半导体激光器调制驱动电源的研制与实践

目的 为半导体激光器合成外差干涉研制一调制驱动电源。方法 选用现有大规模集成芯片，设计力求简单、实用、成本低及高性能。结果 利用数码调制驱动芯片线性区实现各种方式的调频是可行的。结论 该调制驱动电源满足各种波形的合成外差干涉，具有广泛的应用价值。     

激光干涉仪与纳米精度检测

文章对光外差、移相、正弦相位调制等几种常见的纳米精度干涉测量技术进行了综述 ,并介绍了上海光机所的相关工作 .     

基于锁相环的解调技术研究

介绍了调相信号的锁相解调技术基本原理以及利用集成锁相环NE564实现对信号的锁相解调。为了解调出不失真的波形,利用集成锁相环NE564和LM725CN芯片设计PM调制解调系统,可以直接实现信号的调制解调功能,利用相位能稳定跟踪的特点避免了频率失锁的缺陷,提高了测量精度。该系统具有操作简单、稳定性强的优点,并在激光外差干涉信号的解调中具有较强的实用性。     

高加速度超精密激光外差干涉测量模型

为了精确地描述激光外差干涉在高加速度超精密测量中加速度对位移测量精度的影响机理与规律,建立了高加速度超精密激光外差干涉位移测量模型.通过分析测量棱镜三维运动对多普勒频移的影响,推导出高加速度激光外差干涉位移测量模型.理论分析和仿真实验表明,当测量加速度为9m/s2,匀加速运行的位移为500mm时,由于加速度变化引起的相对论性效应对测量精度的影响为5nm.高加速度超精密激光外差干涉位移测量模型的建立,可提高激光外差干涉在高加速度超精密测量中的测量精度,为激光外差干涉在高速和超高速测量领域的应用提供了理论依据.     

空间外差光谱技术仿真研究

针对空间外差光谱技术(SHS)仿真研究,本文介绍了不同特征光谱光源的仿真计算.根据空间外差光谱仪的基本原理和系统结构特点,以及SHS系统参数与光谱干涉的调制关系,分别对单色光谱、连续光谱进行了理论仿真探讨,并且分析了不同带宽和采样间隔对仿真结果的影响.此外,采用空间外差光谱仪实验台装置获取实测数据,并与仿真结果进行对比分析.实验结果表明理论仿真数据和实测数据能够很好的吻合,能够为实际工作提供有益的参考,同时为SHS系统的设计和改造提供必要的依据.     

一种线性保护输入的恒压LED驱动电源设计

采用对母线电压进行反馈调节的恒压控制方式,设计研究了一种新型高压(260AC)线性保护输入LED驱动电路.利用LD7591GS芯片控制的脉冲宽度调制(PWM)电路和外围光耦电压反馈电路以及LNK564芯片控制的线性隔离变换电路,通过对驱动电路拓扑结构进行研究设计,并对变压器参数进行优化,实现了电压反馈的线性保护输入LED驱动电源设计.实验结果表明,采用外围电压反馈方式电路和线性隔离保护电路调整的LED驱动电源电路具有较好的安全稳定特性和低纹波PWM输出波形,并具有高转化效率,良好的抗电磁干扰性能和稳定的恒压功能.     

斜波调频合成外差干涉相位检测非线性分析

目的　分析半导体激光器斜波调频合成外差干涉拍频频率变化对干涉相位的影响 .方法　从频域用计算机进行理论上的仿真 .结果　拍频频率偏离斜波调制电流频率整数倍时 ,会产生随干涉相位输出以π为周期呈正弦变化的非线性误差 .结论　根据拍频频率的变化 ,动态调节调制电流幅度可消除该非线性误差     

用于绝对距离测量的0．6328μm氦－氖激光外差干涉仪

提出了一种用于绝对距离测量的新型外差干涉仪，它采用０．６３２８μｍ双模氦－氖激光器，光外差干涉和电信号混频、比相技术，直接测量合成波小数级次。此法避免了该领域常用的外差干涉仪的不足和拍波干涉仪结构复杂的问题，而且测量精度高、抗干扰能力强、测量时间短，使绝对距离测量技术更具有实用性。     

偏振分光镜旋转角度误差的确定

偏振分光镜存在旋转角度误差是引起激光外差干涉非线性误差的来源之一.提出了一种确定激光外差干涉偏振分光镜旋转角度误差的方法.通过分析偏振分光镜旋转角度误差在其它条件下对激光外差干涉非线性误差的影响,得出偏振分光镜存在的旋转角度误差将极大地增加非线性误差的一次谐波,但改变二次谐波很小.对光电接收器输出信号进行频谱分析,分离出激光外差干涉非线性误差的一次谐波和二次谐波,通过测量非线性误差二次谐波相对测量信号的大小,通过应用非线性误差二次谐波幅度比值与偏振分光镜旋转角度误差之间的模型,确定偏振分光镜旋转角度误差.实验结果表明,应用该方法能够得到偏振分光镜的旋转角度误差,从而为调整偏振分光镜提供了实验依据.     

基于LMS算法的移相干涉仪环境振动控制器

环境振动严重影响移相干涉测量的过程。在运用光学外差法测得移相干涉仪环境振动信号的前提下,设计了采用高速DSP芯片的振动控制器,它对电压形式的振动信号进行采样,用自适应LMS算法分析振动信号,同时输出反馈控制信号。反馈控制信号驱动PZT光学移相器对振动引起的光程差(或波前相位)变化进行实时补偿。通过这种闭环控制,系统能够对幅频积小于100waves*Hz的环境振动进行有效补偿,实验中获得了稳定的移相干涉条纹,保证了光学测试的正确性。     

Heterodyne wavelength meter for continuous-wave lasers

A wavelength meter based on a heterodyne interferometer is presented. A single-wavelength test laser beam is modulated to two orthogonal linearly polarized components with different frequencies by a pair of acousto-optic modulators. Then the modulated laser beam and a two-wavelength laser beam are sent to a heterodyne interferometer in a common path. The ratio of two laser interference phase shifts in the heterodyne interferometer is equal to the ratio of their wavelengths. The heterodyne technique measures the heterodyne interference phase but not the interference intensity, which means that it could measure a light source whose intensity is not stable. The heterodyne interference signal is an alternating signal that can easily magnify and process the circuit that makes up the heterodyne wavelength meter and could be used to measure the low-intensity light source even when there are environmental disturbances. A tunable diode laser wavelength range of 630-637 nm has been measured to an accuracy of 5 parts in 10(7).     

Frequency-shifted optical feedback in a pumping laser diode dynamically amplified by a microchip laser

Compared with conventional optical heterodyne detection, laser optical feedback imaging (LOFI) allows for a several orders of magnitude higher intensity modulation contrast. The maximum contrast amplification is typically 10(3) for a diode laser in the gigahertz range and 10(6) for a microchip laser in the megahertz range. To take advantage of the wavelength tunability of a laser diode and of the lower resonant detection frequency of a microchip laser, we used LOFI modulation induced by the frequency-shifted optical feedback in a laser diode as a modulated pumping power for a microchip laser for resonant dynamic amplification. In this way, we were able to transfer the optical feedback sensitivity of the laser diode to the megahertz range. Application to telemetry is also reported.     

Absolute interferometric distance measurement using a FM-demodulation technique

We propose an interferometric method for measuring absolute distances larger than the wavelength. A laser diode is used as a light source. The principle of operation is based on multiple-wavelength interferometry that uses a modulated light source. This method uses the fact that the wavelength of light emitted by the laser diode can be varied by means of the injection current. The modulation of the injection current in combination with the optical heterodyne technique causes a high-frequency phase-modulated detector signal. The phase deviation of the signal is a measure of the optical path difference in the interferometer. By FM demodulation of the detector output with a phase-locked loop demodulator, the optical path difference can be determined directly without the classical ambiguity problem of interferometry. The measuring range in the experiments was limited to 50 mm by the maximum travel range of the used specimen translation stage. Because of the inherent light sensitivity of the method described, the rangefinder can be used for three-dimensional profile measurements on a wide variety of objects, even on diffuse scattering surfaces.     

High-sensitivity mid-infrared heterodyne spectrometer with a tunable diode laser as a local oscillator

A new mid-IR heterodyne spectrometer, which is intended to be applied for atmospheric and astrophysical studies, is presented. The spectrometer uses a frequency-stabilized tunable diode laser as a local oscillator. Owing to the low output power of available single-mode diode lasers, a newly developed confocal-ring resonator, the diplexer, is used to superimpose the source signal efficiently with that of the local oscillator. Additionally, the diplexer serves as an optical filter that establishes controlled optical feedback between the laser diode and the detector, which allows stable laser operation with linewidths of the order of 1 MHz. The heterodyne signal from the HgCdTe detector is analyzed by means of a 1.4-GHz acousto-optical spectrometer. With this setup we find system temperatures as low as 4400 K (double sideband), that is, approximately a factor of 6 of the quantum limit.     

Extending the continuous tuning range of an external-cavity diode laser

The continuous tuning range of an external-cavity diode laser can be extended by making small corrections to the external-cavity length through an electronic feedback loop so that the cavity resonance condition is maintained as the laser wavelength is tuned. By maintaining the cavity resonance condition as the laser is tuned, the mode hops that typically limit the continuous tuning range of the external-cavity diode laser are eliminated. We present the design of a simple external-cavity diode laser based on the Littman-Metcalf external-cavity configuration that has a measured continuous tuning range of 1 GHz without an electronic feedback loop. To include the electronic feedback loop, a small sinusoidal signal is added to the drive current of the laser diode creating a small oscillation of the laser power. By comparing the phase of the modulated optical power with the phase of the sinusoidal drive signal using a lock-in amplifier, an error signal is created and used in an electronic feedback loop to control the external-cavity length. With electronic feedback, we find that the continuous tuning range can be extended to over 65 GHz. This occurs because the electronic feedback maintains the cavity resonance condition as the laser is tuned. An experimental demonstration of this extended tuning range is presented in which the external-cavity diode laser is tuned through an absorption feature of diatomic oxygen near 760 nm.     

Design and stability analysis of a CMOS feedback laser driver

A feedback laser driver circuit has been developed to control the average optical output power of a double heterostructure CW laser diode and also to operate with a wideband amplitude modulation. The average light power monitoring is realized by measuring the photoelectric current of a photodiode integrated inside the package of the laser diode. Safety features, including transient signal suppression, protect the laser against excessive light power. To obtain responses that are not out of the absolute maximum ratings of the laser diode light power, a study of the feedback loop stability is necessary. Two transconductance structures, using inverting and noninverting circuits are compared using the dominant pole compensation method. Then, the more stable driver circuit is analyzed and integrated using CMOS technology.     

Theory of digital modulation of semiconductor laser diode remotely

The authors present a new theory that can be applied to modulate the semiconductor laser diode (LD) remotely. The proposed scheme utilizes the effect of incoherent external optical feedback (EOF) on the LD output optical signal. In particular, owing to the high increase in threshold carrier density, the LD will be impelled to turn off when the value of external reflectivity is equal to the laser back reflectivity. Thus, by exposing the LD, which is injected with a dc-current higher than threshold, to incoherent EOF digital signal (which conveys the transmitted information), the output optical signal of LD can be modulated accordingly.     

Absolute distance measurement with an optical feedback interferometer

An important use of the self-mixing effect inside a frequency-modulated single-mode laser diode is in laser velocimetry and range-finding applications. The optical beam reflected by a target and injected into the laser diode cavity modulated by a reshaped current is mixed with the light inside the cavity, causing variations of the optical output power. A theoretical analysis of this effect is proposed, based on the determination of the beat frequencies of the optical power variations, to improve the accuracy of laser distance measurement. A resolution of ?1.5 mm from 50 cm to 2 m is obtained when thermal effects are taken into account.     

Fluid velocity measurements in a microchannel performed with two new optical heterodyne microscopes

Two laser Doppler microscopes (LDMs) based on an optical heterodyne interferometer have been developed for measuring fluid velocity in a microchannel. One of LDMs receives light from a Zeeman laser, and one easily obtains the standard heterodyne signal because a polarizer is set in front of a photomultiplier tube. The other LDM, with light from a He-Ne laser, employs a diffractive grating as a frequency shifter that is modulated in a sinusoidal movement by a piezoelectric transducer stack. By this modulation the nonstandard heterodyne signal is further processed by a new synthetic heterodyne algorithm. Finally, the phase shift related to the fluid velocity in both LDMs is demodulated by digital postprocessing in fast-Fourier-transform, bandpass filtering, inverse-fast-Fourier-transform, and arctangent algorithms.