A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an import...A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.展开更多
We present a study of the spectral line shape associated with a High Resolution Spectrograph on the 2.16 m telescope at the Xinglong Observing Station of National Astronomical Observatories, Chinese Academy of Science...We present a study of the spectral line shape associated with a High Resolution Spectrograph on the 2.16 m telescope at the Xinglong Observing Station of National Astronomical Observatories, Chinese Academy of Sciences. This measurement is based on modeling the instrumental line shape obtained by unresolved modes from a Yb-fiber mode-locked laser frequency comb. With the current repetition rate of 250 MHz and 26 GHz mode spacing on the spectrograph, we find the absolute variation of the line center, 0.0597 pixel in the direction of the CCDs, and 0.00275 pixel （～3 m s^-1） for relative variation in successive exposures on a short timescale. A novel double-Gaussian model is presented to improve the quality of the fit by a factor of 2.47 in a typical single exposure. We also use analysis with raw moments and central moments to characterize the change in line shape across the detector. A trend in charge transfer efficiency can be found on the E2V 4096 ×4096 CCD that provides a correction for wavelength calibration aiming to reach a level of precision for radial velocity below 1 m s^- 1.展开更多
A low-thermal-noise,small-sized,monolithic crystalline whispering-gallery-mode cavity can achieve a compact laser frequency locking system.In this study,we propose generating a Fano resonance spectrum within the cryst...A low-thermal-noise,small-sized,monolithic crystalline whispering-gallery-mode cavity can achieve a compact laser frequency locking system.In this study,we propose generating a Fano resonance spectrum within the crystalline cavity to achieve frequency locking without the need for traditional modulation techniques,aiming to further simplify the locking system.By coupling a prism with the crystalline cavity,we generate a Fano transmission spectrum to serve as the error signal for laser frequency locking.Experimental results show that our method achieves a level of noise suppression comparable to the classical Pound-Drever-Hall technique,reducing laser frequency noise to near the thermal noise limit of the crystalline cavity.It enables us to suppress the laser frequency noise to below 1 Hz^(2)∕Hz in the offset frequency range of 103-105Hz and achieve a minimum noise of0.2 Hz^(2)∕Hz.We also analyzed various unique optical noises in the Fano locking technique and found that the primary factor limiting laser frequency noise in this work is still the inherent thermal noise of the crystalline cavity.Our results indicate that the proposed Fano locking technique has significant potential to simplify laser locking systems,enhance stability,and reduce overall power consumption and cost.展开更多
Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive ...Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive since they are monolithic,fundamental oscillators with high power levels and efficiencies.One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies,as this leads to flatter broadband gain spectra.However,as the gain bandwidth is increased,dispersion becomes the main limiting factor for comb bandwidth.Therefore,achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths.Here,we demonstrate the ultimate nanophotonic dispersion compensation scheme:an air-dielectric slab double-chirped mirror,which we fully integrate with the quantum cascade laser gain section.This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth.With this approach,we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations.Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.展开更多
Atomic spectroscopy serves as the basis for quantum precision measurements,where frequency-stabilized lasers are crucial for obtaining accurate atomic spectra.This work introduces a compact laser frequency stabilizati...Atomic spectroscopy serves as the basis for quantum precision measurements,where frequency-stabilized lasers are crucial for obtaining accurate atomic spectra.This work introduces a compact laser frequency stabilization system that employs a multifunctional metasurface to adjust the polarization,amplitude,and propagation direction of incident light.By combining with a Rb atomic vapor cell,the system achieves a tunable sub-Doppler spectrum for laser frequency stabilization.The experimental result demonstrates that a laser frequency stability of 3×10−11 is attained from 1 to 200 s at 780 nm with the input power at 20µW.The devices hold significant potential for compactness,integration,and mass production,making them highly suitable for quantum measurement applications.展开更多
Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface.Hence,this paper proposes a laser frequency-swept carrier(LFSC)ranging me...Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface.Hence,this paper proposes a laser frequency-swept carrier(LFSC)ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection.Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m,the standard deviation of 10 measurements was less than 70μm,measurement accuracy exceeded 27μm,and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak.This method is useful for measurements of noncooperative targets,eg.,large-scale component assembly,industrial measurement,and biomedical testing.展开更多
Optical lattice clocks demonstrate advantages in metrology and frontier physics because of their high stability.Here,we present approaches to enhancing the stability by decoupling the noise related to the short-term a...Optical lattice clocks demonstrate advantages in metrology and frontier physics because of their high stability.Here,we present approaches to enhancing the stability by decoupling the noise related to the short-term and long-term stability.For the short-term stability,we optimize the clock laser by decoupling the frequency noise,and optimize each noise contribution individually until it is below the thermal noise limit.For the long-term stability,we introduce a method to decouple the instability caused by systematic effects.Having identified that the collision frequency shift was the main limiting factor in our systems,we thus optimized the atom number fluctuations in optical lattices.Through targeted optimization,we achieve a synchronous comparison of two clocks with an average stability of 3.2×10^(-16)/√τ and a long-term stability of 2.4×10^(-18)at 8000 s.This work provides an analytical framework for enhancing optical clock stability.展开更多
The resonator integrated optic gyros（RIOGs） based on the Sagnac effect have gained extensive attention in navigation and guidance systems due to their predominant advantages： high theoretical accuracy and simple in...The resonator integrated optic gyros（RIOGs） based on the Sagnac effect have gained extensive attention in navigation and guidance systems due to their predominant advantages： high theoretical accuracy and simple integration. However, the problems of losing lock and low lock-in accuracy are the bottlenecks, which restrict the development of digital RIOGs. Therefore, a multilevel laser frequency lock-in technique has been proposed in this Letter to address these problems. The experimental results show that lock-in accuracy can be improved one order higher and without losing lock in a variable temperature environment. Then, a digital miniaturized RIOG prototype（18 cm × 18 cm × 20 cm） has been produced, and long-term（1 h） bias stability of 26.6 deg/h is successfully demonstrated.展开更多
The modulation transfer spectroscopy in an ytterbium hollow cathode lamp at 399 nm is measured. The error signal for frequency locking is optimized by measuring the dependences of its slope, linewidth and magnitude on...The modulation transfer spectroscopy in an ytterbium hollow cathode lamp at 399 nm is measured. The error signal for frequency locking is optimized by measuring the dependences of its slope, linewidth and magnitude on various parameters. Under the optimum condition, the laser frequency at 399 nm can be stabilized. The long-term stability of laser frequency is measured by monitoring the fluorescence signal of the ytterbium atomic beam induced by the locked laser. The laser frequency is shown to be tightly locked, and the stabilized laser is successfully applied to the cooling of ytterbium atoms.展开更多
Based on the Rydberg cascade electromagnetically induced transparency,we propose a simultaneous dual-wavelength locking method for Rydberg atomic sensing at room temperature.The simplified frequency-locking configurat...Based on the Rydberg cascade electromagnetically induced transparency,we propose a simultaneous dual-wavelength locking method for Rydberg atomic sensing at room temperature.The simplified frequency-locking configuration uses only one signal generator and one electro-optic modulator,realizing real-time feedback for both lasers.We studied the effect of the different probe and coupling laser powers on the error signal.In addition,the Allan variance and a 10 kHz amplitudemodulated signal are introduced to evaluate the performance of the laser frequency stabilization.In principle,the laser frequency stabilization method presented here can be extended to any cascade Rydberg atomic system.展开更多
This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping ^87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broa...This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping ^87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5 × 10^-11τ-1/2 （τ〈500 s） frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90 cm^3 volume and 10^-12τ-1/2 short-term frequency stability.展开更多
A simple and robust technique is reported to offset lock a single semiconductor laser to the atom resonance line with a frequency difference easily adjustable from a few tens of megahertz up to tens of gigahertz. The ...A simple and robust technique is reported to offset lock a single semiconductor laser to the atom resonance line with a frequency difference easily adjustable from a few tens of megahertz up to tens of gigahertz. The proposed scheme makes use of the frequency modulation spectroscopy by modulating sidebands of a fiber electro-optic modulator output. The short-term performances of a frequency offset locked semiconductor laser are experimentally demonstrated with the Allan variance of around 3.9 × 10-11 at a 2 s integration time. This method may have many applications, such as in Raman optics for an atom interferometer.展开更多
We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input...We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input intensity when an acousto-optic modulator is applied to shift the laser frequency from the resonance. We show the stabilization of a strong 795- nm laser detuned up to 550 MHz from the 87Rb 5S1/2 F=2→5P1/2F'=2 transition. The locking range can be modifed by controlling the bufer gas pressure. A laser line width of 2 MHz is achieved over 10 min.展开更多
High-order harmonic generation from one-dimensional （1D） multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser fi...High-order harmonic generation from one-dimensional （1D） multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser field is analyzed in terms of 1D Schroedinger equation with the Crank-Nicolson algorithm, The dependence of high-order harmonics on the laser frequeney and the biter-nuclear distance is discussed, It is found that the optimum range of inter-nuclear distance should be changed to get extended harmonic generation for different laser frequency, and the lower frequency laser pulse is favorable to higher order harmonic generation as the inter-nuclear distance increases.展开更多
A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequenc...A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.展开更多
Strong optical feedback in a birefringent dual frequency He-Ne laser with a high reflectivity feedback mirror has been investigated for the first time. The output characteristics of two orthogonally polarized modes ar...Strong optical feedback in a birefringent dual frequency He-Ne laser with a high reflectivity feedback mirror has been investigated for the first time. The output characteristics of two orthogonally polarized modes are demonstrated in two different optical feedback cases： one is for both modes being fed back and the other is for only one of the modes being fed back. Strong mode competition can be observed between the two modes with strong optical feedback, And when one mode＇s intensity is near its maximum, the other mode is nearly extinguished. When both modes are fed back into the laser cavity, the mode competition is stronger than when only one mode is fed back, The difference in initial intensity between the two orthogonally polarized modes plays an important role in the mode competition, which has been experimentally and theoretically demonstrated.展开更多
We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity la...We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127℃ Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359nm and 1470nm lasers. The 147Ohm laser linewidth is measured to be 407.3Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.展开更多
AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: Th...AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: The seventeen patients (7 male and 10 female; mean age 67.8 years) with difficult common bile duct (CBD) stones were not amenable for conventional endoscopic maneuvers such as sphincterotomy and mechanical lithotripsy were included in this study. Laser wavelengths of 532 nm and 1064 nm as a double pulse were applied with pulse energy of 120 mJ. The laser fiber was advanced under fluoroscopic control through the ERCP balloon catheter. Laser lithotripsy was continued until the fragment size seemed to be less than 10 mm. Endoscopic extraction of the stones and fragments was performed with the use of the Dormia basket and balloon catheter. RESULTS: Bile duct clearance was achieved in 15 of 17 patients (88%). The mean number of treatment sessions was 1.7 ± 0.6. Endoscopic stone removal could not be achieved in 2 patients (7%). Adverse effects were noted in three patients (hemobilia, pancreatitis, and cholangitis). CONCLUSION: The Frequency Doubled Double Pulse Nd:YAG (FREDDY) laser may be an effective and safe technique in treatment of difficult bile duct stones.展开更多
By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm i...By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.展开更多
We report a 42Ohm external cavity diode laser with an interference filter （IF） of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye refle...We report a 42Ohm external cavity diode laser with an interference filter （IF） of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye reflector are used for selecting wavelength and light feedback, respectively. The measured laser linewidth is 24 kHz when the diode laser is free running. Using this narrow-linewidth IF blue diode laser, we realize a compact Rb optical frequency standard without a complicated PDH system. The preliminary stability of the Rb optical frequency standard is 2 × 10^-13 at I s and decreases to 1.9 ×10^-14 at 1000s. The narrow-linewidth characteristic makes the IF blue diode laser a well suited candidate for the compact Rb optical frequency standard.展开更多
基金Supported by the National Fundamental Research Program of China under Grant No 2011CB921501the National Natural Science Foundation of China under Grant Nos 91336103,10934010 and 61078026
文摘A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11233004 and 11390371)supported by the Specialized Research Fund for Shandong Provincial Key Laboratory
文摘We present a study of the spectral line shape associated with a High Resolution Spectrograph on the 2.16 m telescope at the Xinglong Observing Station of National Astronomical Observatories, Chinese Academy of Sciences. This measurement is based on modeling the instrumental line shape obtained by unresolved modes from a Yb-fiber mode-locked laser frequency comb. With the current repetition rate of 250 MHz and 26 GHz mode spacing on the spectrograph, we find the absolute variation of the line center, 0.0597 pixel in the direction of the CCDs, and 0.00275 pixel （～3 m s^-1） for relative variation in successive exposures on a short timescale. A novel double-Gaussian model is presented to improve the quality of the fit by a factor of 2.47 in a typical single exposure. We also use analysis with raw moments and central moments to characterize the change in line shape across the detector. A trend in charge transfer efficiency can be found on the E2V 4096 ×4096 CCD that provides a correction for wavelength calibration aiming to reach a level of precision for radial velocity below 1 m s^- 1.
基金National Natural Science Foundation of China(62305136,62035007,61805112)。
文摘A low-thermal-noise,small-sized,monolithic crystalline whispering-gallery-mode cavity can achieve a compact laser frequency locking system.In this study,we propose generating a Fano resonance spectrum within the crystalline cavity to achieve frequency locking without the need for traditional modulation techniques,aiming to further simplify the locking system.By coupling a prism with the crystalline cavity,we generate a Fano transmission spectrum to serve as the error signal for laser frequency locking.Experimental results show that our method achieves a level of noise suppression comparable to the classical Pound-Drever-Hall technique,reducing laser frequency noise to near the thermal noise limit of the crystalline cavity.It enables us to suppress the laser frequency noise to below 1 Hz^(2)∕Hz in the offset frequency range of 103-105Hz and achieve a minimum noise of0.2 Hz^(2)∕Hz.We also analyzed various unique optical noises in the Fano locking technique and found that the primary factor limiting laser frequency noise in this work is still the inherent thermal noise of the crystalline cavity.Our results indicate that the proposed Fano locking technique has significant potential to simplify laser locking systems,enhance stability,and reduce overall power consumption and cost.
基金supported in part by the Spectral Combs from UV to THz(SCOUT)and SIGMA+programs from the Defense Advanced Research Project Agency(DARPA)support from the Gordon and Betty Moore Foundation through Grant GBMF11446 to the University of Texas at Austin.
文摘Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive since they are monolithic,fundamental oscillators with high power levels and efficiencies.One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies,as this leads to flatter broadband gain spectra.However,as the gain bandwidth is increased,dispersion becomes the main limiting factor for comb bandwidth.Therefore,achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths.Here,we demonstrate the ultimate nanophotonic dispersion compensation scheme:an air-dielectric slab double-chirped mirror,which we fully integrate with the quantum cascade laser gain section.This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth.With this approach,we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations.Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.
基金supported by the Fundamental Research Funds for the Central Universities(No.KG21008401).
文摘Atomic spectroscopy serves as the basis for quantum precision measurements,where frequency-stabilized lasers are crucial for obtaining accurate atomic spectra.This work introduces a compact laser frequency stabilization system that employs a multifunctional metasurface to adjust the polarization,amplitude,and propagation direction of incident light.By combining with a Rb atomic vapor cell,the system achieves a tunable sub-Doppler spectrum for laser frequency stabilization.The experimental result demonstrates that a laser frequency stability of 3×10−11 is attained from 1 to 200 s at 780 nm with the input power at 20µW.The devices hold significant potential for compactness,integration,and mass production,making them highly suitable for quantum measurement applications.
基金National Natural Science Foundation of China(52475532, 51875447)
文摘Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface.Hence,this paper proposes a laser frequency-swept carrier(LFSC)ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection.Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m,the standard deviation of 10 measurements was less than 70μm,measurement accuracy exceeded 27μm,and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak.This method is useful for measurements of noncooperative targets,eg.,large-scale component assembly,industrial measurement,and biomedical testing.
基金supported by the Shanghai Municipal Science and Technology Major Project(No.2019SHZDZX01)the National Natural Science Foundation of China(No.11134003)+1 种基金the National Key Research and Development Program of China(Nos.2016YFA0302103,2017YFF0212003,and 2016YFB0501601)the Shanghai Excellent Academic Leaders Program(No.12XD1402400)。
文摘Optical lattice clocks demonstrate advantages in metrology and frontier physics because of their high stability.Here,we present approaches to enhancing the stability by decoupling the noise related to the short-term and long-term stability.For the short-term stability,we optimize the clock laser by decoupling the frequency noise,and optimize each noise contribution individually until it is below the thermal noise limit.For the long-term stability,we introduce a method to decouple the instability caused by systematic effects.Having identified that the collision frequency shift was the main limiting factor in our systems,we thus optimized the atom number fluctuations in optical lattices.Through targeted optimization,we achieve a synchronous comparison of two clocks with an average stability of 3.2×10^(-16)/√τ and a long-term stability of 2.4×10^(-18)at 8000 s.This work provides an analytical framework for enhancing optical clock stability.
基金supported by the National Natural Science Foundation of China(Nos.51635011,61640601,61571406,and 51727808)the Outstanding Youth Talents Program of Shanxi Province(No.2016002)+1 种基金the Science and Technology on Electronic Test&Measurement Laboratory(No.11010311)the Shanxi "1331 KSC"
文摘The resonator integrated optic gyros（RIOGs） based on the Sagnac effect have gained extensive attention in navigation and guidance systems due to their predominant advantages： high theoretical accuracy and simple integration. However, the problems of losing lock and low lock-in accuracy are the bottlenecks, which restrict the development of digital RIOGs. Therefore, a multilevel laser frequency lock-in technique has been proposed in this Letter to address these problems. The experimental results show that lock-in accuracy can be improved one order higher and without losing lock in a variable temperature environment. Then, a digital miniaturized RIOG prototype（18 cm × 18 cm × 20 cm） has been produced, and long-term（1 h） bias stability of 26.6 deg/h is successfully demonstrated.
基金Project supported by the National Natural Science Foundation of China(Grant No.10774044)the National Key Basic Research and Development Program of China(Grant No.2010CB922903)+1 种基金the Science and Technology Commission of Shanghai Municipality of China(Grant No.07JC14019)Shanghai Pujiang Talent Program of China(Grant No.07PJ14038)
文摘The modulation transfer spectroscopy in an ytterbium hollow cathode lamp at 399 nm is measured. The error signal for frequency locking is optimized by measuring the dependences of its slope, linewidth and magnitude on various parameters. Under the optimum condition, the laser frequency at 399 nm can be stabilized. The long-term stability of laser frequency is measured by monitoring the fluorescence signal of the ytterbium atomic beam induced by the locked laser. The laser frequency is shown to be tightly locked, and the stabilized laser is successfully applied to the cooling of ytterbium atoms.
基金supported by the National Natural Science Foundation of China(Nos.61901495 and 12104509)the Scientific Research Project of National University of Defense Technology(Nos.ZK19-20 and ZK20-13)。
文摘Based on the Rydberg cascade electromagnetically induced transparency,we propose a simultaneous dual-wavelength locking method for Rydberg atomic sensing at room temperature.The simplified frequency-locking configuration uses only one signal generator and one electro-optic modulator,realizing real-time feedback for both lasers.We studied the effect of the different probe and coupling laser powers on the error signal.In addition,the Allan variance and a 10 kHz amplitudemodulated signal are introduced to evaluate the performance of the laser frequency stabilization.In principle,the laser frequency stabilization method presented here can be extended to any cascade Rydberg atomic system.
基金supported by National Natural Science Foundation of China (Grant Nos 10574141 and 10675162)
文摘This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping ^87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5 × 10^-11τ-1/2 （τ〈500 s） frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90 cm^3 volume and 10^-12τ-1/2 short-term frequency stability.
基金supported by the National Natural Science Foundation of China(No.61473166)
文摘A simple and robust technique is reported to offset lock a single semiconductor laser to the atom resonance line with a frequency difference easily adjustable from a few tens of megahertz up to tens of gigahertz. The proposed scheme makes use of the frequency modulation spectroscopy by modulating sidebands of a fiber electro-optic modulator output. The short-term performances of a frequency offset locked semiconductor laser are experimentally demonstrated with the Allan variance of around 3.9 × 10-11 at a 2 s integration time. This method may have many applications, such as in Raman optics for an atom interferometer.
基金supported by the National Natural Science Foundation of China(Nos.60925022,10804097,and 11104243)the National "973" Program of China(No.2013CB329501)the Fundamental Research Funds for the Central Universities(No.2012FZA3001)
文摘We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input intensity when an acousto-optic modulator is applied to shift the laser frequency from the resonance. We show the stabilization of a strong 795- nm laser detuned up to 550 MHz from the 87Rb 5S1/2 F=2→5P1/2F'=2 transition. The locking range can be modifed by controlling the bufer gas pressure. A laser line width of 2 MHz is achieved over 10 min.
基金This work was supported by the Shanghai Priority Academic Discipline, the National Natural Science Foundation of China (No. 10234030 and 10374030)the National Key Project for Basic Research of China (No.1999075204)the Key Project sponsored by Shanghai Science and Technology Committee (No. 036105019and 03DJ14001)the Twilight Project sponsored by Shanghai Education Committee (No. 03SG23)
文摘High-order harmonic generation from one-dimensional （1D） multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser field is analyzed in terms of 1D Schroedinger equation with the Crank-Nicolson algorithm, The dependence of high-order harmonics on the laser frequeney and the biter-nuclear distance is discussed, It is found that the optimum range of inter-nuclear distance should be changed to get extended harmonic generation for different laser frequency, and the lower frequency laser pulse is favorable to higher order harmonic generation as the inter-nuclear distance increases.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91436103 and 11204374
文摘A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.
基金Project supported by the Major Program of National Natural Science Foundation of China （Grant No 60438010）.
文摘Strong optical feedback in a birefringent dual frequency He-Ne laser with a high reflectivity feedback mirror has been investigated for the first time. The output characteristics of two orthogonally polarized modes are demonstrated in two different optical feedback cases： one is for both modes being fed back and the other is for only one of the modes being fed back. Strong mode competition can be observed between the two modes with strong optical feedback, And when one mode＇s intensity is near its maximum, the other mode is nearly extinguished. When both modes are fed back into the laser cavity, the mode competition is stronger than when only one mode is fed back, The difference in initial intensity between the two orthogonally polarized modes plays an important role in the mode competition, which has been experimentally and theoretically demonstrated.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874009,11074011 and 91436210the International Science and Technology Cooperation Program of China under Grant No 2010DFR10900
文摘We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127℃ Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359nm and 1470nm lasers. The 147Ohm laser linewidth is measured to be 407.3Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.
基金The 2007 research fund of Wonkwang University and Wonkwang Clinical Research Institute
文摘AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: The seventeen patients (7 male and 10 female; mean age 67.8 years) with difficult common bile duct (CBD) stones were not amenable for conventional endoscopic maneuvers such as sphincterotomy and mechanical lithotripsy were included in this study. Laser wavelengths of 532 nm and 1064 nm as a double pulse were applied with pulse energy of 120 mJ. The laser fiber was advanced under fluoroscopic control through the ERCP balloon catheter. Laser lithotripsy was continued until the fragment size seemed to be less than 10 mm. Endoscopic extraction of the stones and fragments was performed with the use of the Dormia basket and balloon catheter. RESULTS: Bile duct clearance was achieved in 15 of 17 patients (88%). The mean number of treatment sessions was 1.7 ± 0.6. Endoscopic stone removal could not be achieved in 2 patients (7%). Adverse effects were noted in three patients (hemobilia, pancreatitis, and cholangitis). CONCLUSION: The Frequency Doubled Double Pulse Nd:YAG (FREDDY) laser may be an effective and safe technique in treatment of difficult bile duct stones.
基金Supported by the International Cooperation Projects of Ministry of Science and Technology under Grant No 2012DFB10120the National Natural Science Foundation of China under Grant No 61177059
文摘By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.
基金Supported by the China Academy of Space Technology Foundation under Grant No CAST-2015-5-10the National Hi-Tech Research and Development Programthe National Natural Science Foundation of China under Grant No 91436210
文摘We report a 42Ohm external cavity diode laser with an interference filter （IF） of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye reflector are used for selecting wavelength and light feedback, respectively. The measured laser linewidth is 24 kHz when the diode laser is free running. Using this narrow-linewidth IF blue diode laser, we realize a compact Rb optical frequency standard without a complicated PDH system. The preliminary stability of the Rb optical frequency standard is 2 × 10^-13 at I s and decreases to 1.9 ×10^-14 at 1000s. The narrow-linewidth characteristic makes the IF blue diode laser a well suited candidate for the compact Rb optical frequency standard.
