半导体激光管位移传感器的模型建立及仿真分析

从激光应用系统稳态条件出发,建立了半导体激光管位移传感器系统的数学模型,其仿真结果与有关文献的实验结论相吻合,详细阐述了通过检测ＬＤ注入调制三角波相邻两周期对应点处信号的位相差而完成位移测量的原理。由理论分析提出了提高最大允许位移速度上限和减小测量非线性误差的措施,其结论对激光自混合干涉技术的应用具有重要指导意义     

External cavity diode laser as a stable-frequency light source for application in laser cooling of molecules

We demonstrate a scheme to use a Littman configuration external cavity diode laser(ECDL) as a stablefrequency light source to stabilize two cw single-mode Ti:sapphire lasers for laser cooling of magnesium fluoride molecules. An ECDL based on the Littman configuration is constructed and stabilized by a digital signal processor system. We stabilize the frequency of our ECDL to 0.77 MHz precision over 10 h and the Allan standard deviation reaches 2.6 × 10-11 at an integration time of 10 s. We lock two Ti:sapphire lasers through a transfer cavity, and either laser has a long-term frequency stability of 2.5 MHz.     

Dynamics of erbium-doped fibre laser with optical delay feedback and chaotic synchronization

The dynamical behaviour of the erbium-doped fibre single-ring laser with an optical delay feedback is discussed. Simulation shows that as the delay rate increases, the lasing light displays period-doubling which leads to chaos and via reverse period-doubling route returns from chaos to periodic. At a particular delay rate the intermittently chaotic route to chaos is also observed. The identical synchronization based on chaos in this ring laser is demonstrated by numerical simulation.     

Stability of a diode laser with phase-conjugate feedback

An exact analysis is presented of the steady-state stability of a semiconductor laser subjected to feedback from a phase-conjugate mirror. Reduced stability occurs at low feedback whenever the effective external delay time is an integer multiple of the relaxation oscillation period. The role of a finite response time of the mirror is to enhance drastically the steady-state stability.     

Study on a broad-area laser diode with external cavity feedback

The external cavity feedback of a broad-area laser diode is investigated. In Fourier optic methods, the inserted prism in an external cavity can be interpreted as a spatial filter in the Fourier plane of the laser diode. The transverse mode can be selected by changing the position of the filter. As the result of a self-consistency theoretical analysis, the output beam of the external cavity has a single-lobed far-field profile. It agrees well with the experiment result. The beam times-diffraction-limit-factor M² is measured to be 1.16.     

Development of multi-wavelength microsphere fibre laser system for potential sensor applications

A multi-wavelength microsphere laser system, using a chirped fibre Bragg grating and a microsphere resonator as wavelength-selective elements and a high dopant erbium doped fibre as the gain material, has been successfully demonstrated. The multi-wavelength generation of the laser system arises from both the microsphere whispering gallery mode selection and from the additional Raman scattering inside the microsphere cavity when the erbium laser is operating at resonance with the whispering gallery modes. Through an appropriate design and fabrication of a microsphere and of a fibre taper, a selective multi-wavelength fibre laser has been realized when the pump power is above threshold required. The laser output lines created have shown much narrower linewidths than those from conventional fibre lasers and these characteristics are particularly suitable for the range of sensor applications envisaged in the work.     

二维复用半导体激光器线性调频光纤位移传感器的研究

利用半导体激光器线性调频外差干涉原理和频域多路复用原理,研究了光纤位移传感器多路复用技术,制作了两路复用光纤位移传感器,研究和解决了多路复用时信号串话问题.实验证明,各路之间串话引起的误差小于±0.02μm,每路测量误差小于±0.05μm.     

Controllable optical delay line using a Brillouin optical fiber ring laser

A controllable optical delay line using a Brillouin optical fiber ring laser is demonstrated and a large timedelay is obtained by cascading two optical fiber segments. In experiment, a single-mode Brillouin opticalfiber ring laser is used to provide Stokes wave as probe wave. We achieve a maximum tunable time delayof 61 ns using two cascading optical fiber segments, about 1.5 times of the input probe pulse width of 40ns. In the meantime, a considerable pulse broadening is observed, which agrees well with the theoreticalprediction based on linear theory.     

Fiber optic intensity sensor referenced with a virtual delay line

In this work a self-referencing fiber optic intensity sensor using virtual instrumentation is presented. To ensure higher flexibility and dynamic optimization, the use of an optical fiber delay line or an electrical delay line is avoided by implementing a delay line in the virtual domain, preserving the self-referencing and sensitivity characteristics of the proposed optical intensity sensing structure. Results are presented where displacement is measured with an 18 μm resolution demonstrating the concept feasibility.     

Distributed fiber temperature sensor using a laser diode modulated by a pseudo-random bit sequence

We propose and demonstrate a scheme to measure the distribution of temperature along an optical fiber based on pseudo-random sequence modulation. In our experimental work, current modulation with a pseudo-random bit sequence(PRBS) is applied to a laser diode that serves as the Brillouin pump light and reference light. Because of the independence of the spatial resolution on the PRBS length, the measurement range can be extended while maintaining high spatial resolution using a long PRBS length. Temperature-induced changes in a Brillouin frequency shift of 250 m fiber sections are clearly observed with 54 cm spatial resolution by this method.     

Continuous wave,distributed feedback diode laser based sensor for trace-gas detection of ethane

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C₂H₆) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) based on a 2f wavelength modulation (WM) detection technique. TDLAS was performed with a 100 m optical path length astigmatic Herriott cell. For an interference free C₂H₆ absorption line located at 2976.8 cm⁻¹ a 1σ minimum detection limit of 240 pptv (part per trillion by volume) with a 1 second lock-in amplifier time constant was achieved. In addition, reliable and long-term sensor performance was obtained when operating the sensor in an absorption line locked mode.     

双光反馈半导体激光混沌系统中外腔延时反馈特征的抑制

在一个双光反馈半导体激光混沌系统中,固定其中一个反馈腔镜(固定腔M₁)的反馈延迟时间以及反馈强度,实验研究了另一个反馈腔镜(可变腔M₂)的反馈延迟时间以及反馈强度对系统混沌输出的延时反馈特征的影响.研究结果表明:在可变腔M₂与固定腔M₁的反馈强度相等的条件下,改变M₂的腔长,当其腔长约等于(但不能严格等于)M₁的腔长或者腔长的一半时,系统将呈现较好地抑制延时反馈特征效果;当M 关键词： 半导体激光器 双光反馈 混沌输出 延时特征     

Fiber laser using a microsphere resonator as a feedback element

We show that a glass microsphere resonator can be used as a wavelength-selective mirror in fiber lasers. Due to their high quality factor (Q approximately 10(8)), microsphere resonators possess a narrow reflection bandwidth. This feature enables construction of single-frequency fiber lasers even when the laser cavity is long. Nonlinear effects (such as stimulated Raman lasing) were also observed in our setup at relatively low pump powers.     

Development of a fast temperature sensor for combustion gases using a single tunable diode laser

The 12 best NIR water transition line pairs for temperature measurements with a single DFB laser in flames are determined by systematic analysis of the HITRAN simulation of the water spectra in the 1–2 μm spectral region. A specific line pair near 1.4 μm was targeted for non-intrusive measurements of gas temperature in combustion systems using a scanned-wavelength technique with wavelength modulation and 2f detection. This sensor uses a single diode laser (distributed-feedback), operating near 1.4 μm and is wavelength scanned over a pair of H₂O absorption transitions (7154.354 cm^-1 & 7153.748 cm^-1) at a 2 kHz repetition rate. The wavelength is modulated (f=500 kHz) with modulation amplitude a=0.056 cm^-1. Gas temperature is inferred from the ratio of the second harmonic signals of the two selected H₂O transitions. The fiber-coupled-single-laser design makes the system compact, rugged, low cost and simple to assemble. As part of the sensor development effort, design rules were applied to optimize the line selection, and fundamental spectroscopic parameters of the selected transitions were determined via laboratory measurements including the temperature-dependent line strength, self-broadening coefficients, and air-broadening coefficients. The new sensor design includes considerations of hardware and software to enable fast data acquisition and analysis; a temperature readout rate of 2 kHz was demonstrated for measurements in a laboratory flame at atmospheric pressure. The combination of scanned-wavelength and wavelength-modulation minimizes interference from emission and beam steering, resulting in a robust temperature sensor that is promising for combustion control applications.PACS 42.62.Fi; 42.55.Px; 42.60.Fc; 39.30+w     

A fiber bragg grating acceleration sensor interrogated by a DFB laser diode

A fiber Bragg grating (FBG) acceleration sensor interrogated by a DFB laser diode is demonstrated; the sensor is fabricated by packaging a FBG on to a cantilever; the interrogation scheme takes advantage of the intensity modulation of the narrow spectral bandwidth light of a distributed feedback laser diode, when the reflection spectrum curve of a FBG moves due to the strain which is applied on the sensor. The sensor’s response to the frequency and acceleration is measured by the experiment, and the factors which have an impact on the sensor’s sensitivity are also discussed.     

A new approach to asymmetric feedback in a segmented broad area diode laser

We present the demonstration of a non-critical setup for asymmetric feedback in a segmented broad area diode laser. We compare the dependence of the beam quality on the position of the dispersive element for standard spectral beam combining and our new non-critical setup. We find that our new approach is significantly less critical to the position of the dispersive element. It is shown that we can displace the dispersive element by at least 50% of the focal length of the collimating lens away from the Fourier plane without compromising performance. Furthermore, our approach provides the same high beam quality as is possible using off-axis spectral beam combining. This provides the possibility of achieving a high beam quality in a more compact setup than previously possible.     

Fluorescence feedback control of a diode pumped solid state laser

We implement active feedback control in a Q-switched diode-pumped Nd:YVO₄ laser by monitoring the fluorescence intensity from the laser crystal. When the initial inversion level indicated by the detected fluorescence has reached a predetermined value, Q-switching is initiated. The Q-switched pulse energy is stabler with our feedback scheme based on the fluorescence intensity than that with the conventional Q-switching when pumping source is not stable.     

Coherent beam combination of broad-area laser diode array using off-axis external cavity with double feedback

In this letter, we demonstrate coherent beam combination of laser diode array using the external Talbot cavity with double feedback. The double feedback elements consist of grating and high-reflection plane mirror. Compared with single high-reflection plane mirror feedback, the external Talbot cavity with double feedback reduce the number of interference strips in the far-field pattern and narrow spectral line-width of the laser diode array. The results indicate that the application of the external Talbot cavity with double feedback produces a clear far-field interference pattern. In addition, line-width is reduced to 0.15 nm full-width at half-maximum (FWHM).