A broadband tunable grating-coupled external cavity laser is realized by employing a self-assembled InAs/GaAs quantum-dot （QD） superluminescent diode （SLD） as the gain device. The SLD device is processed with a be...A broadband tunable grating-coupled external cavity laser is realized by employing a self-assembled InAs/GaAs quantum-dot （QD） superluminescent diode （SLD） as the gain device. The SLD device is processed with a bent-waveguide structure and facet antireflection （AR） coating. Tuning bandwidths of 106 nm and 117 nm are achieved under a-A and 3.5-A injection currents, respectively. The large tuning range originates essentially from the broad gain spectrum of self-assembled QDs. The bent waveguide structure combined with the facet AR coating plays a role in suppressing the inner-cavity lasing under a large injection current.展开更多
Effect of high level of spontaneous and carrier noise on mode-locked hybrid soliton pulse source and relative intensity noise is described. Transform limited pulses are not generated over a wide frequency range becaus...Effect of high level of spontaneous and carrier noise on mode-locked hybrid soliton pulse source and relative intensity noise is described. Transform limited pulses are not generated over a wide frequency range because of these noises.展开更多
In order to choose appropriate frequency stabilization method in the atom gravimeter system under construction,Doppler-free dichroic atomic vapor laser lock(Doppler-free DAVLL)and saturated absorption spectroscopy(SAS...In order to choose appropriate frequency stabilization method in the atom gravimeter system under construction,Doppler-free dichroic atomic vapor laser lock(Doppler-free DAVLL)and saturated absorption spectroscopy(SAS)method were implemented on Rubidium atomic vapor.Basic principle and experimental details of both frequency stabilization methods were introduced.With restructuring of optical path and applying of self-made low noise photoelectric detector as well as digital lock module,excellent error signal was obtained.For each method,two sets of locking system were built and kept locked during3000 s′data acquisition.A frequency fluctuation of 629 k Hz when the laser is free running and of16.2 k Hz 31.4 k Hz after locked by SAS and Doppler-free DAVLL were calculated respectively,corresponding to a frequency stability of 1.64×10^(-9)in the condition of free running and 4.21×10^(-11)&8.18×10^(-11)after locked for averaging time of 10 s.The strength and weakness of both methods were elaborated with the demand of system miniaturization.After compared with SAS,Doppler-free DAVLL isconsidered to be a promising choice for miniaturization and modularization in atom interferometry gravimeter.展开更多
Interference filter-stabilized external cavity diode lasers （ECDLs） have properties of simple configurations, high sta- bilities, and narrow linewidths. However, the interference filter used in common ECDL designs r...Interference filter-stabilized external cavity diode lasers （ECDLs） have properties of simple configurations, high sta- bilities, and narrow linewidths. However, the interference filter used in common ECDL designs requires an ultra-narrow bandwidth （about 0.3 nm） to achieve mode selection, that is considerably expensive and not yet available for a wide range of wavelengths. In this paper, a robust ECDL using an available broad bandwidth （about 4 nm） interference filter as the wavelength discriminator is constructed and tested. The ECDL demonstrated a narrow Lorentzian fitted linewidth of 95 kHz and a spectral purity of 2.9 MHz. The long-term frequency stability of the ECDL reaches 5.59 x 10 12.展开更多
We present a compact and practical scheme of building a ~780 nm external cavity diode laser(ECDL) whose wavelength is mainly determined by an interference filter. The Lorentzian linewidth measured by the heterodyne be...We present a compact and practical scheme of building a ~780 nm external cavity diode laser(ECDL) whose wavelength is mainly determined by an interference filter. The Lorentzian linewidth measured by the heterodyne beating between two identical lasers is 60 k Hz, and the geometry size of the laser is only 71.5 mm×65 mm×40 mm. The linear cavity design is less sensitive to misalignment induced by mechanical and thermal disturbances, and in comparison to a common grating-based design, the sensitivity to vibration is substantially reduced. Due to its excellent performance, the laser design has already been applied to cold atom trapping experiments. This interference filter ECDL method can also be extended to other wavelengths and widen the application range of diode laser.展开更多
A 1550-nm linearly tunable continuous wave （CW） single-mode external cavity diode laser （ECDL） based on a singlecavity all-dielectric thin-film Fabry-Pérot filter （s-AFPF） is proposed and realized in this p...A 1550-nm linearly tunable continuous wave （CW） single-mode external cavity diode laser （ECDL） based on a singlecavity all-dielectric thin-film Fabry-Pérot filter （s-AFPF） is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable ECDL relevant parameters： the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm-1552.426 nm, a stable output optical power in the range of 40 μW-50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz-150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.展开更多
An external cavity quantum cascade laser （QCL） array with a wide tuning range and high output power is pre- sented. The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow ...An external cavity quantum cascade laser （QCL） array with a wide tuning range and high output power is pre- sented. The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow configuration. Taking advantage of the single-lobed fundamental supermode far-field pattern, the tuning capa- bility of 30.6cm-1 is achieved with a fixed injected current of 3.5 A at room temperature. Single-mode emission can be observed in the entire process. The maximum single-mode output power of the external cavity setup is as high as 25mW and is essential in real applications.展开更多
The topic of improving the mechanical stability of external cavity diode lasers(ECDLs)has recently attracted widespread attention and interest.The use of corner-cube-array(CCA)-based resonators provides a potential so...The topic of improving the mechanical stability of external cavity diode lasers(ECDLs)has recently attracted widespread attention and interest.The use of corner-cube-array(CCA)-based resonators provides a potential solution for this purpose,although continuous oscillation at super large incident angle remains challenging.In this work,we employ the CCA resonator to generate continuous oscillation within±20°angular misalignment of cavity mirror in experiment.On the basis of retroreflection theory,the retroreflectivity of a CCA is analyzed by using optical simulation software.Notably,the experiment verifies the advantage of using a CCA over a plane mirror in laser resonator,thereby providing a promising approach for ECDLs.The threshold characteristic curves measured at different incident angles in the experiment verify that the CCA possesses an obvious anti-angle misalignment performance.This research introduces an alternative solution of using CCA resonator instead of parallel plane cavity,thereby realizing an adjustment-free ECDL with enhanced mechanical stability.展开更多
The traditional Littrow-type external cavity diode laser(ECDL)has a collimating cavity that is sensitive to external vibration.To solve this problem,we demonstrate a high-stability Littrow-type ECDL using a non-collim...The traditional Littrow-type external cavity diode laser(ECDL)has a collimating cavity that is sensitive to external vibration.To solve this problem,we demonstrate a high-stability Littrow-type ECDL using a non-collimating cavity.The laser has a maximum output power of 30.2 mW at 420 mA drive current.The 3 dB tuning range of the laser is more than 100 nm covering all of the C-band.Compared to the ECDL using a collimating cavity,the root mean square(RMS)power stability is improved from 0.52%to 0.02%and the peak-to-peak power stability is improved from 3.6%to 0.1%.The integral linewidth is suppressed from 70 to 15.4 kHz and the intrinsic linewidth is 2.2 kHz with a 75 mm cavity length.By prolonging the cavity length,the intrinsic linewidth can be reduced to 31 Hz.This study presents a simple structure to substantially improve the power stability of ECDLs and reduce the linewidth to the Hz level.展开更多
A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser (FBG-ECL) and a Mach-Zehnder interferometer (MZI) were reported in this paper. The MZI provided a Q-switching with ...A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser (FBG-ECL) and a Mach-Zehnder interferometer (MZI) were reported in this paper. The MZI provided a Q-switching with response time in the order of micro-seconds. The FBG-ECL provided narrow pulses as seeds to shorten the Q-switched pulses. Experimentally, pulse width of 0.8 μs was measured, which was one fifth of the pulse width without self-seeding.展开更多
For different external cavity lengths, lasing wavelength variation of fiber grating external cavity semiconductor laser (FGECSL) with ambient temperature has been investigated theoretically, and the theoretical result...For different external cavity lengths, lasing wavelength variation of fiber grating external cavity semiconductor laser (FGECSL) with ambient temperature has been investigated theoretically, and the theoretical results are in agreement with reported experimental observations.展开更多
The last half-century was transformed by the electronic revolution that essentially reproduced the human brain and its computing capacity on a chip. But over time, scientists have realized that something was missing t...The last half-century was transformed by the electronic revolution that essentially reproduced the human brain and its computing capacity on a chip. But over time, scientists have realized that something was missing to give life, so to speak, to the small chip with a brain： One needed to awaken its senses and develop its muscles! This challenge was solved through MEMS （micro electro mechanical systems）. Indeed, MEMS today are equipped with the sense of sight, smell, hearing, taste and touch through microsensors. They are also capable of physical exertion through small muscles called microactuators. These new capabilities open wide fields of imagination and important specific applications.展开更多
We propose and numerically test,to our knowledge,a novel concept for asymmetric vortex beam generation in a degenerate vertical external cavity surface emitting laser(DVECSEL).The method is based on a phase-locking ri...We propose and numerically test,to our knowledge,a novel concept for asymmetric vortex beam generation in a degenerate vertical external cavity surface emitting laser(DVECSEL).The method is based on a phase-locking ring array of lasers created inside a degenerate cavity with a binary amplitude mask containing circular holes.The diffraction engineering of the mask profile allows for controlling the complex coupling between the lasers.The asymmetry between different lasers is introduced by varying the hole diameters corresponding to different lasers.展开更多
Narrow linewidth stabilized lasers are central to precision applications that operate across the visible to short-wave infrared wavelengths,including optical clocks,quantum sensing and computing,ultra-low noise microw...Narrow linewidth stabilized lasers are central to precision applications that operate across the visible to short-wave infrared wavelengths,including optical clocks,quantum sensing and computing,ultra-low noise microwave generation,and fiber sensing.Today,these spectrally pure sources are realized using multiple external cavity tabletop lasers locked to bulk-optic free-space reference cavities.Integration of this technology will enable portable precision applications with improved reliability and robustness.Here,we report wavelength-flexible design and operation,over more than an octave span,of an integrated coil-resonator-stabilized Brillouin laser architecture.Leveraging a versatile two-stage noise reduction approach,we achieve low linewidths and high stability with chip-scale laser designs based on the ultra-low-loss,CMOS-compatible silicon nitride platform.We report operation at 674 and 698 nm for applications to strontium neutral and trapped-ion clocks,quantum sensing and computing,and at 1550 nm for applications to fiber sensing and ultra-low phase noise microwave generation.Over this range we demonstrate frequency noise reduction from 1 to 10 MHz resulting in 1.0-17 Hz fundamental and 181-630 Hz integral linewidths and an Allan deviation of 6.5×10^(-13)at 1ms for 674 nm,6.0×10^(-13)at 15ms for 698 nm,and 2.6×10^(-13)at 15 ms for 1550 nm.This work demonstrates the lowest fundamental and integral linewidths and highest stability achieved to date for stabilized Brillouin lasers with integrated coil-resonator references,with over an order of magnitude improvement in the visible wavelength range.These results unlock the potential of integrated,ultra-low-phase-noise stabilized lasers for precision applications and further integration in systems-on-chip solutions.展开更多
Because it has the advantages of high sensitivity, and it is easy to demodulate and convenient to select in FDM system, the coherent optical fiber communication system is much suitable to be used in long distance opt...Because it has the advantages of high sensitivity, and it is easy to demodulate and convenient to select in FDM system, the coherent optical fiber communication system is much suitable to be used in long distance optical communication systems and in optical fiber WANs. There are two major patterns in coherent optical fiber communication: heterodyne and homodyne. Compared with the heterodyne scheme, the homodyne optical fiber communication system has the following advantages: (1) The sensitivity of the homodyne receiver is higher than that of the heterodyne receiver. As we know, the PSK homodyne optical fiber communication system has the highest sensitivity in coherent optical fiber communication systems. So it is much suitable to be used in long distance optical communication systems or in FDM systems. (2) Because the homodyne receiver only uses the baseband to demodulate the transmitted signals, it occupies much narrower frequency domain than the heterodyne receiver does, which makes it more suitable to be used in multichannel systems. (3) The demodulation pattern used in homodyne receiver is much easier than that used in the heterodyne receiver, since it only needs the baseband demodulation. Usually we construct a homodyne receiver with an optical phase locked loop (OPLL). The research of the OPLL began at 1960′s and the study of the homodyne receiver has been made gradually. In 1984, the first homodyne optical fiber communication system was demonstrated in BTRL, in which the signal laser and the local laser were all 1.5 μm He Ne gas lasers, and the OPLL used was a balanced one. In 1989, L.G.Kazovsky demonstrated experimentally a homodyne receiver in Bellcore using two 1.3 μm Nd:YAG lasers as the signal laser and the local laser and also using a balanced OPLL. Because the linewidth of the normal semiconductor laser is too large and its frequency stability is much poorer, it is very difficult to construct a homodyne receiver with the semiconductor lasers. At the end of 1989, the first Dissertation completed Jul. 1992homodyne optical fiber communication system using two 1.5 μm external cavity semiconductor lasers as the signal laser and the local laser, respectively, was finished in AT&T Bell Lab by J. M. Kahn, in which the OPLL was also a balanced one. In China, the research of the homodyne optical fiber communication system was funded by the National Seventh Five Year Program and by the National Natural Science Foundation. The difficulties to construct a homodyne optical fiber communication system are listed as follows: (1) In homodyne communication systems, the signal laser′s frequency should be stable to avoid the penalty of the receiver′s BER and the crosstalk to other channels in a FDM system, and the local laser could be tuned widely and easily to cover all the signal lasers′ frequency domain. Both the signal laser and the local laser should be narrow in linewidth to decrease the influence of the laser′s phase noise on the BER of the receiver. (2) The modulation pattern used should be studied and chosen carefully because the requirements of different kinds of modulation on the laser, the receiver and the channel are different. (3) Since the construction of the linear OPLL (the balanced) and the nonlinear OPLL (the Costas OPLL, or the Decision Driven OPLL) are rather different, their requirements on the linewidths of the lasers are different too, we should study the theory and the construction of the OPLL carefully to select the suitable scheme to realize. (4) In a multichannel system (such as a FDM system), the influence of crosstalk between channels on the homodyne system should be researched carefully. The technology used to stabilize the channel interval should also be studied. In this thesis, the homodyne optical fiber communication system has been theoretically analyzed, the technical difficulties of constructing the system have been studied. Several kinds of external cavity semiconductor laser have been researched experimentally. Compared展开更多
基金Project supported by the National Key Basic Research and Development Program of China (Grant No. 2006CB604904)the National Natural Science Foundation of China (Grant Nos. 60976057, 60876086, 60776037, and 10775106)
文摘A broadband tunable grating-coupled external cavity laser is realized by employing a self-assembled InAs/GaAs quantum-dot （QD） superluminescent diode （SLD） as the gain device. The SLD device is processed with a bent-waveguide structure and facet antireflection （AR） coating. Tuning bandwidths of 106 nm and 117 nm are achieved under a-A and 3.5-A injection currents, respectively. The large tuning range originates essentially from the broad gain spectrum of self-assembled QDs. The bent waveguide structure combined with the facet AR coating plays a role in suppressing the inner-cavity lasing under a large injection current.
文摘Effect of high level of spontaneous and carrier noise on mode-locked hybrid soliton pulse source and relative intensity noise is described. Transform limited pulses are not generated over a wide frequency range because of these noises.
文摘In order to choose appropriate frequency stabilization method in the atom gravimeter system under construction,Doppler-free dichroic atomic vapor laser lock(Doppler-free DAVLL)and saturated absorption spectroscopy(SAS)method were implemented on Rubidium atomic vapor.Basic principle and experimental details of both frequency stabilization methods were introduced.With restructuring of optical path and applying of self-made low noise photoelectric detector as well as digital lock module,excellent error signal was obtained.For each method,two sets of locking system were built and kept locked during3000 s′data acquisition.A frequency fluctuation of 629 k Hz when the laser is free running and of16.2 k Hz 31.4 k Hz after locked by SAS and Doppler-free DAVLL were calculated respectively,corresponding to a frequency stability of 1.64×10^(-9)in the condition of free running and 4.21×10^(-11)&8.18×10^(-11)after locked for averaging time of 10 s.The strength and weakness of both methods were elaborated with the demand of system miniaturization.After compared with SAS,Doppler-free DAVLL isconsidered to be a promising choice for miniaturization and modularization in atom interferometry gravimeter.
基金Project supported by the Foundation of Based Technology of China(Grant No.YXBGD20151JL01)the National Natural Science Foundation of China(Grant Nos.61376049,61604007,11674016,61378058,61575008,and 61574011)+1 种基金the Natural Science Foundation of Beijing City,China(Grant Nos.4172009 and4152003)the Beijing Municipal Commission of Education of China(Grant Nos.PXM2017 014204 500034 and PXM2016 014204 500018)
文摘Interference filter-stabilized external cavity diode lasers （ECDLs） have properties of simple configurations, high sta- bilities, and narrow linewidths. However, the interference filter used in common ECDL designs requires an ultra-narrow bandwidth （about 0.3 nm） to achieve mode selection, that is considerably expensive and not yet available for a wide range of wavelengths. In this paper, a robust ECDL using an available broad bandwidth （about 4 nm） interference filter as the wavelength discriminator is constructed and tested. The ECDL demonstrated a narrow Lorentzian fitted linewidth of 95 kHz and a spectral purity of 2.9 MHz. The long-term frequency stability of the ECDL reaches 5.59 x 10 12.
基金supported by the National Natural Science Foundation of China (No.51275523)the State Key Laboratory of Aerodynamics Research Fund (No.SKLA2019040302)。
文摘We present a compact and practical scheme of building a ~780 nm external cavity diode laser(ECDL) whose wavelength is mainly determined by an interference filter. The Lorentzian linewidth measured by the heterodyne beating between two identical lasers is 60 k Hz, and the geometry size of the laser is only 71.5 mm×65 mm×40 mm. The linear cavity design is less sensitive to misalignment induced by mechanical and thermal disturbances, and in comparison to a common grating-based design, the sensitivity to vibration is substantially reduced. Due to its excellent performance, the laser design has already been applied to cold atom trapping experiments. This interference filter ECDL method can also be extended to other wavelengths and widen the application range of diode laser.
基金the Key Laboratory of Functional Crystals and Laser Technology,Chinese Academy of Sciences(Grant No.JTJG201109)the Guangdong Province&Chinese Academy of Sciences Comprehensive Strategic Cooperation Project(Grant No.2010A090100014)the 2009 Technology Research and Development Fund of Shenzhen,China(Grant No.O702011001)
文摘A 1550-nm linearly tunable continuous wave （CW） single-mode external cavity diode laser （ECDL） based on a singlecavity all-dielectric thin-film Fabry-Pérot filter （s-AFPF） is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable ECDL relevant parameters： the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm-1552.426 nm, a stable output optical power in the range of 40 μW-50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz-150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.
基金Supported by the National Basic Research Program of China under Grant No 2013CB632801the National Key Research and Development Program of China under Grant No 2016YFB0402303+2 种基金the National Natural Science Foundation of China under Grant Nos 61435014,61627822,61574136,61306058 and 61404131the Key Projects of Chinese Academy of Sciences under Grant No ZDRW-XH-2016-4the Beijing Natural Science Foundation under Grant No 4162060
文摘An external cavity quantum cascade laser （QCL） array with a wide tuning range and high output power is pre- sented. The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow configuration. Taking advantage of the single-lobed fundamental supermode far-field pattern, the tuning capa- bility of 30.6cm-1 is achieved with a fixed injected current of 3.5 A at room temperature. Single-mode emission can be observed in the entire process. The maximum single-mode output power of the external cavity setup is as high as 25mW and is essential in real applications.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20240613)Jiangsu Province’s“Innovation and Entrepreneurship Doctor”Program(Grant No.JSSCBS20230088)+4 种基金Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant No.NY224123)Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications(Grant No.NY222112)Beijing Nova Program(Grant No.20240484696)Wenzhou Major Science and Technology Innovation Key Project(Grant No.ZG2020046)INNOVATION Program for Quantum Science and Technology(Grant No.2021ZD0303200)。
文摘The topic of improving the mechanical stability of external cavity diode lasers(ECDLs)has recently attracted widespread attention and interest.The use of corner-cube-array(CCA)-based resonators provides a potential solution for this purpose,although continuous oscillation at super large incident angle remains challenging.In this work,we employ the CCA resonator to generate continuous oscillation within±20°angular misalignment of cavity mirror in experiment.On the basis of retroreflection theory,the retroreflectivity of a CCA is analyzed by using optical simulation software.Notably,the experiment verifies the advantage of using a CCA over a plane mirror in laser resonator,thereby providing a promising approach for ECDLs.The threshold characteristic curves measured at different incident angles in the experiment verify that the CCA possesses an obvious anti-angle misalignment performance.This research introduces an alternative solution of using CCA resonator instead of parallel plane cavity,thereby realizing an adjustment-free ECDL with enhanced mechanical stability.
基金supported by the National Natural Science Foundation of China(No.61627821)。
文摘The traditional Littrow-type external cavity diode laser(ECDL)has a collimating cavity that is sensitive to external vibration.To solve this problem,we demonstrate a high-stability Littrow-type ECDL using a non-collimating cavity.The laser has a maximum output power of 30.2 mW at 420 mA drive current.The 3 dB tuning range of the laser is more than 100 nm covering all of the C-band.Compared to the ECDL using a collimating cavity,the root mean square(RMS)power stability is improved from 0.52%to 0.02%and the peak-to-peak power stability is improved from 3.6%to 0.1%.The integral linewidth is suppressed from 70 to 15.4 kHz and the intrinsic linewidth is 2.2 kHz with a 75 mm cavity length.By prolonging the cavity length,the intrinsic linewidth can be reduced to 31 Hz.This study presents a simple structure to substantially improve the power stability of ECDLs and reduce the linewidth to the Hz level.
文摘A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser (FBG-ECL) and a Mach-Zehnder interferometer (MZI) were reported in this paper. The MZI provided a Q-switching with response time in the order of micro-seconds. The FBG-ECL provided narrow pulses as seeds to shorten the Q-switched pulses. Experimentally, pulse width of 0.8 μs was measured, which was one fifth of the pulse width without self-seeding.
文摘For different external cavity lengths, lasing wavelength variation of fiber grating external cavity semiconductor laser (FGECSL) with ambient temperature has been investigated theoretically, and the theoretical results are in agreement with reported experimental observations.
文摘The last half-century was transformed by the electronic revolution that essentially reproduced the human brain and its computing capacity on a chip. But over time, scientists have realized that something was missing to give life, so to speak, to the small chip with a brain： One needed to awaken its senses and develop its muscles! This challenge was solved through MEMS （micro electro mechanical systems）. Indeed, MEMS today are equipped with the sense of sight, smell, hearing, taste and touch through microsensors. They are also capable of physical exertion through small muscles called microactuators. These new capabilities open wide fields of imagination and important specific applications.
基金Science and Engineering Research Board(SIR/2022/00019,CRG/2021/00306)QuanTEduPAUSE.
文摘We propose and numerically test,to our knowledge,a novel concept for asymmetric vortex beam generation in a degenerate vertical external cavity surface emitting laser(DVECSEL).The method is based on a phase-locking ring array of lasers created inside a degenerate cavity with a binary amplitude mask containing circular holes.The diffraction engineering of the mask profile allows for controlling the complex coupling between the lasers.The asymmetry between different lasers is introduced by varying the hole diameters corresponding to different lasers.
基金supported by DARPA GRYPHON,under Award Number HR0011-22-2-0008by the U.S.Army Research Office under contract/grant number W911NF2310179+1 种基金by the NSF under Award Number 2016244by a gift from Thorlabs.
文摘Narrow linewidth stabilized lasers are central to precision applications that operate across the visible to short-wave infrared wavelengths,including optical clocks,quantum sensing and computing,ultra-low noise microwave generation,and fiber sensing.Today,these spectrally pure sources are realized using multiple external cavity tabletop lasers locked to bulk-optic free-space reference cavities.Integration of this technology will enable portable precision applications with improved reliability and robustness.Here,we report wavelength-flexible design and operation,over more than an octave span,of an integrated coil-resonator-stabilized Brillouin laser architecture.Leveraging a versatile two-stage noise reduction approach,we achieve low linewidths and high stability with chip-scale laser designs based on the ultra-low-loss,CMOS-compatible silicon nitride platform.We report operation at 674 and 698 nm for applications to strontium neutral and trapped-ion clocks,quantum sensing and computing,and at 1550 nm for applications to fiber sensing and ultra-low phase noise microwave generation.Over this range we demonstrate frequency noise reduction from 1 to 10 MHz resulting in 1.0-17 Hz fundamental and 181-630 Hz integral linewidths and an Allan deviation of 6.5×10^(-13)at 1ms for 674 nm,6.0×10^(-13)at 15ms for 698 nm,and 2.6×10^(-13)at 15 ms for 1550 nm.This work demonstrates the lowest fundamental and integral linewidths and highest stability achieved to date for stabilized Brillouin lasers with integrated coil-resonator references,with over an order of magnitude improvement in the visible wavelength range.These results unlock the potential of integrated,ultra-low-phase-noise stabilized lasers for precision applications and further integration in systems-on-chip solutions.
文摘Because it has the advantages of high sensitivity, and it is easy to demodulate and convenient to select in FDM system, the coherent optical fiber communication system is much suitable to be used in long distance optical communication systems and in optical fiber WANs. There are two major patterns in coherent optical fiber communication: heterodyne and homodyne. Compared with the heterodyne scheme, the homodyne optical fiber communication system has the following advantages: (1) The sensitivity of the homodyne receiver is higher than that of the heterodyne receiver. As we know, the PSK homodyne optical fiber communication system has the highest sensitivity in coherent optical fiber communication systems. So it is much suitable to be used in long distance optical communication systems or in FDM systems. (2) Because the homodyne receiver only uses the baseband to demodulate the transmitted signals, it occupies much narrower frequency domain than the heterodyne receiver does, which makes it more suitable to be used in multichannel systems. (3) The demodulation pattern used in homodyne receiver is much easier than that used in the heterodyne receiver, since it only needs the baseband demodulation. Usually we construct a homodyne receiver with an optical phase locked loop (OPLL). The research of the OPLL began at 1960′s and the study of the homodyne receiver has been made gradually. In 1984, the first homodyne optical fiber communication system was demonstrated in BTRL, in which the signal laser and the local laser were all 1.5 μm He Ne gas lasers, and the OPLL used was a balanced one. In 1989, L.G.Kazovsky demonstrated experimentally a homodyne receiver in Bellcore using two 1.3 μm Nd:YAG lasers as the signal laser and the local laser and also using a balanced OPLL. Because the linewidth of the normal semiconductor laser is too large and its frequency stability is much poorer, it is very difficult to construct a homodyne receiver with the semiconductor lasers. At the end of 1989, the first Dissertation completed Jul. 1992homodyne optical fiber communication system using two 1.5 μm external cavity semiconductor lasers as the signal laser and the local laser, respectively, was finished in AT&T Bell Lab by J. M. Kahn, in which the OPLL was also a balanced one. In China, the research of the homodyne optical fiber communication system was funded by the National Seventh Five Year Program and by the National Natural Science Foundation. The difficulties to construct a homodyne optical fiber communication system are listed as follows: (1) In homodyne communication systems, the signal laser′s frequency should be stable to avoid the penalty of the receiver′s BER and the crosstalk to other channels in a FDM system, and the local laser could be tuned widely and easily to cover all the signal lasers′ frequency domain. Both the signal laser and the local laser should be narrow in linewidth to decrease the influence of the laser′s phase noise on the BER of the receiver. (2) The modulation pattern used should be studied and chosen carefully because the requirements of different kinds of modulation on the laser, the receiver and the channel are different. (3) Since the construction of the linear OPLL (the balanced) and the nonlinear OPLL (the Costas OPLL, or the Decision Driven OPLL) are rather different, their requirements on the linewidths of the lasers are different too, we should study the theory and the construction of the OPLL carefully to select the suitable scheme to realize. (4) In a multichannel system (such as a FDM system), the influence of crosstalk between channels on the homodyne system should be researched carefully. The technology used to stabilize the channel interval should also be studied. In this thesis, the homodyne optical fiber communication system has been theoretically analyzed, the technical difficulties of constructing the system have been studied. Several kinds of external cavity semiconductor laser have been researched experimentally. Compared
