirped pulse amplification(CPA) system operating in the 2.0 μm range is experimentally demonstrated.Large mode area(LMA) thulium-doped fiber(TDF) with a core/cladding di...A high-power all polarization-maintaining(PM) chirped pulse amplification(CPA) system operating in the 2.0 μm range is experimentally demonstrated.Large mode area(LMA) thulium-doped fiber(TDF) with a core/cladding diameter of25/400 μm is employed to construct the main amplifier.Through dedicated coiling and cooling of the LMA-TDF to manage the loss of the higher order mode and thermal effect,a maximum average power of 314 W with a slope efficiency of 52% and polarization extinction ratio of 20 dB is realized.The pulse duration is compressed to 283 fs with a grating pair,corresponding to a calculated peak power of 10.8 MW,considering the compression efficiency of 88% and the estimated Strehl ratio of 89%.Moreover,through characterizing the noise properties of the laser,an integrated relative intensity noise of 0.11% at 100 Hz-1 MHz is obtained at the maximum output power,whereas the laser timing jitter is degraded by the final amplifier from 318 to 410 fs at an integration frequency of 5 kHz to 1 MHz,owing to the self-phase modulation effect-induced spectrum broadening.The root-mean-square of long-term power fluctuation is tested to be0.6%,verifying the good stability of the laser operation.To the best of our knowledge,this is the highest average power of an ultrafast laser realized from an all-PM-fiber TDF-CPA system ever reported.展开更多
A mode-locked thulium-doped fiber laser(TDFL) based on nonlinear polarization rotation(NPR) with different net anomalous dispersion is demonstrated. When the cavity dispersion is-1.425 ps^2, the noise-like(NL) pulse w...A mode-locked thulium-doped fiber laser(TDFL) based on nonlinear polarization rotation(NPR) with different net anomalous dispersion is demonstrated. When the cavity dispersion is-1.425 ps^2, the noise-like(NL) pulse with coherence spike width of 406 fs and pulse energy of 12.342 nJ is generated at a center wavelength of 2003.2 nm with 3 dB spectral bandwidth of 23.20 nm. In the experimental period of 400 min, the 3 dB spectral bandwidth variation, the output power fluctuation, and the central wavelength shift are less than 0.06 nm, 0.04 d B, and0.4 nm, respectively, indicating that the NPR-based TDFL operating in the NL regime holds good long-term stability.展开更多
We experimentally demonstrated a type of tunable and switchable harmonic h-shaped pulse generation in a thulium-doped fiber(TDF) laser passively mode locked by using an ultralong nonlinear optical loop mirror.The tota...We experimentally demonstrated a type of tunable and switchable harmonic h-shaped pulse generation in a thulium-doped fiber(TDF) laser passively mode locked by using an ultralong nonlinear optical loop mirror.The total cavity length was ~3.03 km, the longest ever built for a TDF laser to our best knowledge, which resulted in an ultralarge anomalous dispersion over -200 ps^2 around the emission wavelength. The produced h-shaped pulse can operate either in a fundamental or in a high-order harmonic mode-locking(HML) state depending on pump power and intra-cavity polarization state(PS). The pulse duration, no matter of the operation state, was tunable with pump power. However, pulse breaking and self-organizing occurred, resulting in high-order HML,when the pump power increased above a threshold. At a fixed pump power, the order of HML was switchable from one to another by manipulating the PS. Switching from the 8 th up to the 48 th order of HML was achieved with a fixed pump power of ~4.15 W. Our results revealed the detailed evolution and switching characteristics of the HML and individual pulse envelope with respect to both the pump power and PS. We have also discussed in detail the mechanisms of both the h-shaped pulse generation and the switching of its HML. This contribution would be helpful for further in-depth study on the underlying dynamics of long-duration particular-envelope pulses with ultralarge anomalous dispersion and ultralong roundtrip time.展开更多
We demonstrate a 2080 nm long-wavelength mode-locked thulium(Tm)-doped fiber laser operating in the dissipative soliton resonance(DSR) regime. The compact all-fiber dumbbell-shaped laser is simply constructed by a 50/...We demonstrate a 2080 nm long-wavelength mode-locked thulium(Tm)-doped fiber laser operating in the dissipative soliton resonance(DSR) regime. The compact all-fiber dumbbell-shaped laser is simply constructed by a 50/50 fiber loop mirror(FLM), a 10/90 FLM, and a piece of large-gain Tm-doped double-clad fiber pumped by a 793 nm laser diode. The 10/90 FLM is not only used as an output mirror, but also acts as a periodical saturable absorber for initiating DSR mode locking. The stable DSR pulses are generated at the center wavelength as long as 2080.4 nm, and the pulse duration can be tunable from 780 to 3240 ps as the pump power is increased. The maximum average output power is 1.27 W, corresponding to a pulse energy of 290 nJ and a nearly constant peak power of 93 W. This is, to the best of our knowledge, the longest wavelength for DSR operation in a mode-locked fiber laser.展开更多
We report the first demonstration of a unidirectional,isolator-free 2-μm thulium-doped fiber(TDF)laser,relying on the properties of the theta cavity(ring resonator with S-shaped feedback).The core pumped theta cavity...We report the first demonstration of a unidirectional,isolator-free 2-μm thulium-doped fiber(TDF)laser,relying on the properties of the theta cavity(ring resonator with S-shaped feedback).The core pumped theta cavity TDF laser provides sub-Watt output power with a slope efficiency of 25%,a 2 dB flat tuning range of 1900–2050 nm,and a linewidth of 0.2 nm,and achieves the extinction ratio of 18–25 dB(depending on the feedback value)between the favored and suppressed lasing directions.It is shown that these characteristics are competitive with,if not superior to,those of conventional ring cavities.The simulation results of the linear and Kerr-nonlinear theta cavities are also presented,explaining certain unexpected features of the laser behavior and establishing the importance of the doped fiber nonlinearity on the spectral shaping of the emitted signal.展开更多
We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber(TDF) laser based on all-fiber Mach–Zehnder interferometer(MZI) at 1.9 mm. Here a segment of 4 m single-mode TDF is pumped by 1568 n...We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber(TDF) laser based on all-fiber Mach–Zehnder interferometer(MZI) at 1.9 mm. Here a segment of 4 m single-mode TDF is pumped by 1568 nm fiber laser for 2 mm band optical gain. The MZI includes two cascaded 3 d B coupler. A segment of 3.5 m long un-pumped polarization-maintaining TDF and polarization controller(PC) are joined in the ring cavity to suppress the mode competition. Multi-wavelength lasers at 1.9 mm with wavelength number from one to four are obtained by adjusting the PC and the stability of output power of multi-wavelength fiber laser is analyzed.展开更多
In this paper,we report a coherent beam combining(CBC)system that involves two thulium-doped all-polarization maintaining(PM)fiber chirped pulse amplifiers.Through phase-locking the two channels via a fiber stretcher ...In this paper,we report a coherent beam combining(CBC)system that involves two thulium-doped all-polarization maintaining(PM)fiber chirped pulse amplifiers.Through phase-locking the two channels via a fiber stretcher by using the stochastic parallel gradient descent(SPGD)algorithm,a maximum average power of 265 W is obtained,with a CBC efficiency of 81%and a residual phase error of λ/17.After de-chirping by a pair of diffraction gratings,the duration of the combined laser pulse is compressed to 690 fs.Taking into account the compression efficiency of 90%and the main peak energy proportion of 91%,the corresponding peak power is calculated to be 4 MW.The laser noise characteristics before and after CBC are examined,and the results indicate that the CBC would degrade the low frequency relative intensity noise(RIN),of which the integration is 1.74%in[100 Hz,2 MHz]at the maximum combined output power.In addition,the effects of the nonlinear spectrum broadening during chirped pulse amplification on the CBC efficiency are also investigated,showing that a higher extent of pulse stretching is effective in alleviating the spectrum broadening and realizing a higher output power with decent combining efficiency.展开更多
Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an ef...Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an efficient laser source,it was challenging to image the water content in the deep tissue with micron-level spatial resolution.To address this problem,we develop a high-power hybrid optical parametrically-oscillating emitter(HOPE)at 1930 nm,at which the vibrational absorption peak of the O-H bond locates.The maximum pulse energy is over 1.74μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns.We employ this laser source in the optical-resolution photoacoustic microscopy(OR-PAM)system to image the water content in the phantom and the biological tissue in vitro.Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution,deep penetration depth,improved sensitivity,and suppressed artifact signal of the lipid.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304409 and 61705028)the Natural Science Foundation of Chongqing City,China(Grant Nos.csct2013jcyjA4004 and cstc2017jcyjA0893)+1 种基金the Scientific and Technological Research Program of Chongqing Municipal Education Commission,China(Grant No.KJ1500422)the Postgraduate Research Innovation Foundation of Chongqing City,China(Grant No.CYS17240)
文摘Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane (PDMS) to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60878011 and 61078008)the Program for New Century ExcellentTalents in University,China (Grant No. NCET-10-0067)
文摘In this paper, the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber (TDF) laser is investigated. The analytical formulations of pump energy threshold, peak power extraction efficiency, and pulse extraction efficiency are derived through analyzing the interaction process between the pump pulse and the laser pulse. They are useful for understanding, designing, and optimizing the in-band pumped TDF lasers in a 1.9 μm-2.1 μm wavelength region. The experiment with an all-fiber gain-switched TDF laser pumped by a 1.558-μm pulse amplifier is conducted, and our experimental results show good agreement with theoretical analysis.
基金Project supported by the National Natural Science Foundation of China(Grant No.61275146)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120002110066)the Special Program of the Co-construction with Beijing Municipal Government of China(Grant No.20121000302)
文摘The steady-state gain distribution in cladding pumped thulium-doped fiber laser(TDFL) is analytically and numerically solved based on the rate equations including loss coefficients and cross relaxation effect. With the gain curve, a problem, which is named optical feedback inhibition(OFI) and always occurs in tandem TDFL-Ho:YAG laser system, is analyzed quantitatively. The actual characteristics of output spectra and power basically prove the conclusion of theoretical analysis. Then a simple mirror-deflected L-shaped cavity is employed to restrain the external feedback and simplify the structure of fiber-bulk Ho:YAG laser. Finally, 25 W of 2097-nm laser power and 51.2% of optical-to-optical conversion efficiency are obtained, and the beam quality factor is less than 1.43 obtained by knife-edge method.
文摘In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.
基金supported by the Director Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2020ZR02)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.QL20210015).
文摘A high-power all polarization-maintaining(PM) chirped pulse amplification(CPA) system operating in the 2.0 μm range is experimentally demonstrated.Large mode area(LMA) thulium-doped fiber(TDF) with a core/cladding diameter of25/400 μm is employed to construct the main amplifier.Through dedicated coiling and cooling of the LMA-TDF to manage the loss of the higher order mode and thermal effect,a maximum average power of 314 W with a slope efficiency of 52% and polarization extinction ratio of 20 dB is realized.The pulse duration is compressed to 283 fs with a grating pair,corresponding to a calculated peak power of 10.8 MW,considering the compression efficiency of 88% and the estimated Strehl ratio of 89%.Moreover,through characterizing the noise properties of the laser,an integrated relative intensity noise of 0.11% at 100 Hz-1 MHz is obtained at the maximum output power,whereas the laser timing jitter is degraded by the final amplifier from 318 to 410 fs at an integration frequency of 5 kHz to 1 MHz,owing to the self-phase modulation effect-induced spectrum broadening.The root-mean-square of long-term power fluctuation is tested to be0.6%,verifying the good stability of the laser operation.To the best of our knowledge,this is the highest average power of an ultrafast laser realized from an all-PM-fiber TDF-CPA system ever reported.
基金Fundamental Research Funds for the Central Universities(2016YJS034)
文摘A mode-locked thulium-doped fiber laser(TDFL) based on nonlinear polarization rotation(NPR) with different net anomalous dispersion is demonstrated. When the cavity dispersion is-1.425 ps^2, the noise-like(NL) pulse with coherence spike width of 406 fs and pulse energy of 12.342 nJ is generated at a center wavelength of 2003.2 nm with 3 dB spectral bandwidth of 23.20 nm. In the experimental period of 400 min, the 3 dB spectral bandwidth variation, the output power fluctuation, and the central wavelength shift are less than 0.06 nm, 0.04 d B, and0.4 nm, respectively, indicating that the NPR-based TDFL operating in the NL regime holds good long-term stability.
基金Natural Science Foundation of Jiangsu Province,China(BK20170243)National Natural Science Foundation of China(NSFC)(61705094,11674133,11711530208,61575089)+5 种基金Key Research Program of Natural Science of Jiangsu Higher Education Institutions(17KJA416004)Royal Society(IE161214)Protocol of the 37th Session of China-Poland Scientific and Technological Cooperation Committee(37-17)H2020 Marie Sk?odowska-Curie Actions(MSCA)(790666)Jiangsu Overseas Visiting Scholar Program for University Prominent Young and Middle-aged Teachers and PresidentsPriority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘We experimentally demonstrated a type of tunable and switchable harmonic h-shaped pulse generation in a thulium-doped fiber(TDF) laser passively mode locked by using an ultralong nonlinear optical loop mirror.The total cavity length was ~3.03 km, the longest ever built for a TDF laser to our best knowledge, which resulted in an ultralarge anomalous dispersion over -200 ps^2 around the emission wavelength. The produced h-shaped pulse can operate either in a fundamental or in a high-order harmonic mode-locking(HML) state depending on pump power and intra-cavity polarization state(PS). The pulse duration, no matter of the operation state, was tunable with pump power. However, pulse breaking and self-organizing occurred, resulting in high-order HML,when the pump power increased above a threshold. At a fixed pump power, the order of HML was switchable from one to another by manipulating the PS. Switching from the 8 th up to the 48 th order of HML was achieved with a fixed pump power of ~4.15 W. Our results revealed the detailed evolution and switching characteristics of the HML and individual pulse envelope with respect to both the pump power and PS. We have also discussed in detail the mechanisms of both the h-shaped pulse generation and the switching of its HML. This contribution would be helpful for further in-depth study on the underlying dynamics of long-duration particular-envelope pulses with ultralarge anomalous dispersion and ultralong roundtrip time.
基金supported in part by the Research Fund of State Grid Corporation of China(No.52183516000B)the National Natural Science Foundation of China(No.61475129)+1 种基金the Natural Science Foundation of Fujian Province(No.2017J06016)and the Fundamental Research Funds for the Central Universities(No.20720180057)
文摘We demonstrate a 2080 nm long-wavelength mode-locked thulium(Tm)-doped fiber laser operating in the dissipative soliton resonance(DSR) regime. The compact all-fiber dumbbell-shaped laser is simply constructed by a 50/50 fiber loop mirror(FLM), a 10/90 FLM, and a piece of large-gain Tm-doped double-clad fiber pumped by a 793 nm laser diode. The 10/90 FLM is not only used as an output mirror, but also acts as a periodical saturable absorber for initiating DSR mode locking. The stable DSR pulses are generated at the center wavelength as long as 2080.4 nm, and the pulse duration can be tunable from 780 to 3240 ps as the pump power is increased. The maximum average output power is 1.27 W, corresponding to a pulse energy of 290 nJ and a nearly constant peak power of 93 W. This is, to the best of our knowledge, the longest wavelength for DSR operation in a mode-locked fiber laser.
基金This work is supported in part by the SNSF under grant agreement 200021_140816.
文摘We report the first demonstration of a unidirectional,isolator-free 2-μm thulium-doped fiber(TDF)laser,relying on the properties of the theta cavity(ring resonator with S-shaped feedback).The core pumped theta cavity TDF laser provides sub-Watt output power with a slope efficiency of 25%,a 2 dB flat tuning range of 1900–2050 nm,and a linewidth of 0.2 nm,and achieves the extinction ratio of 18–25 dB(depending on the feedback value)between the favored and suppressed lasing directions.It is shown that these characteristics are competitive with,if not superior to,those of conventional ring cavities.The simulation results of the linear and Kerr-nonlinear theta cavities are also presented,explaining certain unexpected features of the laser behavior and establishing the importance of the doped fiber nonlinearity on the spectral shaping of the emitted signal.
基金supported by the National Natural Science Foundation of China(Nos.60907020,91338116,and 61007046)the Key Science and Technology Project of Changchun(No.13KG31)
文摘We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber(TDF) laser based on all-fiber Mach–Zehnder interferometer(MZI) at 1.9 mm. Here a segment of 4 m single-mode TDF is pumped by 1568 nm fiber laser for 2 mm band optical gain. The MZI includes two cascaded 3 d B coupler. A segment of 3.5 m long un-pumped polarization-maintaining TDF and polarization controller(PC) are joined in the ring cavity to suppress the mode competition. Multi-wavelength lasers at 1.9 mm with wavelength number from one to four are obtained by adjusting the PC and the stability of output power of multi-wavelength fiber laser is analyzed.
基金supported in part by the National Key Research and Development Program of China(No.2022YFB3606000)in part by State Key Laboratory of Pulsed Power Laser Technology(No.SKL2020ZR02).
文摘In this paper,we report a coherent beam combining(CBC)system that involves two thulium-doped all-polarization maintaining(PM)fiber chirped pulse amplifiers.Through phase-locking the two channels via a fiber stretcher by using the stochastic parallel gradient descent(SPGD)algorithm,a maximum average power of 265 W is obtained,with a CBC efficiency of 81%and a residual phase error of λ/17.After de-chirping by a pair of diffraction gratings,the duration of the combined laser pulse is compressed to 690 fs.Taking into account the compression efficiency of 90%and the main peak energy proportion of 91%,the corresponding peak power is calculated to be 4 MW.The laser noise characteristics before and after CBC are examined,and the results indicate that the CBC would degrade the low frequency relative intensity noise(RIN),of which the integration is 1.74%in[100 Hz,2 MHz]at the maximum combined output power.In addition,the effects of the nonlinear spectrum broadening during chirped pulse amplification on the CBC efficiency are also investigated,showing that a higher extent of pulse stretching is effective in alleviating the spectrum broadening and realizing a higher output power with decent combining efficiency.
基金This project is funded by Research Grants Council of the Hong Kong Special Administrative Region,China(HKU 17200219,HKU 17209018,E-HKU701/17,CityU T42-103/16-N,and HKU C7047-16G)Natural Science Foundation of China(N_HKU712/16)。
文摘Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an efficient laser source,it was challenging to image the water content in the deep tissue with micron-level spatial resolution.To address this problem,we develop a high-power hybrid optical parametrically-oscillating emitter(HOPE)at 1930 nm,at which the vibrational absorption peak of the O-H bond locates.The maximum pulse energy is over 1.74μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns.We employ this laser source in the optical-resolution photoacoustic microscopy(OR-PAM)system to image the water content in the phantom and the biological tissue in vitro.Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution,deep penetration depth,improved sensitivity,and suppressed artifact signal of the lipid.