Flexible control of semiconductor laser with frequency tunable modulation transfer spectroscopy

We introduce a new method of simultaneously implementing frequency stabilization and frequency shift for semiconductor lasers. We name this method the frequency tunable modulation transfer spectroscopy （FTMTS）. To realize a stable output of 780 nm semiconductor laser, an FTMTS optical heterodyne frequency stabilization system is constructed. Before entering into the frequency stabilization system, the probe laser passes through an acousto-optical modulator （AOM） twice in advance to achieve tunable frequency while keeping the light path stable. According to the experimental results, the frequency changes from 120 MHz to 190 MHz after the double-pass AOM, and the intensity of laser entering into the system is greatly changed, but there is almost no change in the error signal of the FTMTS spectrum. Using this signal to lock the laser frequency, we can ensure that the frequency of the laser changes with the amount of AOM shift. Therefore, the magneto-optical trap （MOT）-molasses process can be implemented smoothly.

Measurement of 3db Bandwidth of Laser Diode Chips

An accurate technique for measuring the frequency response of semiconductor laser diode chips is proposed and experimentally demonstrated.The effects of test jig parasites can be completely removed in the measurement by a new calibration method.In theory,the measuring range of the measurement system is only determined by the measuring range of the instruments network analyzer and photo detector.Diodes' bandwidth of 7 5GHz and 10GHz is measured.The results reveal that the method is feasible and comparing with other method,it is more precise and easier to use.

Two-hertz-linewidth Nd:YAG lasers at 1064 nm stabilized to vertically mounted ultra-stable cavities

Two Nd：YAG lasers operating at 1064 nm are separately servo-locked to two vertically mounted ultra-stable cavities. The optical heterodyne beat between two cavity-stabilized lasers shows that the linewidth of each laser reaches 2 Hz and the average frequency drift reduces to less than 1 Hz/s.

Broad bandwidth interference filter-stabilized external cavity diode laser with narrow linewidth below 100kHz

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.

A New Kind of Self-Frequency-Stabilization 1.3μM Single Frequency Coherent Source with 10MW and a Spectrum Linewidth in the Order of Kilohertz

The design of 1.3μm He-Ne single frequency laser for optical fiber communication is in-troduced.The scheme for obtaining steady single-mode oscillation by raising gas pressureand the method of getting linear-polarization single frequency output by longitudinal Zeemaneffect are present.The relations of linewidth to some factors are discussed.

基于保偏布喇格光栅的窄线宽半导体激光器

为了研制面向量子精密测量应用的近红外波段光纤光栅外腔半导体激光器,采用独立设计的高偏振依赖增益芯片和双折射光纤布喇格光栅,通过法布里-珀罗等效谐振腔模型,系统分析了光栅反射率、外腔和芯片长度对激光线宽的影响。结果表明,所研制激光器实现了54.46 mW的输出功率、58.88 dB的边模抑制比和24.46 dB的偏振消光比,利用延迟自外差拍频方法测得的洛伦兹线宽低至2.69 kHz。此研究为独立设计制备分立器件的单频窄线宽外腔半导体激光器提供参考,有望应用于雷达成像、陀螺仪、磁力仪和原子钟等量子精密测量领域。

基于光谱增强技术实现对532 nm波长激光频率标定

碘稳频532 nm Nd:YAG激光器在复现长度单位“米(m)”、绝对重力测量、引力波探测、精密光谱学、长度计量等领域有着重要应用,对其进行频率测量和标定对于激光器的性能评价具有重要意义.本文采用自行研制的掺Er光纤光学频率梳作为光源,对其扩谱后的1μm波段进行光谱增强并结合倍频晶体将光学频率梳输出的1.5μm波段光脉冲扩展到532 nm波段.其中掺Er光纤光学频率梳输出功率20 mW,首先经过掺Er光纤放大器将功率提到370 mW,经过脉冲压缩后脉冲宽度为45.7 fs,此后经过高非线性光纤扩谱实现光谱覆盖至1μm,输出功率为180 mW.扩谱后的1μm波段激光经过掺Yb光纤放大器放大至601 mW,经过压缩后脉冲宽度为84.6 fs,压缩后功率为420 mW.采用MgO:PPLN晶体对压缩后激光进行倍频得到155 mW的532 nm激光,倍频效率为36%.利用该系统分别对碘稳频532 nm Nd:YAG激光器输出的基频光1064 nm和倍频光532 nm进行拍频,获得了优于40 dB信噪比的拍频信号,后续进行了超过10 h的连续测量,测量结果与国际推荐值保持一致.

窄线宽外腔半导体激光器研究进展

窄线宽外腔半导体激光器具有结构简单、可调谐、噪声低等优势,广泛应用于量子精密测量、光通信、激光雷达等领域。根据外腔选频器件的不同,本文主要介绍光栅型激光器、干涉滤光型激光器、波导型激光器和法拉第激光器四类外腔半导体激光器,分析各类激光器的基本结构与选频机制、介绍各自的优缺点以及国内外研究进展。其中,前三类激光器采用非量子器件进行频率选择,而法拉第激光器利用共振法拉第旋光效应选频,输出波长直接对应原子跃迁谱线,对激光二极管的电流与温度变化具有良好的鲁棒性。随后介绍外腔半导体激光器的应用情况,尤其是在精密测量领域中的典型应用。最后总结并展望窄线宽外腔半导体激光器的未来发展方向。

The developing condition analysis of semiconductor laser frequency stabilization technology

The frequency stability of free-running semiconductor lasers is influenced by several factors, such as driving current and external operating environment. The frequency stabilization of laser has become an international research hotspot in recent years. This paper reviews active frequency stabilization technologies of laser diodes and elaborates their principles. Based on differences of frequency discrimination curves, these active frequency stabilization technologies are classified into three major types, which are harmonic frequency stabilization,Pound-Drever-Hall(PDH) technology and curve subtraction frequency stabilization. Further, merits and demerits of each technology are compared from aspects of frequency stability and structure complexity. Finally, prospects of frequency stabilization technologies of semiconductor lasers are discussed in detail. Combining several of these methods are future trends, especially the combination of frequency stabilization of F–P cavity. And PID electronic control for optimizing the servo system is generally added in the methods mentioned above.

Narrow-linewidth single-polarization frequency-modulated Er-doped fiber ring laser

We demonstrate a 1550-nm narrow-linewidth fiber ring laser with stable single polarization by using single-mode Er-doped fiber as active fiber and saturable absorber. A polarization-maintaining circulator is used to acquire single-polarization laser light with the degree of polarization of 99.8%--99.9%. The linewidth measured using a delayed self-heterodyne method is less than 0.5 kHz. Frequency of the fiber laser can be modulated by driving the waveguide phase modulator with proper voltage. A Mach-Zehnder interferometer with the optical path difference between two arms of about 36 km is used to study the long-distance coherent detection of the fiber laser for frequency-modulated continuous-wave application.

基于超稳腔PDH锁频技术的852 nm超稳激光器

自上世纪80年代激光锁定技术发展以来,超稳激光器在光钟、引力波探测、腔量子电动力学、星地通讯等高精度光学量子时频计量领域发挥着重要作用。利用Pound-Drever-Hall(PDH)锁频技术,可以将自由运转激光器的频率锁定后获得极高频率稳定性的激光输出。这里,将852 nm波长激光锁定在超稳谐振腔的频率谐振点上,实现超稳频激光输出。试验中的超稳谐振腔品质因子达到1010,精细程度达到20万,输出激光的秒级频率稳定度达到5.2×10^(-15),线宽2.3 Hz。这一频率稳定度的连续激光器将为852 nm波长的钟激光器提供有力的技术支持,与Cs原子产生良好关联。

国产激光管在磁选态光检测铯原子钟中的应用研究

在科学仪器国产化背景下,为了改变磁选态-光检测型铯原子钟仍依赖进口激光管的现状,进行国产DFB-LD激光管在磁选态-光检测铯束管上的应用和外差法拍频测试,并分析其与国外TOPTICA Photonics DFB-LD激光管之间的差别。结果显示:国产激光管线宽为1.999 MHz±6 kHz,频率稳定度为1×10^(-11)@100 s,采用国产激光管可以在国产铯束管上实现标准型应用指标(1.45×10^(-12)@100 s),这为进一步提升国产激光管的性能提供了思路和借鉴。未来需要进一步压窄国产激光管线宽,以实现更高的小型铯束钟指标。

可调谐半导体激光器的高精密驱动电源与稳频设计

介绍了一种新型实用的半导体激光稳频系统,主要包括精密控温电路、精密控流电路和激光稳频电路。对电路原理进行了讨论,给出了具体的参考电路和测量结果。结果表明控温电路的控制精度达到1 mK,使得由于温度影响导致的频率漂移小于3.8 MHz,控流电路的控制精度为1μA,使得由于电流抖动引起的频率抖动小于1 MHz,控温、控流电路与稳频电路组成的半导体激光稳频系统能够很好地将频率稳定于原子跃迁线上。所设计的稳频系统精度高、调节方便,可用于激光精密长度测量、化学精密检测和激光冷却等。

外腔半导体激光器的设计与高次谐波稳频

首先讨论了半导体激光器外腔结构参量对激光连续可调范围影响的理论计算方法,给出了Littrow结构外腔半导体激光器调谐范围的计算结果。然后介绍了半导体激光器外腔结构参量的具体设计,利用该设计得到了出射激光线宽小于1MHz、连续可调谐范围可达3GHz的780nm波段外腔半导体激光器。接着讨论了利用腔外饱和吸收谱的三次谐波稳频方法对半导体激光器进行稳频,优化激光频率短期稳定度的方法。最后根据该优化方法设计出稳频系统对半导体激光器进行稳频,得到了稳定度达到10-12量级的半导体激光输出。

激光陀螺仪频率稳定度高精度测量系统的研制

以碘稳定激光器为频率标准,根据拍频检测的原理,建立了一套高精度的激光陀螺仪频率稳定度测量系统。经过实验验证,该系统实现了可用光功率仅为0.1μw量级的微弱激光陀螺仪频率稳定度的测量,测量精度达到了10-11量级。该系统的研制成功为深入开展激光陀螺仪的稳频研究奠定了基础。

高稳定度窄线宽激光器的研究

介绍了3种不同类型的高稳定度窄线宽激光器的研究进展。基于Littman结构和饱和吸收光谱稳频技术,研制了稳频外腔半导体激光器系统,输出波长为780.2nm,频率稳定度1MHz,不失锁时间大于12h。利用边带稳频技术将分布反馈(DFB)激光器的输出波长稳定在Cs原子的吸收谱线的边带处,引入数字信号处理器(DSP)全数字稳频控制技术,实现了自动找频和稳频,获得波长为852.3nm的稳频激光输出,24h内频率漂移为±2MHz。利用国产磷酸盐玻璃光纤作为增益介质,实现了一台高功率单纵模光纤激光器,制作的厘米级激光器实现了最大输出功率100mW,利用外部光反馈实现单偏振运转,测得输出线宽为2kHz,偏振消光比优于35dB。

以原子谱线作参考的半导体激光器的频率锁定

研究以原子谱线作参考的半导体激光器的频率锁定系统，在精密控制半导体激光器的工作温度和工作电流的基础上，利用８５Ｒｂ的Ｄ２线的一次微分信号对ＬＤ的频率进行锁定。锁定后ＬＤ的频率最大变化为１０ＭＨｚ／３ｈ，平均取样时间１０ｓ，用Ａｌａｎ方差估算ＬＤ频率稳定度为１０－９。

频率红移法用于激光二极管热阻测量

给出了“频率(波长)红移法”测量半导体激光二极管热阻Rth的原理:由于温度变化引起LD峰值波长的变化△λ,间接得到温度变化△T;由注入电功率和输出光功率间接得到热耗散功率。克服了以往测试方法复杂、投入高、效率低等不足,而且可以与LD其它参数测试结合,投入少,适合于LD规模化生产和产品研制改进。介绍了Rth测试系统硬件和软件的实现方法以及测试实例。

外腔半导体激光器阵列波长稳定的实验研究

自由运行的半导体激光器列阵输出激光谱线较宽、中心波长易漂移。为此，本文采用体全息光栅（VBG）构成外腔半导体激光器阵列（EcLD）系统，利用体光栅能够稳定波长、压窄线宽的特点，从而克服上述缺点。实验表明：采用了VBG外腔反馈后，在最好的情况下，LDA的输出光谱宽度从自由运行时的2．3nm压窄到了0．96nm；在测试的环境温度变化范围内（14～31℃），LDA的峰值波长稳定在体光栅布拉格波长808nm处，输出光的线宽雏持在1．14nm之下；并且，在测试的偏置电流变化范围内（7～13A）峰值波长和谱宽无明显变化。

半导体激光器的线宽压窄及频率连续调谐

我们利用共焦F-P腔光学弱反馈技术,实现了单模GaAlAs半导体激光器线宽压窄、频率锁定及连续调谐。其线宽从自由运转时的10MHz被压窄到45kHz,并可将频率锁定于共焦F-P腔。实验证明,在弱反馈情况下,激光器的频率连续调谐范围与共焦F-P腔的光强反馈量近似成正比,实现了在铷原子D2线附近1.2GHz的频率连续调谐。